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  • 1990-1994  (26,639)
  • 1980-1984  (19,138)
  • Polymer and Materials Science  (36,309)
  • Organic Chemistry  (7,936)
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  • 101
    Electronic Resource
    Electronic Resource
    A comparison of the effects of the D1 receptor antagonists SCH 23390 and SCH 39166 on suppression of feeding behavior by the D1 agonist SKF38393 (1994)
    Springer
    Psychopharmacology 113 (1994), S. 328-333 
    Details
    ISSN: 1432-2072
    Keywords: Dopamine ; 5-HT2 ; 5-HT1C ; D1 ; SKF 38393 ; SKF 82958 ; SCH 39166 ; SCH 23390 ; Feeding ; Behavior ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The hypophagic effect of the D1 receptor agonist SKF 38393 is not dose-dependently antagonized by the D1 antagonist SCH 23390. Moreover, the receptor specificity of this interaction remains in question, since SCH 23390 has significant activity at both 5-HT2 and 5-HT1C receptors, and SKF 38393 also interacts with 5-HT1C receptors. To determine the relative significance of these actions, a comparison was made between the anorectic effects in rats of SCH 23390 (0.1–1.0 mg/kg) and the benzonaphthazepine SCH 39166 (0.1–3.0 mg/kg), a D1 antagonist with negligible affinity for 5-HT sites. Both compounds inhibited food-intake dose-dependently, with SCH 23390 being approximately twice as potent as SCH 39166. Behaviorally inactive and active doses of both antagonists were tested in combination with the D1 agonist SKF 38393 (10–56 mg/kg). Neither antagonist was able to produce more than a marginal attenuation of the agonist-induced hypophagia. This demonstrates that previous failures to reverse the behavioral actions of SKF 38393 by SCH 23390 were not due to specific actions of this particular antagonist. Finally, like SCH 23390, SCH 39166 (0.3 mg/kg) was able to attenuate fully the anorectic effects of the D1 agonist SKF 82958 (1.0 and 3.0 mg/kg), demonstrating that neither compound is intrinsically unable to block D1 receptor-mediated hypophagia. The results demonstrate the generality of the D1 antagonist-mediated effect on feeding and call into question the use of SKF 38393 as a D1 agonist in studies of feeding, and perhaps in other contexts as well.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02245205
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  • 102
    Electronic Resource
    Electronic Resource
    Prenatal nicotine exposure increased duration of nicotine-induced analgesia in adult rats (1994)
    Springer
    Psychopharmacology 113 (1994), S. 534-538 
    Details
    ISSN: 1432-2072
    Keywords: Nicotine ; Prenatal ; Analgesia ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effect of prenatal exposure to nicotine on nicotine-induced analgesia was studied in rats. The analgesic effect of a single dose of nicotine (1 mg/kg SC) was measured by the tail-flick technique, and two subsequent studies were carried out. In the first study, 7-month-old male rats, born to dams chronically treated with nicotine during pregnancy (NIC), exhibited prolonged nicotine-induced analgesia compared to matched controls. The second study was designed to explore whether rats prenatally exposed to nicotine (NIC rats) are born with an increased sensitivity to nicotine and whether there is any sex difference. The analgesic effect of nicotine was tested on control and NIC rats of both sexes once a month from 2 to 7 months of age. At an early age, male but not female NIC rats, exhibited shorter analgesic responses to nicotine than did the matched controls. With increasing age, however, the duration of nicotine analgesia began to be prolonged in NIC rats of both sexes. Significant differences between control and NIC rats were found at the age of 6 and 7 months, in both sexes. Thus, rats prenatally exposed to nicotine are not born with an increased sensitivity to the analgesic effect of a single dose of nicotine. This phenomenon develops later, during the course of life, independently of gender.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02245235
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  • 103
    Electronic Resource
    Electronic Resource
    Methamphetamine exposure during early postnatal development in rats: I. Acoustic startle augmentation and spatial learning deficits (1994)
    Springer
    Psychopharmacology 114 (1994), S. 392-401 
    Details
    ISSN: 1432-2072
    Keywords: Methamphetamine ; Rat ; Postnatal ; Acoustic startle ; Spatial learning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Methamphetamine (MA) induces neurotransmitter reductions and neurotoxicity at high doses in adult animals, but its effects on early brain development and behavior have received less attention. In this experiment the effects of MA exposure during a period equivalent to the human third trimester were examined. Rats (Sprague-Dawley CD) were injected subcutaneously withd-MA (30 mg/kg b.i.d.) early in postnatal development (days 1–10), later (postnatal days 11–20), or with water during both of these periods. Both early and later MA-exposed offspring exhibited augmented acoustic startle and impaired performance in a complex multiple-T water maze. Only the early MA exposure group showed a persistent deficit in weight while only the later MA exposure group showed impaired learning in the Morris hidden platform maze. Effects on locomoter activity are reported in the accompanying article. It was concluded that the effects of MA are both long lasting and stage dependent and involve cognitive as well as arousal functions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02249328
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  • 104
    Electronic Resource
    Electronic Resource
    Influence of 5-HT3 receptor antagonists and the indirect 5-HT agonist, dexfenfluramine, on heroin self-administration in rats (1994)
    Springer
    Psychopharmacology 114 (1994), S. 611-619 
    Details
    ISSN: 1432-2072
    Keywords: Heroin self-administration ; Rat ; 5-HT ; 2-HT3 receptor antagonists ; Ondansetron ; MDL72222 ; Indirect 5-HT agonist ; Dexfenfluramine ; Opioid reinforcement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The purpose of the present study was to examine the effects of the 5-HT3 antagonists ondansetron and MDL72222, and the 5-HT releaser and reuptake inhibitor dexfenfluramine, on intravenous heroin self-administration by Wistar rats. Using separate squads of animals, two separate schedules of heroin reinforcement were used; a relatively low dose (0.03 mg/kg per infusion) made available under a FR5 schedule for 1 h each day, and a moderate heroin dose (0.1 mg/kg per infusion) available under a FR1 schedule for 2 h each day. Following the acquisition of stable levels of responding across days, both naloxone pretreatment (0.25 mg/kg SC) and halving the heroin infusion dose produced increases in operant responding for heroin at each concentration. Neither ondansetron (0.01–1 mg/kg SC) nor MDL72222 (0.1–3 mg/kg SC) pretreatment influenced heroin self-administration. Chronic treatment (5 day) of ondansetron (0.01–0.1 mg/kg) was similarly ineffective. However, dexfenfluramine (0.5–2.5 mg/kg IP) consistently reduced heroin self-administration at doses producing only modest decreases in food responding. These findings are in contrast to place conditioning studies, which show that 5-HT3 antagonists but not indirect 5-HT agonists block a morphine-induced place preference. Reasons for such discrepancies remain to be determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02244992
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  • 105
    Electronic Resource
    Electronic Resource
    Effects of (R)-α-methylhistamine and scopolamine on spatial learning in the rat assessed using a water maze (1994)
    Springer
    Psychopharmacology 114 (1994), S. 651-656 
    Details
    ISSN: 1432-2072
    Keywords: (R)-α-Methylhistamine ; Scopolamine ; Histamine ; Cognition ; Water maze ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of (R)-α-methylhistamine ((R)-α-MeHA, a selective H3-receptor agonist) and scopolamine (SCOP, a muscarinic antagonist) were investigated on spatial learning and memory in the rat (Hooded Lister) using a water maze (WM). (R)-α-MeHA treatment (6.3 and 10 mg/kg IP) had no apparent effect on spatial learning but did result in enhanced spatial recall at the higher dose, assessed by a transfer (probe) test after training. In contrast, SCOP (0.5 mg/kg IP) induced a learning and memory deficit measured both during and after training. In animals treated with (R)-α-MeHA and SCOP, (R)-α-MeHA partially (6.3 mg/kg) and completely (10 mg/kg) reversed the SCOP-induced deficit during the training phase, while in the post-training transfer test, (R)-α-MeHA (10 mg/kg) significantly reduced the SCOP-induced memory deficit. None of the treatments described resulted in impaired visual acuity as demonstrated by a raised platform test. These results are consistent with a role for histamine in cognitive processes and suggest a possible interaction between central histamine and cholinergic mechanisms associated with rodent spatial learning and memory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02244997
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  • 106
    Electronic Resource
    Electronic Resource
    Ethological study of the effects of tetrahydroaminoacridine (THA) on social recognition in rats (1994)
    Springer
    Psychopharmacology 114 (1994), S. 644-650 
    Details
    ISSN: 1432-2072
    Keywords: Social recognition ; Cognition ; Social interaction ; Ethological method ; Tetrahydroaminoacridine ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Two major difficulties confront ethopharmacological investigations on cognitive abilities such as social recognition in drug-treated animals involved in free social interactions. The first concerns the choice of the most relevant behaviours, those reflecting the cognitive abilities attributed to the animals and assessing the specificity of the drug activity, and those reflecting non-specific drug effects. The second refers to the experimenter's awareness that in contrast to physical objects, social stimuli respond to drug-treated subjects and that their own level of responsiveness may influence the changes of drug-treated subjects' social interest. In addition, their contribution may vary according to the different treatments the drug-treated subjects receive. In examining the effects of tetrahydroaminoacridine (THA) at doses of 0.3, 1 and 3 mg/kg on the ability of adult male rats to recognize previously encountered conspecifics, we attempted to take into consideration such difficulties. A detailed behavioural profile of drug-treated rats was reported to separate specific from non-specific effects of THA. In addition, rats were assigned an index of responsibility for contact which takes into account the interactive dimension of each dyad and allows relevant comparisons between different treatments. The doses of THA which were found to decrease the duration of exploration of a familiar juvenile were also found to decrease the number of contacts initiated by the drug-treated subjects. THA induced a relative increase in body care by comparison to saline treatment. However, it had no effect of locomotor activity and rearing of the subjects. These findings enable dissociation of the effects of THA on cognitive versus non-cognitive processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02244996
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  • 107
    Electronic Resource
    Electronic Resource
    Effects of GABA-ergic drugs on penile erection induced by apomorphine in rats (1994)
    Springer
    Psychopharmacology 115 (1994), S. 249-253 
    Details
    ISSN: 1432-2072
    Keywords: Penile erection ; Muscimol ; Baclofen ; Bicuculline ; Picrotoxin ; Phaclofen ; Apomorphine ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of GABA agonists and antagonists on penile erection (PE) induced by apomorphine were investigated in rats. Subcutaneous (SC) administration of apomorphine (0.01–0.1 mg/kg) induces a dose-dependent PE in rats. The maximum effect was obtained with 0.1 mg/kg of the drug. The response was decreased with increasing doses of apomorphine from 0.1 to 0.5 mg/kg. The response induced by apomorphine (0.1–0.5 mg/kg) was decreased in animals pretreated with either the GABA-A agonist muscimol or the GABA-B agonist baclofen. Combination of muscimol with baclofen caused a stronger inhibitory effect on apomorphine-induced PE. Bicuculline or picrotoxin but not phaclofen reduced the inhibitory effect of muscimol on PE induced by apomorphine, whereas phaclofen but not GABA-A antagonists decreased the inhibitory action of baclofen on apomorphine-induced PE. Pretreatment of animals with higher doses of the GABA-A antagonists bicuculline and picrotoxin or the GABA-B antagonist phaclofen elicited inhibition of apomorphine-induced PE. However, the inhibitory effects of GABA-A and GABA-B antagonists are lost on combination. Administration of GABA-A and GABA-B receptor stimulation inhibit PE induced by dopaminergic mechanism(s).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02244779
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  • 108
    Electronic Resource
    Electronic Resource
    Microcatalepsy and disruption of forelimb usage during operant behavior: differences between dopamine D1 (SCH-23390) and D2 (raclopride) antagonists (1994)
    Springer
    Psychopharmacology 115 (1994), S. 24-30 
    Details
    ISSN: 1432-2072
    Keywords: Dopamine receptors ; Neuroleptics ; SCH-23390 ; Raclopride ; Response duration ; Catalepsy ; Operant behavior ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In an experiment designed to distinguish between the behavioral consequences of treatment with SCH-23390, a D1 dopamine receptor blocker, and raclopride, a D2 antagonist, rats were trained to perform a water-reinforced forelimb operant response. Response rate and the duration of each forelimb contact with the operandum were recorded. In addition, the durations of the rat's visits to the reward well were detected by a photobeam which was blocked by the rat's muzzle as it remained at the reward well. In a between-groups dosing design, separate groups of rats (11–13 rats/group) received SCH-23390 (0, 0.01, 0.02, 0.04, 0.08, 0.12 mg/kg, IP, 30 min) or raclopride (0. 0.05, 0.1, 0.2, 0.4, 0.8 mg/kg, IP, 30 min) for 21 consecutive days. Quantitative analyses indicated that for comparable amounts of operant rate reduction, raclopride had a significantly greater tendency than SCH-23390 to increase the duration of operant responses and to increase the maximum muzzle entry duration (i.e., to induce microcatalepsy). The results support the idea that at relatively low doses D2 antagonism is more likely than D1 antagonism to produce effects identified preclinically with extrapyramidal side effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02244747
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  • 109
    Electronic Resource
    Electronic Resource
    Behavioural and pharmacological characterisation of the elevated “zero-maze” as an animal model of anxiety (1994)
    Springer
    Psychopharmacology 116 (1994), S. 56-64 
    Details
    ISSN: 1432-2072
    Keywords: Anxiety ; Elevated zero-maze ; Rat ; Diazepam ; Chlordiazepoxide ; mCPP ; 8-OH-DPAT ; Ondansetron ; Head dips ; Stretched attend postures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The elevated “zero-maze” is a modification of the elevated plus-maze model of anxiety in rats which incorporates both traditional and novel ethological measures in the analysis of drug effects. The novel design comprises an elevated annular platform with two opposite enclosed quadrants and two open, removing any ambiguity in interpretation of time spent on the central square of the traditional design and allowing uninterrupted exploration. Using this model, the reference benzodiazepine anxiolytics, diazepam (0.125–0.5 mg/kg) and chlordiazepoxide (0.5–2.0 mg/kg) significantly increased the percentage of time spent in the open quadrants (% TO) and the frequency of head dips over the edge of the platform (HDIPS), and reduced the frequency of stretched attend postures (SAP) from the closed to open quadrants. In contrast, the anxiogenic drugm-chlorophenyl-piperazine (mCPP; 0.25–1.0 mg/kg) induced the opposite effects, decreasing %TO and HDIPS, and increasing SAP. The 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT; 0.001–0.1 mg/kg) had no effects on either %TO or HDIPS, but did decrease SAP at 0.01 mg/kg although not at higher or lower doses. Similarly, the 5-HT3 receptor antagonist, ondansetron (0.0001–1.0 mg/kg) decreased SAP and increased %TO at 0.01 mg/kg, but not at other doses. The present data suggest that a combination of the novel “zero-maze” design and a detailed ethological analysis provides a sensitive model for the detection of anxiolytic/anxiogenic drug action.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02244871
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  • 110
    Electronic Resource
    Electronic Resource
    Effects of SR 48692, a selective non-peptide neurotensin receptor antagonist, on two dopamine-dependent behavioural responses in mice and rats (1994)
    Springer
    Psychopharmacology 116 (1994), S. 237-241 
    Details
    ISSN: 1432-2072
    Keywords: SR 48692 ; Neurotensin receptor antagonist ; Dopamine ; Apomorphine ; Bromocriptine ; (+) SKF 38393 ; (+) Amphetamine ; Turning ; Yawning ; Mouse ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract One major mechanism underlying the central action of neurotensin is an interaction with the function of dopamine (DA)-containing neurons. In addition, direct or indirect DA agonists have been reported to promote neurotensin release. We have found that SR 48692, a non-peptide neurotensin receptor antagonist (0.04 – 0.64 mg/kg orally), antagonizes (50–65%) yawning induced by apomorphine (0.07 mg/kg SC) or bromocriptine (2 mg/kg IP) in rats, and turning behaviour induced by intrastriatal injection of apomorphine (0.25 µg), (+) SKF 38393 (0.1 µg), bromocriptine (0.01 ng) or (+) amphetamine (10 µg) in mice. Other apomorphine-induced effects in mice and rats such as climbing, hypothermia, hypo- and hyper-locomotion, penile erections and stereotypies were not significantly modified by SR 48692. Taken together, these data suggest that neurotensin may play a permissive role in the expression of some but not all behavioural responses to DA receptor stimulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02245067
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  • 111
    Electronic Resource
    Electronic Resource
    Atropine effects on the intermediate stage and paradoxical sleep in rats (1994)
    Springer
    Psychopharmacology 116 (1994), S. 304-308 
    Details
    ISSN: 1432-2072
    Keywords: Intermediate stage of sleep ; Paradoxical sleep ; Spindle ; Theta rhythm ; Atropine ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Paradoxical sleep (PS) in the rat, cat and mouse is preceded and sometimes followed by a short-lasting intermediate stage (IS) characterized by high amplitude cortical spindles and low frequency theta rhythm. This stage, which is mimicked by an intercollicular transection, is massively extended at the expense of PS by low doses of barbiturates. Since the pontine cholinergic cell activation of PS is suppressed by barbiturates, we studied whether atropine, an antimuscarinic compound, extends IS at the expense of PS. Atropine sulfate was given at 5, 10 and 20 mg/kg IP. All doses increased dose dependently the occurrence latency of IS and PS. The amount of IS and PS was decreased for several hours, principally by a decrease of the number of phases. At 20 mg/kg the phase mean duration of IS and PS was also decreased. Consequently, IS and PS are similarly supported by muscarinic processes. The theta rhythm frequency was scored during IS and outside PS phasic motor activities (type 2 theta). At all doses it was significantly increased for hours. The theta rhythm frequency was also transiently increased during the hypersynchronization periods of PS (type 1 theta). At 20 mg/kg it was similarly the case for type 1 theta rhythm during waking.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02245333
