Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • 1995-1999  (16,611)
  • 1965-1969  (8,340)
  • Polymer and Materials Science  (23,213)
  • Engineering General  (1,455)
  • Bone
  • Cat
Source
Material
Years
Year
Keywords
  • 1
    Electronic Resource
    Electronic Resource
    Density predicts the activity-dependent failure load of proximal femora with defects (1999)
    Springer
    Skeletal radiology 28 (1999), S. 90-95 
    Details
    ISSN: 1432-2161
    Keywords: Key words DXA ; Bone ; Cadaver ; Biomechanics ; Metastases ; Fracture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Objective. To determine whether the load-bearing capacity of human proximal femora with metastatic defects can be predicted from the bone mineral content. Design. The bone mineral content (BMC) of the total proximal femur was measured by dual-energy X-ray absorptiometry (DXA). The femurs were loaded so as to simulate stair ascent or external rotation. Patients. Simulated lytic defects were created using specialized cutting tools in the intertrochanteric region of 32 human cadaveric femora. Bone density measurements were made before and after creating defects. Results. A linear relation could be used to predict failure load from BMC or bone mineral density. The slope of the linear relation was greater for loads representing external rotation than for loads representing stair ascent. The linear relations suggest that the BMC measurements account for both the density of the host bone and the amount of bone removed by the defect. Conclusions. The data suggest that between 70% and 80% of the variation in failure load of human femora with lytic metastatic defects can be predicted from the BMC and that relations between BMC and failure load are sensitive to the type of loading. Combined with information on the loads associated with the activities of daily living, these data may be used to help identify patients in whom prophylactic stabilization might prevent a pathologic fracture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002560050480
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Advanced glycation endproduct-specific receptors in rat and mouse osteoblast-like cells: regulation with stages of differentiation (1999)
    Springer
    Acta diabetologica 36 (1999), S. 45-52 
    Details
    ISSN: 1432-5233
    Keywords: Key words Non-enzymatic glycosylation ; Advanced glycation endproducts ; Receptor for advanced glycation endproducts ; Diabetes mellitus ; Osteoblasts ; Bone ; Osteopenia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Advanced glycation endproducts have been implicated in the development of diabetic complications. In addition, these products could also mediate certain bone alterations such as diabetic osteopenia. Several receptors specific for advanced glycation endproduct-modified proteins have been characterized in different cell types, contributing to the recognition and degradation of senescent proteins. In the present report, we investigated the possible presence of advanced glycation endproduct-binding proteins on osteoblast-like cells. Both UMR106 and MC3T3E1 cell lines express specific advanced glycation endproduct-binding sites, with an affinity constant between 0.4 and 1.7 · 106 M−1, depending on the stage of osteoblastic differentiation; and with a receptor capacity of 1.5–2.0 · 107 sites/cell. Osteoblast-like cells were also found to participate both in the uptake and degradation of advanced glycation endproduct-modified bovine serum albumin at 37°C. Radiolabelled ligand blotting studies confirmed the presence of several membrane binding proteins, with apparent molecular masses of 50, 45–40, 30, 25 and 18 kDa; the major bands corresponded to 30 and 25 kDa proteins. This study provides evidence of the presence of advanced glycation endproduct-specific binding sites, and for their regulation with the stage of differentiation, in two osteoblast-like cells in culture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005920050144
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Saccades and multisaccadic gaze shifts are gated by different pontine omnipause neurons in head-fixed cats (1999)
    Springer
    Experimental brain research 125 (1999), S. 287-301 
    Details
    ISSN: 1432-1106
    Keywords: Key words Omnipause neurons ; OPN ; Saccade ; Gaze shift ; Tracking ; Perisaccadic drifts ; Moving target ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Pontine omnipause neurons (OPNs) have so far been considered as forming a homogeneous group of neurons whose tonic firing stops during the duration of saccades, when the head is immobilized. In cats, they pause for the total duration of gaze shifts, when the head is free to move. In the present study, carried out on alert cats with fixed heads, we present observations made during self-initiated saccades and during tracking of a moving target which show that the OPN population is not homogeneous. Of the 76 OPNs we identified, 39 were found to have characteristics similar to those of previously described neurons, ”saccade” (S-) OPNs: (1) the durations of their pauses were significantly correlated with the durations of saccades; (2) the discharge ceased shortly before saccade onset and resumed before saccade end; (3) visual responses to target motion were excitatory; and (4) during tracking, S-OPNs interrupted the discharge for the duration of saccades and resumed firing during perisaccadic ”drifts”. However, the characteristics of 37 neurons (”complex” (C-) OPNs) were different: (1) the pause duration was not correlated with the duration of self-initiated saccades; (2) time lead of pause onsets relative to saccades was, on average, longer than in the group of S-OPNs, and firing resumed after the saccade end; (3) visual target motion suppressed tonic discharges; and (4) during tracking, firing was interrupted for the total duration of gaze shifts, including not only saccades but also perisaccadic ”drifts”. We conclude that cat OPNs can be subdivided into two main groups. The first comprises neurons whose firing patterns are compatible with gating individual saccades (”saccade” OPNs). The second group consists of ”complex” OPNs whose firing characteristics are appropriate to gate total gaze displacements rather than individual saccades. The function of these neurons may be to disinhibit pontobulbar circuits participating in the generation of saccade sequences and associated perisaccadic drifts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050685
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    The limited value of radionuclide imaging at symptomatic knee prosthesis (1999)
    Springer
    European journal of orthopaedic surgery & traumatology 9 (1999), S. 251-254 
    Details
    ISSN: 1432-1068
    Keywords: Bone ; Scintigraphy ; symptomatic ; Knee ; Arthroplasty ; Os ; Scintigraphie ; Genou ; Arthroplastie ; Symptomatique
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Résumé Objectif: Evaluation de la scintigraphie osseuse dans l'arthroplastie totale de genou douloureux. Lieu: Hôpital universitaire, Maastricht et Hôpital Maasland, Sittard. Projet: Investigation clinique retrospective. Méthode: Les dossiers cliniques de 27 patients ayant subi une scintigraphie de l'os, ont été étudiés afin d'analyser les plaintes et la façon de décider le diagnostic. Ces patients avaient des symptômes persistants après l'arthroplastie totale du genou. En plus ont été étudiées les radiographies conventionelles et les scanographies isotopes, sans connaître les dossiers cliniques. Sur la base de ces données nous avons évalué les cas dans lesquels la scanographie isotope du genou a contribué de façon décisive au traitement future. Résultats: La scanographie isotope ne contribue pas à la planification du traitement, si l'examen physique ou les radiographies conventionelles n'ont pas apporté de diagnostic clinique. Il s'agissait ici de 37 % des patients de cette série. Dans les cas où le diagnostic clinique était fait, la scanographie isotope a influencé la décision de diagnostic de 65 % des patients. Cependant, pour les autres patients avec diagnostic clinique (35 %), ce ne fut pas le cas. Conclusion : La répresentation radionucléide est de valeur limitée dans le diagnostic d'une arthroplastie symptomatique totale du genou. Elle peut supporter ou rejeter un diagnostic clinique mais entraînera rarement un changement de traitement, dans l'absence de constatations anormales pendant les examens physiques ou radiologiques.
    Notes: Summary Objective: Determination of the value of bone scanning in symptomatic total knee arthroplasties. Setting Academic Hospital Maastricht and Maasland Hospital Sittard. Design: Retrospective clinical investigation. Method: The clinical reports of 27 patients, who underwent a bone scintigraphic study, were investigated for complaints and analysis of diagnostic decision making. These patients had persistent symptoms after total knee arthroplasty. In addition, conventional radiographs and the isotope scans were studied without knowledge of the clinical records. Based on these data we evaluated in which cases isotope scanning of the knee had contributed decisively to the further treatment. Results: Isotope scanning did not contribute to the treatment planning if physical examination or conventional radiographs had not led to a clinical diagnosis. This comprised 37% of the patients in our series. If a clinical diagnosis was present, isotope scanning did influence decision making in 65% of the patients. However in the remaining patients with a clinical diagnosis (35%) this was not the case. Conclusion: Radionuclide imaging is of limited value in the diagnostic process of symptomatic total knee arthroplasty. It may support or reject a clinical diagnosis, but in the absence of abnormal findings at physical examinations or radiologic studies, it seldom will induce a change in treatment
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00573333
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Bone substitutes (1999)
    Springer
    European journal of orthopaedic surgery & traumatology 9 (1999), S. 161-165 
    Details
    ISSN: 1432-1068
    Keywords: Bone ; Bone substitutes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Biocompatible calcium phosphate ceramics has been used for several years in orthopeadic surgery. We have been using two new synthetic biphasic calcium phosphate ceramics (BCP) since September 1996 for bone defect filling in any orthopaedic or trauma operation where autograft use was not possible or even wanted. The first, Eurocer 400® has 300 to 500 micron wide macropores with a totally interconnected porosity. This salt seed like product can be used in bone defect filling, when solidity is not a major concern. The second, Eurocer 200® has not totally interconnected 200 micron large pores. Its main characteristic is a mechanical resistance up to 30 Mpa. We use it in any case of weight-bearing surgery. Different sizes and presentation forms are available and will be chosen according to the recipient site shape. We report one hundred and fifty cases with a six to thirty month follow-up. In one third of the patients hip revision surgery was addressed. Another third concerned recent trauma or sequelae cases,.whereas the last third involved cold orthopaedic procedures. General principles are the need of a living and non-infected site after thorough debridement if necessary. Osteocompatibility of calcium phosphate ceramic is confirmed by our results. We report no mechanical failure. In all cases X-rays show a progressive integration, with new bone formation. Our substitutes have been histologically studied in nine cases, four to fifteen months after implantation. New bone formation around and in the substitute is impressive. Indeed, their good mechanical properties without loss of biological quality is the most relevant feature of these BCPs, leading to a wider indication field; therefore we have now abandoned the use of any bony auto, allo or xenograft.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00542583
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Saccular and utricular inputs to sternocleidomastoid motoneurons of decerebrate cats (1999)
    Springer
    Experimental brain research 126 (1999), S. 410-416 
    Details
    ISSN: 1432-1106
    Keywords: Key words Vestibulocollic reflex ; Saccular nerve ; Utricular nerve ; Sternocleidomastoid motoneuron ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Connections from the otolithic organs to sternocleidomastoid (SCM) motoneurons were studied in 20 decerebrate cats. The electrical stimulation was selective for the saccular or the utricular nerves. Postsynaptic potentials were recorded from antidromically identified SCM motoneurons; these muscles participate mainly in neck rotation and flexion. Partial transections of the brainstem at the level of the obex were performed to identify the possible pathway from the otolithic organs to the SCM motoneurons. Saccular or utricular nerve stimulation mainly evoked inhibitory postsynaptic potentials (IPSPs) in the ipsilateral SCM motoneurons. Some of the sacculus-induced IPSPs were preceded by small-amplitude excitatory PSPs (EPSPs). The latencies of the PSPs ranged from 1.8 to 3.1 ms after saccular nerve stimulation and from 1.7 to 2.8 ms after utricular nerve stimulation, indicating that most of the ipsilateral connections were disynaptic. In the contralateral SCM motoneurons, saccular nerve stimulation had no or faint effects, whereas utricular nerve stimulation evoked EPSPs in about two-thirds of neurons, and no visible PSPs in about one-third of neurons. The latencies of the EPSPs ranged from 1.5 to 2.0 ms, indicating the disynaptic connection. Thus, the results suggest a difference between the two otolithic innervating patterns of SCM motoneurons. After transection of the medial vestibulospinal tract (MVST), saccular nerve stimulation did not evoke IPSPs at all in ipsilateral SCM motoneurons, but some (11/40) neurons showed small-amplitude EPSPs. Most (24/33) of the utricular-activated IPSPs disappeared after transection, whereas the other 9 neurons still indicated IPSPs. In the contralateral SCM motoneurons, no utricular-activated EPSPs were recorded after transection. These MVST transection results suggest that most of the otolith-SCM pathways are located in the MVST at the obex level. However, the results also suggest the possibility that other otolith-SCM pathways exist at the obex level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050747
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    The dynamics of the vestibulo-ocular reflex after peripheral vestibular damage I. Frequency-dependent asymmetry (1999)
    Springer
    Experimental brain research 125 (1999), S. 353-364 
    Details
    ISSN: 1432-1106
    Keywords: Key words Vestibulo-ocular reflex ; Vertigo ; Labyrinthectomy ; Compensation ; Motor learning ; Oculomotor ; Plasticity ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Accurate performance by the vestibulo-ocular reflex (VOR) is necessary to stabilize visual fixation during head movements. VOR performance is severely affected by peripheral vestibular damage; after one horizontal semicircular canal is plugged, the horizontal VOR is asymmetric and its amplitude is reduced. The VOR recovers partially. We investigated the limits of recovery by measuring the VOR’s response to ipsilesional and contralesional rotation after unilateral peripheral damage in cats. We found that the VOR’s response to rotation at high frequencies remained asymmetric after recovery was complete. When the stimulus was a pulse of head velocity comprising a dynamic overshoot followed by a plateau, gain was partially restored and symmetry completely restored within 30 days after the plug, but only for the plateau response. The overshoot in eye velocity remained asymmetric. The asymmetry was independent of stimulus velocity throughout the known linear velocity range of primary vestibular afferents. Sinusoidal rotation at 0.05–8 Hz revealed that, within this range, the persistent asymmetry was significant only at frequencies above 2 Hz. Asymmetry was independent of the peak head acceleration over the range of 50–500°/s2. When both horizontal canals were plugged, a small residual VOR was observed, suggesting residual signal transduction by plugged semicircular canals. However, transduction by plugged canals could not explain the enhancement of the VOR gain, at high frequencies, for rotation away from the plugged side compared with rotation toward the plug. Also, the high-frequency asymmetry was present after recovery from a unilateral labyrinthectomy. These results suggest that high-frequency asymmetry after unilateral damage is not due to residual function in the plugged canal. The findings are discussed in the context of a bilateral model of the VOR that includes central filtering.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050691
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Receptive-field properties of adult cat’s retinal ganglion cells with regenerated axons (1999)
    Springer
    Experimental brain research 124 (1999), S. 383-390 
    Details
    ISSN: 1432-1106
    Keywords: Key words Retinal ganglion cells ; Axonal regeneration ; Single-unit activity ; Receptive field ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Receptive-field properties of retinal ganglion cells (RGCs) that had regenerated their axons were studied by recording single-unit activity from strands teased from peripheral nerve (PN) grafts apposed to the cut optic nerve in adult cats. Of the 286 visually responsive units recorded from PN grafts in 20 cats, 49.7% were classified, according to their receptive-field properties, as Y-cells, 39.5% as X-cells, 6.6% as W-cells, and 4.2% were unclassified. The predominant representation of Y-cells is consistent with a corresponding morphological study (Watanabe et al. 1993a), which identified α-cells as the RGC type with the largest proportion of regenerating axons. Among the X-cells, we only found ON-center types, whereas both ON-center and OFF-center Y-cells were found. As in intact retinas, the receptive-field center sizes of Y-cells and W-cells were larger than those of X-cells at corresponding displacements from the area centralis. Within the 10° surrounding the area centralis, the receptive fields of X-cells with regenerated axons were larger than those in intact retinas, suggesting that some rearrangement of retinal circuitry occurred as a consequence of degeneration and regeneration. Receptive-field center responses of Y-, X-, and W-type units with regenerated axons were similar to those found in intact retinas, but the level of spontaneous activity of Y- and X-type units was, in general, less than that of intact RGCs. Receptive-field surrounds were weak or not detected in more than half of the visually responsive RGCs with regenerated axons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050635
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Direct connection of the nucleus reticularis gigantocellularis neurons with neck motoneurons in cats (1999)
    Springer
    Experimental brain research 128 (1999), S. 527-530 
    Details
    ISSN: 1432-1106
    Keywords: Key words Nucleus reticularis gigantocellularis ; Reticulospinal neuron ; Neck motoneuron ; Single-neuron EPSP ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Functional connections of single reticulospinal neurons (RSNs) in the nucleus reticularis gigantocellularis (NRG) with ipsilateral dorsal neck motoneurons were examined with the spike-triggered averaging technique. Extracellular spikes of single NRG-RSNs activated antidromically from the C6, but not from the L1 segment (C-RSNs) were used as the trigger. These neurons were monosynaptically activated from the superior colliculus and the cerebral peduncle. Single-RSN PSPs were recorded in 43 dorsal neck motoneurons [biventer cervicis and complexus (BCC) and splenius (SPL)] for 21 NRG-RSNs and 135 motoneurons tested. All synaptic potentials were EPSPs, and most of their latencies, measured from the triggering spikes, were 0.8–1.5 ms, which is in a monosynaptic range. The amplitudes of single-RSN EPSPs were 10–360 µV. Spike-triggered averaging revealed single-RSN EPSPs in multiple motoneurons of the same species (SPL or BCC), their locations extending up to nearly 1 mm rostrocaudally. Synaptic connections of single RSNs with both SPL and BCC motoneurons were also found with some predominance for one of them. The results provide direct evidence that NRG-RSNs make monosynaptic excitatory connections with SPL and BCC motoneurons. It appears that some NRG-RSNs connect predominantly with SPL motoneurons and others with BCC motoneurons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050875
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Neuronal pathways from low-threshold hindlimb cutaneous afferents to motoneurons innervating trunk muscles in low-spinal cats (1999)
    Springer
    Experimental brain research 128 (1999), S. 543-549 
    Details
    ISSN: 1432-1106
    Keywords: Key words Abdominal muscles ; Back muscles ; Motoneurons ; Cutaneous afferent ; Spinal cord ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Postsynaptic potentials (PSPs) evoked in motoneurons innervating the back and abdominal muscles in the lumbar part of the body by stimulating hindlimb cutaneous afferents were investigated in unanesthetized decerebate and spinal cats. Various types of PSP: pure excitatory postsynaptic potential (EPSP), pure inhibitory postsynaptic potential (IPSP), and mixed PSP (i.e., EPSP followed by IPSP, EPSP/IPSP; and IPSP followed by EPSP, IPSP/EPSP) were observed. The weak stimulation at 2 times threshold (2T) produced predominantly the EPSP, while at 5T the incidence of IPSP or EPSP followed by IPSP was increased. In about 20–50% of the various groups of motoneurons, PSPs evoked by ipsi- and contralateral nerves were qualitatively and quantitatively similar. For the other motoneurons, PSPs evoked by ipsi- and contralateral nerves were markedly different with respect to magnitude and/or polarity. These findings suggest that, within each motoneuron pool, some neurons act to increase stiffness of the trunk or to move vertically in response to an increased activity of cutaneous afferents, while the other motoneurons act to produce lateral bending of the trunk.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050879
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 11
    Electronic Resource
    Electronic Resource
    The neural substrate of the vestibulocollic reflex (1999)
    Springer
    Experimental brain research 129 (1999), S. 483-493 
    Details
    ISSN: 1432-1106
    Keywords: Key words Vestibulocollic reflex ; Short-latency pathways ; Vestibulospinal and reticulospinal pathways ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The purpose of this review is to assess the role of short-latency pathways in the vestibulocollic reflex (VCR). First the current knowledge about the disynaptic and trisynaptic pathways linking semicircular canal and otolith afferents with cat neck motoneurons is summarized. We then discuss whether these pathways are sufficient or necessary to produce the responses observed in neck muscles by natural vestibular stimulation and conclude that they are neither. Finally, alternate pathways are considered, most likely involving reticulospinal fibers, which are an important part of the neural substrate of the VCR.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050918
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 12
    Electronic Resource
    Electronic Resource
    Activity-dependent development of cortical axon terminations in the spinal cord and brain stem (1999)
    Springer
    Experimental brain research 125 (1999), S. 184-199 
    Details
    ISSN: 1432-1106
    Keywords: Key words Corticospinal tract ; Motor cortex ; Activity-dependent development ; Spinal cord ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Corticospinal (CS) axon terminations in several species are widespread early in development but are subsequently refined into a spatially more restricted distribution. We studied the role of neural activity in sensorimotor cortex in shaping postnatal development of CS terminations in cats. We continuously infused muscimol unilaterally into sensorimotor cortex to silence neurons during the postnatal CS refinement period (weeks 3–7). Using anterograde transport of WGA-HRP, we examined the laterality of terminations from the muscimol-infused (i.e., silenced) and active sides in the spinal cord, as well as in the cuneate nucleus and red nucleus. We found that CS terminations from the muscimol-infused cortex were very sparse and limited to the contralateral side, while those from the active cortex maintained an immature bilateral topography. Controls (saline infusion, noninfusion) had dense, predominantly contralateral, CS terminations. There was a substantial decrease in the spinal gray matter area occupied by terminations from the side receiving the blockade and a concomitant increase in the area occupied by ipsilateral terminations from the active cortex. Optical density measurements of HRP reaction product from the active cortex in muscimol-infused animals showed substantial increases over controls in the ratio of ipsilateral to contralateral CS terminations for all laminae examined (IV–V, VI, VII). Our findings suggest that ipsilateral dorsal horn terminations reflect new axon growth during the refinement period because they are not present there earlier in development. Those in the ventral horn are present earlier in development and thus could reflect maintenance of transient terminations. Increased ipsilateral terminations from active cortex were due to recrossing of CS axons in lamina X and not to an increase in labeled CS axons in the ipsilateral white matter. Examination of brain stem terminations suggested that, between postnatal weeks 3 and 7, development of corticocuneate terminations also is activity-dependent but that development of corticorubral terminations is not. Activity-dependent CS development is a plausible mechanism by which early motor experiences could shape the anatomical and functional organization of the motor systems during a critical postnatal period.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050673
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 13
    Electronic Resource
    Electronic Resource
    Ossifying intramuscular metastasis from colon cancer (1999)
    Springer
    Diseases of the colon & rectum 42 (1999), S. 1225-1227 
    Details
    ISSN: 1530-0358
    Keywords: Colon cancer ; Adenocarcinoma ; Intramuscular metastasis ; Bone ; Heterotopic ossification ; Soft tissue tumor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract PURPOSE: This report presents a patient who developed severe buttock pain because of an ossified intramuscular metastasis from a sigmoid colon cancer. METHODS: This is a case report and review of the literature for intramuscular metastasis from colon cancer. RESULTS: Computed tomography and magnetic resonance imaging showed a soft-tissue mass with heavy calcification. Histologically, mature compact bone was observed with adenocarcinoma cells dispersed among the bony trabeculae. CONCLUSION: When an intramuscular mass is seen, even if it contains extensive calcification, metastasis from colon cancer should be included in differential diagnosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02238580
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 14
    Electronic Resource
    Electronic Resource
    Recognition and significance of pulmonary bone embolism (1999)
    Springer
    International journal of legal medicine 112 (1999), S. 195-197 
    Details
    ISSN: 1437-1596
    Keywords: Key words Trauma ; Calcification ; Bone ; Embolism ; Autopsy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Law
    Notes: Abstract Embolism of bone marrow to the lungs is a quite frequent finding after trauma but transport and deposition of solid bone is rarely seen, which may simply be because pulmonary calcifications are not recognized as bone fragments. We report on three patients with embolism of bone spicules to small lung arteries of about 0.5 mm in diameter which were plentiful in two of the patients on postmortem examination. However, the true nature of the emboli was only recognizable after decalcification of lung tissues. It appears that trauma occurring in a septic bone lesion has the greatest chance to provoke bone embolism. The bone spicules do not usually occlude vessel lumina and thus do not severely disturb the blood circulation in the lungs. The bone fragments become covered by endothelium and can remain recognizable for months or even years.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004140050232
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 15
    Electronic Resource
    Electronic Resource
    Mikromorphologische Kieferveränderungen nach Bestrahlung (1999)
    Springer
    Mund-, Kiefer- und Gesichtschirurgie 3 (1999), S. 140-145 
    Details
    ISSN: 1434-3940
    Keywords: Schlüsselwörter Konfokale Laser-Scanning-Mikroskopie ; Dunkelfeldmikroskopie ; Bisbenzimidmarkierung ; Knochen ; Strahlenfolgen ; Radiogener Osteozytentod ; Key words Confocal laser scanning microscopy ; Microscopy ; Bisbenzimide labelling ; Bone ; Radiation effects ; Osteocytes ; Osteoradionecrosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Early radiation effects on human bone may lead to osteoradionecrosis (ORN). Direct bone cellular lesions [28] as well as fibrous degeneration of blood vessels [21] are considered to be pathologically relevant. Only few data on initial subclinical radiation effects are available. Patients were grouped according to the dose of radiation and clinical findings. Group 1: sound human bone of lower jaw, mostly collected during orthodontic surgery (n = 10 patients); group 2: specimens of lower jaw from patients with ORN (n = 12 patients); group 3: specimens of lower jaw from patients with head and neck cancer who were preoperatively treated with 36 Gy radiation; group 4: specimens of lower jaw from patients with head and neck cancer (n = 9) who were treated with 60–70 Gy radiation. Specimens were studied by confocal laser scanning microscopy (CLSM), by conventional light microscopy (DL) and by flourescence darkfield microscopy (DFM) after bisbenzimide staining (H 33258) of the viable cellular nuclei. For the correlating study of identical areas in CLSM and DL the specimens were prepared according to the sawing and grinding technique [8]. All the radiated bony specimens, regardless of the dose of radiation, showed areas of extensive or total loss of vitality of the osteocytes. This finding was also evident after 36 Gy and a short interval between radiation and sample collection (group 3). Additionally, in CLSM micromorphologic lesions of the lamellate structure were seen. With these results we can confirm the loss of vitality of the osteocytes as an initial radiation effect as described earlier [10, 23, 28]. In addition to these findings, alteration of the lamellate microstructure was found in the early phase after radiation. The functional and mechanical significance of these findings should be the subject of further studies.
