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  • 1985-1989  (3.576)
  • 1965-1969  (3.069)
  • 1987  (3.576)
  • 1966  (1.474)
  • 1965  (1.595)
  • Polymer and Materials Science  (6.209)
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  • 1985-1989  (3.576)
  • 1965-1969  (3.069)
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  • 1
    Digitale Medien
    Digitale Medien
    Prenatal development of the cat thyroid: immunohistochemical demonstration of calcitonin in the “C” cells (1987)
    Springer
    Anatomy and embryology 177 (1987), S. 51-54 
    Details
    ISSN: 1432-0568
    Schlagwort(e): Development ; Thyroid “C” cell ; Cat ; Immunohistochemistry ; Calcitonin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The presence of calcitonin in the cat thyroid was studied immunohistochemically in a series of gland development. the first positive cells are to be found on the 38th day of gestation, i.e. 1–2 days after level nine of ontogenetic development has been reached. The cytoplasm of these cells form only a narrow border round the nucleus. With advancing development the bumber of calcitonin-positive and its amount increases. From approximately the 50th day of prenatal development, the initially diffusely scattered, solitary calcitonin-positive cells are gradually replaced by groups of cells, which begin to occupy a characteristic position in relation to the follicular epithelium. The largest quantity of calcitonin-positive cells is found in foetuses about to be born. In non-pregnant adult cats, the incidence of immunohistochemically calcitonin-reactive cell is more sporadic and their distribution in the lobes of the thyroid is uneven.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00325289
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  • 2
    Digitale Medien
    Digitale Medien
    An investigation of pulp capillaries and tight junctions between odontoblasts in cats (1987)
    Springer
    Anatomy and embryology 177 (1987), S. 131-138 
    Details
    ISSN: 1432-0568
    Schlagwort(e): Capillaries ; Tooth pulp ; Tight junctions ; Odontoblasts ; Ultrastructure ; Mineralisation ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The relative roles of capillaries and odontoblasts in the process of dentinogenesis and in pulp reactions to trauma and pathology are not clear. Contributing to the problem is the paucity of information on odontoblast —capillary relationships and tight junctions between odontoblasts. Using light microscopy the capillaries have now been examined in semithin transverse sections of perfusion fixed teeth at different positions in the long axis from the apical foramina to the pulp horns. Odontoblastic capillaries were prominent in the coronal and middle regions of canines and present at the same levels of incisors. In the pulp horns and just coronal to the pulp horns capillaries were all subodontoblastic but near the apex there were also a few odontoblastic capillary profiles. Transmission electron microscopy on ultrathin sections revealed that a high proportion of middle and coronal odontoblastic capillary profiles were fenestrated but subodontoblastic profiles coronal to the pulp horns were the most fenestrated. In a search for tight junctions in ultrathin sections some typical strands were observed between odontoblasts. The difficult of obtaining the latter evidence was explained by the cellular arrangement of the odontoblasts which differed markedly from an ideal parallel, apically coplanar arrangement. The results question the possibility that there is a direct exchange of materials between pulp capillaries and dentine in teeth of limited growth and provide a baseline for future experiments to test the permeability of the odontoblast layer.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00572537
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  • 3
    Digitale Medien
    Digitale Medien
    Structural alterations in the spinal cord during progressive communicating syringomyelia. An experimental study in the cat (1987)
    Springer
    Acta neuropathologica 72 (1987), S. 248-255 
    Details
    ISSN: 1432-0533
    Schlagwort(e): Experimental communicating syringomyelia ; Ependyma ; Spinal cord ; Cat ; Scanning electron microscope
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary A hydrocephalic-hydromyelic condition was induced in adult cats by causing the closure of the lateral apertures with intracisternal injections of kaolin. After displaying the symptoms characteristic of increased intracranial pressure, which lasted about 10–14 days but varied somewhat in intensity from animal to animal, the cats recovered. From approximately the 2nd post-operative week onward, a distended central canal was revealed by ventriculography; subsequently cavities developed in the tissue of the cord that communicated with the canal. Most cavities were located dorsal to the canal. The surfaces of the distended canal and the cavities showed that in ventral areas the ependyma streched but remained intact, whereas in dorsal areas it ruptured, exposing the nerve fibers to the cerebrospinal fluid (CSF). In cats which had been hydrocephalic for up to 2 years the walls of the cavities were covered by gliotic scar tissue; the nerve fibers were no longer exposed directly to the CSF.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00691097
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  • 4
    Digitale Medien
    Digitale Medien
    Vestibular and optokinetic eye movements evoked in the cat by rotation about a tilted axis (1987)
    Springer
    Experimental brain research 66 (1987), S. 522-532 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Off-vertical-axis rotation ; Eye movements ; Vestibulo-ocular reflex ; Optokinetic nystagmus ; Otoliths ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Horizontal and vertical eye movements were recorded from cats in response to either a) off-vertical axis rotation (OVAR) at a range of velocities (5–72 deg/s) and a range of tilts (0–60 deg) or b) horizontal (with respect to the cat) optokinetic stimulation (10–80 deg/s), also around a range of tilted axes (0–60 deg). The responses to stopping either of these stimuli were also measured: post-rotatory nystagmus (PRN) following actual rotation, and optokinetic after nystagmus (OKAN) following optokinetic stimulation. The response found during OVAR was a nystagmus with a bias slow-phase velocity that was sinusoidally modulated. The bias was dependent on the tilt and reached 50% of its maximum velocity (maximum was 73±23% of the table velocity) at a tilt of 16 deg. The phase of modulation in horizontal eye velocity bore no consistent relation to the angular rotation. The amplitude of this modulation was roughly correlated with the bias with a slope of 0.13 (deg/s) modulation/(deg/s) bias velocity. There was also a low-velocity vertical bias with the slow-phases upwardly directed. The vertical bias was also modulated and the amplitude depended on the bias velocity (0.27 (deg/s) modulation/ (deg/s) bias velocity). When separated from the canal dependent response, the build up of the OVAR response had a time constant of 5.0±0.8 s. Following OVAR there was no decline in the time constant of PRN which remained at the value measured during earth-vertical axis rotation (EVAR) (6.3±2 s). The peak amplitude of PRN was reduced, dependent on the tilt, reaching only 20% of its EVAR value for a tilt of 20 deg. When a measurable PRN was found, it was accompanied by a slowly-emerging vertical component (time constant 5.4±2s) the effect of which was to vector the PRN accurately onto the earth horizontal. OKN measured about a tilted axis showed no differences in magnitude or direction from EVAR OKN even for tilts as large as 60 deg. OKAN following optokinetic stimulation around a tilted axis appeared normal in the horizontal plane (with respect to the animal) but was accompanied by a slowly emerging (time constant 4.1±2 s) vertical component, the effect of which was to vector the overall OKAN response onto the earth horizontal for tilts less than 20 deg. These results are compared with data from monkey and man and discussed in terms of the involvement of the velocity storage mechanism.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00270685
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  • 5
    Digitale Medien
    Digitale Medien
    Expression of “retinal” contrast gain control by neurons of the cat's lateral geniculate nucleus (1987)
    Springer
    Experimental brain research 66 (1987), S. 589-596 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Contrast gain control ; Lateral geniculate nucleus ; Temporal frequency ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary This paper describes the temporal tuning of cells in the lateral geniculate nucleus of the cat (27 X cells, 51 Y cells) and how this changes with stimulus contrast. Drifting sinusoidal gratings of optimal spatial frequency were presented at 7 temporal frequencies (0.5, 1, 2, 4, 8,16 and 32 Hz) and 4 contrasts (10, 20, 40, 80%). For some cells response growth at all temporal frequencies was proportional to changes in contrast. Thus, their temporal tuning functions, on log-log axes, were displaced vertically with increasing contrast. This shift also largely characterizes the response to low temporal frequencies of the other neurons studied. For these other cells, however, responses to high temporal frequencies grew disproportionately large with increasing contrast generally causing their tuning functions to change shape. Typically the peaks of these functions shifted to higher frequencies at higher contrasts. Most of the X cells studied displayed behavior of the first type, while Y cells usually followed the second pattern. This qualitative impression was confirmed quantitatively. Cubic spline functions were fit to the temporal tuning functions obtained at different contrast levels and the peaks of the curves were extracted. X and Y cells preferred similar temporal frequencies at low contrast levels (X mean=8.1 Hz; Y mean=8.4 Hz) but Y cell values were significantly higher at higher contrasts (80%) (X mean= 12.0 Hz; Y mean=16.8 Hz). These contrast-dependent changes in the temporal characteristics of geniculate cells resemble those described for retinal ganglion cells by Shapley and Victor (1978 and subsequent). Thus, the gain control behavior of geniculate cells probably reflects the temporal properties of their retinal inputs with relatively little modification.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00270692
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  • 6
    Digitale Medien
    Digitale Medien
    Reduced binocularity in the noradrenaline-infused striate cortex of acutely anesthetized and paralyzed, otherwise normal cats (1987)
    Springer
    Experimental brain research 68 (1987), S. 593-605 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Ocular dominance ; Plasticity ; Noradrenaline ; Cat ; Visual cortex ; Squint effect
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary In anesthetized and paralyzed cats, the normal alignment of the visual axes is disturbed by paralysis of the eye muscles. Thus, the separation between paired receptive fields of binocular cells in visual cortex is increased (paralysis squint). This increased separation is normally tolerated by the majority of visuocortical cells, about 80% of them being binocularly driven (Hubel and Wiesel 1962). It was shown previously that neuronal plasticity in visual cortex can be enhanced in both normal adult cats (Kasamatsu et al. 1979) and kittens (Kuppermann and Kasamatsu 1984) by intracortical microinfusion of noradrenaline (NA). In the present study we tested whether the usual range of disparity produced by the paralysis squint is sufficient to induce ocular dominance changes in visual cortex of adult cats when the neuronal plasticity is enhanced by NA. NA was continuously infused into visual cortex throughout the experiments. The period of the paralysis squint varied from experiment to experiment between 9 and 47 h. We found: (1) These short periods were sufficient to produce a marked reduction in the proportion of binocular cells. (2) The proportion decreased linearly with increasing the duration of the squint period at a rate of 0.17 per 10 h up to about 22 h. (3) At longer durations the average binocularity remained at about 0.30 and could not be further reduced in the present paradigm. (4) The binocularity seemed to decrease with increasing separation of paired receptive fields. (5) Binocularity increased again toward the normal value after optical correction of the squint. (6) The amount of increased binocularity was linearly correlated with the duration of the period after the squint correction. (7) The binocularity increased at a rate of 0.18 per 10 h, reaching the normal value in less than 30 h. We thus concluded that if visuocortical plasticity is maintained at a high level through the continuous infusion of NA it is possible to change the ocular dominance distribution in the mature visual cortex by manipulations of the alignment of the visual axes even in the acutely anesthetized and paralyzed condition.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00249802
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  • 7
    Digitale Medien
    Digitale Medien
    Receptive field properties of cells in area 19 of the cat (1987)
    Springer
    Experimental brain research 65 (1987), S. 549-558 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Area 19 ; Sinusoidal grating ; End-zone inhibition ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary We have recorded extracellularly from single cells in area 19 of the cat for the purpose of providing a quantitative description of response characteristics. A prominent feature of this area is a high incidence of cells that are end-stopped. Drifting sinusoidal gratings were used to determine spatial and temporal characteristics of the discharge region. In addition, we have conducted independent tests to characterize end zones of receptive fields. When a grating patch was used to stimulate the discharge region alone, all of the cells showed a band-pass spatial frequency tuning characteristic. The optimal spatial frequency ranged from 0.1 to 1.13 cycles/deg, and the distribution had a peak at 0.4 cycles/deg. The bandwidth at half peak amplitude ranged widely from 0.7 to 3.3 octaves (mean 2.0 octaves). When gratings were also presented to the end zones, responses to stimulation of the central region were suppressed. The surround was phase-insensitive in that the relative phase between the grating in the two regions generally did not affect the strength of the suppression. To determine spatial characteristics of the end-zone inhibition, the spatial frequency of the end-zone grating was changed while that for the central pattern was fixed. All cells showed a bandpass characteristic for end-zone inhibition, but in each case, the tuning width was broader than that for excitation. The mean spatial frequency bandwidth of end-zone inhibition was 2.7 octaves. The peak of the inhibition generally coincided with the peak of the excitatory spatial frequency tuning of the discharge center. Considered together, these results show that neurons in area 19 share common properties with those in areas 17 and 18, but they exhibit phase-insensitve end-zone inhibition more frequently.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00235978
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  • 8
    Digitale Medien
    Digitale Medien
    Automatic postural responses in the cat: responses of proximal and distal hindlimb muscles to drop of support from a single hind- or forelimb (1987)
    Springer
    Experimental brain research 65 (1987), S. 527-537 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Postural reflexes ; Unexpected postural perturbations ; Electromyographic activity ; Hindlimb muscles ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Cats respond to drop of the support from beneath a single limb with the “diagonal stance response” (Coulmance et al. 1979). They load the limbs on the diagonal opposite to the one containing the dropped limb and unload the third supporting limb in the diagonal containing the dropped limb. Characteristic biomechanical delays in limb motion and in vertical force changes imposed upon the limbs are observed. These delays range from 30 to 45 ms, depending upon the location of the dropped limb. This study describes the kinematics of the “diagonal stance response” and the activation of selected agonist-antagonist muscle pairs acting on the joints of the hindlimb during the response. Proximal and distal hindlimb muscles respond to perturbations in groups that are appropriate to the vertical forces imposed upon the limb. When the hindlimb containing the recording electrodes is loaded by drop of the contralateral hindlimb or the ipsilateral forelimb medium latency (25–45 ms) EMG responses occur in the extensors. This response serves to stiffen the limb against the increased vertical force of loading. A similar response is observed when the hindlimb is reloaded after being dropped. In this case, however, short latency responses precede the medium latency responses in muscles that are passively stretched by the limb drop. When drop of the diagonal forelimb unloads the hindlimb containing the electrodes, medium latency responses are observed in the distal hindlimb flexors, which indicates that the unloading is evoked in part by active lifting of the limb. In most cases, the medium latency responses precede or are coincident with the changes in force imposed on the limb, suggesting that the observed responses are centrally programmed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00235976
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  • 9
    Digitale Medien
    Digitale Medien
    Neuronal dynamics in the visual corticothalamic pathway revealed through binocular rivalry (1987)
    Springer
    Experimental brain research 66 (1987), S. 10-20 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Corticothalamic feedback ; Binocular rivalry ; Lateral geniculate ; Vision ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Single unit activity was recorded from principal cells in the A-laminae of the cat dorsal lateral geniculate nucleus (dLGN). A steady state pattern of afferent activation was induced by presenting a continuously drifting square wave grating of constant spatial frequency to the eye (the dominant eye) that provided the excitatory input to the recorded cell. Intermittently, a second grating stimulus was presented to the other, nondominant, eye. In most neurones nondominant eye stimulation led to inhibition of relay cell responses. The latency of this suppressive effect was unusually long (up to 1 s) and its intensity and duration depended critically on the similarity between the gratings that were presented to the two eyes. Typically suppression was strongest when the gratings differed in orientation, direction of movement and contrast and when the nondominant eye stimulus was moving rather than stationary. Ablation of visual cortex abolished these long latency and feature-dependent interferences. We conclude that the visual cortex and the corticothalamic projections are involved in the mediation of these interocular interactions. We interpret our results as support for the hypothesis that corticothalamic feedback modifies thalamic transmission as a function of the congruency between ongoing cortical activation patterns and afferent retinal signals.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00236196
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  • 10
    Digitale Medien
    Digitale Medien
    Responses of bradykinin sensitive tooth-pulp driven neurons in cat cerebral cortex (1987)
    Springer
    Experimental brain research 66 (1987), S. 435-439 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Bradykinin ; Tooth-pulp ; Cortical neuron ; Coronal gyrus ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The properties of single cortical neurons responding to electrical stimulation of the tooth-pulp and to intrapulpal application of bradykinin were studied in the cat. The activities of tooth-pulp driven neurons (TPNs) were recorded from the middle and anterior parts of the coronal gyrus of the cerebral cortex. Bradykinin-sensitive tooth-pulp driven neurons (BK-TPNs) were located in layer IV of area 3b of the anterior part of the coronal gyrus. These neurons had a large cutaneous oro-facial receptive field and received a nociceptive input from the facial skin as well as from the tooth-pulp. The BK-TPNs had a higher threshold and longer latency to electrical stimulation than TPNs insensitive to bradykinin (non BK-TPNs). These findings suggest that BK-TPNs in this cortical area may be involved in sensory processing of noxious information from trigeminal regions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00243318