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  • 112
    Electronic Resource
    Electronic Resource
    Investigations of fetal development models for prenatal drug exposure and schizophrenia. Prenatald-amphetamine effects upon early and late juvenile behavior in the rat (1994)
    Springer
    Psychopharmacology 116 (1994), S. 226-236 
    Details
    ISSN: 1432-2072
    Keywords: Fetus ; Prenatal drug exposure ; Schizophreniad-Amphetamine ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Recent evidence suggests that mid-pregnancy is a critical period for production of fetal abnormalities that cause behavioral and neuropathological changes in adult offspring. The present experiments provide an animal model of these effects by treating pregnant Sprague-Dawley rats during gestational days 11–14 withd-amphetamine (AM). Offspring were tested for neurological signs, foraging activity, reversal learning, and sensitivity to amphetamine challenge. In the Early Juvenile period, postnatal days (PND) 20–30, female AM offspring initially showed reductions in rearing, holepoking, and midfield activity. On later trials, and as young adults, AM females showed signs of locomotor hyperactivity despite continued poor foraging efficiency, and were also more sensitive to a 1.0 mg/kgd-amphetamine challenge. AM males showed initially slower and more perseverative responding than controls, but then developed excessive response switching. These changes continued during tests for Retention, Reversal, and Extinction in the Late Juvenile/Early Adult stage (PND 50–90), when both AM-exposed sexes showed increased eating time, significantly more perseverative lateral turning preference (right or left), and slower reversal learning than controls. Behavioral data were consistent with aberrations in thalamo-frontal and mesolimbic/nigrostriatal projection systems that have been reported in AM animals and which are also affected by maternal drug abuse and schizophrenia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02245066
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  • 113
    Electronic Resource
    Electronic Resource
    Chronic haloperidol treatment leads to an increase in the intramembrane interaction between adenosine A2 and dopamine D2 receptors in the neostriatum (1994)
    Springer
    Psychopharmacology 116 (1994), S. 279-284 
    Details
    ISSN: 1432-2072
    Keywords: Adenosine A2 receptor ; Dopamine D2 receptor ; Methylxanthine ; Tardive dyskinesias ; Receptor-receptor interaction ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Stimulation of adenosine A2 receptors (with the selective adenosine A2 agonist CGS 21680) in rat striatal membrane preparations, produces a decrease in both the affinity of D2 receptors and the transduction of the signal from the D2 receptor to the G protein. This intramembrane A2-D2 interaction might be responsible for the behavioural depressant effects of adenosine agonists and for the behavioural stimulant effects of adenosine antagonists such as caffeine and theophylline. Dopamine denervation induces an increase in the intramembrane A2-D2 interaction, which may underlie the observed higher sensitivity to the behavioural effects induced by adenosine antagonists found in these animals. The present study was designed to examine if chronic treatment with haloperidol, which also produces dopamine receptor supersensitivity, is also associated with an increase in the intramembrane A2-D2 interaction in the neostriatum and with a higher sensitivity to the behavioural effects induced by adenosine antagonists. The data showed that: (i) haloperidol pretreatment causes a higher binding of the D2 antagonist [3H] raclopride in striatal membrane preparations due to an increase in the number of D2 receptors without changes in their affinity for the antagonist (increase in Bmax without changes in kd); (ii) GCS 21680 decreases the affinity of dopamine for the D2 receptor, by increasing the equilibrium dissociation constants of high (Kh) and low affinity (K1) dopamine D2 binding sites and increases the proportion of high affinity binding sites (Rh); (iii) a low dose of CGS 21680 (3 nM), which is ineffective in membrane preparations from neostriatum of nontreated animals, is effective in membranes from the striatum of haloperidol-pretreated animals; (iv) the nonselective adenosine antagonist theophylline (20 mg/kg SC) causes a higher motor activation in rats pretreated with haloperidol. The possible relevance of these results for the pathophysiology and treatment of tardive dyskinesias is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02245329
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  • 114
    Electronic Resource
    Electronic Resource
    Adrenalectomy increases local cerebral blood flow in the rat hippocampus (1994)
    Springer
    Pflügers Archiv 426 (1994), S. 183-188 
    Details
    ISSN: 1432-2013
    Keywords: Hippocampus ; Corticosterone ; Adrenalectomy ; Local cerebral blood flow ; Diurnal rhythm ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The present study examined the effect of glucocorticoid manipulations on local cerebral blood flow in the hippocampus. We measured local cerebral blood flow in the hippocampus at 1-h intervals over a 1-day period in freely moving rats, by means of the H2 clearance method, before and after sham adrenalectomy, adrenalectomy or adrenalectomy with corticosterone replacement. We also measured local cerebral blood flow in the prefrontal cortex before and after adrenalectomy. Four weeks after the adrenalectomy, hippocampal blood flow at each time of day was an average of 47% greater than before the operation, showing diurnal variation as before. After the sham adrenalectomy or adrenalectomy with corticosterone replacement, hippocampal blood flow did not change significantly with respect to either its level or its diurnal variation. Local cerebral blood flow in the prefrontal cortex increased by only 19% after adrenalectomy. The present study demonstrates that adrenalectomy causes a remarkable increase in hippocampal blood flow, probably due to a lack of corticosterone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00374770
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  • 115
    Electronic Resource
    Electronic Resource
    Exercise-induced necrotic muscle damage and enzyme release in the four days following prolonged submaximal running in rats (1994)
    Springer
    Pflügers Archiv 428 (1994), S. 346-351 
    Details
    ISSN: 1432-2013
    Keywords: Skeletal muscle ; Muscle damage ; Treadmill running ; Serum ; Enzymes ; Water content ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Male Wistar rats were made to run uphill on a treadmill 5.5° incline at 17 m min−1 for 4 h, and killed for muscle and serum sampling 2, 4, 12, 24, 48 or 96 h after the exertion. To estimate the degree of muscle damage,β-glucuronidase activity, total protein concentration, water content and morphology were examined in the red parts of quadriceps femoris (MQF) and soleus (MS) muscles, the distal white part of the rectus femoris muscle (MRF) and the superficial part of triceps brachii muscle (MTB). Simultaneous serum samples were assayed for creatine kinase (CK) activity and carbonic anhydrase III (CA III) concentration. Fibre swelling and interstitial oedema were detected in MS at 4 h and in MQF at 12 h and typical histopathological changes, including inflammation and fibre necrosis, in both muscles 12–96 h post-exertion.β-Glucuronidase activity, a quantitative marker of muscle damage, was increased in MS at 4 h, in MQF at 24 h and in MRF 48 h after the running. No increase occurred in MTB. Water and protein content increased or decreased respectively, faster in MS (2 h post-exercise) than in MQF (12 h) or MRF (12 h). Water content thus contributed to muscle damage by preceding the increase inβ-glucuronidase activity. Serum CK activity was increased 2, 4, and 48 h after the running. Changes in serum CA III concentration were rather similar to those in CK but were not significant. The increase in serum CK was not in concert with the necrotic events in the muscle but occurred considerably earlier (2 h vs. 12–24 h post-exercise). The second peak in CK, 48 h post-exercise (during the necrotic phase), was smaller than the first one. Our results show that serum CK activity is an inaccurate estimate of exercise-induced muscle damage as regards interpretation of the degree and the time course of pathological events in the muscle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00724517
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  • 116
    Electronic Resource
    Electronic Resource
    An interaction between glucose and estrogen in gastric acid secretion in the lateral hypothalamic area of female rats (1994)
    Springer
    Experimental brain research 102 (1994), S. 171-174 
    Details
    ISSN: 1432-1106
    Keywords: Estrogen ; Gastric acid secretion ; Glucose ; Hypothalamus ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Gastric acid outputs caused by glucose injection into the lateral hypothalamic area (LHA) were examined in insulin hypoglycemia with or without estradiol-17β (EST) administration in bilaterally ovariectomized (OV) female rats. The basal level of acid output was higher in OV rats without EST than in OV rats with EST. When acid response was expressed as the percentage change, glucose injection into the LHA decreased acid output in a dose-dependent fashion in OV rats, while, in OV rats with EST, glucose injection into the LHA also reduced acid output without dose dependency. It was also noted that the threshold concentration of glucose that induced an acid response was lower in OV rats without EST than in OV rats with EST. These findings suggest that glucose-sensitive neurons responsible for gastric acid secretion can be modulated by estrogen at the LHA level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00232450
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    Subthreshold rectification in neostriatal spiny projection neurons (1994)
    Springer
    Experimental brain research 100 (1994), S. 239-249 
    Details
    ISSN: 1432-1106
    Keywords: Neostriatum ; In vitro brain slices Inward rectification ; Subthreshold ion conductances Firing pattern ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Intracellular recordings from slice preparations were used to assess the subthreshold electrophysiological behavior of rat neostriatal projection neurons. Both current steps and ramp currents were used to estimate the current-voltage relationship (I–V plot). Inward rectification in the subthreshold range was a characteristic of most neurons. The amount of rectification varied greatly, and it was complex: membrane voltage trajectories in response to ramps were made up by almost piecewise changes in the rate of voltage rise, suggesting that multiple conductances contribute to the subthreshold range. Inward current blockers such as tetrodotoxin (TTX) or Cd2+ decreased inward rectification, whereas outward current blockers such as tetraethylammonium (TEA) or 4-aminopyridine (4-AP) increased inward rectification. However, most inward rectification was due to TEA- and Cs+-sensitive conductances and not to TTX- or Cd2+-sensitive conductances. Cs+-sensitive conductances predominated at more negative membrane potentials, whereas 4-AP-sensitive conductances predominated at just ±10 mV below the firing threshold. In spite of a very slow activation, there was evidence for transient outward currents modulating the response, i.e., 4-AP-sensitivity, and voltage-sensitivity for firing frequency and threshold. TEA-sensitive conductances also contributed toward fixing the firing threshold. These results imply the contribution of various ion conductances on the shaping of the characteristic physiological firing recorded in vivo. Modulation of these responses by transmitters or peptides may help to understand neural processing in the neostriatum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227194
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  • 118
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    Re-initiated growth from mature ventral mesencephalon: an in oculo transplant study of nigrostriatal co-grafts (1994)
    Springer
    Experimental brain research 101 (1994), S. 73-85 
    Details
    ISSN: 1432-1106
    Keywords: Substantia nigra ; Striatum ; Transplant Dopamine ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The ability of mature dopaminergic neurons derived from ventral mesencephalon to re-initiate growth after making contact with a non-innervated target was studied using the intra-ocular grafting model. Foetal ventral mesencephalic tissue or brain stem including the locus coeruleus area was grafted to the anterior chamber of the eye. Two weeks, 6 weeks or 1 year after the first implantation, foetal striatal tissue was placed in contact with the nigral graft or grafted alone. The size of the transplants was measured through the cornea. The final size of the striatal grafts was significantly larger when placed alone than when co-grafted with 1-year-old or 6-week-old dopaminergic grafts. Striatum grafted together with 2-week-old nigra was larger than when grafted adjacent to mature substantia nigra, but not significantly so. Nerve fibre outgrowth into the iris from the nigral transplants did not increase after maturation, but the re-innervated area of the host iris progressively increased around the locus coeruleus grafts. Ingrowth of tyrosine hydroxylase (TH) immunoreactive nerve fibres into the striatal grafts was studied 6 weeks after the second implantation. TH immunohistochemistry revealed innervation of the striatal piece in all cases, except for the group where striatum alone was grafted. With the short survival time for cografts of 6 weeks, TH-positive nerve fibres innervated a larger volume, had a patchy appearance and the density was higher in striatum grafted to 2 week-old nigral transplants than that seen in striatal transplants grafted to mature nigral grafts. The patchy pattern of TH-immunoreactive nerve terminals was also seen in striatum co-grafted with 6-week-old or 1-year-old nigral transplants. No difference in striatal innervation volume was detected between those latter two groups. When striatum was implanted adjacent to mature ventral mesencephalon and grown together for 6 months — the longer survival time — the same dense TH-positive innervation as seen in striatum co-grafted with immature nigral tissue at the shorter survival time was found. Additionally, the nigral part of the co-grafts showed increased TH-immunoreactive nerve fibre density. In conclusion, dopaminergic neurites from mature ventral mesencephalic transplants can re-initiate growth if placed in contact with non-innervated striatal tissue. The nigral grafts do not progressively re-innervate the host iris, while locus coeruleus grafts do. The intra-ocular grafting model can be used to study the in vivo effects of trophic factors on mature dopaminergc neurons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00243218
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    Threshold-spacing in motoneurone pools of rat and cat: possible relevance for manner of force gradation (1994)
    Springer
    Experimental brain research 102 (1994), S. 69-74 
    Details
    ISSN: 1432-1106
    Keywords: Motoneurone ; Recruitment ; Force modulation ; Rat ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In the context of an analysis concerning factors of importance for the relative contributions of recruitment and rate gradation of muscle force, the distribution of electrical excitability was analyzed for medial gastrocnemius (MG) motoneurones of rat and cat. The experimental data came from previously collected intracellular measurements in animals anaesthetized with pentobarbitone. Electrical excitability was measured as the threshold (nanoamperes) for single spike generation (rheobase) in rat and for maintained repetitive firing (rhythmic threshold) in cat. Furthermore, the data included measurements of axonal conduction velocity and of contractile properties of the muscle units innervated by the studied motoneurones. The units were categorized into types S (slow-twitch, fatigue-resistant), FR (fast-twitch, fatigue-resistant) and FF (fast-twitch, fatiguable) on the basis of the combined criteria of twitch-speed and sensitivity to fatigue. We confirmed that, in spite of the presence of normal-looking symmetrical distributions of axonal conduction velocity, there was a positive skew in the distribution of electrical excitability (relatively high numbers of cells with low thresholds, few with high ones). Within each unit category (S, FR, FF), we ranked the motoneurones according to their relative electrical excitability and calculated the threshold difference between consecutive cells (“threshold spacing”). In accordance with the skewed distribution of electrical excitability, we found that the mean threshold spacing was ranked in the same way as the mean thresholds, i.e. S〈FR〈FF; the statistical analysis showed that, for cats as well as rats, small threshold-spacing steps were significantly more common for S than for FF motoneurones. In the discussion it is pointed out that the narrow threshold-spacing for S units, as compared to FF units, would tend to decrease the relative amount of recruitment-parallel rate modulation in these cells. Thus, the spacing of recruitment thresholds tends to allow the easily recruited S motoneurones to remain firing at relatively low rates during ongoing recruitment gradation, which would be of potential value in promoting a high degree of endurance for long-lasting postural contractions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00232439
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    Sensorimotor transformation in a spinal motor system (1994)
    Springer
    Experimental brain research 100 (1994), S. 170-174 
    Details
    ISSN: 1432-1106
    Keywords: Withdrawal reflexes ; Motion analysis Nociception ; Pain ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To use sensory information from the skin to guide motor behaviour the central nervous system must transform sensory coordinates into movement coordinates. As yet, the basic principles of this crucial neural computation are unclear. One motor system suitable as a model for the study of such transformations is the spinal withdrawal reflex system. The spatial organization of the cutaneous input to these reflexes has been characterized, and we now introduce a novel method of motion analysis permitting a quantitative analysis of the spatial input-output relationship in this motor system. For each muscle studied, a “mirror-image” relationship was found between the spatial distribution of reflex gain for cutaneous input and the pattern of cutaneous unloading ensuing on contraction. Thus, there is an “imprint” of the movement pattern on this motor system permitting effective sensorimotor transformation. This imprint may indicate the presence of a learning process which utilizes the sensory feedback ensuing on muscle contraction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227291
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    Expression of major histocompatibility complex class II antigen on amoeboid microglial cells in early postnatal rat brain following intraperitoneal injections of lipopolysaccharide (1994)
    Springer
    Experimental brain research 100 (1994), S. 287-292 
    Details
    ISSN: 1432-1106