    Notes: Für die infizierte Osteoradionekrose (IORN) des Kiefers werden unterschiedliche pathogenetische Mechanismen initialer Strahlenfolgen im Knochen diskutiert: Wichtige Parameter sind dabei die direkte Zellschädigung der Osteozyten [28] und die Gefäßfibrosierung [21]. Bislang liegen wenige Kenntnisse zum Ausmaß der initialen, subklinischen Veränderungen vor. 4 Probengruppen wurden anhand verschiedener Patientenkollektive definiert: Gruppe 1: gesunde Unterkieferproben meist von orthodontischen Operationen (n = 10 Patienten); Gruppe 2: Unterkieferproben mit manifester IORN (n = 12 Patienten); Grruppe 3: Unterkieferproben nach 36 Gy präoperativer Radio(chemo)therapie (n = 9 Patienten); Gruppe 4: Unterkieferproben nach 60–70 Gy Bestrahlung ohne Hinweise auf IORN (n = 9 Patienten). Alle Proben wurden histotomographisch mit konfokaler Laser-Scanning-Mikroskopie (CLSM), durchlichtmikroskopisch (DL) und dunkelfeldmikroskopisch (DFM) nach Fluoreszenzmarkierung des intakten Zellkerns (Bisbenzimid H 33258) untersucht. Korrelierende Histologien identischer Probenareale erfolgten an Trenndünnschliffen [8]. Als Ergebnisse wurden gefunden: 1. Alle unterschiedlich bestrahlte Knochenproben zeigten Areale mit weitgehendem bis vollständigem Verlust vitaler Osteozyten. Diese Strahlenfolge trat auch schon nach 36 Gy und kurzem Intervall bis zur Operation (Gruppe 3) auf. 2. Im CLSM zeigten sich zusätzlich mikromorphologische Veränderungen der lamellären Struktur, die zwischen den Probengruppen progredient waren. Hieraus können folgende Schlußfolgerungen gezogen werden: 1. Der vorbeschriebene Vitalitätsverlust der Osteozyten [10, 23, 28] konnte als sehr frühe, initiale, radiogene Läsion bestätigt werden. 2. Zusätzlich zeigten sich Veränderungen der lamellären Mikroarchitektur des Knochens als frühe und im Gruppenvergleich progrediente Strahlenläsion. Die mikromechanisch funktionelle Bedeutung dieser Veränderung muß in weiterführenden Untersuchungen eruiert werden.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100060050118
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 16
    Electronic Resource
    Electronic Resource
    Model for Intravital Microscopic Evaluation of the Effects of Arterial Occlusion-caused Ischemia in Bone (1999)
    Springer
    Annals of biomedical engineering 27 (1999), S. 508-516 
    Details
    ISSN: 1573-9686
    Keywords: Angiogenesis ; Artery ; Bone ; Creeping substitution ; Leukocytes ; Osteocytes ; Reperfusion injury ; Trauma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract An in vivo model has been developed for chronic observation of the effects of ischemia on cortical bone remodeling and perfused vascularity. Diaphragm occluders were implanted around the right common iliac artery of four rabbits and inflated to produce 10 h of ischemia to the limb. Microcirculation was monitored with intravital microscopy of injected fluorescent microspheres and FITC-Dextran 70 through a bone window, the tibial bone chamber implant (BCI). Bone resorption and apposition in the BCI were indicated with mineralization dyes. Between 2 and 12 h following release of the occluder, secondary ischemia/no-reflow and other evidence of reperfusion injury were observed. Vessel damage was suggested by abnormally high leakage of FITC-D70 from the few vessels perfused during secondary ischemia. In the weeks following occluder release perfused vasculature increased beyond pre-occlusion levels. Net bone resorption reached a maximum when vascularity passed normal levels. In order to further validate the arterial occlusion model for osteonecrosis, techniques for (1) confirming bone death and (2) detecting increased leukocyte adherence to endothelial cells were added. The dead cell stain Ethidium homodimer-1 was used to tag dead osteocytes immediately after occlusion and produced a measure designated “osteonecrosis index.” To detect leukocytes adhering to vessel walls, carboxyfluorescein diacetate, succinimidyl ester was injected at occluder release. An increase in the number of adherent leukocytes was detected. © 1999 Biomedical Engineering Society. PAC99: 8764Rr, 8717-d, 8719Tt
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1114/1.194
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 17
    Electronic Resource
    Electronic Resource
    Bone tunnel enlargement after anterior cruciate ligament reconstruction with the hamstring autograft and endobutton fixation technique A clinical, radiographic and magnetic resonance imaging study with 2 years follow-up (1999)
    Springer
    Knee surgery, sports traumatology, arthroscopy 7 (1999), S. 290-295 
    Details
    ISSN: 1433-7347
    Keywords: Key words Anterior cruciate ; ligament reconstruction ; Bone ; tunnel enlargement ; Hamstring ; tendons ; Magnetic resonance ; imaging ; Radiographic evaluation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Sports Science
    Notes: Abstract The aim of this study was to describe the contrast-enhanced magnetic resonance imaging (MRI) appearance of bone tunnel enlargement detected on radiography after anterior cruciate ligament (ACL) reconstruction with semitendinosus and gracilis tendon endobutton (STG-endobutton) fixation technique. Fourteen patients with a STG-endobutton ACL reconstruction were examined 3 months (n = 1), 1 year (n = 1) and 2 years (n = 12) postoperatively. An age- and sex-matched group with a bone–patellar tendon–bone (BTB) autograft ACL reconstruction with similar follow-up was taken as control. Data on clinical examination, laxity and isokinetic muscle torque measurements, anteroposterior and lateral view radiography were obtained, and knee scores (Lysholm and Tegner) were collected. Contrast-enhanced MRI was performed in the STG-endobutton group with a 1.5-T imager. There were no statistical differences between the groups with respect to clinical findings, stability tests, or knee scores. In the STG-endobutton group the average femoral and tibial bone tunnel diameter detected on anteroposterior view radiography had increased at 2-year follow-up by 33% and 23%, respectively. On MRI the ligamentous graft itself was not enhanced by the contrast medium whereas periligamentous tissue within and around the STG graft bundles showed mild contrast enhancement. In conclusion, the MRI results suggest that enhancing periligamentous tissue accumulated in and around the STG graft associated with the tunnel expansion. In spite of the significant bone tunnel enlargement observed on the follow-up radiography the STG-endobutton knees were stable and the patients satisfied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001670050166
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 18
    Electronic Resource
    Electronic Resource
    Die aneurysmatische knochenzyste am kleinfinger (1999)
    Springer
    European journal of trauma 25 (1999), S. 230-236 
    Details
    ISSN: 1615-3146
    Keywords: Aneurysmatische Knochenzyste ; Knochentumor ; Hand ; Aneurysmal bone cyst ; Bone ; Hand
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract The aneurysmal bone cyst localizised at the longfingers of the hand is an extremely rare clinical entity, particularly considering the age and the distinct aggressiveness in our case. In this specific case of a 53-year-old male the differentialdiagnosis as well as problems of the aneurysmal bone cyst with affection of the phalangeal bone will be discussed. Furthermore the various possibilities of therapy will be focussed on. At first the patient was treated with curettage followed by bone grafting. Already 5 months later a local recurrence appeared. The proximal phalangeal bone and the metacarpophalangeal joint V were almost distroyed. Aiming at preservation of a high funcionality of the hand we amputated the 5th finger in the metacarpophalangeal joint.
    Notes: Zusammenfassung Die aneurysmatische Knochenzyste mit Lokalisation an der Hand, insbesondere an den Phalangen, ist ein extrem seltenes Krankheitsbild. Auch das Alter des Patienten und die ausgeprägte Aggressivität unseres Falles sind bemerkenswert. Anhand der Krankengeschichte eines 53jährigen Mannes mit Befall der Grundphalanx des fünften Fingers der rechten Hand werden die Problemstellung bzw. Differentialdiagnose verdeutlicht und die verschiedenen Therapiemöglichkeiten besprochen. In unserem Fall wurde zunächst eine Kürettage mit anschließender Spongiosaaufftüllung durchgeführt. Bereits nach fünf Monaten kam es zu einem aggressiven Rezidiv mit Zerstörung der gesamten Grundphalanx und des Grundgelenks, so daß wir uns schließlich unter Berücksichtigung der bestmöglichen Funktion der Hand für eine Amputation des Kleinfingers entschieden haben.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00596732
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 19
    Electronic Resource
    Electronic Resource
    Repeated cat-associated peritonitis in a patient on automated nocturnal intermittent peritoneal dialysis (1999)
    Springer
    Clinical and experimental nephrology 3 (1999), S. 59-61 
    Details
    ISSN: 1437-7799
    Keywords: Key words Peritoneal dialysis ; Peritonitis ; Cat ; Pasteurella multocida
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A 49-year-old man had three episodes of bacterial peritonitis in the 8 months after he started nocturnal intermittent peritoneal dialysis (NIPD) at home, using an automated cycler device. When peritonitis was first diagnosed, Enterobacter agglomerance was cultured in his peritoneal fluid. In the second and third episodes, Pasteurella multocida and alpha-Streptococcus were isolated, respectively. These bacteria are unusual pathogens in continuous ambulatory peritoneal dialysis (CAPD) peritonitis. Detailed questioning revealed that a domestic cat had bitten the dialysis tube before the patient experienced the second episode of peritonitis. Pasteurella multocida is part of the normal oral flora in cats and dogs. We isolated Pasteurella multocida from the teeth of the patient's cat. Enterobacter agglomerance is part of the common bacterial flora in animal's alimentary tract, and alpha-Streptococcus is commonly found in animal's respiratory tracts. Since the patient removed the cat from his bedroom, he has had no peritonitis. NIPD is a very convenient sysytem for patients in the final stage of renal failure; however, patients must be aware of the risks associated with keeping pets in their homes. This case is the first report of cat-associated peritonitis in Japan.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s101570050011
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 20
    Electronic Resource
    Electronic Resource
    Estrogen research (1999)
    Springer
    Reproduktionsmedizin 15 (1999), S. 405-409 
    Details
    ISSN: 1434-808X
    Keywords: Schlüsselwörter Estrogenrezeptoren ; Knochen ; Arteriosklerose ; Endometrium ; Zentralnervensystem ; Key words Estrogen receptors ; Bone ; Arteriosclerosis ; Endometrium ; Central nervous system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Almost each cell in the body is estrogen-receptive. The strength of estrogen influence on organs or organ systems, however, may vary. Thus, estrogen withdrawal may have more or less severe pathophysiological consequences. Recently, the existence of two estrogen receptors has been established (estrogen receptor α and β = ERα and ERβ and several splice variants of these two basic receptor types have been desribed). This, together with our increasing knowledge about tissue-specific enhancer and repressor genes now allows a better understanding of the organ-specific effects of estrogens. In view of gynecological endocrinology, hormone replacement therapy with estrogens is beneficial for most organs in the body (bone, cardiovascular system, CNS). However, pure estrogen therapy may have deleterious effects in the endometrium of the uterus because it may initiate the development of uterine cancer. In the uterus of most species studied so far, no ERβ but only the classical ERα gene has been described. Hence, drug companies have now intensively begun to search for ERβ-specific estrogens. The first, relatively specific, non-steroidal product that addresses primarily the ERβ is the drug raloxifen, which has been recently introduced clinically. However, also some natural phyto-estrogens appear to be ERβ-specific.