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  • 11
    Digitale Medien
    Digitale Medien
    Responses of cat preoptic neurons to stimulation of the medial frontal cortex and the medial basal hypothalamus (1987)
    Springer
    Experimental brain research 66 (1987), S. 555-564 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Preoptic region ; Frontal cortex ; Medial basal hypothalamus ; Electrophysiology ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Responses of single preoptic neurons to electrical stimulation of the medial frontal cortex, the mediobasal hypothalamus (MBH) and the medial forebrain bundle (MFB) were recorded in anaesthetised cats. Single pulse stimulation of the medial frontal cortex orthodromically drove 96 otherwise quiescent preoptic neurons, which were found more frequently in the dorsal preoptic region, inhibited 53% of the spontaneously active preoptic neurons and excited 16%. Testing of cortically influenced preoptic neurons with MBH or MFB stimulation resulted in antidromic invasion of 6% (MBH) and 9% (MFB). Convergence of orthodromic inputs from medial frontal cortex and MBH was detected in 78% of spontaneously active preoptic neurons, and three-way convergence including input from MFB was noted in 17% of neurons tested with all stimulators. Some cortex-responsive neurons were found to also respond to vaginal or anal probing, paw squeezing and haemorrhage. The role of this input to the preoptic region from medial frontal cortex remains to be elucidated, but may include neuroendocrine, behavioural and homeostatic functions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00270688
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  • 12
    Digitale Medien
    Digitale Medien
    Branching cortical neurons in cat which project to the colliculi and to the pons: a retrograde fluorescent double-labeling study (1987)
    Springer
    Experimental brain research 67 (1987), S. 1-15 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Corticopontine collaterals ; Corticotectal neurons ; Cortex ; Cat ; Fluorescent tracers
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The fluorescent double-labeling technique has been used to determine whether the corticopontine and the corticotectal fibers in the cat are derived from two different sets of neurons or whether they are derived from branching neurons which distribute collaterals to the pontine grey and the colliculi. After unilateral DY.2HCl injections in the pontine grey and FB injections in the ipsilateral colliculi, large numbers of FB-DY.2HCl double-labeled neurons were present in the cortex of the ipsilateral hemisphere. However, the labeled neurons in its rostral part may have represented pyramidal tract neurons which were labeled retrogradely because their fibers descended through the DY.2HCl injection area. Therefore, also DY.2HCl injections were made in the pyramid (i.e. caudal to the pons) and the cortical pyramidal tract area, containing the retrograde DY.2HCl-labeled neurons, was delineated. In the rest of the experiments only the DY.2HCl-labeled neurons in the caudal two thirds of the hemisphere (outside the pyramidal tract area) were taken into account because only these neurons could, with confidence, be regarded as corticopontine neurons. In some anterograde HRP transport experiments the trajectories of the corticotectal and the corticopontine fibers were visualized. On the basis of the findings the DY.2HCl injections in the pontine grey were placed such that they could not involve any of the corticotectal fibers passing from the cerebral peduncle to the colliculi. Thus artifactual doublelabeling of cortical neurons was avoided. However, also under these circumstances many double-labeled neurons were present in the caudal two thirds of the hemisphere. This led to the conclusion that in the cat a large proportion of the corticopontine neurons in the caudal two thirds of the hemisphere represent branching neurons which also distribute collaterals to the colliculi. The parietal (anterior part of the lateral gyrus, middle and posterior suprasylvian gyri) and the cingulate areas together contained three quarters of all labeled corticopontine neurons outside the pyramidal tract area. In the parietal areas roughly 25% of them were double-labeled and in the cingulate area 14%. However, in the visual areas 18 and 19 a much larger percentage (30–60%) was doublelabeled. In a recent study from our laboratory it was found that in the cat the pyramidal tract fibers distribute an abundance of collaterals to the pontine grey. Therefore, a large proportion of all corticopontine connections in this species appear to be established by branching neurons which also distribute fibers to other cell groups in the brain stem and the spinal cord.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00269447
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  • 13
    Digitale Medien
    Digitale Medien
    Detection latencies of X and Y type cells of the cat's dorsal lateral geniculate nucleus (1987)
    Springer
    Experimental brain research 65 (1987), S. 703-706 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Cat ; Electrophysiology ; Lateral geniculate cells ; Signal detection ; Visual latencies
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The latencies of visually-evoked responses from X- and Y-type neurons of the cat's dorsal lateral geniculate nucleus were measured in a manner that takes account of the inherent variability of discharge in these cells. Latencies measured in this way vary from trial to trial in one cell (and also between cells) by tens to as much as hundreds of milliseconds. This variability in the time for generation of reliable responses suggests that the much emphasized conduction advantage of the Y pathway plays a minor role in the detection of visual stimuli by the cat.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00235998
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  • 14
    Digitale Medien
    Digitale Medien
    Convergent inputs from articular, cutaneous and muscle receptors onto ascending tract cells in the cat spinal cord (1987)
    Springer
    Experimental brain research 66 (1987), S. 479-488 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Joint ; Spinal cord ; Pain ; Ascending tracts ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary 1.Responses were recorded from 160 ascending tract cells in segments L4 to L6 of the spinal cord in chloralose anaesthetized, spinalized cats. The tract cells were identified by antidromic activation following stimulation of pathways in the lateral and ventral funiculi at the level of the spinal cord transection at the thoracolumbar junction. Axonal conduction velocities ranged from 9 to 114 m/s. 2. A sample of 152 of the neurones examined could be subdivided according to the distribution of their receptive fields into 49 cells activated just from receptors located in skin (“s” cells), 17 neurones excited by receptors in deep tissues (“d” cells), 15 units with a convergent input from receptors in skin and deep tissues (“sd” cells), and 25 neurones with a convergent input from the knee joint and either skin (“sj” cells), deep tissues (“dj” cells) or both (“sdj” cells). No receptive fields could be demonstrated for the remaining 46 neurones. 3. “S” and “sj” cells were found almost exclusively in the dorsal horn, whereas many “d”, “sd”, “sdj” and “dj” units were in the ventral horn. Almost all of the cells that lacked receptive fields were in the ventral horn or intermediate grey. 4. Ninety-one of 158 cells (56%) demonstrated no background activity. Of these, 43 cells (27%) lacked receptive fields. Many of the silent neurones were in the ventral horn, but some were in the dorsal horn. Of 25 cells having knee joint input, 18 (72%) had background activity. 5. All of the neurones that had a receptive field in the knee joint also had a convergent input from receptors in other tissues. In 3 cases, there was a receptive field in the skin over the foot (“sj” cells). For 16 cells, receptive fields included not only the knee joint but also skin and deep tissue (“sdj” cells). Usually, the cutaneous receptive field was near the knee joint, but sometimes it was remote, such as on the foot. The deep receptive fields were chiefly in the muscles of the thigh and/or leg. For 6 “dj” cells, the receptive fields included not only the knee joint but also deep fields like those of “sdj” cells. 6. Cutaneous receptive fields were classified as “low threshold” (cells excited best by innocuous intensities of mechanical stimulation), “wide dynamic range” (cells activated by weak mechanical stimuli, but the best responses were to noxious stimuli) or high threshold (innocuous stimuli had little effect, but noxious mechanical stimuli produced a vigorous discharge). Similarly, stimulation of the knee joint with weak mechanical stimuli could excite some neurones, while others could be activated by weak or strong articular stimuli but were excited best by noxious stimuli, and still other neurones were activated by knee joint stimuli only if the intensity was noxious. 7. In several instances, contralateral receptive fields were noted. These were generally in deep tissue or in the knee joint. 8. It was concluded that many of the responses to articular stimulation of the spinal cord ascending tract cells examined in this study could have been mediated by the fine afferent fibres that supply the knee joint. Although further work will be required to determine which particular ascending tracts transmit nociceptive information concerning the knee joint, it can be proposed that many of the responses demonstrated here were likely to play a role in either joint pain of in triggering responses associated with joint pain.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00270680
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  • 15
    Digitale Medien
    Digitale Medien
    Lateral excitation in the cat lateral geniculate nucleus (1987)
    Springer
    Experimental brain research 67 (1987), S. 291-298 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Lateral inhibition ; Lateral excitation ; Cat ; Dorsal lateral geniculate nucleus ; GABA ; Silent synapses
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Visual responses were elicited by global phase reversal stimuli in cells of the cat dorsal lateral geniculate nucleus (dLGN) after small retinal lesions had been centered on each receptive field. After acute lesions of different sizes exclusively lateral inhibition was found. When GABAergic inhibition was blocked by continuous microiontophoretic application of bicuculline lateral excitation emerged in dLGN cells partially deafferented by small and medium size acute retinal lesions, but not in those affected by large lesions. This indicates the presence of excitatory retinal inputs at the periphery of the dLGN cell dendrites which are normally suppressed by strong, long-ranging lateral inhibitory processes. After chronic deafferentation, the remaining excitatory inputs increase in effectiveness and lateral excitation is seen without blockade of inhibition. The maximal lateral spread of excitation (300 μm) in the dLGN is distinctly smaller than the extent of lateral inhibition (1000 μm).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00248550
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  • 16
    Digitale Medien
    Digitale Medien
    Automatic postural responses in the cat: responses of distal hindlimb muscles to paired vertical perturbations of stance (1987)
    Springer
    Experimental brain research 68 (1987), S. 477-490 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Postural reflexes ; Unexpected postural perturbations ; Electromyographic activity ; Motor control ; Hindlimb muscles ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The active components of the quadrupedal diagonal stance response to rapid removal of the support from beneath a single limb were studied in cats to further define the mechanisms that trigger and generate the response. We recorded EMG activity from lateral gastrocnemius and tibialis anterior muscles in awake, behaving cats while they stood on an hydraulic posture platform. By dropping the support from beneath a single limb, we evoked the diagonal stance response, with its characteristic changes in vertical force and EMG patterns. As the animal responded to this drop, a second perturbation of posture was then presented at intervals of 10 to 100 ms following the first. This second perturbation, which consisted of dropping the support from beneath the two limbs that were loaded as a result of the initial limb drop, made the first response biomechanically inappropriate. The EMG responses observed in both muscles during paired perturbations were triggered by the somatosensory events related to the perturbations. Muscle responses that were appropriate for the first perturbation always occurred with amplitudes and latencies similar to control trials. This was true even when the second perturbation occurred 10–20 ms after the first, that is, when this perturbation either preceded or was coincident with the response to the initial limb drop. The EMG responses that were normally associated with the second perturbation were delayed and/or reduced in amplitude when the time interval between perturbations was short. As the inter-perturbation interval was lengthened beyond 60–100 ms, however, EMG responses to the second perturbation were unaffected by the occurrence of the first perturbation. When the hindlimb containing the recording electrodes was dropped as part of the second perturbation, a myotatic latency response was observed in tibialis anterior. The amplitude of this response to the second perturbation was greater than controls when this displacement was presented during the period between initiation of the first perturbation and execution of the response to it. When the second displacement was presented after execution of the first response began, the amplitude of the myotatic response was reduced below control levels. While the results do not preclude the possibility that these “automatic” postural responses are segmental or suprasegmental reflexes, they support the hypothesis that the active component of the response to drop of the support beneath a single limb is centrally programmed and that the appropriate response can be riggered very rapidly by the somatosensory information signalling the perturbation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00249792
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  • 17
    Digitale Medien
    Digitale Medien
    The pattern of ocular dominance columns in flat-mounts of the cat visual cortex (1987)
    Springer
    Experimental brain research 68 (1987), S. 661-666 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Visual cortex ; Ocular dominance columns ; Flat-mount ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Ocular dominance (OD) columns in the cat visual cortex were visualized with autoradiography after intravitreal injection of (3H)proline. Extending previous studies, a flat-mount technique was applied that enabled the analysis of the distribution of label throughout extensive regions of the visual cortex without requiring reconstructions from serial sections. OD-columns were confined to layer IV and consisted of isolated patches and short bands. The latter were parallel to each other and regularly spaced, the main trajectory being orthogonal to the 17/18 border. This pattern of the geniculo-cortical terminals was similar in the hemispheres ipsi- and contralateral to the injected eye. The mean periodicities of the OD-bands were virtually identical in the two hemispheres of the same animal: 850 μm and 830 μm in cat D1 and 770 μm and 800 μm in cat D2. However, the ipsilateral OD-columns appeared smaller, more heavily labeled and more sharply delineated than the contralateral columns.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00249809
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  • 18
    Digitale Medien
    Digitale Medien
    Enhancement of the responses of ascending tract cells in the cat spinal cord by acute inflammation of the knee joint (1987)
    Springer
    Experimental brain research 66 (1987), S. 489-499 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Joint ; Pain ; Inflammation ; Spinal cord ; Ascending tracts ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary 1. Recordings were made from 16 ascending tract cells in the spinal cords of anaesthetized, spinalized cats before and after an acute arthritis was produced by injection of kaolin and carrageenan into the knee joint. 2. The responses tested routinely were to passive flexion of the knee, an innocuous movement. In some cases, responses to other movements were also tested, and changes in background discharge rates were monitored. 3. Control recordings for a period of 1 h or in 3 cases of 3 h indicated that the responses to flexion were reasonably stationary. 4. Four tract cells that initially showed little or no response to flexion of the knee joint developed large responses within 1 to 2 h after inflammation of the joint. 5. Another 9 cells were tested that had responses to flexion of the knee joint prior to inflammation. In 6 cases, inflammation produced enhanced static or transient responses. In 2 cases, the effect of flexion was initially inhibitory or variable, but after inflammation these cells showed large excitatory responses. In the other case, inflammation had no effect. Background discharges were increased by inflammation in 6 of these 9 cells. 6. The effect of inflammation of the knee joint was tested on 3 tract cells that had no clearly defined receptive field in the knee. In 1 case, a response developed to knee flexion after acute inflammation was produced. In the other 2 cases, there were initially responses to knee flexion, but these were unchanged by inflammation. 7. Two of the cells tested had bilateral receptive fields in or around the knee joints. Inflammation of one knee joint enhanced the responses to flexion of the same but not of the contralateral knee in one case but greatly increased the responses to flexion of both knees in the other case. 8. Injections of prostaglandin (PGE2) caused an enhancement of the responses to knee flexion beyond that caused by inflammation in 5 of 7 cases. One cell whose responses to flexion of the knee were unaffected by inflammation showed inhibitory responses to prostaglandin injections into the inflamed knee joint. 9. The effects of inflammation on the responses of ascending tract cells of the spinal cord appear to serve as a useful neural model of the events responsible for the development of arthritic pain.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00270681
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  • 19
    Digitale Medien
    Digitale Medien
    Synaptic organization of olfactory inputs and local circuits in the entorhinal cortex: a current source density analysis in the cat (1987)
    Springer
    Experimental brain research 67 (1987), S. 615-622 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Entorhinal area ; Current source density ; Olfactory afferents ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The distribution of the olfactory afferents within the ventrolateral part of the entorhinal cortex (EC) was studied by means of field potentials evoked by stimulation of the olfactory bulb (OB) and the olfactory cortex (PPC). Depth profiles of the field potentials evoked by OB or PPC stimulation were studied using current source density analysis. After OB or PPC stimulation an early superficial sink-deep source configuration was found, which some time later reversed into a superficial source-deep sink. Both OB and PPC activated mainly the superficial dendrites of the cells of layers II and III. In layers II and III evidence for strong recurrent inhibition was found, using double pulse stimulation. The results indicate that there exists a common basic design of the synaptic organization of the olfactory areas of the base of the brain extending to the EC.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00247292
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  • 20
    Digitale Medien