    Keywords: Amoeboid microglia Major histocompatibility complex Type 3 complement receptor ; Endotoxin ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In rats given two single intraperitoneal injections of lipopolysaccharide (LPS) at 1 and 4 days of age and killed at 7 days of age, 11.5–12% of amoeboid microglial cells (AMC) in the supraventricular corpus callosum were induced to express major histocompatibility complex (MHC) class II antigen, as detected with monoclonal antibody OX-6. The MHC class II antigen induced was colocalized with MHC class I antigen and type 3 complement receptors on the same cells. The expression of MHC class II antigen on the plasma membrane of AMC was confirmed in immunoelectron microscopy. Although OX-6-positive AMC often assumed a perivascular position, the majority of them, however, were far removed from the blood vessels. The cytoplasmic processes of the perivascular OX-6-positive AMC appeared to rest directly on the vascular lamina, and in some section profiles they were in contact with a large surface area of the outer wall of small blood vessels. It is concluded from this study that although MHC class II antigen is not constitutively present on AMC, it is, however, inducible under stimulation with LPS. It is, therefore, suggested that the OX-6-positive AMC, especially the perivascular AMC, may have the potentiality to function as antigen-presenting cells in the developing brain when challenged by LPS.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227198
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    Lowering of extracellular pH suppresses low-Mg2+-induces seizures in combined entorhinal cortex-hippocampal slices (1994)
    Springer
    Experimental brain research 101 (1994), S. 44-52 
    Details
    ISSN: 1432-1106
    Keywords: Acidosis ; Seizures ; Brain slices ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Lowering [Mg2+]o induces epileptiform bursting in hippocampus and entorhinal cortex (EC), presumably by activation of N-methyl-d-aspartate (NMDA) receptors. Since increasing [H+]o has been shown to reduce NMDA receptor activation, we hypothesized that this could contribute to anticonvulsant actions of acidic pH. To test this, we studied the effects of raising extracellular PCO2 (20.6%, pH = 6.7) or lowering extracellular pH (6.7 or 6.2) on low-Mg2+-induced epileptiform discharges. Lowering the pH to 6.7 by either means increased the interval between seizure-like events (SLEs), decreased the maximal amplitude of SLEs, and, if the site of seizure generation was at a distance from the recording site, acidification slowed the rate of seizure propagation. In contrast, the duration of SLEs was unaffected by acidic pH or high PCO2. Raising PCO2 or lowering pH to 6.7 also blocked early (8–10 min) but not late (〉 20 min) phases of status-like discharges. All effects of the extracellular pH changes were fully reversible. Further lowering of extracellular pH to 6.2 completely and reversibly blocked both SLEs and status-like discharges. Our data show that the effects of high PCO2 and low pH on seizures in the EC in vitro may be dose-dependent and consistent with induction by proton blockade of NMDA receptors. Thus, blockade of NMDA currents by protons may be an important component of the anticonvulsant action of extracellular acidosis. The results also suggest that acidosis may be a desirable property for new antiepileptic treatments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00243215
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    Phosphinic acid derivatives as baclofen agonists and antagonists in the mammalian spinal cord: an in vivo study (1994)
    Springer
    Experimental brain research 101 (1994), S. 59-72 
    Details
    ISSN: 1432-1106
    Keywords: Spinal cord ; Synaptic transmission ; GABAB receptors ; Baclofen agonists and antagonists ; Rat ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The actions of a series of derivatives of 3-aminopropyl-phosphinic acid as baclofen agonists and antagonists have been examined on the synaptic excitation of neurones by impulses in primary afferent fibres in the lumbar spinal cords of pentobarbitone-anaesthetised cats and rats. Both the pre-and postsynaptic inhibitory actions of microelectrophoretic (-)-baclofen were reduced by similarly administered CGP 35 348, 36 742, 46 381, 52 432, 54 626 and 55 845, the latter being the most potent antagonist. None of these antagonists either decreased or increased the excitability of spinal neurones, and the inhibitory action of GABA was reduced only by local concentrations of antagonists which also reduced the action of piperidine-4-sulphonic acid, a GABAA agonist. Although the weak inhibitory effect of 3-aminopropylphosphinic acid in both the rat and the cat was not reduced by these baclofen antagonists, the pre-and postsynaptic inhibitory effects of 3-aminopropyl-methyl-osphinic acid (CGP 35 024), which was more potent than (-)-baclofen, were reduced by the antagonists. Like (-)-baclofen, CGP 35 024 was relatively ineffective in reducing transmitter release in the cord from the terminals of excitatory spinal interneurones, the terminals of excitatory tracts in the dorsolateral funiculus and the cholinergic terminals of motor axon collaterals. In both rat and cat cords, receptors for (-)-baclofen could not be demonstrated to be activated by microelectrophoretic GABA, possibly because of the predominantly dendritic location of GABAB receptors. Spinal pre-and postsynaptic baclofen receptors appeared to be pharmacologically similar but differed from those in the higher central nervous system of the rat, where 3-aminopropylphosphinic acid has been reported to be an effective baclofen agonist. The compounds tested, particularly CGP 55 845 and 46 381, will be of use in further investigations of the physiological relevance of baclofen receptors at central synapses where GABA may be the transmitter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00243217
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    Synaptic connectivity of serotonin graft efferents in the suprachiasmatic and supraoptic nuclei of the hypothalamus (1994)
    Springer
    Experimental brain research 101 (1994), S. 353-364 
    Details
    ISSN: 1432-1106
    Keywords: Transplantation ; Serotonin neurons ; Hypothalamus ; Electron microscopy ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We have previously reported that a cell suspension from the rostral part of the embryonic raphe grafted to the basal hypothalamus of 5,7-dihydroxytryptamine-denervated rats produced incomplete serotonin (5-HT) re-innervation of the suprachiasmatic nucleus (SCN) as opposed to hyper-innervation of the supraoptic nucleus (SON). We took advantage of this experimental model to investigate whether the graft-derived, 5-HT fibres retained normal ultrastructural features, and, particularly, a normal density of synaptic junctions, irrespective of the extent of target re-innervation. The intrinsic features of immunostained, graft-derived 5-HT axonal varicosities in both the SCN (ventral portion) and the SON were essentially similar to those exhibited by the respective endogenous innervation. Analysis of well-preserved varicosities in uninterrupted series of thin sections allowed us to evaluate directly the proportions of junctional to non-junctional 5-HT varicosities in both regions. Synaptic incidences were also remarkably conserved after grafting (45.5% in the SCN versus 38.5% in the SON; 48% and 38% in normal rats, respectively). Synapses were primarily reestablished on dendritic shafts, which also were identified as the major post-synaptic targets of the normal 5-HT innervations. We noted, however, a tendency toward increased numbers of symmetrical versus asymmetrical synapses in both the SCN and SON of grafted rats. Thus, irrespective of whether hypo-or hyper-innervation patterns developed post-grafting, the transplanted 5-HT neurons essentially retained normal ultrastructural features in their target territories, with a normal incidence of synaptic junctions. The data provide further support to the hypothesis that the innervation territory is the major determinant of the frequency with which ingrowing 5-HT fibres make synaptic junctions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227329
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  • 125
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    Ibotenic acid lesions of the striatum reduce drug-induced rotation in the 6-hydroxydopamine-lesioned rat (1994)
    Springer
    Experimental brain research 101 (1994), S. 365-374 
    Details
    ISSN: 1432-1106
    Keywords: 6-Hydroxydopamine ; Ibotenic acid ; Rotation ; Amphetamine ; Apomorphine ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Lesions of the dopaminergic nigrostriatal tract produce a range of motor and sensorimotor deficits. One of the simplest and most reliable is the rotational response of the animal following activation with drugs that stimulate the dopaminergic network, most notably amphetamine and apomorphine. Consequently, the rotation test has been extensively used in assessing the success of treatments designed to restore dopaminergic function, including neural transplants. The present study investigates whether rotation induced by 6-hydroxydopamine lesions of the nigrostriatal bundle in rats is modified by additional lesions in the neostriatum. It was found that apomorphine-induced rotation can be reduced by ibotenic acid lesions of the dopamine-deafferented striatum, and that the extent of the reduction was proportional to the size of the lesions. In contrast, such lesions produced a non-significant reduction in amphetamine-induced rotation, although the correlation between the extent of the reduction and the size of the lesion was again apparent. Since the pattern of change was similar in direction, albeit smaller in magnitude, than the previously reported effects of intrastriatal transplantation in rats with similar nigrostriatal lesions, rotation tests alone do not provide an unequivocal test of graft survival and function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227330
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    Metabolism of a glucuronide conjugate of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone in rats (1994)
    Springer
    Archives of toxicology 69 (1994), S. 14-17 
    Details
    ISSN: 1432-0738
    Keywords: Key words Tobacco-specific nitrosamine ; 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone ; [4-(Methylnitrosamino)-1-(3-pyridyl)but-1-yl]- β-O-d-glucosiduronic acid ; Rat ; Urine ; Metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Besides 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), [4-(methylnitrosamino)-1-(3-pyridyl)but-1-yl]-β-O-d-glucosiduronic acid (NNAL-Glu) is another important metabolite of the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) which has been detected in the urine of tobacco users and non-smokers heavily exposed to sidestream cigarette smoke. In order to evaluate the toxicological significance of NNAL-Glu formation and excretion, the metabolism of [5-3H]-NNAL-Glu was studied in rats. Five male F344 rats were administered 3.7 mg/kg [5-3H]-NNAL-Glu by i.v. injection and the metabolites in urine analysed by HPLC. More than 90% of the radioactivity was excreted in urine within the first 24 h. Unchanged NNAL-Glu accounted for 81.2±3.1% of the total radioactivity; the remaining part of the dose appears to be deconjugated resulting in the urinary excretion of NNAL (3.6±1.7%) and its α-hydroxylation (11.5±2.2%) and N-oxidation (3.6±1.6%) products. The presence of α-hydroxylation products of NNAL-Glu in urine suggests that this NNK metabolite may be activated in vivo to carcinogenic intermediates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002040050130
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    Messenger RNA levels of lung extracellular matrix proteins during ozone exposure (1994)
    Springer
    Lung 172 (1994), S. 15-30 
    Details
    ISSN: 1432-1750
    Keywords: Rat ; DNA ; mRNA ; Collagen ; Fibronectin ; c-myc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Continuous exposure of rats to ozone has been shown to result in lung epithelial damage, inflammation, and subsequent increases in collagen content. The main goal of this study was to identify the earliest time point of altered extracellular matrix protein gene expression by utilizing Northern blot analyses of rat lungs continuously exposed to 1.0 ppm ozone for 14 days. An early increase of steady-state fibronectin mRNA levels was observed at 2 days of exposure, prior to the time point of increased type I collagen mRNA, which was seen at 4 days. This increased level of type I collagen mRNA preceded measurable changes in total lung collagen content, observed at 7 days. In addition, peak levels of the growth-related proto-oncogene c-myc mRNA could be correlated with maximal increases of lung DNA content, although the initial increase in c-myc mRNA preceded measurable changes of total lung DNA. The use of specific cDNA probes for measuring altered gene expression can be useful for defining the early cellular and molecular events in ozone-induced lung injury.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00186166
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    High-resolution magnetic resonance imaging of arthritic pathology in the rat knee (1994)
    Springer
    Skeletal radiology 23 (1994), S. 429-437 
    Details
    ISSN: 1432-2161
    Keywords: Arthritis ; Rat ; Knee ; MRI ; X-radiography ; histology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract High-resolution magnetic resonance imaging (MRI) has been used to visualise the changes that occur in both soft tissue and bone during antigen-induced, monoarticular arthritis (AIMA) of the rat knee. Extensive optimisation studies were performed in order to minimise the time of the experiments and to maximise both the signal-to-noise ratio and the contrast in the MR images. The study was cross-sectional rather than longitudinal and at each of the 13 time points studied during the progression of the disease, corresponding X-radiographs and histological sections were obtained. Interpretation of the spin echo MR images was aided by the use of chemical shift-selective imaging, magnetisation transfer contrast and relaxation time experiments, as well as by correlation with the histology and X-radiography data. The MR images clearly show invasion of the synovium by an inflammatory pannus which spreads over the articular cartilage and invades the bone, leading to erosion and later remodelling. Two distinct types of bony erosion were observed: focal erosions, especially at the margins of the joint, and subchondral erosions. It is concluded that MRI provides a sensitive, non-invasive method for investigating both early-stage inflammatory changes and late-stage bony changes in the knee joints of the arthritic rat.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00204603
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    Prepulse inhibition of the acoustic startle response of rats is reduced by 6-hydroxydopamine lesions of the medial prefrontal cortex (1994)
    Springer
    Psychopharmacology 113 (1994), S. 487-492 
    Details
    ISSN: 1432-2072
    Keywords: Prefrontal cortex ; Dopamine ; Acoustic startle response ; Prepulse inhibition ; 6-Hydroxydopamine ; Rat ; Schizophrenia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Prepulse inhibition (PPI) of the acoustic startle response (ASR) is impaired by dopamine (DA) overactivity in the nucleus accumbens and anteromedial striatum. Since there is evidence that DA in the medial prefrontal cortex exerts an inhibitory control on striatal DA systems, it was investigated whether depletion of prefrontal DA reduces PPI. Rats were tested for PPI both before and after injections (2 × 1 µl per side) of vehicle, a low (3.0 µg/µl) or a high (6.0 µg/µl) dose of 6-hydroxydopamine hydrobromide (6-OHDA) into the prefrontal cortex. Only the high dose of 6-OHDA, leading to an 87% depletion of prefrontal DA, impaired PPI. The ability of an acoustic prepulse (75 dB, 10 kHz) to reduce the response to a startle pulse (100 dB noise burst) was maintained in sham lesioned rats, but was significantly disturbed in rats lesioned with the high dose of 6-OHDA. The 6-OHDA treatment did not affect the ASR amplitude in the absence of a prepulse. The reduction of PPI in lesioned rats correlated with the extent of DA depletion. These results suggest that the DA innervation of the prefrontal cortex is involved in the modulation of the ASR and they provide further evidence for opposite actions of prefrontal and subcortical DA systems in the control of behaviour. The present findings are discussed with regard to the potential role of prefrontal DA in schizophrenia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02245228
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    Effect of lesions of the ascending 5-hydroxytryptaminergic pathways on timing behaviour investigated with the fixed-interval peak procedure (1994)
    Springer
    Psychopharmacology 114 (1994), S. 463-468 
    Details
    ISSN: 1432-2072
    Keywords: 5-Hydroxytryptamine ; 5,7-Dihydroxytryptamine ; Operant behaviour ; Timing ; Fixed-interval peak procedure ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Twelve rats received injections of 5,7-dihydroxytryptamine into the dorsal and median raphe nuclei; 12 rats received sham lesions. The rats were then trained for 60 sessions under a discrete-trials fixed-interval schedule (peak procedure). In half the trials, a reinforcer became available 40 s after trial onset, and the trial was terminated upon reinforcer delivery; the remaining trials were 120 s in duration, and reinforcement did not occur in these trials. Performance during the 120-s trials was characterized by increasing response rate during the first 40 s of the trial, declining response rate between 40 s and 80 s, and a secondary increase in response rate during the final 40 s of the trial. The lesioned group showed a broader “spread” of the response rate function than the control group (time between attainment of 70% of the peak response rate and subsequent decline of response rate below this level); however, the peak response rate and the time from trial onset until attainment of the peak response rate did not differ significantly between the groups; the spread/peak-time ratio was significantly greater in the lesioned group than in the control group. The levels of 5-hydroxytryptamine (5HT) and 5-hydroxyindoleacetic acid in the parietal cortex, hippocampus, amygdala, nucleus accumbens and hypothalamus were markedly reduced in the lesioned group, but the levels of noradrenaline and dopamine were not significantly affected by the lesion. The results confirm the involvement of 5HTergic function in timing behaviour.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02249337
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    Crossmodal divided attention in rats: effects of chlordiazepoxide and scopolamine (1994)
    Springer
    Psychopharmacology 115 (1994), S. 213-220 
    Details
    ISSN: 1432-2072
    Keywords: Divided attention ; Scopolamine ; Chlordiazepoxide ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract “Divided attention” is a psychological construct that hinges on assumptions about a fixed finite capacity of subjects to simultaneously process multiple sets of information. A model of a crossmodal divided attention task was developed in rats. Initially, rats were trained consecutively in operant auditory and visual conditional discrimination tasks. The final task consisted of two successive blocks of 20 trials per modality (modality certainty), followed by 60 trials comprising a semi-randomized sequence of stimuli of both modalities (auditory or visual) and qualities (flashing/pulsing or constantly turned on; modality uncertainty). In comparison to unimodal blocks of trials, performance in the mixed condition was assumed to reflect the demands on the parallel processing of two sets of stimulus-response rules. While response accuracy remained unchanged, response latencies were generally longer in the bimodal condition. Administration of scopolamine (0.03, 0.06, 0.1 mg/kg) or chlordiazepoxide (1, 3, 5, 8 mg/kg) dose-dependently increased response latencies. The scopolamine-induced increase in response latencies was greater in the mixed condition. Cost-benefit analyses demonstrated that the absolute divided attention costs (in ms) were generally higher for visual than for auditory stimuli. Both drugs produced qualitatively similar effects; however, scopolamine was more potent in increasing the absolute divided attention costs than chlordiazepoxide. These data are discussed in terms of the validity of this animal paradigm, and of hypotheses about the effects of benzodiazepine receptor agonists and muscarinic antagonists on brain information processing capacity.