    Notes: Zusammenfassung Fast jede Körperzelle ist estrogenrezeptiv. Es gibt allerdings Organe und Organsysteme, die besonders unter dem Einfluß von Estrogenen stehen und die sich bei Estrogenmangel krankhaft verändern können. Die vielfältigen Wirkungen von Estrogenen konnten nicht vollständig verstanden werden, solange die Existenz von nur einem Estrogenrezeptor quasi ein Dogma war. Erst die Klonierung eines zweiten (Estrogenrezeptor β = ERβ) sowie das bessere Verständnis von gewebespezifischen Enhancer- und Repressor-Genen konnten die vielfältigen und z. T. organspezifischen Wirkungen der Estrogene aufklären. Aus der Sicht der gynäkologischen Endokrinologie ist die Hormonersatztherapie mit Estrogenen für fast alle Organe des Körpers (Knochen, Herz-Kreislauf-System, Zentralnervensystem) segensreich. Eine nicht gestagenbegleitete Estrogentherapie kann allerdings verheerende Folgen am Endometrium mit Entwicklung eines Corpus-Karzinoms haben. Da der Uterus praktisch kein ERβ sondern nur den klassischen ERα exprimiert, hat eine intensive Suche nach ERβ-spezifischen Estrogenen begonnen. Ein erstes, halbwegs spezifisches nicht-steroidales Produkt scheint das kürzlich in die Klinik eingeführte Raloxifen zu sein, aber auch einige Phytoestrogene scheinen ERβ-spezifisch zu wirken.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004440050096
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 21
    Electronic Resource
    Electronic Resource
    Osseous hemangiopericytomas of unsuspected intracranial origin (1998)
    Springer
    Skeletal radiology 27 (1998), S. 98-102 
    Details
    ISSN: 1432-2161
    Keywords: Key words Hemangiopericytoma ; Brain ; Bone ; Metastasis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Two cases of osseous hemangiopericytoma are presented that were initially diagnosed as primary in origin, but later reclassified as metastases, after a history of resection for an intracranial tumor was discovered. An intracranial source should be excluded before an isolated osseous tumor is determined to be a primary hemangiopericytoma.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002560050345
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 22
    Electronic Resource
    Electronic Resource
    Intraosseous malignant peripheral nerve sheath tumor in a patient with neurofibromatosis (1998)
    Springer
    Skeletal radiology 27 (1998), S. 346-349 
    Details
    ISSN: 1432-2161
    Keywords: Key words Neurofibromatosis ; Malignant peripheral nerve sheath tumor ; Bone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Malignant peripheral nerve sheath tumors (MPNSTs) are uncommon sarcomas that almost always arise in soft tissue. They can develop in pre-existing neurofibromas or schwannomas, de novo from peripheral nerves, or following radiation therapy. Primary intraosseous MPNST is rare and has been reported most frequently in the mandible. Of the reported cases involving the long bones, none has been associated with neurofibromatosis type 1 (NF-1). We report a case of MPNST arising in the femur in a patient with NF-1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002560050395
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 23
    Electronic Resource
    Electronic Resource
    Humoral factor in children with neonatal Bartter syndrome reduces bone calcium uptake in vitro (1998)
    Springer
    Pediatric nephrology 12 (1998), S. 371-376 
    Details
    ISSN: 1432-198X
    Keywords: Key words: Neonatal Bartter syndrome ; Bone ; Cal- cium ; Heparin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. The neonatal Bartter syndrome (NBS) is associated with a complex disorder of mineral metabolism in children, including hypercalciuria, nephrocalcinosis, and diminished bone mineral density. Although cyclooxygenase inhibition usually brings about improvement in these findings, there is a variable component which is resistant to such therapy in many children. The factor mediating this disorder has not been identified. Blood and urine from 12 children with NBS were examined. When compared with samples from normal children and adults, all (NBS) sera reduced bone calcium uptake in a bone disc bioassay. This effect persisted in the presence of parathyroid hormone (PTH) antibody and PTH receptor blockade, indicating that neither PTH nor PTH related peptide was responsible. It was eliminated by indomethacin, suggesting that prostanoid generation was essential. Protamine was also inhibitory, as was the addition of ecteola, an anion binder. Activity could be recovered from ecteola by elution with hypertonic buffer. Urine samples from children with NBS had the same calcitropic effect. The agent was removed by ecteola and recovered by hypertonic elution. Activity was eliminated by protamine and by heparinase, but not by trypsin digestion. Size exclusion centrifugation showed that the activity was associated with a material between 10 and 30 kilodaltons. Finally, urine ecteola eluates from NBS patients raised serum concentrations of calcium after intraperitoneal injection in rats. These data suggest that children with NBS have a calcitropic substance in their serum and urine which is not found in normal individuals. The substance is heparin like, and mediates its effects through prostanoid production. These studies provide additional evidence against a direct renal cause of the urinary calcium disturbance characteristic of the disorder.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004670050468
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 24
    Electronic Resource
    Electronic Resource
    Visual zone of the claustrum shows localizational and organizational differences among rat, guinea pig, rabbit and cat (1998)
    Springer
    Anatomy and embryology 198 (1998), S. 63-72 
    Details
    ISSN: 1432-0568
    Keywords: Key words Claustrum ; Visual cortex ; Visual zones Comparative anatomy ; Rat ; Guinea pig ; Rabbit ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The retrograde axonal transport method was used to compare the topography and organization of the visual zone of the claustrum in rat, guinea pig, rabbit and cat. First, massive Fluoro-Gold injections were placed into the primary visual cortex and the secondary areas. Experiments showed differences in the location of the visual zone among the animals under study. In rat, the visual zone occupied the posteroventral part of the claustrum and spread to its anterior pole. In guinea pig, neurons projecting to the visual cortex were located dorsally in the posterior half of the claustrum. In rabbit, similarly to the rat, they were localized in the posteroventral part; however, they did not reach the anterior pole. In cat, neurons that project to the visual cortex were concentrated dorsally in the posterior fourth of the claustrum. In double-injection experiments, Fast Blue and Diamidino Yellow were placed into the primary and secondary visual areas in various combinations. The experiments showed that in the rat and the rabbit claustral neurons project to primary visual cortex (area 17) as well as to both secondary visual areas (areas 18a and b). Populations of neurons sending axons to the primary and secondary areas showed full overlap. The presence of double-labeled neurons indicates that some claustral neurons project both to the primary and secondary fields. In cat, neurons that project to the primary visual cortex appear to be clearly separated from those connected with the secondary visual area, as no double-labeled neurons were found. In all studied species, the double injections placed into the visual and primary somatosensory cortex did not result in any double-labeling neurons. Our results indicate that the location of the visual zone in the posterior part of the claustrum is a phylogenetically stable feature, whereas its dorsoventral shift as well as the extent toward the anterior pole is related to the particular species. The overlap of neurons projecting to the primary and secondary visual areas in the rat and rabbit as well as the separation of both projections in cat appear to reflect the higher degree of complexity of the visual system in the latter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004290050165
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 25
    Electronic Resource
    Electronic Resource
    Muscular dystrophy: Centronucleation may reflect a compensatory activation of defective myonuclei (1998)
    Springer
    Journal of biomedical science 5 (1998), S. 54-61 
    Details
    ISSN: 1423-0127
    Keywords: Muscular dystrophy ; Central nuclei ; Avian muscle ; Inflammation ; Dwarfism ; Lymphocyte ; Mechanochemical transducer ; Bone ; Steroid ; Fiber splitting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Muscular dystrophy has long been believed to be characterized by degeneration and abortive regeneration of muscle fibers (the muscle degeneration theory), but unfortunately its pathogenesis is still unclear and an effective treatment has yet to be developed. As a challenge to the theory, we have proposed an alternative muscle-defective-growth theory and a further bone muscle growth imbalance hypothesis supposing possible defects in bone-growth-dependent muscle growth based on our findings in hereditary dystrophic dy mice (C57BL/6Jdy/dy). This review presents some new insights into the pathogenesis of the disease along with our hypothesis, focusing on the physiological meaning of centronucleation, one of the major pathological changes commonly observed in dystrophic muscles of man and experimental animals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02253356
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 26
    Electronic Resource
    Electronic Resource
    Cystic angiomatosis of bone with massive osteolysis of the cervical spine (1998)
    Springer
    European spine journal 7 (1998), S. 257-259 
    Details
    ISSN: 1432-0932
    Keywords: Key words Angiomatosis ; Bone ; Osteolysis ; Cervical spine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The case of a 21/2-year-old boy with diffuse cystic angiomatosis of bone is presented. No evidence of visceral involvement was recorded. The clinical, radiographic and histologic findings during the course of the disease process are discussed. At the age of 15 years the patient died of neurologic alterations developed due to massive osteolysis and collapse of the cervical spine, and severe dyspnoea, secondary to persistent bilateral pleural effusions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005860050069
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 27
    Electronic Resource
    Electronic Resource
    Distribution of glutamate-, glycine- and GABA-immunoreactive nerve terminals on dendrites in the cat spinal motor nucleus (1998)
    Springer
    Experimental brain research 118 (1998), S. 517-532 
    Details
    ISSN: 1432-1106
    Keywords: Key words Ultrastructure ; Immunohistochemistry ; Bouton ; Synaptic input ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The dendritic tree constitutes more than 93% of the receptive membrane area of a spinal motoneuron, yet little is known about its synaptic inputs. In this study we examined the distribution of glutamate-, GABA- and glycine-like immunoreactivity in boutons apposing dendrites in the L7 spinal cord motor nucleus, by use of postembedding immunohistochemistry on serial sections. We examined 799 boutons apposing 401 cross-sectioned dendrites of different calibre (range 0.2–15 µm), and 14 first-order (stem) dendrites. Thirty-five percent (35%) of the boutons were immunopositive for glutamate and 59% for GABA and/or glycine. Among the latter, 30% showed glycine immunoreactivity only and 24% were immunoreactive for both GABA and glycine. Very few were immunoreactive only for GABA (5%). As few as 6% of the boutons were judged as not enriched for any amino acid analysed. The fine structural characteristics of the boutons were in accordance with previous descriptions. The sample of dendrites was arranged in calibre bins in order to facilitate distribution analysis. Stem dendrites differed from the other bins, with a high total bouton covering (61%) and a high bouton density. Sixty-nine percent of the membrane covering was by glycine- and/or GABA-immunoreactive boutons, whereas 18% was covered by boutons enriched in glutamate. For non-stem dendrites, bouton covering fell from 33% to 12% with decreasing calibre. However, bouton apposition length decreased in parallel, yielding a fairly uniform bouton density among dendrites of different calibre. The lack of correlation between packing density and dendrite calibre was also evident when the sample of dendrites was broken down into subsamples based on content of amino acid immunoreactivity. The latter analysis also revealed that both the relative covering and density of boutons containing inhibitory amino acids (57%; glycine and/or GABA) and glutamate (38%), respectively, did not vary systematically with dendrite calibre. Combined, the data indicate that in non-stem dendrites the proportion of excitatory and inhibition inputs does not change systematically throughout the dendritic arborizations of spinal α-motoneurons. Thus, spinal motoneurons can, with respect to the general synaptic architecture, be divided into two main compartments, i.e. the proximal soma-juxtasomatic compartment (including stem dendrites) and the distal dendritc compartment. The proximal domain is under a powerful glycine and/or GABA influence. Finally, based on the data presented here and previously published data, it was calculated that spinal α-motoneurons receive in the range of 50–140×103 synaptic boutons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050308
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 28
    Electronic Resource
    Electronic Resource
    A possible basic cortical microcircuit called ’’cascaded inhibition’’Results from cortical network models and recording experiments from striate simple cells (1998)
    Springer
    Experimental brain research 122 (1998), S. 318-332 
    Details
    ISSN: 1432-1106
    Keywords: Key words Cortical microcircuits ; Relative modulation ; Push-pull mechanism ; Simple cell ; Cascaded inhibition ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The robust behavior, the degree of response linearity, and the aspect of contrast gain control in visual cortical simple cells are (amongst others) the result of the interplay between excitatory and inhibitory afferent and intracortical connections. The goal of this study was to suggest a simple intracortical connection pattern, which could also play a role in other cortical substructures, in order to generically obtain these desired effects within large physiological parameter ranges. To this end we explored the degree of linearity of spatial summation in visual simple cells experimentally and in different models based on half-wave rectifying cells (’’push-pull models’’). Visual cortical push-pull connection schemes originated from antagonistic motor-control models. Thus, this model class is widely applicable but normally requires a rather specific design. On the other hand we showed that a more generic version of a push-pull model, the so-called cascaded inhibitory intracortical connection scheme, which we implemented in a biologically realistic simulation, naturally explains much of the experimental data. We investigated the influence of the afferent and intracortical connection structure on the measured linearity of spatial summation in simple cells. The analysis made use of the relative modulation measure, which is easy to apply but is limited to moving sinusoidal grating stimuli. We introduced two basic push-pull models, where the order of threshold nonlinearity and linear summation is reversed. Very little difference is observed with the relative modulation measure for these models. Alterative models, like half-wave squaring models, were also briefly discussed. Of all model parameters, the ratio of excitation to inhibition in the simple cell exerts the most crucial influence on the relative modulation. Linearity deteriorates as soon as excitatory and inhibitory inputs are imbalanced and the relative modulation drops. This prediction was tested experimentally by extracellular recordings from cat area 17 simple cells and we found that about 62% showed a significant deviation from linear behavior. The problem that individual basic push-pull models are hard to distinguish experimentally led us to suggest a different solution. In order to generically account for the observed behavior (e.g., imbalance of excitation versus inhibition), we suggested a rather generic version of a push-pull model where it no longer mattered about (the hard-to-distinguish) fine differences in connectivity. Thus, we introduced a new class of biophysically realistic models (’’cascaded inhibition’’). This model class requires very little connection specificity and is therefore highly robust against parameter variations. Up to 25 cells are connected to each target cell. Thereby a highly interconnected network is generated, which also leads to disinhibition at some parts of an individual receptive field. We showed that the performance of these models simulates the degree of linearity and its variability in recal simple cells with comparatively high accuracy. This behavior can be explained by the self-regulating properties of a cascaded inhibitory connection scheme by which the balance between excitation and inhibition at a given cell is improved by the joint network effects. The virtues and the generic design of this connection pattern, therefore, allow to speculate that it is used also in other parts of the cortex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050520
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 29
    Electronic Resource
    Electronic Resource
    Flexor reflex afferents reset the step cycle during fictive locomotion in the cat (1998)
    Springer
    Experimental brain research 122 (1998), S. 339-350 
    Details
    ISSN: 1432-1106
    Keywords: Key words Fictive locomotion ; Proprioception ; Flexor reflex ; Spinal cord ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The generation of locomotor-like spinal rhythms has been proposed to involve two neural centres with mutual reciprocal inhibition (Graham Brown’s ”half-centre” hypothesis). Much later a particular set of segmental flexor reflex pathways were described as being organized in accordance with this half-centre hypothesis. As these pathways became operative following injection of monoaminoxidase inhibitors and l-3,4-dihydroxyphenylalanine (l-dopa), i.e. under the same conditions under which a spontaneous locomotor activity may develop, it was assumed that these particular pathways and spinal rhythm generators involve the same neuronal networks. In order to give further evidence to this hypothesis, we investigated whether short trains to ”flexor reflex afferents” (FRA) reset the spinal locomotor rhythm, i.e. shorten or lengthen the stimulated cycle after which the regular rhythm is resumed with step cycles of the original duration. The experiments were performed in anaemically decapitated, high-spinal curarized cats. A steady locomotor rhythm was induced by injection of nialamide and l-dopa and the influence of electrical stimulation (trains of 50–1000 ms) of FRA (joint, cutaneous, and group II and III muscle afferents) onto this rhythm was tested. Stimulation of FRA induced a clear resetting of the locomotor rhythm, which was mainly characterized by a flexion reflex pattern: during the extension phase the extensor activity was interrupted and a flexion phase was initiated; during the late flexion phase mainly a prolongation of that phase with a variable change of the following extension phase was induced. In addition to this prevailing pattern, stimulation of some nerves (in particular nerves to more distal extensors and the sural nerve) could often prolong extension, when stimulated during the late extension, or terminate the flexor burst and initiate a new extension phase, when stimulated during the late flexion phase. This pattern is probably due to the concomitant stimulation of group I afferents in the case of the muscle nerves and to separate non-FRA pathways in the case of the sural nerve. The results demonstrate that the interneurones of the FRA pathways, which are operative during l-dopa-induced locomotion in spinal animals, can be considered as neuronal elements of the rhythm-generating network for locomotion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050522
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 30
    Electronic Resource
    Electronic Resource
    Evidence for a strychnine-sensitive mechanism and glycine receptors involved in the control of urethral sphincter activity during micturition in the cat (1998)
    Springer
    Experimental brain research 119 (1998), S. 297-306 
    Details
    ISSN: 1432-1106
    Keywords: Key words Spinal inhibition ; Interneurons ; Micturition ; Bladder-sphincter dyssynergia ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Micturition in the decerebrate cat is characterized by a coordinated bladder contraction and a simultaneous decrease in external urethral sphincter (EUS) efferent activity. Without the suppression of EUS activity, voiding is significantly impaired, resulting in a state sometimes referred to as bladder-sphincter dyssynergia. The aim of the present study was to determine whether glycinergic inhibition contributes to the suppression of EUS activity during micturition evoked by bladder distension or electrical stimulation of the pontine micturition center (PMC) in decerebrate cats. Using subconvulsive intravenous doses of strychnine (0.1–0.24 mg/kg), we examined changes in bladder and EUS electroneurographic (ENG) activity during micturition. Following subconvulsive doses of strychnine, tonic EUS ENG activity increased during bladder filling in five of six animals. In the presence of strychnine, it was possible to evoke reflex bladder contractions of similar duration and peak pressure to those observed before strychnine administration. However, there was an absence of suppression of EUS ENG activity during the bladder contractions in all the animals. To determine whether the changes in sphincter activity could be due to strychnine acting at glycine receptors on EUS motoneurons, sacral spinal tissue was processed for a structural protein (gephyrin) associated with the glycine receptor. Motoneurons in Onuf′s nucleus in S1 were identified using choline acetyltransferase immunohistochemistry and subsequently processed with a gephyrin monoclonal antibody. Abundant gephyrin labeling was evident throughout Onuf′s nucleus. Since Onuf′s nucleus is made up of EUS and other motoneuron populations, a sample of antidromically identified urethral and anal sphincter motoneurons were intracellularly labeled with tetramethylrhodamine dextran (TMR-D) and then processed with the gephyrin antibody. Using dual-beam confocal microscopy, gephyrin immunoreactivity was observed on the soma and proximal processes of individual EUS motoneurons in both male and female animals. It was concluded that a strychnine-sensitive mechanism contributes to the suppression of sphincter activity normally observed during voiding. Although glycinergic inhibition may affect several components of the circuitry responsible for micturition, it appears that the suppression of EUS motoneurons during micturition may be partly due to a direct glycinergic inhibition of the EUS motoneurons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050345
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 31
    Electronic Resource
    Electronic Resource
    Activity of thoracic and lumbar epaxial extensors during postural responses in the cat (1998)
    Springer
    Experimental brain research 119 (1998), S. 315-323 
    Details
    ISSN: 1432-1106
    Keywords: Key words Stance posture ; Balance ; Epaxial muscles ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  This study examined the role of trunk extensor muscles in the thoracic and lumbar regions during postural adjustments in the freely standing cat. The epaxial extensor muscles participate in the rapid postural responses evoked by horizontal translation of the support surface. The muscles segregate into two regional groups separated by a short transition zone, according to the spatial pattern of the electromyographic (EMG) responses. The upper thoracic muscles (T5-9) respond best to posteriorly directed translations, whereas the lumbar muscles (T13 to L7) respond best to anterior translations. The transition group muscles (T10-12) respond to almost all translations. Muscles group according to vertebral level rather than muscle species. The upper thoracic muscles change little in their response with changes in stance distance (fore-hindpaw separation) and may act to stabilize the intervertebral angles of the thoracic curvature. Activity in the lumbar muscles increases along with upward rotation of the pelvis (iliac crest) as stance distance decreases. Lumbar muscles appear to stabilize the pelvis with respect to the lumbar vertebrae (L7-sacral joint). The transition zone muscles display a change in spatial tuning with stance distance, responding to many directions of translation at short distances and focusing to respond best to contralateral translations at the long stance distance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050347