    Digitale Medien
    Direct projections from Ammon's horn to the septum in the cat (1987)
    Springer
    Experimental brain research 68 (1987), S. 179-188 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Ammon's horn ; Hippocampus ; Septum ; Dentate gyrus ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Direct projections from Ammon's horn to the septum were studied in the cat by the anterograde tracing method after injecting WGA-HRP (wheat germ agglutinin-horseradish peroxidase conjugate) into Ammon's horn. The results were further confirmed by the retrograde WGA-HRP method after injecting WGA-HRP into the septum. Pyramidal neurons in fields CA1, CA2 and CA3 were observed to send their axons ipsilaterally to the lateral septal nucleus; the septal parts of the hippocampus sent projection fibers to the dorsomedial portions of the lateral septal nucleus via the medial aspects of the subcallosal fornix, while the hippocampal regions successively more proximal to the temporal pole sent projection fibers to progressively more ventrolateral portions of the lateral septal nucleus via more lateral aspects of the subcallosal fornix. It was also found that the septal parts of fields CA1, CA2 and CA3 sent projection fibers bilaterally to the dorsomedial aspects of the lateral septal nucleus. Field CA4 appeared to send projection fibers only sparsely, if at all, to the medial septal nucleus. The rudimentary parts of the hippocampal formation, taenia tecta and indusium griseum, were found to have reciprocal ipsilateral connections with the dorsal portions of the lateral septal nucleus.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00255243
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  • 21
    Digitale Medien
    Digitale Medien
    Binocular interaction in the dorsal lateral geniculate nucleus of the cat (1987)
    Springer
    Experimental brain research 68 (1987), S. 305-310 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Binocular interaction ; Lateral geniculate nucleus ; Cat ; Retinal disparity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary We have investigated binocular interaction in the dorsal lateral geniculate nucleus (LGN) of the cat. Neurons were recorded extracellularly during visual stimulation with sinusoidal gratings which were presented at different interocular phases (disparities). The large majority of cells (91%) exhibited some type of binocular interaction. For 75% and 16% of the total number of cells, the binocular interaction was inhibitory or facilitatory, respectively. For the remaining 9% of cells, no interaction was evident. In marked distinction from visual cortex, the facilitatory and inhibitory interactions in the LGN are independent of the relative interocular phase of the patterns. Neurons in the LGN are therefore insensitive to the stereoscopic depth cue, retinal disparity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00248796
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  • 22
    Digitale Medien
    Digitale Medien
    Processing of interaural time and intensity differences in the cat inferior colliculus (1987)
    Springer
    Experimental brain research 68 (1987), S. 379-392 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Cat ; Inferior colliculus ; Single cell recording ; Binaural hearing ; Time/intensity trading
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary 1. Binaural neurones were recorded in the central nucleus of the cat inferior colliculus and were stimulated with tone and noise bursts. Closed field sound systems were used to produce independent interaural time (ITD) and intensity (IID) differences. Particular attention was paid to high frequency (above 2 kHz) cells. 2. Three main types of binaural neurone were found: High frequency excitatory-inhibitory neurones (EI cells), excited by input from the contralateral ear and inhibited by ipsilateral input, high frequency excitatory-excitatory cells (EE cells), excited by inputs from either ear and low frequency cells sensitive to interaural phase differences (IPD cells). 3. The EI cells had characteristics similar to those of IE cells in the contralateral lateral superior olive. They were sensitive to envelope ITDs (most cells) and IIDs (all cells) favouring the contralateral ear. The response of these cells increased with increasing contra lead ITDs or contra loud IIDs up to values well outside the physiological range. 4. Low frequency binaural cells were sensitive to interaural phase differences (IPDs). The peak response was often in the contralateral physiological range and the response was unaffected by IIDs. 5. Many high frequency EE cells were sensitive to envelope ITDs. These units were relatively unaffected by IID. Although the ITD sensitivity of these cells was generally less than that of the IPD cells, the peak response of the ITD curve was also often in the contralateral physiological range. 6. Some of the high frequency EI and EE cells were sensitive to ongoing time differences (OTDs) in white noise signals, i.e. they showed ITD response curves to carrier only shifted noise bursts. 7. The EI cells often showed recovery from inhibition at large ipsilateral lead. This tendency was increased as the sound pressure level on the inhibitory side was lowered and by the use of click stimuli. Similarly, cycles of suppression could be seen to follow excitation in some EE cells. The time course of these effects was in the order of hundreds of μs. 8. Binaural characteristics (degree of ITD, IID or OTD sensitivity) showed considerable interunit variation within each cell type. These variations were also affected by signal type (tone or noise bursts) and did not appear to be correlated with best frequency, nature of the tuning curve or PSTH type. We suggest that the time course of the inhibitory and excitatory effects at each unit (and its interaction with the signal type) determines the type of ITD response and that this time course varies from cell to cell.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00248803
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  • 23
    Digitale Medien
    Digitale Medien
    Effects of monocular strobe rearing on kitten striate cortex (1987)
    Springer
    Experimental brain research 68 (1987), S. 525-532 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Cat ; Visual cortex ; Stroboscopic exposure ; Monocular experience ; Motion deprivation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Monocular deprivation in kittens does not lead to an ocular dominance shift in striate cortex if the visual stimuli do not contain contours. In the present study we sought to find out whether an ocular dominance shift is produced if the visual environment does contain contours but is devoid of motion. Six kittens were reared with one eye occluded in a visual environment that was lit only by the light of a stroboscope (2 flashes per sec). Exposure was started at 5–6 weeks of age after dark-rearing from birth and extended until 8–12 weeks of age for 8 h per day. The rest of the time was spent in total darkness. Thus, the animals were completely deprived of vision in one eye, while the other eye experienced only stationary flashing contours. Single units in area 17 of these animals were studied and compared to normally reared cats. In all six animals ocular dominance was clearly shifted towards the eye with strobe experience. The ocular dominance shift showed, however, the following interdependencies with other parameters: neurones that responded to stationary flashing test stimuli were nearly always dominated by the strobe eye; neurones that responded only to moving bars or edges remained binocular. In the normal control animals the ocular dominance distribution was similar for both groups of cells. Track analysis according to cortical lamination revealed that neurones in infragranular layers consistently showed a weaker OD shift towards the strobe eye than neurones in supragranular layers (including layer 4). Response latencies to stationary flashing stimuli were significantly shorter in the strobe-reared animals than in the normal controls. Orientation tuning was normal in all animals. Directional tuning was reduced after monocular strobe experience, but not by the same amount as described after binocular strobe rearing. The present results demonstrate that monocular visual experience reduced to stationary flashing contours is sufficient to produce on ocular dominance shift in striate cortex. This adds further support to existing notions about the role of nervous activity for changes in cortical connections. Cortical responses to afferent stimulation and the resulting correlated activation of pre- and postsynaptic neurones seem to be a prerequisite for a stabilization of synaptic connections.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00249796
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  • 24
    Digitale Medien
    Digitale Medien
    Tonotopic organization in the medial geniculate body (MGB) of lightly anesthetized cats (1987)
    Springer
    Experimental brain research 69 (1987), S. 24-42 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Medial geniculate body ; Tonotopic organization ; Single unit pairs ; Frequency selectivity ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary In the medial geniculate body (MGB) of nitrous oxide anesthetized cats, the pars lateralis (PL) was the only nucleus to show a clear topographic arrangement of its neurons according to their characteristic frequency (CF). When compared to barbiturate anesthetized cats (Imig and Morel 1985a), the tonotopic organization in PL appeared less strict and was characterized by a significant local CF disparity. Furthermore, the degree of tonotopic organization varied along the rostrocaudal axis of the nucleus: it was lower in its caudal than in its rostral half. In the pars ovoidea, the rostral half of the pars magnocellularis (PM) and the suprageniculate nucleus, CF sequences and quantitative evaluations of the tonotopicity indicated the presence of some degree of tonotopic organization which was lower than in PL. No such organization was observed in the caudal part of PM nor in the ventrolateral nucleus, while in the dorsal nucleus, the proportion of toneresponding units was too low for a significant analysis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00247026
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  • 25
    Digitale Medien
    Digitale Medien
    The effects of CO2 and fixed acid on the O2-Hb affinity of rabbit and cat blood (1987)
    Springer
    Pflügers Archiv 408 (1987), S. 451-457 
    Details
    ISSN: 1432-2013
    Schlagwort(e): O2-Hb affinity ; Bohr effect interaction ; CO2 Bohr effect ; Fixed acid Bohr effect ; Rabbit ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The action of respiratory and metabolic acid-base disturbances on the O2-Hb affinity was studied in rabbits and cats. Blood samples of both species were exposed to in vitro pH-changes, which were either achieved by variation ofPCO2 (2.8–8.3 kPa) at constant lactic acid concentration, or by addition of lactic acid (5–14 mmol·l−1) at constantPCO2. ThePO2 at halfsaturation (P50) and the Hill'sn were determined from O2-Hb dissociation curves (ODC) in a range between 20 and 80% SO2. Under standard conditions (T=331 K,PCO2=5.33 kPa, pH=7.4), the average P50 value was 4.66±0.05 kPa in rabbits, that is slightly higher than reported by others, and 5.17±0.03 kPa in cats. The average values of Hill'sn were 2.91±0.02 and 2.95±0.03 for rabbits and cats, respectively. When plasma pH was varied by CO2, the resulting classical CO2 Bohr factor φCO2=ΔlgP50/ΔpH50 was distinctly higher in cats (−0.560±0.006,n=25) than in rabbits (−0.504±0.014,n=22), although in the latter species being even higher than reported elsewhere. Concomitant metabolic acidosis did not significantly affect φCO2, but shifted the P50 at a given plasma pH to lower values. Substitution of lactic acid with equimolar amounts of sodium lactate left both φCO2 and P50 unchanged. When plasma pH was varied by lactic acid (LA), the resulting fixed acid Bohr factors φLA were similar for cats (−0.420±0.016,n=21) and rabbits (−0.427±0.010,n=18), and not influenced by additional respiratory acidosis. Concomitant respiratory acidosis, however, shifted the P50 at a given plasma pH to higher values. The deviation of lgP50 from that under standard conditions (lgP50st) induced by both, respiratory and metabolic acid-base changes, can generally be expressed by Eqs. (1) or (2) (1) $$1gP_{50} - 1gP_{50} st = \varphi CO_2 \left( {pH - 7.4} \right) - \left( {\varphi CO_2 - \varphi LA} \right) \cdot \left[ {pH\left( {LA} \right) - 7.4} \right]$$ (2) $$1gP_{50} - 1gP_{50} st = \varphi LA\left( {pH - 7.4} \right) + \left( {\varphi CO_2 - \varphi LA} \right) \cdot \left[ {pH\left( {CO_2 } \right) - 7.4} \right].$$ Thereby, the first term considers the total pH-deviation, irrespective of its origin, and the second term represents the metabolic (1) or the respiratory (2) correction. For practical use and within the physiological range of plasma pH (7.2–7.6), φCO2 and φLA are assumed to be additively linked and to be independent of pH. Once these factors are determined for a given species, together with the buffer capacity for CO2, they provide sufficient data to estimate fairly accurately the position of the ODC. This is particularly important for in vivo conditions where respiratory and metabolic acid-base disturbances often occur simultaneously.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00585068
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  • 26
    Digitale Medien
    Digitale Medien
    Responses of sacral visceral afferents from the lower urinary tract, colon and anus to mechanical stimulation (1987)
    Springer
    Pflügers Archiv 410 (1987), S. 296-303 
    Details
    ISSN: 1432-2013
    Schlagwort(e): Sacral visceral afferents ; Pelvic nerve ; Urinary bladder ; Urethra ; Colon ; Anus ; Functional properties ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The discharge characteristics of sacral visceral afferents supplying the urinary bladder, urethra, colon and anus to mechanical stimuli were analyzed in the anaesthetized cat. The stimuli used were passive distension (urinary bladder, colon), isovolumetric contraction (urinary bladder), movements of the urethral catheter and mechanical shearing stimuli (mucosal skin of the anal canal). (1) In total 245 afferent units which projected in the pelvic nerve were isolated from the sacral dorsal roots. From one of the following organs, urinary bladder, colon, urethra and anus 117 afferent units were activated. By these stimuli from the bladder, urethra and anus 122 afferent units could not be activated, and as far as tested also not from the colon; in 6 afferent units the classification was unclear. (2) Afferent units from the urinary bladder and the colon responded consistently to passive distension of the respective organ. The units from the urinary bladder showed graded responses at intraluminal pressures of about 10–70 mm Hg and responded also to isovolumetric contractions of the organ. The thresholds of the units from the bladder to passive distension and contraction varied from about 5 to 20 mm Hg intravesical pressure. (3) The afferent units from the urethra and the anus did not react or showed some weak phasic and irregular responses to distension and contraction applied to the urinary bladder or to distension of the colon. They were consistently excited by low threshold mechanical stimulation of the urethra and anus, respectively. (4) The axons from the bladder, urethra and anus were presumably myelinated (conduction velocity above 2 m/s) and conducted at 10.3±6.1 m/s (n=34, mean±SD), 26.3±9.3 m/s (n=13) and 9.5±5.1 m/s (n=37), respectively. The axons from the colon conducted at about 0.5 to 16 m/s (n=20), 13 of them conducting at less than 2 m/s. About 75% of the axons which could not be activated by mechanical stimulation of the visceral organs were presumably unmyelinated (conduction velocity below 2 m/s). (5) Some ongoing activity was found in 9 out of 26 afferent units from the anus but, with one exception, the afferent units from the bladder, urethra and colon were silent. (6) It is concluded that the pelvic afferent units from the urinary bladder, urethra, colon and anus consist of distinct populations with characteristic response patterns. There is no indication from this investigation that the urinary bladder is supplied by sacral afferents which are only recruited at high intravesical pressures during passive distension and isovolumetric contractions and which are possibly associated with pain.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00580280
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  • 27
    Digitale Medien
    Digitale Medien
    Morphology of ultrahigh molecular weight polyethylene surface slid against steel (1987)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 150 (1987), S. 189-192 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A morphological study was made to examine the friction and wear mechanisms of ultrahigh molecular weight polyethylene in air and water by means of transmission electron microscopy of a carbon replica film of a very thin layer of the polymer surface slid against a steel ball. Electron diffractions revealed that a molecular orientation with a typical fiber pattern was formed in the friction in air, while thin ribbon-like crystals with particular crystal orientations were formed in water in a way that the sliding took place on the crystallographic a - c plane, giving rise to a low friction coefficient of the polymer.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1987.051500116
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  • 28
    Digitale Medien
    Digitale Medien
    Degradation of polypropylene: Effect of stabilizers (1987)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 150 (1987), S. 137-150 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Es wurde der relative Wirkungsgrad von fünf handelsüblichen Stabilisatoren bei Photooxidation und thermischer Alterung von Polypropylen (PP) anhand der Änderungen der mechanischen Eigenschaften untersucht. Es wurden Polypropylenproben mit unterschiedlichem Anteil an Cyasorb UV-531 hergestellt (bezeichnet als PC0.5-31, PC1-31, PC1.5-31 und PC2-31). Der Einfluß der Photooxidation auf das thermische Verhalten ist mit Hilfe der Differentialscanningkalorimetrie und durch thermogravimetrische Analysen untersucht worden. 2-Hydroxy-4-n-octyloxybenzophenon (2 Gew.-%) war am wirksamsten, Polypropylen, gegen Verfärbung und Brüchigkeit zu stabilisieren. Bei einer Probe mit 1% Stabilisatorzusatz fanden sich nach 32 h Bestrahlung noch 81% des ursprünglichen Wertes der Streckgrenze gegenüber 18% bei unstabilisiertem PP.
    Notizen: The relative effectiveness of five commercially available stabilizers on the photooxidation and thermal ageing of polypropylene (PP) was investigated by following changes in mechanical properties. Samples of PP containing different percentages of Cyasorb UV-531 were prepared (designated as PC0.5-31, PC1-31, PC1.5-31, and PC2-31, respectively). The effect of photooxidation on thermal behaviour was investigated by differential scanning calorimetry and thermogravimetric analysis. 2-Hydroxy-4-n-octyloxy benzophenone (2% w/w) was most effective in stabilizing PP towards discolouration and brittleness. After 32 h irradiation, 81% retention in yield strength was observed in case of PC1-31 against 18% in case of PP.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1987.051500111
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  • 29
    Digitale Medien
    Digitale Medien
    Modified starch-natural rubber blend, I. Cyanoethylation of xanthated starch (1987)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 153 (1987), S. 113-124 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Käufliche Weizenmehlstärke wurde unter Verwendung verschiedener Mengen Schwefelkohlenstoff und Acrylnitril xanthogeniert und cyanethyliert und dann zur Herstellung von modifizierten Stärke-Naturkautschuk-Masterbatches eingesetzt. Weiterhin wurden die Einflüsse untersucht, die die Gleichgewichte der Xanthogenierung und Cyanethylierung gegenseitig aufeinander ausüben. Die Ergebnisse werden auf der Basis definierter Wechselwirkungen zwischen der Xanthogenatgruppe und dem freien Acrylnitril erklärt. Hierbei führen sowohl sterische Faktoren als auch die höhere Elektrophilie des Acrylnitrils zum Zerfall der Xanthogenatgruppe. Daher kann die Cyanethylierung nur noch in einem geringeren Ausmaß erfolgen.
