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  • 1995-1999  (5,624)
  • 1995  (5,624)
  • Polymer and Materials Science  (4,710)
  • Engineering General  (737)
  • Rat  (177)
  • Nuclear reactions
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  • 1995-1999  (5,624)
Year
Keywords
  • 101
    Electronic Resource
    Electronic Resource
    Thermal images of somatic sensory cortex obtained through the skull of rat and gerbil (1995)
    Springer
    Experimental brain research 106 (1995), S. 7-18 
    Details
    ISSN: 1432-1106
    Keywords: Infrared image ; Somatosensory cortex ; Skull ; Rat ; Gerbil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Infrared images of the skull surface were obtained in urethane-anesthetized rats and gerbils before, during and after mechanical stimulation of the face and mystacial vibrissae on one side. Areas of increased temperature on the skull, localized mainly over the face area of the primary somatosensory cortex contralateral to the side of stimulation, appeared within 4–5 s after the onset of stimulation. Rarely, such temperature change was recorded bilaterally. Temperatures did not remain high on the intact skull in rats, but fell to baseline within minutes after stimulus onset regardless of stimulus duration. In rats in which the skull had been thinned and in gerbils with intact skull, temperatures remained elevated during the course of stimulation. We were unable to resolve the activation of individual vibrissae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00241352
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  • 102
    Electronic Resource
    Electronic Resource
    A survey of spinal dorsal horn neurones encoding the spatial organization of withdrawal reflexes in the rat (1995)
    Springer
    Experimental brain research 106 (1995), S. 19-27 
    Details
    ISSN: 1432-1106
    Keywords: Pain ; Nociception ; Sensorimotor integration ; Receptive field ; Somatosensory ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The withdrawal reflex pathways to hindlimb muscles have an elaborate spatial organization in the rat. In short, the distribution of sensitivity within the cutaneous receptive field of a single muscle has a spatial pattern that is a mirror image of the spatial pattern of the withdrawal of the skin surface ensuing on contraction in the respective muscle. In the present study, a search for neurones encoding the specific spatial input-output relationship of withdrawal reflexes to single muscles was made in the lumbosacral spinal cord in halothane/nitrous oxide-anaesthetized rats. The cutaneous receptive fields of 147 dorsal horn neurones in the L4-5 segments receiving a nociceptive input and a convergent input from A and C fibres from the hindpaw were studied. The spatial pattern of the response amplitude within the receptive fields of 118 neurones was quantitatively compared with those of withdrawal reflexes to single muscles. Response patterns exhibiting a high similarity to those of withdrawal reflexes to single muscles were found in 27 neurones located in the deep dorsal horn. Twenty-six of these belonged to class 2 (responding to tactile and nociceptive input) and one belonged to class 3 (responding only to nociceptive input). None of the neurones tested (n=20) with reflex-like response patterns could be antidromically driven from the upper cervical cord, suggesting that they were spinal interneurones. With some overlap, putative interneurones of the withdrawal reflexes to the plantar flexors of the digits, the plantar flexors of the ankle, the pronators, the dorsiflexors of the ankle, and a flexor of the knee, were found in succession in a mediolateral direction. It is concluded that neurones that are able to encode the specific spatial input-output organization of the withdrawal reflexes to single muscles do exist in the deep dorsal horn. Such reflex encoders appear to have a “musculotopic” organization. A hypothesis of the organization of the withdrawal reflex system is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00241353
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  • 103
    Electronic Resource
    Electronic Resource
    Raphespinal and reticulospinal neurons project to the dorsal vagal complex in the rat (1995)
    Springer
    Experimental brain research 106 (1995), S. 79-92 
    Details
    ISSN: 1432-1106
    Keywords: Autonomic ; Axon collaterals ; Medial tegmental field ; Motoneurons ; Respiratory ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Stimulation of the caudal raphe nuclei alters visceral functions. The caudal raphe nuclei project to the nucleus of the solitary tract, which receives the central terminations of vagal afferents and plays an important role in the central integration of autonomic activities. The caudal raphe nuclei also project to the somatic and preganglionic autonomixc motoneurons of the spinal cord. Diamidino yellow was injected into the nucleus of the solitary tract, and fast blue was injected into either the cervical, thoracic, or lumbar spinal cord. Large numbers of double-labeled neurons were present within the caudal raphe nuclei and the adjacent reticular formation of the medial tegmental field. This observation documents that individual raphespinal and reticulospinal neurons project an axon collateral to the nucleus of the solitary tract. These data demonstrate the anatomic substrate for global modulation of the autonomic motoneuron pool by the caudal raphe nuclei.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00241358
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  • 104
    Electronic Resource
    Electronic Resource
    Fictive motor activities in adult chronic spinal rats transplanted with embryonic brainstem neurons (1995)
    Springer
    Experimental brain research 106 (1995), S. 69-78 
    Details
    ISSN: 1432-1106
    Keywords: Neural transplantation ; Locomotion ; Paw shaking ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The present study was designed to examine the effects of an intraspinal transplantation of embryonic brainstem neurons on fictive motor patterns which can develop in hindlimb nerves of adult chronic spinal rats. Seventeen adult rats were spinalized at T8-9 level and, 8 days later, a suspension of embryonic cells obtained either from the raphe region (RR, n=8) or from the locus coeruleus (LC, n=9) was injected caudally (T12–13) to the cord transection. Eight control animals (control rats) were spinalized and injected with vehicle under the same conditions. One to three months later, the animals were decorticated and fictive motor patterns were recorded in representative hindlimb nerves. The data revealed that both control and grafted spinal rats could exhibit two distinctly different fictive motor patterns, one which could be associated with stepping and the other with hindlimb paw shaking. They further showed that following transplantation of embryonic RR or LC neurons the excitability of the spinal stepping generator was increased, whereas that of the spinal neural circuits which generate hindlimb paw shaking was not significantly affected. A histological analysis performed on the spinal cord segments below the transection revealed complete absence of serotonin and noradrenaline immunoreactivity in control spinal animals and, in both types of grafted rats, an extensive monoaminergic reinnervation with synaptic contacts between monoaminergic transplanted neurons and host interneurons and/or motoneurons. The possible mechanisms by which grafted monoaminergic neurons can influence the spinal motor networks are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00241357
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  • 105
    Electronic Resource
    Electronic Resource
    Astroglial responses in photochemically induced focal ischemia of the rat cortex (1995)
    Springer
    Experimental brain research 106 (1995), S. 1-6 
    Details
    ISSN: 1432-1106
    Keywords: Spreading depression ; GFAP ; Astrocytes ; Focal ischemia ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This study investigated astroglial responses after focal cerebral ischemia in the rat cortex induced by photothrombosis. Astrocyte activation was studied at various time points by immunocytochemistry for glial fibrillary acidic protein (GFAP) and vimentin (VIM). We found a dual astrocytic response to focal ischemia: In the border zone of the infarct, GFAP-positive astrocytes were present within 2 days and persisted for 10 weeks. These astrocytes additionally expressed VIM. Remote from the ischemic lesion, cortical astrocytes of the entire ipsilateral hemisphere transiently expressed GFAP, but not VIM, beginning on day 3 after photothrombosis. This response had disappeared on day 14. By recording DC potentials, five to seven spreading depressions (SD) could be detected on the cortical surface during the first 2 h after photothrombosis. Treatment with MK801, a non-competitive NMDA-receptor antagonist, completely abolished SD and remote ipsilateral astrocytic activation, while the reaction in the border zone of the infarct remained unchanged. Functionally, persistent astrocytosis around the infarct might be induced by leukocyte-derived cytokines, while NMDA-receptor-mediated SD might cause remote responses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00241351
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  • 106
    Electronic Resource
    Electronic Resource
    Intrinsic burst generation of preinspiratory neurons in the medulla of brainstem-spinal cord preparations isolated from newborn rats (1995)
    Springer
    Experimental brain research 106 (1995), S. 57-68 
    Details
    ISSN: 1432-1106
    Keywords: Respiratory rhythm ; Respiratory neurons ; Pacemaker neurons ; Perforated patch ; Nystatin ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In brainstem-spinal cord preparations isolated from newborn rats, intrinsic burst-generating properties of preinspiratory (Pre-I) neurons in the rostral ventrolateral medulla, which have been suggested to be primary respiratory rhythm-generating neurons, were studied by “perforated” whole-cell recordings using the antibiotic nystatin. Nystatin causes small pores to be formed in the cells, through which pass small monovalent ions. For blockade of chemical synaptic transmission, perfusate Ca2+ concentration was lowered to 0.2 mM and the Mg2+ concentration was increased to 5 mM. In Iow-Ca2+, high-Mg2+ solution (referred to here as “low Ca”), 10 of 55 Pre-I neurons generated rhythmic bursts (burst type), 14 fired tonically (tonic type), and 31 were silent (silent type). Burst-type neurons showed periodic depolarization of 5–12 mV in low Ca, at a rate of 12±6.5/min. Hyperpolarization of the membrane caused decrease in or disappearance of the periodic depolarization and prolongation of the cycle period. Thus, the burst generations were voltage dependent. The firing frequency of tonictype neurons was 2.3±1.6 Hz and was decreased by hyperpolarization. In 6 of these neurons, the firing patterns changed to burst patterns during continuous hyperpolarization. Membrane depolarization by continuous outward current injection into some silent-type neurons (3 of 11 tested) induced bursting activity. Activity of C4 and Pre-I neurons was completely silent with 0.1–1 μM tetrodotoxin (TTX) added to the standard perfusate. In low Ca, burst-type neurons (n=3) were also silent with 1 μM TTX perfusion. Inspiratory neurons either became silent (n=4) or fired tonically (n=1) in low Ca. The present study by “perforated” whole-cell recordings confirmed that some Pre-I neurons possess intrinsic burst-generating properties, which were not attributable to phasic synaptic inputs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00241356
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  • 107
    Electronic Resource
    Electronic Resource
    Cooperative effects of neuronal ensembles (1995)
    Springer
    Experimental brain research 106 (1995), S. 106-110 
    Details
    ISSN: 1432-1106
    Keywords: Spiking neural network ; Refractory period ; Phase transition ; Finite-size effect ; Hippocampal culture ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Electrophysiological properties of neurons as the basic cellular elements of the central nervous system and their synaptic connections are well characterized down to a molecular level. However, the behavior of complex noisy networks formed by these constituents usually cannot simply be derived from the knowledge of its microscopic parameters. As a consequence, cooperative phenomena based on the interaction of neurons were postulated. This is a report on a study of global network spike activity as a function of synaptic interaction. We performed experiments in dissociated cultured hippocampal neurons and, for comparison, simulations of a mathematical model closely related to electrophysiology. Numeric analyses revealed that at a critical level of synaptic connectivity the firing behavior undergoes a phase transition. This cooperative effect depends crucially on the interaction of numerous cells and cannot be attributed to the spike threshold of individual neurons. In the experiment a drastic increase in the firing level was observed upon increase of synaptic efficacy by lowering of the extracellular magnesium concentration, which is compatible with our theoretical predictions. This “on-off” phenomenon demonstrates that even in small neuronal ensembles collective behavior can emerge which is not explained by the characteristics of single neurons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00241360
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  • 108
    Electronic Resource
    Electronic Resource
    A behavioral model of excitotoxicity: retinal degeneration, loss of vision, and subsequent recovery after intraocular NMDA administration in adult rats (1995)
    Springer
    Experimental brain research 106 (1995), S. 93-105 
    Details
    ISSN: 1432-1106
    Keywords: Retina ; NMDA ; HRP ; Neurotoxicity ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To establish a new behavioral animal model of excitotoxicity, we injected adult rats intraocularly with a single dose of 2, 20, or 100 nmol of N-methyl-d-aspartate (NMDA). We quantified visual impairment by plotting the size of the visual field in which the rats successfully oriented towards a small, moving target. In comparison to the saline-injected (contralateral) control side, the side injected with 2 nmol of NMDA was not significantly impaired. When injected with higher doses, the rats were nearly blind immediately after surgery, with only about 20% (20 nmol NMDA) or 10% (100 nmol NMDA) of residual vision. Within about 3 weeks, however, visual performance returned to near-normal levels. Simultaneous intraocular administration of a non-competitive NMDA-antagonist, MK-801 (1 nmol), resulted in complete behavioral protection. NMDA administration led to a dose-dependent loss of cells within the ganglion cell layer, as assessed in whole-mounted retinae which were retrogradely labelled with horseradish peroxidase (HRP). Whereas 2 nmol of NMDA led to the loss of about 30% of retinal ganglion cells (RGCs), at higher NMDA doses only 13% of the RGCs survived. After the injection of 20 nmol of NMDA, large-diameter RGCs (〉22 μm) survived the lesion to a greater extent than small diameter cells (8–21 μm); at 100 nmol cells of all diameters were equally affected. The number of Nissl-stained cells with small diameters (〈11 μm), presumed to be displaced amacrine cells, was also affected by NMDA, although to a lesser degree. Analysis of behavioral performance (vision score) and the number of cells in the retina revealed a correlation of r=0.76 between visual performance and the number of HRP-filled RGCs immediately after surgery. Lower correlations were found between visual performance and cells stained with Nissl of diameters smaller than 11 μm (presumably displaced amacrine cells) or larger than 11 μm (presumed RGCs without retinofugal connections; r=0.55 and r=0.58, respectively). Because of the spontaneous recovery of vision, all correlations declined to values near 0 after 3 weeks. Thus, despite a dramatic loss of RGCs following NMDA administration, visual deficits recover significantly in adult rats within 2–3 weeks.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00241359
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  • 109
    Electronic Resource
    Electronic Resource
    Synaptic depression in visual cortex tissue slices: an in vitro model for cortical neuron adaptation (1995)
    Springer
    Experimental brain research 106 (1995), S. 145-155 
    Details
    ISSN: 1432-1106
    Keywords: Adaptation ; Depression ; LTD ; LTP ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Synaptic depression was assessed from intracellular recordings in cortical tissue slices. Evoked postsynaptic potentials exhibited synaptic depression with an exponential or double exponential decrease (time constants: 〈1–30 s) in amplitude during repetitive afferent stimulation by short trains of suprathreshold stimuli. Depressed synaptic responses recovered with an exponential time course (time constants: 10 s-8 min) during presentation of similar short trains of stimuli every 5 or 10 s. Cortical cells recorded extracellularly in cat visual cortex show similar time constants of response decrement during adaptation to moving stripes. Postsynaptic voltage- or ion-regulated conductances and chloride conductances do not appear to be involved in synaptic depression. Input resistance changes and effects of injection of chloride indicate a lack of GABAA receptor-mediated effects. Hyperpolarizing or depolarizing neurons, and pairing polarization with afferent stimulation, also did not affect synaptic depression. This distinguishes these processes from long-term depression and long-term potentiation. Our results suggest that the most likely mechanisms of synaptic depression and adaptation in cortical cells are presynaptic decrease in transmitter release and/or receptor desensitization. Short-term postsynaptic changes may also occur after synaptic depression.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00241364
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  • 110
    Electronic Resource
    Electronic Resource
    NMDA and non-NMDA receptors mediate taste afferent inputs to cortical taste neurons in rats (1995)
    Springer
    Experimental brain research 106 (1995), S. 391-402 
    Details
    ISSN: 1432-1106
    Keywords: Taste ; Insular cortex ; Excitatory amino acid receptor ; Iontophoresis ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Two main subclasses of ionotropic receptors for excitatory amino acids (EAAs), N-methyl-d-aspartate (NMDA) receptors and non-NMDA receptors, are involved in neurotransmission in the cortex of mammals. To examine whether EAAs are transmitters at the cortical taste area (CTA) in rats and to elucidate which types of the two ionotropic receptors operate at these synapses, we studied the effects of microiontophoretic administration of EAA antagonists on the responses of 64 taste cortical neurons to four basic taste stimuli in urethane-anesthetized rats. Both d-2-amino-5-phosphonovalerate (APV), a selective antagonist for NMDA receptors, and 6-cyano-7-nitro-quinoxaline-2,3-dione (CNQX), a selective antagonist for non-NMDA receptors, suppressed most of the taste responses. The percentage of neurons suppressed by APV (70.3%) was almost the same as that suppressed by CNQX (64.1%). These suppressive effects were independent of the effects of background discharges during the prestimulus, water-rinsing period. The percentage of neurons suppressed by the antagonists did not differ between any pairs of taste stimuli. The number of neurons possessing both receptors was larger in the granular insular area (area GI), one of the two CTAs, than in the dysgranular insular area (area DI). In addition, taste responses were suppressed by CNQX or by both APV and CNQX in area GI in a significantly larger number of layer V neurons than in area DI. The present results indicate that normal excitatory transmission of taste afferents in the CTA in rats was mediated by both NMDA and non-NMDA receptors. The finding that a large fraction of neurons in the CTA in rats mediated taste information through NMDA receptors in normal transmission might be related to the higher potency of the plasticity observed in the CTA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00231062
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  • 111
    Electronic Resource
    Electronic Resource
    Nephrotic syndrome associated with N-hydroxyureas, inhibitors of 5-lipoxygenase (1995)
    Springer
    Archives of toxicology 69 (1995), S. 480-490 
    Details
    ISSN: 1432-0738
    Keywords: Key words 5-Lipoxygenase inhibitors ; N-Hydroxyureas ; Nephrotoxicity ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The N-hydroxyurea derivatives 70C ((E)-N-{3-[3-(4-fluorophenoxy)phenyl]-1-(R,S)-methylprop-2-enyl}-N-hydroxyurea) and its (R) 225C and (S) 404C enantiomers, which were being developed as 5-lipoxygenase inhibitors for the treatment of certain allergic and inflammatory conditions, were found to cause severe glomerulonephropathy in the rat. The lesion appeared to be of greater severity in female rats compared with male rats. In addition, 70C and 225C treated animals appeared more severely affected than 404C treated animals. Detailed examination of the lesion in animals dosed with 225C showed that there was a clear relationship between the onset of the lesion and the dose given, i.e. the higher the dose the sooner the lesion developed. The earliest changes detected in the kidney by transmission electron microscopy were noted in the glomeruli, in which the visceral cells appeared enlarged and showed varying degrees of foot process loss. In the more advanced lesion, the degree of foot process loss became more obvious and changes in the kidney tubules were seen by light microscopy. The morphological changes were mirrored by a dose-related increase in water consumption, an increased kidney to body weight ratio and gastrointestinal oedema, suggesting impaired renal function. Shortly after the onset of foot process loss, decreases in the total plasma protein and albumin and increases in the plasma cholesterol, triglycerides, urea and creatinine were recorded. These changes, particularly the foot-process loss, together with increased proteinuria, hypoalbuminaemia, hypercholesterolaemia and lipaemia, are all characteristic of “minimal change nephrotic syndrome”. Because of the serious nature of the kidney lesion caused by these N-hydroxyureas in the rat, it was considered that it precluded their development as therapeutic agents for use in man.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002040050202
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  • 112
    Electronic Resource
    Electronic Resource