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 32
    Electronic Resource
    Electronic Resource
    The cat vertebral column: stance configuration and range of motion (1998)
    Springer
    Experimental brain research 119 (1998), S. 324-332 
    Details
    ISSN: 1432-1106
    Keywords: Key words Vertebral column ; Antigravity support ; Scapula ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  This study examined the configuration of the vertebral column of the cat during independent stance and in various flexed positions. The range of motion in the sagittal plane is similar across most thoracic and lumbar joints, with the exception of a lesser range at the transition region from thoracic-type to lumbar-type vertebrae. The upper thoracic column exhibits most of its range in dorsiflexion and the lower thoracic and lumbar in ventroflexion. Lateral flexion is limited to less than 5° at all segments. The range in torsion is almost 180° and occurs primarily in the midthoracic region, T4-T11. Contrary to the depiction in most atlases, the standing cat exhibits several curvatures, including a mild dorsiflexion in the lower lumbar segments, a marked ventroflexion in the lower thoracic and upper lumbar segments, and a profound dorsiflexion in the upper thoracic (above T9) and cervical segments. The curvatures are not significantly changed by altering stance distance but are affected by head posture. During stance, the top of the scapula lies well above the spines of the thoracic vertebrae, and the glenohumeral joint is just below the bodies of vertebrae T3-T5. Using a simple static model of the vertebral column in the sagittal plane, it was estimated that the bending moment due to gravity is bimodal with a dorsiflexion moment in the lower thoracic and lumbar region and a ventroflexion moment in the upper thoracic and cervical region. Given the bending moments and the position of the scapula during stance, it is proposed that two groups of scapular muscles provide the major antigravity support for the head and anterior trunk. Levator scapulae and serratus ventralis form the lateral group, inserting on the lateral processes of cervical vertebrae and on the ribs. The major and minor rhomboids form the medial group, inserting on the spinous tips of vertebrae from C4 to T4. It is also proposed that the hypaxial muscles, psoas major, minor, and quadratus lumborum could support the lumbar trunk during stance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050348
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 33
    Electronic Resource
    Electronic Resource
    Changes in synaptology of adult cat spinal α-motoneurons after axotomy (1998)
    Springer
    Experimental brain research 118 (1998), S. 1-13 
    Details
    ISSN: 1432-1106
    Keywords: Key words Nerve injury ; Retrograde reaction ; Spinal cord ; Electron microscopy ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The aim of this electron-microscopic study was to analyze the distribution of synaptic contacts on the cell bodies and dendrites of permanently axotomized adult cat spinal α-motoneurons. Following transection and ligation of the medial gastrocnemius nerve, the synaptic covering of the cell bodies and three different dendritic compartments of homonymous α-motoneurons was analyzed quantitatively at 3, 6, and 12 weeks postoperatively. The synaptic boutons were classified according to their size and the shape of their synaptic vesicles. On the soma, a transient increase in the number of boutons was noted at 3 weeks and 6 weeks postoperatively, while after 12 weeks the bouton number had decreased to half of its normal value. The transient increase was mainly due to an increase in the number of F-type boutons. At 12 weeks postoperatively, the synaptic covering was reduced by 83% on the soma and by 57% on the proximal dendrites. In the distal dendritic regions, the values for synaptic covering remained largely unchanged. In summary, axotomized motoneurons exhibit a reduction in synaptic covering which is maximal on the cell body and becomes less pronounced centrifugally along the dendrites. However, if also taking into account the loss of distal dendritic branches that occurs in axotomized motoneurons, the total loss of boutons is several times larger in the dendrites than on the soma.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050249
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 34
    Electronic Resource
    Electronic Resource
    Differential activation of spinal dorsal horn units by subcutaneous formalin injection in the cat: an electrophysiological study (1998)
    Springer
    Experimental brain research 118 (1998), S. 14-18 
    Details
    ISSN: 1432-1106
    Keywords: Key words Subcutaneous formalin ; Dorsal horn ; Nociception ; Central neuronal changes ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  In our previous report we found that subcutaneous (s.c.) formalin injection into the cutaneous receptive field (RF) of dorsal horn wide-dynamic-range (WDR) units and nociceptive primary afferent units resulted in a tonic, long-lasting increase in firing. However, s.c. formalin injection only resulted in a short-lasting increase in firing of non-nociceptive primary afferent units. In the present study, by using extracellular single-unit recording techniques we further studied effects of s.c. formalin on response properties of identified superficial-layer nociceptive-specific (NS) units and deeper-layer, low-threshold mechanoreceptive (LTM) units of L7 dorsal horn in urethane-chloralose-anesthetized cats. s.c. formalin injection into the RF of NS units resulted in a tonic, long-lasting increase in firing (7.08 ± 0.42 spikes/s, n = 5), for more than 1 h, compared with the spontaneous background (1.42 ± 0.03 spikes/s, n = 5). Formalin injection into the RF of LTM units also resulted in an increase in firing; however, the duration was short-lasting, for 25–520 s (152.92 ± 46.73 s, n = 12). The present study demonstrated that s.c. injection of dilute formalin solution resulted in activation of not only nociceptive but also non-nociceptive dorsal horn units, suggesting that tissue injury caused by s.c. formalin results in vigorous injury discharges of peripheral nerve terminals, which subsequently leads to activation of primary afferent neurons and secondary dorsal horn neurons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050250
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 35
    Electronic Resource
    Electronic Resource
    Short-term changes in neck muscle and eye movement responses following unilateral vestibular neurectomy in the cat (1998)
    Springer
    Experimental brain research 120 (1998), S. 439-449 
    Details
    ISSN: 1432-1106
    Keywords: Key words Antagonist neck muscles ; Eye movements ; Unilateral vestibular neurectomy ; Visual substitution ; Motor strategies ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The purpose of this study was to investigate changes in neck muscle and eye movement responses during the early stages of vestibular compensation (first 3 weeks after unilateral vestibular neurectomy, UVN). Electromyographic (EMG) activity from antagonist neck extensor (splenius capitis) and flexor (longus capitis) muscles and eye movements were recorded during sinusoidal visual and/or otolith vertical linear stimulations in the 0.05–1 Hz frequency range (corresponding acceleration range 0.003–1.16 g) in the head-fixed alert cat. Preoperative EMG activity from the splenius and longus capitis muscles showed a pattern of alternate activation of the antagonist neck muscles in all the cats. After UVN, two motor strategies were observed. For three of the seven cats, the temporal activation of the individual neck muscles was the same as that recorded before UVN. For the other four cats, UVN resulted in a pattern of coactivation of the flexor and extensor neck muscles because of a phase change of the splenius capitis. In both subgroups, the response patterns of the antagonist neck muscles were consistent for each cat independently of the experimental conditions, throughout the 3 weeks of testing. Cats displaying alternate activation of antagonist neck muscles showed an enhanced gain of the visually induced neck responses, particularly in the high range of stimulus frequency, and a gain decrease in the otolith-induced neck responses at the lowest frequency (0.25 Hz) only. By contrast, for cats with neck muscle coactivation, the gain of the visually induced neck responses was basically unaffected relative to preoperative values, whereas otolith-induced neck responses were considerably decreased in the whole range of stimulation. As concerns oculomotor responses, results in the two subgroups of cats were similar. The optokinetic responses were not affected by the vestibular lesion. On the contrary, otolith-induced eye responses showed a gain reduction and a phase lead. Deficits and short-term changes after UVN of otolith- and semicircular canal-evoked collic and ocular responses are compared.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050417
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 36
    Electronic Resource
    Electronic Resource
    Feline caudofemoralis muscle Muscle fibre properties, architecture, and motor innervation (1998)
    Springer
    Experimental brain research 121 (1998), S. 76-91 
    Details
    ISSN: 1432-1106
    Keywords: Key words Motor nucleus ; EMG ; Muscle architecture ; Muscle fiber ; Caudofemoralis ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Feline caudofemoralis (CF) is a promising preparation in which to study the properties of mammalian fast-twitch skeletal muscle, but little is known about its muscle fiber properties, architecture, and motor innervation. We used histochemical techniques to confirm that it contained predominantly type IIB fibers (95±2%, n=8, with six of eight muscles composed exclusively of type IIA and IIB fibers), but physiological experiments showed less fatiguability than for the type IIB component of medial gastrocnemius. This may be related to the surprisingly strong and regular recruitment of CF during repetitive tasks such as walking and trotting, which we demonstrated electromyographically. We measured muscle length over the anatomical range of motion for CF (∼0.6–1.2 L 0) and estimated working length during walking and trotting (∼0.95–1.15 L 0). The specific tension was similar to that of the exclusively slow-twitch soleus muscle (31.2±4.7 N/cm2 compared with 31.8±4.1 N/cm2; P〉0.8). Single fiber dissections of CF revealed a series-fibered architecture with a mean of 2.3 fibers, each 2.5 cm long, required to span the fascicle length. We identified two neuromuscular compartments in CF by cutting one of the two nerve branches innervating CF and depleting the glycogen stores in the intact motor units. These compartments were in parallel and extended the length of the muscle; their electromyographic activity was similar during various natural behaviors. CF and gluteus maximus motoneurons were labeled concurrently with a combination of fluorescent, retrograde tracers including Fluororuby, Fluorogold and Fast Blue. The CF motor nucleus was located in L7-S1, overlapping and intermingling extensively with the nucleus of the adjacent gluteus maximus muscle. Distributions of CF motoneuron diameter revealed one large peak around 50–55 µm, with relatively few small-diameter (less than 35 µm) cells. Using estimates of the total number of fibers in three muscles and the estimated number of α-motoneurons for those same muscles, we calculated a mean innervation ratio of ∼270, which is at the low end of the innervation ratios for type IIB motor units from other feline muscles and more similar to type IIA motor units. In general, CF appears to be a useful preparation in which to study the properties of fast-twitch muscle, but these properties may vary somewhat from type IIB fibers from different muscles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050439
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 37
    Electronic Resource
    Electronic Resource
    Indications for coupling between feline spinocervical tract neurones and midlumbar interneurones (1998)
    Springer
    Experimental brain research 119 (1998), S. 39-46 
    Details
    ISSN: 1432-1106
    Keywords: Key words Spinal cord ; Spinocervical tract ; Interneurones ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The possibility of collateral segmental actions of spinocervical tract (SCT) neurones upon interneurones with input from cutaneous and group II muscle afferents was investigated in deeply anaesthetized cats. To this end, intracellular and/or extracellular recordings were made from 35 dorsal horn and 15 intermediate zone interneurones in midlumbar segments of the spinal cord and effects of stimulation of the ipsilateral dorso-lateral funiculus (DLF) at C3 and C1 levels, i.e. below and above the lateral cervical nucleus where axons of SCT cells terminate, were compared. The stimuli applied at the C3 segment were within the range of stimuli (50–100 μA) required for antidromic activation of SCT neurones in the same experiment. Those applied at the C1 segment (200–500 μA) were at least 3 times stronger than C3 stimuli. Under the same experimental conditions, long ascending and descending tract neurones (dorsal spino-cerebellar and rubro-spinal tract neurones) with axons in the DLF were activated at similar thresholds from the C1 and C3 segments. Intracellular recordings were made from 29 interneurnoes of which 19 (65%) were dorsal horn and 10 (35%) were intermediate zone interneurones. Excitatory postsynaptic potentials (EPSPs) evoked by single stimuli applied at the C3 segment, but not the C1 segment, were found in 14 (48%) of those interneurones; their latencies (3.0–5.7 ms) and frequency following with only minimal temporal facilitation were as required for potentials being evoked monosynaptically by the fastest conducting SCT neurones. Extracellular recordings were made from 30 interneurones (24 dorsal horn and 6 intermediate zone interneurones), and in these neurones spike potentials induced from the C3, but not from the C1 segment, were evoked only by short trains of stimuli. However, their latencies from the first effective stimulus (4.3–5.4 ms) were compatible with mono- or oligosynaptically mediated collateral actions of SCT neurones. They were found in 10 (33%) of the 30 investigated interneurones. Similar effects of C3 stimuli were found in similar proportions of dorsal horn interneurones and intermediate zone interneurones. Indications were also found for synaptic actions evoked by C3 stimuli that could not be attributed to direct collateral actions of SCT neurones. In some intracellularly recorded dorsal horn interneurones, short-latency EPSPs were evoked from the C3 segment by the 2nd or 3rd stimulus in the train, but not by single stimuli. In other dorsal horn and intermediate zone interneurones, inhibitory postsynaptic potentials (IPSPs) were evoked from the C3 segment at minimal latencies (2.7–3.2 ms), which might be too short to allow their mediation via SCT neurones. We conclude that SCT neurones might be used to forward information from muscle group II and cutaneous afferents not only to neurones in the lateral cervical nucleus and via them to thalamus and cerebral cortex but also to interneurones in spinal reflex pathways. Thereby reflex actions evoked from group II and cutaneous afferents might be co-ordinated with responses mediated by supraspinal neurones. We conclude also that dorsal horn and intermediate zone mid-lumbar interneurones might contribute to the previously reported di-and poly-synaptic excitation or inhibition of postsynaptic dorsal column (PSDC), spinothalamic tract (STT) and spinomesencephalic tract (SMT) neurones by collateral actions of SCT cells. Thereby these interneurones might contribute to the co-ordination of responses mediated by various populations of supraspinal neurones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050317
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 38
    Electronic Resource
    Electronic Resource
    Spatial disparity coding in the superior colliculus of the cat (1998)
    Springer
    Experimental brain research 119 (1998), S. 333-344 
    Details
    ISSN: 1432-1106
    Keywords: Key words Disparity sensitivity ; Binocular interactions ; Superior colliculus ; Stereopsis ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Cells in the superficial layers of the superior colliculus of the cat have mainly binocular receptive fields. The aim of the present experiment was to investigate the sensitivity of these cells to horizontal spatial disparity. Unit recordings were carried out in the superficial layers of the superior colliculus of paralyzed and anesthetized cats. Centrally located receptive fields were mapped, separated using prisms, and then stimulated simultaneously using two luminous bars optimally adjusted to the size of the excitatory region of the receptive fields. Only binocular cells were tested, and 65% of these units were found to be sensitive to spatial disparities. Some cells (20%) were clearly insensitive to spatial disparity and the remaining 15% showed complex, unclassifiable interactions. The sensitive cells could be divided into four classes based on their disparity-sensitivity profiles: 38% showed excitatory interactions, whereas 9% showed inhibitory interactions. Moreover, 11% and 7% of the cells responded, respectively, to crossed or uncrossed disparities, and were classified as near cells and far cells. Whereas the general shapes of the sensitivity profiles were similar to those of cells in areas 17–18, selectivity in the superior colliculus was significantly coarser. The superficial layers of the superior colliculus project topographically to the deep layers of the superior colliculus, which are known to contain circuits involved in the control of ocular movements. The results thus suggest that disparity-sensitive cells of the superior colliculus could feed information to these oculomotor neurons, allowing for the localization and fixation of objects on the appropriate plane of vision.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050349
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 39
    Electronic Resource
    Electronic Resource
    Mechanical sensitivity of muscle afferents in a nerve treated with colchicine (1998)
    Springer
    Experimental brain research 119 (1998), S. 391-398 
    Details
    ISSN: 1432-1106
    Keywords: Key words Mechanoreceptor ; Axoplasm ; Muscle spindle ; Colchicine ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The experiments reported here demonstrate that the mechanical sensitivity of peripheral nerve fibres typically seen after injury can be induced without overtly injuring the nerve, but by simply applying colchicine topically to the nerve. In cats anaesthetised with pentobarbitone sodium, the medial gastrocnemius nerve was exposed and 10 mM colchicine applied topically for 15 min. The animals recovered from the operation normally and showed no subsequent motor deficit. Six days later animals were re-anaesthetised, a laminectomy carried out and responses recorded in single afferents at the level of the dorsal root. It was found that many afferents, particularly those with conduction velocities in the group II–III range, had become sensitive to local mechanical stimulation of the nerve in the region treated with colchicine and showed slowly adapting responses to stretch of the nerve. Many of the smaller fibres exhibited spontaneous activity. Mechanically sensitive afferents exhibited impulse conduction blocks at the colchicine-treated site. Some afferents, which appeared to conduct impulses normally through the treated region, were associated with muscle receptors having normal response properties. However, other muscle receptors were clearly abnormal and were insensitive to muscle stretch or contraction or exhibited only phasic responses. When the nerve was cut proximal to the colchicine-treated site, some, but not all, spontaneous activity was abolished. It was subsequently shown using a collision technique that the activity in some axons had its origin in the cell body in the dorsal root ganglion. In one experiment, it was shown that after nerve section proximal to the colchicine-treated region three of five axons switched their activity from a peripheral to a central origin. It is postulated that colchicine disrupts fast axonal transport of mechanically sensitive or voltage-sensitive ion channels, from the cell body to the peripheral terminals of the axons, leading to an accumulation of these channels at the treated site. This induces mechanical sensitivity and spontaneous activity. It is postulated that interruption of a retrogradely transported signal induces the spontaneous activity in the cell body. These experiments suggest that an important influence is exerted by the cell body on the peripheral terminals of mechanoreceptors to confer on them their normal response properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050354
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 40
    Electronic Resource
    Electronic Resource
    Positron emission tomography reveals changes in global and regional cerebral blood flow during noxious stimulation of normal and inflamed elbow joints in anesthetized cats (1998)
    Springer
    Experimental brain research 118 (1998), S. 439-446 
    Details
    ISSN: 1432-1106
    Keywords: Key words Positron emission tomography ; Articular nociception ; Cerebral blood flow ; Joint inflammation ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  In cats the global (gCBF) as well as the regional cerebral blood flow (rCBF) and blood pressure were measured before, during, and after noxious inward and outward rotations of normal and inflamed elbow joints. The animals were anesthetized with halothane and immobilized by gallamine triethiodide. The gCBF as well as the rCBF were measured using positron emission tomography (PET) with a camera specifically designed for use in small animals. Slow intravenous bolus injections of 15O-labeled water were followed by 3-min acquisition of regional radioactivity starting at the time of injection. In all experiments the gCBF as well as the blood pressure were increased by noxious inward-outward rotations of the normal and of the inflamed joint, whereas the blood pressure and the rCBF remained unchanged during bolus injections under control conditions (without any joint movement). Movements of the inflamed joint evoked significantly greater increases in blood pressure and gCBF than corresponding ones of the normal joint. These increases in gCBF were paralleled by increases in rCBF along the complete anterior to posterior axis of the brain. Again, the increases in rCBF were larger, more extensive and more uniform following the stimulation of the inflamed joint relative to the results obtained with stimulation of the normal joint. No significant laterality was seen, but when an atlas-based region of interest (ROI) analysis was carried out and when the individual variations in rCBF were removed with two-way ANOVA, significant differences were disclosed in rCBF between the stimulated condition and the resting condition in a large number of brain regions. In particular, noxious rotation of the normal (right) elbow joint induced a significant increase in rCBF over the cerebral cortex and in the right thalamus and hippocampus. The same stimulation of the (left) inflamed joint induced a significant increase in rCBF throughout the brain; the biggest increase being over the right posterior cortex. It is concluded that under the conditions of the present experiments the generally accepted autoregulation of the cerebral blood flow is not fully functioning, and various factors that may be responsible for this failure (which obscures rCBF differences) are discussed. The more pronounced increases in rCBF when moving inflamed joints instead of normal ones is thought to be a direct consequence of the peripheral sensitization of the articular nociceptors and the consequent central hyperexcitability induced in the articular nociceptive pathways.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050300
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 41
    Electronic Resource
    Electronic Resource
    Effect of head position on postural orientation and equilibrium (1998)
    Springer
    Experimental brain research 122 (1998), S. 175-184 
    Details
    ISSN: 1432-1106
    Keywords: Key words Balance ; Sensorimotor transformation ; Neck proprioception ; Vestibular system ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  This study examined (1) how changes in head position affect postural orientation variables during stance and (2) whether changes in head position affect the rapid postural response to linear translation of the support surface in the horizontal plane. Cats were trained to stand quietly on a moveable platform and to maintain five different head positions: center, left, right, up, and down. For each head position, stance was perturbed by translating the support surface linearly in 16 different directions in the horizontal plane. Postural equilibrium responses were quantified in terms of the ground reaction forces, kinematics, dynamics (net joint torques), body center of mass, and electromyographic (EMG) responses of selected limb and trunk muscles. A change in head position involved rotation of not only the neck but also the scapulae and anterior trunk. Tonic EMG levels were modulated in several forelimb and scapular muscles but not hindlimb muscles. Finally, large changes in head orientation in both horizontal and vertical planes did not hamper the ability of cats to maintain postural equilibrium during linear translation of the support surface. The trajectory of the body’s center of mass was the same, regardless of head position. The main change was observed in joint torques at the forelimbs evoked by the perturbation. Evoked EMG responses of forelimb and scapular muscles were modulated in terms of magnitude but not spatial tuning. Hindlimb responses were unchanged. Thus, the spatial and temporal pattern of the automatic postural response was unchanged and only amplitudes of evoked activity were modulated by head position.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050505
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 42
    Electronic Resource
    Electronic Resource
    Visually evoked cortical potentials in awake cats during saccadic eye movements (1998)
    Springer
    Experimental brain research 122 (1998), S. 203-213 
    Details
    ISSN: 1432-1106
    Keywords: Key words Saccadic suppression ; Corollary discharge ; Visually evoked potential ; Striate cortex ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Visually evoked potentials (VEPs) measured under conditions of retinal image stabilization that minimized the influences of visual masking and smearing were averaged from electroencephalographic records measured from striate cortex of three cats. The amplitudes of the VEPs increased around saccade initiation. The grating-evoked potentials obtained at different times relative to the saccade exhibited changes in waveform shape that could be attributed to a saccade-evoked potential. The changes in the shape of the waveform were reasonably accounted for by the summation of the grating-evoked potential (produced when the cat did not make a saccade) and an appropriately timed saccade-evoked potential. The fundamental amplitudes of the residual potentials were computed and found to vary across the time course of the saccade. These observations suggest that there are other influences besides visual masking that are exerted early in the visual pathway to modulate visual processing during saccadic eye movements. A corollary discharge process is the most likely candidate to exert these influences.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050508
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 43
    Electronic Resource
    Electronic Resource
    Neuronal responsiveness to three-dimensional motion in cat posteromedial lateral suprasylvian cortex (1998)
    Springer
    Experimental brain research 122 (1998), S. 214-226 
    Details
    ISSN: 1432-1106
    Keywords: Key words Visual perception ; Three-dimensional motion ; Motion disparity ; Size change ; Posteromedial lateral suprasylvian cortex ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The neuronal responsiveness to three-dimensional (3D) motion in cat posteromedial lateral suprasylvian (PMLS) cortex was studied using a computer-controlled, stereoscopic 3D graphic display capable of reproducing the major visual cues for natural 3D motion, including motion disparity, size, texture, and shading changes. The animals were anesthetized with nitrous oxide supplemented with alphaxalone, and paralysis prevented eye movement. Systematic investigation of neuronal responsiveness to 3D motions in 26 different directions revealed that more than half of the PMLS cells were selectively responsive to approaching (AP cells, 112 of 271) or recessive motion (RC cells, 64 of 271). The remaining cells were selectively responsive to frontoparallel motion (FP cells, 49 of 271) or nonselectively responsive to motion in multiple directions (NS cells, 46 of 271). The dependency on these visual cues was investigated as a reduction in the response amplitude or the response selectivity for the removal of a single cue from the motion stimuli containing the full visual cues. The AP and RC cells showed a strong dependency on the motion disparity cue, moderate dependency on the size cue, and weak dependency on the texture and shading cues. The FP cells showed no dependency on those visual cues. The cue dependency analysis indicated the existence of nonlinear interactions between those visual cues. Comparison of the responses to a combination of the motion disparity and size cues with the summed responses to each of the individual cues revealed that the responses to the combined cues are roughly predicted as a linear sum between the preferred responses. This comparison also showed nonlinear summation between the nonpreferred responses, i.e., responses to the combined cues were smaller than the summed responses. A similar quasilinear summation of the preferred responses between the two eyes and a nonlinear summation of the nonpreferred responses were found in the AP and RC cells for the motion disparity stimulus. All of these observations indicate that quasilinear and nonlinear interactions of the responses to various stimulus elements underlie the 3D motion responsiveness of the PMLS cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050509
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 44
    Electronic Resource
    Electronic Resource
    Prolonged GABAB receptor-mediated synaptic inhibition in the cat spinal cord: an in vivo study (1998)
    Springer
    Experimental brain research 121 (1998), S. 319-333 
    Details
    ISSN: 1432-1106
    Keywords: Key words Spinal cord ; Synaptic inhibition ; GABAA receptors ; GABAB receptors ; GABA antagonists ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  In pentobarbitone-anaesthetised spinal cats, a comparison was made of the effects of intravenous bicuculline hydrochloride, a GABAA-receptor antagonist, and several (-)-baclofen (GABAB-receptor) antagonists (CGP 35348, 46381, 56999A) on the prolonged inhibition of extensor-muscle monosynaptic reflexes, recorded from lumbar ventral roots, by brief or continuous tetanic stimulation of low-threshold afferent fibres of hindlimb flexor muscles. Two components of brief tetanus inhibition were detected. Whilst possibly of similar central latency, the inhibition associated with GABAB receptors had a longer time course than that reduced by bicuculline. Furthermore, whereas bicuculline reduced primary afferent depolarization, generated by the inhibitory volleys, and detected as dorsal-root potentials, such potentials were generally enhanced by intravenous baclofen antagonists. The inhibition of reflexes during and after continuous (333 Hz) tetanic flexor-nerve stimulation appeared to be predominantly associated with the activation of GABAB receptors. In the period following continuous tetanic flexor-nerve stimulation, during which monosynaptic extensor reflexes were reduced in amplitude, the action potentials of the intraspinal terminations of extensor-muscle group-Ia afferent fibres were reduced in duration, as detected by the time course of the recovery of the threshold to extracellular microstimulation following the arrival of an orthodromic impulse. A reduction in termination action-potential duration also accompanied the reduction by microelectrophoretic (-)-baclofen of the release of excitatory transmitter from group-Ia terminations, both presynaptic effects being blocked by microelectrophoretic baclofen antagonists. However, the reduction of the duration of the action potential of individual group-Ia terminations, which followed continuous flexor-nerve stimulation, was not sensitive to the baclofen antagonist CGP 55845A, but was diminished by bicuculline methochloride. Intravenously administered bicuculline hydrochloride, however, had little or no effect on the inhibition of reflexes following continuous flexor-nerve stimulation. These observations are discussed in the context of possible intraspinal pathways and pre- and postsynaptic mechanisms for GABAA and GABAB receptor-mediated inhibition of the monosynaptic excitation of spinal motoneurones and of the functional significance of central GABAB receptor-associated inhibitory processes, given the relatively minimal effects on motor activity and behaviour produced by baclofen antagonists that penetrate the mammalian blood-brain barrier.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050465
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 45
    Electronic Resource
    Electronic Resource
    Cell behaviour in tubes (1998)
    Springer
    Experimental biology online 3 (1998), S. 1-15 
    Details
    ISSN: 1430-3418
    Keywords: Bone ; Cell behaviour ; Chondrocyte ; Endothelia ; Epitenon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The motile behaviour, growth and reactions of osteoblasts, chondrocytes, epitenal cells and endothelia to culture on extended concave surfaces inside tubes is reported. Time-lapse video observations show that these cells can be successfully grown in quartz tubes for up to 21days. The cells would attach to the concave surfaces even when the radius of curvature was as low as 25 μm. The cells attached to the walls were not oriented. As culturing progressed the chondrocytes, osteoblasts and epitenon cells tended to detach from the walls of the tubes, forming long cords of cells attached to the walls at a few points only. Endothelial cells did not detach. These cords showed extensive lamellipodial activity at their points of attachment to the tube wall. The cells in these cords do not show contact inhibition of movement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00898-998-0002-6
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 46
    Electronic Resource
    Electronic Resource
    Vascularized knee joint transplantation in man: a report on the first cases (1998)
    Springer
    Transplant international 11 (1998), S. S487 
    Details
    ISSN: 1432-2277
    Keywords: Key words Knee joint ; Vascularized graft ; Bone ; Transplantation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Four transplantations of an allogeneic vascularized human knee joint were performed at the Trauma Center Murnau between April 1996 and July 1997. The indication for the procedure was the total loss of the knee joint including the extensor apparatus due to severe trauma. These were the first transplants of this type. Management of patients started with closure of soft-tissue defects. After successful completion, stabilization was achieved with femoral and tibial nails plus a temporary arthroplasty. AB0 compatibility and a negative cross-match were the main criteria for selecting patients for transplantation. Interlocking compression nails were used for osteosynthesis. Vascular anastomoses between graft and recipient vessels were established by the end-to-side technique. Immunosuppression was started as a quadruple induction therapy for 3 days, then reduced to a two-drug maintenance therapy with cyclosporine and azathioprine. Six months posttransplantation the osteotomies were bridged by callus and the patients became completely mobile. Radiographic and histological examinations revealed vital graft tissue.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001470050525
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 47
    Electronic Resource
    Electronic Resource
    Role of the retrorubral nucleus in striatally elicited orofacial dyskinesia in cats: effects of muscimol and bicuculline (1998)
    Springer
    Psychopharmacology 140 (1998), S. 150-156 
    Details
    ISSN: 1432-2072
    Keywords: Key words Retrorubral nucleus ; A8 ; Oro-facial dyskinesia ; Striatum ; GABA ; Bicuculline ; Muscimol ; DPI (3 ; 4 dihydroxy-phenylimino)-2-imidazoline ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Orofacial dyskinesia (OFD) is a disorder characterized by involuntary movements of the oral and facial muscles. OFD attacks can be elicited acutely in cats by local injections of dopaminergic agents into the anterodorsal part (r-CRM) of the caudate nucleus. Because the dopaminergic A8 cell group, being embedded in the retrorubral nucleus (RRN), gives rise to fibres which terminate in the r-CRM, two questions arose: (1) whether the A8 cell group forms part of the circuitry that directs and/or modulates OFD, and (2) whether GABA-ergic compounds in the RRN play a role in OFD, and if so, whether a pharmacological GABA-ergic intervention of the activity in the RRN modulates or mediates OFD. For this purpose, the activity of the RRN was manipulated with local injections of the GABAA agonist muscimol and antagonist bicuculline. These local injections into the RRN were subsequently combined with manipulations of dopamine transmission in the r-CRM with local injections of the selective DAi receptor agonist (3,4-dihydroxyphenylimino)-2-imidazoline. The present study shows that local injections of GABA-ergic compounds into the RRN do not elicit OFD attacks in cats, but can modulate oral behaviour elicited from the r-CRM. The latter effect is dose dependent and GABA-ergic specific.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002130050752
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 48
    Electronic Resource
    Electronic Resource
    Konfokale Laser-Scanning Mikroskopie (CLSM) (1998)
    Springer
    Mund-, Kiefer- und Gesichtschirurgie 2 (1998), S. 141-145 
    Details
    ISSN: 1434-3940
    Keywords: Schlüsselwörter Konfokale Laser-Scanning-Mikroskopie ; Knochen ; Histotomographie ; Key words Confocal laser scanning microscopy ; Bone ; Histotomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Objectives: Fixation (formalin), decalcification (sections) or mechanical treatment (grinding) all bear the risk of artifacts occurring during hard-tissue histology. Because studies on the etiology of pathological changes mostly focus on subclinical lesions, artifacts can simulate early changes or even be superimposed on existing changes. The objective of this study was to determine how artifacts can be reduced. Material and methods: In confocal laser scanning microscopy (CLSM) a focused laser beam scans the surface of the specimens and penetrates into the tissue. The intensity of the remitted light is recorded. The confocal effect is due to an extremely small aperture (pinhole), excluding light from out-of-focus planes of the sample. By stepwise movement of the object table, a tomographic series of tomographic images is obtained. Sound cortical bone samples of the lower jaw (n = 20) were studied by light microscopy and by CLSM, visualizing identical areas of a ground sectioned sample after H & E staining. Additionally, embedded and fresh blocks of tissue of the same bone sample were studied histotomographically in the CLSM. Results: (1) Light microscopic micromorphology of cortical bone can be visualized adequately in the CLSM; (2) many structures that can be visualized by light microscopy only after special staining (e.g., osteozyte processes) can be visualized by the CLSM using sample blocks without pretreatment. Conclusion: (1) Nondestructive subsurface histotomography by CLSM totally excludes mechanical artifacts; (2) physicochemical artifacts can be handled more easily because fresh samples can be studied; (3) pseudo-three-dimensional imaging allows histological interpretation of the tissue that is equivalent to macroscopic tomographic techniques (CT, MRT).
    Notes: Durch Fixierung (Formalin), Entkalkung (Schnitte) oder mechanische Bearbeitung (Schliffe) besteht bei der Hartgewebshistologie das Risiko physikalisch-chemischer oder mechanischer Artefakte. Da Studien zur Ätiopathogenese pathologischer Veränderungen meist auf subklinische Läsionen zielen, besteht die Gefahr, daß Artefakte frühe Veränderungen vortäuschen oder vorhandene überdecken. Es wird der Frage einer artefaktminimierten Histologie nachgegangen. Bei der konfokalen Laser-Scanning-Mikroskopie (CLSM) rastert ein monochromatischer Laserstrahl über die Probenoberfläche und dringt in das Gewebe ein. Die Intensität der remittierten Strahlung wird in einem Detektor gemessen. Durch eine konfokale Blende (pinhole) erreicht nur Laserlicht aus einer extrem dünnen In-Fokus-Ebene den Detektor, so daß schrittweises Bewegen des Objekttischs eine tomographische Serie von Einzelbildern visualisiert. Gesunde kortikale Knochenproben des Unterkiefers (n = 20) wurden durchlichtmikroskopisch und im CLSM untersucht: Dabei wurden identische Probenareale an Dünnschliffen nach HE-Färbung visualisiert. Außerdem wurden eingebettete und frische Gewebeblöcke derselben Knochenproben im CLSM histotomographiert. Als Ergebnisse wurden gefunden: 1. Lichtmikroskopische Mikromorphologie kortikalen Knochens ist im CLSM valide visualisierbar. 2. Viele lichtmikroskopisch erst nach Spezialfärbungen darstellbare Strukturen (z.B. Osteozytenfortsätze) können im CLSM an Probenblöcken ohne Vorbereitung mikroskopiert werden. Hieraus können folgende Schlußfolgerungen gezogen werden: 1. Die zerstörungsfreie Histotomographie des CLSM unter der Probenoberfläche vermeidet mechanische Artefakte völlig. 2. Physikalisch-chemische Artefakte werden kontrollierbar, da auch frische Proben mikroskopiert werden können. 3. Die pseudo-dreidimensionale Darstellung erlaubt eine histologische Gewebeinterpretation, die makroskopischen Schichtbildverfahren (CT, MRT) vergleichbar ist.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100060050049
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 49
    Electronic Resource
    Electronic Resource
    Neuer Hydroxylapatitzement für die kraniofaciale Chirurgie (1998)
    Springer
    Mund-, Kiefer- und Gesichtschirurgie 2 (1998), S. S37 
    Details
    ISSN: 1434-3940
    Keywords: Schlüsselwörter Kalzium ; Phosphat ; Hydroxylapatit ; Zement ; Knochenersatz ; Augmentation ; Key words Calcium ; Phosphate ; Hydroxyapatite ; Cement ; Bone ; Augmentation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary A new stoechiometric mixture of 27% dicalcium-phosphate (DCPA) and 73% tetra-calcium-phosphate (TTCP) can be prepared with water intraoperatively to a paste that subsequently sets to a structurally stabile implant composed of hydroxyapatite (HA). Primary setting time is about 20 min; pH during setting ranges from 6.5 to 8.5. There is no relevant curing heat or expansion or contraction. Compressive strength is about 50 MPa, tensile strength about 8 MPa. Over a period of about 4 h in physiological milieu, the cement converts to hydroxyapatite. This product is no longer redissolvable in normal body fluid. This cement can be used for non-load-bearing applications especially in craniofacial bone surgery. Cranial defects due to tumour or trauma as well as deficits in the facial skeleton may be reconstructed using this new biomaterial. In nine of ten patients we used the hydroxyapatite cement successfully for reconstructions in the craniofacial area. Fluid control of the operation field and implant site is extremely important and sometimes difficult to achieve. Further applications could be all non-load-bearing augmentations such as filling of blocked paranasal sinuses, of dentoalveolar cysts and defects following dental apectomy or fixation of implanted hearing-aid electrodes. The perspectives for the hydroxyapatite cement include its application as a carrier for osteogenic protein preparations, especially because of its isothermic reaction and intrinsic osteoconductive characteristics.
    Notes: Zusammenfassung Ein neuer Kalziumphosphatzement besteht aus 73% Tetrakalziumphosphat und 27% Kalziumhydrogenphosphat. Er bindet bei Körpertemperaturen nach Zugabe von Wasser innerhalb von 20 min ab. Innerhalb von 4 h wird der Zement zu Hydroxylapatitkristallen umgesetzt und damit wasserunlöslich. Der Abbindeprozeß verläuft nahezu isotherm im pH-Bereich von 6,5–8,5 ohne Schrumpfung. Die Druckfestigkeit liegt im ausgehärteten Zustand oberhalb von 50 MPa, die Zugfestigkeit bei mehr als 8 Mpa. Der Zement ist für alle nicht lasttragenden Knochenaugmentationen und Knochenersatzanwendungen insbesondere am Gesichtsschädel geeignet. Bei 9 von 10 Patienten benutzten wir den Zement erfolgreich für Rekonstruktionen im kraniofazialen Bereich. Beim klinischen Einsatz muß besonders auf sorgfältige Trockenlegung des Operations- und Implantationsfelds geachtet werden. Weitere Anwendungsmöglichkeiten sind das Auffüllen von ausgeräumten und verblockten Schädelhöhlen, die Fixation von implantierten Hörelektroden in der Hals-Nasen-Ohren-Heilkunde sowie das Auffüllen von Zysten und Wurzelspitzenresektionsdefekten in der dentoalveolären Chirurgie. Besondere Perspektiven bietet der Hydroxylapatitzement wegen seiner isothermen Abbindereaktion und seiner intrinsischen osteokonduktiven Eigenschaften als Trägermaterial für osteogene Proteinkomplexe.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00014476
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 50
    Electronic Resource
    Electronic Resource
    Asymmetry of the internal connections of the striate cortex of the cat in the projection zone of the center of the field of vision (1998)
    Springer
    Neuroscience and behavioral physiology 28 (1998), S. 211-217 
    Details
    ISSN: 1573-899X
    Keywords: Cat ; striate cortex ; internal connections ; horseradish peroxidase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Studies were carried out on the organization of the internal connections of the striate cortex in cats in the projection zone of the center (0–5°) of the field of vision by microintophoretic application of horseradish peroxidase to electrophysiologically identified orientational columns. The area containing neurons showing retrograde labeling in most cases extended in the mediolateral direction. Labeled cells were located in the upper (II, III) and lower (V, VI) layers of the cortex, and the shapes and orientations of the areas containing labeled neurons in these layers coincided. Spatial asymmetry was detected in the distribution of labeled neurons relative to the orientational column studied. Labeled cells were located predominantly medial to the columns, regardless of the distance from the projection of the area centralis. Considering the visuotopical map of field 17, the asymmetry detected here provides evidence that neurons in orientational columns have more extensive connections with neurons of the peripheral part of the cortex. An asymmetrical distribution of “silent” zones around the receptive fields of neurons in orientational columns is suggested, and that these appear to receive influences from the periphery of the visual field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02461970
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 51
    Electronic Resource
    Electronic Resource
    Identifikation eines skelettierten Kleinkind-Schädels durch die molekularbiologische Untersuchung von Hirnresten (1998)
    Springer
    Rechtsmedizin 8 (1998), S. 109-111 
    Details
    ISSN: 1434-5196
    Keywords: Key words Identification ; Forensic osteology ; DNA typing ; PCR ; Brain ; Bone ; Schlüsselwörter Identifikation ; Forensische ; Osteologie ; DNA-Typisierung ; PCR ; Gehirn ; Knochen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Law
    Description / Table of Contents: Zusammenfassung Ein weitgehend skelettierter Kleinkind-Schädel konnte mittels forensisch-anthropologischer Befunderhebung klassifiziert und mittels erfolgreicher DNA-PCR-Typisierung am Hirnbrei, nicht jedoch am Schädelknochen identifiziert werden. Die vorgestellte Kasuistik belegt eindrücklich, daß eine sorgfältige forensisch-anthropologische Befunderhebung eine wesentliche Grundlage für die molekularbiologische Identifizierung an Skeletteilen bildet und daß auch an fortgeschritten fäulnisverändertem Gehirn bei feuchtem Lagerungsmilieu eine DNA-PCR-Typisierung erfolgreich sein kann.
    Notes: Abstract The skull of a small child, which was largely devoid of soft tissue, was classified according to forensic/anthropological findings and could be identified on the basis of DNA typing by PCR using residual brain tissue, but not bone. This case illustrates the fact that careful forensic/anthropological investigation is an important basis for molecular biological identification from skeletal remains and that DNA typing by PCR may even be possible on brain tissue that has been exposed to damp conditions and is an advanced state of decomposition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001940050041
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 52
    Electronic Resource
    Electronic Resource
    Synthesis, homopolymerization, and block copolymerization of N-ethyl-2-ethynyl-pyridinium trifluoromethanesulfonate with styrene and butadiene (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 703-712 
    Details
    ISSN: 0887-624X
    Keywords: synthesis ; homopolymerization ; block copolymerization ; N-ethyl-2-ethyl-pyridinium ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A novel acetylenic monomer 2-N-ethyl pyridinium trifluoromethane sulfonate (2EPyEtTf) was synthesized and polymerized. Diblock copolymers of 2EPyEtTf with styrene and with butadiene were prepared. Initiation of the polymerization by living anionic polystyryl--Li+ and polybutadienyl--Li+ (Scheme 1) resulted in polystyrene-block-poly(N-ethyl-2-ethynylpyridinium trifluoromethanesulfonate) (PS57PA8), and polybutadiene -block-poly(N-ethyl-2-ethynylpyridinium trifluoromethanesulfonate) (PB30PA8). These amphiphilic block molecules contain rigid, conjugated, and strongly hydrophilic polyacetylene chain fragments attached to hydrophobic polystyrene or flexible polybutadiene chain fragments. The structure of these copolymers was studied by FTIR, UV-visible, and NMR spectroscopy. GPC and viscometry were also used to obtain information on the molecular mass and the molecular mass distribution. Thermal behavior was investigated by means of TGA and DSC. Both block copolymers were shown to form stable monolayers at the air-water interface. The positively charged rigid polyacetylene portion of the copolymer is believed to be partially submerged, while the more flexible hydrophobic chains are forced out of the water. Multilayers of PB30PA8 deposited using the Langmuir-Blodgett technique were found to be less uniform than in the case of the previously reported polystyrene-block-poly(2EPyMeTf) (PS12PA4) copolymer (Balogh et al., Macromolecules, 29, 1996). Polycation-polyanion self-assembly deposition was also investigated, using polystyrenesulfonate (PSS) as polyanion. While PS57PA8/PSS layer-by-layer deposition was not uniform, it was found that PB30PA8/PSS gave homogenous and stable films on hydrophilic glass substrates. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 703-712, 1998
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 53
    Electronic Resource
    Electronic Resource
    Kinetics of the photoinitiated inverse microemulsion polymerization of 2-methacryloyl oxyethyl trimethyl ammonium chloride (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 737-748 
    Details
    ISSN: 0887-624X
    Keywords: inverse microemulsion polymerization ; MADQUAT ; nucleation ; photopolymerization ; molecular weights ; flocculants ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The polymerization of inverse microemulsions of 2-methacryloyl oxyethyl trimethyl ammonium chloride stabilized by a blend of nonionic emulsifiers (a sorbitan sesquioleate and a sorbitan monooleate) and initiated by UV light in the presence of Azobis(isobutyronitrile) (AIBN) was investigated. The effect of initiator concentration, light intensity, emulsifier concentration, and dispersed phase weight fraction on the polymerization rate (Rp), number of polymer particles (Np), and polymer molecular weight (Mw) was studied. The application of this process to tubular reactors is discussed. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 737-748, 1998
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 54
    Electronic Resource
    Electronic Resource
    Molecular weight distribution of crosslinked polymers produced in emulsion (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1127-1156 
    Details
    ISSN: 0887-624X
    Keywords: emulsion polymerization ; crosslinking and long-chain branching ; molecular weight distribution ; compartmentalization ; gel formation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A kinetic model for evaluating the chain length distribution of a branched polymer produced in emulsion was developed. Chain branching occurring through any intermolecular mechanism is considered, namely, crosslinking, chain transfer to polymer and propagation to terminal double bond. The model accounts for active chain compartmentalization and, when coupled to a model able to describe the evolution of the polymerization system, allows evaluation of the cumulative properties of the produced polymer both in the pregel and postgel phases. The numerical difficulties related to the description of a rather wide polymer chain population and of gel formation are overcome by using the ‘numerical fractionation’ technique. A parametric analysis of both instantaneous and cumulative properties is reported and discussed, with special attention to the role of radical compartmentalization in determining the molecular weight properties of a polymer produced in emulsion. Significant differences with the molecular weights computed using models developed for homogeneous (non compartmentalized) systems have been found. A comparison with the predictions of Flory's statistical theory is also reported in terms of gel point and gel weight fraction. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1127-1156, 1998
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 55
    Electronic Resource
    Electronic Resource
    Cationic copolymerization of cyclic ketene acetals: The effect of substituents on reactivity (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 861-871 
    Details
    ISSN: 0887-624X
    Keywords: 2-methylene-1,3-dioxane ; 4-methyl-2-methylene-1,3-dioxane ; 4,4,6-trimethyl-2-methylene-1,3-dioxane ; 2-methylene-1,3-dioxolane ; 4-methyl-2-methylene-1,3-dioxolane ; 4,5-dimethyl-2-methylene-1,3-dioxolane ; cationic copolymerization ; reactivity ratio ; relative reactivity ; ring-retained polymerization ; cyclic ketene acetals ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cationic copolymerizations of 4-methyl-2-methylene-1,3-dioxane, 2 (M1), with 2-methylene-1,3-dioxane, 1 (M2); of 4,4,6-trimethyl-2-methylene-1,3-dioxane, 3 (M1), with 2-methylene-1,3-dioxane, 1 (M2); of 4-methyl-2-methylene-1,3-dioxolane, 5 (M1), with 2-methylene-1,3-dioxolane, 4 (M2); and of 4,5-dimethyl-2-methylene-1,3-dioxolane, 6 (M1), with 2-methylene-1,3-dioxolane, 4 (M2) were conducted. The reactivity ratios for these four types of copolymerizations were r1 = 1.73 and r2 = 0.846; r1 = 2.26 and r2 = 0.310; r1 = 1.28 and r2 = 0.825; r1 = 2.23 and r2 = 0.515, respectively. The relative reactivities of these monomers towards cationic polymerization are: 3 〉 2 〉 1; and 6 〉 5 〉 4. With both five- and six-membered ring cyclic ketene acetals, the reactivity increased with increasing methyl substitution on the ring. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 861-871, 1998
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 56
    Electronic Resource
    Electronic Resource
    Enzymatic activity of trypsin adsorbed on temperature-sensitive composite polymer particles (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 883-888 
    Details
    ISSN: 0887-624X
    Keywords: temperature sensitive ; particle ; emulsion polymerization ; morphology ; adsorption ; enzyme ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two kinds of temperature-sensitive composite polymer particles were prepared by seeded emulsion copolymerizations of (dimethylamino)ethyl methacrylate and ethylene glycol dimethacrylate with 0.14 μm-sized polystyrene and 0.26 μm-sized poly(methylmethacrylate) seed particles. To evaluate the usefulness as a carrier for biomolecules, the enzymatic activities of trypsin adsorbed on these two composite polymer particles were measured at temperatures above and below each lower critical solution temperature (LCST). In both cases, adsorbed trypsin retained its enzymatic activity during repeated adsorption/desorption measurements. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 883-888, 1998
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 57
    Electronic Resource
    Electronic Resource
    Synthesis of (1→6)-2,5-anhydro-D-glucitol through cyclopolymerization of 3,4-di-O-allyl-1,2 : 5,6-dianhydro-D-mannitol and optical resolution ability of its derivative in HPLC (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 901-909 
    Details
    ISSN: 0887-624X
    Keywords: (1→6)-2,5-anhydro-D-glucitol ; HPLC ; optical resolution ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The cyclopolymerization of 3,4-di-O-allyl-1,2 : 5,6-dianhydro-D-mannitol (1) was carried out using BF3·OEt2 and t-BuOK. The polymer obtained by the polymerization with BF3·OEt2 mainly consisted of (1→6)-bonded 3,4-di-O-allyl-2,5-anhydro-D-glucitol as the five-membered constitutional repeating unit, though it contained a small amount of other cyclic repeating units. On the other hand, during the polymerization using t-BuOK, the stereoregular polymer (1→6)-linked 3,4-di-O-allyl-2,5-anhydro-D-glucitol (2) was synthesized via a regio- and stereoselective mechanism. Cleavage of the allyl ether linkage in polymer 2 occurred to produce the polymer consisting of only 2,5-anhydro-D-glucitol units, i.e., (1→6)-2,5-anhydro-D-glucitol (3). Chromatographic enantioseparation of chloroquine and tröger base has been performed on (3,5-dimethylphenyl)carbamate and 4-methylbenzoate derivatives of 3 as a chiral stationary phase for high-performance liquid chromatography. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 901-909, 1998
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 58
    Electronic Resource
    Electronic Resource
    Model structures of thermoplastic polyesters having regularly alternated aromatic and fluorinated segments (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 939-947 
    Details
    ISSN: 0887-624X
    Keywords: fluorine ; perfluoropolyether ; polyester ; segmented ; thermoplastic ; interfacial synthesis ; thermal transitions ; dynamic-mechanical properties ; chemical resistance ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Linear segmented polyesters containing soft perfluoropolyether (PFPE) and hard aromatic segments are obtained by an interfacial polycondensation reaction of an acyl chloride-ended fluorinated prepolymer with various aromatic diphenols in the presence of phase transfer catalysts (PTC) as accelerators. Experimental conditions for reaching high molecular weights are discussed. The calorimetric analysis (DSC) of all the polyesters synthesized shows a typical biphasic morphology, where a very low Tg (〈 -110°C) corresponding to the segregated PFPE moiety, is always accompanied by another Tg or a higher melting temperature, depending on the nature of the hard phase. Dynamic-mechanical analysis (DMA) has been carried out confirming the DSC results and suggesting diversified mechanical behaviors at the various temperatures in line with the amorphous or semicrystalline nature of the polymer. Chemical resistance was finally tested by dipping in several solvents and chemicals. The new polyesters show high contact angles, a moderate swelling in many organic solvents and excellent stability in aggressive hydrolytic environments. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 939-947, 1998
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 59
    Electronic Resource
    Electronic Resource
    Thermosensitive lactitol-based polyether polyol (LPEP) hydrogels (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 979-984 
    Details
    ISSN: 0887-624X
    Keywords: lactitol ; hydrogel ; polyether polyol ; PEO and PPO linkage ; swelling degree ; thermosensitivity ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of new thermosensitive polymer hydrogels were prepared by reacting acylated poly(ethylene glycol) bis(carboxymethyl) ether (PEGBCOCl) with lactitol-based polyether polyols (LPEP). The polyether polyols were generated from propoxylation of lactitol and have molecular weights ranging from 1337 to 4055 g/mol. The hydrogels absorb water up to 1000% of their dry weight and expel free water at temperatures at and above 30°C. The wide ranging swelling behavior and excellent thermosensitivity depend closely on the degree of crosslinking and the propylene oxide lengths in the polyols. Differential scanning calorimetry of the hydrogels showed two endotherms associated with the phase transitions of PO and EO segments in the hydrogel structures. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 979-984, 1998
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 60
    Electronic Resource
    Electronic Resource
    Kinetic and microstructure studies of poly(ethylene-co-p-methylstyrene) copolymers prepared by metallocene catalysts with constrained ligand geometry (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1017-1029 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper discusses the poly(ethylene-co-p-methylstyrene) copolymers prepared by metallocene catalysts, such as Et(Ind)2ZrCl2 and [C5Me4(SiMe2NtBu)]-TiCl2, with constrained ligand geometry. The copolymerization reaction was examined by comonomer reactivity (reactivity ratio and comonomer conversion versus time), copolymer microstructure (DSC and 13C-NMR analyses) and the comparisons between p-methylstyrene and other styrene-derivatives (styrene, o-methylstyrene and m-methylstyrene). The combined experimental results clearly show that p-methylstyrene performs distinctively better than styrene and its derivatives, due to the cationic coordination mechanism and spatially opened catalytic site in metallocene catalysts with constrained ligand geometry. A broad composition range of random poly(ethylene-co-p-methylstyrene)copolymers were prepared with narrow molecular weight and composition distributions. With the increase of p-methylstyrene concentration, poly(ethylene-co-p-ethylstyrene)copolymer shows systematical decrease of melting point and crystallinity and increase of glass transition temperature. At above 10 mol % of p-methylstyrene, the crystallinity of copolymer almost completely disappears. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1017-1029, 1998
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 61
    Electronic Resource
    Electronic Resource
    Synthesis and spinning of a thermotropic liquid crystal copolyester containing a semirigid cycloaliphatic spacer (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1473-1480 
    Details
    ISSN: 0887-624X
    Keywords: thermotropic polymers ; liquid crystalline polymers ; semirigid spacers ; melt spinning ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A thermotropic, liquid crystalline copolyester, based on 2-chlorohydroquinone, 1,4-cyclohexanedimethanol and terephthaloyl chloride, has been synthesized and melt spun. The cyclohexanedimethylene moiety acts as a semirigid spacer, introducing flexibility while preserving the thermotropic nature of the polymer. Melt-spun fibers were observed to have a high degree of molecular alignment owing to the nematic nature of the melt. Both polymer and fiber properties have been characterized. Characterization techniques used to this end include elemental analysis, hot-stage polarized light microscopy, scanning electron microscopy, dilute solution viscometry, Fourier transform infrared spectroscopy, nuclear magnetic resonance, differential scanning calorimetry, and thermogravimetric analysis. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1473-1480, 1998
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 62
    Electronic Resource
    Electronic Resource
    Synthesis and properties of copolymers from 2-hydroxyethyl methacrylate-linked nonsteroidal antiinflammatory agents with methacrylic acid (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1481-1490 
    Details
    ISSN: 0887-624X
    Keywords: ibuprofen ; ketoprofen ; naproxen ; copolymer reactivity ; thermal stability ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three nonsteroidal antiinflammatory drugs, 2-(4-isobutylphenyl)-propionic acid (ibuprofen), 2-(3-benzoylphenyl)-propionic acid (ketoprofen), and 2-(6-methoxy-2-naphthyl)-propionic acid (naproxen), were covalently linked with 2-hydroxyethyl methacrylate (HEMA). The drug-linked HEMA (M1) (ibuprofen-linked HEMA abbreviated as HI; ketoprofen-linked HEMA as HK, and naproxen-linked HEMA as HN), were respectively copolymerized with methacrylic acid (M2), MA, to obtain macromolecular prodrugs. The compositions of the copolymers were determined by means of a 1H-NMR spectroscopy and monomer reactivity ratios were estimated using the Kelen-Tüdös linear differential equation. The reactivity ratios are: r1 = 0.101 ± 0.012, r2 = 1.071 ± 0.065 for HI-MA; r1 = 0.344 ± 0.066, r2 = 0.966 ± 0.032 for HN-MA, and r1 = 0.650 ± 0.182, r2 = 1.032 ± 0.106 for HK-MA, respectively. The monomer reactivity toward to MA radical estimated from 1/r2 values is almost same for all three monomers (1/r2 ∼ 1). The glass transition temperatures of three drug-linked homopolymers go hand in hand with the steric hindrance of three drugs, i.e., ketoprofen 〉 naproxen ≫ ibuprofen calculated the minimum energy by computer molecular modeling. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1481-1490, 1998
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 63
    Electronic Resource
    Electronic Resource
    Liquid chromatography of macromolecules at the critical adsorption point. II. Role of column packing: Bare silica gel (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1363-1371 
    Details
    ISSN: 0887-624X
    Keywords: liquid chromatography ; column packing ; bare silica gel ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Liquid chromatography of macromolecules at the critical adsorption point (LC CAP) presents a potentially very powerful method for molecular characterization of complex polymers. However, LC CAP applicability is limited due to various experimental problems. The pore sizes and surface chemistry of the column packings belong to the most important weak points of the method. The LC CAP behavior of poly(methyl methacrylate)s was investigated using bare silica gels of 6, 12, and 100 nm pore sizes and with various amounts of surface silanols. Tetrahydrofuran as the adsorption suppressing liquid and toluene as the adsorption promoting liquid were mixed to form the “nearly critical” eluents. Both pore size and surface chemistry of silica were found to strongly influence the retentive characteristics of the system in the critical adsorption area. Macromolecules that were large enough to be excluded from the packing pores hardly followed the LC CAP rules: their retention volumes changed irregularly with the polymer molar mass and their recovery dropped sharply. The narrow pore silica gel-packed column governed the elution patterns of the whole column set composed of silica gels with different pore sizes. This makes the conventional LC CAP characterization of common polymers with broader molar mass distribution impractical and even not feasible. A hybrid column system was proposed containing narrow pore nonadsorptive column added in series to the meso- and macroporous LC CAP silica gels. This narrow pore column would allow separation of gas, impurities, and system peaks from the polymer peaks. The possible successive changes of the surface of silica gel, e.g., due to formation of silanols by hydrolysis or due to irreversible adsorption of some admixtures from the sample or eluent may make the LC CAP irrepeatable. Pronounced peak broadening was observed in the critical adsorption area and this effect increased strongly with the polymer molar mass. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1363-1371, 1998
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 64
    Electronic Resource
    Electronic Resource
    New polymer syntheses. XCVII. Hyperbranched LC-polyesters based on β-(4-hydroxyphenyl)propionic acid and 4-hydroxybenzoic acid (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1397-1405 
    Details
    ISSN: 0887-624X
    Keywords: hyperbranched polyesters ; nematic phase ; phloritic acid ; vectra ; melt rheology ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two classes of liquid crystalline hyperbranched copolyesters were prepared by the copolycondensation of silylated 3,5-bis(acetoxy)benzoic acid with mixtures of mesogenic difunctional monomers. The first class of LC-copolyesters was obtained from 1 : 1 mixtures (molar ratio) of silylated β-(4-acetoxyphenyl)propionic acid and silylated 4-acetoxybenzoic acid (poly(HPPA/HBA)). The second class of LC-copolyesters was obtained by additional copolycondensation of silylated 6-acetoxy-2-naphthoic acid. The hyperbranched copolyesters of this ternary system poly(HPPA/HBA/HNA) proved to be less crystalline in contrast to the binary system. In both classes of LC-copolyesters the degree of branching was varied via the feed ratio of 3,5-dihydroxybenzoic acid. A minimum segment length of 6 difunctional monomer units between the branching points is required to establish a nematic phase. However, a greater segment length is needed to obtain a homogeneous LC-phase. The poly(HPPA/HBA) copolyesters were also characterized by melt rheology. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1397-1405, 1998
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 65
    Electronic Resource
    Electronic Resource
    Polymerization of acrylates by atom transfer radical polymerization. Homopolymerization of 2-hydroxyethyl acrylate (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1417-1424 
    Details
    ISSN: 0887-624X
    Keywords: 2-hydroxyethyl acrylate ; poly(2-hydroxyethyl acrylate) ; atom transfer radical polymerization (ATRP) ; controlled free radical polymerization ; MALDI-MS ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The application of atom transfer radical polymerization (ATRP) to the homopolymerization of 2-hydroxyethyl acrylate, a functional monomer, is reported. The polymerizations exhibit first-order kinetics, and molecular weights increase linearly with conversion. Polydispersities remain low throughout the polymerization (Mw/Mn ≈ 1.2). Reactions were conducted in bulk and in 1 : 1 (by volume) aqueous solution; the latter demonstrates the resilience of ATRP to protic media. Analysis of poly(2-hydroxyethyl acrylate) by MALDI-MS and 1H-NMR shows Mn,exp to be much closer to Mn,th than those observed by SEC using polystyrene standards. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1417-1424, 1998
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 66
    Electronic Resource
    Electronic Resource
    Unbridged bivalent lanthanidocenes for isotactic and stereomultiblock polymerization of methyl methacrylate (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1599-1606 
    Details
    ISSN: 0887-624X
    Keywords: bivalent organolanthanides ; polymerization ; methyl methacrylate ; stereomultiblock polymer ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Bivalent organolanthanides with unbridged substituted indenyl or fluorenyl ligands (1-SiMe3Ind)2YTHF (I), (9-SiMe3Flu)2YTHF (II), were found to efficiently catalyze the stereoregular polymerization of methyl methacrylate. The microstructure of resultant polymers was shown to be dependent of a conformation that the ligands adopt at the polymerization temperature. The formation of isotactic rich PMMAs from complex II was proposed to be associated with the fluctuation of the 9-trimethylsilylfluorenyls around a C2 symmetric twisted-conformation. The formation of the multi(syndioPMMA-block-iso-PMMA) polymers from the mixture of rac- and meso-isomers of I was rationalized on the basis of competing conjugate addition and inversion of the metallocene conformation. Surprisingly, both rac- and meso-isomers of I were found to operate with similar activity and stereospecifity, although the stereospecific operation of the meso-form was not completely understandable. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1599-1606, 1998
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 67
    Electronic Resource