    Notizen: Common wheat flour starch was subjected to xanthation followed by cyanoethylation at various levels of carbon disulfide and acrylonitrile to prepare modified starchnatural rubber masterbatches. Mutual influences of the extents of equilibrium xanthation and cyanoethylation on each other have been studied. The results have been explained on the basis of a definite interaction between xanthate group and free acrylonitrile in which both the steric factors and higher electrophilicity of acrylonitrile lead to the decomposition of xanthate groups and reduced the extent of cyanoethylation.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1987.051530108
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  • 30
    Digitale Medien
    Digitale Medien
    Blends of polychloroprene and polyvinylchloridePresented in part at the International Conference on Rubber and Rubberlike Materials, November 6-8, 1986, Jamshedpur, India. (1987)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 153 (1987), S. 153-163 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Aus Polychloropren und Polyvinylchlorid wurden Blends in verschiedenen Zusammensetzungen hergestellt und ihre Eigenschaften bestimmt. Die Eigenschaften der Blends zeigen, daß sie Polychloropren in vielen Anwendungen ersetzen können.
    Notizen: Blends of polychloroprene rubber and plasticized polyvinylchloride have been prepared in various compositions and their properties evaluated. The properties of the blends show that they can be used to replace polychloroprene in many applications.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1987.051530111
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  • 31
    Digitale Medien
    Digitale Medien
    Eine rheo-optische Apparatur für die Durchführung homogener, einfacher Dehnungen an Polymerschmelzen mit simultaner Aufzeichnung der Deformation, der mechanischen Spannung und der Doppelbrechung (1987)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 153 (1987), S. 135-152 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: The present paper describes a rheo-optical apparatus consisting of an elongational rheometer (with rotary clamps) and a device to measure birefringence. This equipment was designed to perform homogeneous deformations on polymer melts in the simple elongational mode. Elongational experiments were performed on polyisobutylene samples at room temperature using different strain rates (from \documentclass{article}\pagestyle{empty}\begin{document}$\dot \varepsilon$\end{document} 0.01 s-1 to 1 s-1). In typical experiments homogeneous elongations up to λ ≈ 200 and stresses up to 2 · 106 Pa were achieved. The stress, the birefringence, and the deformation were obtained by measuring the force, the sample thickness, the optical retardation (the frequency of the sampling was 20 Hz) and the width of the sample (the frequency of the sampling was 3 Hz). It was found that the stress-optical coefficient was constant. The homogeneity of the deformations was carefully controlled because inhomogeneities cause serious errors in the measurements of elongational viscosity and birefringence.
    Notizen: Es wird über eine rheo-optische Apparatur zur Verstreckung von Polymerschmelzen mit rotierenden Klemmen berichtet, die mit einer Doppelbrechungs-Meßeinrichtung ausgerüstet ist. Mit dieser Einrichtung können einfache Dehnungen an Polymerschmelzen bis zu hohen Verstreckgraden unter homogenen Bedingungen durchgeführt werden. Während des Deformationsvorganges können die Spannung, die Doppelbrechung und die Probendicke mit einer Meßrate von 20 Hz, sowie die Probenbreite mit ca. 3 Hz erfaßt werden.Wir haben Messungen an Polyisobutylen bei Raumtemperatur mit verschiedenen Dehngeschwindigkeiten (0,01 s-1 〈 \documentclass{article}\pagestyle{empty}\begin{document}$\dot \varepsilon$\end{document} 〈 1 s-1) bis zu einem Verstreckgrad von λ ≈ 200 durchgeführt. Dabei wurden Spannungen bis zu 2 · 106 Pa erhalten. Das spannungsoptische Gesetz war bei homogener Versuchsführung stets erfüllt. Es wird gezeigt, daß ohne Kontrolle der Dehngeschwindigkeit und insbesondere bei inhomogener Dehung nicht nur Abweichungen vom spannungsoptischen Gesetz, sondern auch große Fehler bei der Spannungs- bzw. Viskositätsberechnung auftreten. Deshalb wurde großer Wert auf die Prüfung der Homogenität der Dehnung gelegt.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1987.051530110
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  • 32
    Digitale Medien
    Digitale Medien
    Verträglichkeit zwischen Methacrylat-homo- und Copolymeren (1987)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 153 (1987), S. 187-195 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: The miscibility of various polymethylmethacrylate (PMMA)/polybutylmethacrylate (PBMA)/poly(methylmethacrylate-co-butylmethacrylate)systems has been studied. PMMA and PBMA are immiscible. Methacrylic homopolymers and copolymers are immiscible, too. A one-phase mixture from PMMA and PBMA is only accessible by copolymerization.
    Notizen: Die Mischbarkeit von verschiedenen Systemen aus Polymethylmethacrylat (PMMA), Polybutylmethacrylat (PBMA) und Poly(methylmethacrylat-co-butylmethacrylat) (P(MMA-co-BMA)) wurde untersucht. PMMA und PBMA sind miteinander nicht mischbar. Die untersuchten Homopolymeren und entsprechende Methacrylatcopolymere bilden ebenfalls heterogene Systeme. Einphasige Mischungen aus PMMA und PBMA sind nur über Copolymerisation erreichbar.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1987.051530114
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  • 33
    Digitale Medien
    Digitale Medien
    Ethylene insertion with soluble Ziegler catalysts. III. The system cp2TiMeCl/AlMe2Cl/13C2H4 studied by 13C-NMR spectroscopy. The time-development of chain propagation and oligomer distributionPart II cf. lit.1. (1987)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 154 (1987), S. 1-21 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Mit Hilfe der 13C-NMR-Spektroskopie wurde die Entwicklung der Oligomerenverteilung während der Polymerisation von 13C-angereichertem Ethylen mit dem löslichen Ziegler-Katalysatorsystem Cp2TiMeCl/AlMe2Cl verfolgt. Zuordnung und quantitative Auswertung aller Signale der verschiedenen wachsenden Ketten werden beschrieben. Die Geschwindigkeiten der Ethylen- und der Cp2 TiMeCl-Abnahme sowie die Bildungsgeschwindigkeit neuer Ketten konnten direkt aus den Spektren ermittelt werden. So läßt sich zum ersten Mal zeigen, daß die Konzentration der Ti-Propyl-und Ti-Pentylspezies in einen stationthen Zustand einlaufen. Dies ermbglicht, die Geschwindigkeitskonstanten der Ethyleninsertion in die Ti-Kohlenstoffbindung von Ti-Me, Ti-Pr und Ti-Pe zu ermitteln. Diese Ergebnisse fiihren zu einem detaillierten Ein-blick in den Ablauf der ersten Insertionsschritte und sind so eine Grundlage fur die mathematische Modellierung. Sie sind aufierdem ein weiterer unabhlngiger Beweis für die Giiltigkeit des dynamischen Modells des Mechanismus der Ethylenpolymerisation mit lbslichen Ziegler-Katalysatoren, nlmlich die Bildung der polymerisationsaktiven Spezies in zwei aufeinanderfolgenden sehr dynamischen Gleichgewichtsreaktionen.
    Notizen: The development of the oligomer distribution during the polymerization of 13C-enriched ethylene by the soluble Ziegler catalyst system Cp2 TiMeCl/AlMe2Cl was followed by 13C-NMR spectroscopy. The assignment of the signals from the growing chains is described in full. It is shown that the rate of consumption of ethylene and Cp2 TiMeCl and the rate of formation of new chains can be monitored directly from the spectra. The concentrations of Ti-propyl and Ti-pentyl species during the polymerization were followed spectroscopically; both attain a steady state concentration. The relative rates were determined for the insertion of ethylene in the Ti-carbon bond of Ti-Me, Ti-Pr and Ti-Pe. These results give a detailed insight into the way that the oligomer distribution develops and provide a basis for its computer simulation. They also provide an independent proof that the dynamic model for the mechanism of ethylene polymerization with soluble Ziegler catalysts of the type Cp2 TiRCl/AlRnClm is correct.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1987.051540101
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  • 34
    Digitale Medien
    Digitale Medien
    Effects of reaction conditions on bromination of atactic poly(propylene) (1987)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 154 (1987), S. 99-110 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Der Einfluß verschiedener Reaktionsbedingungen auf die Bromierung von ataktischem Poly(propylen) (APP) in Tetrachlorkohlenstofflösung wurde untersucht. Mit zunehmender Reaktionszeit steigt der Bromierungsgrad. Auch mit steigender Verdünnung der APP-Lösung nimmt die Bromierungsgeschwindigkeit zu, welche bezüglich der APP-Konzentration die Ordnung 0,66 hat. Dies wird erklärt durch die anfängliche Substitution eines Wasserstoffs am tertiären Kohlenstoffatom. Die folgende H-Abstraktion an den benachbaren sekundären und primären Kohlenstoffatomen ist erleichtert. Die scheinbare Aktivierungsenergie wurde zu 11,9 kcal/mol bestimmt. Die Bromierungsgeschwindigkeit steigt bis zu einem APP : Br2-Molverhältnis von 1 : 1 an, darüber hinaus wird die Geschwindigkeit unabhängig vom Molverhältnis. Die Bromierung scheint folgendermaßen zu verlaufen: Nach anfänglicher Substitution eines tertiären H-Atoms durch freie Bromradikale werden nach und nach auchdie sekundäen und primären H-Atome durch weitergehende Substitution oder durch Addition nach einem Eliminierungsschritt ersetzt. Das IR-Spektrum bestätigt die Anwesenheit von Brom in den Proben.
    Notizen: Effects of various reaction conditions on bromination of atactic poly(propylene) (APP) in carbon tetrachloride solution were studied. It was found that with the increase of the reaction time the extent of bromination increases. Also with an increased dilution of APP the rate of bromination increased following a bromination order of 0.66 with respect to APP concentration. This has been ascribed to initial replacement of the hydrogen at the tertiary carbon atoms followed by enhanced ease of abstraction from the neighbouring secondary and primary carbon atoms. The apparent activation energy was found to be 11.9 kcal/mol. The rate of bromination increases with an increase of the APP: Br2 molar ratio up to 1 : 1, beyond which the rate becomes independent of this ratio. Mechanism of bromination appears to be an initial substitution of tertiary H-atoms by bromine radicals followed subsequently by replacement of secondary and primary H-atoms via either progressive substitution or elimination-addition. IR spectra confirm the presence of bromine in the samples.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1987.051540107
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  • 35
    Digitale Medien
    Digitale Medien
    A high molecular-weight sequential polypeptide, poly(leucyl-γ-ethyl glutamyl-alanyl-alanyl) (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 5-8 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360260104
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  • 36
    Digitale Medien
    Digitale Medien
    Determination of thermodynamic functions from scanning calorimetry data (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 213-229 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We present a theoretical basis and new methods for the determination of thermodynamic functions from scanning calorimetry data. A thermodynamic state is defined here as an ensemble of microstates in the system, and it can be defined only through assumptions of its heat capacity function and the two integral constants. With these assumptions, scanning calorimetry data can be analyzed using the single or double (or multi-) deconvolution presented here. New equations to calculate the van't Hoff enthalpy function and the calorimetric enthalpy function are presented. We prove that the agreement of these two functions is a necessary and sufficient factor for the condition that the system can be described with the assumed two-state model.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360260205
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  • 37
    Digitale Medien
    Digitale Medien
    Poly[d(A-T)-Cs+] conformations studied by IR spectroscopy (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 251-260 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Infrared absorption and ir linear dichroism measurements have been performed on poly[d(A-T)-Cs+] films at various relative humidities. At high relative humidity, samples are in a B form; at low relative humidity, in a C form. The B → C conformational transition is shown to be a noncooperative one corresponding to a gradual evolution of the backbone geometry of the polynucleotide within the B family. the C-form-type spectrum is characteristic of an alternated phosphodiester chain with a dinucleotidic repeat unit.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360260207
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  • 38
    Digitale Medien
    Digitale Medien
    Masthead (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987) 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360260301
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  • 39
    Digitale Medien
    Digitale Medien
    Reversal of the long-wavelength CD band of poly(dI-dC) · poly(dI-dC) on specific interaction with the 53-58 peptide fragment of the lac repressor (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 329-332 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360260302
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  • 40
    Digitale Medien
    Digitale Medien
    Molecular mechanical studies on left- and right-handed B-DNA (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 403-414 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Molecular mechanical simulations on base-paired deoxyhexanucleoside phosphates, (dAdT)3 · (dAdT)3, (dTdA)3 · (dTdA)3, (dGdC)3 · (dGdC)3, and (dCdG)3 · (dCdG)3, have been carried out to assess their energetic stabilities in left- and right-handed forms. These hexamers have also been simulated with alternating sugar-puckering profiles with the combinations (purine : C2′-endo-pyrimidine : C3′-endo) and (purine : C3′-endo-pyrimidine C2′-endo). The right-handed models have been found to be the energetically most stable structures and the left-handed structures are significantly destabilized. This instability has been rationalized in terms of competition between stabilizing stacking interactions on one hand, and distortions in the bond angles and torsion angles in the sugar-phosphate backbone on the other.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360260308
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  • 41
    Digitale Medien
    Digitale Medien
    Loop formation in polynucleotide chains. II. Flexibility of the anticodon loop of tRNAPhePresented in part at the Biophysical Society Meeting, San Antonio, Texas, February 1984. (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 415-438 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The flexibility of hairpin loops containing n bases (residues) has been examined using a theoretical model [N. L. Marky and W. K. Olson (1982), Biopolymers, 21, 2329-2344] of oligonucleotide loop closure. The study is based on correlated probabilities of chain separation and terminal residue orientation as outlined previously. The probabilities are calculated using standard statistical mechanical methods as functions of local conformational changes of the chain backbone. Our results for an RNA chain of 9 residues suggest that the anticodon loop is a dynamic structure capable of assuming a variety of different spatial conformations. Free energy values related to the various conformations span a narrow range of values (2-4 kcal/mole) and compare well with experimental observations in aqueous solution. Conformational transitions between the loop conformations are within less than 0.5 kcal/mole in free energy. The different spatial loop conformations and the likely pathways between them may have potential relevance to the molecular translation of the genetic code.