    Regional differences in expression of osteonectin mRNA after administration of cadmium to rats (1995)
    Springer
    Archives of toxicology 69 (1995), S. 590-595 
    Details
    ISSN: 1432-0738
    Keywords: Key words Cadmium ; Osteonectin ; Metallothionein ; Gene expression ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Osteonectin gene expression in relation to metallothionein mRNA expression was investigated in various tissues from Cd-treated rats. After a single 50 μmol/kg subcutaneous injection of CdCl2, Cd predominantly accumulated in the liver and metallothionein gene expression significantly increased concomitantly with Cd accumulation, but no alteration of osteonectin gene expression was observed. In the kidney and lung, both metallothionein and osteonectin mRNA increased significantly but the elevation of metallothionein mRNA levels (1 h after Cd administration) preceded that of osteonectin (3 h after administration). A significant elevation of osteonectin mRNA levels was also observed in the testis after 3 h, but that of metallothionein mRNA occurred after 6 h. Not only accumulation of Cd but also increments in both osteonectin and metallothionein mRNA were minimal in the brain, but a significant increase in gene expression was observed after 1 h for osteonectin and after 3 h for metallothionein. Since, except in the testis, metallothionein gene expression preceded osteonectin gene expression, the induced metallothionein might transpose Cd and thereby affect its levels immediately, thus reducing the levels of Cd available for accumulation in other tissues. Hence, the osteonectin-Cd interaction might be secondary to the metallothionein-Cd interaction. However, the fact that osteonectin mRNA was predominantly induced by Cd administration in the target tissues of Cd toxicity, such as the lung, kidney and testis, suggests the possible involvement of osteonectin in Cd intoxication/detoxication mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002040050218
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  • 113
    Electronic Resource
    Electronic Resource
    Effects of paraquat, dinoseb and 2,4-D on intracellular calcium and on vasopressin-induced calcium mobilization in isolated hepatocytes (1995)
    Springer
    Archives of toxicology 69 (1995), S. 460-466 
    Details
    ISSN: 1432-0738
    Keywords: Key words Paraquat ; Dinoseb ; 2 ; 4-D Intracellular calcium ; Rat ; Hepatocytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The effects of the herbicides paraquat, dinoseb and 2,4-D on intracellular Ca2+ levels and on vasopressin-induced Ca2+ mobilization were investigated in intact isolated hepatocytes. Incubation of rat hepatocytes with paraquat (5 mM for 60 min) and dinoseb (10 μM) resulted in a time-dependent loss of viability by approximately 25%. Viability of cells treated with 2,4-D decreased significantly, dropping to about 20% at 10 mM and 60 min incubation. Exposure of hepatocytes to paraquat (1–10 mM) for 60 min had no effect on the basal level of [Ca2+] i . Additionally, exposure to paraquat had no effect on the magnitude and on the duration of the [Ca2+] i response to vasopressin. In the presence of 2,4-D (1–10 mM), basal [Ca2+] i increases as a function of herbicide concentration. The magnitude of the Δ[Ca2+] i response decreases from 256±8 nM in control to 220±5 nM, at 10 mM 2,4-D. Exposure of hepatocytes to dinoseb (1–10 μM) had no effect on the basal level of [Ca2+] i . However, a strong concentration-dependent decrease in the magnitude of Δ[Ca2+] i in response to vasopressin was noticed at 60 min incubation. Dinoseb markedly inhibited the stimulation of the production of inositol phosphates by vasopressin stimulus. The present study demonstrates that paraquat, 2,4-D and dinoseb cause cell death in hepatocytes by mechanisms not related to an early increase in [Ca2+] i . Additionally, it has been shown for the first time that dinoseb disturbs the transduction mechanism promoted by vasopressin by inhibiting the formation of IP3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002040050199
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  • 114
    Electronic Resource
    Electronic Resource
    Investigation of potential oncogenetic effects of β-cyclodextrin in the rat and mouse (1995)
    Springer
    Archives of toxicology 69 (1995), S. 631-639 
    Details
    ISSN: 1432-0738
    Keywords: Key words β-Cyclodextrin ; Oncogenicity ; Rat ; Mouse
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The results of oncogenicity studies of β-cyclodextrin in inbred Fischer 344 rats and CD-1 outbred mice are presented. Chronic feeding of β-cyclodextrin to Fischer 344 rats and CD-1 mice did not cause any treatment related carcinogenic effects. The only toxic effect was seen in mice as macroscopic distension of the large intestine with soft or fluid contents, histologically associated with the mucosa covered by mucous secretion containing exfoliated cells, and mucosal flattening and intestinal gland atrophy. Despite these observations, no differences between control and treated groups were observed concerning mortality, clinical observations or body weight and food consumption.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002040050224
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  • 115
    Electronic Resource
    Electronic Resource
    Prediction of uptake of methyl mercury by rat erythrocytes using a two-compartment model (1995)
    Springer
    Archives of toxicology 70 (1995), S. 34-42 
    Details
    ISSN: 1432-0738
    Keywords: Key words Compartment model ; Erythrocytes ; Intracellular compartmentation ; Methyl mercury ; Rat ; Uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The uptake of methyl mercury (MeHg) by isolated rat erythrocytes was studied at 37°C using MeHg-cysteine (MeHgCySH), MeHg-glutathione (MeHgGSH), MeHg-mercaptalbumin (MeHgMASH) and the mixture of MeHgCySH with MeHgGSH, MeHgCySH with MeHgMASH, MeHgGSH with MeHgMASH at different MeHg concentrations. The measured MeHg concentrations were analyzed according to the Akaike’s information criterion in order to determine the suitable compartment model. After determining a two-compartment model, a model-independent two-compartment model was developed from the kinetics of uptake of MeHg at a concentration of 1 mmol MeHg/l packed erythrocytes using MeHgCySH, MeHgGSH and MeHgMASH, respectively. The developed two-compartment model was validated by predicting the kinetics of uptake of MeHg by rat erythrocytes at different MeHg concentrations and different mixtures of MeHg-complexes. Then, the predicted values were compared with the measured values. The results suggested: 1) MeHg uptake appeared suitable to be described by a two-compartment model, while using MeHgGSH, MeHgMASH, MeHgCySH at lower concentrations and the mixtures of MeHg-complexes; 2) MeHgCySH uptake was slowest among three kinds of MeHg-complexes, although a postulated cysteine-facilitated MeHgCySH transport system might exist in erythrocyte membrane; 3) the mixture of MeHg-complexes might facilitate MeHgCySH uptake; 4) there might be a second MeHg intracellular compartment in rat erythrocytes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002040050246
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  • 116
    Electronic Resource
    Electronic Resource
    Cytotoxicity of propyl gallate and related compounds in rat hepatocytes (1995)
    Springer
    Archives of toxicology 69 (1995), S. 204-208 
    Details
    ISSN: 1432-0738
    Keywords: Key words Propyl gallate ; Rat ; Hepatocytes ; Cytotoxicity ; Gallate esters ; Antioxidant ; Mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The cytotoxic effects of propyl gallate (PG), its related gallates and gallic acid have been studied in freshly isolated rat hepatocytes. Addition of PG (0.5–2.0 mM) to hepatocyte suspension elicited concentration-dependent cell death accompanied by losses of intracellular ATP, adenine nucleotide pools, glutathione (GSH) and protein thiols. The rapid loss of intracellular ATP preceded the onset of cell death caused by PG. In the comparative toxic effects of PG and related gallates at concentration of 1 mM, octyl gallate (OG), dodecyl gallate (DG) and butyl gallate (BG) elicited an abrupt depletion of ATP, followed by an acute cell death. These gallates were more toxic than PG; the toxic effects of PG were similar to those of methyl gallate (MG) and ethyl gallate (EG). In mitochondria isolated from rat liver, PG caused a concentration-dependent increase in the rate of state 4 oxygen consumption, indicating an uncoupling effect. The rate of state 3 oxygen consumption was inhibited by OG and DG. According to the respiratory control index, the order of impairment potency to mitochondria was OG〉BG, DG〉PG〉EG, MG〉gallic acid. These results indicate that PG and related gallates are toxic to hepatocytes and that the acute cytotoxicity may be due to mitochondrial dysfunction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002040050159
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    Subchronic toxicity of 3-phenylamino alanine, an impurity in L-tryptophan reported to be associated with eosinophilia-myalgia syndrome (1995)
    Springer
    Archives of toxicology 69 (1995), S. 444-449 
    Details
    ISSN: 1432-0738
    Keywords: Key words Eosinophilia-myalgia syndrome ; L-Tryptophan ; 3-(Phenylamino) alanine ; Rat ; 1 ; 1’-Ethylidenebis (L-tryptophan)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Consumption of certain product lots of L-tryptophan (LT) has been reported to be epidemiologically associated with an outbreak of eosinophilia-myalgia syndrome (EMS) in the United States. Since the production lots were found to contain 3-phenylamino alanine (PAA) as an impurity, its effects were studied by administering the substance orally by gavage to 5-week-old Sprague-Dawley rats. Groups of animals were given PAA for 13 consecutive weeks at dose levels of 1, 10 and 100 mg/kg per day. The animals were killed at 4 or 8 weeks. Hematological and blood biochemical tests were performed and detailed histopathological observations were made. No significant abnormalities were observed in the test animals and in particular no EMS-like conditions. A brief summary of other animal studies using several species of rats and mice performed in our laboratory since 1989 on various LT related substances is also presented. No EMS-like effects were observed in these studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002040050197
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  • 118
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    Social deprivation enhances the vulnerability of male Wistar rats to stressor- and amphetamine-induced behavioral sensitization (1995)
    Springer
    Psychopharmacology 117 (1995), S. 116-124 
    Details
    ISSN: 1432-2072
    Keywords: Psychostimulant ; Amphetamine ; Stress ; Long-term sensitization ; Social isolation ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The aim of the present study was to assess the influence of experimential factors on the vulnerability of rats to develop amphetamine (AMPH)- and stressor-induced behavioral sensitization. Young male Wistar rats with previous social experience were isolated from their peers for 2 weeks. 1) The effect of this short-lasting social deprivation were: a) a reduced tendency to explore a fearful environment; b) a prolonged exploratory activity in response to a novel but little fearful environment; and c) a dose-dependent increase in the psychomotor stimulation induced by systemic AMPH injection. 2) After repeated AMPH injections (injection every other day for 10 days), isolated rats exhibited behavioral sensitization at lower doses (0.5 and 0.75 mg/kg) than those required for group-housed rats (1 mg/kg). 3) After being submitted to a repeated stressor (3, 7 or 14 footshock sessions, with 2 days between sessions), the isolated rats exhibited a greater increase in the behavioral responsivity to a subsequent AMPH challenge (1 mg/kg) than did the group-housed rats regardless of the number of stress sessions. In conclusion, these results suggest that experiential factors such as privation of contact with peers (social isolation) may make rats more vulnerable to the long-term repercussions of chronic environmental and pharmacological challenges.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02245106
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  • 119
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    Can the DRL 72s schedule selectively reveal antidepressant drug activity? (1995)
    Springer
    Psychopharmacology 117 (1995), S. 154-161 
    Details
    ISSN: 1432-2072
    Keywords: Antidepressants ; DRL 72s schedule Water reinforcement ; Chlordiazepoxided-Amphetamine ; Haloperidol ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of three antidepressants, desipramine (2.5–20 mg/kg) tranylcypromine (0.63–2.5 mg/kg) mianserin (1.25–10 mg/kg) and three non-antidepressants, chlordiazepoxide (CDP; 1.25–10 mg/kg) haloperidol (0.02–0.16 mg/kg)d-amphetamine (0.31–1.25 mg/kg) were evaluated in rats responding for water reinforcement under a DRL 72s schedule. The antidepressants all produced dose-related decreases in overall response rates, but no significant changes in reinforcement frequency. In contrast, the anxiolytic CDP did increase the number of reinforcers obtained. Haloperidol decreased both reinforcers and responses whilstd-amphetamine stimulated responding, thereby decreasing reinforcement frequency. An analysis of the modes of inter-response times (IRTs) revealed no significant shifts in the peaks of the IRT distributions for most of the drugs tested. Amphetamine, however, (0.31 and 0.63 mg/kg) decreased the modal values in correspondence with the shift to the left of the peak of responding caused by this compound. These results are discussed in the context of the use of the DRL 72s procedure as a screening test for antidepressant drugs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02245181
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  • 120
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    Strain differences in the rewarding and dopamine-releasing effects of morphine in rats (1995)
    Springer
    Psychopharmacology 117 (1995), S. 240-247 
    Details
    ISSN: 1432-2072
    Keywords: Microdialysis Conditioned place preference ; Morphine Locomotor activity ; Genetic differences ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Studies examining differential sensitivity to psychoactive drugs in mice suggest that genotype may play a critical role. Furthermore, an involvement of genotype in mediating individual differences in sensitivity to the rewarding effects of several drugs of abuse has also been postulated. The aim of this study was to examine the conditioned rewarding and dopamine-releasing effects of morphine in two outbred rat strains commonly used in addiction research. Additionally, the behavioural and neuroendocrine responses of these strains to the stress of novelty were also examined. Basal locomotor activity was higher in Wistar rats than Sprague-Dawley following exposure to a novel environment. In contrast, elevations in plasma corticosteroid levels following novelty exposure did not differ between the two strains. In a counterbalanced place preference conditioning procedure, increasing doses of morphine (1.0–10.0 mg/kg SC) produced significant conditioned place preferences (CPP) in both Wistar and Sprague-Dawley strains. However, Wistar rats required a significantly larger dose of morphine (5.0 mg/kg) to produce a significant CPP than the Sprague-Dawley rats. In the latter strain, CPP occurred with doses of 3.0 mg/kg and greater. In parallel microdialysis experiments, both strains showed significant dose-related increases in dopamine release in the nucleus accumbens following acute morphine challenge (1.0–10.0 mg/kg SC). Again in Wistar rats, a larger dose of morphine was necessary to produce a significant increase in comparison to Sprague-Dawley rats. These results show that genetically distinct rat strains can show differential sensitivity to opioids, more specifically to drug-seeking responses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02245193
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    Chronic treatment with fluvoxamine by osmotic minipumps fails to induce persistent functional changes in central 5-HT1A and 5-HT1B receptors, as measured by in vivo microdialysis in dorsal hippocampus of conscious rats (1995)
    Springer
    Psychopharmacology 117 (1995), S. 358-363 
    Details
    ISSN: 1432-2072
    Keywords: Microdialysis ; Dorsal hippocampus 5-HT1A and 5-HT1B receptors ; Chronic treatment Fluvoxamine ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This study investigated the alterations of the 5-HT1A and 5-HT1B autoreceptor function following chronic treatment with fluvoxamine using osmotic minipumps. The 5-HT1A and 5-HT1B autoreceptor function were studied using microdialysis in the dorsal hippocampus. The effect of the 5-HT1A receptor agonist 8-OH-DPAT (0.3 mg/kg, SC) and the 5-HT1B receptor agonist RU-24969 (100 nM through the dialysis probe for 30 min) on 5-HT release was compared with rats chronically treated with saline. 8-OH-DPAT decreased 5-HT release to 55% and 60% of baseline, while RU-24969 decreased 5-HT release to 66% and 70% of baseline value in the saline and fluvoxamine group, respectively. In both cases, differences between the saline and fluvoxamine groups were not statistically significant. Plasma levels of fluvoxamine after 21 days of treatment ranged from 3 to 5 ng/ml. Fluvoxamine concentration in rat brain during treatment was estimated between 100 and 200 nM, which approximates to the IC50 value of fluvoxamine on the 5-HT transporter in synaptosomes and is 50 times higher than the Kd value for the 5-HT reuptake site. In conclusion, no evidence was found for changes in 5-HT1A,B receptor function using 8-OH-DPAT and RU-24969 as probes after continuous treatment with fluvoxamine by means of osmotic minipumps.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02246110
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    Dissociation between cognitive and motor/motivational deficits in the delayed matching to position test: effects of scopolamine, 8-OH-DPAT and EAA antagonists (1995)
    Springer
    Psychopharmacology 122 (1995), S. 268-280 
    Details
    ISSN: 1432-2072
    Keywords: Operant delayed matching task ; MK-801 ; CGS 19755 ; Scopolamine ; 8-OH-DPAT ; Cognition ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of the muscarinic antagonists scopolamine HBr and MeBr, the 5-HT1A agonst 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), and theN-methyl-d-aspartate (NMDA) antagonists MK-801 and CGS-19755 on performance of rats in a delayed matching-to-position task were examined. Pretreatment with scopolamine HBr (0.05 and 0.1 mg/kg), resulted in a delay-dependent decrease in the percentage of correct responses and discriminability (logd), but had no effect on either the latency to complete trials, or the rate of trial completion during the fixed duration session. Scopolamine MeBr (0.1 mg/kg) did not impair percent correct or increase the response latency but did decrease the rate of trial completion. 8-OH-DPAT (up to 0.3 mg/kg), had no effect on percent correct, but did induce a small decrease in discriminability. The impairment in discriminability occurred only at a dose that substantially reduced the rate of trial completion. Both MK-801 (0.05 mg/kg) and CGS 19755 (10 mg/kg) induced a delay-independent impairment in percent correct, discriminability and a reduction in the rate of trial completion without affecting latency. A lower dose of CGS 19755 (5.0 mg/kg) induced a slight impairment in discriminability without significantly affecting the other measures. Taken together, these results demonstrate some dissocation between drug-induced cognitive and motor/motivational deficits in the DMTP test. However, the data question the specificity of putative cognitive impairments reported in many previous studies with the 5-HT1A agonist 8-OH-DPAT.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02246548
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    Effects of morphine on different aspects of social play in juvenile rats (1995)
    Springer
    Psychopharmacology 117 (1995), S. 225-231 
    Details
    ISSN: 1432-2072
    Keywords: Social play ; Opioid ; Morphine Environment ; Social isolation ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To clarify the influence of opioids on social play, the effects of morphine on playful and non-playful social behavior in juvenile rats was investigated under different conditions. Environmental variables employed were different (dim and intense) levels of illumination during testing, familiarity to the test cage, and different periods of social isolation prior to testing. Under dim light conditions, morphine markedly increased playful social behavior, such as pinning, boxing/wrestling and following/chasing, whereas non-playful social behavior such as social exploration and contact behavior was hardly affected. This effect of morphine was independent of duration of previous isolation and dose-dependent, with a maximal effect at 1.0 mg/kg. The mechanism of this effect is interpreted as an action on the rewarding aspects of play. A dose of 0.1 mg/kg of morphine abolished the initial suppression of play induced by unfamiliarity to the test cage, without influencing total levels of play. This may be an effect of morphine on the integration of sensory stimuli. Under intense light conditions, where playful behavior was completely suppressed, morphine itself hardly affected such behavior, but decreased some aspects of non-playful social behavior. These results suggest that in juvenile rats playful and non-playful forms of social behavior are differentially regulated. In addition, opioid systems may be involved at different levels in the regulation of social play.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02245191
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  • 124
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    The ambivalent behaviour “stretched approach posture” in the rat as a paradigm to characterize anxiolytic drugs (1995)
    Springer
    Psychopharmacology 121 (1995), S. 81-90 
    Details
    ISSN: 1432-2072