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    URL: http://dx.doi.org/10.1007/BF02244774
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    Diazepam impairs place learning in naive but not in maze-experienced rats in the Morris water maze (1994)
    Springer
    Psychopharmacology 115 (1994), S. 73-78 
    Details
    ISSN: 1432-2072
    Keywords: Benzodiazepines ; Diazepam ; Morris water maze ; Place learning ; Anxiety ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Anxiolytic benzodiazepines have been shown to impair place learning in the Morris water maze. However, a clear-cut demonstration of a direct and specific effect on mnemonic processes has not yet been offered. In the present study, the effects of diazepam on place navigation in the Morris water maze were studied in rats. Three conditions were examined: learning, reversal learning and learning after familiarisation of animals with the maze. In view of the anxiolytic and sedative properties of diazepam, appropriate doses of the drug, i.e. those that produced an anxiolytic effect but no major motor impairment, were initially selected in the water-lick conflict and rotarod tests, respectively. Doses of 2.5 and 5 mg/kg PO increased punished drinking in the water-lick conflict test without significantly decreasing rotarod performance. These doses were then used to assess the effects of diazepam on spatial behaviour. Diazepam, at both doses, impaired place learning in behaviourally naive rats. Such an effect appeared to be transient: diazepam-treated rats eventually reached control performance. Moreover, analysis of the probe trial at the end of training revealed adoption of a spatial strategy to locate the submerged platform. Neither reversal learning nor learning after familiarisation was affected. These results do not replicate previous findings in the Morris water maze and provide some evidence that the diazepam-induced place learning deficit may be primarily anxiolytic in nature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02244754
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    α2-adrenoceptor blockade, pituitary-adrenal hormones, and agonistic interactions in rats (1994)
    Springer
    Psychopharmacology 115 (1994), S. 478-484 
    Details
    ISSN: 1432-2072
    Keywords: Aggression ; α2 Adrenoceptors ; Catecholamines ; ACTH ; Corticosterone ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of adrenergic activation on aggressiveness and the aggression induced endocrine changes were tested in rats. α2 adrenoceptor blockers were used for enhancing activation of the adrenergic system, and changes in aggressiveness were tested in resident-intruder contests. Three experiments were conducted. In experiment 1, saline injected rats responded to the presence of an opponent by aggression and the increase in plasma ACTH and corticosterone. Intraperitoneal administration of 1 mg/kg CH-38083 (an α2 adrenoceptor antagonist) produced a several fold increase in clinch fighting and mutual upright scores, and also further enhanced the plasma ACTH and corticosterone response. In experiment 2, the effect of three doses (0.5, 1 and 2 mg/kg) of three different α2 adrenoceptor blockers CH-38083, idazoxan and yohimbine were tested. All the substances increased aggression at 0.5 and 1 mg/kg; at 2 mg/kg the effect of idazoxan and yohimbine disappeared, while with CH-38083 an additional increase was obtained. In yohimbine treated animals the enhancement of aggression was reduced already at 1 mg/kg. In experiment 3, indomethacin, a potent inhibitor of the catecholamine-induced ACTH release completely abolished the effects of the α2 adrenoceptor antagonist CH-38083: the intensity of agonistic interactions, as well as ACTH and corticosterone plasma concentrations, returned to control levels. The possible role of catecholamines and the stress hormones in the activation of aggression is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02245571
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    Effects of cocaine microinjections into the nucleus accumbens and medial prefrontal cortex on schedule-induced behaviour: comparison with systemic cocaine administration (1994)
    Springer
    Psychopharmacology 115 (1994), S. 375-382 
    Details
    ISSN: 1432-2072
    Keywords: Cocaine ; Schedule-induced polydipsia ; Drinking ; Locomotor activity ; Nucleus accumbens ; Medial prefrontal cortex ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of cocaine HCl infusions into either the nucleus accumbens (NACC) or medial prefrontal cortex (PFC) were compared on the performance of schedule-induced polydipsia (SIP) and related behaviours. Food-deprived rats were exposed to a fixed-time 60-s schedule of food delivery in daily 30-min sessions until stable levels of behaviour were obtained (14 days). Rats were then bilaterally infused with cocaine into either the NACC or PFC via chronically indwelling guide cannulae. Each subject received a sequence of five cocaine infusions (0, 12.5, 25, 50, 100 µg) according to a Latin Square design. For comparison, following these intracranial infusions each rat received a sequence of five IP injections of cocaine (0, 2.5, 5, 10, 20 mg/kg) also in a counterbalanced order. NACC and PFC infusions of cocaine and IP cocaine dose-dependently reduced SIP. Cocaine infusions into the NACC, but not the PFC, increased locomotor activity but the characteristic temporal profile of locomotor activity during SIP was retained. IP cocaine also increased locomotor activity in a dose-dependent manner, but the temporal profile of activity was flattened following 20 mg/kg cocaine. NACC and PFC infusions of cocaine had little effect on the total number of panel presses to gain access to the food pellets, but did slightly decrease the high rates of responding immediately prior to the pellet delivery. IP cocaine increased the total number of panel presses at the higher doses, mainly by increasing the low rates of responding. The effects of cocaine infusions into the PFC were behaviourally the most selective, as they reduced SIP without having substantial effects either on locomotor activity or panel pressing. These data therefore implicate a role for the PFC in the performance of SIP.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02245080
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    CCK-A and CCK-B selective receptor agonists and antagonists modulate olfactory recognition in male rats (1994)
    Springer
    Psychopharmacology 115 (1994), S. 435-440 
    Details
    ISSN: 1432-2072
    Keywords: Behaviour ; Olfactory recognition ; Social investigation ; Neuropeptides ; Cholecystokinin ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Modulation of learning and memory is one of the physiological roles that the neuropeptide cholecystokinin (CCK-8) may play. We have used a behavioural model of olfactory recognition among rats to test this hypothesis and to explore the relationship between CCK-A and CCK-B receptors and memory retention. Adult male rats form a transient memory of a juvenile congenere as indicated by a reduction in the duration of investigatory behaviour upon re-exposure 30 min after an initial exposure, but not when re-exposure is delayed until 120 min afterwards. In the present study, rats were treated after the first contact with various compounds; inhibition and facilitation of olfactory recognition were evaluated as the persistence in investigation 30 min and the decrease in investigation 120 min after pharmacological manipulations, respectively. Systemic injection of CCK-8, of a selective CCK-A agonist, or of non-peptide CCK-B antagonists (CI-988 and LY-262691) enhanced olfactory recognition. In contrast, the CCK-B selective agonist BC 264 and the tetrapeptide CCK-4 both disrupted it. Taken together with previous evidence of the detrimental effect of the non-peptide CCK-A antagonist devazepide on olfactory recognition, these results confirm and extend the hypothesis that there is a balance between CCK-A-mediated facilitative effects and CCK-B-mediated inhibitory effects on memory retention.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02245565
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    Parallel changes in dopamine D2 receptor binding in limbic forebrain associated with chronic mild stress-induced anhedonia and its reversal by imipramine (1994)
    Springer
    Psychopharmacology 115 (1994), S. 441-446 
    Details
    ISSN: 1432-2072
    Keywords: Chronic mild stress ; Imipramine ; Animal model of depression ; Dopamine ; D1-receptors ; D2-receptors ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Chronic sequential exposure to a variety of mild stressors has previously been found to cause an antidepressant-reversible decrease in the consumption of palatable sweet solutions, associated with abnormalities of dopaminergic neurotransmission in the nucleus accumbens. In the present study, 5 weeks of treatment with imipramine (10 mg/kg b.i.d.) reversed the decreased sucrose intake of rats exposed to chronic mild stress. Stress also caused a decrease in D2-receptor binding in the limbic forebrain (but not the striatum), which was completely reversed by imipramine. In nonstressed animals, imipramine decreased D1-receptor binding in both regions. However, in stressed animals, imipramine did not significantly alter D1-receptor binding in either area. Stress alone slightly increased D1-receptor binding, in striatum only. Scatchard analysis showed that all changes in receptor binding resulted from changes in receptor number (Bmax) rather than receptor affinity (KD). The results support the hypothesis that changes in D2-receptor function in the nucleus accumbens are responsible for chronic mild stress-induced anhedonia and its reversal by antidepressant drugs. They do not support the hypothesis that the sensitization of D2-receptors seen following chronic antidepressant treatment is caused by a down-regulation of D1-receptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02245566
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    Methamphetamine exposure during early postnatal development in rats: II. Hypoactivity and altered responses to pharmacological challenge (1994)
    Springer
    Psychopharmacology 114 (1994), S. 402-408 
    Details
    ISSN: 1432-2072
    Keywords: Methamphetamine ; Rat ; Postnatal development ; Hypoactivity ; Pharmacological challenge
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Methamphetamine induces neurotransmitter reductions and neurotoxicity at high doses in adult animals, but its effects on early brain development and behavior have received little attention. In this experiment the effects of methamphetamine exposure during a period equivalent to the human third trimester were examined. Rats (Sprague-Dawley CD) were injected subcutaneously withd-methamphetamine (d-MA) (30 mg/kg b.i.d.) early in postnatal development (days 1–10), later (postnatal days 11–20), or with water during both of these periods. Both early and later MA-exposed offspring exhibited reduced locomotor activity. The effect was most evident at 30 days of age and was smaller at 45 and 60 days and only present at these latter ages in males. Only the early MA exposure group showed prolonged suppression of activity in response to a challenge dose of fluoxetine and a persistant deficit in weight while only the later MA exposure group showed attenuated suppression of activity in response to a challenge dose of fluoxetine. Based both on the present data and those in the preceding article, it was concluded that the effects of MA are both long lasting and stage dependent and involve arousal as well as cognitive functions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02249329
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    5-HT1A receptor agonists improve the performance of normal and scopolamine-impaired rats in an operant delayed matching to position task (1994)
    Springer
    Psychopharmacology 116 (1994), S. 135-142 
    Details
    ISSN: 1432-2072
    Keywords: Short term memory ; Delayed matching to position ; 5-HT ; 5-HT1A receptor ; 8-OH DPAT ; Ipsapirone ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A series of experiments examined the effects of 5-HT1A ligands alone and in combination with the muscarinic antagonist scopolamine on short term working memory in the rat. The behavioural paradigm was a discrete trial, operant delayed matching to position task, with delays of 0, 5, 15 and 30 s. The 5-HT1A ligands tested were the full agonist, 8-OH DPAT (0, 0.1, 0.3 and 1 mg/kg), the partial agonist, ipsapirone (0, 1, 3 and 10 mg/kg), and the purported antagonist, NAN 190 (0, 1, 2, and 4 mg/kg). 1-PP (0, 0.1, 0.3, 1 mg/kg), the major metabolite of ipsapirone, was also tested. The lowest dose of 8-OH DPAT significantly improved matching accuracy at the longest delay, whereas the highest dose impaired matching accuracy and increased the latency to respond. Ipsapirone also significantly improved the accuracy of performance at a dose of 3 mg/kg, but the doses of 1 and 10 mg/kg did not significantly affect performance. NAN-190, at the highest dose tested (4 mg/kg), impaired matching accuracy, whereas the two lower doses did not significantly affect performance. The highest dose also increased the latency to respond. 1-PP had no effect on performance. Scopolamine HBr (0.14 mg/kg) caused a delay dependent impairment in matching accuracy, and had no effect on missed trials or the latency to respond. Low doses of 8-OH DPAT (0.1 and 0.3 mg/kg) significantly attenuated the scopolamine induced accuracy impairment, whereas 1 mg/kg 8-OH DPAT potentiated the impairment. Ipsapirone (3 mg/kg) also significantly improved the performance of scopolamine impaired rats. NAN-190 increased the latency to respond and reduced the number of nose pokes made during the delays in scopolamine-treated rats, and tended to potentiate the scopolamine-induced accuracy impairment. 1-PP did not affect the performance of scopolamine treated rats. Taken together, these results suggest that modulation of 5-HT1A receptors influences short term spatial working memory in the rat.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02245055
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    The neurosteroid pregnenolone sulfate blocks NMDA antagonist-induced deficits in a passive avoidance memory task (1994)