    Zusätzliches Material: 16 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360260309
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  • 42
    Digitale Medien
    Digitale Medien
    Structural models for the N- and C-terminal telopeptide regions of interstitial collagens (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 463-480 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Secondary-structure prediction has been used to investigate the conformation of the N- and C-terminal telopeptides for type I and type III collagen. The three predictive methods (Chou and Fasman, Robson and co-workers, Lim) indicate mainly aperiodic conformations. A common structural motif is provided by the positioning of β-turns, particularly in the vicinity of the residue sites involved in intermolecular cross-links. An alternative model to that of Helseth et al [(1979) Biopolymers 18, 3005-3014] for the secondary structure of the N-terminal telopeptide of type I collagen is proposed. The general features of these two contrasting structures have been surveyed by model-building techniques employing molecular graphics and energy minimization. The role of the telopeptide component in the structural design of the biomaterial collagen is assessed. Notably, the alternative model clearly serves to demonstrate the compatibility of current cross-linking evidence with the quasi-hexagonal model for the packing of molecules within a collagen fibril.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360260403
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  • 43
    Digitale Medien
    Digitale Medien
    Conformation of the oligonucleotide d(AAAAAATTTTTT)2 by two-dimensional nuclear overhauser effect spectroscopy and its relevance to poly(dA) · poly(dT) (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 525-536 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Conformational analysis from the pattern and intensities of cross-peaks in the two-dimensional nuclear Overhauser effect proton nmr spectra of the homopolymer, poly(dA) · poly(dT), and the analogous oligomer, d(AAAAAATTTTTT)2, indicate that they both exist in the B-conformation. The conformation of the ApT/TpA junction in the oligomer is significantly different from the rest of the base pairs.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360260406
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  • 44
    Digitale Medien
    Digitale Medien
    Masthead (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987) 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360260501
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  • 45
    Digitale Medien
    Digitale Medien
    The mobility of polyions in gel electrophoresis (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 609-611 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360260503
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  • 46
    Digitale Medien
    Digitale Medien
    Masthead (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987) 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360260101
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  • 47
    Digitale Medien
    Digitale Medien
    Editor's note (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. iii 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360260102
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  • 48
    Digitale Medien
    Digitale Medien
    Radius of the elastic rod model of a polyelectrolyte (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 1-3 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360260103
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  • 49
    Digitale Medien
    Digitale Medien
    The influence of calcium ions on fibrin polymerization (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 27-43 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The influence of calcium ions on the polymerization induced in fibrinogen solutions by thrombin and by Reptilase has been investigated by meansof static and dynamic light scattering in combination with measurements of the release of the fibrinopeptide A. The calcium concentration was varied in the range between 0.3 and 103 calcium ions per fibrinogen molecule. The enzyme concentration was chosen sufficiently low so that it was possible to make quantitative observations as a function of time, in particular, beforethe onset of gelation. Likewise, the influence of calcium ions on the enzymatically induced polymerization of fragment X was studied. The results indicate that there are at least three mechanisms by which calcium can influence the evolution of the polymer system on the path to gelation and clotting. Which mechanism dominates depends upon the calcium concentration.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360260107
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  • 50
    Digitale Medien
    Digitale Medien
    Local sequence patterns of hydrophobicity and solvent accessibility in soluble globular proteins (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 17-26 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We examined the variation in the solvent accessibility and hydrophobicity of the amino acids along the sequences of 58 soluble globular proteins with known tertiary structure. We found that there is a significant tendency for the accessibilities to run in clusters along the sequence but that the hydrophobicities are distributed without such nonrandom clusters. Theseresults suggest severe limitations on the power of sequence analysis tools that use average hydrophobicity scores of overlapping subsequences to predict accessibility.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360260106
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  • 51
    Digitale Medien
    Digitale Medien
    On the CD helix band for long helical polymers (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 109-119 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The CD helix bands for infinitely long helical polymers are shown tobe composed of two parts: a derivative-shaped band plus an ordinary Gaussian-like band. The derivative-shaped band results from the zero-order term of an expansion while the Gaussian-like band results from the first-order expansion term. However, the intensities of the two bands are shown to be of the same order of magnitude. They are both linear in the coulombic coupling of transition charge densities for polymer transitions. The sum yields a skewed derivative-shaped band. The shapes of net CD helix bands are shown to not depend on the approximations used for averaging over orientations if the usual systems, such as polypeptides and polynucleotides, are considered in their long-wave-length spectral regions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360260112
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  • 52
    Digitale Medien
    Digitale Medien
    Prediction of the folding of short polypeptide segments by uniform conformational sampling (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 137-168 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A procedure, CONGEN, for uniformly sampling the conformational spaceof short polypeptide segments in proteins has been implemented. Because thetime required for this sampling grows exponentially with the number of residues, parameters are introduced to limit the conformational space that has to be explored. This is done by the use of the empirical energy function ofCHARMM [B. R. Brooks, R. E. Bruccoleri, B. D. Olafson, D. J. States, S. Swaminathan and M. Karplus (1983) J. Comput. Chem. 4, 187-217] and truncating the search when conformations of grossly unfavorable energy are sampled. Tests are made to determine control parameters that optimize the search without excluding important configurations. When applied to known protein structures, the resulting procedure is generally capable of generating conformations where the lowest energy conformation matches the known structure within a rms deviation of 1 Å.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360260114
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  • 53
    Digitale Medien
    Digitale Medien
    Number of binding sites of DNA and polynucleotides with tris(2,2′-bipyridyl)ruthenium(II) cationsDedicated to professor arther charesby on the occasion of his 70th birthday. (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 189-201 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The binding of tris(2,2′-bipyridyl)ruthenium(II) cations [Ru(bpy)2+3] with single- and double-stranded (ss and ds) DNA, and the polynucleotides poly(A), poly(C), poly(G), poly(I), poly(I) · poly(C), and poly(U), was studied in aqueous solution. Steady-state electrical conductivity measurements with the polynucleotides, ssDNA, and dsDNA reveal that approximately three nucleotides offer one binding site. This may be compared with the ratio [nucleotide]/[Mg2+] of 2.4 : 1 for dsDNA. After laser excitation (353 nm), the luminescence of Ru(bpy)2+3 bound to nucleic acids shows two decay components. The contribution of the fast component, which is interpreted as resulting from quenching processes of the absorbed ruthenium complex, exhibits a maximum with increasing [nucleotide]/[Ru(bpy)2+3] at a ratio of about three to one. Bound Ru(bpy)2+3 can be released from the strand by addition of NaClO4 [half-concentration: 2.5 and ≤ 10 mM for poly(U) and dsDNA, respectively].
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360260203
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  • 54
    Digitale Medien
    Digitale Medien
    Predicting antibody hypervariable loop conformation. I. Ensembles of random conformations for ringlike structures (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 2053-2085 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: One approach to finding the conformation of minimum energy for a complicated molecule is to perform energy minimization, perhaps coupled to more exhaustive search procedures such as dynamics or Monte Carlo sampling, from many starting conformation. Where there are geometric constraints on the conformations, as in a ring molecule, or a variable loop starting and ending in known constant regions of one of a series of homologous proteins, rapidly generating many such starting conformations, all satisfying the constraints, has been a problem in the past. We have devised an algorithm, which we call random tweak, which performs this task in the context of a torsional description of a molecule, and have used it to model the backbones of the six CDRs (complementarity determining regions) of the immunoglobulin MCPC603. These range in size from 5 to 19 residues, and have from 8 to 36 variable dihedral angles. Ensembles of 100 properly closed backbone structures for each CDR were generated under several conditions of van der Waals screening internally and against the rest of the molecule, and ensembles of 1000 were generated for selected CDRs. These structure “libraries” reveal how the geometry at the base of a CDR and the topography of the surrounding protein surface restrict the region of space that a given CDR can occupy. In accord with simple notions of chain molecule statistics, the more highly extended a CDR at its base, the more similar the possible structures and the fewer that are necessary to span the conformational space. Energy minimization and molecular dynamics studies (reported elsewhere) using these libraries to furnish starting conformations show that, as the number of residues in a CDR goes from five to nine, the number of randomly generated structures necessary to ensure that low-lying energetic minima, such as the native conformation, will be found several times goes from a few tens to a few hundred. Some of the spatial features of an ensemble of random conformations are implicit in the histogram of the rms atomic displacements calculated for all the pairs in the ensemble. The random tweak method is carried out by setting each dihederal angle on the main chain of the variable fragment to a random value, then using an iterated linearized Lagrange multiplier technique to enforce the geometric constraints with the minimal conformational perturbation. The time required for the algorithm is linear in fragment length, and the resulting ability of the method to handle large loops makes it especially applicable to the modeling of homologous proteins. In most cases, hundreds of acceptable structures could be generated in a few hours on a VAX 11/780. Where van der Waals screening against fixed atoms need not be performed, as for isolated ring molecules, generation times go down by an order of magnitude or more.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360261207
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  • 55
    Digitale Medien
    Digitale Medien
    Dynamic light-scattering study of semiflexible polymers: Collagen (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 1717-1729 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Dynamic light-scattering measurements were carried out for collagen in acetate buffer (pH 4.8) extracted from lathyritic ratskin. The correlation functions were analyzed in terms of the semiflexibility of collagen molecules. The experimental Γ/K2 vs K2 relationship was compared with the theoretical one based on formulation including anisotropy in translational diffusion, chain flexibility, and the hydrodynamic interaction; Γ is the average decay rate and K is the magnitude of the momentum transfer vector. By using the model parameters evaluated from the Γ/K2 vs K2 relationship, a good agreement was obtained between profiles of theoretical and experimental correlation functions over the entire delay times. Detailed examinations of the dynamic light-scattering spectrum permitted us to conclude that a set of the contour length L of 300 nm and the Kuhn length γ-1 of 340 nm are much more probable than other sets of L and γ-1 that equally explain static quantities such as the radius of gyration. The results show that collagen molecules are well characterized by a wormlike chain model.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360261006
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  • 56
    Digitale Medien
    Digitale Medien
    Dynamic properties of oxy- and carbonmonoxyhemoglobin probed by optical spectroscopy in the temperature range of 300-20 K (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 1769-1779 
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    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We have studied the absorption bands of oxy- and carbonmonoxyhemoglobin in the wavelength range of 650-350 nm (visible and Soret bands) and in the temperature range of 300-20 K. The spectra in the whole temperature range have been successfully deconvoluted in terms of gaussian components. The analysis of the temperature dependence of the first and second moment of the bands enables us to compare dynamic properties of the heme group in oxy- and carbonmonoxyhemoglobin. The results of the analysis indicate that the “mean-effective” frequency of the nuclear motion coupled to the electronic transition responsible for the visible bands is higher in carbonmonoxy- than in oxyhemoglobin. The possible functional relevance of this finding is discussed.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360261009
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  • 57
    Digitale Medien
    Digitale Medien
    A predictive model of enzymatic cleavage of nucleic acids (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 1789-1807 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A new static model of enzymatic cleavage of polymeric substrates such as nucleic acids has been derived. The model is compared to that elaborated by Tanford and to experimental data. In predicting the fragment distribution for a restriction enzyme digestion of a circular substrate, the model is superior to that of Tanford.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360261011
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  • 58
    Digitale Medien
    Digitale Medien
    A mixed β-turn and β-sheet structure for bovine tooth enamel amelogenin: Raman spectroscopic evidence (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 1809-1813 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360261012
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  • 59
    Digitale Medien
    Digitale Medien
    Theoretical conformational analysis of a μ-selective cyclic opioid peptide analog (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 1431-1444 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The allowed conformations of the μ-receptor-selective cyclic opioid peptide analog were determined using a grid search through the entire conformational space. Energy minimization of the 13-membered ring structure lacking the exocyclic Tyr1 residue and the Phe3 side chain using the molecular mechanics program Maximin resulted in only four low-energy conformations. These four ring structures served as templates for a further energy minimization study with the Tyr1 residue and Phe3 side chain added to the molecule. The results indicated that the Tyr1 and Phe3 side chains enjoy considerable orientational freedom, but nevertheless, only a limited number of low-energy side-chain configurations were found. The obtained low-energy conformers are discussed in relation to various proposed models of the bioactive conformation of enkephalins and morphiceptin.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360260817
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  • 60
    Digitale Medien
    Digitale Medien
    Solvent effect on the stability of mannobiose conformersPart X: Theoretical Studies on the Conformation of Saccharides. (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 1499-1508 
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    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The conformational equilibria of seven methyl β-D-mannobioside conformers have been studied theoretically in five solvents. The structure of each individual conformer has been refined by the PCILO quantum-chemical method from the seven distinct low-energy regions determined from (Φ, Ψ) maps calculated by a potential function method. The stability of the conformers in dilute solution has been evaluated by using a method that consists of electrostatic, dispersion, and cavity terms. The calculated abundance of conformers depends on the solvent and results indicate that the preponderant conformer in the solution may not be the one adopted by mannobiose in the crystalline form. Based on the determined abundance of conformers, thermodynamically averaged nmr parameters, dipole moment, and linkage rotation have been calculated. The solvation behavior of methyl β-D-mannobioside is compared to those previously estimated for cellobiose and maltose.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360260905
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  • 61
    Digitale Medien
    Digitale Medien
    The thermodynamic parameters of the interaction of concanavalin A with glycosyl-free liposomes: A microcalorimetric study (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 1509-1526 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The nonspecific interaction of the mitogenic lectin Concanavalin A (Con A) with glycosyl-free liposomes of various composition has been investigated by microcalorimetric titration measurements. The results obtained show the following features of main interest: (1) the affinity constants (Ka) of the interaction of Con A with liposomal bilayers are in the order of magnitude 105-106M-1. The reaction enthalpies (ΔH) are positive, and small (approximately 0.1 KJ mol-1 lipid), compared to the free energy terms (-ΔG = 30-40 KJ mol-1 lipid). All lectin-lipid interactions are strongly entropy-controlled (ΔH/TΔS 〈 1.0). These thermodynamic features are characteristic for hydrophobic interaction processes. (2) The liposomal head-group charge does not significantly affect the lipid-affinity of Con A. Electrostatic forces thus appear to play a minor role in lectin-lipid interactions. (3) The lipid affinity of Con A is sensitive to the fluidity of the liposomal bilayers, increasing with increasing fluidity. Below the gel to liquid-crystal phase transition temperature, the lectin binding to liposomal bilayers is inhibited. (4) The binding isotherms, corresponding to the interaction of Con A with liposomes, composed of tightly packed, saturated phospholipids, exhibit pronounced positive cooperativity. This phenomenon is absent in the binding curves, corresponding to the interaction of Con A with more fluid liposomal bilayers. (5) The Con A specific inhibitor α-D-methylmannopyranoside (50 mM) drastically increases the molar reaction enthalpy. The Ka term is significantly reduced in presence of the inhibitor sugar. Urea induces analogous changes in the thermodynamic parameters of the lectin-lipid interaction. The effects of α-D-methylmannopyranoside are thus not Con A specific, but are attributable to solvent effects. (6) It was shown that the binding of one Con A molecule affects a large number (approximately 1000) of phospholipid molecules in the liposomal bilayer. (7) The affinity constants (Ka) of the interaction of Con A with glycosyl-free lipids are smaller by a factor of approximately 10, compared to the Ka terms, reported for Con A binding to biological membranes. The presence of glycosidic receptor groups thus controls the specificity of lectin-membrane interactions, whereas the nonspecific lectin-lipid interactions appear to represent the main driving force for the strong attachment of the lectin to membrane surfaces.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360260906
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  • 62
    Digitale Medien
    Digitale Medien
    Calculating thermodynamic data for transitions of any molecularity from equilibrium melting curves (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 1601-1620 
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    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: In this paper, we derive the general forms of the equations required to extract thermodynamic data from equilibrium transition curves on oligomeric and polymeric nucleic acids of any molecularity. Significantly, since the equations and protocols are general, they also can be used to characterize thermodynamically equilibrium processes in systems other than nucleic acids. We briefly review how the reduced forms of the general equations have been used by many investigators to evaluate mono- and bimolecular transitions, and then explain how these equations can be generalized to calculate thermodynamic parameters from common experimental observables for transitions of higher molecularities. We emphasize the strengths and weaknesses of each method of data analysis so that investigators can select the approach most appropriate for their experimental circumstances. We also describe how to analyze calorimetric heat capacity curves and noncalorimetric differentiated melting curves so as to extract both model-independent and model-dependent thermodynamic data for transitions of any molecularity. The general equations and methods of analysis described in this paper should be of particular interest to laboratories that currently are investigating association and dissociation processes in nucleic acids that exhibit molecularities greater than two.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360260911
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  • 63
    Digitale Medien
    Digitale Medien