    Keywords: Stretched approach posture ; Ambivalent behaviour ; Intention movements ; Ethological observation ; Rat ; Anxiety disorders ; Benzodiazepines ; 5-HT1A receptor agonists ; 5-HT uptake inhibitors ; Clonidine ; Clorgyline ; Anxiogenic drugs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effect of various psychotropic drugs on the ambivalent behaviour “stretched approach posture” (SAP) in the rat was assessed. SAP was elicited after a mild startle reaction due to physical contact with an electrified prod at one end of a straight runway. Using ethological observation methods, SAP as well as intention movements, prod contact, crossings, rearing, exploration, grooming and immobility were recorded. The benzodiazepine receptor agonists chlordiazepoxide, diazepam and alprazolam, the 5-HT1A receptor agonists flesinoxan and ipsapirone and the 5-HT uptake inhibitor clomipramine selectively (no effect on crossings) reduced SAP. Except for alprazolam, these drugs also reduced intention movements. In addition, chlordiazepoxide and diazepam enhanced prod contact. Reductions of SAP and intentions with concomitant reductions of crossings (nonspecific anti-ambivalent effects) were established for the α2-adrenoceptor agonist clonidine and the MAO inhibitor clorgyline. The 5-HT uptake inhibitor fluvoxamine suppressed intention movements, but not SAP. The mixed 5-HT/NA uptake inhibitor imipramine did not significantly affect SAP or intentions, but reduced crossings. The 5-HT2C/1B receptor agonist m-CPP, the inverse BZD receptor agonists FG 7142 and DMCM, and the α2-adrenoceptor antagonist yohimbine, to all of which putative anxiogenic effects have been ascribed, had no effect on SAP directed towards the prod. m-CPP, however, produced an increase in the stretched posture directed away from the prod (SAwayP). FG 7142 reduced intentions while strongly enhancing immobility (freezing). SAwayP and/or freezing may possibly reflect anxiogenic properties of drugs. The putative anxiogenic drug pentylenetetrazol false positively reduced SAP while increasing exploration. The dopamine-D2 receptor antagonist haloperidol and the catecholamine releaserdl-amphetamine had no effect on ambivalent behaviour. The muscarine receptor antagonist scopolamine reduced SAP and intentions while stimulating crossings. Finally, the 5-HT2C receptor antagonist ritanserine, the CCKA receptor antagonist devazepide, the CCKB receptor antagonist L-365.260 and the strychnine-insensitive glycine site antagonist 7-Cl-kynurenic acid were without effect on the behaviours in this paradigm using single doses. In conclusion, SAP and intention movements were reduced selectively by anxiolytic agents from different classes, including benzodiazepine receptor agonists, 5-HT1A receptor agonists and a 5-HT uptake inhibitor, whereas an α2-adrenoceptor agonist and a MAO inhibitor reduced SAP non-selectively. SAP in relation to other behaviours may therefore serve as a valuable paradigm to characterize anxiolytic drugs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02245594
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    Effects of benzodiazepine receptor partial inverse agonists in the elevated plus maze test of anxiety in the rat (1995)
    Springer
    Psychopharmacology 121 (1995), S. 118-126 
    Details
    ISSN: 1432-2072
    Keywords: Anxiety ; Plus maze ; Rat ; Benzodiazepine receptor ; DMCM ; FG 7142 ; Yohimbine ; Pentylenetetrazol ; β-Carboline ; Inverse agonist
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The present series of experiments examined the effects of five benzodiazepine receptor (BZR) partial inverse agonists on the behaviour of rats on an elevated plus maze. The drugs were tested in a standard plus maze with 3-cm walls added to the open arms, as this has been shown to increase the sensitivity of the plus maze to anxiogenic-like drug effects (Jones and Cole 1995). The drugs tested were FG 7142 (0–100 mg/kg),β-CCE (0–30 mg/kg), ZK 132 556 (0–100 mg/kg), ZK 90 886 (0–30 mg/kg) and Ro 15–4513 (0–30 mg/kg). In addition, to allow a comparison with previous studies, the effects of three reference substances, DMCM (0–2.5 mg/kg), pentylenetetrazol (PTZ; 0–30 mg/kg) and yohimbine (0–5 mg/kg), were also examined. These three reference compounds produced a dose-dependent reduction in the duration of open arm exploration and the total number of open arm entries, indicative of anxiogenic-like effects. DMCM produced significant effects at the doses of 1.25 and 2.5 mg/kg, PTZ at 30 mg/kg, and yohimbine at 5 mg/kg. The BZR partial inverse agonist FG 7142 (10, 30 and 100 mg/kg) also reduced the duration of open arm exploration and the total number of arm entries. The minimally effective dose resulted in a receptor occupancy of approximately 80%. Ro 15–4513 also produced anxiogenic-like effects, but only at a dose (30 mg/kg) that resulted in a receptor occupancy of approximately 95%. In contrast, the other BZR partial inverse agonists, ZK 132 553 and ZK 90 886, did not significantly reduce the duration of open arm exploration, even at doses that produced greater than 95% receptor occupancies.β-CCE also did not reduce open arm exploration at any dose tested (0–30 mg/kg). The GABA shift, a biochemical index of intrinsic activity, indicates that these latter three compounds are more inverse agonistic than Ro 15–4513. In summary, these results demonstrate that not all BZR receptor partial inverse agonists have anxiogenic-like activity in the rat plus maze, and that the GABA shift, a biochemical index of intrinsic efficacy, does not predict which BZR partial inverse agonists are anxiogenic.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02245598
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    Failure of CCK receptor ligands to modify anxiety-related behavioural suppression in an operant conflict paradigm in rats (1995)
    Springer
    Psychopharmacology 121 (1995), S. 127-134 
    Details
    ISSN: 1432-2072
    Keywords: Anxiety ; Cholecystokinin ; CCK-A and CCK-B receptor antagonists ; CCK-B receptor agonists ; Behavioural suppression ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of cholecystokinin (CCK) receptor ligands were studied in the rat safety signal withdrawal conflict procedure, an operant paradigm sensitive to both anxiolytic and anxiogenic compounds. In this procedure, behavioural suppression of lever pressing for food was induced by the withdrawal of a conditioned signal for safety without the usual presentation of a conditioned signal for danger. The compounds tested were selective CCK-B antagonists [CI-988 (0.01–1 mg/kg SC), L-365,260 (0.004–2 mg/kg IP) and LY 262,691 (0.001–1 mg/kg SC)], CCK-B agonists [CCK-4 (0.01–1 mg/kg SC) and BC 264 (0.004–1 mg/kg IP)] and CCK-A antagonists [devazepide (0.001–1 mg/kg SC) and lorglumide (0.01–1 mg/kg SC)]. None of these drugs induced the expected behavioural effects, i.e. an anxiolytic-like release of the behavioural suppression with CCK-B and, possibly, CCK-A antagonists and/or a further reduction of lever pressing with CCK-B agonists, indicative of an anxiogenic-like potential. In contrast, the established anxiolytic lorazepam (0.06–0.25 mg/kg IP), as well as diazepam (2 mg/kg IP) and buspirone (0.25 mg/kg SC) used as positive control drugs, released the suppression of pressing for food during the period associated with the safety signal withdrawal, whereas picrotoxin (1 mg/kg IP), used as an anxiogenic control, further reduced responding during this conflict period. The present results contrast with a series of published data suggesting the involvement of CCK processes in anxiety-related behaviour in rodent models such as the elevated plus-maze or the light:dark two compartment test, and in panic disorders in humans. They indicate that the behavioural effects of one category of drugs might vary considerably, depending on the experimental situation. Furthermore, they allow the conclusion that anticipatory anxiety generated by withdrawal of conditioned signals for safety does not involve CCK-related processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02245599
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    Scopolamine prevents augmentation of stereotypy induced by chronic methamphetamine treatment (1995)
    Springer
    Psychopharmacology 121 (1995), S. 158-163 
    Details
    ISSN: 1432-2072
    Keywords: Methamphetamine ; Behavioral sensitization ; Scopolamine ; Acetylcholine ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Cholinergic neurotransmission has been implicated in various forms of neural plasticity such as kindling and learning. We have previously shown that blockade of muscarinic cholinergic receptors prevents the development of locomotor sensitization to methamphetamine. The present study was conducted to examine whether scopolamine, a muscarinic cholinergic antagonist, would also block augmentation of stereotypy induced by chronic methamphetamine (MA) treatment. Rats treated with MA (2.5 mg/kg, SC) for 10 days indicated significantly enhanced stereotyped behavior when tested with MA (2.5 mg/kg) after a 7-to 8- day withdrawal. Pretreatment with scopolamine (3 mg/kg) prior to MA administration prevented the augmentation of stereotypy. Rats treated with scopolamine alone showed no difference in MA-induced stereotypy compared to those treated with saline. Scopolamine methylbromide, a derivative of scopolamine that does not easily cross the blood-brain barrier, had no effect on the augmentation of stereotypy. These results suggest that stimulation of central muscarinic cholinergic receptors plays a role in the development of sensitization to the stereotypy stimulating effect of methamphetamine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02245625
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    Inhibitory mechanisms in epileptiform activity induced by low magnesium (1995)
    Springer
    Pflügers Archiv 430 (1995), S. 238-245 
    Details
    ISSN: 1432-2013
    Keywords: Epilepsy ; Epileptiform activity ; Mg2+-free media ; Low magnesium ACSF ; PDS afterpotentials ; Inhibition ; Hippocampus ; Rat ; GABA ; Ca2+-dependent K+ current
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In rat hippocampal slices epileptiform activity was induced by superfusion with Mg2+-free artificial cerebrospinal fluid (ACSF). Paroxysmal depolarization shifts (PDS) were evoked by electrical stimulation of Schaffer collaterals. To investigate the afterpotentials that follow PDS, intracellular recordings were made from CA1 pyramidal cells. The experiments revealed that several components are engaged in the generation of PDS afterpotentials in Mg2+-free ACSF. A long lasting component which determined the overall duration of the PDS afterhyperpolarization was blocked by intracellular application of ethylenebis(oxonitrilo)-tetraacetate (EGTA); concomitantly, the afterhyperpolarizations following depolarizing current injections were blocked. This indicated that the long lasting component was due to a slow Ca2+-activated K+ current. The block of Ca2+-activated K+ current uncovered a depolarizing PDS afterpotential with an N-shaped voltage dependence, suggesting that this depolarizing afterpotential component may be due to an N-methyl d-aspartate (NMDA) conductance. Intracellular injection of Cl− revealed that the PDS were followed by Cl− currents lasting about 500 ms. This component could be blocked by application of bicuculline suggesting that it is due to a synaptically GABA-mediated (i.e. γ-aminobutyric acid) Cl− current. A comparison of PDS afterpotentials in Mg2+-free ACSF and those in other models of epileptiform activity suggests that similar sequences of inhibitory components are activated in spite of different pharmacological alterations of membrane conductances which induce the epileptiform discharges.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00374655
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    Diffusion of myoglobin in skeletal muscle cells — dependence on fibre type, contraction and temperature (1995)
    Springer
    Pflügers Archiv 430 (1995), S. 519-525 
    Details
    ISSN: 1432-2013
    Keywords: Diffusion coefficient ; Muscle cells ; Myoglobin ; Microinjection ; Oxygen ; Facilitated diffusion ; Intracellular oxygen transport ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We measured the diffusion coefficient of myoglobin (D Mb) inside mammalian skeletal muscle cells with a microinjection technique. A small bolus of horse Mb was injected into a single muscle fibre and the subsequent time-dependent changes of the Mb profiles along the fibre axis were measured with a microscope-photometer. For fibres of the rat soleus muscle at 22° C, a D Mb of 1.3·10−7 cm2/s was found, confirming a result obtained previously by us for rat diaphragm muscle with a photo-oxidation technique. In the extensor digitorum longus muscle of the rat, a higher value of 1.9 · 10−7 cm2/s was measured. Auxotonic muscle contractions did not change the apparent D Mb. For the temperature range between 22 ° C and 37 ° C, a temperature coefficient, Q 10, of 1.5 was calculated. The implication of this result for the role of Mb in the facilitation of oxygen transport was examined. Model calculations show that with this relatively low D Mb value, the intracellular oxygen supply can be improved only slightly.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00373888
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    Involvement of intracellular calcium ions in the release of the fluorescent dye calcein by cholinergic and α-adrenergic agonists from rat parotid acinar cells (1995)
    Springer
    Pflügers Archiv 429 (1995), S. 555-560 
    Details
    ISSN: 1432-2013
    Keywords: Rat ; Parotid glands ; Salivary glands ; Calcein ; Amylase ; Secretion ; Carbachol ; Noradrenalin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Effects of cholinergic and adrenergic agonists on the secretion of the fluorescent dye calcein were examined to clarify the involvement of calcium ions in the secretion of calcein from acinar cells dispersed from the rat parotid gland. Addition of carbachol (CCh) and noradrenalin (NA), but not isoproterenol (IPR), enhanced the net release of calcein from acinar cells during the subsequent 10 min in a dose range from 10−8 M to 10−6 M. The net release of calcein reached a maximum 7 min after the addition of CCh. The release of calcein was suppressed by the simultaneous additions of atropine with CCh, or phenoxybenzamine with NA. Addition of CCh induced a sustained dosedependent increase in the intracellular levels of calcium ions, ([Ca2+]i). Addition of NA at 10−6 M increased [Ca2+]i. Phenoxybenzamine completely inhibited the NA-induced increase, but propranolol did not. The removal of extracellular calcium ions did not influence the release of calcein induced by 10−6 M CCh, but it abolished the sustained increase in [Ca2+]i. The transient increase in [Ca2+]i induced by CCh was observed in the absence of extracellular calcium ions. A calcium ion chelator, 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid (BAPTA) inhibited the CCh-induced release of calcein. The calcium ionophore, A23187 (2.5×10−6 M), but not 10−3 M dibutyryl cAMP, evoked the release of calcein. It also increased [Ca2+]i. Removal of extracellular calcium ions suppressed the A23187-induced release of calcein. These results suggest that the release of calcein from parotid acinar cells is transiently induced through an increase in [Ca2+]i by muscarinic and α-adrenergic agonists and may represent the initial process of salivary secretion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00704161
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  • 131
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    Promotion of sleep by heat in young rats (1995)
    Springer
    Pflügers Archiv 430 (1995), S. 729-738 
    Details
    ISSN: 1432-2013
    Keywords: Sleep ; Thermoregulation ; Slow wave activity ; Sleep drive ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The aim of the experiments was to study the effects of a moderate heat load on sleep in young (26-day-old) rats and to determine whether the sleep-promoting effect of heat results from stimulation of the homeostatic sleep process. The changes in sleep-wake activity, electroencephalogram slow wave activity (SWA) during non-rapid eye movement sleep (NREMS) and cortical temperature (T crt) were determined during and after long (24-h) and short (2.5-h) heat loads (elevation of ambient temperature from 26° C to 32° C), and after total sleep deprivation (SD) combined with a short-term heat load. The heat exposures elicited increases in T crt and rectal temperature (2 and 1.7° C respectively). The long-term heat load induced persistent, albeit slight enhancements in NREMS. Rapid eye movement sleep (REMS) increased with a 12-h delay during the 24-h heat load. Heat elicited an immediate large increase in SWA. After this initial increase, SWA declined and tended to fall below the baseline level during the last 12 h of the 24-h heat load. SWA and REMS were significantly suppressed after termination of 24-h heat loading. The increased SWA during the short-term heat load was not followed by subsequent alterations in sleep when the ambient temperature had returned to normal. However, after the combination of SD with the shortterm heat load the durations of NREMS and SWA were significantly enhanced compared with those found after SD at 26° C. The results are interpreted as suggesting that heat increases NREMS in the young rat by the same mechanism as is involved in the enhancement of NREMS after SD: a stimulation of sleep drive.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00386168
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  • 132
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    Effects of hypobaric hypoxia on histochemical fibre-type composition and myosin heavy chain isoform component in the rat soleus muscle (1995)
    Springer
    Pflügers Archiv 429 (1995), S. 601-606 
    Details
    ISSN: 1432-2013
    Keywords: Hypobaric hypoxia ; Histochemistry ; Muscle fibre-type ; Electrophoresis ; Myosin heavy chain isoform ; Soleus muscle ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Histochemical fibre-type composition and myosin heavy chain isoform component in the soleus muscle were studied in normoxic rats at postnatal ages of 5, 10, 15, and 20 weeks and in rats exposed to hypobaric hypoxia (460 torr) for 5 weeks from postnatal ages of 5, 10, and 15 weeks. The increase in the percentage of type I fibres and the concomitant decrease in that of type IIa fibres in the soleus muscle of normoxic rats were observed until 15 weeks of age. On the other hand, no change in the fibre-type composition of the muscle during postnatal development was observed in hypoxic rats, irrespective of the age at which they were exposed to hypoxia. The changes in the myosin heavy chain isoform component (MHC I and MHC IIa) of the muscle during postnatal development and by hypoxia corresponded well with those in the muscle fibre-type composition. It is concluded that hypobaric hypoxia inhibits the growth-related shift of muscle fibre-types from type IIa to type I and of myosin heavy chain isoforms from MHC IIa to MHC I in the rat soleus muscle, and that there are no changes in the muscle fibre-type composition or the myosin heavy chain isoform component caused by hypoxia after the shifts in these parameters which occur during postnatal development are completed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00373980
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  • 133
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    Developmental variation of the permeability to Ca2+ of AMPA receptors in presumed hilar glial precursor cells (1995)
    Springer
    Pflügers Archiv 431 (1995), S. 244-252 
    Details
    ISSN: 1432-2013
    Keywords: Rat ; Hippocampus ; Hilus ; Glutamate ; Kainate ; Patch-clamp in situ
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Glial cells in the hilus of the dentate gyrus of the rat were investigated using the patch-clamp technique in acute slices of the hippocampal formation. According to their voltage-gated current patterns, two classes of glial cells — putative astrocytes and presumed glial precursor cells — were apparent. The glutamate receptor agonists kainate, glutamate, and α-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) evoked inward currents at a holding potential of −70 mV in astrocytes and presumed glial precursor cells. Inward currents could also be induced in nucleated patches, indicating a direct action on glial receptors. In presumed hilar glial precursor cells, 6,7-dinitroquinoxaline-2,3-dione (DNQX; 10 μM) blocked the kainate-induced current, while it was partially inhibited by Zn2+ (2 mM) and Evans Blue (10 μM). Cyclothiazide (100 μM), in contrast, potentiated this current, indicating the presence of AMPA receptors. In 90% of the presumed glial precursor cells the excitatory amino-acid-evoked current voltage (I/V) relations were linear or outwardly rectifying and reversed close to 0 mV, which is characteristic for non-specific cation channels. To determine the permeability to Ca2+, I/V relations were determined in a Na+-free solution containing 40 mM Ca2+ and showed reversal potentials of a wide variation ranging from −63 mV to + 1 mV with corresponding P Ca/ P Cs permeability ratios of between 0.09 and 2.10. Statistical analysis revealed that the permeability to Ca2+ significantly decreased with an advance in age (r=−0.596; n=21; P〈0.01). These data suggest that the Ca2+ influx mediated by the activation of AMPA receptors expressed in presumed hilar glial precursor cells is dependent on the developmental stage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00410197
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    Psychopharmacological studies in rats responding at touch-sensitive devices (1995)
    Springer
    Psychopharmacology 118 (1995), S. 226-229 
    Details
    ISSN: 1432-2072
    Keywords: Touch-sensitive device ; Visual attention ; Cognition ; Amphetamine ; Serotonin ; 5-HT ; Acetylcholine ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A multiple choice serial reaction time task was used to investigate visual attention in rats. The intelligence panel consisted of a transparent touch-sensitive device, placed directly in front of a video monitor. Amphetamine (0.2–1.6 mg/kg IP) increased errors of omission and decreased latency to respond, but had no effect on accuracy. The 5-HT agonist quipazine (0.6–2.4 mg/kg IP) increased errors of omission, but did not affect other parameters. ICV administration of hemicholinium-3 (1–4 µg) had no effect upon performance. Thus, psychopharmacological manipulations can reliably alter performance in the touch window box, suggesting potential new avenues for rat cognitive testing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02245846
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  • 135
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    Sulpiride antagonizes the biphasic locomotor effects of quinpirole in weanling rats (1995)
    Springer
    Psychopharmacology 119 (1995), S. 299-304 
    Details
    ISSN: 1432-2072
    Keywords: Dopamine ; Autoreceptor ; Sulpiride ; Quinpirole ; Locomotion ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Low doses of dopamine (DA) agonists such as the D2 receptor subfamily agonist quinpirole are thought to stimulate DA autoreceptors selectively, thereby inhibiting locomotor activity. High doses of quinpirole initially suppress and later activate locomotion during a single test session; the activation is presumably due to stimulation of postsynaptic receptors. The aim of this study was to investigate whether pretreatment with a selective DA D2 receptor antagonist, sulpiride, could block the putative autoreceptor-mediated inhibition at a lower dose than was required to block the postsynaptically mediated activation. Male and female 30-day-old rats were injected SC with one of eight doses of sulpiride (0.313–40 mg/kg) or the vehicle. Sixty minutes later, rats were injected SC with 0.2 mg/kg quinpirole or the vehicle. Five minutes after the second injection, rats were placed in automated activity monitors which recorded locomotor behavior for 60 min at 5-min intervals. Quinpirole at this dose first suppressed and later increased locomotor activity. Sulpiride pretreatment dose-dependently reversed both the early inhibition and later activation of quinpirole-induced locomotion. However, sulpiride did not block the quinpirole-induced early suppression at a lower dose than was required to block the later activation. Thus, there was no evidence that the locomotor suppression elicited by quinpirole is mediated by a more sensitive subset of DA receptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02246295
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    Phencyclidine injections into the dorsal hippocampus disrupt long- but not short-term memory within a spatial learning task (1995)
    Springer
    Psychopharmacology 120 (1995), S. 203-208 
    Details
    ISSN: 1432-2072
    Keywords: Phencyclidine ; Dorsal hippocampus ; Rat ; Spatial navigation task
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Since the hippocampus is likely to be a major site of phencyclidine (PCP) action, the effects of various doses of PCP (1.8, 18 or 36 nM) as well as 3.6 nM MK-801 or saline injected directly into the dentate gyrus of the hippocampus was tested for acquisition of a spatial navigation task (dry land version of a water maze) using a paradigm that assesses short term memory based on learning within a day and long term memory based on learning between days. Results indicated that relative to saline or 1.8 nM PCP injected rats, rats with 18 or 36 nM PCP or 3.6 nM MK-801 injections were impaired in acquisition of the task as measured by increased distances traveled to find the food location between days but not within days. In additional experiments 36 nM PCP or 3.6 nM MK-801 did not produce any deficits in the acquisition of an object discrimination task. It is suggested that PCP through its blocking action of the NMDA receptor in the dentate gyrus or CA1 region of the dorsal hippocampus mediates the consolidation of new spatial location information.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02246194
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    Acute and subchronic effects of clozapine on licking in rats: tolerance to disruptive effects on number of licks, but no tolerance to rhythm slowing (1995)
    Springer
    Psychopharmacology 120 (1995), S. 249-255 
    Details
    ISSN: 1432-2072
    Keywords: Clozapine ; Ritanserin ; Atypical neuroleptic ; Lick rhythm ; Oscillator slowing ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In order to assess the effects of the atypical neuroleptic clozapine on orolingual competence in rats, tongue function was measured by quantitating the rhythm of tongue movements after acute (1.0, 3.0, 6.0 mg/kg) or subchronic intraperitoneal treatment (1.5, 3.0, 4.5 mg/kg, each dose for at least 7 days) with the drug. Thirsty rats were trained to lick water from a force-sensing disk by thrusting the tongue through a 12-mm-diameter hole to strike the horizontal disk located 5 mm below the hole. Number of licks in 2 min and rhythm of tongue movements (as determined by Fourier analysis of the force-time signal) were each dose dependently reduced in the acute dose-effect phase of the study. In the subchronic study number of licks exhibited tolerance, but the slowing of lick rhythm did not show tolerance. An acute dose range of the serotonin antagonist ritanserin (0.5, 1.0, 2.0, 4.0 mg/kg) was also studied in the same rats. Ritanserin had no effect on any of the measures of orolingual function. The clozapine result was replicated in a second study using younger, drug naive rats. The results for clozapine were contrasted with previous reports indicating that haloperidol has little effect on lick rhythm. Additional discussion evaluated the possible contribution of neurotransmitter receptors on motor neurons of the hypoglossal nucleus to the observed rhythm slowing induced by clozapine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02311171
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    The competitive NMDA antagonists CGP 43487 and APV potentiate dopaminergic function (1995)
    Springer
    Psychopharmacology 118 (1995), S. 310-315 
    Details
    ISSN: 1432-2072
    Keywords: MK-801 ; APV and CGP 43487 ; Apomorphine-induced behavior ; Motor activity ; Rota-rod test ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The administration to rats of different doses of the non competitive NMDA receptor blocker MK-801 (0.03–1 mg/kg IP) induced stimulation or reduction of locomotor activity, depending on the dose, whereas the competitive NMDA antagonists CGP 43487 (0.188–6 mg/kg IP) and APV (2.5–20 μg/rat ICV) inhibited locomotion at the highest doses. Unlike MK-801 and APV treatment, the administration of CGP 43487 did not induce impairment of rota-rod test performance. Both competitive and non-competitive NMDA antagonists, at doses devoid of any behavioral effect per se, potentiated the responses elicited by apomorphine (0.25 mg/kg SC). In particular, the occurrence of episodes of licking was weakly affected by MK-801 administration, but significantly increased by CGP 43487 and APV treatment; the presence of gnawing was augmented by all the pretreatments; sniffing, locomotion, grooming and rearing occurrence were not affected by the administration of NMDA antagonists. The results suggest that the competitive antagonists which facilitated dopaminergic function without causing motor impairment could be useful supplements in the treatment of Parkinson's disease.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02245960
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  • 139
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    Retarded acquisition of a temporal discrimination following destruction of noradrenergic neurones by systemic treatment with DSP4 (1995)
    Springer
    Psychopharmacology 118 (1995), S. 332-337 
    Details
    ISSN: 1432-2072
    Keywords: Noradrenaline ; DSP4 ; Operant behaviour Timing ; Interval bisection procedure ; Acquisition ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This experiment examined the effect of destroying central noradrenergic neurones, using the selective neurotoxin DSP4 (N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine) on the acquisition and performance of discrimination between two time intervals. Rats that had received systemic treatment with DSP4 and vehicle-treated control rats were trained in a series of discrete trials to press lever A following a 2-s presentation of a light stimulus and lever B following an 8-s presentation of the same stimulus. Both groups acquired the discrimination (〉90% correct choices) within 15 sessions; however, the DSP4-treated group showed significantly slower acquisition than the control group. When stable performance had been attained, ‘probe’ trials were introduced in which the light was presented for intermediate durations. Both groups showed sigmoid functions relating percent choice of lever B to log stimulus duration. Neither the bisection point (duration corresponding to 50% choice of lever B) nor the Weber fraction differed significantly between the DSP4-treated and control groups. The levels of noradrenaline were markedly reduced in the neocortex and hippocampus of the DSP4-treated group, but the levels of dopamine and 5-hydroxytryptamine were not altered. The results indicate that noradrenaline depletion induced by DSP4 retarded the acquisition of temporal discrimination, but did not impair steady-state discriminative precision.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02245963
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  • 140
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    Behavioural consequences of maternal exposure to natural cannabinoids in rats (1995)
    Springer
    Psychopharmacology 122 (1995), S. 1-14 
    Details
    ISSN: 1432-2072
    Keywords: Rat ; Development ; Behavior ; Cannabis ; Delta-9-tetrahydrocannabinol ; Motor activity ; Place preference ; Grooming ; Corticosterone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Cannabis sativa preparations (hashish, marijuana) are the most widely used illicit drugs during pregnancy in Western countries. The possible long-term consequences for the child of in utero exposure to cannabis derivatives are still poorly understood. Animal models of perinatal cannabinoid exposure provide a useful tool for examining the developmental effects of cannabinoids. Behavioral consequences of maternal exposure to either cannabis preparations or to its main psychoactive component, Δ9-tetrahydrocannabinol (THC) in rat models are reviewed in this paper. Maternal exposure to cannabinoids resulted in alteration in the pattern of ontogeny of spontaneous locomotor and exploratory behavior in the offspring. Adult animals exposed during gestational and lactational periods exhibited persistent alterations in the behavioral response to novelty, social interactions, sexual orientation and sexual behavior. They also showed a lack of habituation and reactivity to different illumination conditions. Adult offspring of both sexes also displayed a characteristic increase in spontaneous and water-induced grooming behavior. Some of the effects were dependent on the sex of the animals being studied, and the dose of cannabinoid administered to the mother during gestational and lactational periods. Maternal exposure to low doses of THC sensitized the adult offspring of both sexes to the reinforcing effects of morphine, as measured in a conditioned place preference paradigm. The existence of sexual dimorphisms on the developmental effects of cannabinoids, the role of sex steroids, glucocorticoids, and pituitary hormones, the possible participation of cortical projecting monoaminergic systems, and the mediation of the recently described cannabinoid receptors are also analyzed. The information obtained in animal studies is compared to the few data available on the long-term behavioral and cognitive effects on in utero exposure to cannabis in humans.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02246436
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    Examination of drug-induced and isolation-induced disruptions of prepulse inhibition as models to screen antipsychotic drugs (1995)
    Springer
    Psychopharmacology 122 (1995), S. 15-26 
    Details
    ISSN: 1432-2072
    Keywords: Prepulse inhibition ; Schizophrenia ; Dopamine ; Serotonin ; Glutamate ; Social isolation ; Clozapine ; Raclopride ; Haloperidol ; Rirsperidone ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Prepulse inhibition (PPI) of an acoustic startle response is impaired in schizophrenics. PPI can also be studied in the rat, and is impaired by dopamine (DA) D2/3 receptor agonists such as apomorphine. This disruption is reversed by DA antagonists, leading to proposals that this approach may be a useful means to identify novel antipsychotics. There is also evidence to suggest a role of serotonergic (5-HT) and glutamatergic systems in schizophrenia, and accordingly PPI can be disrupted by the 5-HT2 agonist DOI, and the non-competitive NMDA antagonist, dizocilpine. In the present study we have examined the effect of four antipsychotic drugs, haloperidol (0.1–0.3 mg/kg), raclopride (0.03–0.3 mg/kg), risperidone (0.3–3 mg/kg) and clozapine (0.0001–10 mg/kg), against the PPI disruptions induced by apomorphine (0.5 mg/kg), DOI (3 mg/kg) and dizocilpine (0.15 mg/kg). Furthermore, these drugs have been examined for their ability to restore a PPI deficit produced by housing rats under conditions of social isolation. All drugs except clozapine reversed an apomorphine-induced disruption. However, clozapine and risperidone, but not raclopride and haloperidol, reversed a DOI-induced disruption. Only risperidone was effective in restoring a PPI deficit produced by dizocilpine. In contrast to the drug-induced disruptions which were differentially sensitive to the various neuroleptics, isolation-induced disruptions were restored by each drug. These results support the idea that non-drug induced disruptions of PPI, such as social isolation, may be a more viable approach to identify novel antipsychotics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02246437
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    Cell deletion by apoptosis during regression of rat parotid sialadenosis (1995)
    Springer
    Virchows Archiv 427 (1995), S. 181-186 
    Details
    ISSN: 1432-2307
    Keywords: Isoproterenol ; Apoptosis ; Rat ; Parotid ; Sialadenosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Enlargement of the rat parotid salivary glands was induced by repeated administration of isoproterenol. Mean wet weights of the treated glands increased steadily to 240% of control values. Following withdrawal of the drug, quantitative histological techniques were used to investigate the balance between hypertrophy, hyperplasia and apoptosis. The volume occupied by acinar cells relative to the total gland volume together with cytoplasmic|:|nuclear area ratios as measures of hypertrophy increased during the early experimental period. Similarly, serous acinar cell mitotic counts increased, indicating that hyperplasia had occurred. Apoptosis was demonstrated at light microscopical level to be the main mechanism for cell deletion as the glands returned to normal size and weight. The results indicate that hypertrophy and hyperplasia of serous acinar cells contribute to isoproterenol-induced sialadenosis. The experimental animal model demonstrates that these proliferative changes are completed by 48 h and thereafter are balanced by apoptosis as the glands recover their normal size and weight.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00196524
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    Localization and coexistence of atrial natriuretic peptide (ANP) and neuropeptide Y (NPY) in vertebrate adrenal chromaffin cells immunoreactive to TH, DBH and PNMT (1995)
    Springer
    Cell & tissue research 280 (1995), S. 267-276 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Adrenal organ ; Atrial natriuretic peptide ; Neuropeptide Y ; Catecholamine synthesizing enzymes ; Coexistence ; Rat ; Guinea pig ; Coturnix c. japonica (Aves ; Phasianiformes) ; Lacerta viridis (Lacertilia) ; Bufo marinus ; Caldula pulchra (Anura) ; Cyprinus carpio ; Cottus scorpius (Teleostei)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Antisera specific for mammalian atrial natriuretic peptide (ANP) and neuropeptide Y (NPY) were applied to examine, in immunofluorescence, the occurrence of cells immunoreactive to ANP and NPY in the adrenal organs of mammals, birds, reptiles, amphibians, and bony fish. Catecholamine-containing cells were identified using antisera against tyrosine-hydroxylase, dopamine-β-hydroxylase, and phenylethanolamine-N-methyl-transferase. In all vertebrates studied, immu- noreactivities to ANP and NPY occurred in adrenal chromaffin cells but were absent from the cortex or its homolog, the interrenal. The majority of immunoreactivities to ANP and NPY was confined to the adrenaline cells. In mammals, the number of ANP-immuno-reactive cells (60%–80% of the total cell population) exceeded that of the NPY-immunoreactive cells (35%–45%). In birds, reptiles, and Amphibia, the numbers of ANP-immunoreactive (35%–40%) and NPY-immunoreactive (30%–35%) cells were in a similar range. The bony fish showed a density of both ANP-immunoreactive (80%–90%) and NPY-immunoreactive (35%–40%) cells. In all species studied, immunoreactivities to ANP and NPY partially coexisted. Generally, 30%–55% of the ANP-immunoreactive cells also contained NPY-immunoreactivity. In rat, coexistence amounted to almost 100% and in quail to 95%. Except for the rat, three subpopulations of chromaffin cells seemed to occur: ANP-immunoreactive non-NPY-immunoreactive, ANP-immunoreactive+NPY-immunoreactive, and NPY-immunoreactive non-ANP-immunoreactive cells. Thus, adrenal ANP and NPY share a conservative history and coexist as early as at the level of bony fish. The endocrine actions of ANP and NPY derived from medullary cells on cortical cells as found in mammals might be based on an ancestoral paracrine system. In submammalians, ANP and NPY may not only act as endocrine hormones, but also influence steroid-producing interrenal cells in a paracrine manner, and act as modulators on chromaffin cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00307798
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    Pro-enkephalin opioid peptides are abundant in porcine and bovine splenic nerves, but absent from nerves of rat, mouse, hamster, and guinea-pig spleen (1995)
    Springer
    Cell & tissue research 281 (1995), S. 143-152 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Enkephalin ; Opioid peptides ; Spleen ; Innervation ; Neuro-immunology ; Species differences ; Immunohistochemistry ; Cow ; Pig ; Guinea-pig ; Mouse ; Rat ; Dsungarian hamster
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The opioidergic innervation of the mammalian spleen and possible species differences were investigated. Light-microscopic immunohistochemistry revealed that splenic nerves of bovine and porcine spleen, but not of rat, mouse, hamster and guinea-pig spleen contained proenkephalin-derived opioidergic innervation. Immunoreactivity to both prodynorphin and pro-opiomelanocortin was absent from splenic nerves. In bovine and porcine spleen, fibers immunoreactive for met-enkephalin, met-enkephalin-Arg-Phe, met-enkephalin-Arg-Gly-Leu, leu-enkephalin and peptide F formed perivascular plexus, traveled in trabecular connective tissue, and extended into the capsule. Spatial relationships with immune cells were apparent in the white and red pulp, excluding lymphoid follicles. Colocalization of enkephalin immunoreactivity with immunoreactivities for tyrosin hydroxylase, dopamin-β-hydroxylase, and neuropeptide Y, but not for substance P or calcitonin gene-related peptide were found. Our results provide evidence that opioid expression in splenic innervation is strongly species-dependent and exclusively proenkephalin-derived. Colocalization with marker enzymes of noradrenergic neurons indicates a mainly postganglionic sympathetic origin of proenkephalinergic splenic innervation. Opioidergic perivascular nerves probably control the splenic blood flow. A close interrelationship of opioidergic fibers with immune cells provides the anatomical basis for direct effects of neurally released opioids on splenic immune functions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00307968
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  • 145
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    Localization and coexistence of atrial natriuretic peptide (ANP) and neuropeptide Y (NPY) in vertebrate adrenal chromaffin cells immunoreactive to TH, DBH and PNMT (1995)
    Springer
    Cell & tissue research 280 (1995), S. 267-276 
    Details
    ISSN: 1432-0878
    Keywords: Adrenal organ ; Atrial natriuretic peptide ; Neuropeptide Y ; Catecholamine synthesizing enzymes ; Coexistence ; Rat ; Guinea pig ; Coturnix c. japonica (Aves, Phasianiformes) ; Lacerta viridis (Lacertilia) ; Bufo marinus, Caldula pulchra (Anura) ; Cyprinus carpio, Cottus scorpius (Teleostei)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Antisera specific for mammalian atrial natriuretic peptied (ANP) and neuropeptide Y (NPY) were applied to examine, in immunofluorescence, the occurrence of cells immunoreactive to ANP and NPY in the adrenal organs of mammals, birds, reptiles, amphibians, and bony fish. Catecholamine-containing cells were identified using antisera against tyrosine-hydroxylase, dopamine-β-hydroxylase, and phenylethanolamine-N-methyl-transferase. In all vertebrates studied, immunoreactivities to ANP and NPY occurred in adrenal chromaffin cells but were absent from the cortex or its homolog, the interrenal. The majority of immunoreactivities to ANP and NPY was confined to the adrenaline cells. In mammals, the number of ANP-immuno-reactive cells (60%–80% of the total cell population) exceeded that of the NPY-immunoreactive cells (35%–45%). In birds, reptiles, and Amphibia, the numbers of ANP-immunoreactive (35%–40%) and NPY-immunoreactive (30%–35%) cells were in a similar range. The bony fish showed a density of both ANP-immunoreactive (80%–90%) and NPY-immunoreactive (35%–40%) cells. In all species studied, immunoreactivities to ANP and NPY partially coexisted. Generally, 30%–55% of the ANP-immunoreactive cells also contained NPY-immunoreactivity. In rat, coexistence amounted to almost 100% and in quail to 95%. Except for the rat, three subpopulations of chromaffin cells seemed to occur: ANP-immunoreactive non-NPY-immunoreactive, ANP-immunoreactive+NPY-immunoreactive and NPY-immunoreactive non-ANP-immunoreactive cells. Thus, adrenal ANP and NPY share a conservative history and coexist as early as at the level of bony fish. The endocrine actions of ANP and NPY derived from medullary cells on cortical cells as found in mammals might be based on an ancestoral paracrine system. In submammalians, ANP and NPY may not only act as endocrine hormones, but also influence steroid-producing interrenal cells in a paracrine manner, and act as modulators on chromaffin cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00307798
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    Pro-enkephalin opioid peptides are abundant in porcine and bovine splenic nerves, but absent from nerves of rat, mouse, hamster, and guinea-pig spleen (1995)
    Springer
    Cell & tissue research 281 (1995), S. 143-152 
    Details
    ISSN: 1432-0878
    Keywords: Enkephalin ; Opioid peptides ; Spleen ; Innervation ; Neuro-immunology ; Species differences ; Immunohistochemistry ; Cow ; Pig ; Guinea-pig ; Mouse ; Rat ; Dsungarian hamster
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The opioidergic innervation of the mammalian spleen and possible species differences were investigated. Light-microscopic immunohistochemistry revealed that splenic nerves of bovine and porcine spleen, but not of rat, mouse, hamster and guinea-pig spleen contained proenkephalin-derived opioidergic innervation. Immunoreactivity to both prodynorphin and pro-opiomelanocortin was absent from splenic nerves. In bovine and porcine spleen, fibers immunoreactive for met-enkephalin, met-enkephalin-Arg-Phe, met-enkephalin-Arg-Gly-Leu, leu-enkephalin and peptide F formed perivascular plexus, traveled in trabecular connective tissue, and extended into the capsule. Spatial relationships with immune cells were apparent in the white and red pulp, excluding lymphoid follicles. Colocalization of enkephalin immunoreactivity with immunoreactivities for tyrosin hydroxylase, dopamin-β-hydroxylase, and neuropeptide Y, but not for substance P or calcitonin gene-related peptide were found. Our results provide evidence that opioid expression in splenic innervation is strongly species-dependent and exclusively proenkephalin-derived. Colocalization with marker enzymes of noradrenergic neurons indicates a mainly postganglionic sympathetic origin of proenkephalinergic splenic innervation. Opioidergic perivascular nerves probably control the splenic blood flow. A close interrelationship of opioidergic fibers with immune cells provides the anatomical basis for direct effects of neurally released opioids on splenic immune functions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00307968
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  • 147
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    Effect of exposure to oxygen at 101 and 150 kPa on the cerebral circulation and oxygen supply in conscious rats (1995)
    Springer
    European journal of applied physiology 71 (1995), S. 475-484 
    Details
    ISSN: 1439-6327
    Keywords: Cardiovascular changes ; Hyperbaric O2 ; Microspheres ; Rat ; Regional cerebral blood flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Hyperbaric oxygen at pressures of 300 to 500 kPa has been shown to induce changed distribution of cerebral blood flow ( $$\dot Q$$ CBF) in rats, in places reducing the supply of the supplementary O2. Thus, in the present study, the effect of hyperoxia at 101 (group 1, n = 9) and 150 (group 2, n = 9) kPa OZ on cerebral blood flow distribution and central haemodynamics was tested in conscious, habituated rats. During the control period the systolic arterial pressure (BPs), heart rate (f c), breathing frequency (f b), cardiac output ( $$\dot Q$$ c), arterial acid-base chemistry and glucose, as well as $$\dot Q$$ CBF distribution (r $$\dot Q$$ CBF) were similar in the two groups of animals. During O2 exposure, the acid-base chemistry remained unchanged. The haemoglobin decreased in group 2, but remained unchanged in group 1. The f c decreased rapidly in both groups during the change in gas composition, after which f c remained constant both in group 1 and in group 2, for whom pressure was increased. The $$\dot Q$$ c and f b decreased and BPs increased similarly in the two groups. Total $$\dot Q$$ CBF and r $$\dot Q$$ CBF decreased to the same extent in both groups, and the r $$\dot Q$$ CBF changes were equally scattered. In group 1, breathing of pure O2 did not increase the O2 supply to any cerebral region except to the thalamus and colliculi after 60 min, whereas the O2 supply to the hypothalamus decreased and remained low. In group 2, the O2 supply was unchanged compared to the control period in all regions. These findings agree with previous observations during exposures to higher O2 pressures. In air after O2 exposure the acid-base chemistry remained normal. The f c and f b increased to higher levels than during the control period. The BPs remained high. The brain blood flows were increased, inducing elevated O2 supply to several brain regions compared to the control period. In conclusion, O2 supply to the central nervous system was found to be in the main unchanged during breathing of O2 at 101 kPa and 150 kPa.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238548
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  • 148
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    Growth, hormonal status and protein turnover in rats fed on a diet containing peas (Pisum sativum L.) as the source of protein (1995)
    Springer
    Plant foods for human nutrition 47 (1995), S. 211-220 
    Details
    ISSN: 1573-9104
    Keywords: Hormonal status ; Legume diet ; Pisum sativum L. ; Protein turnover ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The inclusion of peas (Pisum sativum L.) as the source of protein in the diet of growing rats brings about a reduction in growth rate as well as the impairment in the liver, muscle and spleen weights as compared with casein fed controls. Also, a fall in plasma glucose, triglycerides and protein was observed in the legume fed animals, while no changes in cholesterol levels were found. Furthermore, the rats fed on the diet containing peas showed lower levels of plasma insulin, corticosterone, IGF-I and T4 as compared with casein controls. Liver and muscle total protein (mg) and total DNA (mg) were markedly decreased in the legume fed animals, but DNA/g, protein/DNA and RNA/protein ratios were similar in both dietary groups. Likewise, liver and muscle fractional synthesis rates were similar in the casein and legume groups, while the whole body protein synthesis is assumed to be lower in the legume fed animals due to differences in body weights. It is concluded that animals fed on a diet containing peas (Pisum sativum L.) as the only source of protein showed less adverse effects than those found with other legumes such asVicia faba L. orPhaseolus vulgaris L., in which protein quality, antinutritional factors and nutrient availability could be involved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01088329
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  • 149
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    Effect of infra-red low-power laser irradiation on regeneration of myelinated axons (1995)
    Springer
    Lasers in medical science 10 (1995), S. 273-277 
    Details
    ISSN: 1435-604X
    Keywords: Ga-As laser ; Myelinated fibre regression ; Rat ; Sciatic nerve
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract The purpose of the present study was to examine the regeneration of myelinated axons under the effect of laser irradiation at various wavelengths and energy densities. Laser irradiation at 890 nm with an energy dose of 0.33 J cm−2 as well as He-Ne laser irradiation failed to change the number of regenerating myelinated axons in distal nerve stumps on the 30th day after cutting the nerve. An increase of dose delivered to the skin to 9.33 J cm−2 resulted in a 49% decrease in the number of myelinated axons. A 24% suppression of nerve regeneration was also registered using 1220 nm wavelength laser (dose 0.98 J cm−2). This phenomenon is likely to be attributed to the stimulating effect of laser irradiation of the near-infra-red range on proliferation of fibroblasts and scar formation. 1220 nm of 7.2 J cm−2 dose effected neither the growth nor the myelinization of axons in distal nerve stumps on the 20th day following nerve damage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02133620
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  • 150
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    Optimization of mechanical strength of reinforced composites. 1. Study on the effect of reactive bismaleimide on the mechanical performance of CaCo3-filled polypropylene (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 224 (1995), S. 9-20 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Der Einfluß von 3-Phenylenbismaleimid auf die Werkstoffeigenschaften von CaCO3 gefüllten Polypropylen-Verbundstoffen wurde untersucht. Die Verarbeitungstemperatur spielte eine entscheidende Rolle bei der Herstellung der Verbundwerkstoffe. Bei Verarbeitungstemperaturen oberhalb der Bismaleimid-Zersetzungstemperatur zeigte die Bismaleimid-Verbindung einen positiven Effekt. Die chemische Zusammensetzung der modifizierten Verbunde wurde mit den mechanischen Eigenschaften korreliert. Basierend auf ESCA-Analysen werden Wechselwirkungen zwischen dem Polymeren und CaCO, diskutiert.
    Notes: The effect of 3-phenylene bismaleimide on the mechanical performance of an inorganic filler-based polypropylene composite was studied. The selection of processing temperature played a significant role in the preparation of such composites. A positive effect of the bismaleimide compound was obtained for a processing temperature above the decomposition temperature of bismaleimide. The chemical composition of the modified composite was correlated to its mechanical strength by experimentation involving a rotatable design. An interaction between polymer and CaCO3 has been proposed based on ESCA analysis.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052240102
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  • 151
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    The effect of the processing steps on the oxidative stability of polyethylene tubing crosslinked by irradiation (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 224 (1995), S. 33-48 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Chemische und mechanische Eigenschaften von Zwischenprodukten der PE-Schrumpfschlauch-Produktion wurden bei unterschiedlichen Compound-Zusammensetzungen (PE, ein aromatisches Amin oder Phenolderivat als Antioxidans und in einigen Fällen ein Flammschutzmittel und/oder eine Elastomerkomponente) untersucht.Während der Herstellung, besonders während der durch Elektronenstrahlung initiierten Vernetzung, nimmt die thermooxidative Stabilität des Materials gegenüber der des compoundierten Granulats ab. Das aromatische Amin scheint bei gleicher Zusammensetzung das wirksamere und strahlungsbeständigere Antioxidans im Vergleich zum Phenolderivat zu sein. Die Oxidationsstabilität der hergestellten Schrumpfschläuche wird nicht von der Qualität des eingesetzten PE-Ausgangsgranulats beeinflußt.Durch die Alterung des Materials ändern sich die mechanischen Eigenschaften geringfügig. Die Elastomerzugabe bewirkt keine Änderung von Zugfestigkeit und Reißdehnung. Die Stabilität des Endprodukts ist bei weitem ausreichend, um den Spannungen, die beim Schrumpfen während des Gebrauchs auftreten, standzuhalten. Die gute Zugfestigkeit des Materials wird durch die Alterung ebenfalls nicht beeinträchtigt.Bei der Extrusion des Granulats tritt keine nennenswerte Änderung des Molekulargewichts bzw. der Molekulargewichtsverteilung auf. Durch die Bestrahlung wird das Material vernetzt und zu mehr als 50% unlöslich, und seine thermooxidativen Eigenschaften ändern sich deutlich gegenüber dem ursprünglichen PE und dem daraus compoundierten Material.
    Notes: Some chemical and mechanical properties of intermediate products obtained in the production of PE heat-shrinkable tubes were studied at different compositions of the material containing PE, antioxidant (aromatic amime or phenol) and, in some cases, flame retardant and/or an elastomer.In the course of the production phase, the thermooxidative stability decreases compared to that of compounded granulate. The greatest decrease is caused by irradiation. The aromatic amine seems to be a more effective antioxidant at similar compositions than the phenol derivative, and it shows a better resistance against irradiation. The oxidative stability of the finished shrinkable tubes is not affected by the quality of commercial granulate (initial polyethylene).Mechanical properties change slightly upon ageing, and the introduction of the elastomer did not alter the tensile strength and elongation at break. The remaining stability of the end product was still high enough to bear the stress of shrinking in use, and the good tensile strength of the material did not decrease upon thermal ageing either.In the extrusion of the granulated compound no significant change in the distribution and average molecular weight took place. Irradiation produced more than 50% insoluble fraction and the thermooxidative properties of the crosslinked sample changed significantly compared to the original PE and to the compound prepared from it.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052240104
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  • 152
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    Thermogravimetrie als brennbarkeitsbestimmungs-methode für lineare polyurethane (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 224 (1995), S. 89-96 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: In the present work oxygen index (OI) measurements and thermogravimetric analysis (TG) for a series of polyurethanes based on diols and isocyanate were conducted. It was found that a correlation exists between some of the thermal degradation parameters obtained from TG and OI-values. Analysis of experimental results confirms that the amount of mass loss at 250°C is directly proportional to the OI-value. It was also found that the logarithmic temperatures of maximal decomposition rates are directly proportional to the OI-values.
    Notes: In der vorliegenden Arbeit wurden für eine Serie von Polyurethanen auf der Basis von Diol und Isocyanat der Sauerstoffindex (SI) gemessen und die thermische Zersetzung mittels thermogravimetrischer Analyse (TG) untersucht. Dabei wurde ein Zusammenhang zwischen einigen Parametern der thermischen Zersetzung und den SI-Werten gefunden. Die Auswertung der experimentellen Ergebnisse zeigte, daß die Höhe des Massenverlustes bei 250°C und die SI-Werte direkt proportional zueinander sind. Derselbe Zusammenhang besteht auch zwischen dem Logarithmus der Temperatur bei der maximalen Zersetzungsgeschwindigkeit und den SI-Werten.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052240109
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  • 153
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    Studies on thermal stability of modified polycarboxylate cements (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 224 (1995), S. 109-114 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Poly(acrylsäre-co-acrylamid) wurde mit Zinkoxid und Kryolith (Na3AlF6) in unterschiedlichen Verhältnissen gemischt und bei Raumtemperatur zu Zahnzementen ausgehärtet. IPDT, Temperaturen bei maximaler Abbaugeschwindigkeit, Aktivierungsenergien und Frequenzfaktoren des thermischen Abbaus der Proben wurden aus thermogravimetrischen Messungen ermittelt. Die Probe mit 20 Gew.-% Kryolith in der Füllstoffmischung ist thermisch sehr stabil.
    Notes: Dental cement compositions made by mixing poly(acrylic acid-co-acrylamide) and mixtures of zinc oxide and cryolite (Na3AIF6) in various proportions of 10-50 wt.-% (w/w) were cured at room temperature. From thermogravimetric analyses of the samples, the integral procedural decomposition temperatures (IPDT), maximum decomposition temperatures, activation energies and frequency factors were evaluated. The cured cement sample containing 20 wt.-% cryolite in the filler mixture is thermally very stable.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052240111
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  • 154
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    Synthesis and characterization of water-soluble diazonium salts as contrast-enhancement materials (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 224 (1995), S. 133-144 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die wasserlöslichen aromatischen Diazonium-Doppelsalze p-Diazodiphenylaminchlorid/Zinkchlorid (DZS-1) und p-Diazoanisolchlorid/Zinkchlorid (DZS-2) wurden auf ihre Verwendbarkeit als photobleichbare Farbstoffe in der Kontrastverstärkungslithographie untersucht. Nach Untersuchung der Bleicheigenschaften der hergestellten Salze wurde DZS-1 in wäßrigen Lösungen mit Poly(vinylalkohol) als Kontrastverstärkungssystem eingesetzt. Die thermische Stabilität, der Resistkontrast, die Bestrahlungsparameter und andere Bleicheigenschaften wurden untersucht. Im Vergleich zu einem handelsüblichen i-Linien-Photoresist beträgt das Kontrastverhältnis der DZS-1/PVA CEL-Schicht 1,67.
    Notes: Water soluble aromatic diazonium double salts, p-diazodiphenylamine chloride zinc chloride (DZS-1) and p-diazoanisol chloride zinc chloride (DZS-2), have been evaluated as photobleachable dyes for contrast enhancement lithography. After testing the bleaching characteristics, aqueous solutions of DZS-1 and poly(vinyl alcohol) were used as a contrast enhancement material. Thermal stability, resist contrast, exposure parameters and other bleaching characteristics of the photobleachable membranes were investigated. A. commercial i-line photoresist was used to evaluate the contrast ratio of the DZS-1/PVA CEL layer. The contrast ratio obtained in this investigation is 1.67.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052240114
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    Comparison of the coupling behaviour of diisocyanate and bisoxazolines in modification of liquid crystalline poly(ethylene terephthalate-co-oxybenzoate)s (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 224 (1995), S. 167-178 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Methylen-4,4′-diphenyldiisocyanat und zwei unterschiedliche Bisoxazoline wurden für Kopplungsreaktionen in mit Carboxygruppen terminierten flüssigkristallinen Poly(ethylenterephthalat-co-oxybenzoat)en eingesetzt. Um definierte Bedingungen zu gewährleisten, erfolgte die Synthese von Copolyestern mit unterschiedlichen Carboxygruppenkonzentrationen. Die Bestimmung des Carboxygruppengehalts wird beschrieben.Es erfolgt ein Vergleich des Kopplungsverhaltens beider Arten von Kettenverlängerern. Es konnte nachgewiesen werde, daß die Bisoxazoline bedeutend schneller reagieren als das Diisocyanat. Durch einen geringen Überschuß and Bisoxazolin in der Reaktionsmischung konnte einer thermischen Schädigung vorgebeugt werden. Abhängig von der Menge an zugegebenem Koppler wurden bei den modifizierten Copolyestern Oxazolinendgruppen beobachtet. Außerdem werden mögliche Vernetzungsreaktionen und die thermische Stabilität diskutiert.
    Notes: Methylene-4,4′-diphenyldiisocyanate and two different bisoxazolines were used for coupling reactions in carboxy-terminated liquid crystalline poly(ethylene terephthalate-co-oxybenzoate). In order to guarantee defined conditions, copolyesters with different carboxylic group concentrations were synthesized. The determination of the carboxylic group content is described.The coupling behaviour of both types of chain extenders has been compared. It was evidenced that the bisoxazolines reacted significantly faster than the diisocyanate. A slight excess of bisoxazoline in the reaction mixture prevented thermomechanical degradation. Depending on the amount of coupling agent added, an oxazoline termination of the copolyester was observed. Additionally, probable crosslinking reactions and the thermal stability have been discussed.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052240117
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    Announcements (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 224 (1995), S. 201-201 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052240120
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  • 157
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    Optimization of mechanical strength of reinforced composites. 2. Reactive bismaleimide-modified polypropylene composites filled with talc and zeolitePart 1 cf.2. (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 225 (1995), S. 11-20 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Der Einfluß von 3-Phenylenbismaleimid auf die Werkstoffeigenschaften von mit Talkum und Zeolith gefüllten Polypropylen-Verbundstoffen wurde untersucht. Durch geeignete Planung des Aufbaus kann die Produkteigenschaft optimiert werden. Die Kapazität zur Füllstoffaufnahme schwankt bei Polypropylen je nach Art des Füllstoffs. Ein hochbelastbarer Verbundstoff kann aus einem geeignet modifizierten, mit Zeolith gefüllten Polypropylen hergestellt werden, auch wenn der Füllstoff in der Verbundmatrix dominiert. Als Ursache dieser Verstärkung wird eine verbesserte Wechselwirkung zwischen dem Polymeren und dem Füllstoff angenommen.
    Notes: The effect of 3-phenylene bismaleimide as a modifier for talc and zeolite-filled polypropylene composites has been studied. The usefulness of the experimental design to assure best product properties has also been illustrated. Polypropylene shows a variable degree of filling capacity depending on the type of filler. A high-strength composite can be prepared with suitably modified zeolite-filled polypropylene even if filler is the dominant phase in the composite matrix. An improved interfacial interaction between polypropylene and filler is proposed to be the reason for this improvement of strength.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052250102
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  • 158
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    Oligomerization of 1-decene with Ziegler-Natta catalysts (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 225 (1995), S. 51-61 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die katalytische Oligomerisation von 1-Decen wurde mit Komplexverbindungen mehrerer Übergangsmetalle (Co(II), Co(III), Zr(IV), Ti(IV), Cr(III), V(V)) und Alkyl-aluminiumhalogeniden als Cokatalysatoren durchgeführt. Mit einem Chrom(III)-Et3Al2Cl3-Katalysatorsystem konnten Dimere (C20), Trimere (C30) und Tetramere (C40) von 1-Decen erhalten werden. Die kinematischen Viskositäten und Fließpunkte der hydrierten Oligomere wurden bestimmt und mit den Werten handelsüblicher Proben verglichen. Ein Mechanismus für die Oligomerisation von 1-Decen mit diesem Katalysatorsystem wird vorgeschlagen.
    Notes: The catalytic oligomerization of 1-decene has been carried out employing several transition metal complexes of Co(II), Co(III), Zr(IV), Ti(IV), Cr(III), V(V) in combination with alkyl aluminum halides as cocatalysts. The chromium(III)-Et3Al2Cl3 system exhibits good oligomerizing activity yielding dimers (C20), trimers (C30) and tetramers (C40) of 1-decene. The kinematic viscosities and pour points of hydrogenated oligomers have been determined and compared with those of commercial samples. The probable mechanism of oligomerization of 1-decene on this catalyst is described.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052250105
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  • 159
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    Zur Häurtung von Bisphenol-A-diglycidether mit Dicyandiamid in Gegenwart von Beschleuniger-Addukten (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 225 (1995), S. 99-107 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Single-component formulations of epoxy resins with reactive accelerators must be storable. The preparation of several blocked accelerators is described. The basicity of tertiary amines, which correlates with accelerating effects, as well as acidity and structure of polyphenols and modified novolacs influences the extend of blocking. The curing process was investigated by measurements of gel time and viscosity.
    Notes: Einkomponentige Epoxidharzsysteme mit effizienten Reaktionsbeschleunigern müssen lagerstabil sein. Daher wurden Versuche unternommen, Beschleuniger auf Basis von tertiären Aminen mit modifizierten Phenolnovolaken zu blockieren. Das Ausmaß der Blockierung ist sowohl von der Basizität der Amine, die mit der beschleunigenden Wirkung korreliert, als auch von der Acidität und dem strukturellen Aufbau der modifizierten Phenole abhängig. Die Bewertung der Härtungseigenschaften erfolgte über Gelzeitbestimmungen und Viskositätsmessungen.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1995.052250109
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    Comparison of the crack growth method and the crack stress whitening zone method for the fracture toughness determination of phenolphthalein poly(ether ketone)Key Project of the National Natural Science Foundation of China. (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 225 (1995), S. 131-138 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Bruchzähigkeit von Phenolphthalein-Poly(etherketon) bei 190°C wurde mit zwei verschiedenen Methoden bestimmt, der konventionellen Rißwachstumsmethode und der „stress whitening zone“-Methode. Die gute Übereinstimmung der Ergebnisse zeigt, daß letztere Methode zur Bestimmung der Rißinitiierung einiger Polymerer herangezogen werden kann, für die das „blunting line concept“ nicht geeeignet ist.
    Notes: Fracture toughness values of phenolphthalein poly(ether ketone) (PEK-C) at 190°C were determined by two different methods, i.e. the conventional crack growth method and the crack stress whitening zone method, which show consistent results. This indicates that the crack stress whitening zone method can be used to determine the crack initiation of some polymers for which the blunting line concept is unsuitable.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1995.052250112
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  • 161
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    Thermodynamic studies on some interpolymer interactions and stability of polycomplexes (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 226 (1995), S. 13-22 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Stabilitätskonstanten und zugehörige thermodynamische Parameter (ΔH°, ΔS°) eines intermakromolekularen Komplexes aus Poly(acrylsäure-co-acrylamid), Poly(methacrylsäure-co-acrylamide) und Poly(N-vinylpyrrolidon) wurden mit bekannten Methoden bei verschiedenen Temperaturen bestimmt. Dabei wurde eine stufenweise Auflösung des Komplexes in Abhängigkeit von der Temperatur beobachtet, die mit den Stabilitätskonstanten und den thermodynamischen Parametern korreliert wurde.
    Notes: Stability constant and related thermodynamic parameters (ΔH° and ΔS°) of a multicomponent intermacromolecular complex consisting of poly(acrylic acid-coacrylamide), poly(methacrylic acid-co-acrylamide) and poly(N-vinylpyrrolidone) have been determined using known methods. A distinct stepwise disintegration of the complex at different temperatures has been observed, and this could be correlated with the stability constant and thermodynamic parameters calculated at various temperatures.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1995.052260102
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  • 162
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    The effect of ultrasound in ethyl methacrylate polymerization and depolymerization reactions (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 226 (1995), S. 53-57 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Der Einfluß von Ultraschall auf die Polymerisation und Depolymerisation von Ethylmethacrylat und der Mechanismus des Kettenabbruchs wurden untersucht. Der Polymerisationsumsatz war unabhängig von den verwendeten Ultraschallbedingungen (800 W, 35 kHz). Depolymerisationsversuche mit Ultraschall bei 20°C zeigten, daß Kettenabbruch im wesentlichen durch Disproportionierung stattfindet; dabei werden Molekulargewichte nicht unter ca. 500000 erreicht.
    Notes: The effect of ultrasound in ethyl methacrylate polymerization and depolymerization and the chain termination mechanism for ethyl methacrylate have been studied. Polymerization conversion at 60°C did not depend on energy (80 W) and frequency (35 kHz) of ultrasound applied. In ultrasound depolymerization studies at 20°C the governing termination mechanism was found to be disproportionation and the lower limiting molecular weight was Mn = 500 000.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1995.052260106
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  • 163
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    Reaktive membrancopolymere auf acrylbasis (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 226 (1995), S. 71-87 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The copolymerization of acrylonitrile with maleic anhydride was investigated to synthesize acylic reactive polymers for manufacture of membranes that serve as support for covalent enzyme immobilization. The free-radical copolymer synthesis was carried out in solution (N,N-dimethylformamide (DMF), dimethylacetamide (DMAC), γ-butyrolactone, ethylene carbonate), by precipitation polymerization (dioxane) as well as bulk polymerization. The polymers were characterized using IR spectroscopy, elementary analysis, NMR spectroscopy, gel permeation chromatography, viscosity measurements, osmometry and potentiometry.The kinetic parameters were followed by dilatometric measurements up to high conversions. The anhydride content in the monomer mixtures showed a significant influence on the rate of polymerization and the molecular weight. With raised concentration of anhydride the polymerization rate and molecular weights decreased. Film forming polymers (M̄η 〉 30 000 g/mol) can be obtained by all copolymerization procedures with exception of solution polymerization in DMF and DMAC, respectively. The content of maleic anhydride in the membrane polymers did not exceed 5 mol-%, even though the maleic anhydride content in the monomer mixtures was raised up to the equimolar mixture. Nevertheless, such low maleic anhydride content of prepared membranes is enough for successful enzyme immobilization with amyloglucosidase (copolymer was prepared in γ-butyrolactone, M̄η = 49 000 g/mol, cPMSA = 0,3 mol-%).
    Notes: Die Copolymerisation des Acrylnitrils mit Maleinsäureanhydrid (MSA) wurde mit dem Ziel untersucht, acylfunktionalisierte Reaktivpolymere mit Filmbildungseigenschaften herzustellen, um diese in der Anwendung als Membran für kovalente Enzymfixierungen zu nutzen. Die radikalinitiierte Synthese der Copolymeren wurde in Lösung (Dimethylformamid (DMF), Dimethylacetamid (DMAC), γ-Butyrolacton, Ethylencarbonat), durch Fällungscopolymerisation (Dioxan) sowie in Substanz durchgeführt.Die Polymercharakterisierung erfolgte durch IR-Spektroskopie, Elementaranalyse, Kernresonanzspektroskopie, Gelpermeationschromatographie, Viskosimetrie, Osmometrie und Potentiometrie.Die Kinetik wurde durch dilatometrische Untersuchungen bis zu hohen Umsätzen verfolgt. Danach weist der Anhydridgehalt im Monomergemisch einen signifikanten Einfluß auf die Bruttopolymerisationsgeschwindigkeit und die Molmasse der Polymeren auf. Mit steigendem Anhydridanteil wird die Bruttopolymerisationsgeschwindigkeit herabgesetzt und eine Verringerung der Molmasse herbeigeführt. Die Copolymerisation von Acrylnitril und Maleinsäureanhydrid führt mit Ausnahme der Lösungspolymerisation in DMF bzw. DMAC zu Polymeren mit Molmassen oberhalb 30 000 g/mol, was ihre Anwendung als Membran ermöglicht. Die Einbaurate an Maleinsäureanhydrid in den Membranpolymeren ist bis einschließlich einer äquimolaren Zusammensetzung des Monomergemischs nicht größer als 5 mol-%. Derartig niedrige MSA-Reaktivgruppenanteile erweisen sich jedoch als ausreichend, um an einer aus einem Lösungspolymerisat (γ-Butyrolacton, M̄η = 49 000 g/mol, cPMSA = 0,3 mol-%) formierten Membran eine Enzymimmobilisierung mit Amyloglucosidase nachzuweisen.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1995.052260108
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    Synthesis and characterization of photopolymers with azo units. Interfacial polyaddition, photolysis, photodegradation (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 226 (1995), S. 143-160 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Synthesen einer Aryl-alkyl-azodiisocyanat-Verbindung und einer Azoharnstoff-Modellsubstanz werden beschrieben. Aus dem Azodiisocyanat wurden durch Grenzflächen-Polyaddition neuartige Azoharnstoff-Polymer hergestellt. Die zahlenmittleren Molekulargewichte, bestimmt mit der Gelpermeationschromatographie (GPC), lagen zwischen 6000 und 9000. Die Photolyse- und Thermolysereaktionen der Modellsubstanzen und der Polymeren wurden mittels UV-Spektroskopie und Differentialkalorimetrie (DSC) verfolgt und mit den Ergebnissen von ähnlichen Azoamiden verglichen. Der photochemische Polymerabbau wurde mittels GPC untersucht.
    Notes: The synthesis of an aryl alkyl azo diisocyanate and a model azo urea is described. From the azo diisocyanate new azo polyureas were created by interfacial polyaddition. Molecular weights Mn in the range of 6000 to 9000 were determined by gel permeation chromatography (GPC). Photolysis and thermolysis of both, model compounds and polymers, were studied by UV-spectroscopy and differential scanning calorimetry (DSC), respectively, and the results were compared with those of similar azo amides. Photochemical polymer degradation was followed by GPC.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1995.052260113
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    Announcements (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 226 (1995), S. 219-219 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052260120
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  • 166
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    Molecular structure of liquid-crystalline copolyesters of vanillic acid, 4-hydroxybenzoic acid and poly(ethylene terephthalate) (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 227 (1995), S. 69-85 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Thermotrop flüssigkristalline Copolyester aus Vanillinsäure (V), 4-Hydroxybenzoesäure (B) und Polyethylenterephthalat (E) wurden mittels 1H-NMR-Spektroskopie und Gelpermeationschromatographie (GPC) untersucht. Die neun möglichen Diaden konnten detektiert und zugeordnet werden. Die Abfolge der Grundeinheiten der V/B/E-Copolyester ändert sich mit zunehmendem B-Anteil von statistischer Verteilung zur Blockbildung und ist außerdem geringfügig von der Katalysatorkonzentration und der Polykondensationsdauer abhängig. Die GPC-Ergebnisse deuten darauf hin, daß die V/B/E-Copolyester engere Molekulargewichtsverteilungen aufweisen als die B/E-Copolyester. Mit von 0 bis 5 mol-% steigendem V-Anteil verengt sich die Molekulargewichtsverteilung. Die Gelpermeationschromatogramme der meisten V/B/E-Copolyester weisen im Unterschied zu den Einzelsignalen der B/E-Copolyester Dublett-Peaks auf.
    Notes: Thermotropic liquid-crystalline copolyesters made from vanillic acid (V), 4-hydroxybenzoic acid (B) and poly(ethylene terephthalate) (E) were examined by 1H-NMR and GPC investigations. Nine possible diads could be identified and assigned. The sequence distribution of V/B/E copolyesters tends to change from random to block with an increase of B content in the copolyesters. The sequence distribution also varies slightly with catalyst concentration and polycondensation time. GPC results suggest that the V/B/E copolyesters have narrower molecular weight distribution (MWD) than B/E copolyesters. The MWD of the copolyesters narrows gradually with increasing V content from zero to 5 mol-%. The GPC chromatograms of the most V/B/E copolyesters show double peaks, which is different from the single peak of the GPC chromatograms of the B/E copolyesters.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1995.052270108
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    Effect of pre-irradiation on radiation stability of co-polypropylene (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 227 (1995), S. 111-120 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Strahlungsbeständigkeit von vorbestrahltem Polypropylen mit 2,5 Gew.-% Ethylenanteil wurde mitr einem Copolymeren aus Polypropylen und einem nukleierenden Agens im Hinblick auf die Strahlungssterilisation von medizinischen Geräten verglichen. Die Transparenz des Propylen-Ethylen-Copolymeren wurde durch die Vorbehandlung verbessert. Im Vergleich mit der ebenfalls verbesserten Transparenz des Copolymeren aus Polypropylen und dem nukleierenden Agens wurde durch die Vorbestrahlung die Strahlungsbeständigkeit während der Bestrahlung und bei der Lagerung des bestrahlten Materials verbessert. Dies wird auf die geringere Kristallinität des vorbestrahlten Polypropylens aufgrund von bei der Bestrahlung gebildeten Verzweigungen zurückgeführt.
    Notes: The radiation stability of the pre-irradiated copolymer of polypropylene containing 2.5 wt.-% ethylene units is compared with a copolymer of polypropylene with a nucleating agent with regard to radiation sterilization of medical devices. It is found that transparency property of the propylene-ethylene copolymer is improved through pre-irradiation processes. This finding was compared with the co-polypropylene with nucleating agent which also gives a better transparency property. In comparison, it is found that pre-irradiated copolymer exhibits better radiation stability during irradiation and during storage after irradiation. The radiation stability of the pre-irradiated copolymer is due to its lower crystallinity caused by the formation of branches during the pre-irradiation process.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1995.052270111
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  • 168
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    Mitteilungen/Announcements (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 227 (1995), S. 193-193 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052270117
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    Poly(diaryl diazosulfide)s  -  synthesis and photolysisThis topic is part of the Ph.D.-Thesis of A. Lang.. Photopolymers, diazosulfides, interfacial polycondensation, photolysis (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 228 (1995), S. 73-92 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Polydiaryldiazosulfide wurden durch Grenzflächenpolykondensation aus aromatischen Bisdiazoniumionen und Benzol-1,3-dithiol erhalten. Auf diese Weise wurden Molekulargewichte Mn von 3400 bis 11700 erreicht (GPC).Die neue Polymerklasse zeichnet sich durch hohe Photolabilität und relativ geringe Thermostabilität aus. Mittels UV-Spektroskopie wurde die Photolyse von Modellver-bindungen und Polymeren verfolgt, wobei in nahezu allen Fällen ein Zerfall 1. Ordnung beobachtet wurde. Der photochemische Kettenabbau konnte durch GPC-Untersuchungen verfolgt werden. Die thermische Stabilität der polymeren Diazosulfide wurde durch DSC-Messungen untersucht.
    Notes: Poly(diaryl diazosulfide)s were synthesized from aromatic bisdiazonium ions and benzene-1,3-dithiol via interfacial polycondensation. Number-average molecular weights Mn in the range of 3400 to 11700 were determined by gel permeation chromatography (GPC).The new polymer class is distinguished by high photosensitivity and low thermostability. First order kinetics during photolysis of nearly all polymers and model compounds under investigation was observed by means of UV spectroscopy. Polymer degradation upon irradiation was verified by GPC measurements. Thermal decay was followed by differential scanning calorimetry (DSC).
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1995.052280107
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    Methoden zur bestimmung des maleinsäureanhydridgehaltes in acrylnitril-copolymeren in gegenwart initialer carboxygruppen (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 228 (1995), S. 161-178 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Three different titration methods were proved with respect to accuracy, reproducibility and handling for the determination of maleic anhydride (MSA) content in acrylonitrile (AN) copolymers in form of poly(AN-co-MSA) and poly(AN-co-styrene-co-MSA). The comparison comprises (i) the combined method A/H characterized by the reaction of anhydride groups (AG) with aniline and titration of the formed monoacid with methanolic KOH (A) and the complete hydrolysis of AG and titration of acid groups (SG) with aqueous NaOH (H), (ii) method B based on the conversion of AG with n-butylamine (BA) and back-titration of unreacted amine with HClO4 in glacial acetic acid and (iii) method C consisting of the reaction of AG with p-chloroaniline (pCA) followed by Cl-determination after the Schöniger-decomposition. Whereas all mentioned methods are suitable for the determination of AG in the presence of initial SG, the combination of A/H additionally allows the simultaneous determination of AG and SG. In comparison with the other methods the combination of A/H is to be favoured due to the possibility to obtain additional information about SG and because of the better results in accuracy, reproducibility and handling. By means of FTIR spectroscopy the content of AG and SG was estimated qualitatively and a correlation between the spectroscopic and potentiometric data of AG was discovered.
    Notes: Zur Bestimmung des Maleinsäreanhydrid(MSA)-Gehaltes in Acrylnitril(AN)-Copolymeren des Typs Poly(AN-co-MSA) bzw. Poly(AN-co-Styrol-co-MSA) wurden drei verschiedene Titrationsmethoden hinsichtlich ihrer Richtigkeit, Reproduzierbarkeit sowie ihres Zeitaufwandes geprüft. Miteinander verglichen wurden (i) eine Methodenkombination A/H bestehend aus dem Teilschritt A, einer Umsetzung der Anhydridgruppen (AG) mit Anilin einschließlich der Titration der Monosäuregruppen mit methanolischer KOH, und dem Teilschritt H, einer vollständigen Hydrolyse der AG und Titration der Säuregruppen (SG) mit wäßriger NaOH, (ii) Methode B basierend auf der Reaktion der AG mit n-Butylamin (BA) und der Rücktitration des nicht umgesetzten Amins mit Perchlorsäure (HClO4) in Eisessig und (iii) Methode C, beruhend auf der Umsetzung der AG mit p-Chloranilin (pCA) und nachfolgender Chlorbestimmung durch Schöniger-Aufschluß. Während sich alle genannten Methoden prinzipiell für die AG-Bestimmung in Gegenwart initialer SG empfehlen, ist darüber hinaus über A/H eine simultane Bestimmung von AG und SG möglich. Wegen dieses zusätzlichen Informationsgewinns, ihrer besseren Reproduzierbarkeit, der erhöhten Richtigkeit sowie des geringeren zeitlichen und apparativen Aufwandes ist die Kombination A/H zu favorisieren. Mit Hilfe der FTIR-Spektroskopie wurde der Gehalt an AG und SG qualitativ verfolgt und eine Korrelation zwischen den Bandenintensitäten der AG und den potentiometrisch erhaltenen Werten gefunden.
    Additional Material: 6 Ill.
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    Curing of unsaturated polyester resins with low exotherm peak (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 229 (1995), S. 15-27 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Härtung eines ungesättigten Polyesterharzes mit niedrigem Exotherm-Peak wurde mit der Standardmethodik und der Differential-Kalorimetrie (DSC) untersucht. Ein Kupfersalz und α-Methylstyrol wurden als Polymerisationsverzögerer benutzt. Der Einfluß der Verzögerer auf die Temperatur des exothermen Peaks, die Gelzeit, die Härtungsenthalpie und die Polymerisationskinetik wurden untersucht.
    Notes: The curing behavior of an unsaturated polyester resin with low exotherm peak was studied by a standard procedure and by differential scanning calorimetry (DSC). A copper salt and α-methylstyrene were used as the polymerization retarders. The influence of the retarders on the exotherm peak temperature, gelation time, exothermic heat and the polymerization kinetics was investigated.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1995.052290102
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    Modified syndiotactic polypropene: Poly(propene-co-octene) and blends with atactic oligopropene (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 229 (1995), S. 93-112 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Propen und 1-Octen wurden mit dem syndiospezifischen Metallocen-Katalysator Me2C(Cp)(Flu)ZrCl2/MAO copolymerisiert. Es wurde ein hoher, statistischer Octeneinbau beobachtet. Niedrige Octenkonzentrationen beeinflußten die Aktivität des Katalysators nur wenig; Molekulargewicht, Kristallinität, E-Modul und Glastemperatur wurden dagegen mit ansteigendem Octengehalt erniedrigt. Blends aus ataktischem Oligopropen und syndiotaktischem Polypropen bzw. Poly(propen-co-octen) wurden aus einer Toluol-Lösung hergestellt. Diese Lösungsblends wurden mit einem Reaktorblend verglichen, der mit einem Hybrid-Katalysator bestehend aus einer Mischung von syndiospezifischem Me2C(Cp)(Flu)ZrCl2/MAO und unspezifischem Cp2ZrCl2/MAO hergestellt wurde. Das ataktische Oligopropen wirkte als Weichmacher, der E-Modul und Glastemperatur der Blends erniedrigte.
    Notes: Propene and 1-octene were copolymerized with the syndiospecific homogeneous metallocene catalyst Me2C(Cp)(Flu)ZrCl2/MAO. Large amounts of octene were incorporated randomly. While catalyst activity was not affected markedly by low octene content, molecular weight, crystallinity, Young's modulus, and glass transition temperature were reduced with increasing octene content. Blends of atactic oligopropene with syndiotactic polypropene and poly(propene-co-octene) were prepared from toluene solution and compared with a reactor blend prepared with a hybrid catalyst containing a mixture of syndiospecific Me2C(Cp)(Flu)ZrCl2/MAO and non-specific Cp2ZrCl2/MAO. Atactic oligopropene acted as plasticizer reducing Young's modulus and glass transition temperature of the blends.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052290106
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    Inner surface and void system of regenerated cellulose fibers (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 229 (1995), S. 175-184 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die innere Oberfläche und das Hohlraumsystem von verschiedenartigen Celluloseregeneratfasern werden mit Röntgenkleinwinkelstreuung untersucht. Dabei wird gefunden, daß alle Fasern ein Hohlraumsystem von 0,01 bis 0,1% (Volumenanteil 10-4-10-3) aufweisen. Es zeigt sich jedoch, daß die Größe des Hohlraumsystems für die mechanischen Eigenschaften wenig Bedeutung hat. Es ist vielmehr die Gestalt der Hohlräume und ihre Orientierung, die hier wesentlich sind. Es wird gefunden, daß langgestreckte Hohlräume, vermutlich orientiert, für gute mechanische Eigenschaften verantwortlich sind. Damit können auch verbesserte textile Eigenschaften von Lyocellfasern des NMMO-Typs erklärt werden.
    Notes: Both the inner surface and the void system of different cellulose regenerate fibers are investigated with X-ray small angle scattering. Thereby it turns out that all fibers have a void system of 0.01 to 0.1% (volume fraction 10-4-10-3). However, the amount of the void system has little influence on the mechanical properties. Rather, it is the shape of the voids and their orientation which proves essential. It is found that elongated voids, probably well oriented, are responsible for superior mechanical properties. This explains also improved textile properties of lyocell fibers of the NMMO type.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052290112
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    Radiation-induced copolymerization of methacrylic and acrylic acid with acrylamide (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 230 (1995), S. 1-12 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die mit γ-Strahlen induzierte Polymerisation von Methacrylsäure (MA) und Acrylsäure (AA) mit Acrylamid (AAm) (M2) in Substanz wurde untersucht. Die nach Kelen-Tüdős berechneten Copolymerisationsparameter betragen r1 = 1.35 und r2 = 0.22 für MA-AAm bzw. r1 = 1.75 und r2 = 0.10 für AA-AAm. Die Polymerisationsgeschwindigkeit hängt sowohl von der Temperatur als auch von der Comonomerzusammensetzung ab. Die differentialkinetischen Kurven sind unimodal, was darauf hinweist, daß nur der Copolymerisationsprozeß abläuft. Ein zweites Maximum in diesen Kurven wird mit Vernetzung und der Bildung wasserunlöslicher Bestandteile erklärt. Die Copolymeren sind weiße Pulver; die wasserlöslichen Fraktionen sind im Gegensatz zu den wasserunlöslichen nicht giftig, aber als Immunmodulatoren weniger aktiv.
    Notes: A study was made of the γ-radiation-induced bulk copolymerization of the methacrylic acid-acrylamide (M2) (MA-AAm) and acrylic acid-acrylamide (M2) (AA-AAm) monomeric pairs. The copolymerization reactivity ratios deterined according to the Kelen-Tüdő method were: r1 = 1.35, r2 = 0.22 for the MA-AAm pair, and r1 = 1.75, r2 = 0.10 for the AA-AAm pair. It has been established that the polymerization rate depends both on the composition of the starting reaction mixture and on the reaction temperature. The differential kinetic curves obtained are unimodal ones, suggesting the occurrence of only one process, i.e. copolymerization. A second maximum in these curves, appearing at elevated temperature, is explained by crosslinking and formation of a water-insoluble fraction. The copolymers obtained are white powders; in contrast to their water-insoluble fractions, the water-soluble ones are not toxic but they are less active as immunomodulators.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052300101
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    Synthesis and hydrolytic stability of model poly(ester urethane ureas) (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 228 (1995), S. 201-219 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Hydrolyse von Poly(ester-urethan-harnstoffen) (PURUs) wurde untersucht. Es handelt sich dabei um einen komplexen Vorgang, der die Analyse der Beziehung zwischen der Zusammensetzung der PURUs und ihrer Hydrolysebeständigkeit erschwert. Es wurde gefunden, daß die Hydrolysebeständigkeit mit Zunahme (i) der Polyol-Acidität, (ii) des Estergruppen-Gehaltes, (iii) der Beweglichkeit der Hauptketten und (iv) deren Hydrophilie abnimmt; die Molmasse des Polyols scheint keinen merklichen Einfluß darauf zu haben. Der negative Einfluß von Ethergruppen (obwohl hydrolysebeständiger als Estergruppen) ist möglicherweise auf eine Zunahme der Hauptkettenbeweglichkeit und den dadurch leichteren Zugang von Wassermolekülen zu Estergruppen zurückzuführen. Der positive Effekt von aromatischen Ringen in Polyolen kann einer erhöhten Steifigkeit der Hauptkette als auch einer ansteigenden Hydrolysebeständig-keit benachbarter Estergruppen durch Resonanzeffekte zugeschrieben werden. Insgesamt kann angenommen werden, daß die beschriebenen Effekte sich überlagern und gleichzeitig die resultierende Hydrolysebeständigkeit vorherbestimmen. Es sollte daher möglich sein, qualitative Vorhersagen bezüglich der Hydrolysebeständigkeit in Abhängigkeit von der Zusammensetzung der PURUs zu treffen.
    Notes: Hydrolysis of poly(ester urethane ureas) (PURUs) is a complex phenomenon which impedes the analysis of the relationships between their composition and hydrolytic stability. Hydrolytic stability of PURUs decreases due to rising (i) polyol acidity, (ii) content of ester groups, (iii) flexibility and (iv) hydrophilicity of the backbones; molar mass of polyols does not seem to have any appreciable effect on it. Negative influence of ether groups (which have better hydrolytic stability than ester groups) is probably linked to the increase in the backbone flexibility and, consequently, to easier access of water molecules to ester groups. Positive effect of aromatic rings in polyols can be ascribed to enhanced rigidity of the backbones as well as to increased hydrolytic stability of adjacent ester groups due to the resonance effect. It can be presumed that the mentioned effects will superpose and simultaneously predestine the resulting hydrolytic resistance. Considering the observed tendencies, it is possible to qualitatively predict the trends how the hydrolytic stability will respond to changes in PURUs composition.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052280116
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  • 176
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    Synthesis and characterization of a naphthoquinonediazide positive photoresist derived from bis(hydroxymethyl)phenol (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 229 (1995), S. 63-72 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Eine neuartige lichtempfindliche Naphthochinondiazid-Verbindung (NQD) wurde aus 2,6-Bis(hydroxymethyl)-3,4-dimethylphenol und Toluoldiisocyanat synthetisiert und mit IR-, NMR- und Elementaranalyse identifiziert. Die Bleicheigenschaften unter Lichteinwirkung wurden mit UV-Spektrophotometrie bestimmt. Die Anwendung von NQD in der Photolithographie als positiver Photoresist sowie einer wäßrigen Lösung von NQD, Novolak, Cellosolve-Acetat und DMF als lichtempfindliches Material wurde untersucht. Das hergestellte NQD erwies sich als effektive Komponente in positiven Photoresists. Die optimalen Bedingungen der UV-Dosis, Schichtdicke und Resistzusammensetzung wurden abgeschätzt. Die Auflösung des positiven Photoresists wurde durch Rasterelektronenmikroskopie bestimmt. Außerdem wurde der Einfluß von UV-Dosis und -Wellenlänge, Einwirkungsdauer und Entwicklungszeit auf die Empfindlichkeit und die Auflösung des Photoresists untersucht.
    Notes: A new photosensitive naphthoquinonediazide (NQD) was synthesized from 2,6-bis-(hydroxymethyl)-3,4-dimethylphenol and toluene diisocyante. NQD was identified by using IR, NMR and elemental analyses. Photobleachable characteristics were evaluated by UV spectrophotometry. Applications of the NQD on the photolithography as a positive working photoresist were investigated. The aqueous solution of NQD, novolak, cellosolve acetate, and DMF was used as a photosensitive material. It was found that NQD synthesized in this investigation can be used as an effective component in a positive photoresist. Optimal conditions of the UV dose, coating thickness, and development of the resist system were estimated. Resolution of the positive resist was evaluated by SEM technique. Effects of UV dose, exposure time, development time, and exposure UV wave length on the sensitivity and resolution of the photoresist were investigated.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052290104
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    Investigations on free radical polymerization of phenyl-substituted 2-methylene-1,3-dioxanes (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 229 (1995), S. 123-132 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die radikalinduzierte Polymerisation von phenlysubstituierten 2-Methylen-1,3-dioxanen wurde untersucht. Es kann gezeigt werden, daß die grundlegende Polymerisationstendenz derartiger Ketenacetale darin besteht, über die Doppelbindung zu hochmolekularen Polyacetalen ohne eine nennenswerte Ringöffnung zu polymerisieren. Einflußfaktoren, wie z. B. resonanzstabilisierte Kettenenden oder sterische Hinderungen während des Wachstumsschrittes sind nicht in der Lage, die Polymerisation in die Richtung der gewünschten Ringöffnung zu lenken.Mittels Dichtemessungen wurden Informationen über das Schrumpfungsverhalten gewonnen. Es konnte gezeigt werden, daß raumerfüllende Substituenten am 2-Methylen-1,3-dioxansystem bei der Homopolymerisation grundsätzlich eine geringe Volumenschrumpfung bewirken und die Schrumpfung von herkömmlichen Monomeren bei der Copolymerisation herabsetzen können.
    Notes: We have investigated the free radical polymerization of phenyl-substituted 2-methylene-1,3-dioxanes. It was shown that there is a basic tendency of such ketenacetals to undergo exclusively a vinyl polymerization forming high-molecular polyacetals without any detectable ring opening. The polymerization with the desirable ring opening reaction cannot be controlled by factors like resonance stabilized chain ends or steric hindrance in the growing step.From densitometric measurements we got new information about the shrinkage behaviour. It was demonstrated that bulky substituents attached to the 2-methylene-1,3-dioxane system result in a significant low shrinkage in homopolymerization and the shrinkage of common comonomers can be decreased by copolymerization.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1995.052290108
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  • 178
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    Acrylamide polymerization in concentrated bicontinuous systems (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 229 (1995), S. 133-143 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Polymerisation von Acrylamid (AAM) in einer konzentrierten bikontinuierlichen Mikroemulsion wurde studiert. Die Initiierungsstelle bei Verwendung von radikalischen Initiatoren mit verschiedener Wasserlöslichkeit wurde untersucht. Es wurde festgestellt, daß ein vollständig oder teilweise wasserlöslicher radikalischer Initiator die Acrylamidpolymerisation in der untersuchten Mikroemulsion effektiv initiieren kann. Die dadurch entstandenen Polymeren weisen eine Spezialstruktur auf, die von der Zusammensetzung der ursprünglichen Mikroemulsion abhängig ist.
    Notes: The polymerization of acrylamide (AAM) in concentrated bicontinuous microemulsion systems was studied. The locus of initiation using radical initiators with various water-solubility was investigated. It was found that water-soluble and partially water-soluble initiators initiate the AAM polymerization in the reaction systems under investigation very effectively. The polymers thus formed have special structures dependent on the composition of the original concentrated bicontinuous microemulsion.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052290109
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    Mitteilungen/announcements (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 229 (1995), S. 209-209 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052290115
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  • 180
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    Orientierung von Bacteriorhodopsin in einer Polymermatrix (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 229 (1995), S. 185-198 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Bacteriorhodopsin is a component of the purple membrane of Halobacterium halobium. It shows photochemical activity and undergoes a series of photocyclic-associated conformational changes. Incorporated in a matrix it is suitable as a light energy/electrical current transducer. Very important is an orientation of purple membrane fragments.The reaction between solutions of a polyelectrolyte and multivalent ions leads to a ionotropic gel, that is a gel with an ordered structure. If the gel formation was carried out in the presence of purple membrane fragments, the Bacteriorhodopsin is highly oriented and produces a photoelectrical signal. It consists a correlation between the light direction and the orientation of the purple membrane due to the gel formation.
    Notes: Bacteriorhodopsin ist Bestandteil der sogenannten Purpurmembran des Mikroorganismus Halobacterium halobium. Es zeigt photochemische Aktivität und kann als biologischer Lichtwandler fungieren. Voraussetzung hierfür ist eine orientierte Anordnung der Purpurmembran in einer Matrix.Das Prinzip der ionotropen Gelbildung, d. h. die geordnete Strukturbildung einer Polyelektrolytlösung infolge eines gerichteten Diffusionsstromes von mehrwertigen Ionen gestattet die orientierte Anordnung der Purpurmembran. Durch Lichteinwirkung werden elektrische Signale induziert. Es besteht ein Zusammenhang zwischen der Richtung des Strahlungseinfalls und der durch die Gelwachstumsrichtung festgelegten Orientierung der Purpurmembran.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1995.052290113
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  • 181
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    Stabilizer consumption and lifetime prediction in ageing of crosslinked polyethylenePaper presented at the “16th International Conference on Advances in the Stabilization and Degradation of Polymers” in Luzern (Switzerland), June 14-17, 1994. (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 232 (1995), S. 1-12 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The thermal oxidation of β ray-crosslinked polyethylene (XLPE) was studied in temperatures ranging from 90 to 180°C. Various analytical methods were used for determination of an end of the induction period on bulk samples: gravimetry, ultimate tensile properties, density and color change. On microtome slices of ∼30 μm thickness the depth distribution of oxidation products, phenolic antioxidant, density and tensile ultimate properties were followed as a function of exposure time by respectively IR and UV spectrophotometry, densitometry and Microfoil Tensile Testing.Depending on the testing method different durations of induction period (DIP) were obtained. They increase in following order:Phenol depletion 〈 Ultimate elongation 〈 Density 〈 Carbonyl build-up ≤ Color change 〈 Weight loss.The difference between phenol depletion DIP and carbonyl build-up DIP can be considered as negligible at temperatures higher than the melting point (about 30%) but it reachs more than 100% at T〈 Tm.Different kinetic regimes of phenol consumption were observed depending on the exposure temperature. A mechanistic interpretation is proposed explaining the role of the stabilizer system in initially homogeneous and later heterogeneous oxidation of the bulk material.The Arrhenius law was applied to different durations of induction period. A discontinuity appeared in the melting point region (120-130°C) which is tentatively interpreted in terms of different stabilizer concentration in amorphous phase of semicrystalline material (T 〈 Tm) and in melt material (T 〉 Tm). On the basis of the presented complex study of polyethylene thermo-oxidation, different aspects of lifetime predictions are discussed.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052320101
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  • 182
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    Pyrolysis with respect to recycling of polymerPaper presented at the “16th International Conference on Advances in the Stabilization and Degradation of Polymers” in Luzern (Switzerland), June 14-17, 1994. (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 232 (1995), S. 151-165 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Most plastics are produced from oil and have a high potential as hydrocarbon sources for the chemical industry. Pyrolysis is a practicable way to pyrolyze mixed plastics. The fluidized bed pyrolysis has turned out to be particularly advantageous. 25 to 45 percent of product gas with a high heating value and 30 to 50 percent of an oil rich in aromatics, could be recovered. The oil is comparable to that of a mixture of light benzene and bituminous coal tar. Up to 60 percent of ethene and propene are produced by using mixed polyolefins as feedstock. Under appropriate conditions the pyrolysis could be successful on the market.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1995.052320110
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    Photodegradation of UV absorbers: Kinetics and structural effectsPaper presented at the “16th International Conference on Advances in the Stabilization and Degradation of Polymers” in Luzern (Switzerland), June 14-17, 1994. (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 232 (1995), S. 229-238 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: When poly(methyl methacrylate) films containing UV absorbers are exposed to UV light, the absorbers undergo photodegradation resulting in loss of absorbance. If the data extend for less than one half-life, both zero and first order kinetic treatment give fairly linear fits, but the rate constants so derived are dependent on the initial absorbance of the films. When the zero order rate constants are corrected to account for the higher rate of degradation near the surface compared with the bulk that occurs in highly absorbing films, consistent “infinite absorption” zero order rate constants are derived. The inhomogeneous degradation is due to only the highly absorbed, higher energy light contributing significantly to the degradation. For the benzophenone and benzotriazole classes of absorber, at least 65% of the degradation is due to light with wavelengths 〈 350 nm. Structural variations generally caused only small differences in the rates of degradation of these classes of absorbers unless the substitutions disrupted the intramolecular hydrogen bonds that are critical for stability. If the hydrogen bond is weakened, the absorber is less stable.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1995.052320114
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    Polymers from renewable resources, VI. Synthesis and characterization of thermosetting resins derived from cashewnut shell liquid/formaldehyde/substituted aromatic compounds (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 233 (1995), S. 1-13 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Aus Cardanol, einem Bestandteil der Schale der Cashewnuß, wurde durch Kondensation mit Formaldehyd und substituierten aromatischen Verbindungen unter saurer oder basischer Katalyse eine Reihe von Harzen hergestellt und anhand ihrer IR-Spektren charakterisiert. Sie lassen sich als selektive Ionenaustauscher für bestimmte Ionen verwenden, was mittels einer Gleichgewichtsmethode geprüft wurde. Das thermische Verhalten der Harze wurde untersucht, und ein plausibler Abbaumechanismus wird vorgeschlagen.
    Notes: A large number of resins have been synthesized by reacting cardanol, a constituent of cashewnut shell liquid, with formaldehyde and substituted aromatic compounds in the presence of acidic and basic catalysts. The resins have been characterized by IR spectra. They were shown to be selective ion exchangers for certain metal ions. A batch equilibrium method was used for studying the selectivity of the metal ions. The thermal behaviour of the resins has been studied and a plausible degradation mechanism has been suggested.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052330101
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    Search for the sources of color in thermally aged, weathered and γ-ray irradiated bisphenol a polycarbonatePaper presented at the “16th International Conference on Advances in the Stabilization and Degradation of Polymers” in Luzern (Switzerland), June 14-17, 1994. (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 232 (1995), S. 27-43 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Bisphenol A polycarbonate (BPA-PC) is an important high performance engineering thermoplastic well known for its outstanding combination of toughness, transparency and heat resistance. These properties make it an idel material for demanding applications where it is exposed to external stresses such as elevated temperatures, ultraviolet light and γ-ray sterilization. However, on extended exposure to these conditions, BPA-PC slowly degrades, turning progressively more yellow, eventually leading to a decrease in its physical properties. Over the years, there has been numerous studies made to understand these degradative processes so as to better design more stable BPA-PC formulations. In this paper, this chemistry is briefly reviewed along with more recent work in this area with a special emphasis on the efforts made to identifying the actual chemical species responsible for the observed yellow color and the chemistry responsible for their formation.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1995.052320103
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    Model studies on the mechanism of hals stabilizationPaper presented at the “16th International Conference on Advances in the Stabilization and Degradation of Polymers” in Luzern (Switzerland), June 14-17, 1994. (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 232 (1995), S. 65-83 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Hindered Amine Light Stabilizers (HALS) are know to inhibit the photo-oxidation of polymers. A key reaction in their stabilization mechanism is believed to be the conversion of a hindered aminoether into a nitroxyl radical. Several different possible mechanisms for this conversion were explored. One, the elimination of the aminoether to form an olefin and hydroxylamine (an intermediate in the formation of a nitroxyl), while possible at high temperatures, cannot account for the inhibitory activity we observed for secondary and primary aminoethers. Direct radical displacement by peroxy radicals was also considered. However, the products predicted by this reaction pathway were not observed. Finally, oxidation of the nitrogen by a peroxy radical, by either electron transfer or a radical attack on the nitrogen, was investigated. While electron transfer was shown to be unlikely, direct oxidation of the aminoether nitrogen was supported by our results. A detailed mechanism for the reaction of both alkyl- and acyl-peroxy radicals with aminoethers is proposed.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1995.052320105
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    Physical, dynamic-mechanical and thermogravimetric analysis of aromatic and cycloaliphatic-based poly(urethaneurea)s (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 231 (1995), S. 79-89 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die thermischen und dynamisch-mechanischen Eigenschaften einiger linearer kautschukelastischer Polyurethane mit chemisch unterschiedlichen starren Segmenten wurden untersucht und zur chemischen Zusammensetzung in Beziehung gesetzt. Interessante Zusammenhänge wurden zwischen der Kristallinität der elastischen Polyurethanharnstoffe und der aromatischen oder cycloaliphatischen Natur der Diisocyanat-Komponenten gefunden. Darüber hinaus scheinen die Ergebnisse bei einem bestimmten Verhältnis zwischen starren und flexiblen Segmenten und bei gegebener Zusammensetzung der flexiblen Gruppen auf eine bessere Phasenseparation bei den Polyurethanharnstoffen mit cycloaliphatischen starren Segmenten als bei solchen mit aromatischen, starren Einheiten hinzuweisen.
    Notes: Experimental batches of linear rubber-like polyurethanes characterized by the presence of chemically different hard segments are studied and their thermal and dynamic-mechanical properties are related to the differences in chemical compositions. Interesting correlations are found between the development of crystallinity in such elastomeric poly(urethaneurea)s and the aromatic or alicyclic nature of the diisocyanate. Moreover, for a fixed ratio between hard and soft segments, and for a given composition of the soft segment, the results seem to indicate a better degree of phase separation in cycloaliphatic-based hard segment poly(urethaneurea)s than in aromatic-based hard segment poly(urethaneurea)s.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1995.052310108
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    Dispersion polymerization of styrene and methyl methacrylate initiated by poly(oxyethylene) macromonomeric azoinitiators (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 231 (1995), S. 135-144 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Makromonomere Polyethylenoxid-Azoinitiatoren (Makroinimere) MIM-400 und MIM-1500 wurden synthetisiert und IR- und NMR-spektroskopisch sowie mit Hilfe der DSC-Analyse charakterisiert. Die mit diesen Makroinimeren initiierte Dispersions-polymerisation von Styrol bzw. Methylmethacrylat (MMA) in Ethanol/Wasser bei 60°C wurde untersucht. Dabei wurde gefunden, daß die Polymerisationsgeschwindig-keit mit zunehmender MIM-Konzentration ansteigt, wobei der Anstieg im Styrolsystem ausgeprägter war. Im Bereich von mittleren Umsätzen konnte gezeigt werden, daß die Polymerisationsgeschwindigkeit von MMA proportional der Potenz 1,7 bzw. 1,6 von [MIM-400] bzw. [MIM-1500] ist, während für Styrol eine Potenz von 2,5 bezüglich [MIM-400] gefunden wurde.
    Notes: Macromonomeric poly(oxyethylene) azoinitiators (macroinimers) MIM-400 and MIM-1500 were synthesized and characterized by IR and NMR spectroscopy and DSC techniques. The dispersion polymerizations of styrene and methyl methacrylate (MMA) initiated by poly(oxyethylene) macroinimers (MIM-400 and MIM-1500) in water/ethanol were investigated at 60°C. The rate of polymerization was found to increase with increasing concentration of MIM and the increase was more pronounced in the styrene system. In the range of medium conversions the rate of polymerization was found to be proportional to the 1.7th and 1.6th power of [MIM-400] and [MIM-1500] for MMA and to the 2.5th power of [MIM-400] for styrene, respectively.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1995.052310112
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    Modell zur beschreibung der glasübergangstemperaturen binärer und ternärer mischungen von poly(styrol-co-n-butylmethacrylat)en (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 231 (1995), S. 187-198 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Glass transition temperatures of binary and ternary blends of chemically uniform poly(styrene-co-n-butyl methacrylate)s with a mean content of 30.8 wt.-% of n-butyl methacrylate and number-average molar masses in the range of 4900 and 67000 g/mol have been investigated in relation to their composition. The blends showed significant deviations from an ideal behaviour with reference to a linearity between glass transition temperature and composition.This phenomenon is described by a mathematical model where polynoms are particularly well suited to represent the glass transition temperatures of the blends, partly exceeding those of the pure components. Finally, various reasons of these deviations were discussed. Here, energetical interactions seem to be of considerable importance combined with a nonadditivity of volumes.
    Notes: Die Glasübergangstemperaturen binärer und ternärer Mischungen chemisch einheitlicher Poly(styrol-co-n-butylmethacrylat)e mit einem mittleren n-Butylmethacrylat-Anteil von 30,8 Gew.-% und unterschiedlichen zahlenmittleren Molmassen im Bereich von 4900 bis 67000 g/mol wurden in Abhängigkeit von der Zusammensetzung untersucht. Es wurden wesentliche Abweichungen vom idealen Verhalten bezüglich einer linearen Abhängigkeit zwischen Glasübergangstemperatur und Zusammensetzung festgestellt.Dieses Verhalten konnte mit einem mathematischen Modell dargestellt werden, wobei sich insbesondere Polynome zur Beschreibung der teilweise über den Werten der Ausgangskomponenten liegenden Glasübergangstemperaturen der Mischungen als geeignet erwiesen. Schließlich wurden verschiedene Ursachen für diese Abweichungen diskutiert, wobei offensichtlich energetische Wechselwirkungen verbunden mit einer Nichtadditivität der Volumina von wesentlicher Bedeutung sind.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1995.052310116
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    Zur bildung von polyepoxid-polyamid-netzwerken. Modelluntersuchungen am system phenylglycidether-ε-caprolactam (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 233 (1995), S. 133-148 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: ε-Caprolactam (CL) and phenyl glycidyl ether (PGE) were homopolymerized using the initiator/accelerator-systems Na-caprolactam/N-acetyl-caprolactam (NaCL/AcCL) and Na-caprolactam/N-acetyl imidazole (NaCL/AcImi). In a one-pot reaction both monomers gave different oligomeric reaction products depending on the reaction temperature (100°C to 140°C, max. 240°C) but no regular copolymers. Soluble products were separated by HPLC and identified by means of spectroscopic methods. In acetone insoluble products were investigated by IR- and NMR-spectroscopy, mass spectrometry and elemental analysis.
    Notes: Es wurden Versuche zur Homopolymerisation von ε-Caprolactam (CL) und Phenylglycidether (PGE) mit den Initiator/Beschleuniger-Systemen Na-Caprolactam/N-Acetylcaprolactam (NaCL/AcCL) und Na-Caprolactam/N-Acetylimidazol (NaCL/AcImi) durchgeführt, um die für eine mögliche Copolymerisation von CL und PGE geeigneten Reaktionsbedingungen zu ermitteln. CL und PGE wurden in unterschiedlichen molaren Verhältnissen (CL : PGE = 1 : 5 bis 1 : 0,05) und bei Temperaturen zwischen 100°C und 140°C (max. 240°C) in einer Eintopfreaktion polymerisiert.Die löslichen Produkte wurden mittels HPLC getrennt und spektroskopisch identifiziert. Die in Aceton unlöslichen Produkte wurden mit IR- und NMR-Spektroskopie, Massenspektrometrie (MS) und Elementaranalyse untersucht.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052330112
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  • 191
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    Synthesis and characterization of copolymers from acrylic and methacrylic acid with 2-methylaziridine by spontaneous copolymerization (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 231 (1995), S. 199-211 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: 2-Methylaziridin (MAz) wurde als nukleophiles Monomeres mit den elektrophilen Monomeren Acrylsäure (AA) bzw. Methacrylsäure (MA) in unterschiedlichen Verhältnissen ohne Initiator copolymerisiert. Die Copolymeren wurden mittels Elementaranalyse, FT-IR- und 1H-NMR-Spektroskopie charakterisiert. Die Copolymerisationsparameter wurden mit den Methoden nach Fineman-Ross bzw. Kelen-Tüdős bestimmt. Für r1 und r2 wurden die Copolymerpaare MAz-AA und MAz-MA jeweils Werte 〈 1 ermittelt, was auf statistische Copolymere mit einer Tendenz zu alternierenden Copolymeren hinweist. Thermische Zersetzung mit einem Gewichtsverlust von 10% tritt bei den Copolymeren erst oberhalb 430 K auf. Der thermische Abbau verläuft nach einer Reaktion nullter Ordnung. Die kinetischen Parameter der Zersetzung der Copolymeren wurden bestimmt.
    Notes: 2-Methylaziridine (MAz) as a nucleophilic monomer and acrylic acid (AA) and methacrylic acid (MA), respectively, as electrophilic monomers were copolymerized in the absence of initiator at various feed ratios. Copolymers were characterized by elemental analysis, FT-IR and 1H-NMR spectroscopy. The monomer reactivity ratios were determined by the Fineman-Ross and Kelen-Tüdős methods. Values of r1 and r2 were found to be less than unity for MAz-AA, and MAz-MA, corresponding to random copolymers with the tendency to the alternance. For all the copolymers the thermal decomposition with 10% weight loss is higher than 430 K. The reaction order for degradation of all copolymers was zero. The kinetic parameters of the decomposition were determined for all copolymers.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1995.052310117
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    New trends in epr and epr kinetics studies in the stabilization mechanism by N-oxyl radicalsPaper presented at the “16th International Conference on Advances in the Stabilization and Degradation of Polymers” in Luzern (Switzerland), June 14-17, 1994. (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 232 (1995), S. 45-63 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The mechanism of the solid state oxidation of isotactic polypropylene films and the the mechanism of inhibition by HALS have been investigated by kinetic-ESR and kinetic modelling with derivation of the rate constants for the sensitive steps in the reaction scheme. The results have shown the inadequacy of the Denisov cycle to account for the observed experimental kinetics of the intermediate nitroxyl radicals. The molecular dynamics associated with the oxidation inhibited by HALS in the polypropylene matrix has been investigated by applying the Liouville stochastic method to the analysis of the temperature effects of the ESR spectra of the intermediate nitroxyl radicals used as spin probes. The investigation on the nature and characteristics of the molecular motions available at the oxidation sites has also been carried out with nitroxyl spin labels bound to the PP chains. For this application a novel method of spin labelling was developed based on reactions with some of the oxidation products, namely the terminal and intrachain ketones (keana method), alcohols, peroxides and macroalkyl radicals.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1995.052320104
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    Aspects of stabilization with phosphorous antioxidants in polymersPaper presented at the “16th International Conference on Advances in the Stabilization and Degradation of Polymers” in Luzern (Switzerland). June 14-17, 1994. (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 232 (1995), S. 119-131 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: As plastics are being used in a variety of applications, demands on a greater level of processing stability are increasing. Phosphites are noteworthy as effective processing stabilizer and the performance of phosphite antioxidants can be correlated to the chemical structure of phosphites. Cyclic phosphite esters derived from 2, 2′ methylene bis-2, 4-di-tert-butylphenol and some commercially available phosphites were submitted to comparative studies. Decomposition of cumene hydroperoxide, melt flow of polypropylene and consumption of additives after multiple extrusions were investigated to understand the activity of phosphites as process stabilizers in polypropylene.This study suggests that phosphites play an important role in process stabilization when used in combination with sterically hindered phenols, and that the activity of phosphites may be predicted by their reactivity on hydroperoxide.
    Additional Material: 13 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1995.052320108
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  • 194
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    β-Turn conformations in crystal structures of model peptides containing α,α-Di-n-propylglycine and α,α-Di-n-butylglycine (1995)
    New York : Wiley-Blackwell
    Biopolymers 35 (1995), S. 1-9 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal state conformations of three peptides containing the α,α-dialkylated residues. α,α-di-n-propylglycine (Dpg) and α,α-di-n-butylglycine (Dbg), have been established by x-ray diffraction. Boc-Ala-Dpg-Alu-OMe (I) and Boc-Ala-Dbg-Ala-OMe (III) adopt distorted type II β-turn conformations with Ala (1) and Dpg/Dbg (2) as the corner residues. In both peptides the conformational angles at the Dxg residue (I: φ = 66.2°, ψ = 19.3°; III: φ = 66.5°. ψ = 21.1°) deviate appreciably from ideal values for the i + 2 residue in a type II β-turn. In both peptides the observed (N…O) distances between the Boc CO and Ala (3) NH groups are far too long (1: 3.44 Å: III: 3.63 Å) for an intramolecular 4 → 1 hydrogen bond. Boc-Ala-Dpg-Ata-NHMe (II) crystallizes with two independent molecules in the asymmetric unit. Both molecules HA and HB adopt consecutive β-turn (type III-III in HA and type III-I in IIB) or incipient 310-helical structures, stabilized by two intramolecular 4 → 1 hydrogen bonds. In all four molecules the bond angle N-Cα-C′ (τ) at the Dxg residues are ≥ 110°. The observation of conformational angles in the helical region of φ,ψ space at these residues is consistent with theoretical predictions. © 1995 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360350102
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  • 195
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    A nonhelical, multiple β-turn conformation in a glycine-rich heptapeptide fragment of trichogin A IV containing a single central α-aminoisobutyric acid residue (1995)
    New York : Wiley-Blackwell
    Biopolymers 35 (1995), S. 21-29 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational properties of the protected seven-residue C-terminal fragment the lipopeptaibol antibiotic Trichogin A IV (Boc-Gly-Gly-Leu-Aib-Gly-Ile-Leu-OMe) has been examined in CDCl3 and (CD3)2SO by 1H-nmr. Evidence for a multiple β-turn conformation [type I′ at Gly(1)-Gly(2), type II at Leu(3)-Aib(4), and a type I′ at Aib(4)-Gly(5)] suggests that Leu(3) has preferred an extended or semiextended conformation over a helical conformation in CDCl3. This structure is thus in contrast to earlier observations of seven-residue peptides containing a single central Aib preferring helical conformations in both solution and crystalline slates. A structural transition to a frayed right-handed helix is absented in (CD3)2SO. These results suggest that nonhelical conformations may be important in Gly-rich peptides containing Aib. Further, the presence of amino acids with contradictory influences on backbone conformational freedom can lead to well-defined conformational transitions even in small peptides. © 1995 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360350104
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    A method for characterizing transition concertedness from polymer dynamics computer simulations (1995)
    New York : Wiley-Blackwell
    Biopolymers 35 (1995), S. 31-46 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A statistical method based on classifying the transitions among a set of dihedral angles within an “energy transfer window” is developed, and used to analyze Brownian (BD) and molecular dynamics (MD) simulations of the acyl chains in a lipid bilayer, and MD of neat hexadecane. It is shown for the BD simulation that when a transition of the dihedral angle in the center of the chain occurs, a transition of a particular next nearest neighbor (or angle 2-apart) will follow concertedly with a probability of approximately 0.10 within a lime window of approximately 3 ps. The MD bilayer simulations, which are based on a more flexible model of the hydrocarbon chains, yield corresponding concerted transition probabilities of approximately 0.083 and window sizes of 1-2 ps. An analysis of angles 4-apart yields concerted transition probabilities of 0.03 and 0.04 for the BD and MD bilayer simulations, respectively, and window sizes close to those of the corresponding 2-apart cases. Statistical hypothesis testing very strongly rejects the assertion that these follower transitions are occurring at random. Similar analysis reveals marginal or no evidence of concertedness between 1-apart (nearest neighbor) and between 3-apart dihedral angle transitions. The pattern of concertedness for hexadecane is qualitatively similar to that of the lipid chains, although concertedness is somewhat stronger for the 3-apart transitions and somewhat weaker for those 4-apart. Finally, it is suggested that the diffusion of small solute molecules in membranes is better facilitated by non concerted transitions, which are associated with relatively large displacements of the chains, than by concerted transitions, which do little to change the chain shape. © 1995 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360350105
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    The distribution of water in arterial elastin: Effects of mechanical stress, osmotic pressure, and temperature (1995)
    New York : Wiley-Blackwell
    Biopolymers 35 (1995), S. 161-169 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using gravimetric and radiotracer techniques, we investigated the effects of mechanical stress, osmotic pressure, and temperature on the volumes of the intra- and extrafibrillar water spaces in arterial elastin. We also investigated the effects of temperature on water flow through elastin membranes and on dynamic mechanical properties of elastin rings. Compression by mechanical or osmotic loading reduced the hydration of the elastin in an identical manner. Two distinct stages were evident; at low loads there was extensive water removal from the extrafibrillar space while high loads were required to remove water from the intrafibrillar space. Conversely, dehydration caused by mechanical extension of the matrix was associated with a much smaller loss from the extrafibrillar compartment and a large fractional decrease in the intrafibrillar space. Contraction of the matrix as a result of increased temperature had similar effects on hydration to those produced by extension. Water flux across elastin membranes, corrected for changes in viscosity, and specific hydraulic conductivity both increased as a result of temperature-induced contraction. This effect was attributed to increases in both the fractional volume of the extrafibrillar space and the fiber radius. The elastic modulus decreased with increasing temperature, but there was an increase in viscoelasticity. Previous studies have determined that viscoelasticity depends on the rate of redistribution of intrafibrillar water, so this finding provides additional evidence that heating affects primarily the volume of the intrafibrillar space. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360350204
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    Gel electrophoresis measurement of counterion condensation on DNA (1995)
    New York : Wiley-Blackwell
    Biopolymers 35 (1995), S. 211-216 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We used agarose gel electrophoresis to measure the effective charge neutralization of DNA by counterions of different structure and valence, including Na+, Mg2+, Co(NH3)63+, and sperinidine3+, which competed for binding with an excess of Tris acetate buffer. Linear DNA molecules ranged in size from 1 to 5 kilobases, and supercoiled plasmid pUC18 was also measured. In all cases, the results were in good agreement with theoretical predict ions from counterion condensation theory for two-counterion mixtures. © 1995 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360350209
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    Hydrogen exchange studies of the Arc repressor: Evidence for a monomeric folding intermediate (1995)
    New York : Wiley-Blackwell
    Biopolymers 35 (1995), S. 217-226 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The hydrogen exchange rates of the backbone amide and labile side-chain protons of the dimeric Arc repressor have been measured. For the slowly exchanging amides in the α-helical regions, these rates show a concentration dependence. To account for this dependence, the role of the monomer-dimer equilibrium was considered. Extrapolating the observed exchange rates to zero dimer concentration provides estimates of these rates in the monomer and shows that they are significantly retarded compared to those of an unfolded polypeptide. This suggests that the monomer is in a structured “molten globule” like state. In particular, the two helices of Arc retain a high degree of their secondary structure and it is proposed that the two amphiphilic helices are packed together with their hydrophobic faces. Evidence for a partially folded structure in the Arc monomer was reported earlier in two other studies [J. L. Silva, C. F. Silveira, A. Correia, Jr., and L. Pontes (1992) Journal of Molecular Biology, Vol. 223, pp. 545-555: X. Peng, J. Jonas, and J. L. Silva (1993) Proceedings of the National Academy of Science USA, Vol. 90, pp. 1776-1780]. By combining the results of these studies and ours, a folding pathway of the dimeric Arc repressor involving four different stages is proposed. Due to the low concentration of Arc repressor in the cell, the protein is present either as a free monomer or it is bound to DNA presumably as a tetramer. Therefore the folding pathway can be regarded as an integral part of the overall DNA binding process. © 1995 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360350210
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    Masthead (1995)
    New York : Wiley-Blackwell
    Biopolymers 35 (1995) 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360350301
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