    Springer
    Psychopharmacology 116 (1994), S. 201-206 
    Details
    ISSN: 1432-2072
    Keywords: Neurosteroid ; Memory ; Amnesia ; NMDA receptor ; Ataxia ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The neurosteroid pregnenolone sulfate (PS) has been recently shown to positively modulate NMDA receptors and to have memory enhancing properties in mice. In the present study, we examined the ability of PS to increase retention performance and to reduce deficits induced by a competitive NMDA receptor antagonist, the 3-((±)-2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP), in a step-through passive avoidance task in rats. Pretraining administration of PS (0.84–1680 pmol, ICV) had minimal effects on retention performance assessed 24 h after training, while CPP significantly decreased retention performance at the doses of 1.2 and 1.6 nmol (ICV). However, when administered in combination with CPP (1.2 nmol), PS (0.84–840 pmol, ICV) dose-dependently blocked the deficit in passive avoidance response induced by the NMDA antagonist. At the dose of 840 nmol, PS also significantly reduced the motor impairment induced by CPP (1.2 nmol). The blockade of CPP-induced behavioral deficits by PS may result from its positive modulatory action at NMDA receptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02245063
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    Dissociation between brown adipose tissue thermogenesis and sympathetic activity in rats with high plasma levels of oestradiol (1994)
    Springer
    Pflügers Archiv 426 (1994), S. 40-43 
    Details
    ISSN: 1432-2013
    Keywords: Brown adipose tissue ; Cold-acclimation ; Noradrenaline turnover ; Oestradiol ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract It has been shown previously that high plasma levels of oestradiol inhibit brown adipose tissue thermogenesis. Since rats and mice show a close association between thermogenic activity in and sympathetic discharge to brown fat, we measured the noradrenaline turnover in rats with high plasma levels of oestradiol to establish whether the observed inhibition of thermogenic activity is brought about by a reduction in the sympathetic drive to brown adipocytes. Oestradiol-filled Silastic capsules were implanted subcutaneously in female rats previously acclimated either to thermoneutrality or to cold. Control rats received empty implants. After 15 days treatment, noradrenaline turnover was measured by blocking its synthesis with α-methyl-p-tyrosine. As expected, noradrenaline turnover was higher in cold-acclimated rats than in rats kept at thermoneutrality. The presence of high plasma oestradiol levels did not alter sympathetic activity in any of the treated groups despite reducing thermogenic activity. This result reveals that oestradiol dissociates the thermogenic activity of brown adipose tissue from its sympathetic activation. Such dissociation has never been previously reported in rats, although it seems to be common in Syrian hamsters. However the causative factor in this species is unknown.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00374668
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    Respiratory responses to combined hypoxia and hypothermia in rats after posterior hypothalamic lesions (1994)
    Springer
    Pflügers Archiv 426 (1994), S. 371-377 
    Details
    ISSN: 1432-2013
    Keywords: Body temperature ; Respiration ; Electrolytic lesions ; Urethrane anaesthesia ; Hypothalamus ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Urethane-anaesthetised rats were exposed to hypoxia (7% O2 in N2) for 5 min periods while body core temperature (T bc) was maintained within the normal range (37–38° C) using an abdominal heat exchanger. Animals were exposed to hypoxia and after placement of electrolytic lesions in either the anterior (n=6) or posterior hypothalamus (n=6). Neither lesion altered respiration while rats breathed air at either T bc. At normal T bc, rats responded to hypoxia with increased ventilation throughout the exposure period. This response was unchanged by lesions in either location. At reduced T bc rats responded to hypoxia with an initial increase in ventilation followed by depression to below air-breathing levels. This depressive response was unchanged after anterior hypothalamic lesions but eliminated after posterior hypothalamic lesions. It is concluded that neurons either originating in the posterior hypothalamus, or passing through it, play a role in the interaction between cold and hypoxia which leads to inhibition of respiration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00388299
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    Effects of methionine sulphoximine treatment on renal amino acid and ammonia metabolism in rats (1994)
    Springer
    Pflügers Archiv 427 (1994), S. 524-532 
    Details
    ISSN: 1432-2013
    Keywords: Glutamine synthetase ; Kidney ; Intestine ; Glutamine ; Ammonia ; Amino acids ; Metabolism ; Rat ; In vivo
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Renal glutamine metabolism in relation to ammoniagenesis has been extensively studied during chronic metabolic acidosis, when arterial glutamine levels are reduced. However, little is known about the effects of reduced glutamine delivery on renal glutamine and ammonia metabolism at physiological systemic pH values. Therefore, a model of decreased arterial glutamine concentrations at normal pH values was developed using methionine sulphoximine (MSO). Renal glutamine and ammonia metabolism was measured by determining fluxes and intracellular concentrations after an overnight fast in ether anaesthetized normal rats, MSO-treated rats and their pair-fed controls. Moreover, fluxes and intracellular concentrations of several other amino acids were determined concomitantly. After 2 and 4 days of MSO treatment, arterial glutamine concentrations were reduced to 55%, while arterial ammonia concentrations increased by 70%. Kidney glutamine uptake reduced, but systemic pH was unchanged. Fractional extraction of glutamine remained unchanged, suggesting that also in vivo net uptake of glutamine by the kidney at subnormal levels is related to arterial glutamine concentrations. As a result, at day 2 but not at day 4, the kidney reduced the net release of ammonia into the renal vein and thus reduced net renal ammonia addition to body ammonia pools. Therefore at day 2, the kidney seems to play an important role in adaptation to both hyperammonaemia and hypoglutaminaemia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00374270
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    Analysing ion channels with hidden Markov models (1994)
    Springer
    Pflügers Archiv 426 (1994), S. 328-332 
    Details
    ISSN: 1432-2013
    Keywords: Cortical collecting duct ; K+ channel ; Rat ; Isolated tubule ; Patch clamp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Ion channel current amplitudes (μ) and open probabilities (P o) have been analysed so far by defining a 50% threshold to distinguish between open and closed states of the channels. With this standard method (SM) it is very difficult or even impossible to analyse channels of different size in one membrane patch correctly. A stochastical model, named the hidden Markov model (HMM), separates between observation noise and the stochastic process of opening and closing of ion channels. The HMM allows the independent analysis of μ, P o, and mean dwell times (τ) of different channels in one membrane patch, without defining threshold levels. Using this method errors in the analysis are not summarized like in the SM because all different analysing procedures (e. g. filtering, setting of threshold, fitting processes) are done in one step. Two different K+ channels in excised basolateral membranes of the cortical collecting duct of rat (CCD) were analysed by the SM and the HMM. The μ value of the intermediate-conductance K+ channel (i-K+) was 3.9±0.1 pA (SM) and 3.8±0.2 pA (HMM) for 11 observations. The P o value of this channel was 10.2±4.2% (SM) and 10.1±4.0% (HMM). The mean τ values were 5.4±0.6 ms for the open state and 9.6±2.2 ms and 145±21 ms for the closed states (SM) and 7.8±1.1 ms, 7.7±0.9 ms and 148±24 ms (HMM), respectively. For seven small-conductance K+ (s-K+) channels, which were found in the same membrane patches as the i-K+, an accurate analysis of P o and τ was not possible with the SM. The μ value was 1.0±0.1 (SM), 0.9±0.1 (HMM) pA. P o was 16.6±4.6%, the open τ value was 11.1±2.8 ms, and the closed τ value was 34.9±8.5 ms. The HMM allows the analysis of single-channel currents, P o, and mean τ values when different or more than one ion channel(s) are colocalized in one membrane patch. Where analysis with the SM was possible results did not significantly differ from those obtained with the HMM. Thus for this kind of analysis the method of setting a 50% threshold appears justified.
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    URL: http://dx.doi.org/10.1007/BF00374789
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    Oxygen consumption of oestradiol-treated rats (1994)
    Springer
    Pflügers Archiv 426 (1994), S. 351-353 
    Details
    ISSN: 1432-2013
    Keywords: Rat ; Brown adipose tissue ; Noradrenaline responsiveness ; Oxygen consumption ; Cold acclimation ; Body temperature ; Oxidative capacity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Rectal temperature and oxygen consumption (üüO2) were monitored in female rats acclimated either to cold or to thermoneutrality and with and without chronic administration of oestradiol. The hormone is known to inactivate brown adipose tissue (BAT) and to reduce its response to noradrenaline (NA). The role of sympathetic control was studied by administering NA or the adrenergic blocker propranolol. Oestradiol treatment did not affect rectal temperature in the states of acclimation to thermoneutrality and to cold, nor did it change the hypothermic response of cold-exposed rats to temporary food deprivation. In the cold-acclimated rats, both controls and oestradiol-treated animals exhibited similar degrees of metabolic reduction after propranolol administration in the cold and similar degrees of metabolic activation by NA at thermoneutrality. Rats acclimated to thermoneutrality showed a larger metabolic response to NA when treated with oestradiol. The results suggest that oestradiol, while inactivating the BAT response to NA, activates the NA responsiveness of other metabolically active tissues in cold-induced thermogenesis. The observation of a greater oxidative capacity in the kidney and the rectus abdominis muscle of oestradiol-treated, cold-acclimated rats would be in line with this proposal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00374793
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    Alterations in the ontogeny of rat pup ultrasonic vocalization produced by prenatal exposure to nitrogen dioxide (1994)
    Springer
    Psychopharmacology 116 (1994), S. 423-427 
    Details
    ISSN: 1432-2072
    Keywords: Nitrogen dioxide ; Prenatal exposure ; Behavior ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Wistar female rats were exposed to low concentrations of nitrogen dioxide, NO2 (1.5 and 3 ppm) from day 0 to day 20 of pregnancy. The results show that prenatal exposure to this oxidant gas produced significant changes in the duration pattern of ultrasonic vocalizations emitted by male pups removed from their nest. In particular, a significant decrease in the length of ultrasonic calls was found in both 10- and 15-day-old rats exposed to NO2 (3 ppm) during gestation. These alterations were found at dose levels which did not significantly affect reproduction parameters, body weight gain and motor activity development. These findings suggest that gestational exposure to NO2, at concentrations below those associated with overt signs of toxicity, induces in rat offspring subtle behavioral changes characterized by altered ontogeny of ultrasonic emission.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02247472
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    Sex-dimorphic psychomotor activation after perinatal exposure to (−)-Δ9-tetrahydrocannabinol. An ontogenic study in wistar rats (1994)
    Springer
    Psychopharmacology 116 (1994), S. 414-422 
    Details
    ISSN: 1432-2072
    Keywords: Rat ; Development ; Δ-9-Tetrahydrocannabinol ; Motor behavior ; Locomotor activity ; Grooming ; Corticosterone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The ontogeny and the adult expression of motor behaviors were studied in male and female rats born from mothers exposed to Δ9-tetrahydrocannabinol (THC, 5 mg/kg) during gestation and lactation. Perinatal exposure to THC increased both rearing and locomotor activities in males and females at immature preweanling ages (P-15 and P-20). These effects disappeared after ceasing THC exposure (postweaning ages), but they were observed again in adult (P-70) females. The effects appeared as persistently high motor activity in familiar environments, disappearing the characteristic habituation profile in locomotor and exploratory behaviors. In novel environment condition tests, adult (P-70) THC-exposed females, but not males, exhibited lower locomotor activity in the socio-sexual approach test, and an increase in the emergence latency in the dark-light emergence test. Additionally, animals of both sexes exposed to THC showed a increase in the time spent grooming measured in novelty conditions. These findings suggest that perinatal exposure to THC affects both the development and the adult expression of motor behaviors and it resulted in a sex-dimorphic psychomotor activation very similar to that observed after perinatal exposure to other drugs of abuse. A possible role of THC-induced pituitary-adrenal (PA) axis activation was also evaluated by measuring plasma corticosterone levels in adult animals perinatally exposed: THC-exposed females exhibit a clear increase of this adrenal hormone, whereas THC-exposed males displayed lower levels of this hormone. These results confirm our previous finding of a sex-dimorphic behavioral response to perinatal exposure to hashish extracts, and they suggest a role of THC-induced PA activation in the mediation of these actions.
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    URL: http://dx.doi.org/10.1007/BF02247471
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    Ontogeny of behavioral sensitization in the rat: effects of direct and indirect dopamine agonists (1994)
    Springer
    Psychopharmacology 116 (1994), S. 483-490 
    Details
    ISSN: 1432-2072
    Keywords: Behavioral sensitization ; amphetamine ; NPA ; Ontogeny ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In the present study, the abilities of NPA (a direct DA receptor agonist) and amphetamine (an indirect DA receptor agonist) to induce short- and long-term behavioral sensitization were assessed in 11- and 17-day-old rats (age at initial injection). Rats were injected on 4 consecutive days with amphetamine (1.0, 2.5, or 5.0 mg/kg), NPA (1.0 mg/kg), or saline. A final test day occurred either 2 days (experiment 1) or 8 days (experiment 2) later. On the test day, rats given successive agonist injections received a single injection of the same agonist again; whereas rats given successive saline injections received either amphetamine or NPA for the first time. Five minutes after injection, locomotor activity (line-crosses), stereotyped sniffing, and vertical activity were measured during a 30-min testing session. The results showed that 11- and 17-day-old rats exhibited behavioral sensitization when tested with NPA or amphetamine after a 2-day interval. In contrast, neither NPA nor amphetamine was able to sensitize the behaviors of preweanling rats when measured 8 days after initial drug treatments. Therefore, these results show that both direct and indirect DA agonists are able to induce short-term behavioral sensitization in preweanling rats, but that the mechanisms responsible for mediating long-term behavioral sensitization have not yet matured.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02247482
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  • 148
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    Stress-induced changes in respiratory quotient, energy expenditure and locomotor activity in rats: effects of midazolam (1994)
    Springer
    Psychopharmacology 116 (1994), S. 475-482 
    Details
    ISSN: 1432-2072
    Keywords: Stress ; Anxiety ; Rat ; Metabolism ; Energy expenditure ; Energy substrate utilisation ; Respiratory quotient ; Midazolam ; FG-7142 ; RO 15-1788 ; Panic ; Hyperventilation ; Sympathetic nervous system ; Benzodiazepine ; Conditioned stimulus ; Respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Changes in O2 consumption, CO2 production and locomotor activity were examined in rats exposed to (1) brief footshock, (2) an aversive conditioned stimulus (CS) predicting footshock, or (3) the anxiogenic drug FG-7142. Respiratory quotient (RQ=CO2 produced/O2 consumed) and energy expenditure [EE=O2 consumed (364+113RQ)] were derived to give an estimate of the energy substrate (fat, carbohydrate or protein) being utilised and total substrate oxidation respectively. In experiment 1, footshock (4 × 5 s 0.6 mA shocks over 2 min) produced an immediate increase in RQ, EE and activity. The RQ and EE effects were attenuated by the benzodiazepine midazolam (1 mg/kg). In experiment 2, an aversive CS, consisting of flashing light and buzzer that had 24 h earlier been repeatedly paired with footshock (20 × 5 s 0.6 mA shocks) caused a pronounced drop in RQ, an increase in EE and locomotor activity suppression. The effects of the aversive CS on RQ and EE were reversed by midazolam (1 mg/kg). In experiment 3, FG-7142 (10 mg/kg) produced a steep drop in RQ that persisted for at least 2 h and which was reversed by midazolam (1 mg/kg) and delayed by the benzodiazepine antagonist RO 15-1788 (10 mg/kg). FG-7142 also tended to inhibit EE and locomotor activity, but these effects did not reach statistical significance. Overall, these data show that stress causes profound alterations in RQ, EE and activity and that the pattern of change in these parameters differs with the nature of the stressor involved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02247481
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  • 149
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    Kavapyrone enriched extract fromPiper methysticum as modulator of the GABA binding site in different regions of rat brain (1994)
    Springer
    Psychopharmacology 116 (1994), S. 469-474 
    Details
    ISSN: 1432-2072
    Keywords: Kavapyrone ; Piper methysticum ; GABA ; Rat ; Brain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Regional differences in the modulation of [3H] muscimol binding to GABAA receptor complexes by kavapyrones, compounds of the rhizome of the plantPiper methysticum which possess sedative activity, were demonstrated using membrane fractions obtained from target brain centers of kavapyrone action: hippocampus (HIP), amygdala (AMY) and medulla oblongata (MED), and from brain centers outside the main kavapyrone effects as frontal cortex (FC) and cerebellum (CER). The kava extract enhanced the binding of [3H] muscimol in a concentration-dependent manner with maximal potentiation of 358% over control in HIP followed by AMY and MED (main target brain centers). Minimal stimulation was observed in CER followed by FC. In contrast, apart from CER, the potency of kavapyrones was similar in the brain areas investigated with EC50 values ranging between 200 and 300 µM kavapyrones. Scatchard analysis revealed that the observed effects of kavapyrones were due to an increase in the number of binding sites (Bmax), rather than to a change in affinity. At a kavapyrone concentration of 500 µM the order of enhancement in Bmax was HIP=AMY〉MED〉FC〉CER. When kavapyrones are included together with pentobarbital or HPO the two classes of compounds produced a more than additive, i.e., synergetic effect on [3H] muscimol binding. Our findings suggest that one way kavapyrones might mediate sedative effects in vivo is through effects on GABAA receptor binding.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02247480
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  • 150
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    Excitatory amino acid receptors in the rostral ventrolateral medulla mediate hypertension induced by carotid body chemoreceptor stimulation (1994)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 349 (1994), S. 549-554 
    Details
    ISSN: 1432-1912
    Keywords: Kynurenate ; Excitatory amino acid receptor ; Vasopressin ; Chemoreceptor ; Vasopressin antagonist ; Rostral ventrolateral medulla ; Carotid body ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The rostral ventrolateral medulla (RVLM) is involved in the mediation of cardiovascular responses to peripheral chemoreceptor stimulation. To investigate whether excitatory amino acid inputs in the RVLM are related to the responses to chemoreceptor stimulation, we microinjected kynurenate, an amino acid antagonist, unilaterally into the RVLM and examined its effects on the pressor response to stimulation of carotid body chemoreceptors. Male Wistar rats were anesthetized with urethane, paralyzed and artificially ventilated. The carotid chemoreceptors were stimulated with isotonic solutions of inorganic phosphate solution. Stimulation of carotid body chemoreceptors produced increases in blood pressure. Kynurenate injected ipsilaterally but not contralaterally into the RVLM markedly inhibited the pressor response to chemoreceptor stimulation. In rats with spinal transection, stimulation of carotid body chemoreceptors also produced increases in blood pressure. The pressor response in rats with spinal transection was inhibited by intravenous injection of a vasopressin antagonist or by kynurenate injected ipsilaterally into the RVLM. Kynurenate injected into the RVLM inhibited the pressor response to NMDA, AMPA and kainate but not to acetylcholine in intact rats. These findings indicate that excitatory amino acid receptors are involved in mediating the pressor response to carotid body chemoreceptor stimulation in the rat RVLM. It appears that the chemoreceptor stimulation produces an increase in vasopressin release and the enhancement of vasopressin release is also mediated by an increase in excitatory amino acid inputs in the RVLM.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01258457
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  • 151
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    Halothane anesthesia enhances the effect of dopamine uptake inhibition on interstitial levels of striatal dopamine (1994)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 350 (1994), S. 239-244 
    Details
    ISSN: 1432-1912
    Keywords: Halothane ; Vanoxerine ; GBR 12909 ; d-Amphetamine ; Dopamine uptake ; Microdialysis ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The anesthetic, isoflurane, has been shown to potentiate the ability of the dopamine (DA)-uptake inhibitor, nomifensine, to increase the brain interstitial dopamine level ([DA]e). Since the effect of the more commenly used anesthetic, halothane, on this system is unknown, we determined [DA]e by microdialysis in the striatum of rats, conscious or anesthetized with halothane, in the presence of the more selective DA uptake inhibitor, vanoxerine (GBR 12909), or the DA releaser, d-amphetamine. Basal [DA]e was not changed by halothane. However, in halothane-anesthetized rats, the vanoxerine (3 mg/kg i.v.)-induced DA response increased severalfold compared to the response in conscious rats. The initial peak response to d-amphetamine (1 mg/kg i.v.) did not change, but the late response (1–3 h after injection) was augmented in anesthetized rats. Halothane is believed to increase firing of DA neurons in the substantia nigra and, hence, to release striatal DA. We hypothesize that [DA]e, is maintained at a normal level during the increased firing by equally increased activity of the DA transporter. However, when the DA transporter is blocked by vanoxerine, the increased DA release is unimpaired and [DA]e rises.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00175028
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  • 152
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    Convulsant action of a benzodiazepine receptor agonist/inverse agonist Ro 19-4603 in developing rats (1994)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 350 (1994), S. 393-397 
    Details
    ISSN: 1432-1912
    Keywords: Seizures ; Development ; Rat ; Benzodiazepine ; Inverse agonist
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract An inverse benzodiazepine receptor agonist Ro 19-4603, administered intraperitoneally, was found to induce two types of motor seizures, i.e. minimal, predominantly clonic and major, generalized tonic-clonic, in rats at all developmental stages studied (7, 12, 18 and 25 days old). The developmental profile of the two types of seizure was different. Minimal seizures could be induced easily in the two youngest groups, whereas there were no marked differences in the induction of major seizures between the age groups. A lethal outcome was more common in 18- and 25-day-old rats than in younger animals. The convulsant action of the benzodiazepine agonist/inverse agonist Ro 19-4603 shows only quantitative changes during post-natal development in the rat.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00178957
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  • 153
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    The AMPA antagonists NBQX and GYKI 52466 do not counteract neuroleptic-induced catalepsy (1994)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 349 (1994), S. 61-65 
    Details
    ISSN: 1432-1912
    Keywords: AMPA receptor ; NBQX ; GYKI 52466 ; Dizocilpine ; Quinpirole ; l-DOPA ; Catalepsy ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The AMPA antagonists NBQX (2.5, 5, 10 mg/kg) and GYKI 52466 (4.8, 8 mg/kg) were investigated in haloperidol (0.5 mg/kg)-induced catalepsy in the rat. The effects of AMPA antagonists administered either alone or in combination with the noncompetitive NMDA antagonist dizocilpine (0.02 mg/kg), with the dopamine D-2 agonist quinpirole (1 mg/kg) or with L-DOPA (50, 100 mg/kg plus benserazide) were tested. NBQX or GYKI 52466 did not exert anticataleptic effects, neither alone nor in combination with dizocilpine, quinpirole or l-DOPA. Thus, in the rat inhibition of AMPA receptors with NBQX or GYKI 52466 does not have effects predictive for an antiparkinsonian potential.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00178207
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  • 154
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    Expression of the α-subunit of glycoprotein hormones in the pars tuberalis-specific glandular cells in rat, mouse and guinea-pig (1994)
    Springer
    Cell & tissue research 278 (1994), S. 617-624 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Pituitary ; Pars tuberalis ; α-Subunit ; Immunocytochemistry ; In situ hybridization ; Rat ; Mouse ; Guinea-pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The nature of the hormone(s) secreted by the pars tuberalis (PT) is still unknown. This pituitary lobe is mainly formed by specific glandular cells that differ in their ultrastructural features from the other adenohypophysial cell types. Data from the literature indicate the presence of thyroid-stimulating hormone immunoreactivity in the PT-specific cells of the rat and the Djungarian hamster but not of other species, including the mouse and guinea-pig. The PT also encloses variable numbers of pars distalis cells, essentially gonadotrophs that are mainly dispersed in its caudal area. We studied the expression of the glycoprotein hormone α-subunit in the PT of the rat, mouse and guinea-pig by in situ hybridization and immunocytochemistry. In situ hybridization, using an oligonucleotide probe complementary to rat cDNA sequence 196–237 revealed the expression of the α-subunit gene throughout the PT of the rat and the mouse; in the guinea-pig, the probe labelled no pituitary cells. Light- and electron-microscopic immunocytochemistry demonstrated α-subunit immunoreactivity in the secretory granules of the PT-specific cells in the three species examined. These cells did not react with a specific antibody against the β-subunit of luteinizing hormone, an antibody that labelled scattered gonadotrophs. The present data suggest that hormone(s) produced by the PT-specific glandular cells are, at least partly, related to glycoprotein hormones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410050253
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  • 155
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    Expression of the α-subunit of glycoprotein hormones in the pars tuberalis-specific glandular cells in rat, mouse and guinea-pig (1994)
    Springer
    Cell & tissue research 278 (1994), S. 617-624 
    Details
    ISSN: 1432-0878
    Keywords: Pituitary ; Pars tuberalis ; α-Subunit ; Immunocytochemistry ; In situ hybridization ; Rat ; Mouse ; Guinea-pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The nature of the hormone(s) secreted by the pars tuberalis (PT) is still unknown. This pituitary lobe is mainly formed by specific glandular cells that differ in their ultrastructural features from the other adenohypophysial cell types. Data from the literature indicate the presence of thyroid-stimulating hormone immunoreactivity in the PT-specific cells of the rat and the Djungarian hamster but not of other species, including the mouse and guinea-pig. The PT also encloses variable numbers of pars distalis cells, essentially gonadotrophs that are mainly dispersed in its caudal area. We studied the expression of the glycoprotein hormone α-subunit in the PT of the rat, mouse and guinea-pig by in situ hybridization and immunocytochemistry. In situ hybridization, using an oligonucleotide probe complementary to rat cDNA sequence 196–237 revealed the expression of the α-subunit gene throughout the PT of the rat and the mouse; in the guinea-pig, the probe labelled no pituitary cells. Light-and electron-microscopic immunocytochemistry demonstrated α-subunit immunoreactivity in the secretory granules of the PT-specific cells in the three species examined. These cells did not react with a specific antibody against the β-subunit of luteinizing hormone, an antibody that labelled scattered gonadotrops. The present data suggest that hormone(s) produced by the PT-specific glandular cells are, at least partly, related to glycoprotein hormones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00331382
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  • 156
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    The immunolocalization of small nuclear ribonucleoprotein particles in testicular cells during the cycle of the seminiferous epithelium of the adult rat (1994)
    Springer
    Cell & tissue research 278 (1994), S. 363-378 
    Details
    ISSN: 1432-0878
    Keywords: Key words: snRNPs ; Testis ; Spermatocytes ; Spermatids ; Immunocytochemistry ; Chromatoid body ; Intermitochondrial nuage ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The objective of this study was to determine the cellular and subcellular distribution of small nuclear ribonucleoprotein particles (snRNPs) in the adult rat testis in relation to the different cell types at the various stages of the cycle of the seminiferous epithelium. The distribution of snRNPs in the nucleus and cytoplasm of germ cells was quantitated in an attempt to correlate RNA processing with morphological and functional changes occurring during the development of these cells. Light-microscopic immunoperoxidase staining of rat testes with polyclonal anti-Sm and monoclonal anti-Y12 antibodies localized spliceosome snRNPs in the nuclei and cytoplasm of germ cells up to step 10 spermatids. Nuclear staining was intense in Sertoli cells, spermatogonia, spermatocytes, and in the early steps of round spermatid development. Although comparatively weaker, cytoplasmic staining for snRNPs was strongest in mid and late pachytene spermatocytes and early round spermatids. Quantitative electron-microscopic immunogold labeling of Lowicryl embedded testicular sections confirmed the light-microscopic observations but additionally showed that the snRNP content peaked in the cytoplasm of mid-pachytene spermatocytes and in the nuclei of late pachytene spermatocytes. The immunogold label tended to aggregate into distinct loci over the nuclear chromatin. The chromatoid body of spermatids and spermatocytes and the finely granular material in the interstices of mitochondrial aggregates of spermatocytes were found to be additional sites of snRNP localization and were intensely labeled. This colocalization suggests that these dense cytoplasmic structures may be functionally related. Anti-U1 snRNP antibodies applied to frozen sections showed the same LM localization pattern as spliceosome snRNPs. Anti-U3 snRNP antibodies applied to frozen sections stained nucleoli of germ cells where pre-rRNA is spliced.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00414179
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  • 157
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    Selective association of nerve fibres immunoreactive for substance P or bombesin with putative cholinergic neurons of the male rat major pelvic ganglion (1994)
    Springer
    Cell & tissue research 278 (1994), S. 589-594 
    Details
    ISSN: 1432-0878
    Keywords: Autonomic ganglia ; Neuropeptides ; Pelvic plexus ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The male rat major pelvic ganglion contains both sympathetic and parasympathetic neurons that supply the lower urinary and digestive tracts, and the reproductive organs. The aim of this study was to describe the distribution and identify potential targets of sensory and intestinofugal axons in this ganglion. Two putative markers of these projections were chosen, substance P for primary sensory axons and bombesin for myenteric intestinofugal projections. Varicose substance P-immunoreactive axons were associated only with non-noradrenergic (putative cholinergic) somata, and most commonly with those that contained vasoactive intestinal peptide. Immunoreactivity for substance P was also present in a small group of non-noradrenergic somata, many of which were immunoreactive for enkephalins, neuropeptide Y or vasoactive intestinal peptide. Bombesin immunoreactivity was found only in preterminal and terminal (varicose) axons, the latter of which were exclusively associated with non-noradrenergic somata that contain neuropeptide Y-immunoreactivity. Some varicose axons containing either substance P-or bombesin-immunoreactivity were intermingled with clumps of small, intensely fluorescent cells. These studies indicate that substance P-and bombesin-immunoreactive axons are likely to connect with numerically small, but discrete, populations of pelvic neurons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00331378
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  • 158
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    Zona glomerulosa of the adrenal gland in a transgenic strain of rat: a morphologic and functional study (1994)
    Springer
    Cell & tissue research 278 (1994), S. 21-28 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Adrenal cortex ; Renin-angiotensin system ; Steroidogenesis ; Electron microscopy ; Morphometry ; Rat ; transgenic (mRen2) 27
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Transgenic rats for the murine Ren-2 gene display high blood pressure, low circulating levels of angiotensin II, and high renin content in the adrenal glands. Moreover, transgenic rats possess an increased aldosterone secretion (maximal from 6 to 18 weeks of age), paralleling the development of hypertension. To investigate further the cytophysiology of the adrenal glands of this strain of rats, we performed a combined morphometric and functional study of the zona glomerulosa of 10-week-old female transgenic rats. Morphometry did not reveal notable differences between zona glomerulosa cells of transgenic and age- and sex-matched Sprague-Dawley rats, with the exception of a marked accumulation of lipid droplets, in which cholesterol and cholesterol esters are stored. The volume of the lipid-droplet compartment underwent a significant decrease when transgenic rats were previously injected with angiotensin II or ACTH. Dispersed zona glomerulosa cells of transgenic rats showed a significantly higher basal aldosterone secretion, but their response to angiotensin II and ACTH was similar to that of Sprague-Dawley animals. Angiotensin II-receptor number and affinity were not dissimilar in zona glomerulosa cells of transgenic and Sprague-Dawley rats. These data suggest that the sustained stimulation of the adrenal renin-angiotensin system in transgenic animals causes an increase in the accumulation in zona glomerulosa cells of cholesterol available for steroidogenesis, as indicated by the expanded volume of the lipid-droplet compartment and the elevated basal steroidogenesis. However, the basal hyperfunction of the zona glomerulosa in transgenic animals does not appear to be coupled with an enhanced responsivity to its main secretagogues, at least in terms of aldosterone secretion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00305774
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  • 159
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    The immunolocalization of small nuclear ribonucleoprotein particles in testicular cells during the cycle of the seminiferous epithelium of the adult rat (1994)
    Springer
    Cell & tissue research 278 (1994), S. 363-378 
    Details
    ISSN: 1432-0878
    Keywords: snRNPs ; Testis ; Spermatocytes ; Spermatids ; Immunocytochemistry ; Chromatoid body ; Intermitochondrial nuage ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The objective of this study was to determine the cellular and subcellular distribution of small nuclear ribonucleoprotein particles (snRNPs) in the adult rat testis in relation to the different cell types at the various stages of the cycle of the seminiferous epithelium. The distribution of snRNPs in the nucleus and cytoplasm of germ cells was quantitated in an attempt to correlate RNA processing with morphological and functional changes occurring during the development of these cells. Light-microscopic immunoperoxidase staining of rat testes with polyclonal anti-Sm and monoclonal anti-Y12 antibodies localized spliceosome snRNPs in the nuclei and cytoplasm of germ cells up to step 10 spermatids. Nuclear staining was intense in Sertoli cells, spermatogonia, spermatocytes, and in the early steps of round spermatid development. Although comparatively weaker, cytoplasmic staining for snRNPs was strongest in mid and late pachytene spermatocytes and early round spermatids. Quantitative electron-microscopic immunogold labeling of Lowicryl embedded testicular sections confirmed the light-microscopic observations but additionally showed that the snRNP content peaked in the cytoplasm of midpachytene spermatocytes and in the nuclei of late pachytene spermatocytes. The immunogold label tended to aggregate into distinct loci over the nuclear chromatin. The chromatoid body of spermatids and spermatocytes and the finely granular material in the interstices of mitochondrial aggregates of spermatocytes were found to be additional sites of snRNP localization and were intensely labeled. This colocalization suggests that these dense cytoplasmic structures may be functionally related. Anti-U1 snRNP antibodies applied to frozen sections showed the same LM localization pattern as spliceosome snRNPs. Anti-U3 snRNP antibodies applied to frozen sections stained nucleoli of germ cells where pre-rRNA is spliced.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00414179
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  • 160
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    Changes in fibre-type composition and myosin heavy-chain IId isoform in rat soleus muscle during recovery period after hindlimb suspension (1994)
    Springer
    European journal of applied physiology 68 (1994), S. 102-106 
    Details
    ISSN: 1439-6327
    Keywords: Hindlimb suspension ; Recovery ; Soleus muscle ; Fibre-type composition ; Myosin heavy-chain IId isoform ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We examined the changes in myosin heavy-chain (HC) isoforms and fibre-type composition in rat soleus muscle using both myosin adenosine triphosphatase staining and sodium dodecyl sulphate/polyacrylamide gel electrophoresis (SDS-PAGE) analyses during the recovery period after 4 weeks of hindlimb suspension. Although there was no change in type IIc fibres after the suspension, an increase in this type of fibres was observed during the 1- to 4-week recovery period. The increase in type Ilc fibres was considered to be due to a shift from type Ila to IIc fibres. The SDS-PAGE analysis revealed the presence of the HC IId isoform, which was not observed in the control muscle, after a 4-week hindlimb suspension. The HC IId isoform gradually decreased over 3 weeks of recovery and disappeared in the 4th week of recovery after the suspension. These results suggest that the hypogravity conditions induced by hindlimb suspension stimulated the synthesis of the HC IId isoform, whereas an increase in mechanical load to the muscle accelerated the degradation of the HC IId isoform and the synthesis of type Ilc fibres during the recovery period after hindlimb suspension.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00599249
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  • 161
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    Muscle glycogen repletion and pre-exercise glycogen content: effect of carbohydrate loading in rats previously fed a high fat diet (1994)
    Springer
    European journal of applied physiology 68 (1994), S. 483-488 
    Details
    ISSN: 1439-6327
    Keywords: Carbohydrate loading ; Glycogen utilization ; Glycogen repletion ; Glycogen synthase ; Muscle ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We have recently reported that rates of muscle glycogen repletion during the early period of recovery were increased by carbohydrate (CHO) loading in rats previously fed a high fat diet. However, the reason for this remained unanswered. The purpose of this study was to examine whether an increase of glycogen utilization due to an elevated pre-exercise glycogen store would enhance rates of glycogen repletion in muscle. Despite an equal degree of glycogen depletion, the rates of glycogen repletion of soleus, red and white gastrocnemius muscles by postexercise administration of glucose (3.0 g · kg−1 body mass) and citrate (0.5 g · kg−1 body mass) were faster in the CHO loaded (3 days) rats than in the nonloaded rats, as a result of elevated pre-exercise glycogen content and consequently the greater glycogen utilization. The higher rate of muscle glycogen repletion may in part be explained by increased postexercise glycogen synthase activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00599517
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  • 162
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    Protein synthesis in the hippocampal slice: Transient inhibition by glutamate and lasting inhibition by ischemia (1994)
    Springer
    Metabolic brain disease 9 (1994), S. 235-247 
    Details
    ISSN: 1573-7365
    Keywords: Hippocampus ; Slices ; Protein synthesis ; Ischemia ; Glutamate ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Protein synthesis was measured in hippocampal slices which were exposed to glutamate (1 mM or 10 mM) or which were deprived of glucose and oxygen (‘in vitro ischemia’) for 15 min. Glutamate at 1 mM, a concentration estimated to occur duringin vivo ischemia did not affect protein synthesis. Ten mM glutamate inhibited protein synthesis immediately after exposure (50% of control values) and reduced ATP levels to about 30% of the control. After two hours, slices fully recovered their protein synthesis and energy metabolism. The effect of 10 mM glutamate was not receptor-mediated, as NMDA, AMPA, or metabotropic receptor antagonists failed to block the glutamate effect. Immediately after ischemia, protein synthesis was reduced to 30% of control values, and 2 hours later it was still depressed to one-half of control values. Energy charge, however, recovered completely. Ischemic inhibition of protein synthesis was not reversed by glutamate receptor antagonists. The data indicate that inhibition of protein synthesis in hippocampal slices during ischemia is not glutamate-dependent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01991197
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  • 163
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    Experimental oxygen-induced retinal detachment in the newborn Wistar rat (1994)
    Springer
    Documenta ophthalmologica 87 (1994), S. 315-329 
    Details
    ISSN: 1573-2622
    Keywords: Experimental retinal detachment ; Glial fibrillary acidic protein ; Müller cells ; Oxygen ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We conducted an extensive histological study of the retinas of newborn rats that had been exposed to hyperoxic conditions. Our aim was to verify whether it is possible, using oxygen alone, to induce retinal detachment, a lesion that is characteristic of the more advanced stages of retinopathy of prematurity (ROP). Eight litters (total number of animals: 64) of newborn, albino Wistar rats were used. Four litters (32 rats) were exposed to 80% oxygen for the first ten days of life. Some of these rats were then removed to room-air environments where they were kept for two, three or four more weeks. The other four litters (32 rats) were maintained for the entire period in room-air. On the 11th, 25th, 32nd and 39th days of life rats from both the exposed and control groups were sacrificed and 5 micron sections of their in toto eyeballs were submitted to histological evaluation and immunohistochemical studies. Folding of the internal retinal layers was observed in some of the animals exposed to hyperoxia, as well as those kept in room air. These folds did not alter the overall thickness of the retina itself and were probably congenital. Retinal folds and microdetachments were seen in many of the retinas from the exposed group of rats. Extensive detachment was observed in one of the rats sacrificed after two weeks of room-air recovery, in two of those recovered for three weeks and in two exposed to four weeks of room air. The sections containing these areas of retinal detachment showed marked increases in glial fibrillary acidic protein (GFAP) in immunocytochemical studies, suggesting that Müller cells might play a role in the pathogenesis of retinal detachment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01203341
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  • 164
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    Microvascular transfers of serratus anterior muscles in rats (1994)
    Springer
    European journal of plastic surgery 17 (1994), S. 1-4 
    Details
    ISSN: 1435-0130
    Keywords: Rat ; Free flaps ; Serratus anterior ; Microvascular surgery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The serratus anterior muscle in the rat is supplied by the serratus division of thoracodorsal vessels, in a pattern similar to man [2]. The serratus anterior muscles were transferred to the groin area as a free muscle flap in 17 rats and as a free muscle graft in 13 rats. In the free muscle flap group, the serratus anterior muscles of 8 of 10 rats survived; histological examination showed them to be viable and the vascular anastomoses were patent at the 30th day. In the free muscle graft group, all of the muscle grafts became necrotic. As a result, it is concluded that the microvascular transfer of serratus anterior muscles in rats is a useful small animal model for microsurgical laboratory training of clinical free flap transfers and also for performing pharmacological and biochemical studies in transplanted muscle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00176491
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  • 165
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    Image formation of alkyl-pendent aromatic polyimide by photocoupling with aromatic ketones (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 214 (1994), S. 57-65 
    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: Positive und negative Photostrukturen wurden in einem Polyimid (PI) aus 4,4′-Biphthalsäureanhydrid (BPA) und 4,4′-Diamino-3,3′-dimethyldiphenylmethan (DADMDPM), PI(BPA/DADMDPM) erzeugt, nachdem dieses mit Michlers Keton (MK) bzw. Benzophenon (BP) dotiert und einer ultravioletten Strahlung von 400 ± 50 nm ausgesetzt und naß entwickelt wurde. Das Prinzip der positiven Abbildung basiert auf dem Photokupplungseffekt von MK mit PI, der die Löslichkeit des Polyimids erhöht und so die Entwicklung eines Positivmusters ermöglicht. Die Erzeugung negativer Muster wird durch intermakromolekulare Wasserstoffbrücken zwischen der Carbonylgruppe des Imid-Rings und der Hydroxygruppe, die bei der photoinduzierten Kupplung von Benzophenon mit dem Polyimid gebildet wird, bewirkt. Die lithographische Auswertung zeigt, daß der mit MK dotierte, positive Polyimidfilm nicht in der Lage ist, brauchbare Muster zu erzeugen, da die UV-Wellenlängen von MK absorbiert werden, wodurch die Photokupplung in den tieferen Schichten des Films verhindert wird. Andererseits können in dem 0,6 μm dicken, mit Benzophenon dotierten Polyimidfilm sogar 2 μm schmale Linien aufgelöst werden.
    Notes: Positive and negative photostructures are formed after the polyimide (PI) of 4,4′-biphthalic anhydride (BPA) and 4,4′-diamino-3,3′-dimethyldiphenylmethane (DADMDPM), PI(BPA/DADMDPM) is doped with Michler′s ketone (MK) and benzophenone (BP), respectively, and is subjected to UV light (400 ± 50 nm) irradiation and solvent development. The principle of positive feature formation is based on the photocoupling of MK with PI, which increases PI solubility and thus enables a positive pattern to be developed. The phenomenon of negative photopatterning results from intermacromolecular H-bonding between the carbonyl group of the imide ring and the hydroxy group which is formed in the photoinduced coupling reaction between BP and PI. Lithographic evaluation shows that the MK-doped positive-acting PI film cannot form useful patterns because UV wavelengths are strongly absorbed by MK, which limits the depth of photocoupling in the film. On the other hand, 2-μm-wide lines can be resolved in the BP-doped negative-acting 0.6-μm-thick PI film.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052140106
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  • 166
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    Blends of polyamide 6 and poly(etheraroylhydrazide)s prepared concurrently with polyhydrazide polymerization (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 214 (1994), S. 101-113 
    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: Polyhydrazid/Polyamid-Blends (PEHZ12/PA6) wurden durch Niedrigtemperatur-Polykondensation von 4,4′-Dichlorformyl-α,ω-diphenoxydodecan und Terephthaloyldihydrazid (TDH) zu Poly(etheraroylhydrazid) in Gegenwart von Polyamid 6 synthetisiert. Die DSC-Analysen lassen vermuten, daß die zwei Polymerkomponenten nicht wechselwirken. Bei der Extraktion des PA6-Anteils der Blends mit Ameisensäure zeigt die Charakterisierung des PEHZ12-Extraktionsrückstands aber, daß zumindest bei bestimmten Zusammensetzungen Wechselwirkungen zwischen den Komponenten auftreten. Modellreaktionen erlauben die Annahme, daß die PEHZ12-Polymerisation zwischen den Amino-Endgruppen des PA6 und den wachsenden PEHZ12-Polymerketten abläuft.
    Notes: Poly(etheraroylhydrazide) is synthesized in the presence of PA6 by means of low-temperature condensation polymerization of 4,4′-dichloroformyl-α,ω-diphenoxydodecane with terephthaloyl dihydrazide (TDH) in order to prepare polyhydrazide/poly-amide 6 (PEHZ12/PA6) blends. The thermal analysis of the blends by DSC seems to indicate that the two polymers are not interacting. Nevertheless, when the blends are subjected to an extraction process with formic acid in order to remove the PA6, the characterization of the residual PEHZ12 reveales that some interactions do occur between the constituent polymers, at least for selected compositions. Model experiments permit to hypothesize that the polymerization of PEHZ12 proceeds with a chemical interaction between amino end groups of PA6 and growing PEHZ12 chains.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052140110
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  • 167
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    Die kristallisation von polybutylenterephthalat (PBT) und polycarbonat (PC) im polymerblend PBT/PC (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 214 (1994), S. 179-196 
    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 crystallization behavior of PBT as well as PC is changed in the controlled-processed blend due to intermolecular interactions between the different macromolecules in molten state.If the kinetics of the crystallization process prevents a crystallization-induced separation, the partial miscibility of the amorphous phases, measured by the glass transition temperatures, will lead to a decrease of the crystallinity of PBT. The crystallinity, normalized to the concentration of PBT in the blend, is independent from the concentration of PC at low coolling rates.At high cooling rates, PBT is crystallizing stepwise in the blend PBT/PC 40/60 wt.-%. The crystallization temperature in the anisothermic crystallization process is increased at low contents of PC due to a changed nucleation mechanism. The half-time of crystallization is increasing in blends with an increasing PC-content in isothermic crystallization experiments.The normally amorphous PC crystallizes considerably fast in presence of PBT in PC-rich blends. The crystallization or change in the state of order of PC was measured in situ by X-ray diffraction. Calorimetric experiments confirm this result and allow a quantitative estimation of the PC-crystallinity, which amounts to some 20% in the blend PBT/PC 5/95 wt.-%.
    Notes: Das Kristallisationsverhalten sowohl von PBT als auch von PC ist im definiert verarbeiteten Blend infolge intermolekularer Wechselwirkungen zwischen den unterschiedlichen Molekülen in der Schmelze verändert.Die über die Glasübergangstemperaturen gemessene teilweise Mischbarkeit der amorphen Phasen führt bei PBT zu einer Erniedrigung des Kristallinitätsgrades, wenn die kinetischen Bedingungen des Kristallisationsprozesses keine kristallisationsbedingte Entmischung zulassen. Der auf den PBT-Anteil normierte Kristallinitätsgrad ist bei kleinen Abkühlgeschwindigkeiten vom PC-Anteil unabhängüg.In der Mischung PBT/PC 40/60 Gew.-% kommt es bei hohen Kühlraten zu einer fraktionierten Kristallisation. Die Kristallisationstemperatur bei anisothermer Kristallisation ist bei geringen PC-Gehalten durch Änderung des Keimbildungsmechanismus erhöht. Bei isothermer Kristallisation steigt mit zunehmendem PC-Anteil die Kristallisationshalbwertszeit des PBT an.Das normalerweise amorphe PC kann in Gegenwart von PBT in den PC-reichen Mischungen besonders schnell kristallisieren, wobei der Kristallisations- bzw. Ordnungsprozeß des PC in situ mittels der Röntgenbeugung gemessen wurde. Kalorimetrische Untersuchungen bestätigen dieses Ergebnis und erlauben eine quantitative Abschätzung des PC-Kristallinitätsgrades zu ca. 20% im Blend PBT/PC 5/95 Gew.-%.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052140116
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  • 168
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    Photoreactions in halogen-containing negative-tone novolac resists (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 214 (1994), S. 197-210 
    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: Elementaranalytische sowie NMR-, IR- und UV-spektroskopische Untersuchungen zeigen, daß die Photolyse von Halogenphenolnovolaken zur Substitution der Halogenatome durch Wasserstoff, der Bildung chinoider Gruppen und intermolekularen Vernetzung führt. Die Geschwindigkeit der Halogeneliminierung hängt von der Art des Halogens ab. Sie steigt in der Reihenfolge F 〈 Cl 〈 Br 〈 I. Die Chloreliminierung aus der 4-Position ist gegenüber der aus der 2- und 3-Position begünstigt. Außerdem verläuft die Abspaltung para-ständiger Chloratome aus Dimeren schneller als aus Trioder Tetrameren. ESR-Messungen bei 77 K sowie die Laserblitzphotolyse bei 296 K deuten auf die intermediäre Bildung von Phenoxyl- und Arylradikalen. Lithographische Tests belegen die hohe UV-Empfindlichkeit von Resisten auf der Basis von Halogenphenolnovolaken. Im Vergleich zu nichthalogenhaltigen Novolakresisten wird eine 6 - 10fache (System: 4-Chlorphenolnovolak/4,4′-Bisazidobiphenyl (5%)) bzw. eine ca. 25fache (System: 4-Chlorphenol-/m-Cresolnovolak/Hexamethoxymethylmelamin (5%)) Steigerung der Empfindlichkeit erreicht. Zur Interpretation wird ein Mechanismus postuliert, demzufolge die durch Halogenabspaltung hervorgerufene Sekundärradikalbildung zu einer zusätzlichen Vernetzung beiträgt. In den melaminhaltigen Resisten katalysiert der gebildete Halogenwasserstoff (Hal· + RH → H-Hal + R·) außerdem die Reaktion der Melaminverbindung mit der Novolakmatrix.
    Notes: The photolysis of halogenophenol novolacs is determined by the substitution of halogens by hydrogen and the formation of quinoid groups and intermolecular crosslinks. This is concluded from elemental analysis, NMR, IR and optical absorption measurements. The rate of halogen release depends on the chemical nature of the halogen. It increases in the order F 〈 Cl 〈 Br 〈 I. Chlorine elimination from 4-position is favored over that from 2- and 3-position. Moreover, dimers release chlorine from 4-position much more readily than trimers and tetramers. ESR measurements at 77 K and flash photolysis studies at 296 K yielded evidence for the intermediate existence of phenoxyl and aryl radicals. Lithographic tests demonstrated the high UV-sensitivity of resist formulations based on halogen-containing novolacs. The increase in sensitivity relative to that of formulations based on nonhalogenated novolacs is 6 to 10fold system: 4-chlorophenol novolac/4,4′-bisazidobiphenyl (5%) and ca. 25fold system: 4-chlorophenol/m-cresol novolac/hexamethoxymethylmelamine (5%). A postulated reactions mechanism concerning the sensitivity increase takes into account that halogen elimination results in the formation of additional radicals that accelerate the rate of crosslinking. Moreover, hydrogen halide generated by hydrogen abstraction of halogen radicals (Hal· + RH → H-Hal + R·) provides for the acid required to catalyze the reaction of the melamine compound with the novolac matrix.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052140117
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  • 169
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    Crystallization behavior of polypropylene filled with calcium carbonate of various shape (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 215 (1994), S. 11-24 
    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: Calciumcarbonate unterschiedlicher Teilchenform (sphäarisch, kubisch und nadelfäormig) wurden mit Polypropylen (PP) in einer Zwei-Walzen-Mäuhle gemischt und anschließend zu Platten gepreßt. Der Einflußder Teilchenform auf das Kristallisationsverhalten der PP/CaCO3-Composite, d.h. Kristallisationspeaktemperatur (Tmax), Kristallisationsverlauf usw., wurde mittels Differentialkalorimetrie untersucht. Der Wert von Tmax häangt von der Größe der Gesamtoberfläache der CaCO3-Teilchen ab; Tmax ist bei nadelfäormigen Teilchen gräoßer als bei kubischen oder sphäarischen und hauangt in allen Fäallen der nicht-isothermen Kristallisation von der Abkäuhlgeschwindigkeit und der vorher erreichten maximalen Temperatur ab.
    Notes: Calcium carbonate of various particle shape (spheric, cubic, needle-shaped type) and polypropylene (PP) were mixed on a two roll mill and the mixture was pressed into plates. The effect of particle shape on the crystallization behavior of PP/CaCO3 composites, such as crystallization peak temperature (TMAX), crystallized pattern, etc., was investigated with differential scanning calorimetry measurements. The value of TMAX is explained by the total surface area of added CaCO3 particles; TMAX of needle-shaped series is larger than that of cubic or spheric ones. TMAX of various shaped CaCO3-filled PP totally depends on the cooling rate and maximum temperature in the non-isothermal crystallization, respectively.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052150102
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  • 170
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    Cationic polyelectrolytes, XIIPart. XI cf.8.. PEG-precursor for water-soluble cationic polymers with tertiary n-atoms in the main chain (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 215 (1994), S. 107-119 
    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: Durch Polyaddition von Polyethylenglykol (PEG) Oligoglycidylethern (Mn (PEG): 396,587, 1437 und 3554) mit asymmetrischen Diaminen, wie N,N-Dimethylund N,N-Diethyl-1,3-diaminopropan, wurden wasserläosliche kationische Polymere erhalten. Die Eigenschaften der kationischen Polymeren sind vom urspräunglichen PEG-Molekulargewicht und der Diaminreaktivitäat abhäangig. PEG mit Mn = 396 zeigt das beste Verhalten. In verdäunnten wäassrigen Läosungen und in wäassrigen 2M NaCl-Läosungen der Polymeren wurde das Polyelektrolytverhalten veranschaulicht. Die Gegenwart der PEG Kette bestimmt das Polyelektrolytverhalten in den 2M NaCl Läosungen.
    Notes: Water-soluble cationic polymers were obtained by polyaddition of poly(ethylene glycol) (PEG) diglycidylethers (M̄n of PEG were 396, 587, 1437 and 3554, resp.) with asymmetrical diamines such as N,N-dimethyl-1,3-diaminopropane and N,N-diethyl-1,3-diaminopropane. The cationic polymer properties depend on the PEG initial molecular weight and on the diamine reactivity too. PEG with M̄n = 396 had the best behaviour in these reactions. The polyelectrolyte feature of cationic polymers was emphasized both in dilute aqueous solutions and in 2M aqueous NaCl solutions. The polyelectrolyte behaviour in 2M aqueous NaCl solution is determined by the PEG chain presence.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052150109
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  • 171
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    Untersuchungen zur reaktion von o-kresol mit formaldehyd unter verwendung tertiärer amine (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 215 (1994), S. 139-145 
    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 Reaktion von o-Kresol mit Formaldehyd wurde unter Verwendung verschiedener tertiäarer Amine als Katalysatoren untersucht. Der Einfluß der Reaktionsparameter Basizitäat, Temperatur, Reaktionszeit und Formaldehydkonzentration wird diskutiert. Für die bevorzugte Bildung von 2,4-Bis(hydroxymethyl)-6-methylphenol wurden optimierte Synthesebedingungen erarbeitet. Die Bildung von Zwei-bzw. Mehrkernprodukten konnte nicht ausgeschlossen werden.
    Notes: The reaction between o-cresol and formaldehyde was investigated using various tertiary amines as catalysts. The influence of the reaction parameters basicity, temperature, reaction time and concentration of formaldehyde was discussed. To yield preferentially 2,4-bis(hydroxymethyl)-6-methylphenol the conditions of synthesis were optimized. The formation of bi- and polynuclear products cannot be avoided.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052150112
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  • 172
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    Effect of addition of cellulose powder on the viscometric behavior of liquid crystalline solutions of ethyl cellulose in m-cresol (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 215 (1994), S. 189-200 
    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 Scherviskositäat fläussigkristalliner Ethylcellulose, die mit Cellulosepulver unterschiedlicher Partikelgräoße gefäullt war, wurde bei konstantem Schergefäalle mit einem Kegel-Platte-Viskosimeter bestimmt. Der Einfluß des Cellulosepulvergehalts, des Läange/Breite-Verhäaltnisses der Pulverteilchen und der Temperatur auf das viskose Verhalten und die Phasenäubergäange wird diskutiert. Der Zusatz von Cellulosepulver erhäoht die Viskositäat und verringert die Aktivierungsenergie des Fließens(Ea), ohne jedoch die Phasenäubergäange zu beeinflussen. Die Viskositäat und die Aktivierungsenergie sind abhäangig vom Läange/Breite-Verhäaltnis der Pulverteilchen; mit zunehmender Gräoße dieses Verhäaltnisses wird die Viskositäatszunahme beschleunigt und die Aktivierungsenergie des Fließens erhäoht, wäahrend die Aktivierungsenergie mit steigendem Pulvergehalt abnimmt. Die Phasenumwandlungen sind unabhäangig von der Partikelform. Der Einfluß des Pulvergehalts auf Viskositäat und Aktivierungsenergie ist abhäangig von der Art der fläussigen Phase; in der anisotropen Phase ist der Einfluß geringer als in der isotropen Phase. Dies scheint von der Ausrichtung der Pulverteilchen und der stäabchenfäormigen Molekäule herzuräuhren.
    Notes: Steady-state shear viscosity for the liquid crystalline ethyl cellulose solution filled with cellulose powders was determined using a cone-plate-type viscometer and the effects of cellulose powder content, powder aspect ratio and temperature on the viscometric behavior and phase transformation were discussed. The addition of powder increased the viscosity and decreased the activation energy (Ea) for flow, but did not affect the phase transformation. The viscosity and Ea depended on the aspect ratio; with greater aspect ratio, the viscosity enhancement was accelerated and Ea as well as the decrease in Ea with powder content increased. The phase transformation did not depend on the aspect ratio, the dependences of viscosity and of Ea on powder content depended on the solution phase; the dependences for the anisotropic phase were smaller than those for the isotropic one. The findings appeared to originate from the alignments of powders and rod-like molecules.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052150116
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    Oxygen uptake methods as a tool to determine the mechanism of action of hindered amine light stabilizers1Paper presented at the “15th Annual International Conference on Advances in the Stabilization and Degradation of Polymers” in Luzern (Switzerland), June 2-4, 1993. (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 216 (1994), S. 37-44 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The UV-degradation of an unstabilized and two HALS stabilized polyethylene (PE) films is described. The degradations are characterized by measuring the oxygen uptake, the formation of CO and CO2, the FT-IR spectra, the mechanical properties, the stabilizer concentration and the oxygen content of the film.The oxygen uptake of the unstabilized PE film led to the expected changes in the IR spectra and embrittlement of the film, while the oxygen uptake by the HALS stabilized films caused only minor changes. The differences between the results for the unstabilized and the HALS stabilized polymers are explained assuming that the initiation of the photodegradation of PE is due to charge transfer complexes.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052160103
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    Current of status of exploitation of radical scavenging stabilizers in advanced polymer stabilizationPaper presented at the “15th Annual International Conference on Advances in the Stabilization and Degradation of Polymers” in Luzern (Switzerland), June 2-4, 1993. (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 216 (1994), S. 135-146 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Principal chemical pathways characteristic of active participation of radical scavenging polymer stabilizers (phenols, aromatic, hydroaromatic and hindered aliphatic amines) are outlined. Pathways resulting in a partial depletion or distortion of activity of stabilizers, in formation of polymer discolouring products, or in interactions in bifunctional stabilizers are involved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052160109
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    Poly(butyleneterephtalate) photolysis and photooxidation : Identification of the ir-absorbing productsPaper presented at the “15th Annual International Conference on Advances in the Stabilization and Degradation of Polymers” in Luzern (Switzerland), June 2-4, 1993. (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 216 (1994), S. 155-167 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Irradiations (λ≥300 nm) of poly(butyleneterphtalate) films were carried out in both vacum and air. Photoproducts were investigated by FTIR spectroscopy, chemical derivatization reactions and physical treatments. The repartition of photoproducts in the polymer was shown to be heterogeneous. A scheme accounting for the main routes of PBT photolysis was found on the basis of photoproducts identification. Most of oxidation products were analogous to vacum photolysis species; the mechanism of photooxidation proposed implied both pure photolytical processes and a photo-induced oxidation route.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052160111
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    Photo- and radiation-induced degradation of synthetic polymers: Polymer structure and stabilityPaper presented at the “15th Annual International Conference on Advances in the Stabilization and Degradation of Polymers” in Luzern (Switzerland), June 2-4, 1993. (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 216 (1994), S. 225-241 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effect of polymer density, processing conditions (quenching of annealing), degree of crystallinity, size of crystallite and mobility of polymer chains on the photo-and radiation-induced degradation and the polymer stability have been studied by UV, FTIR spectroscopic, viscosity and mechanical property measurements. Four kinds of annealed or quenched polyethylene (PE) films varying densities were used to the studies. Polystyrene (PSt) films were used to investigate the effect of chain mobility on polymer degradation. The following results were obtained. 1.In linear low density (LLD) PE, greater amounts of crosslinking (irradiated in vacuum) and chain scission (irradiated in air) were noticed than in mediun density (MD) PE and high density (HD) PE samples.2.Polyene formation is favored in the case of the irradiation in vacuum for LLDPE.3.Polymer stability evaluated by mechanical property such as elongation at break (%) is superior in LLDPE to MDPE and HDPE for annealed and quenched samples.4.Segmental motion of polymer chain also affects the polymer stability
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052160115
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    Eigenschaften von binären mischungen aus polyethylenen hoher dichte mit ultrahoher und normaler molmasse (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 217 (1994), S. 43-49 
    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 study is on two component blends of high density polyethylenes, having normal and ultra-high molecular weight. The polyethylenes were homogenized by two routes: in powder state or by rolling in melt, then pressed at temperatures in the range from 140°C to 220°C. