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  • 1995-1999  (11,962)
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  • 2020-2023
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  • 1995-1999  (11,962)
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  • 1
    Electronic Resource
    Electronic Resource
    Effects of orally administered interferon-α on the pathogenesis of feline leukaemia virus-induced erythroid aplasia (1995)
    Springer
    Comparative clinical pathology 5 (1995), S. 79-83 
    Details
    ISSN: 1433-2981
    Keywords: Cat ; Feline leukaemia virus ; Interferon-α
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The use of orally administered interferon-α as a treatment for retroviral disease was evaluated in the experimental model of feline leukaemia virus (FeLV)-induced erythroid aplasia. Progressive anaemia, FeLV viraemia, and leukopenia developed in cats inoculated with the Kawakami-Theilen isolate of feline leukaemia virus (FeLV-KT). A treatment regimen with orally administered recombinant interferon-α or natural interferon-α as employed in this study had no significant effects on viraemia, course of disease, or differential leucocyte counts. The results of this study did not reveal any beneficial effects of human interferon-α administered by the oral route for treatment of cats with experimentally induced FeLV infection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00638923
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of decalcification on bone mineral content and bending strength of feline femur (1995)
    Springer
    Calcified tissue international 56 (1995), S. 78-82 
    Details
    ISSN: 1432-0827
    Keywords: Bone mineral content (BMC) ; Cat ; Decalcification ; Ethylene diaminetetra acetic acid (EDTA) ; Femur
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract The relationships between bone mineral content (BMC), bone calcium, and bone strength were studied in fractionally demineralized feline femurs. In 44 pairs of cat femurs, the right bones were decalcified in ethylene diaminetetra acetic acid (EDTA) to 20%, 40%, 60%, 80%, and 100% of the mineral content of the intact left bone (=control). The bones were then loaded to failure, and maximum strength values were recorded. The data were then used to calculate the percentage strength of the right relative to the left femurs. A correlation coefficient (r) of 0.970 was found between the percentage decalcification and percentage bending strength. A direct relationship (r=0.876) was also observed between the total calcium extracted and total loss in BMC. The EDTA solutions were spot checked for protein content to determine if the organic matrices had been altered by demineralization. Protein was never detected. Nor did the demineralized tissues display histologic evidence of gross microscopic damage. This study has shown that in cat femurs, 20% decalcification led to about 35% loss in bending strength, and 60% decalcification caused 75% loss in strength. These values are significant as they highlight the importance of calcium to the strength of osteopenic bone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00298748
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  • 3
    Electronic Resource
    Electronic Resource
    Different patterns of fore-hindlimb coordination during overground locomotion in cats with ventral and lateral spinal lesions (1995)
    Springer
    Experimental brain research 104 (1995), S. 70-80 
    Details
    ISSN: 1432-1106
    Keywords: Locomotion ; Spinal lesions ; Interlimb coordination ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effect of large, low thoracic (T10–T11), partial spinal lesions involving the ventral quadrants of the spinal cord and, to a different extent, the dorsolateral funiculi, on fore-hindlimb coordination was examined in cats walking overground at moderate speeds (40–100 cm/s). Three different forms of impairment of fore-hindlimb coordination depending on the extent of the lesions, were observed. Lesions sparing the dorsolateral or the ventral funiculus on one side preserved the equality of the fore- and hindlimb locomotor rhythms but changed the coupling between the movements of both girdles as compared to intact animals. Larger lesions in which, in addition to the ventral quadrants of the spinal cord, also major parts of the dorsolateral funiculi were destroyed elicited episodes of rhythm oscillations in both girdles, which appeared at the background of a small difference in these rhythms. Lesions destroying almost the whole spinal cord induced a permanent difference (about 200 ms) in the step cycle duration of the fore- and the hindlimbs. However, even in these animals some remnant form of fore-hindlimb coordination was found. The results suggest that dorsolateral funiculi play a major role in preserving the equality of rhythms in the foreand the hindlimbs, while lesions of the ventral quadrants change the coupling between limbs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00229856
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of neonatal splitting of the optic chiasm on the development of feline visual callosal connections (1995)
    Springer
    Experimental brain research 104 (1995), S. 275-286 
    Details
    ISSN: 1432-1106
    Keywords: Corpus callosum ; Vision ; Cortex ; Plasticity ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract During normal postnatal development, there is an overproduction and subsequent partial elimination of the callosal projections of cortical areas 17 and 18 in the cat. In the present study, we investigated how neonatal splitting of the optic chiasm affects this process. Our results indicate that neonatal splitting of the optic chiasm exaggerates the normally occurring partial elimination of immature callosal projections: it causes a significant reduction in the total number of neurons in the supragranular layers that send an axon through the corpus callosum. It does not, however, cause a significant change in the number of callosally projecting neurons in the infragranular layers. These data suggest that in addition to other factors previously described, the level or spatial distribution of correlated binocular input to visual cortical neurons may influence the stabilization/elimination of immature callosal connections.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00242013
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  • 5
    Electronic Resource
    Electronic Resource
    Dopaminergic control of transmission from group II muscle afferents to spinal neurones in the cat and guinea-pig (1995)
    Springer
    Experimental brain research 105 (1995), S. 39-47 
    Details
    ISSN: 1432-1106
    Keywords: Dopamine ; Group II muscle afferents ; Spinal cord ; Cat ; Guinea-pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of dopamine and its agonists on transmission from muscle afferents to spinal neurones were investigated in the cat and guinea-pig spinal cord, by measuring the drug effects on the amplitude of monosynaptic field potentials evoked by electrical stimulation of group I and group II muscle afferents. Local iontophoretic application of dopamine, the dopamine D1/D5 agonist SKF-38393 and the D2/D3/D4 agonist quinpirole all depressed the group II field potentials evoked at the base of the dorsal horn. Group II field potentials in the intermediate zone were depressed by dopamine to a similar degree as the dorsal horn field potentials, whereas the dopamine agonists were without effect upon them. The intermediate zone field potentials evoked by group I muscle afferents were not depressed by any of the drugs. The dopamine-evoked depression of the group II-evoked field potentials in the dorsal horn in the guinea-pig spinal cord was reduced by the simultaneous application of haloperidol. The results demonstrate that dopamine receptors mediate the depression of transmission from group II muscle afferents to interneurones in the dorsal horn, but not to neurones in the intermediate zone of the spinal cord.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00242180
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  • 6
    Electronic Resource
    Electronic Resource
    Transmission characteristics for the 1:1 linkage between slowly adapting type II fibers and their cuneate target neurons in cat (1995)
    Springer
    Experimental brain research 105 (1995), S. 67-75 
    Details
    ISSN: 1432-1106
    Keywords: Slowly adapting type II ; Cuneate neuron ; Synaptic transmission ; Tactile afferent fiber ; Somatosensory system ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Transmission from single, identified, slowly adapting type II (SAII) tactile fibers to their target neurons in the cuneate nucleus was examined in anesthetized cats. Simultaneous recordings were made from cuneate neurons and from fine, intact fascicles of the superficial radial nerve in which it was possible to identify and monitor the activity of each group II fiber. Selective activation of individual SAII fibers was achieved by means of skin stimulation with fine probes, in conjunction with extensive forelimb denervation. Responses were studied for seven SAII-driven cuneate neurons. For three there was unequivocal monitoring of the identified SAII input fiber. However, in six of the seven there was evidence that just one SAII fiber provided suprathreshold input to the cuneate neuron, and neither temporal nor spatial summation was required for reliable transmission. Cuneate impulse rates, in response to SAII inputs lasting 1 s, were less than 250 impulses per second, even though the SAII impulse rates could be 500 s-1. Responses to individual SAII impulses consisted of a burst of 2–3 impulses at low SAII input rates, but burst responses disappeared at high SAII rates. In all three SAII-cuneate pairs studied, the transmission security (the percentage of SAII impulses that evoked cuneate spike output) exceeded 80% in response to static skin displacement and in response to certain frequencies of skin vibration, in particular, at 100–200 Hz, exceeded 98% when the SAII fiber responded near the 1∶1 level (one impulse per vibration cycle). Transmission characteristics for the SAII-cuneate linkage resulted in the cuneate neuron showing tight phaselocking of responses to high-frequency (〉100 Hz) vibrotactile stimuli and higher impulse rates than its SAII input (up to input rates of ∼50 impulses s-1). Security of transmission across the SAII-cuneate synapse is similar to that demonstrated previously for tactile fibers of the SAI and Pacinian corpuscle (PC)-related classes, which suggests that there is no marked differential specialization in transmission characteristics for dorsal column nuclei neurons that receive input from different tactile fiber classes. Furthermore, it means that the reported failure of individual SAII fiber inputs to generate conscious sensation in man following intraneural microstimulation is not related to transmission failure at the first central relay.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00242183
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  • 7
    Electronic Resource
    Electronic Resource
    Relationship of simultaneously recorded cerebellar nuclear neuron discharge to the acquisition of a complex, operantly conditioned forelimb movement in cats (1995)
    Springer
    Experimental brain research 105 (1995), S. 325-330 
    Details
    ISSN: 1432-1106
    Keywords: Cerebellum ; Motor learning ; Reaching ; Cerebellar nuclei ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This study was designed to examine the changes in the modulation of small populations of cerebellar neurons during the acquisition of a complex, operantly conditioned forelimb task in cats. The experiments are based on the general postulate that, during the learning of a complex motor behavior, the cerebellum is important for generating a coordinated movement that meets the task's objectives, and that, as the cerebellum participates in this process, it acts to reinforce the effective motor pattern once it has been established. This specific study examines whether the changes in the modulation of cerebellar nuclear neurons during the learning of this task are consistent with this view. Cats were required to learn to move the manipulandum through a novel pattern of 2–3 consecutive straight grooves connected end to end in different spatial configurations, e.g., the letter L, an inverted L, and the letter C. Throughout the acquisition process, 6–12 single units were recorded simultaneously in the cerebellar nuclei, and the kinematics of the movement were evaluated using an Optotrak system. Cells were recorded from the two interposed nuclei and the dentate nucleus in these initial studies. Trials were sorted off-line based on the level of skill at which the required movement was performed. This was assessed using several objective criteria such as movement times, kinematic characteristics, and smoothness (number of peaks in the velocity profile). Event-related histograms then were constructed from each group of sorted trials. Changes in modulation related to a specific event were measured in successive histograms for each neuron. One of the most consistent findings across the cells in all nuclei was that the magnitude of the task-related modulation reached a peak at the time the task was first performed reasonably well and then progressively decreased (but did not disappear) as the task became well practiced. Both the initial increase and the subsequent decrease in response amplitude were significant statistically. The implications of these observations are discussed in the context of the role the cerebellum may play in the acquisition of complex motor tasks.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00240970
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  • 8
    Electronic Resource
    Electronic Resource
    Express saccades in cat: effects of task and target modality (1995)
    Springer
    Experimental brain research 103 (1995), S. 209-217 
    Details
    ISSN: 1432-1106
    Keywords: Express saccade ; Reaction time ; Attention ; Fixation ; Orienting response ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Saccadic eye movements to visual, auditory, and bimodal targets were measured in four adult cats. Bimodal targets were visual and auditory stimuli presented simultaneously at the same location. Three behavioral tasks were used: a fixation task and two saccadic tracking tasks (gap and overlap task). In the fixation task, a sensory stimulus was presented at a randomly selected location, and the saccade to fixate that stimulus was measured. In the gap and overlap tasks, a second target (hereafter called the saccade target) was presented after the cat had fixated the first target. In the gap task, the fixation target was switched off before the saccade target was turned on; in the overlap task, the saccade target was presented before the fixation target was switched off. All tasks required the cats to redirect their gaze toward the target (within a specified degree of accuracy) within 500 ms of target onset, and in all tasks target positions were varied randomly over five possible locations along the horizontal meridian within the cat's oculomotor range. In the gap task, a significantly greater proportion of saccadic reaction times (SRTs) were less than 125 ms, and mean SRTs were significantly shorter than in the fixation task. With visual targets, saccade latencies were significantly shorter in the gap task than in the overlap task, while, with bimodal targets, saccade latencies were similar in the gap and overlap tasks. On the fixation task, SRTs to auditory targets were longer than those to either visual or bimodal targets, but on the gap task, SRTs to auditory targets were shorter than those to visual or bimodal targets. Thus, SRTs reflected an interaction between target modality and task. Because target locations were unpredictable, these results demonstrate that cats, as well as primates, can produce very short latency goal-directed saccades.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00231707
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  • 9
    Electronic Resource
    Electronic Resource
    Cross-correlation of augmenting expiratory neurons of the Bötzinger complex in the cat (1995)
    Springer
    Experimental brain research 103 (1995), S. 251-255 
    Details
    ISSN: 1432-1106
    Keywords: Respiratory neurophysiology ; Cross-correlation ; Bötzinger complex ; Expiratory neurons ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Ipsilateral and contralateral pairs of augmenting expiratory neurons were recorded simultaneously from the Bötzinger complex using glass-coated tungsten microelectrodes in pentobarbitone-anaesthetized cats. The neurons were identified both by firing pattern and by antidromic activation from the contralateral site of the dorsal respiratory group. Cross-correlation histograms of the extracellularly recorded action potentials were calculated in order to detect short time-scale synchronizations of firing indicative of synaptic connections between the neurons. The cross-correlation histograms for 40 ipsilateral pairs of neurons less than 1 mm apart showed eight (20%) narrow troughs (mean half-amplitude width ±SD, 1.1±0.37 ms) at short latencies (mean latency±SD, 1.0±0.35 ms) suggestive of monosynaptic inhibition. These included two cross-correlation histograms which showed troughs on both sides of time zero, indicating a mutual inhibition. For another four pairs of neurons (10%), a central broad peak suggestive of common activation due to either excitation or release from inhibition was evident. Contralateral pairs of expiratory neurons of the Bötzinger complex were examined in a similar manner. The cross-correlation histograms for 43 pairs of neurons showed five (12%) narrow troughs (mean half-amplitude width±SD, 1.2±0.67 ms) at short latencies (mean latency±SD, 2.7±1.47 ms) suggestive of monosynaptic inhibition. These included one cross-correlation histogram which showed troughs (one not statistically significant) on both sides of time zero, indicating a mutual inhibition. For another two pairs of neurons (4.6%) a central, broad peak suggestive of common activation due to either excitation or release from inhibition was evident. We conclude that inhibitory interconnections exist between augmenting expiratory neurons of the Bötzinger complex ipsilaterally and contralaterally. These connections may synchronize the expiratory burst of activity within this population and assist in the patterning of the burst.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00231711
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  • 10
    Electronic Resource
    Electronic Resource
    Binaural noise stimulation of auditory callosal fibers of the cat: responses to interaural time delays (1995)
    Springer
    Experimental brain research 104 (1995), S. 30-40 
    Details
    ISSN: 1432-1106
    Keywords: Corpus callosum ; Sound localization ; Interaural time delays ; Midline fusion ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The corpus callosum, the principal neocortical commissure, allows for the interhemispheric transfer of lateralized information between the hemispheres. The aim of the present experiment was to study callosal transfer of auditory information in the cat, with particular reference to its contribution to sound localization. The corpus callosum was approached under direct visual control, and axonic responses were recorded under light anesthesia using glass micro-pipettes. Results showed that auditory information is transmitted in the posterior portion of the callosum. Diotic presentations, in which interaural time delay was manipulated, indicated that, for a large number of fibers, the largest excitatory or inhibitory interactions were obtained at null interaural time delay, a condition which supports the notion of a callosal contribution to auditory midline fusion. However, an important number of callosal fibers was also found to be excited maximally at specific, non-zero interaural time delays, suggesting that they preferred sounds situated at spatial locations other than the midline. The results are discussed in relation to those obtained electrophysiologically for the visual and somesthesic modalities and in terms of results obtained in human and animal behavioral experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00229853
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  • 11
    Electronic Resource
    Electronic Resource
    Brainstem modulation of signal transmission through the cat dorsal lateral geniculate nucleus (1995)
    Springer
    Experimental brain research 103 (1995), S. 372-384 
    Details
    ISSN: 1432-1106
    Keywords: Contrast gain ; Lateral geniculate nucleus ; Neuromodulation ; Retinogeniculate transmission Lagged and nonlagged cells ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We studied changes in retinogeniculate transmission that occur during variation of modulatory brainstem input and during variation of stimulus contrast. Responses of single cells in the dorsal lateral geniculate nucleus (dLGN) to a stationary flashing light spot of varying contrast were measured with and without electrical stimulation of the peribrachial region (PBR) of the brain-stem. PBR stimulation increased the contrast gain (slope of response versus contrast curve) and the dynamic response range (range between spontaneous activity and maximal firing). Lagged and nonlagged X-cells reached the midpoint of the dynamic response range at lower contrasts during PBR stimulation than in the controls. No comparable change was seen for Y-cells. Only minor changes of threshold contrast were seen. The characteristics of the retinogeniculate transmission were directly studied by comparing the response of dLGN cells with their retinal input (slow potentials, S-potentials). With increasing contrast there was a marked increase in the transfer ratio (proportion of impulses in the input that generates action potentials in the dLGN cell). The transfer ratio seemed to be primarily determined by the firing rate of the retinal input. The transfer ratio increased with increasing input rates from low values near threshold to values that could approach 1 at high-input firing rates. PBR stimulation increased the transfer ratio, particularly at moderate input firing rates. The increased transfer ratio, caused by increasing input firing rates, enhanced the response versus contrast characteristics through an increase in contrast gain and dynamic response range. The modulatory input from the PBR further enhanced these characteristics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00241496
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  • 12
    Electronic Resource
    Electronic Resource
    The auditory pathway in cat corpus callosum (1995)
    Springer
    Experimental brain research 104 (1995), S. 534-540 
    Details
    ISSN: 1432-1106
    Keywords: Corpus callosum ; Auditory pathway ; Primary auditory field ; Tonotopy ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The cortical auditory fields of the two hemispheres are interconnected via the corpus callosum. We have investigated the topographical arrangement of auditory callosal axons in the cat. Following circumscribed biocytin injections in the primary (AI), secondary (AII), anterior (AAF) and posterior (PAF) auditory fields, labelled axons have been found in the posterior two-thirds of the corpus callosum. Callosal axons labelled by small individual cortical injections did not form a tight bundle at the callosal midsagittal plane but spread over as much as one-third of the corpus callosum. Axons originating from different auditory fields were roughly topographically ordered, reflecting to some extent the rostro-caudal position of the field of origin. Axons from AAF crossed on average more rostrally than axons from AI; the latter crossed more rostrally than axons from PAF and AIL Callosal axons originating in a discrete part of the cortex travelled first in a relatively tight bundle to the telo-diencephalic junction and then dispersed progressively. In conclusion, the cat corpus callosum does not contain a sector reserved for auditory axons, nor a strictly topographically ordered auditory pathway. This observation is of relevance to neuropsychological and neuropathological observations in man.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00231988
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  • 13
    Electronic Resource
    Electronic Resource
    Depression of transmission from group II muscle afferents by electrical stimulation of the cuneiform nucleus in the cat (1995)
    Springer
    Experimental brain research 105 (1995), S. 25-38 
    Details
    ISSN: 1432-1106
    Keywords: Cuneiform nucleus ; Synaptic transmission ; Spindle afferents ; Spinal cord ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of short trains of electrical stimuli applied within the cuneiform nucleus and the subcuneiform region were examined on transmission from group I and group II muscle afferents to first-order spinal neurons. Variations in the effectiveness of transmission from these afferents were assessed from changes in the sizes of the monosynaptic component of extracellular field potentials evoked following stimulation of muscle nerves. Field potentials evoked from group II muscle afferents in the dorsal horn of the midlumbar and sacral segments and in the intermediate zone of the midlumbar segments were reduced when the test stimuli applied to peripheral nerves were preceded by conditioning stimulation of the cuneiform nucleus or the subcuneiform region. The depression occurred at conditioning-testing intervals of 20–400 ms, being maximal at intervals of 32–72 ms for dorsal horn potentials and 40–100 ms for intermediate zone potentials. At the shortest intervals, both group II and group I field potentials in the intermediate zone were depressed. Conditioning stimulation of the cuneiform nucleus depressed group II field potentials nearly as effectively as conditioning stimulation of the coerulear or raphe nuclei. We propose that the nonselective depression of transmission from group I and II afferents at short intervals is due to the activation of reticulospinal pathways by cells or fibers stimulated within the cuneiform area. We also propose that the selective depression of transmission from group II afferents at long intervals is mediated at least partly by monoaminergic pathways, in view of the similarity of the effects of conditioning stimulation of the cuneiform nucleus and of the brainstem monoaminergic nuclei and by directly applied monoamines (Bras et al. 1990). In addition, it might be caused by primary afferent depolarization mediated by non-monoaminergic fibers (Riddell et al. 1992).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00242179
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  • 14
    Electronic Resource
    Electronic Resource
    Distribution of vestibulospinal synaptic input to cat triceps surae motoneurons (1995)
    Springer
    Experimental brain research 107 (1995), S. 1-8 
    Details
    ISSN: 1432-1106
    Keywords: Deiters' nucleus ; Vestibulospinal system ; Motoneurons ; Synaptic input ; Synaptic currents ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We applied supramaximal, repetitive stimulation to the lateral vestibular nucleus (Deiters' nucleus, DN) at 200 Hz to evoke steady-state synaptic potentials in ipsilateral triceps surae motoneurons of the cat. The effective synaptic currents underlying these potentials were measured using a modified voltage-clamp technique. The steady-state effective synaptic currents evoked by activating DN were generally small and depolarizing (mean±SD 2.5±2.6 nA). DN stimulation generated hyperpolarizing synaptic currents in 2 of the 34 triceps motoneurons studied. The effective synaptic currents from DN tended to be larger in putative type F motoneurons than in putative type S cells (type F mean 3.0±3.1 nA; type S mean 1.8±1.0 nA). There was a statistically significant difference between the inputs to putative type FF and putative type S motoneurons (mean difference 2.8 nA, t=2.87, P〈0.01). The synaptic input from DN to medial gastrocnemius motoneurons had approximately the same mean amplitude as that from homonymous la afferent fibers. However, the distribution of DN input with respect to putative motor unit type was the opposite of that previously reported for Ia afferent input. Thus, the synaptic input from DN might act to compress the range of recruitment thresholds within the motoneuron pool and thereby increase the gain of its input-output function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00228010
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  • 15
    Electronic Resource
    Electronic Resource
    Non-length-tuned cells in layers II/III and IV of the visual cortex: the effect of blockade of layer VI on responses to stimuli of different lengths (1995)
    Springer
    Experimental brain research 104 (1995), S. 12-20 
    Details
    ISSN: 1432-1106
    Keywords: Visual cortex ; Layer VI to layer IV ; Non-length-tuned cells ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We have previously shown, using a local inactivation technique, that layer VI provides a facilitatory input to the majority of hypercomplex cells located in layer IV above, and hence to layers II/III, which in many cases enhances length selectivity. However, many cells in these layers are not tuned for stimulus length, being equally responsive to long and short stimuli. Thus it is important to know whether layer VI can influence the responses of these cells. We have now used a similar paradigm of iontophoretic application of GABA to examine the effect of blockade of layer VI on the length tuning profiles of these cells in layers II–IV. During the blockade of layer VI, the most common effect, seen in 41% of the cells, was inhibition of visual responses, (i.e. commensurate with loss of a facilitatory input). An increase in response magnitude was found in 21% of the population, and responses were unaffected in 36% of cells tested. This suggests that the predominant influence of local regions of layer VI on this cell type, located in layers II/III and IV, is facilitatory, with a smaller proportion of cells receiving an inhibitory input. Such effects were seen even with the shortest lengths tested, suggesting once more that elements of layer VI are responsive to stimuli much shorter than was previously accepted. Thus these data suggest that layer VI plays a role in the generation of the response dynamics of non-length-tuned cells in overlying layers II/III and IV.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00229851
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  • 16
    Electronic Resource
    Electronic Resource
    On-line compensation of gaze shifts perturbed by micro-stimulation of the superior colliculus in the cat with unrestrained head (1995)
    Springer
    Experimental brain research 106 (1995), S. 196-204 
    Details
    ISSN: 1432-1106
    Keywords: Gaze shifts ; Dynamic feedback ; Superior colliculus ; Microstimulation ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Prior studies have led to the gaze feedback hypothesis, which states that quick orienting movements of the visual axis (gaze shifts) are controlled by a feedback system. We have previously provided evidence for this hypothesis by extending the original study of Mays and Sparks (1980) to the cat with unrestrained head (Pélisson et al. 1989). We showed that cats compensated for a stimulation-induced perturbation of initial gaze position by generating, in the dark, an accurate gaze shift towards the remembered location of a flashed target. In the present study, we investigate goal-directed gaze shifts perturbed “in flight” by a brief stimulation of the superior colliculus. The microstimulation parameters were tuned such that significant perturbations were induced without halting the movement. The ambient light was turned off at the onset of the gaze shift, suppressing any visual feedback. We observed that, following stimulation offset, the gaze shift showed temporal and spatial changes in its trajectory to compensate for the transient perturbation. Such compensations, which occurred “on-line” before gaze shift termination, involved both eye and head movements and had dynamic characteristics resembling those of unperturbed saccadic gaze shifts. These on-line compensations maintained gaze accuracy when the stimulation was applied during the early phase of large and medium (about 60 and 40°) movements. These results are compatible with the notion of a gaze feedback loop providing a dynamic gaze error signal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00241115
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  • 17
    Electronic Resource
    Electronic Resource
    Analysis of potentials induced in red nucleus neurones from the somaesthetic pathway stimulated at the bulbar level (1995)
    Springer
    Experimental brain research 106 (1995), S. 377-390 
    Details
    ISSN: 1432-1106
    Keywords: Motor control ; Somaesthesia ; Magnocellular red nucleus ; Intracellular recording ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A somaesthetic pathway to the magnocellular red nucleus (RNm) via relays other than corticoor cerebello-rubral relays was previously found to exist in the cat. At the brainstem level, the ascending spinorubral fibres follow the medial lemniscus (LM). The present paper aims at describing in detail and evaluating the quantitative importance of the short-latency responses in RNm cells after microstimulation performed in the LM through a monopolar electrode. The RNm cells, tested intracellularly in cats anaesthetized with α-choralose and placed in a stereotaxic device, were identified by their antidromic activation to stimulation of the rubrospinal tract in the cervical cord. It was established that single-shock stimulation below 100 μA current delivered to the LM induced short-latency postsynaptic potentials (PSPs) in 87% of all the rubrospinal cells tested. The responses were indeed due to activation of LM fibres, as demonstrated by different tests: the location of the electrode tip in the LM was verified by recording, with the same electrode, the potentials evoked by stimulating the dorsal columns of the cord. The site was later confirmed histologically. The absence of stimulus spread from the LM to the underlying pyramidal tract was systematically checked by simultaneously recording the responses evoked in RNm cells and in the motor cortex. Monosynaptic excitatory responses (EPSPs) were evoked in RNm cells with a minimum stimulating current of less than 20 μA in the LM and a mean threshold of 42 μA. Disynaptic inhibitory potentials (IPSPs) were evoked in 23% of these cells with single-pulse stimulation. These latter responses showed a temporal facilitation with short trains of three pulses, which indicated that they were transmitted through inhibitory interneurones. Recordings were also performed from presumed LM fibre terminals running inside the RNm. The results therefore confirm the existence of strong lemniscal projections to RNm and demonstrate that they transmit both excitatory and inhibitory messages to rubrospinal cells. As the somaesthetic pathway to the RNm was previously found to come from the spinal cord, where it is located in the ventral portion, the present results also confirm that the LM is composed of fibres originating not only from neurones in the dorsal column nuclei, but also from cells placed at the segmental levels of the cord. The presumed sensorimotor function of this ascending pathway is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00231061
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  • 18
    Electronic Resource
    Electronic Resource
    Functional relation between corticonuclear input and movements evoked on microstimulation in cerebellar nucleus interpositus anterior in the cat (1995)
    Springer
    Experimental brain research 106 (1995), S. 365-376 
    Details
    ISSN: 1432-1106
    Keywords: Climbing fibres ; Rubrospinal tract ; Motor control ; Motor learning ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The functional relation between receptive fields of climbing fibres projecting to the C1, C3 and Y zones and forelimb movements controlled by nucleus interpositus anterior via the rubrospinal tract were studied in cats decerebrated at the pre-collicular level. Microelectrode tracks were made through the caudal half of nucleus interpositus anterior. This part of the nucleus receives its cerebellar cortical projection from the forelimb areas of these three sagittal zones. The C3 zone has been demonstrated to consist of smaller functional units called microzones. Natural stimulation of the forelimb skin evoked positive field potentials in the nucleus. These potentials have previously been shown to be generated by climbing fibre-activated Purkinje cells and were mapped at each nuclear site, to establish the climbing fibre receptive fields of the afferent microzones. The forelimb movement evoked by microstimulation at the same site was then studied. The movements usually involved more than one limb segment. Shoulder retraction and elbow flexion were frequently evoked, whereas elbow extension was rare and shoulder protraction never observed. In total, movements at the shoulder and/or elbow occurred for 96% of the interpositus sites. At the wrist, flexion and extension movements caused by muscles with radial, central or ulnar insertions on the paw were all relatively common. Pure supination and pronation movements were also observed. Movements of the digits consisted mainly of dorsal flexion of central or ulnar digits. A comparison of climbing fibre receptive fields and associated movements for a total of 110 nuclear sites indicated a general specificity of the input-output relationship of this cerebellar control system. Several findings suggested that the movement evoked from a particular site would act to withdraw the area of the skin corresponding to the climbing fibre receptive field of the afferent microzones. For example, sites with receptive fields on the dorsum of the paw were frequently associated with palmar flexion at the wrist, whereas sites with receptive fields on the ventral side of the paw and forearm were associated with dorsiflexion at the wrist. Correspondingly, receptive fields on the lateral side of the forearm and paw were often associated with flexion at the elbow, whereas sites with receptive fields on the radial side of the forearm were associated with elbow extension. The proximal movements that were frequently observed also for distal receptive fields may serve to produce a general shortening of the limb to enhance efficiency of the withdrawal. It has previously been suggested that the cerebellar control of forelimb movements via the rubrospinal tract has a modular organisation. Each module would consist of a cell group in the nucleus interpositus anterior and its afferent microzones in the C1, C3 and Y zones, characterised by a homogenous set of climbing fibre receptive fields. The results of the present study support this organisational principle, and suggest that the efferent action of a module is to withdraw the receptive field from an external stimulus. Possible functional interpretations of the action of this system during explorative and reaching movements are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00231060
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  • 19
    Electronic Resource
    Electronic Resource
    Stimulation of the group I extensor afferents prolongs the stance phase in walking cats (1995)
    Springer
    Experimental brain research 103 (1995), S. 20-30 
    Details
    ISSN: 1432-1106
    Keywords: Ib afferent ; Locomotion ; Walking ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Group I afferents in nerves innervating the lateral gastrocnemius-soleus (LG-Sol), plantaris (P1), and vastus lateralis/intermedius (VL/VI) muscles were stimulated during walking in decerebrate cats. The stimulus trains were triggered at a fixed delay following the onset of bursts in the medial gastrocnemius muscle. Stimulation of all three nerves with long stimulus trains (〉600 ms) prolonged the extensor bursts and delayed the onset of flexor burst activity. LG-Sol nerve stimulation had the strongest effect; often delaying the onset of flexor burst activity until the stimulus train was ended. By contrast, flexor bursts were usually initiated before the end of the stimulus train to the P1 and VL/VI nerves. The minimum stimulus strength required to increase the cycle period was between 1.3×threshold and 1.6×threshold for all three nerves. Simultaneous stimulation of the P1 and VL/VI nerves produced a larger effect on the cycle period than stimulation of either nerve alone. The spatial summation of inputs from knee and ankle muscles suggests that the excitatory action of the group I afferents during the stance phase is distributed to all leg extensor muscles. Stimulation of the group I afferents in extensor nerves generally produced an increase in the amplitude of the heteronymous extensor EMG towards the end of the stance phase. This increase in amplitude occurred even though there were only weak monosynaptic connections between the stimulated afferents and the motoneurones that innervated these heteronymous muscles. This suggests that the excitation was produced via oligosynaptic projections onto the extensor motoneuronal pool. Stimulation with 300 ms trains during the early part of flexion resulted in abrupt termination of the swing phase and reinitiation of the stance phase of the step cycle. The swing phase resumed coincidently with the stimulus offset. Usually, stimulation of two extensor nerves at group I strengths was required to elicit this effect. We were unable to establish the relative contributions of input from the group 1a and group 1b afferents to prolonging the stance phase. However, we consider it likely that group Ib afferents contribute significantly, since their activation has been shown to prolong extensor burst activity in reduced spinal preparations. Thus, our results add support to the hypothesis that unloading of the hindlimb during late stance is a necessary condition for the initiation of the swing phase in walking animals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00241961
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  • 20
    Electronic Resource
    Electronic Resource
    Effects of eye position on auditory localization and neural representation of space in superior colliculus of cats (1995)
    Springer
    Experimental brain research 104 (1995), S. 402-408 
    Details
    ISSN: 1432-1106
    Keywords: Superior colliculus ; Sensory integration ; Auditory localization ; Eye movement ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The maps of visual and auditory space within the superior colliculus are in approximate register both with each other and with the underlying motor maps associated with orienting responses. The fact that eyes and ears can move independently poses a problem for the sensorimotor organization of these two modalities. By monitoring eye and pinna positions in alert, head-fixed cats, we showed that the accuracy of saccadic eye movements to auditory targets was little affected by eye eccentricity (range ±15 deg) at the onset of the sound. A possible neural basis for this behavioral compensation was suggested by recordings from superior colliculus neurons. The preferred sound directions of some neurons in the deep layers of this midbrain nucleus exhibited a shift with the direction of gaze, while in others the response throughout the auditory receptive field was either increased or decreased, suggesting that changes in eye position alter the gain of the auditory response.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00231975
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  • 21
    Electronic Resource
    Electronic Resource
    Effect of reversible dorsal cold block on the persistence of inhibition generated by spinal reflexes (1995)
    Springer
    Experimental brain research 107 (1995), S. 205-214 
    Details
    ISSN: 1432-1106
    Keywords: Motoneuron ; Stretch reflex ; Cutaneous ; Contralateral ; Spinal ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of bilateral focal cooling of dorsolateral thoracic spinal cord on segmental reflex pathways to the triceps surae muscles were assessed in decerebrate cats from the reflex forces produced by single shocks or trains of electrical stimuli applied to the ipsilateral caudal cutaneous sural and the contralateral tibial nerves. The validity of the dorsal cold block technique as a substitute for acute surgical dorsal hemisection was established by showing that focal cooling reliably reproduced the stretch-induced “clasp knife” inhibition of triceps surae reflexive force seen following dorsal hemisection. Under control (warm) conditions, the inhibitory components of electrically evoked ipsilateral sural and contralateral tibial reflexes faded rapidly during sustained trains, with a resultant production of large-amplitude reflex force as measured from either the entire triceps surae or from the medial gastrocnemius muscle alone. Dorsal cold block greatly reduced the amplitude of reflexive force evoked by sustained electrical stimulation of either nerve. Indeed, the cold block completely reversed the sign of train-evoked reflexes to a net inhibition of reflex force output in one-half of the sural and one-half of the contralateral tibial stimulation experiments. Peak transient forces evoked by single shocks to the sural or contralateral tibial nerves were also sometimes reduced, but this result was more variable than for prolonged nerve stimulation. The persistence of activity in segmental inhibitory pathways during dorsal cold block, as indicated by instances of reflex sign reversal, suggests that descending bulbospinal pathways traversing the dorsolateral funiculi may be responsible for “fading” of segmental inhibitory reflex components in decerebrate cats with intact spinal cords during sustained afferent input. The possibility that the enhanced magnitude and duration of segmental inhibition during cold block will increase the likelihood of disruption of the size principle for motoneuron recruitment is also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230042
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  • 22
    Electronic Resource
    Electronic Resource
    Differences in the temporal dynamics of the visual ON and OFF pathways (1995)
    Springer
    Experimental brain research 104 (1995), S. 171-176 
    Details
    ISSN: 1432-1106
    Keywords: Visual channels ; Lateral geniculate nucleus ; Visual cortex ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The temporal structure of spike trains recorded from optic fibers and single units of the lateral geniculate nucleus (LGN) and primary visual cortex of the cat was studied with a novel method of inter-spike interval analysis. ON type relay cells of the LGN exhibited a multimodal interval distribution preferring a distinct interval (fundamental interval) and its multiples during the sustained light response, whereas most OFF cells showed a broad, unimodal distribution. The general pattern of the interval distribution was relatively independent of stimulus size and contrast and the degree of light adaptation. Simultaneously recorded S-potentials originating from the retinal input generally produced only a single peak at the fundamental interval length. Therefore, the multimodal interval distribution of LGN cells seems to be a result of intra-geniculate inhibition. Cortical cells also showed a weak tendency to fire with spike intervals similar to LGN cells. Therefore, the regular firing pattern observed at peripheral stages of the visual pathway can persist at higher levels and might promote the occurrence of oscillatory activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00229868
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  • 23
    Electronic Resource
    Electronic Resource
    The effects of baclofen on the stretch reflex parameters of the cat (1995)
    Springer
    Experimental brain research 104 (1995), S. 287-296 
    Details
    ISSN: 1432-1106
    Keywords: Baclofen ; Stretch reflex ; Muscle stiffness ; Spinal cord ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Experiments were done in cats decerebrated at the precollicular postmammillary level to determine how a tonic increase of presynaptic inhibition of the intraspinal terminals of muscle spindle afferents changes the mechanical properties of the soleus stretch reflex (s.r.). Baclofen, a specific GABAB receptor agonist, was injected i.v. (1–2 mg/kg) so as to induce a tonic increase in presynaptic inhibition. The effects of baclofen on the stiffness and threshold of the s.r. were determined, respectively, from plots of stiffness vs background force and force vs length (length-tension plot). Baclofen, at these doses, had no effect on the excitation-contraction coupling properties of muscle or on the intrinsic stiffness-force relation. Changes of the soleus background force, required to obtain the stiffness vs force plots, were produced by stimulation of the contralateral common peroneal nerve or the posterior tibial nerve and occasionally by electrical stimulation in the area of the red nucleus. The stiffness of the s.r. as a function of the background force level was determined by stretching the muscle with a square pulse of 1–2 mm amplitude and 200–300 ms duration. The stiffness at each force level was calculated by dividing the change in force by the change in length, at a point where the force trace had stabilized. The length-tension relation of the s.r. was determined by stretching the muscle 12–17 mm at a constant rate of 1–2 mm/s. At all force levels, baclofen produced a significant decrease (40% or more) in the s.r. stiffness, within 10–15 min of injection as determined from the stiffness-force plots. The length-tension plots revealed that the decrease of s.r. stiffness was always accompanied by an increase in the s.r. threshold (typically 2–3 mm). It is suggested, therefore, that the s.r. threshold is not an independent variable, depending on the membrane potential of the α- motoneurons, and additionally on the level of presynaptic inhibition of the muscle spindle afferent terminals. The present results also imply that it may be possible for the CNS to adaptively modify the s.r. stiffness via presynaptic inhibition of the intraspinal terminals of muscle afferents. However, any such change of s.r. stiffness will be accompanied by a change in the s.r. threshold.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00242014
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    Electronic Resource
    Effects of eye position on saccadic eye movements and on the neuronal responses to auditory and visual stimuli in cat superior colliculus (1995)
    Springer
    Experimental brain research 103 (1995), S. 227-242 
    Details
    ISSN: 1432-1106
    Keywords: Vision ; Audition ; Superior colliculus ; Saccade ; Multisensory convergence ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Many neurons in the deeper layers of the superior colliculus (SC) respond to multiple sensory inputs — visual, auditory, and somatic — as well as provide signals essential for saccadic eye movements to targets in different modalities. When the eyes and pinnae are in primary position, the neural map of auditory space is in rough topographic alignment with the map of visual space, and if the auditory map is based solely on head-pinna coordinates, any changes in eye position in the orbit will cause misalignment of the maps. We investigated the effects of eye position on the response of sound-sensitive neurons in the SC of cats because previous work on cats and on monkeys had suggested the possibility of species differences in the representation of auditory signals in the SC. We also investigated the effects of eye position on the accuracy of saccades to auditory, visual, and bimodal stimuli. All studies were conducted in alert, trained cats with the head restrained in a fixed position. Neuronal and behavioral responses were studied during periods when the eyes were steadily directed to different positions relative to the position of the sound. Cats showed partial compensation for eye position in making saccades, regardless of the modality of the target, and they showed similar patterns of error in saccades to auditory and visual targets. These behavioral data are consistent with coding the location of visual and auditory targets in the same coordinate system. In the vast majority of intermediate-layer neurons, eye position significantly affected the number of spikes evoked by sound stimuli. For most of these neurons, changes in eye position produced significant shifts in the speaker location producing maximal response. In some neurons, eye position significantly facilitated the magnitude of neuronal response evoked by sounds from a variety of speaker locations. Because few pinna movements could be detected, it is unlikely that these changes in neuronal response could be due to changes in the position of the pinnae. Our results indicate that the deep layers of the SC contain an eye-centered representation of sound location. Because eye position did not affect the percentage of neurons exhibiting multimodal integration, visual and auditory maps appear to remain integrated in the SC even when the eyes are directed eccentrically. Examination of the effects of eye position on neuronal responses to visual stimuli revealed that a substantial minority of neurons showed quantitative changes in the magnitude of response to visual stimuli when the retinal locus of stimulation was held constant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00231709
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    Electronic Resource
    Electronic Resource
    Encoding of jaw movements by central trigeminal neurons with cutaneous receptive fields (1995)
    Springer
    Experimental brain research 104 (1995), S. 363-375 
    Details
    ISSN: 1432-1106
    Keywords: Cutaneous ; Jaw movements ; Vi ; Kinesthesia ; Trigeminothalamic ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Neurons with orofacial cutaneous receptive fields that responded to jaw movements were recorded in the trigeminal subnucleus interpolaris of the cat. Movement-related neuronal activity was identified by imposing passive ramp and hold stretches of the jaw at four different rates. Thirty-nine neurons with hair (26), skin (9), or convergent (4) receptive fields were studied. Thalamic projection neurons were identified by antidromic stimulation of the ventroposteromedial nucleus of the thalamus. The receptive fields of movement-related hair units included multiple hairs located mainly around the angle of the jaw and chin. The receptive fields of movement-related skin units were smaller than those of hair units and they were located primarily around the angle of the mouth. The convergent units had more than one receptive field that usually included hair or skin. All of the hair units were activated both during opening and closing jaw movements. They typically responded with short bursts of action potentials. Four units with skin receptive fields exhibited similar responses. The five skin units that did not show bursting activity included two that were active during both opening and closing of the jaw, two that were active only during opening, and one that was tonically active during maintained open position. All of the convergent units showed biphasic responses, and three responded with bursts. The maximum discharge rate, the mean discharge rate (mean bursting rate for units with bursting responses), and the total number of spikes per movement were measured. Statistical analysis was performed on these variables to assess functional properties of each unit. The results were used to classify units as velocity, speed, direction, or transient motion detectors. Thirty-three percent of the neurons were trigeminothalamic neurons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00231972
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    Electronic Resource
    Electronic Resource
    Latency variability of responses to visual stimuli in cells of the cat's lateral geniculate nucleus (1995)
    Springer
    Experimental brain research 105 (1995), S. 7-17 
    Details
    ISSN: 1432-1106
    Keywords: Lagged cells ; Nonlagged cells ; Visual system ; Thalamus ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We constructed average histograms from responses evoked by flashing stimuli and noted previously described variations in the shape of the response profile, particularly with respect to sharpness of the peak. To express this variable, we measured the half-rise latency, which is the latency from stimulus onset required to reach half the maximum response. A short half-rise latency, which is characteristic of nonlagged cells, is associated with a brisk response and sharp peak; a long half-rise latency, characteristic of lagged cells, is associated with a sluggish response and broad peak. Nonlagged cells were readily seen; we attempted to identify cells with long latencies as lagged, but we were unable to do so unambiguously due to failure to observe lagged properties other than latency. We thus refer to these latter cells as having “lagged-like” responses to indicate that we are not certain whether these are indeed lagged cells. In addition to the histograms, we analyzed the individual response trials that were summed to create each histogram, and we used spike density analysis to estimate the initial response latency to the flashing spot for each trial. We found that lagged-like responses were associated with more variability in initial response latency than were nonlagged responses. We then employed an alignment procedure to eliminate latency variation from individual trials; that is, responses during individual trials were shifted in time as needed so that each had a latency equal to the average latency of all trials. We used these “aligned” trials to create a second, “aligned” response histogram for each cell. The alignment procedure had little effect on nonlagged responses, because these were already well aligned due to consistent response latencies amongst trials. For lagged-like responses, however, the alignment made a dramatic difference. The aligned histograms looked very much like those for nonlagged responses: the responses appeared brisk, with a sharply rising peak that was fairly high in amplitude. We thus conclude that the slow build up to a relatively low peak of firing of the lagged-like response histogram is not an accurate reflection of responses on single trials. Instead, the sluggishness of lagged-like responses inferred from average response histograms results from temporal smearing due to latency variability amongst trials. We thus conclude that there is relatively little difference in briskness between nonlagged and lagged-like responses to single stimuli.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00242177
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    Electronic Resource
    Integration in trigeminal premotor interneurones in the cat (1995)
    Springer
    Experimental brain research 104 (1995), S. 449-461 
    Details
    ISSN: 1432-1106
    Keywords: Premotor interneurones ; Subnucleus oralis-γ ; Trigeminal motor nucleus ; Spike-triggered averaging ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A population of last-order interneurones within the rostrodorsal part of the oral nucleus of the spinal trigeminal tract (NVspo-γ) has been investigated in 21 chloralose anaesthetised cats. The neurones were identified by their antidromic (AD) response to microstimulation (median current 9 μA, range 3–39 μA) of the ipsior the contralateral masseteric subnucleus of the trigeminal motor nucleus. Fifty-one of 113 interneurones tested were discharged from the ipsilateral and eight from the contralateral motor nucleus. The average conduction time was 0.50 ms from the ipsilateral and 0.74 ms from the contralateral motoneurone pool. Conduction velocities of the axons ranged from 2.0 to 14.0 ms. The pattern of primary afferent input onto the selected neurones was analysed by graded electrical stimulation of dissected trigeminal nerves. Low-threshold afferents innervating the intraoral mucosa including the tongue and the perioral skin of the lower lip were the most effective inputs, as judged from both the frequency of occurrence and from the latencies of the evoked spike discharges. Ninety-six percent of the neurones responded to stimulation of the inferior alveolar nerve (Alv inf) and 83% responded to stimulation of the lingual nerve (Ling). The median threshold strength required to evoke the Alv inf and the Ling responses was 1.7 T (range 1.0–3.6 T) and 1.3 T (range 1.0–5.0 T), respectively. The median latency to spike discharges evoked by the Alv inf was 2.0 ms (range 1.3–4.8 ms) and to the Ling it was 2.5 ms (range 1.4–7.0 ms). Action potentials elicited by stimulation of the masseteric and digastric nerves were observed in 40% and 10% of the neurones, respectively. These responses, which had median latencies of more than 8 ms (range 4.7–16.0 ms), were only seen at stimulation intensities above 2 T (range 2.5–25 T). An input from the maxillary whisker nerve was seen in only one case. Postspike averages of the extracellular field potentials within the trigeminal motoneurone subnuclei evoked by interneuronal spikes were made in a subsample of 51 NVspo-γ neurones activated by iontophoresis of L-glutamic acid. Excitatory synaptic effects within the masseteric subnucleus were observed in eight cases. An inhibitory effect was seen in one case. One specific neurone gave an excitatory extracellular field potential within the digastric motoneurone subnucleus. This interneurone was AD activated from the digastric, but not from the masseteric subnucleus. The physiological properties of the NVspo-γ-mass interneurones are discussed in relation to their suggested roles in the phase-dependent control of the trigeminal motoneurones during oro-facial masticatory behaviours.
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    URL: http://dx.doi.org/10.1007/BF00231979
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    An in vivo electrophysiological investigation of group Ia afferent fibres and ventral horn terminations in the cat spinal cord (1995)
    Springer
    Experimental brain research 106 (1995), S. 403-417 
    Details
    ISSN: 1432-1106
    Keywords: Spinal Ia terminations ; Myelinated fibres ; Action potentials ; Primary afferent depolarization ; Transmitter release ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract An extracellular microstimulation technique has been used to investigate and compare the properties of group I primary afferent myelinated fibres in the dorsal column and group Ia unmyelinated terminations in the lumbar spinal cord of cats anaesthetised with pentobarbitone sodium. Fibres were distinguished from terminations on the basis of location, anodic blocking factor and sensitivity to GABAA mimetics. The recovery curves of threshold following an orthodromic impulse provided an estimate of both action potential duration and rate of repolarization. The action potentials of group Ia terminations were of briefer duration (by a factor of approximately 2) with more rapid rates of repolarization (factor of approximately 3) than those of the myelinated fibres. The prolongation of termination but not fibre action potentials by microelectrophoretic tetraethylammonium and 4-aminopyridine indicated the presence of voltage-activated potassium channels in the termination membrane. Differences in the effects on Ia termination action potentials of depolarizations (reductions in threshold) associated with a preceding action potential, synaptically released GABA, microelectrophoretic piperidine-4-sulphonic acid or dl-homocysteic acid suggest that an increase in termination membrane conductance is the major factor in the reduction of transmitter release during the activation of presynaptic GABAA receptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00231063
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  • 29
    Electronic Resource
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    Evidence for high-velocity smooth pursuit in the trained cat (1995)
    Springer
    Experimental brain research 106 (1995), S. 509-512 
    Details
    ISSN: 1432-1106
    Keywords: Eye movement ; Smooth pursuit ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract It is generally accepted that in cats smooth pursuit velocity of the eye never exceeds a few degrees per second. This is in contrast with observations in primates, where smooth pursuit velocity can reach values as high as 100°/s. Cats were trained to fixate and pursue spots of light appearing on a translucent screen. Spots were moved in the horizontal and vertical planes at different constant velocities up to 80°/s. Eye position was recorded with the sclerai search coil technique. Naive cats did not pursue moving targets with high efficiency. Smooth eye movement velocity saturated at 5°/s. After a few days of training, smooth-pursuit eye velocity increased with target velocity and saturated at 25°/s on average. However, velocities twice as high have been observed frequently. When the target was unexpectedly extinguished, smooth eye movement velocity dropped to values close to 0°/s in approximately 350 ms. After a short training period (usually 5 times the same target presentation), the eye continued to move smoothly until the target reappeared. These data suggest that smooth pursuit eye movements of the cat are qualitatively similar to those of primates, but reach lower velocities and are more variable in their characteristics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00231076
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    Electronic Resource
    Observations of chemical processing in the circumstellar environment (1995)
    Springer
    Astrophysics and space science 224 (1995), S. 81-84 
    Details
    ISSN: 1572-946X
    Keywords: Chemistry ; Depletions ; Shocks ; IRAS 05338-0624 ; NGC 1333 IRAS 4
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract High resolution interferometer and single-dish observations of young, deeply embedded stellar systems reveal a complex chemistry in the circumstellar environments of low to intermediate mass stars. Depletions of gas-phase molecules, grain mantle evaporation, and shock interactions actively drive chemical processes in different regions around young stars. We present results for two systems, IRAS 05338-0624 and NGC 1333 IRAS 4, to illustrate the behavior found and to examine the physical processes at work.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00667826
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    Electronic Resource
    Electronic Resource
    Ozone exposure suppresses epithelium-dependent relaxation in feline airway (1995)
    Springer
    Lung 173 (1995), S. 47-56 
    Details
    ISSN: 1432-1750
    Keywords: Airway hyperresponsiveness ; Ozone ; Airway epithelial cell ; Bronchiole ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We examined the effect of exposure to ozone on the epithelium-dependent relaxation (EpDR) of bronchioles evoked by electrical field stimulation (EFS) in a feline model with hyperresponsive airways induced by exposure to ozone. Airway responsiveness was assessed by measuring the increases in total pulmonary resistance (RL) produced by aerosolized acetylcholine (ACh) in vivo. Airway responsiveness was also measured in vitro in dissected bronchiolar ring preparations. Exposure to ozone (3 ppm, 2 h) significantly increased the airway responsiveness in vivo. The concentration of ACh required increasing R L to 200% of the baseline value, decreased from 1.97 mg/ml (GSEM 1.94) to 0.12 mg/ml (GSEM 1.77, p 〈 0.01) after exposure to ozone. EFS evoked atropine-, guanethidine-, and tetrodotoxin-resistant relaxations in the control bronchiolar rings precontracted by 5-hydroxytryptamine. Such relaxation was significantly suppressed by the mechanical denudation of epithelium, confirming that it was epithelium dependent. The amplitude of EpDR was significantly suppressed in the animals exposed to ozone. These results suggest that EpDR is present in cats, and that its inhibition may contribute to the development of airway hyperresponsiveness.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00167600
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  • 32
    Electronic Resource
    Electronic Resource
    Interactions of the subthalamic nucleus and the subpallidal area in oro-facial dyskinesia: role of GABA and glutamate (1995)
    Springer
    Psychopharmacology 119 (1995), S. 20-26 
    Details
    ISSN: 1432-2072
    Keywords: Oro-facial dyskinesia ; Subthalamic nucleus ; Globus pallidus ; GABA ; Glutamate ; Behaviour ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Previous studies have shown that lowering the GABAergic activity in the sub-pallidal area (SP) in the cat results in the display of oro-facial dyskinesia (OFD). There exists an intense, mutual anatomical connection between the SP and the subthalamic nucleus and the adjoining lateral hypothalamic area (STH). The present study investigated whether the STH is also involved in OFD. Once this turned out to be true (see below), it was investigated whether the SP-specific OFD is funneled via the STH, or vice versa. Bilateral injections of low doses (50–250 ng) of picrotoxin, a non-competitive GABA antagonist, into the STH were found to elicit OFD. This effect which was quantified in terms of numbers of tongue protrusions, was dose-dependent: a bell-shaped dose-response was found (50–500 ng). The OFD elicited by the most effective dose of picrotoxin (250 ng) was significantly antagonized by muscimol, a specific GABAA agonist, in a dose (50 ng) which itself was ineffective, indicating GABA specificity. In addition, it was found that OFD elicited by local injections of picrotoxin (250 ng) into the STH was significantly attenuated by SP injections of the broad spectrum glutamate antagonist kynurenic acid in a dose (1000 ng) which itself was ineffective, but not by muscimol (100 ng), indicating that the STH-elicited OFD needs an intact and functioning glutaminergic, but not GABAergic, transmission process in the SP for its expression. Finally, it was found that OFD elicited by picrotoxin injections (500 ng) into the SP was significantly attenuated by muscimol injections (50 ng) into the STH, indicating that the SP-elicited OFD needs an intact and functioning GABAergic transmission process in the STH for its expression.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02246049
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  • 33
    Electronic Resource
    Electronic Resource
    Horseradish peroxidase in axons of the dorsal funiculi of the cat: distribution after an injection of the enzyme into the dorsal column nuclei (1995)
    Springer
    Cell & tissue research 283 (1995), S. 67-73 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Node of Ranvier ; Axon ; Horseradish peroxidase (HRP) ; Retrograde axonal transport ; Electron microscopy ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Horseradish peroxidase (HRP) was injected into the left dorsal column nuclei of adult cats. Large dorsal funiculi axons of the C3, C5, C8 and L7 segments were searched for HRP-activity after 12, 24, 36 and 48 h using light and electron microscopy. Accumulations of intra-axonal HRP-positive bodies occurred at nodes of Ranvier in the C3–C8 segments at 12, 24 and 36 h and in the L7 segments at 24, 36, and 48 h. The accumulations of HRP in three spatio-temporally different consecutive patterns, noted earlier at nodes of Ranvier in the peripheral nervous system (PNS) portion of feline alpha motor axons for more than 70 h after an intramuscular injection of the enzyme, were not observed in the present material. We suggest that the differences in the modes in which large PNS and CNS axons interact with retrogradely transported HRP are due to differences in the organization of the respective nodal regions. We also emphasize that endocytosis via axon terminals in the CNS normally represents uptake of material from an extracellular space which is controlled and protected by the blood-brain barrier. This is in contrast to endocytosis via axon terminals in a muscle, which represents uptake of material from an extracellular space openly exposed to influx of different substances from the blood stream.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410050513
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  • 34
    Electronic Resource
    Electronic Resource
    A monoclonal anticarbohydrate antibody detecting superfast myosin in the masseter muscle (1995)
    Springer
    Cell & tissue research 283 (1995), S. 85-92 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Masseter muscle ; Limb muscles ; Superfast fibres ; Myosin heavy chains ; Glycosylation ; Galactose ; ATPase ; Cat ; Dog ; Macaca fascicularis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Superfast-contracting muscle fibres (II M) were identified by ATPase staining and after incubation with an antiserum raised against myosin type II M and with an antibody raised against the Galα1–3Galβ1–4GlcNAc structure. II M fibres were present in masseter muscles from cat, dog and Macaca fascicularis but not in limb muscles from the same animals and not in masseter muscles from rat, pig, cow or man. Electrophoresis and staining of blots from myosin preparations showed that the anticarbohydrate antibody detected myosin heavy chains from cat masseter but not myosin heavy chains from cat biceps. The α-galactose specific lectin Griffonia simplicifolia isolectin B4 (GS I B4) did not stain muscle fibres or myosin heavy chains. Therefore, the epitope on myosin heavy chains defined by the anticarbohydrate antibody is presumably not Galα1–3Galβ1–4GlcNAc although the antibody staining was strongly inhibited after absorption by 10 mM of this trisaccharide. Antibody staining of the muscle fibres was totally inhibited by adding 10 mM p-nitrophenyl β-D-glucuronide to the incubation medium. The results thus imply that an anticarbohydrate antibody distinctively detects a carbohydrate epitope specific for myosin in superfast contracting muscle fibres from jaw-closing muscles and confirm that this epitope is not present in other muscle fibre types. This appears to be the first report on differentiated glycosylation among myosin isoforms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410050515
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  • 35
    Electronic Resource
    Electronic Resource
    A new combination of methods for the localization, identification, and three-dimensional reconstruction of the sensory endings of articular afferents characterized by electrophysiology (1995)
    Springer
    Cell & tissue research 281 (1995), S. 283-294 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Articular afferents ; Corpuscular endings ; Free nerve endings ; Morpho-functional examination ; Three-dimensional reconstruction ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. A combination of methods is described to identify and reconstruct corpuscular and non-corpuscular sensory endings of group II and group III nerve fibers following functional examination by electrophysiology. Afferent units activated by electrical stimulation of the medial articular nerve of the cat’s knee were analyzed by single fiber recordings and characterized by their responsiveness to mechanical stimuli. The receptive fields of the units were closely demarcated by fine needles when the responses elicited by insertion of the needles were being recorded. After fixation, the tissue around the demarcated field was dissected and histologically processed. Series of semithin sections were cut from the embedded tissue blocks containing the receptive fields. Corpuscular endings of group II fibers and peripheral myelinated group III nerve fibers, presumably corresponding to the characterized units, were identified by light microscopy of semithin sections and localized within the demarcated area. Non-corpuscular endings were identified by electron microscopy of ultrathin sections cut in alternation with, or after re-embedding of, semithin sections. Morphometric analysis of ultrathin section series allowed the measurement of parameters such as the mean axon diameter and the organelle content of the sensory endings. The methods described are appropriate for collecting data that correlate the structural and functional characteristics of sensory endings in deep tissues.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410050425
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  • 36