    Conformational studies of diastereomeric cyclic enkephalins by 1H-NMR and computer simulations (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 1573-1586 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We report the solid-phase synthesis and conformational analysis of a 14-membered, cyclic enkephalin analog, H—Tyr—c[—D—A2bu—Gly—Phe—D—Leu—] (where A2bu represents α,γ-diaminobutyric acid). The results from the guinea pig ileum (GPI) and mouse vas deferens (MVD) assays show that the analog, though active, has little selectivity for the μ or δ opioid receptors. Conformational analysis is carried out using 1H-nmr and computer simulations, including molecular dynamics and energy minimizations. The results obtained here are compared with the findings of our studies carried out on the μ-receptor-selective diastereomer, H—Tyr—c[—D—A2bu—Gly—Phe—Leu—] [N. Mammi, M. Hassan, and M. Goodman (1985) J. Am. Chem. Soc. 107, 4008-4013]. This comparison allows for insight into the regiospecificity of these cyclic enkephalin analogs.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360260909
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  • 64
    Digitale Medien
    Digitale Medien
    Characterization of the interactions of an amino-terminal fibronectin fragment with the native molecule: Implications for polymerization of fibronectinThe results of this study were presented in abstract form at the 1986 meeting of the American Society of Biological Chemists in Washington, D. C. (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 2087-2098 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Plasma fibronectin is a 450-kD glycoprotein composed of two similar subunits connected by interchain disulfide bridges that may fold over in solution, allowing the amino terminus of each chain to bind the carboxyl terminus of the same subunit or a different subunit, thereby allowing polymerization. In order to study the characteristics of the fold-over interaction, the interaction between the amino terminal 29-kD fragment of fibronectin with native fibronectin has been studied in detail. One 29-kD molecule bound per fibronectin subunit, the apparent equilibrium dissociation constant was 40 nM, and the half-times for association and dissociation at 22°C were, respectively, 16 h and 23 days. Complexation could be inhibited by high concentrations of salt, but not by 8M urea. Amino terminal 20-kD and carboxyl terminal 8-kD subfragments of the 29-kD fragment also bound fibronectin and the activity was dependent on the integrity of the type 1 loop structures. The kinetics of the interaction of 29-kD fragment with fibronectin were unaffected by the presence of ligands, but were affected by detergents such as sodium dodecyl sulfate or deoxycholate, which enhanced the rate of interaction over 100-fold or 6-fold, respectively. Therefore, the interaction of fibronectin with ionic cell membrane components such as deoxycholate in vivo may trigger polymerization.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360261208
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  • 65
    Digitale Medien
    Digitale Medien
    Editor's note (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. Si 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360260002
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  • 66
    Digitale Medien
    Digitale Medien
    Peptidomimetics: Synthesis, spectroscopy, and computer simulations (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. S25 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Synthesis, spectroscopy, and computer simulations are used in an integrated approach to elucidate secondary structure of oligopeptides. Three lactam-bridge peptides were synthesized and examined. One of these model compounds was shown to prefer a β-turn conformation, as indicated by spectroscopy (CD and nmr), and by computer simulations of minimum potential energy and of molecular dynamics. Partial retro-inverso cyclic analogs of enkephalin were also synthesized and investigated. Biological activity studies of the analogs indicated that the Gly3 carbonyl group and the side-chain orientation of the L-Leu5 residue are important. Hydrogen-bonding patterns for the three analogs are described in terms of the spectroscopic evidence correlated to the molecular dynamics simulations.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360260007
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  • 67
    Digitale Medien
    Digitale Medien
    On the multiple-minima problem in the conformational analysis of polypeptides. I. Backbone degrees of freedom for a perturbed α-helixThis article is dedicated to Ephraim Katchalski-Katzir on the occasion of his 70th birthday. (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. S33 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The multiple-minima problem is the most formidable in the conformational analysis of polypeptides. Several approaches have been developed to surmount this problem, and we present an additional one here that may possibly be extendable to very large polypeptides. In this new approach, designated the Self-Consistent Electric Field (SCEF) method, we calculate the electric field, due to the whole molecule, at each CO and NH group of the peptide units, and also in the middle of the C′N peptide bonds, for an arbitrary starting conformation. It is assumed that the native conformation has approximately optimal orientations of its group dipoles in the electric field. The direction of the electric field with respect to the CO and NH bond dipole moments provides information as to which peptide units are the worst oriented. We then compute the changes in the backbone dihedral angles φ and ψ required to align the most unfavorably oriented peptide-unit dipole moments along the electric field. After carrying out such alignment of dipoles, a complete potential energy function is used in a minimization procedure to locate the nearest local minimum. The SCEF and energy-minimization procedures are then applied iteratively to try to locate the global minimum. The effectiveness of this method is illustrated by computations on very different starting conformations of terminally blocked 19-residue chains of poly(L-alanine), for which the global minimum is judged to be the right-handed α-helix.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360260008
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  • 68
    Digitale Medien
    Digitale Medien
    Raman and normal-mode studies of the extended-helix conformation in polypeptide chainsThis is paper number 36 in a series on vibrational analysis of peptides, polypeptides, and proteins, of which Ref. 23 is paper number 35. (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. S99 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The nature of the local main-chain conformation of polypeptides with charged side chains has been the subject of considerable discussion since Tiffany and Krimm first proposed [(1968) Biopolymers 6, 1379-1381] that, rather than being random, the chain is locally relatively regular, with conformations similar to that of a left-handed threefold helix. Such structures, referred to as “extended-helix” (EH) conformations, have now been studied in a charged poly(L-glutamic acid) system by a combination of Raman spectroscopy and normal-mode analysis. Calculations were done for EH conformations with 3.0 and 2.4 residues/turn, using force fields refined for α-helix, 31-helix, and β-sheet structures. Together with previous results on the α-helix and β-sheet forms, an interesting new correlation emerged: the frequency of the CαC stretch skeletal mode, usually found in the 900-1000 cm-1 region of the Raman spectrum, is essentially linearly correlated with the value of the φ angle. Applying this relationship to the observed frequencies of the α-helix and β-sheet forms of poly(L-glutamic acid), we find that an observed sharp band in the spectrum of crystals of the calcium salt of poly(L-glutamic acid) (which is close to the frequency observed for the charged form in solution) corresponds to an EH conformation very close to that predicted from energy calculations. These studies thus provide very strong support for our proposal that charged polypeptide chains are not random but adopt local conformations of the EH type.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360260011
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  • 69
    Digitale Medien
    Digitale Medien
    Noise as a source of information about dynamical properties of biological macromolecules (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. S161 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The time course of a noise signal is not completely random, since it is coupled to the characteristic dynamical behavior of the physical system that produces the noise. The statistical properties of the noise may thus be very informative about the properties of the noise-generating system. The use of the autocorrelation function, of modified autocorrelation functions that show directionality with respect to the time axis, and of probability density-distribution functions of intervals in noise traces are discussed. Thus, by labeling specific points on polymer chain molecules by suitable chormophores between which excitation energy transfer may occur and by analyzing the autocorrelation function of the fluctuations in the emitted fluorescence under steady illumination, one may characterize the internal dynamics of the polymer molecules. It is also shown that the presence or absence of time directionality in noise traces, as tested with the help of some of the above-mentioned statistical functions, may demonstrate whether the noise-generating system is at thermodynamic equilibrium or whether irreversible processes are coupled to the dynamic changes that produce the noise signals.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360260015
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  • 70
    Digitale Medien
    Digitale Medien
    Salting-out adsorption techniques for protein purification (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. S193 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Salt-promoted adsorption of proteins occurs on hydrophobic gels, on immobilized metal ions e.g., Zn2+, Co2+, Ni2+, Cu2+, and on newly described absorbents provisionally called “thiophilic gels.” The latter gels are characterized by the ligand structure —SO2—CH2—CH2—S—R. In a simple form (R = —CH2—CH2—OH) the “T-gel” is extremely useful for rapid isolation of immunoglobulins from complex mixtures. When R is rich in π-electrons the thiophilic affinity will be superimposed by charge-transfer coupling with hitherto unknown counterligands in interacting proteins. The use of tandem and cascade processes for protein fractionation according to several more or less independent separation parameters is briefly demonstrated.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360260017
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  • 71
    Digitale Medien
    Digitale Medien
    The emulsan polymer: Perspectives on a microbial capsule as an industrial product (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. S223 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Microbial polysaccharides have become significant industrial products in recent years, primarily because of their high molecular weight and unique rheological properties. More recently, a new class of microbial biopolymer has been developed - namely, the exopolysaccharide bioemulsifiers. The best studied of this class of biopolymer is the capsular anionic polysaccharide of the oil-degrading bacterium Acinetobacter calcoaceticus RAG-1, emulsan. The emulsan polymer (MW, 106) consists of D-galacatosamine, D-galactosamine uronic acid (pKa, 3.01), and a diamino deoxyhexosamine. The amphipathic properties of emulsan are due in part to the presence of fatty acids linked to the polysaccharide backbone in both ester and amide linkages. Emulsan is characterized by a very high affinity for the oil/water interface, and its major industrial application is in the stabilization of oil-in-water emulsions at very low concentrations (emulsan : oil, 1 : 1000). This interfacial binding is accompanied by a conformational change in the polymer, which in turn allows for the concentration of normally water-soluble cations, proteins, and even phages in the oil layer after emulsion separation. Emulsan is now a commercial product produced by fermentation on an industrial scale. Two major applications are likely to involve its ability to stabilize heavy oil-in-water emulsions for (1) transportation in pipelines of high-viscosity oils at lower temperatures and (2) upgrading of high-viscosity fuels so that the homogeneous oil/water emulsions can be burned directly without water removal. Both applications have been tested on a semi-industrial scale and their feasibility has been demonstrated.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360260020
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  • 72
    Digitale Medien
    Digitale Medien
    Synthesis and characterization of some 2,4′-dibenzyldiisocyanate ionic polymers. II. Cationic polyurethances using N,N′-bis-(β-hydroxyethyl)-piperazinePart I cf. lit5. (1987)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 147 (1987), S. 99-106 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Es wurden kationische Polyurethane mit Piperazinringen in der makromolekularen Kette hergestellt. Die Polymeren bilden elastische und lichtdurchlässige Filme. Das Verhalten der verdünnten Lösungen in Lösungsmitteln mit verschiedenen Dielektrizitätskonstanten wurde untersucht.
    Notizen: Cationic polyurethanes containing piperazine rings on the macromolecular chain were synthesized. The polymers form flexible and transparent films. The behaviour of diluted solutions in solvents of different dielectrical constants was studied.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1987.051470109
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  • 73
    Digitale Medien
    Digitale Medien
    The effect of various pigments on the rheological behaviour and morphology of polypropylene (1987)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 147 (1987), S. 113-122 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: In der vorliegenden Arbeit werden die Charakteristika von pigmentiertem Polypropylen (PP) untersucht. Die Ergebnisse zeigen, daß die Fließeigenschaften von PP-Schmelzen, die Morphologie und das Zugverhalten der Fasern deutlich von der Anwesenheit verschiedener, in der PP-Matrix dispergierter Pigmente beeinflußt werden. Die Auswirkungen verschiedener, dem PP zugefügten Pigmente zeigen große Unterschiede. Der Fließwiderstand von PP steigt mit Zugabe von Phthalocyaninblau, Ruß und Titandioxid, fällt aber bei der Anwesenheit von “BR red” und “GL orange” Die Strangaufweitungseffekte der PP-Schmelze werden durch Addition dieser Pigmente intensiviert. Die Elastizitätsgrenze von Fasern mit stäbchenförmiger Struktur ist 80-125% niedriger als die von Fasern mit Sphärulitstruktur.
    Notizen: In this paper the characteristics of polypropylene (PP) containing pigments are systematically studied. The results show that the flow properties of PP melt, morphological structures, and drawing behaviour of the fibres are obviously affected by the presence of certain pigments dispersed in the PP matrix. The effects of various pigments added in PP display great difference. The flow resistance of PP increases with the addition of phthalocyanine blue, carbon black, and titanium dioxide, but decreases with the presence of BR red and GL orange. The extrudate swell effects of PP melt are intensified by adding these pigments. The yield stress of filaments with rod structure is 80-125% lower than that of filaments with spherulitic structure.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1987.051470111
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  • 74
    Digitale Medien
    Digitale Medien
    Propriétés de la Surface d'un Film de Polyéthylène Modifiée par Greffage d'un Oligomère Acrylique (1987)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 147 (1987), S. 147-156 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: The grafting of a liquid acrylic derivative (2-methylenepentane-1,5-dicarboxylic acid diethylester) on the surface of a polyethylene film (HD) was carried out in the presence of benzoylperoxide. The wettability of the surface was investigated with respect to the adhesion properties against aluminium and compared with those of a film of polyethylene grafted in mass with acrylic acid. The mobility of the surface grafted chains may cause the differences in the observed comportment.
    Notizen: Le greffage d'un dérivé acrylique liquide (méthylène-2 pentanedïoate-1,5 de diéthyle) est effectué en présence de peroxyde de benzoyle à la surface d'un film de polyéthylène (HD). Les propriétés de mouillabilité de la surface sont examinées en relation avec les propriétés d'adhésion vis à vis de l'aluminium, et comparées avec celles d'un film de polyéthylène greffé dans la masse à l'acide acrylique. La mobilité des chaǐnes greffées à la surface pourrait ětre à l'origine des différences de comportement observées.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1987.051470114
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  • 75
    Digitale Medien
    Digitale Medien
    Study of polymerization of methacrylamide initiated by persulphate with different activators (1987)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 150 (1987), S. 151-159 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Die Polymerisation von Methacrylamid wurde in wäßriger Phase unter Verwendung von Persulfat/Äpfelsäure und Persulfat/Ethanolamin als Redox-Systeme unter Stickstoff untersucht. Bezüglich des Persulfats wurde für beide Fälle eine Reaktion erster Ordnung gefunden, für Äpfelsäure ergab sich die Ordnung 1/2, für Ethanolamin nullte Ordnung. Für Methacrylamid wurde im Ansatz mit K2S2O8/Äpfelsäure erste Ordnung und im Ansatz mit K2S2O8/Ethanolamin die Ordnung 1,5 gefunden. Das mittlere Molekulargewicht wurde viskosimetrisch für die unter verschiedenen Bedingungen erhaltenen Proben bestimmt.
    Notizen: The aqueous polymerization of methacrylamide was studied by using persulphate/malic acid and persulphate/ethanolamine redox pairs under nitrogen atmosphere. The order with respect to persulphate was found to be one half with both the redox systems. Malic acid and ethanolamine show half order and zero order, respectively. Methacrylamide has first order dependence on the rate of polymerization initiated by K2S2O8-malic acid system and one and half order dependence on the rate of polymerization initiated by K2S2O8-ethanolamine redox pair. Viscometric average molecular weight was determined for the samples obtained under different kinetic conditions.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1987.051500112
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  • 76
    Digitale Medien
    Digitale Medien
    Functionalization of atactic polypropylene using allyl and azide compounds (1987)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 150 (1987), S. 1-11 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Ataktisches Polypropylen wurde durch die Umsetzung mit Dicumylperoxid (8 Gew.-%) und einer Allylverbindung (8 Gew.-%) (Eugenolmethylether, Allylphenylether, Allylharnstoff, N-Allylthioharnstoff, Allylmalonsäurediethylester und N-Allylanilin) bei 170°C funktionalisiert. Bei der Reaktion von tert-Butylazidoformat mit ataktischem Polypropylen wurden maximal 1,8 Gew.-% Carbamatgruppen in das Polymere eingebaut. Die Mechanismen der beiden Reaktionstypen werden diskutiert.
    Notizen: Atactic polypropylene was functionalized by reaction with dicumyl peroxide (8 wt.-%) and allyl compounds (8 wt.-%) such as eugenol methylether, allylphenylether, allylurea, N-allylthiourea, diethyl allylmalonate, N-allylaniline at 170°C. Using tert-butyl azidoformate carbamate groups (1.8 wt.-%) were attached to atactic polypropylene. The mechanism of both types of reactions is discussed.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1987.051500101
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  • 77
    Digitale Medien
    Digitale Medien
    Effect of hydrostatic pressure on the electrical conductivity of FEF carbon black-loaded sbr vulcanizates (1987)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 150 (1987), S. 21-32 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Es wurde die elektrische Leitfähigkeit von Styrol-Butadien-Kautschuk (SBR-1502), der mit unterschiedlichen Konzentrationen von sehr schnell spritzbarem Furnace-Ruß (70, 80, 90 und 100 phr) beladen war, untersucht. Auf der Basis des Modells von Holm wurde eine qualitative Beschreibung für die elektrische Leitfähigkeit durch diese Verbundstoffe gesucht. Der Druckkoeffizient K wurde berechnet und zeigte eine starke Abhängigkeit von den Rußkonzentrationen.
    Notizen: The electrical conduction was investigated in styrene butadiene rubber (SBR-1502) loaded with different concentrations of fast extrusion furnace (FEF) black (70, 80, 90, and 100 phr). On the bases of Holm's model, a qualitative description for the electrical conduction through these composites was sought. The pressure coefficient K was calculated and found to be strongly dependent on the carbon black concentrations.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1987.051500103
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  • 78
    Digitale Medien
    Digitale Medien
    Characterization of low molecular compounds in dashboard foils by extraction, preparative high performance liquid chromatography, and IR-spectroscopy (1987)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 150 (1987), S. 13-19 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Es wird ein Verfahren zur Bestimmung der niedermolekularen Anteile von Instrumententafel-Folien beschrieben. Die Lösungsmittel-Extrakte der Folien werden mit Hilfe der präparativen Umkehr- bzw. Normalphasen-HPLC fraktioniert und die Fraktionen über ihre IR-Spektren charakterisiert. Vorzüge und Nachteile beider Verfahren werden diskutiert.
    Notizen: A procedure to obtain information concerning the low molecular weight compounds of dashboard foils is described. Solvent extracts of the foils were fractionated by preparative reversed or normal phase HPLC, respectively. The fractions were characterized by their infrared spectra. The benefits and the shortcomings of the two methods are discussed.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1987.051500102
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  • 79
    Digitale Medien
    Digitale Medien
    Oberflächenstrukturierung polymerer Fasern durch UV-LaserbestrahlungTeil 2 cf. Lit.1.. 3. Synergetisches Modell für das Entstehen der OberflächenstrukturenAuszug aus der Dissertation von T. Bahners, Universität Duisburg 1987. (1987)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 151 (1987), S. 39-47 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: A synergetic model is proposed for the development of the surface structure on UV-Laser irradiated polymers and especially synthetic fibres. It is suggested that thermal contributions to the UV-laser-polymer-interaction produce a very thin, highly heated layer of molten material at the ablation limit. The formation of the typical surface structure is then thought to be caused by Marangoni-convection and shrinkage because of intrinsic stress. The parameters of the effect therefore are the absorption coefficient for the corresponding laser wavelength as a measure of the thickness of the molten layer and the existence of the shrinking behaviour.
    Notizen: Ein synergetisches Modell wird vorgeschlagen für die Entstehung der Oberflächenstruktur von UV-laserbestrahlten Polymeren und speziell Synthesefasern. Dabei wird angenommen, daß durch thermische Beiträge zur UV-Laser-Polymer-Wechselwirkung eine sehr dünne, hocherhitzte Schmelzschicht an der Ablationsgrenze entsteht. Das Zusammenwirken von Marangoni-Konvektion und Schrumpfverhalten aufgrund innerer Spannungen ist dann für das Entstehen der typischen Struktur verantwortlich. Parameter für das Auftreten des Effekts sind hierbei der Absorptionskoeffizient für die jeweilige Wellenlänge, der die Dicke der Schmelzschicht bestimmt, sowie die Existenz des Schrumpfes.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1987.051510103
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  • 80
    Digitale Medien
    Digitale Medien
    Oxygen transport and surface active properties of silicone containing copolymers of methyl methacrylate IIPart I cf. lit9. (1987)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 151 (1987), S. 69-83 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Es wurden neue organofunktionelle Siloxane aus γ-Methacryloxypropyltrimethoxysilan (MPTMS) durch Umesterung von Methoxygruppen mit linearen höheren Alkoholen, Etheralkoholen und α-Hydroxysäuren hergestellt. Die Faktoren die die Substitutionsverhältnisse beeinflussen, wurden bestimmt.Diese Siloxane wurden mit Methylmethacrylat (MMA) copolymerisiert und mit Ethylenglykoldimethacrylat vernetzt, um den Einfluß der substituierten Gruppen auf den Sauerstoffpermeabilitätskoeffizienten (Pd) und die Eigenschaften der freien Oberflächenenergie der resultierenden Polymeren zu prüfen.Die Substitution der Sauerstoff enthaltenden polaren Gruppen erniedrigte die Sauerstoffdurchlässigkeit wegen der Wechselwirkungen zwischen den polaren Gruppen, die das freie Volumen erniedrigen. Diese Gruppen jedoch erhohten die polare Komponente der freien Oberflächenenergie (γPS) und somit die gesamte freie Oberflgchenenergie (γS). Die Hydrophilie der Carbitol und 2-Ethoxyethanol enthaltenden Siloxan-Methylmethacrylat-Copolymeren macht sie fur biomedizinische Anwendungen geeignet.
    Notizen: New organofunctional siloxanes from γ-methacryloxypropyltrimethoxysilane (MPTMS) were synthesized by transesterification of methoxy groups with linear high alcohols, ether alcohols, and α-hydroxyacids. The factors affecting the substitution ratios were determined.These siloxanes were copolymerized with methyl methacrylate (MMA), crosslinked with ethylene glycol dimethacrylate (EGDM) in order to examine the effect of substituted groups to the oxygen permeability coefficient (Pd) and surface free energy properties of the resultant copolymers.The substitution of the oxygen containing polar groups decreased the oxygen permeability due to the interactions between polar groups decreasing the free volume. However, these groups increased the polar component of surface free energy (γSP) and thus total surface free energy (γS). The hydrophilicity of the carbitol and 2-ethoxyethanol containing siloxane-MMA copolymers was found to be suitable for biomedical applications.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1987.051510105
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  • 81
    Digitale Medien
    Digitale Medien
    Mitteilungen (1987)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 151 (1987), S. 275-275 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1987.051510108
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  • 82
    Digitale Medien
    Digitale Medien
    A model for predicting elongational viscosity of polymer blends (1987)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 151 (1987), S. 95-101 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Es wird ein Modell vorgeschlagen, nach dem die Dehnungsviskosität von Blends mit der Theorie des Freien Volumens so korreliert werden kann, daß die Dehnungsviskosität eines Blends für jede Zusammensetzung aus den Dehnungsviskositäten und dem Gewichtsbruch der Komponenten bestimmt werden kann. Die Voraussagen des Modells wurden an experimentellen Daten in vier Fällen überprüft.
    Notizen: A model has been proposed to correlate the elongational viscosity of blends with the free volume theory so that the elongational viscosity of a blend at any composition can be determined from the elongational viscosity and the weight fractions of the individual components. The predictions of the model are compared with experimental data in four cases and found to give reasonable good agreement.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1987.051510107
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  • 83
    Digitale Medien
    Digitale Medien
    Synthesis and thermal studies of bisitaconimide-methacrylic acid copolymers (1987)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 152 (1987), S. 21-31 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Ein Copolymeres aus 3,3′-Bisitaconimido-m,m′-diphenylsulfon und Methacrylsäure wurde in einer radikalischen Polymerisation hergestellt. Das Copolymere wurde charakterisiert und die Copolymerisationsparameter ermittelt. Die durch drei verschiedene Methoden erhaltenen Reaktivitätsverhältnisse stimmen gut überein und lassen auf ein alternierendes Copolymeres schließen. Der thermische Abbau des Bisitaconimidhomopolymeren und des Copolymeren wurden verglichen und das thermische Verhalten diskutiert. Die Aktivierungsenergien für die verschiedenen Stufen des thermischen Abbaus des Homo- und des Copolymeren wurden durch Coats-Redfarn-Diagramme ermittelt.
    Notizen: A copolymer of 3,3′-bisitaconimido-m,m′-diphenyl sulfone and methacrylic acid was synthesized by free radical polymerization. The copolymer was characterized and the copolymerization parameters were evaluated. The reactivity ratios determined by three different methods were in good agreement and the values suggest an alternating copolymer. The thermal degradation of the bisitaconimide homopolymer and the copolymer were compared and the structural implications on the thermal behaviour are discussed. The activation energies for the different stages of thermal decomposition of both the homopolymer and the copolymer were evaluated from the Coats-Redfarn plots.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1987.051520103
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  • 84
    Digitale Medien
    Digitale Medien
    Untersuchungen zur thermodynamischen verträglichkeit von polyethylen hoher dichte (HD PE) und polyethylen niederer dichte (LD PE) in schmelzezustand, II. Die spezifische freie mischungsenthalpie (1987)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 152 (1987), S. 15-20 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: The parameters of solubility of HD PE and LD PE were used to calculate the Flory-Huggins-interaction parameter χ12 and, from this, the specific free mixing enthalpy ΔGm/V was determined according to Flory-Huggins for a system of these components. The diffusion rate of the PE molecules was estimated using the reptation model and the Einstein relation.The motive power of diffusion is proportional to the specific free mixing enthalpy. The results show that diffusion controlled segregation does not run in a HD PE/LD PE blend in the state of melt. This means that the morphology of polyethylene blends is only determined by mixing conditions in connection with the flow properties of components.
    Notizen: Aus den Löslichkeitsparametern von HD PE und LD PE wurde ihr temperaturabhängiger Flory-Huggins-Wechselwirkungsparameter χ12 und daraus wiederum nach Flory-Huggins die spezifische freie Mischungsenthalpie ΔGm/V eines HD PE/LD PE-Systems berechnet. Unter Zuhilfenahme des „reptation“-Modells und der Einstein-Relation wurde die Diffusionsgeschwindigkeit der PE-Moleküle abgeschätzt. Die Triebkraft dieser Diffusion ist proportional der spezifischen freien Mischungsenthalphie. Die Ergebnisse zeigen, daß diffusionskontrollierte Entmischungserscheinungen in einer HD PE/LD PE-Mischung im Schmelzezustand nicht ablaufen. Das bedeutet, daß die Morphologie der Mischungen im Schmelzezustand nur durch die Mischbedingungen im Zusammenspiel mit den Fließeigenschaften der Komponenten festgelegt wird.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1987.051520102
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  • 85
    Digitale Medien
    Digitale Medien
    Influence of synthesis conditions of porous copolymers of 1,4-di(methacryloyloxymethyl)-naphthalene with divinylbenzene on their structure, 2Part 1 cf. lit.7.. Influence of diluent composition (1987)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 152 (1987), S. 33-39 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Es wurde der Einfluß der Lösungsmittelzusammensetzung aus Toluol und n-Decanol auf die innere Struktur poröser Copolymerer untersucht.Eine Serie von Copolymeren mit jeweils 50 mol-% 1,4-Di(methacryloyloxymethyl)-naphthalin (1,4-DMN) und Divinylbenzol (DVB) wurde in Anwesenheit unterschiedlicher Anteile Toluol in der Mischung mit n-Decanol hergestellt. Um den Einfluß der Toluolkonzentration auf die innere Struktur der porösen Polymeren zu bestimmen, wurden die spezifische Oberfläche, die Porengrößenverteilung sowie die Polarität des Quellungsmittels untersucht.
    Notizen: The influence of diluent composition on the internal structure of porous copolymers of 1,4-di(methacryloyloxymethyl)naphthalene (1,4-DMN) and divinylbenzene (DVB) was studied.A set of copolymers containing 0.5 mole fraction of 1,4-DMN and 0.5 mole fraction of DVB obtained in the presence of various amounts of toluene in the mixture with n-decanol was investigated. In order to establish the influence of toluene concentration on the internal structure of 1,4-DMN and DVB copolymers, surface areas, pore size distributions, and polarities of sorbents were investigated.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1987.051520104
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  • 86
    Digitale Medien
    Digitale Medien
    Untersuchungen zur thermodynamischen verträglichkeit von polyethylen hoher dichte (HD PE) und polyethylen niederer dichte (LD PE) im schmelzezustand, I. Die bestimmung der löslichkeitsparameter (1987)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 152 (1987), S. 1-13 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: The solubility parameters of HD PE and LD PE above crystallization temperatures were determined on the basis of gas chromatographical retention data. The method of inverse gas chromatography was used. It showed that the solubility parameters of the types of polyethylene investigated are nearly equal within the margin of error. From the dependence of the solubility parameters on the temperature follows that the thermodynamical behaviour of the polyethylene components in mixtures is determined by their different free volumes.
    Notizen: Für HD PE und LD PE wurden oberhalb der Kristallisationstemperaturen die Löslichkeitsparameter auf der Basis gaschromatographischer Retentionsdaten bestimmt. Als Meßverfahren wurde die Methode der Inversen Gaschromatographie angewendet. Es zeigte sich, daß die Löslichkeitsparameter der untersuchten Polyethylentypen innerhalb der Fehlergrenzen nahezu gleich sind. Aus der Beschreibung der Temperaturabhängigkeit der Löslichkeitsparameter folgt, daß das thermodynamische Verhalten der Polyethylenkomponenten in Mischungen durch ihre unterschiedlichen freien Volumina determiniert ist.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1987.051520101
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  • 87
    Digitale Medien
    Digitale Medien
    Effect of the structure of slightly crosslinked polyurethanes on their thermal stability (1987)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 152 (1987), S. 41-53 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Die schwachvernetzten Polyurethane mit Allophanat- und C—C - Bindungen wurden durch die Reaktion von 4,4′-Diphenylmethandiisocyanat mit einer Poly(ethylenadipat)/Poly(ethylenmaleat)-Mischung sowie mit einer Mischung aus Terephthal-Adipinsäure-Copolyesterdiol und niedermolekularen Diolen hergestellt.Die Ergebnisse der isothermen und dynamischen thermischen Analyse in inerter Atmosphäre zeigen, daß die thermische Stabilität der Polyurethane von der Vernetzungsdichte und der chemischen Struktur der Vernetzungsbindungen und der Hart-Segmente unabhängig ist.
    Notizen: Polyurethanes slightly crosslinked with allophanate and C—C linkages have been prepared by reaction of 4,4′-diphenylmethane diisocyanate with poly(ethylene adipate) and poly(ethylene maleate) as well as with terephthalic-adipic copolyesterdiol and some low molecular diols.Data obtained from isothermal and dynamic thermogravimetric analysis carried out in an inert atmosphere indicate that the thermal stability of polyurethanes is independent on the crosslinking density and the structural characteristics of crosslinks and hard segments.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1987.051520105
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  • 88
    Digitale Medien
    Digitale Medien
    Reaction of poly(vinyl alcohol) with n-butyl isocyanate. Chemical hydrolysis of the resulting polymers (1987)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 152 (1987), S. 79-91 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Diese Untersuchung befaßt sich mit einigen kinetischen Merkmalen der Reaktion von n-Butylisocyanat mit Polyvinylalkohol ohne jeden Katalysator und unter Verwendung von Triethylendiamin als Katalysator. Die Struktur der resultierenden Polymeren wurde mit Hilfe der IR-, 1H-, und 13C-NMR-Spektroskopie und chemischer Analyse ermittelt. Es wurden Vinylalkohol-Vinylbutylurethancopolymere (VAL-VBU) erhalten. Es ergab sich eine lineare Abhängigkeit der Reaktionsgeschwindigkeit von Polymer-, n-Butylisocyanat- und Triethylendiaminkonzentration. Die Reaktionsgeschwindigkeitskonstante nimmt mit zunehmender Reaktionszeit ab. Das kann mit der sterischen Hinderung durch die Urethangruppen, die entlang der Polymerkette eingebaut sind, erklärt werden. Die Aktivierungsenergie ergab sich zu 49,9 kJ/mol. Eine kinetische Untersuchung der homogenen Hydrolyse von VAL-VBU-Copolymeren wurde durchgefilhrt als Funktion der Basenkonzentration, der Temperatur und des VBU Gehalts. Es zeigte sich, daß die homogene Hydrolyse als Reaktion 1 . Ordnung verliluft, sowohl im Hinblick auf die Hydroxylionen als auch auf den VBU-Gehalt. Die Aktivierungsenergie filr die basenkatalysierte Hydrolyse betragt 79,3 kJ/mol. Die heterogene Hydrolyse von VAL-VBU-Copolymeren im basischen Medium zeigte, daß keine Hydrolyse unter diesen Bedingungen stattfand.
    Notizen: This study is concerned with some kinetic features of the reaction of n-butyl isocyanate with poly(vinyl alcohol) without any catalyst and using triethylene diamine as catalyst. The structure of the resulting polymers was determined by means of IR, 1H- and 13C-NMR spectroscopy as well as by chemical analysis. Vinyl alcohol-vinyl butyl urethane (VAL-VBU) copolymers were obtained. It has been found a linear dependence of reaction rate on polymer, n-butyl isocyanate, and triethylene diamine concentrations. Reaction rate constant decreases as reaction time increases. It can be explained by steric hindrance phenomena due to urethane groups incorporated along the polymeric chain. The activation energy was found to be 49.9 kJ/mol. A kinetic study of the homogeneous hydrolysis of VAL-VBU copolymers has been made as a function of the base concentration, the temperature, and the VBU content. The homogeneous hydrolysis was found to be first order with respect to both hydroxyl ion and VBU contents. The activation energy for the base catalyzed homogeneous hydrolysis was found to be 79.3 kJ/mol. The heterogeneous hydrolysis of VAL-VBU copolymers in basic medium showed that no hydrolysis takes place under the conditions employed.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1987.051520108
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  • 89
    Digitale Medien
    Digitale Medien
    Studies on 50/50 natural rubber/styrene butadiene copolymer blendDedicated to Prof. R. Anantaraman on his 61st birthday (1987)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 152 (1987), S. 107-119 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Ein mit Ruß gefülltes 50/50 NR/SBR-Blend (Naturkautschuk/Styrol-Butadien-Copolymer) wurde unter Verwendung verschiedener konventioneller Vernetzungssysteme, die durch unterschiedliche Schwefel- und Beschleunigeranteile gekennzeichnet sind, vulkanisiert. Die Vulkanisationscharakteristiken und die Eigenschaften der Vulkanisate wurden verglichen. Das Ausmaß und die Qualität der Vernetzungsstellen wurden für jeden Fall durch chemische Testmethoden ermittelt, um sie mit den Vulkanisateigenschaften zu vergleichen.
    Notizen: A carbon black filled 50/50 natural rubber (NR)/styrene-butadiene rubber (SBR) blend is vulcanized using several conventional curing systems designed by varying the amounts of sulphur and accelerator. The cure characteristics and the properties of the vulcanizates are compared. The quantity and quality of crosslinks in each case are evaluated by chemical probes to correlate them with the vulcanizate properties.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1987.051520110
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  • 90
    Digitale Medien
    Digitale Medien
    Solution properties of ultrahigh molecular weight polymers, 15Part 14: Rev. Roum. Chim. 31 (1986) 995.. A viscometric study of poly(isobutyl methacrylate) in different solvents (1987)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 152 (1987), S. 121-131 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Die Arbeit stellt eine Erweiterung der vorhergehenden Untersuchungen hinsichtlich synthetischer Polymerer mit sehr großen Molekularmassen dar. Die Grenzviskositäten und die Viskositätskonstanten von Poly(isobutylmethacrylat) wurden mit den Methoden von Huggins, Kraemer, Martin, Schulz-Blaschke und Fedors in CCl4 und C6H6 bei 25°C erhalten. Es wurde beobachtet, daß die Methode von Fedors nicht sehr sensibel ist bei den möglichen Fehlern, die bei der Bestimmung der relativen Viskositäten in konzentrierten Bereichen auftreten. Diese Methode führt zu Grenzviskositäten, die nahe den mittleren Werten liegen, die mit den anderen fünf Methoden und der Sakai-Mitteilung erhalten wurden. Außerdem wurden die Umwandlungskonzentrationen, die die verdünnt-halbverdünnten Bereiche trennen, sowie die Mark-Houwink-Konstanten bestimmt.
    Notizen: The paper extends previous studies on ultrahigh molecular weight synthetic polymers. The intrinsic viscosities and the viscosity constants of poly(isobutyl methacrylate) fractions were obtained by the methods of Huggins, Kraemer, Martin, Schulz-Blaschke, and Fedors in CCl4 and C6H6 at 25°C. It was observed that the method of Fedors is not very sensitive to the possible errors appearing in estimating the relative viscosities in higher concentration domains. This method yields intrinsic viscosity values close to the mean values obtained from the other five methods and to the values calculated according to the averaging procedure suggested by Sakai. The transition concentrations separating the concentration domains (diluted-semidiluted) and the Mark-Houwink constants were obtained.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1987.051520111
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  • 91
    Digitale Medien
    Digitale Medien
    Radiation initiated grafting of styrene and methyl methacrylate onto wool (1987)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 152 (1987), S. 133-147 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Die strahleninduzierten Pfropfungen der hydrophoben Monomeren Styrol und Methylmethacrylat sowohl auf gefärbtem Teppich als auch auf gefärbter und ungefärbter Wolle werden ausgeführt. Betont wird die Notwendigkeit des Quellens zur Erzielung einer merkbaren Pfropfausbeute. Es wurde gefunden, daß die Pfropfungsgeschwindigkeit für die gefärbte Wolle wie auch für den Teppich kleiner ist als für die ungefärbte Wolle. Diese Ergebnisse werden erklärt mit der abschirmenden Wirkung der aromatischen Farbstoffmolekülteile. Bei geringen Monomerkonzentrationen wurde ein Umsatz von 97% bezogen auf die eingesetzte Monomermenge gefunden, da die als Nebenreaktion ablaufende Homopolymerisation in Gegenwart von Radikalabfängern fast vernachlässigbar ist. Eine angemessene Hydrophobie wurde erreicht bei mit ca. 80% Styrol und ca. 150% Methylmethacrylat gepfropfter Wolle.
    Notizen: Radiation initiated grafting of hydrophobic monomers styrene and methyl methacrylate onto wool (dyed and undyed) and dyed carpet has been carried out. The importance of swelling in obtaining appreciable amounts of grafting has been stressed. The rate of grafting with dyed wool and carpet is found to be less than for undyed wool and the results are explained on the basis of protection offered by aromatic moieties of the dye. Efficiency of monomer utilization has been found to be as high as 98% at low concentrations of the monomer since the accompanying (parasitic) homopolymerisation is almost negligible in the presence of scavengers. Reasonable hydrophobicity is achieved in ca. 80% styrene grafted and ca. 150% methyl methacrylate grafted wool.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1987.051520112
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  • 92
    Digitale Medien
    Digitale Medien
    Fließverhalten von Mischungen aus chloriertem Polyethylen und Polymethylmethacrylat (1987)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 155 (1987), S. 163-175 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: The flow behavior of bicomponent polymer blends of chlorinated polyethylene (PEC) and poly(methyl methacrylate) (PMMA) is presented in the form of flow curves. The relations between the rheological measurements and the morphology are discussed. The blends (PEC/PMMA, chlorinated up to 40 wt.-%) show the characteristic behavior of incompatible systems, some of them with a second highly dispersed phase. In addition a system of PE/PMMA is examined, the PE being the raw material of the PEC. The influence of the chlorination on flow behavior and the biphase structure is obvious.
    Notizen: Das Fließverhalten von Mischungen aus chloriertem Polyethylen (PEC) und Polymethylmethacrylat (PMMA) wird in Form von Fließkurven dargestellt. Die Ergebnisse der rheologischen Messungen werden anhand der sich ausbildenden Morphologie diskutiert. Es zeigt sich, daß die untersuchten Mischungen aus PEC/PMMA mit Chlorierungsgraden bis 40 Gew.-% Cl das charakteristische Verhalten von unverträglichen (2-phasigen) Mischungen mit teilweise fein dispergierter zweiter Phase liefern. Vergleichend wird die Stoffkombination PE/PMMA betrachtet, wobei die PE-Sorten jeweils die unchlorierten Ausgangsprodukte darstellen. Der Einfluß der Chlorierung auf das Fließverhalten und die zweiphasige Struktur ist deutlich festzustellen.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1987.051550114
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  • 93
    Digitale Medien
    Digitale Medien
    Preparation and properties of selectively p-chlorinated polystyrene (1987)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 155 (1987), S. 191-197 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Polystyrol wurde in Lösung mit SbCl3 als Katalysator und 10-Trifluoracetylphenothiazin als Cokatalysator chloriert. Dabei wurde ein Polymeres erhalten, das durch die Formel . beschrieben werden kann. Die aromatische Substitutionsreaktion (x 〉 1) erfolgt vorwiegend and der para-Position; das Verhältnis der para- zur ortho-Chlorierung beträgt 10 - 12. Die Grenzviskositätszahl bei 30°C einer toluolischen Polymerlösung nimmt mit dem Chlorgehalt x des Polymeren ab. Der Brechungsindex nD wächst mit x. Der nD - Wert eines Polymeren mit 25,05 Gew.-% Chlor (x ≃ 1) beträgt 1,6041.
    Notizen: Polystyrene has been chlorinated in the liquid phase by SbCl3 catalyst combined with 10-trifluoroacetylphenothiazine to afford a polymer, which is represented by the formula . The aromatic substitution reaction (x 〉 1) occurs predominantly at the p-position, the ratio of p- to o-chlorination being 10-12. The intrinsic viscosity of the toluene solution at 30°C decreases with content of chlorine, x. The refractive index, nD, increases with x. The nD value of a 25.05% chlorine-containing polymer (x ≃ 1) is 1.6041.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1987.051550116
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  • 94
    Digitale Medien
    Digitale Medien
    Interactions of polymer backbones and complexation of polychelatogens with methylthiourea ligands in aqueous solutionDedicated to Prof. Dr. E. Bayer on the occasion of his 60th birthday (1987)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 155 (1987), S. 151-161 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Die Wechselwirkungen des Polymergerüsts und die Komplexbildung mit einer Reihe von Schwermetallen wurde für die Methylthioharnstoff als Liganden tragenden Basispolymeren Poly(ethylenimin), Poly(vinylpyrrolidinon) und Poly(acrylamid) in Abhängigkeit vom pH-Wert untersucht.Retentionsstudien in wässriger Lösung unter Verwendung von Membranfiltration wurden zur Bewertung der Wechselwirkungen zwischen Metallionen und Makromolekülen in Abhängigkeit vom pH-Wert herangezogen. Es wurde für die Ionen Na, Co, Ni, Cu, Zn, Cd, Hg, Fe gezeigt, daß die Wechselwirkung sowohl von der Art des Polymergerüsts als auch vom pH abhängt. Während die Retentionswerte von Copolymeren auf der Basis von Poly(ethylenimin) nur schwach vom pH beeinflußt wurden, zeigten die beiden anderen untersuchten Copolymeren eine starke Abhlngigkeit für die einzelnen Metalle. Es wurde eine vorherrschende Wirkung des funktionellen Liganden-Comonomeren hinsichtlich der Wechselwirkung im Vergleich zum Basismonomeren füur den größten Teil der untersuchten Metallionen gefunden.
    Notizen: The interactions of the polymeric backbone and complex formation with a series of metals were investigated for poly(ethyleneimine), poly(vinylpyrrolidinone), and poly-(acrylamide) as basis polymers with methylthiourea as ligand. Retention studies by application of membrane filtration of aqueous solutions were used for the evaluation of interaction between the metal ions and macromolecules as function of pH. It was shown for the Na, Co, Ni, Cu, Zn, Cd, Hg, Fe ions that the interaction depends both on the type of polymer backbone and the pH.Whereas for poly(ethyleneimine)-based copolymers the retention data were influenced only slightly by pH, the two other copolymers investigated showed a strong pH dependency for the individual metals. A dominating effect of the functional ligand comonomer in terms of the interaction over the basis monomer was observed for the majority of metal ions investigated.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1987.051550113
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  • 95
    Digitale Medien
    Digitale Medien
    The laser flash-initiated polymerization as a tool of evaluating (individual) kinetic constants of free radical polymerization, 3Part 2: cf. lit6.. Information from degrees of polymerization (1987)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 155 (1987), S. 177-190 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Für die in einer pseudostationären Laserpuls-induzierten Photopolymerization entstehenden Polymeren werden Gleichungen für die Zahlen- und den Masenmittelwert der Polymerisationsgrade abgeleitet. Der Kettenabbruch kann dabei, bei vernachlässigbarer Kettenübertragun, in einer Disproportionierung oder einer Rekombination bestehen. Die Analyse der bei verschiedenen Pulsabständen resultierenden Polymerisationsgrade ermöglicht die Bestimmung der Wachstumskonstanten (kp) und des Produkts kt ρ (kt = Geschwindigkeitskonstante des bimolekularen Kettenabbruchs, ρ = Konzentration der pro Laserblitz produzierten Primärradikale). Da überdies k2/kt%/& aus der (pseudostätionaren) Polymerisationsgeschwindigkeit und dem Massenmittel-Polymerisationsgrad des im selben Experiment gebildeten Polymeren berechnet werden kann, ist es, zumindest im Prinzip, möglich, eine vollstähdige Auflösung in die individuellen GröBen kp, kt und ρ zu erreichen. Anhand eines Beispiels läßt sich zeigen, daß die auf diesem Weg für die Styrolpolymerisation bei 25°C gewonnenen Daten gut mit jenen übereinstimmen, die mittels anderer Methoden erhalten wurden.
    Notizen: Equations are derived for the number average and the weight average degrees of polymerization for the polymer forming in a laser-initiated photo-polymerization under pseudostationary conditions when termination occurs by disproportionation or recombination and if chain transfer is negligible. Analysis of the degrees of polymerization at various pulse separations leads to information on the rate coefficient of propagation (kp) and on the product kt ρ (kt = rate coefficient of bimolecular chain termination, ρ = concentration of primary radicals produced in each flash). As kp2/kt may be evaluated from the rate and the weight average degree of polymerization P̄w of a single pseudostationary experiment, at least in principle, a complete resolution into individual constants may be achieved. It is demonstrated in an example that the data obtained in this way for the polymerization of styrene at 25°C are well consistent with those originating from other methods.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1987.051550115
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  • 96
    Digitale Medien
    Digitale Medien
    Mitteilungen (1987)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 155 (1987), S. 199-200 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1987.051550117
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  • 97
    Digitale Medien
    Digitale Medien
    The role of the stress resultant in determining mechanical equilibria of superhelical DNA (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 9-15 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360260105
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  • 98
    Digitale Medien
    Digitale Medien
    A model of the hydrodynamic behavior of irradiated DNA: Dependence on molecular conformation (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 59-82 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The model presented here describes the DNA viscosity and viscoelastometric responses to ionizing radiation-induced molecular breakdown. Four DNA conformations are considered: (1) linear chain, (2) relaxed circle, (3) supercoiled circle, and (4) supercoiled linear. The model includes the systems of differential equations for calculating the size distributions of DNA molecules as functions of dose. Thedistributions are used in the usual hydrodynamic formulae for heterogeneouspopulations of polymer molecules. The sensitivity of viscoelastometry for the estimation of D37 is better than that of viscometry. The model predicts a considerable difference between the radiation responsesof linear and circular DNAs. The prediction is confirmed by experimental data for T4 DNA [C. S. Lange et al. (1984) Rad. Res. 100, 1-15] and E. coli DNA [S. E. Bresler et al. (1984) Biophys. J. 45, 749-754]. Thus, ionizing radiation can be used to determine the original conformation of DNA molecules.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360260109
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  • 99
    Digitale Medien
    Digitale Medien
    Proton polarizability and proton transfer in histidine-phosphate hydrogen bonds as a function of cations present: Ir investigations (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 95-108 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: (L-His)n- dihydrogen phosphate systems are studied by ir spectroscopy in the presence of various cations and as a function of the degree of hydration. Ir continua indicate that (I) OH … N ⇌ O-…H+N (IIR) hydrogen bonds are formed and that these bonds show high proton polarizability, which increases from the Li+ to the K+ system. In the K+-system, His-Pi-Pi chains are formed, showing particularly high proton polarizability due to collective proton motion within both hydrogen bonds. The OH N ⇌ O-…H-N equilibria are determined from ir bands. With the Li+ system, 55% of the protons are present at the histidine residues; this percentage is smaller with the Na+ system (41%), and amounts to only 32% with the K+ system. With the increasing degree of hydration the removal of the degeneracy of νas-PO2-3 vanishes, indicating loosening of the cations from the phosphates. Nevertheless, the hydrogen bond acceptor O atom becomes more negative; a shift of the equilibrium to the right is observed in the OH… N ⇌ O-…H+N bond. This is explained by the strong interaction of the dipole of the hydrogen bonds with the water molecules. All these results show that protons can be shifted easily in these hydrogen bonds due to their high proton polarizability. The transfer equilibria can be controlled easily by local electrical fields. In addition, these results may be of significance when phosphates interact with proteins.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360260111
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  • 100
    Digitale Medien
    Digitale Medien
    The hydrogen bonding of cytosine with guanine: Calorimetric and 1H-NMR analysis of the molecular interactions of nucleic acid bases (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 591-603 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The enthalpy of hydrogen-bond formation between guanine (G) and cytosine (C) in o-dichlorobenzene and in chloroform at 25°C has been determined by direct calorimetric measurement. We derivatized 2′-deoxyguanosine and 2′-deoxycytidine at the 5′- and 3′-hydroxyls with triisopropylsilyl groups; these groups increase the solubility of the nucleic acid bases in nonaqueous solvents. Such derivatization also prevents the ribose hydroxyls from forming hydrogen bonds. Consequently, hydrogen-bond formation in our system is primarily between the bases, and to a lesser extent, between base and solvent, and can be measured directly with calorimetry. To obtain the data on base-pair formation, we first took into account the contributions from self-association of each base, and where possible, have determined the ΔH of self-association. From isoperibolic titration calorimetry, our measured ΔH of C2 formation in chloroform is -1.7 kcal/mol of C. Our measured ΔH of C:G base-pair formation in o-dichlorobenzene is -6.65 ± 0.32 kcal/mol. Since o-dichlorobenzene does not form hydrogen bonds, the ΔH of C:G base-pair formation in this solvent represents the ΔH of the hydrogen-bonding interaction of C with G in a nonassociating solvent. In contrast, our measured ΔH of C:G base-pair formation in chloroform is -5.77 ± 0.20 kcal/mol; thus, the absolute value of the enthalpy of hydrogen bonding in the C:G base pair is greater in o-dichlorobenzene than in chloroform. Since chloroform is a solvent known to form hydrogen bonds, the decrease in enthalpic contribution to C:G base pairing in chloroform is due to the formation of hydrogen bonds between the bases and the solvent. The ΔH of hydrogen bonding of G with C reported here differs from previous indirect estimates: Our measurements indicate the ΔH is 50% less in magnitude than the ΔH based on spectroscopic measurements of the extent of interaction. We have also observed that the enthalpy of hydrogen bonding of C with G in chloroform is greater when G is in excess than when C is in excess. This increased heat is due to the formation of C:Gn 〉 1 complexes that we have observed using 1H-nmr. Although C:G2 structures have previously been observed in triple-stranded polymeric nucleic acids, higher order structures have not been observed between C and G monomers in nonaqueous solvents until now. By using monomers as a model system to investigate hydrogen-bonding interactions in DNA and RNA, we have obtained the following results: A direct measurement of the ΔH of hydrogen bonding in the C:G complex in two nonaqueous solvents, and the first observation of C:Gn 〉 1 complexes between monomers. These results reinforce the importance of hydrogen bonding in the stabilization of various nucleic acid secondary and tertiary structures.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360260411
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