    Electronic Resource
    Novel hydrogen-transfer polymerization of vinyl monomer derived from p-toluenesulfonyl isocyanate and acrylamide (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1491-1494 
    Details
    ISSN: 0887-624X
    Keywords: sulfonyl isocyanate ; acrylamide ; hydrogen-transfer polymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 68
    Electronic Resource
    Electronic Resource
    p-Nitrophenol permeability and temperature characteristics of an acryloyl-L-proline methyl ester-based porous gel membrane (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1495-1500 
    Details
    ISSN: 0887-624X
    Keywords: acryloyl-L-proline methyl ester (A-ProOMe) ; methacryloyl-L-proline methyl ester (MA-ProOMe) ; porous gel membranes ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermoresponsive porous gel membranes were synthesized by a simultaneously occurring process consisting of radiation-induced polymerization and crosslinking in aqueous solutions at various concentrations of acryloyl-L-proline methyl ester(A-ProOMe) without a crosslinker. Permeation of p-nitrophenol (PNP) through a thermoresponsive porous gel membrane obtained at a monomer concentration of 80% (w/w) drastically reduced around 14°C, the lower critical solution temperature (LCST) of linear poly(A-ProOMe) in water, from 0.60 × 10-3 cm/min at 10°C to no permeation at 18°C, accompanied by changes in both size and shape of pores associated with gel shrinkage. Moreover, it was found that porous gel membranes with a porosity of approximately 60% had a greater PNP permeability constant through porous gel membranes with mutually connected pores obtained at a monomer concentration of 50% (w/w) than individually supported pores obtained at a monomer concentration of 70% (w/w). © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1495-1500, 1998
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 69
    Electronic Resource
    Electronic Resource
    Polymerization under a magnetic field. VI. Triplet dye-sensitized photopolymerization of acrylamide and methyl methacrylate (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1509-1513 
    Details
    ISSN: 0887-624X
    Keywords: methylene blue ; dye-sensitized photopolymerization ; magnetic field ; triplet state ; acrylamide ; methyl methacrylate ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methylene blue sensitized photopolymerization of acrylamide (AM) and methyl methacrylate (MMA) using triethanolamine or the sodium salt of EDTA as a reducing agent has been investigated under the influence of a magnetic field (0-7.3 kG). There was no effect of the magnetic field (MF) on the polymerization of AM and MMA in aqueous medium. However, in the water-methanol mixture (1 : 1) the yield of polymer decreases and the molecular weight increases in both cases under MF. This has been explained on the basis of the triplet mechanism. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1509-1513, 1998
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 70
    Electronic Resource
    Electronic Resource
    Porous monodisperse poly(divinylbenzene) microspheres by precipitation polymerization (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1543-1551 
    Details
    ISSN: 0887-624X
    Keywords: polymer microspheres ; monodisperse ; crosslinked ; porosity ; porogen ; precipitation polymerization ; divinylbenzene ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The precipitation polymerization of commercial divinylbenzene in acetonitrile containing up to 40 vol. % toluene or other cosolvents is shown to produce novel porous monodisperse poly(divinylbenzene) microspheres. These microspheres have diameters between 4 and 7 μm, total pore volumes of up to 0.52 cm3/g, and surface areas of up to 800 m2/g. As no surfactant nor stabilizer was used in the preparation of these particles, their surfaces are free of any such residues. The particles were slurry-packed into stainless steel columns for size exclusion chromatography evaluation, and the results show an exclusion limit at molecular weights of 500 g/mol. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1543-1551, 1998
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 71
    Electronic Resource
    Electronic Resource
    (Diisopropylamido) bis (methylcyclopentadienyl) lanthanides as single-component initiators for polymerization of methyl methacrylate (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1593-1597 
    Details
    ISSN: 0887-624X
    Keywords: MMA ; polymerization ; (diisopropylamido)bis(methylcyclopentadienyl)lanthanides ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It was first found that (diisopropylamido)bis(methylcyclopentadienyl)lanthanides (MeC5H4)2LnN(i-Pr)2(THF) (Ln = Yb (1), Er (2), Y (3)) exhibit extremely high catalytic activity in the polymerization of methyl methacrylate. The reactions can be carried out over a quite broad range of polymerization temperatures from -78 to 40°C. The catalytic activity of the complexes increases with an increase of ionic radii of the metal elements, i.e. Y 〉 Er 〉 Yb. The results of GPC (gel permeation chromatography) indicate that the number-average molecular weights (Mn) of polymers obtained exceed 100 × 103 and the molecular weight distribution (Mw/Mn) becomes broad with the increase of temperature. Furthermore highly syndiotactic PMMA (87.7%) can be obtained by lowering the reaction temperature to -78°C. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1593-1597, 1998
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 72
    Electronic Resource
    Electronic Resource
    Preparation and properties of poly(styrene-co-maleic anhydride)/silica hybrid materials by the in situ sol-gel process (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1607-1613 
    Details
    ISSN: 0887-624X
    Keywords: sol-gel ; hybrid material ; poly(styrene-co-maleic anhydride) ; tetraethoxysilane ; (3-aminopropyl)triethoxysilane ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Poly(styrene-co-maleic anhydride)/silica hybrid material has been successfully prepared from styrene-maleic anhydride copolymer and tetraethoxysilane (TEOS) in the presence of a coupling agent (3-aminopropyl)triethoxysilane (APTES) by an in situ sol-gel process. It was observed that the gel time of sol-gel solution was dramatically influenced by the amount of APTES. The hybrid material exhibits optical transparency almost as good as both silica gel and the copolymer. The covalent bonds between organic and inorganic phases were introduced by the aminolysis reaction of the amino group with maleic anhydride units of copolymer to form a copolymer bearing trimethoxysilyl groups, which undergo hydrolytic polycondensation with TEOS. The differential scanning calorimetry (DSC) showed that the glass transition temperature of the hybrid materials increases with increasing of SiO2 composition. Photographs of scanning electron microscopy (SEM) and atomic force microscopy (AFM) inferred that the size of the inorganic particles in the hybrid materials was less than 20 nm. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1607-1613, 1998
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 73
    Electronic Resource
    Electronic Resource
    Influence of plasma treatment on the molar mass of poly(ethylene terephthalate) investigated by different chromatographic and spectroscopic methods (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1639-1648 
    Details
    ISSN: 0887-624X
    Keywords: poly(ethylene terephthalate) (PET) ; plasma ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The influence of different types of low and atmospheric pressure plasma on poly(ethylene terephthalate) (PET) has been studied in terms of changes in molar mass and molar mass distribution. Apart from a variation of plasma gases (oxygen, helium) different types of plasma (microwave, radio frequency, corona discharge) were used for the plasma surface modification. The changes in molar mass and types of functional end groups of lower molar mass products were investigated by means of matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOFMS), whereas the high-molar mass fraction was analyzed by means of size-exclusion chromatography (SEC). The formation of crosslinked products during exposure to a helium plasma, which emits preponderately energy-rich and intense ultraviolet radiation, was proved by means of thermal field-flow fractionation (ThFFF). This method combined with a multiangle laser light scattering (MALLS) detector allows detection of weakly crosslinked polymers and microgels. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1639-1648, 1998
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 74
    Electronic Resource
    Electronic Resource
    Synthesis and properties of poly(ether imide)s derived from 2,6-bis(3,4-dicarboxyphenoxy)naphthalene dianhydride and aromatic diamines (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1657-1665 
    Details
    ISSN: 0887-624X
    Keywords: 2,6-bis(3,4-dicarboxyphenoxy)naphthalene dianhydride ; poly(ether imide)s ; thermal behavior ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new naphthalene unit-containing bis(ether anhydride), 2,6-bis(3,4-dicarboxyphenoxy)naphthalene dianhydride, was synthesized in three steps starting from the nucleophilic nitrodisplacement reaction of 2,6-dihydroxynaphthalene and 4-nitrophthalonitrile in N,N-dimethylformamide (DMF) solution in the presence of potassium carbonate, followed by alkaline hydrolysis of the intermediate bis(ether dinitrile) and subsequent dehydration of the resulting bis(ether diacid). High-molar-mass aromatic poly(ether imide)s were prepared using a conventional two-step polymerization process from the bis(ether anhydride) and various aromatic diamines. The intermediate poly(ether amic acid)s had inherent viscosities of 0.65-2.03 dL/g. The films of poly(ether imide)s derived from two rigid diamines, i.e. p-phenylenediamine and benzidine, crystallized during the thermal imidization process. The other poly(ether imide)s belonged to amorphous materials and could be fabricated into transparent, flexible, and tough films. These aromatic poly(ether imide) films had yield strengths of 104-131 MPa, tensile strengths of 102-153 MPa, elongation to break of 8-87%, and initial moduli of 1.6-3.2 GPa. The glass transition temperatures (Tg's) of poly(ether imide)s were recorded in the range of 220-277°C depending on the nature of the diamine moiety. All polymers were stable up to 500°C, with 10% weight loss being recorded above 550°C in both air and nitrogen atmospheres. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1657-1665, 1998
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 75
    Electronic Resource
    Electronic Resource
    A simple method for the anionic polymerization of α-carbonyl acids in water (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1683-1683 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 76
    Electronic Resource
    Electronic Resource
    Novel aromatic polyhydrazides and poly(amide-hydrazide)s based on “multiring” flexible dicarboxylic acids (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1847-1854 
    Details
    ISSN: 0887-624X
    Keywords: polyhydrazides ; poly-1,3,4-oxadiazoles ; thermal behavior ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two flexible dicarboxylic acid monomers, 4,4′-[isopropylidenebis(1,4-phenylene)dioxy]dibenzoic acid (1) and 4,4′-[hexafluoroisopropylidenebis(1,4-phenylene)-dioxy]dibenzoic acid (3), were synthesized from readily available compounds in two steps in high yields. High molecular-weight polyhydrazides and poly(amide-hydra-zide)s were directly prepared from dicarboxylic acids 1 and 3 with terephthalic dihydrazide (5), isophthalic dihydrazide (6), and p-aminobenzhydrazide (7) by the phosphorylation reaction by means of diphenyl phosphite (DPP) and pyridine in N-methyl-2-pyrrolidone (NMP)/LiCl, or prepared from the diacyl chlorides of 1 and 3 with the hydrazide monomers 5-7 by the low-temperature solution polycondensation in NMP/LiCl. Less favorable results were obtained when using triphenyl phosphite (TPP) instead of DPP in the direct polycondensation reactions. Except for those derived from terephthalic dihydrazide, the resulting polyhydrazides and poly(amide-hydrazide)s could be cast into colorless, flexible, and tough films with good tensile strengths. All the hydrazide polymers and copolymers are amorphous in nature and are readily soluble in various polar solvents such as NMP and dimethyl sulfoxide (DMSO). Their Tgs were recorded in the range of 162-198°C and could be thermally cyclodehydrated into the corresponding polyoxadiazoles and poly(amide-oxadiazole)s approximately in the region of 300-380°C, as evidenced by the DSC thermograms. The oxadiazole polymers and copolymers showed a dramatically decreased solubility and higher Tg when compared to their respective hydrazide prepolymers. They exhibited Tgs of 190-216°C and were stable up to 450°C in air or nitrogen. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1847-1854, 1998
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 77
    Electronic Resource
    Electronic Resource
    Novel polyisobutylene/poly(dimethylsiloxane) bicomponent networks. I. Synthesis and characterization (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1891-1899 
    Details
    ISSN: 0887-624X
    Keywords: polyisobutylene ; poly(dimethylsiloxane) ; hydrosilation ; bicomponent networks ; molecular weight between crosslinks ; network functionality ; sol fraction ; extractables ; model networks ; end-linking ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of novel polyisobutylene (PIB)/poly(dimethylsiloxane) (PDMS) bicomponent networks is described. The synthesis strategy (see Figure 1) was to prepare well-defined and -characterized allyl-tritelechelic polyisobutylenes [φ(PIB - C - C=C)3] and SiH-ditelechelic poly(dimethylsiloxanes) (HSi-PDMS-SiH) and then crosslink these moieties by hydrosilation. The φ(PIB - C - C=C)3 was prepared by living isobutylene polymerization followed by end-quenching with allyltrimethylsilane, whereas the HSi-PDMS-SiH was obtained by equilibrium polymerization of octamethylcyclotetrasiloxane and tetramethyldisiloxane. The detailed structures of the starting polymers were characterized by GPC and 1H-NMR spectroscopy. A series of PIB/PDMS bicomponent networks of varying compositions and average molecular weights between crosslinks (Mc) of ∼ 20,000 g/mol were assembled. Optimum crosslinking conditions were defined in terms of H2PtCl6 catalyst concentration, nature of solvent, time, temperature, and stoichiometry of ∼ CH2CH=CH2/∼SiH groups, allowing for the convenient synthesis of well-defined model bicomponent networks. Swelling studies and elemental analysis confirm the correctness of the synthetic strategy. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1891-1899, 1998
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 78
    Electronic Resource
    Electronic Resource
    Novel polyisobutylene/poly(dimethylsiloxane) bicomponent networks. II. Network structure and property characterization (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1901-1910 
    Details
    ISSN: 0887-624X
    Keywords: polyisobutylene ; poly(dimethylsiloxane) ; bicomponent networks ; network structure ; molecular weight between crosslinks ; network properties ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The first part of this series concerned the synthesis of novel polyisobutylene (PIB)/poly(dimethylsiloxane) (PDMS) bicomponent networks; the present paper concerns the structure and property characterization of a series of bicomponent networks of varying compositions (PIB wt %/PDMS wt % = 92/8, 70/30, 50/50, 35/65) having average molecular weights between crosslinks (Mc) of ˜ 20,000 g/mol. According to network structure analysis by uniaxial equilibrium stress-strain measurements, the experimental Mc's are in excellent agreement with theoretical values. Hydrosilation end-linking efficiency was quantitated by the amount of sol and functional group analysis by 1H-NMR spectroscopy. NMR evidence indicates double-bond isomerization during hydrosilation. Network compositions by elemental analysis together with the low sol fractions indicate efficient crosslinking. These data suggest highly efficient network formation and well-defined bicomponent network structures. While PIB and PDMS showed Tg's at -72 and -124°C, respectively, the bicomponent network did not exhibit clearly discernible phase transitions. The heat stability of bicomponent networks increased slightly with increasing PDMS content showing initial (10%) degradation temperatures at ˜ 380°C in nitrogen and ˜ 320°C in air. Tensile strengths and elongations were dependent on composition and varied in the 0.6-3.8 MPa and 600-1100% ranges, respectively. The swelling behavior was not much affected by composition. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1901-1910, 1998
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 79
    Electronic Resource
    Electronic Resource
    Copolymerization of carbon monoxide and norbornene derivatives with ester groups by palladium catalyst (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1785-1790 
    Details
    ISSN: 0887-624X
    Keywords: carbon monoxide ; norbornene ester ; glass transition temperature ; palladium catalyst ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this article we will discuss the synthesis of the new copolymers of norbornene derivatives with an ester group and carbon monoxide, using Pd(CH3CN)4(BF4)2 as a catalyst and 2,2′-bipyridine as a ligand in nitromethane/methanol at 60°C. Elementary analysis, infrared spectra, and NMR spectra indicated that copolymers contain ketone, ester, and bicyclic structures. Methanol functions as the coinitiator and chain transfer agent in copolymerization. A decrease in the molar ratio of [CH3OH]/[Pd] caused an increase in molecular weight and a decrease in yield of the copolymer. The number-average molecular weight of copolymers (Mn) ranged from 3800 to 5300, and the glass transition temperature (Tg) ranged from -32 to 117°C. Thermal analysis revealed that both T10%d and Tmaxd exceeded 180 and 230°C, respectively. Linear long-chain substituents such as n-C11H23C(O)—O—CH2— drastically reduced Tg to a value of -32°C. In general, copolymers having a longer linear side-chain substituents of ester on norbornene have a more desirable solubility. Moreover, X-ray diffraction demonstrated that the degree of crystallinity decreases with an increasing length of side chain substituents. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1785-1790, 1998
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 80
    Electronic Resource
    Electronic Resource
    LC-polyimides XXXIV. Noncrystalline thermotropic copoly(ester-imide)s based on PET (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1813-1820 
    Details
    ISSN: 0887-624X
    Keywords: poly(ester-imide)s ; poly(ethylene terephthalate) ; transesterification, nematic phase ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four series of copoly(ester-imide)s (co-PEIs) were prepared by transesterification of poly(ethylene terephthalate), PET, with N-(4-carboxyphenyl)trimellitimide and an acetylated diphenol. Methylhydroquinone, tert. butylhydroquinone, phenylhydroquinone, and 2,7-dihydroxynaphthalene were used as diphenols. The chemical structures of these co-PEIs were characterized by chemical analyses, 1H-, and 13C-NMR spectra. A low degree of crystallinity was observed when the PET content was above 85% mol %. Between 60 and 80 mol % PET all co-PEIs are biphasic, whereas below 60 mol % the co-PEIs form a homogeneous nematic melt and below the glass transition temperature (Tg) a nematic glass. The Tgs vary continously with the molar composition but the mechanical properties drop sharply when the nematic phase changes to an isotropic one. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1813-1820, 1998
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 81
    Electronic Resource
    Electronic Resource
    Morphology and grafting of oxazoline-functional polymer particles with various carboxylic acids (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1821-1827 
    Details
    ISSN: 0887-624X
    Keywords: morphology ; grafting ; oxazoline-functionalized polymer particles ; carbolic acids ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Oxazoline-functionalized, crosslinked PMMA-particles, prepared by free radical nonaqueous dispersion polymerization, were grafted with n-decanoic acid and carboxylic acid-terminated polystyrene. Oxazoline groups, separated by an alkylspacer from the PMMA backbone, showed enhanced mobility with respect to the backbone, as evaluated by solid-state NMR spectroscopy using a dipolar filter. As a function of molecular mass of the carboxylic acid, the oxazoline conversion varied from 70 mol % for n-decanoic acid to 1% for monocarboxylate-terminated polystyrene CT-PS with Mn: 15,900 g/mol. Morphological studies, performed by TEM, showed that reaction with acid terminated polystyrene results exclusively in interfacial grafting at the particle surface. At low grafting levels a raspberry-like morphology was obtained, whereas grafting levels exceeding 14 wt % CT-PS resulted in core-shell morphology. Core-shell morphology was also verified by static light scattering using toluene solvent, which is isorefractive to the PMMA core. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1821-1827, 1998
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 82
    Electronic Resource
    Electronic Resource
    Aminolysis kinetics of model and polymer-bound anhydride moieties in low- and high-viscosity media (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1573-1582 
    Details
    ISSN: 0887-624X
    Keywords: amic acid ; secondary amine ; maleic anhydride ; melt reaction kinetics ; model compounds ; polymer-bound functional groups ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This study examines the legitimacy of using the reaction kinetics of low molecular weight model compounds in solution to predict the chemical kinetics of polymer-bound species in a homogeneous melt. The reaction under study takes place between an aliphatic secondary amine, diisooctadecylamine (DiOA), and a 5-membered anhydride ring, saturated maleic anhydride (MA), forming an amic acid product. The MA species was present as a pendant graft on either a model compound, dodecane-g-(maleic anhydride) (dodecane-g-MA), or a polymer chain, linear low-density polyethylene-g-(maleic anhydride) (LLDPE-g-MA). Pseudo-second-order kinetics of the anhydride consumption are followed by infrared spectroscopy, either in situ in dodecane solution or by scanning frozen film samples taken from a linear low-density polyethylene melt. It was found that the LLDPE-g-MA/DiOA system reacted at a slightly slower rate than the dodecane-g-MA/DiOA system in the low-viscosity solution at 140°C. In the melt, the dodecane-g-MA/DiOA system experienced a small decrease in the overall reaction rate compared to the same reaction carried out in dodecane. However, the LLDPE-g-MA/DiOA system underwent a 65% decrease in the observed second-order rate constant on going from a solution to the melt. To explain these phenomena, the effects of diffusion, miscibility, and chain entanglements in the melt are examined here. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1573-1582, 1998
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 83
    Electronic Resource
    Electronic Resource
    New polymer syntheses. XC. A-B-A triblock copolymers with hyperbranched polyester A-blocks (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 31-38 
    Details
    ISSN: 0887-624X
    Keywords: triblock copolymers ; polycondensations ; telechelic character ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Telechelic oligo(ether-ketone)s containing two trimethylsiloxy end groups and one methyl group per repeating unit were prepared by polycondensation of 4-fluoro-2′-methyl-4′-(trimethylsiloxy)benzophenone. The telechelic character was achieved by cocondensation of a small amount of silylated bisphenol-P. The end groups of the silylated oligo(ether-ketone)s were acetylated by means of acetyl chloride. On the basis of 1H-NMR end group analyses two samples of α,ω-bis(acetoxy) oligo(ether-ketone)s with DP = 14 and DP ∼ 28 were obtained. These oligo(ether-ketone)s and a 70 or 140 fold molar amount of silylated 3,5-bis(acetoxy)benzoic acid were polycondensed at 270°C in bulk. The resulting A-B-A triblock copolymers were fractionated by dissolution in tetrahydrofuran. In three out of four experiments a small fraction of precipitated material rich in oligo(ether-ketone) was isolated. The purified triblock copolymers were characterized by inherent viscosities and NMR spectra. For those samples containing the long oligo(ether-ketone) block a low degree of crystallinity was observed after annealing. Four additional polycondensations were conducted with an initial reaction temperature of 290°C. In this way a completely soluble and amorphous triblock copolymer was obtained. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 31-38, 1998
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 84
    Electronic Resource
    Electronic Resource
    Liquid crystalline epoxy resins by polyaddition of diglycidyl ether of 4,4′-dihydroxybiphenyl and difunctional aromatic compounds (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 21-29 
    Details
    ISSN: 0887-624X
    Keywords: liquid crystalline polymers ; epoxy resins ; thermotropic ; polymer chain extension ; catalytic polyaddition ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This work is a continuation of the authors' earlier investigations of liquid crystalline epoxy resins prepared from diglycidyl ether of 4,4′-dihydroxybiphenyl (DGE-DHBP), which was used as a mesogenic agent, and aliphatic dicarboxylic compounds, which were used as flexible spacers. In this paper, the synthesis and characterization of liquid crystalline epoxy resins, prepared from DGE-DHBP and difunctional aromatic compounds are described. Three series of liquid crystalline epoxy resins were prepared by chain extension of DGE-DHBP with isomeric hydroxybenzoic and benzenedicarboxylic acids as well as diphenols. An isophthalic-terminated polyether was applied to decrease the temperature of phase transitions. The syntheses were carried out by catalytic polyaddition in the melt. Triphenylphosphine was applied as the catalyst. The resulting epoxy resins were investigated by DSC, polarizing microscope as well as by X-ray and IR spectroscopy. The phase transition temperatures and the type of mesophase of the resulting products depend on the character of the functional groups in the chain extender and on the position of the functional groups in the aromatic ring. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 21-29, 1998
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 85
    Electronic Resource
    Electronic Resource
    Preparation and properties of new soluble aromatic polyimides from 2,2′-bis(3,4-dicarboxyphenoxy)biphenyl dianhydride and aromatic diamines (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2021-2027 
    Details
    ISSN: 0887-624X
    Keywords: 2,2′-bis(3,4-dicarboxyphenoxy)biphenyl dianhydride ; aromatic polyimides ; solubility ; thermal behavior ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new aromatic tetracarboxylic dianhydride having a crank and twisted noncoplannar structure, 2,2′-bis(3,4-dicarboxyphenoxy)biphenyl dianhydride, was synthesized by the reaction of 4-nitrophthalonitrile with biphenyl-2,2′-diol, followed by hydrolysis and cyclodehydration. The biphenyl-2,2′-diyl-containing aromatic polyimides having inherent viscosities up to 0.66 dL/g were obtained by the conventional two-step procedure starting from the dianhydride monomer and various aromatic diamines. Most of the polyimides were readily soluble in amide-type solvents such as N,N-dimethylacetamide and N-methyl-2-pyrrolidone. The aromatic polyimides had glass transition temperatures in the range of 205-242°C, and began to lose weight around 415°C, with 10% weight loss being recorded at about 500°C in air. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2021-2027, 1998
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 86
    Electronic Resource
    Electronic Resource
    Studies of lipase-catalyzed polyesterification of an unactivated diacid/diol system (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2069-2079 
    Details
    ISSN: 0887-624X
    Keywords: Candida antarctica lipase ; Novozym 435® ; polyester ; enzymatic polymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Preliminary enzymatic polymerization studies in the simple stoichiometric adipic acid/butane-1,4-diol system using lipase B from Candida antarctica, immobilized as Novozym 435®, suggest that in solvent-free conditions a step-growth mechanism operates involving the sequential addition of an AB synthon by esterification mode only. Conversely, in toluene as solvent there is a change to the more facile transesterification mode in line with the conventional polyesterification procedure, pointing to a change in specificity of the lipase. Evidence is drawn from qualitative studies using a series of synthetic intermediates, enabling authentication of product mixtures together with an indication of the comparative reactivity of species along the proposed reaction pathway. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2069-2080, 1998
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 87
    Electronic Resource
    Electronic Resource
    Mechanical properties of blends of PAMAM dendrimers with poly(vinyl chloride) and poly(vinyl acetate) (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2111-2117 
    Details
    ISSN: 0887-624X
    Keywords: dendritic polymer ; blends ; coatings ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hybrid blends of poly(amidoamine) PAMAM dendrimers with two linear high polymers, poly(vinyl chloride), PVC, and poly(vinyl acetate), PVAc, are reported. The interaction between the blend components was studied using dynamic mechanical analysis, xenon nuclear magnetic resonance (NMR) spectroscopy, and tensile property measurements. The data suggest a much higher degree of interaction between components of PVAc-containing blends compared to those containing PVC. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2111-2117, 1998
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 88
    Electronic Resource
    Electronic Resource
    Side chain liquid crystal polyurethanes with azobenzene mesogenic moieties: Influence of spacer length on hydrogen bonding at different temperatures (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2135-2146 
    Details
    ISSN: 0887-624X
    Keywords: SCLC polyurethanes ; azobenzene mesogenic group ; alkyl spacer ; bilayer smectic phases ; hydrogen bonding ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of side chain liquid crystal polyurethanes (CnCNPs), in which the spacer length was varied from 2 to 12 methylene units, were synthesized by the addition polymerization of α-[bis(2-hydroxyethyl)amino]-ω-(4-cyanoazobenzene-4′-oxy)alkanes (CnCN-diols) with hexamethylene diisocyanate. The liquid crystalline properties of CnCNPs were characterized by means of differential scanning calorimetry, polarizing optical microscopy, and X-ray diffraction. Polyurethanes with spacer length 4 or higher exhibited mesomophic properties. C4CNP and C5CNP exhibited an enantiotropic nematic mesophase, while C6-C12CNPs exhibited enantiotropic bilayer smectic mesophases. CnCNPs have a high tendency to crystallize; crystallization is kinetically controlled. Polyurethane's backbone crystallization is closely related to hydrogen bonding. To establish the role of hydrogen bonding in mesophase formation as well as crystallization, Fourier transform infrared spectroscopy studies of CnCNPs were carried out at different temperatures focusing on H-bonds between the N—H and C=O groups of the urethane backbone. With increasing temperature, C=O and N—H stretching bands were evenly shifted to higher wavenumbers, with two exceptions (C4CNP and C5CNP) discussed in detail in the text. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2135-2146, 1998
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 89
    Electronic Resource
    Electronic Resource
    Initiation mechanisms in free radical polymerization: Competitive reaction of cyanoisopropyl radicals with styrene and acrylonitrile (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2169-2176 
    Details
    ISSN: 0887-624X
    Keywords: free radical ; initiation ; styrene ; acrylonitrile ; copolymerization ; nitroxide trapping ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The competitive reactions of cyanoisopropyl radicals with the mixed monomers styrene and acrylonitrile have been investigated using the nitroxide radical trapping technique. When the trap concentration is kept low, second, third, and even fourth generation (in terms of successive monomer addition) carbon radicals have been observed as trapped products. The ratio of rate constants for the addition of styrene and acrylonitrile to cyanoisopropyl radicals is 2.7 at 75°C and 5.3 at 105°C. These values are compared with the ratios for reactions of these two monomers with a number of other radicals and discussed in terms of the polarities of the radicals and monomers. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2169-2176, 1998
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 90
    Electronic Resource
    Electronic Resource
    Synthesis and characterization of new poly(amide-imide)s from 1,4-bis(4-trimellitimidophenoxy)-2-tert-butylbenzene with various diamines (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2301-2307 
    Details
    ISSN: 0887-624X
    Keywords: 1,4-bis(4-trimellitimidophenoxy)-2-tert-butylbenzene (BTTB) ; direct polycondensation ; poly(amide-imide)s ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New poly(amide-imide)s were prepared from a diimide-dicarboxylic acid, 1,4-bis(4-trimellitimidophenoxy)-2-tert-butylbenzene (BTTB), with various diamines by the direct polycondensation in N-methyl-2-pyrrolidinone (NMP) using triphenyl phosphite and pyridine as condensing agents. The new diimide-dicarboxylic acid BTTB containing an ether linkage and tert-butyl substituent was synthesized by the condensation reaction of 1,4-bis(4-aminophenoxy)-2-tert-butylbenzene with trimellitic anhydride. All the polymers were obtained in quantitative yields with inherent viscosities of 0.62-1.06 dL g-1. The polymers were amorphous, and most of them were readily soluble in aprotic polar solvents such as NMP, N,N-dimethylacetamide (DMAc), and N,N-dimethylformamide (DMF), as well as in less polar solvents such as dimethyl sulfoxide (DMSO), m-cresol, pyridine, and γ-butyrolactone, and also even in tetrahydrofuran. The glass transition temperatures of the polymers were determined by DSC method, and they were in the range of 238-279°C. These polymers were stable up to 408-449°C in air and 451-483°C in nitrogen and lose 10% weight in the range of 479-525°C in air and 480-528°C in nitrogen atmosphere. The polymer films had a tensile strength range of 71-115 MPa, an elongation at break range of 4-14%, and a tensile modulus range of 2.3-3.1 GPa. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2301-2307, 1998
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 91
    Electronic Resource
    Electronic Resource
    Synthesis and surface characterization of heparin-immobilized polyetherurethanes (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2331-2338 
    Details
    ISSN: 0887-624X
    Keywords: poly(ether urethane) ; surface modification ; heparin immobilization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Novel poly(ether urethanes) containing diester groups in the side chains (PU) were synthesized from 4,4′-diphenylmethyl diisocyanate, polytetramethylene glycol, and diethyl bis(hydroxymethyl)malonate as a chain extender. The surface modification of the PU film was carried out by a hydrolysis reaction, poly(ethylene oxide) (PEO) grafting, and heparin immobilization, and the surface-modified PUs were then characterized by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, electron spectroscopy for chemical analysis (ESCA), and a contact angle goniometer. The concentration of carboxylic acid groups introduced on the PU surfaces as determined by the rhodamine interaction method was 61 nmol/cm2 when treated with 4N NaOH/methanol (1 : 2 v/v) for 30 min and subsequently with a citric acid-methanolic aqueous solution. The amounts of heparin coupled to the carboxyl groups on the PU surfaces and to the terminus amino groups on the PU-PEO were 0.92 and 0.84 μ g/cm2, respectively. There was almost no heparin released from the immobilized surface of a physiological solution for 100 h, thereby indicating the strong stability of immobilized heparin. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2331-2338, 1998
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 92
    Electronic Resource
    Electronic Resource
    Synthesis and characterization of new aromatic polyesters and a polyether derived from 2,2-bis(4-hydroxyphenyl)-1,2-diphenylethanone (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2229-2235 
    Details
    ISSN: 0887-624X
    Keywords: polyarylates ; aromatic polyether ; 2,2-bis(4-hydroxyphenyl)-1,2-diphenylethanone ; solubility ; thermal behavior ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New polyarylates having benzopinacolone units were synthesized from 2,2-bis(4-hydroxyphenyl)-1,2-diphenylethanone and aromatic dicarboxylic acid chlorides. The polymers having an inherent viscosity of 0.71-0.94 dL/g were obtained by the two-phase method using toluene as an organic solvent. The polymers were easily soluble in various organic solvents and had high glass transition temperatures in the range of 200-240°C. An aromatic polyether having benzopinacolone unit was also prepared. However, its inherent viscosity was low because of the occurrence of a side reaction. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2229-2235, 1998
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 93
    Electronic Resource
    Electronic Resource
    Preparation of plasma-grafted polymer membranes and their morphology and pervaporation properties toward benzene/cyclohexane mixtures (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2247-2259 
    Details
    ISSN: 0887-624X
    Keywords: pervaporation ; plasma graft polymerization ; membrane ; glycidyl methacrylate ; morphology ; porous polyethylene ; benzene/cyclohexane separation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Composite membranes were prepared by plasma-induced graft polymerization of vinyl monomers onto porous substrates of high density polyethylene, and the relationship between the polymerization conditions and morphological structure and pervaporation performance toward benzene/cyclohexane mixtures was investigated in detail. The morphological structures of the plasma-grafted membranes depended on the monomer reactivity, plasma treatment manner, and graft polymerization conditions. Pervaporation properties were closely related to the graft monomers and the morphological structures. The poly(glycidyl methacrylate)-grafted membranes prepared by homogeneous both sides plasma treatment and under mild polymerization conditions showed the highest pervaporation performance with a permeation flux of 0.3 kg/(m2 h) and separation factor of 22 at 60 wt % benzene and 70°C. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2247-2259, 1998
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 94
    Electronic Resource
    Electronic Resource
    Polymerization of olefins with a novel dinuclear ansa-zirconocene catalyst having a biphenyl bridge (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2269-2274 
    Details
    ISSN: 0887-624X
    Keywords: dinuclear ansa-zirconocene catalyst ; diastereomers ; biphenyl and phenyl ligands ; polymerization of ethene and propene ; copolymerization of ethene and 1-octene ; thermal stability of active species ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Both the rac- and meso-dinuclear ansa-zirconocene catalysts (μ-C12H8{[SiPh(Ind)2]ZrCl2}2) were prepared by a coupling reaction between 2 equiv of diindenylphenylchlorosilane (rac- and meso-isomers) and 1 equiv of p-dilithiobiphenyl in diethyl ether at -80°C, followed by a successive reaction with ZrCl4 · 2THF in THF at -78°C. Polymerizations of ethene and propene were conducted in a 1 dm3 high-pressure glass reactor equipped with a mechanical stirrer at 60, 80, 100, 120, and 150°C using methylalumoxane (MAO) as cocatalyst and toluene or decahydronaphthalene as the solvent. Copolymerization of ethene and 1-octene was also checked in brief. For ethene polymerization, the meso-catalyst was found to be more active, which displayed an extremely high activity to give linear polyethene with a high molecular weight and a narrow molar mass distribution (MMD). The apparent activity increased monotonously with rising polymerization temperature from 60°C up to 150°C, indicating that the active species are stable even at a high temperature. On the other hand, both the rac- and meso-catalysts showed very poor activities for propene polymerization. However, copolymerization of ethene and 1-octene proceeded at a high speed. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2269-2274, 1998
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 95
    Electronic Resource
    Electronic Resource
    Spectral, thermal, and electrical properties of poly(o- and m-toluidine)-polystyrene blends prepared by emulsion pathway (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2291-2299 
    Details
    ISSN: 0887-624X
    Keywords: poly(o-toluidine) ; (POT) ; poly(m-toluidine) ; (PMT) ; polystyrene (PSt) ; blends ; emulsion pathway ; spectroscopy ; thermal stability ; conductivity ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conducting poly(o-toluidine) (POT) and poly(m-toluidine) (PMT) blends containing 10, 30, 50, 70, and 90 % wt/wt of polystyrene (PSt) were prepared by employing a two-step emulsion pathway. The bands characteristic of both polystyrene and POT/PMT are present in the IR spectra of POT-PSt and PMT-PSt blends. The UV-visible spectra of POT-PSt and PMT-PSt blends exhibit two bands around 313 and 610 nm, confirming that some amount of POT/PMT base is present in the blends. The EPR parameters such as line width and spin concentration reveal the presence of POT/PMT salt in the respective blends. The TGA, DTA, and DSC results suggest a higher thermal stability for the POT and PMT blends than that for the respective salts. The conductivity values of POT(70)-PSt(30) and POT(90)-PSt(10) blends are almost the same (1.1 × 10-2 and 1.3 × 10-2 S cm-1, respectively) and these values are very close to that of pure POT salt, suggesting that POT can be blended with up to 30% wt/wt of PSt to improve its mechanical properties without a significant drop in its conductivity. The conductivity values of PMT-PSt blends are lower than those of the corresponding POT-PSt blends by two to three orders of magnitude, indicating that POT is a better system than PMT to prepare blends by this method. The dielectric constant and tan δ values of the blends increase with the amount POT/PMT and are greater than that of polystyrene. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2291-2299, 1998
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 96
    Electronic Resource
    Electronic Resource
    Characterization and degradation of the poly(methylphenylsiloxane)-poly(methyl methacrylate) graft copolymer (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2521-2530 
    Details
    ISSN: 0887-624X
    Keywords: poly(methylphenylsiloxane) ; poly(methyl methacrylate) ; graft copolymer ; spin-spin relaxation ; degradation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Poly(methylphenylsiloxane)-poly(methyl methacrylate) graft copolymers (PSXE-g-PMMA) were prepared by condensation reaction of poly(methylphenylsiloxane)-containing epoxy resin (PSXE) with carboxyl-terminated poly(methyl methacrylate) (PMMA), and they were characterized by gel permeation chromatography (GPC), infrared (IR), and 29Si and 13C nuclear magnetic resonance (NMR). The microstructure of the PSXE-g-PMMA graft copolymer was investigated by proton spin-spin relaxation T2 measurements. The thermal stability and apparent activation energy for thermal degradation of these copolymers were studied by thermogravimetry and compared with unmodified PMMA. The incorporation of poly(methylphenylsiloxane) segments in graft copolymers improved thermal stability of PMMA and enhanced the activation energy for thermal degradation of PMMA. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2521-2530, 1998
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 97
    Electronic Resource
    Electronic Resource
    Amine-linked thioxanthones as water-compatible photoinitiators (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2563-2570 
    Details
    ISSN: 0887-624X
    Keywords: thioxanthone derivatives ; water-compatible photoinitiator ; absorption spectrum ; fluorescence ; photopolymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Six amine-linked thioxanthones, i.e., 2-(2-hydroxy-3-[bis(2-hydroxyethyl)amino]propoxy)thioxanthone (HAPTX) and its 4-methyl, 1,3-dimethyl, 1,4-dimethyl, 3,4-dimethyl, and 1,3,4-trimethyl substituted derivatives, were synthesized as water-compatible photoinitiators and identified with FTIR, MS, NMR, and elementary analysis. The absorption and fluorescence properties were studied. Their photoinitiating polymerization efficiencies were tested with a recording dilatometer utilizing acrylamide as monomer in aqueous solution. The results show that the six amine-linked thioxanthones can independently initiate acrylamide polymerization efficiently without additional external amines as co-initiators. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2563-2570, 1998
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 98
    Electronic Resource
    Electronic Resource
    Oxidative polymerization of phenylenediamines catalyzed by horseradish peroxidase (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2593-2600 
    Details
    ISSN: 0887-624X
    Keywords: phenylenediamine ; oxidative polymerization ; enzyme ; horseradish peroxidase ; CD spectrum ; organic solvent ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ortho-, meta-, and para-phenylenediamines were polymerized using hydrogen peroxide as an oxidant and horseradish peroxidase as a catalyst in mixed solvents of 1,4-dioxane and water. The yield of the polymers was strongly dependent on solvent composition, and maximum yields were obtained at 15-30% 1,4-dioxane. The analysis of circular dichroic spectra of the enzyme suggested that enzyme structure was significantly modified at high 1,4-dioxane contents, which may be responsible for the decrease of catalytic activity of the enzyme. On the basis of IR and electronic spectra of the polymers, it was considered that o- and p-phenylenediamine polymers retain disubstituted benzene nuclei, which suggests that the polymerization proceeded mainly via N - N coupling. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2593-2600, 1998
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 99
    Electronic Resource
    Electronic Resource
    Synthesis of alkoxyamine initiators for controlled radical polymerization (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2667-2668 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 100
    Electronic Resource
    Electronic Resource
    Syntheses and properties of liquid crystalline N-substituted pyrroles and their polymers (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2691-2698 
    Details
    ISSN: 0887-624X
    Keywords: N-substituted pyrrole ; liquid crystalline polymer ; polypyrrole ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three liquid crystalline N-substituted pyrroles were synthesized from 6-(1-pyrrolyl)hexanol with phenolic derivatives having a mesogenic core of cyclohexylbenzene or biphenyl by Mitsunobu reaction. These pyrroles had two anodic peaks at 1.4 and 1.8 V (vs. SCE). The former was due to an oxidation of the pyrrole moiety and the latter was due to an oxidation of the mesogenic moiety. These pyrrole monomers were polymerized by electrochemical and chemical methods. The potentiostatic method and the chemical method using FeCl3 gave a soluble and fusible polymer, respectively. A polymer having a mesogenic core of cyclohexyl benzene obtained by the chemical method and a polymer having a mesogenic core of biphenylketone obtained by the potentiostatic method had a liquid-crystalline phase. The phase was identified as smectic A by polarizing microscopy and XRD analysis. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2691-2698, 1998
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...