    Electronic Resource
    Electronic Resource
    Association of immune cells with neuroepithelial bodies in the lungs of neonatal dogs, cats and hamsters (1995)
    Springer
    Cell & tissue research 282 (1995), S. 519-522 
    Details
    ISSN: 1432-0878
    Keywords: Lungs ; Chemoreceptors ; Mast cells ; Eosinophils ; Neutrophils ; Newborns ; Dog ; Cat ; Golden hamster
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract A close topographical association between neuroepithelial bodies and immune cells is occasionally observed in the lungs of various neonatal mammalian species. The immune cells concerned are mast cells and neutrophil or eosinophil granulocytes. In the lungs of newborn puppies having undergone left lung autotransplantation, mast cells are particularly numerous in the airway mucosa of both right and left lungs and their association with neuroepithelial bodies is highly significant. Several of the substances known to be synthesized by the neuroepithelial bodies have a chemoattractive effect on immune cells. Thus, our observations indicate that intrapulmonary neuroepithelial bodies contribute to the local immune response.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00318884
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  • 37
    Electronic Resource
    Electronic Resource
    Association of immune cells with neuroepithelial bodies in the lungs of neonatal dogs, cats and hamsters (1995)
    Springer
    Cell & tissue research 282 (1995), S. 519-522 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Lungs ; Chemoreceptors ; Mast cells ; Eosinophils ; Neutrophils ; Newborns ; Dog ; Cat ; Golden hamster
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. A close topographical association between neuroepithelial bodies and immune cells is occasionally observed in the lungs of various neonatal mammalian species. The immune cells concerned are mast cells and neutrophil or eosinophil granulocytes. In the lungs of newborn puppies having undergone left lung autotransplantation, mast cells are particularly numerous in the airway mucosa of both right and left lungs and their association with neuroepithelial bodies is highly significant. Several of the substances known to be synthesized by the neuroepithelial bodies have a chemoattractive effect on immune cells. Thus, our observations indicate that intrapulmonary neuroepithelial bodies contribute to the local immune response.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410050503
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  • 38
    Electronic Resource
    Electronic Resource
    A new combination of methods for the localization, identification, and three-dimensional reconstruction of the sensory endings of articular afferents characterized by electrophysiology (1995)
    Springer
    Cell & tissue research 281 (1995), S. 283-294 
    Details
    ISSN: 1432-0878
    Keywords: Articular afferents ; Corpuscular endings ; Free nerve endings ; Morpho-functional examination ; Three-dimensional reconstruction ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract A combination of methods is described to identify and reconstruct corpuscular and non-corpuscular sensory endings of group II and group III nerve fibers following functional examination by electrophysiology. Afferent units activated by electrical stimulation of the medial articular nerve of the cat's knee were analyzed by single fiber recordings and characterized by their responsiveness to mechanical stimuli. The receptive fields of the units were closely demarcated by fine needles when the responses elicited by insertion of the needles were being recorded. After fixation, the tissue around the demarcated field was dissected and histologically processed. Series of semithin sections were cut from the embedded tissue blocks containing the receptive fields. Corpuscular endings of group II fibers and peripheral myelinated group III nerve fibers, presumably corresponding to the characterized units, were identified by light microscopy of semithin sections and localized within the demarcated area. Non-corpuscular endings were identified by electron microscopy of ultrathin sections cut in alternation with, or after re-embedding of, semithin sections. Morphometric analysis of ultrathin section series allowed the measurement of parameters such as the mean axon diameter and the organelle content of the sensory endings. The methods described are appropriate for collecting data that correlate the structural and functional characteristics of sensory endings in deep tissues.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00583397
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  • 39
    Electronic Resource
    Electronic Resource
    Intraretinal analysis of electroretinogram with K+ microelectrodes during acute intraocular pressure elevation (1995)
    Springer
    Documenta ophthalmologica 91 (1995), S. 129-139 
    Details
    ISSN: 1573-2622
    Keywords: Cat ; C-wave ; Electroretinogram ; Intraocular pressure ; Potassium ion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We examined the effects of acute intraocular pressure elevation on the intraretinal electroretinogram in the cat dark-adapted eye. Perfusion pressure of the eye (mean arterial pressure minus intraocular pressure) was regulated within the range of 25–75 mm Hg by increasing the intraocular pressure, which was adjusted by changing the height of the reservoir of balanced salt solution perfused into the eye through a needle placed in the anterior chamber. The vitreal electroretinogram, transepithelial c-wave, slow PIII and light-evoked decrease in extracellular K+ concentration were recorded during intraocular pressure elevation in the darkadapted retina. The c-wave increased in amplitude between 40 and 75 mm Hg of perfusion pressure and decreased below 40 mm Hg in some cases. These changes were unrelated to the standing potential. The transepithelial c-wave, slow PIII and light-evoked decrease in extracellular K+ concentration were larger in the range of perfusion pressure examined. These suggest that some factor induces electroretinographic changes that are not readily explained by hypoxia or pH changes alone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01203692
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  • 40
    Electronic Resource
    Electronic Resource
    The importance of chemical data for the study of interstellar shocks (1995)
    Springer
    Astrophysics and space science 233 (1995), S. 125-137 
    Details
    ISSN: 1572-946X
    Keywords: Interstellar Medium ; Dark Clouds ; Chemistry ; Bistability ; C-shock Waves
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Shock waves perturb the chemical state of the interstellar gas. We consider the effects of C-shocks on the composition of molecular clouds, for a range of values of the pre-shock gas density and magnetic induction. The time required to re-establish equilibrium in the post-shock gas depends on the initial conditions and can become very large. The significance of the two known chemical phases of dark clouds and of bistability is considered in this context.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00627340
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  • 41
    Electronic Resource
    Electronic Resource
    Molecular diagnostics of diffusive boundary layers (1995)
    Springer
    Astrophysics and space science 233 (1995), S. 161-164 
    Details
    ISSN: 1572-946X
    Keywords: Stars ; Chemistry ; Diffusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have assessed the role of diffusion in determining chemical abundances in molecular interface regions. Chemical models have been developed which include the appropriate diffusion terms and that are appropriate to a narrow diffusion region (∼0.01pc) that may exist at the interface between a dark core and a hot, shocked T-Tauri wind. We have assumed pressure balance throughout and have calculated the chemical abundances as functions of time and position through the interface. The results show that significant enhancements of detectable molecules/transitions are expected (e.g. CO J=6→5, OH and CH). Using a realistic value of the diffusion coefficient a diffusive region of dimension 0.01pc may be established within about 104 years. In general it seems likely that diffusion processes are highly significant on these and smaller lengthscales.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00627344
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  • 42
    Electronic Resource
    Electronic Resource
    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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  • 43
    Electronic Resource
    Electronic Resource
    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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  • 44
    Electronic Resource
    Electronic Resource
    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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  • 45
    Electronic Resource
    Electronic Resource
    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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  • 46
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    Electronic Resource
    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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  • 47
    Electronic Resource
    Electronic Resource
    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.
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    URL: http://dx.doi.org/10.1002/apmc.1995.052240117
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    Electronic Resource
    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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  • 49
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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.
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    URL: http://dx.doi.org/10.1002/apmc.1995.052250102
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  • 50
    Electronic Resource
    Electronic Resource
    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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  • 51
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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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052250109
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  • 52
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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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052250112
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  • 53
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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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  • 54
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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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052260106
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  • 55
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    Electronic Resource
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052260108
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  • 56
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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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052260113
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  • 57
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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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  • 58
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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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052270108
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  • 59
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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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052270111
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  • 60
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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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  • 62
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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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    URL: http://dx.doi.org/10.1002/apmc.1995.052280113
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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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  • 64
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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.
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    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.
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    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.
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    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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    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.
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    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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    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.
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    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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    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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    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.
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    URL: http://dx.doi.org/10.1002/apmc.1995.052320101
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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.
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    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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  • 79
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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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  • 80
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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.
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    URL: http://dx.doi.org/10.1002/apmc.1995.052330112
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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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    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.
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    URL: http://dx.doi.org/10.1002/bip.360350102
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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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  • 91
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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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360350210
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  • 92
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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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  • 93
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    Modeling of long-range electrostatic interactions in DNA (1995)
    New York : Wiley-Blackwell
    Biopolymers 35 (1995), S. 289-296 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We used a Monte Carlo approach to compute the statistical properties of closed DNA chains with different descriptions of the electrostatic interactions. We compared these computed results with experimentally measured knotting probabilities, which are very sensitive to intersegment interactions. The calculated results based on the Debye-Hückel approximation of the solution of the Poisson-Boltzmann equation agreed very well with the published experimental data, while potential based on counterion condensation theory was clearly less satisfactory. We then compared the simpler hard-core approximation of electrostatic interactions to the Debye-Hückel potential. The hard-core approximation, specified in terms of a DNA effective diameter, gives the same conformational properties of random coils as the Debye-Hückel approximation. We found clear but relatively small differences between the two potentials for the conformational properties of supercoiled DNA. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360350304
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  • 94
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    1H-, 13C-, and 113Cd-nmr study of the Cd(II) complex of a blocked peptide, Z-Cys-Ala-Pro-His-OMe, in organic solvents (1995)
    New York : Wiley-Blackwell
    Biopolymers 35 (1995), S. 319-329 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Cd(II) complex of a peptide, Z-Cys-Ala-Pro-His-OMe was prepared and characterized by absorption, CD, 1H-, 13C-, and 113Cd-nmr, and nuclear Overhauser effect spectroscopy (NOESY) spectra to show the coordination of cysteine thiolate and histidine imizazole to Cd(II) ion. The NOESY spectra in dimethyl formamide showed that the cysteine residue was in proximity to the histidine residue. These results reveal the dictation of Z-Cys-Ala-Pro-His-OMe to Cd(II) ion in solution. Temperature-dependent dissociation equilibrium of histidine imidazole in solution was observed in this complex. Structural features of the chelating peptide are discussed. © 1995 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360350307
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  • 95
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    Solution behavior of α-chymotrypsin dissolved in nonpolar organic solvents via hydrophobic ion pairing (1995)
    New York : Wiley-Blackwell
    Biopolymers 35 (1995), S. 451-456 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dissolution of α-chymotrypsin in nonpolar organic solvents can be achieved using hydrophobic ion pairing, whereby the polar counterions are replaced by a stoichiometric number of detergent molecules. Using Aerosol OT[AOT, sodium bis(2-octyl)sulfosuccinate], it is possible to partition significant amounts of the enzyme into alkanes and chlorocarbons. Apparent solubility in isooctane is greater than 1 mg/mL (80 μM). Necessary conditions for achieving effective partitioning of α-chymotrypsin into these solvents are described. Using CD spectroscopy, it can be shown that the AOT-α-chymotrypsin (CMT) complex retains its native secondary and tertiary structure when dissolved in alkanes, and that the globular structure is stable to more than 100°C. In contrast, α-chymotrypsin unfolds at 54°C in aqueous solution. The relative solubility of the AOT-CMT complex in a variety of alkanes and chlorocarbons is also reported. The native structure of α-chymotrypsin is maintained in carbon tetrachloride, but not in methylene chloride or chloroform. © 1995 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360350504
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  • 96
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    Hydrolysis of β-lactoglobulin by thermolysin and pepsin under high hydrostatic pressure (1995)
    New York : Wiley-Blackwell
    Biopolymers 35 (1995), S. 475-483 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hydrolysis of β-lactoglobulin with thermolysin and pepsin at pressures ranging between 0.1 and 350 MPa showed a significant increase of cleavage rates. Pressure-induced changes of susceptibility to hydrolysis of β-lactoglobulin proteolytic sites were also observed. The pressure, raised to 200 MPa, accelerates the hydrolysis of β-lactoglobulin by thermolysin and changes obtained peptide profiles. Initially, higher pressure makes the N-terminal, and to a smaller extent, C-terminal peptide fragments of β-lactoglobulin molecule, more susceptible to removal by thermolysin. This indicates combined influence of pressure-induced thermolysin activation and partial unfolding of β-lactoglobulin by compression at neutral pHs.The rates of hydrolysis of β-lactoglobulin by pepsin (negligible at 0.1 MPa) are increased considerably with pressure up to 300 MPa. The Susceptibility of β-lactoglobulin proteolytic sites to peptic cleavage remains constant over all the studied pressure range. The lack of significant qualitative changes in the peptic peptide profiles produced at different pressures and at clearly pressure-dependent rates points to negative reaction volume changes as the major factor in peptic hydrolysis of β-lactoglobulin under high pressure. Thus the β-lactoglobulin molecule resists pressure-induced unfolding in acid pHs and yields to it in neutral pHs. © 1995 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360350506
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  • 97
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    Competitive reactions in solutions of DNA and water-soluble interpolyelectrolyte complexes (1995)
    New York : Wiley-Blackwell
    Biopolymers 35 (1995), S. 523-531 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of competitive binding of two polyanions - DNA and synthetic fluorescence-tagged poly(methacrylate) (PMA*) - with the polycation-quencher poly(N-ethyl-4-vinyl-pyridinium) (PEVP) was studied by fluorescence quenching technique. It was found that ability of DNA to displace PMA *from the water-soluble nonstoichiometric interpolyelectrolyte complex (NPEC) formed by PMA* and PEVP - NPEC(PMA*-PEVP) - and to form water-soluble NPEC(DNA-PEVP) \documentclass{article}\pagestyle{empty}\begin{document}$$ NPEC(PMA^{*}\hbox{-}PEVP) + DNA \Leftrightarrow NPEC(DNA\hbox{-}PEVP) + PMA^{*}$$\end{document} can be determined by the parameter Ψ = PPMA*/PPEVP where PPMA* and PPEVP are the degrees of polymerization of PMA* and PEVP, respectively. In the case of Ψ 〈 1 the decrease of Ψ leads to the shift of the reaction equilibrium to the right, which can be explained by the gain of entropy due to the increase of the total number of polymeric particles in the solution. Introduction of alkali metal cations into the reaction mixture results in the shift of the reaction equilibrium, and according to their ability to shift the equilibrium to the right the cations can be arranged in the series Na+ 〉 K+ 〉 Li+. The substitution of native DNA by denatured DNA practically does not affect the reaction equilibrium in solutions of NaCl and KCl but considerably shifts it to the right in solutions of LiCl. The data obtained are in accordance with the differences in the selectivity of alkali cations binding with competitive polyanions. © 1995 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360350511
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  • 98
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    Design of B-DNA cross-linking and sequence-reading molecules (1995)
    New York : Wiley-Blackwell
    Biopolymers 35 (1995), S. 543-553 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We report the design of hybrid molecules to bind in the minor groove of B-DNA, which combine DNA alkylating and cross-linking ability for increased chemotherapeutic efficacy, with sequence specificity, to minimize side effects. Optimal linkage geometries have been determined for the synthesis of bis-anthramycin and anthramycin-netropsin hybrid molecules. Earlier studies on linked drugs have typically been based on molecular mechanics calculations. This work, in contrast, uses the observed crystal structures of a netropsin/DNA complex and a new anthramycin/DNA complex to determine the exact spacing between two individual drugs when bound in the minor groove of B-DNA. Molecular linkers then are designed and tested between these two experimental positions, to form a chimeric or bis-linked compound molecule. A linked anthramycin-netropsin molecule has been designed specifically to target the polypurine tract second-strand primer site of the reverse transcriptase of HIV-1. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360350513
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  • 99
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    Sequence and temperature dependence of the interbase hydrogen-bond breathing modes in B-DNA polymers: Comparison with low-frequency Raman peaks and their role in helix melting (1995)
    New York : Wiley-Blackwell
    Biopolymers 35 (1995), S. 573-582 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We carry out temperature-dependent lattice dynamics calculations to determine the vibrational normal modes associated with the interbase H-bond breathing motion in several B-DNA copolymers at temperatures from room temperature to the melting temperatures. We take into consideration Raman selection rules and incorporate a simple empirical model of Raman susceptibility in the interbase H bonds in our calculation and compare them to Raman measurements. Our calculations are carried out using empirical force constants that are not further refined to low-frequency spectra. Our calculations show the existence of strong interbase H-bond breathing modes at frequencies and with relative oscillator strengths close to the observed Raman peaks in the range of 60-140 cm-1 for the DNA sequences considered except for one helix. The correlation between the calculated and observed frequencies and oscillator strengths indicates that the observed Raman peaks in the frequency range are likely interbase H-bond breathing modes. We find that these modes exhibit sizable temperature as well as sequence dependence. We show the softening of these modes on approaching thermal denaturation that is also in agreement with the observed behavior in Raman and melting measurements. The sensitivity of the calculation on the empirical model of Raman susceptibility and the possible reasons for the discrepancy between a few calculated values and observations are discussed. © 1995 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360350603
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  • 100
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    Synthesis and interfacial behavior of poly(Lys-Tyr-Tyr-Lys) (1995)
    New York : Wiley-Blackwell
    Biopolymers 35 (1995), S. 629-637 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Poly(Lys-Tyr-Tyr-Lys) was synthesized by polycondensation of the tetrapeptide unit using paranitrophenyl esters. The conformation of poly (Lys-Tyr-Tyr-Lys) is very dependent on its environment. CD spectra in bulk are difficult to interpret owing to the contribution of Tyr residues, but from ir spectra it seems that poly(Lys-Tyr-Tyr-Lys) adopts preferentially an unordered conformation in water. Addition of salts induces a partial transition to a β structure. The behavior is different at interfaces. When poly(Lys-Tyr-Tyr-Lys) is spread as a film on a water subphase, the shape of the compression isotherm curves is compatible with a stacking of two β-sheets. On a KCl subphase, the polymer film is more expanded and more compressible, and the isotherm curve resembles that of a polymer in a random conformation. The analysis by CD and ir spectroscopy of transferred monolayers using the Langmuir-Blodgett technique allowed us to confirm and make these data more precise: on a water subphase the spectra are those of an antiparallel β structure. At the interface of a saline solution the spectra are compatible with a mixture of random coil (largely) and a small content of β structures. © 1995 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360350609
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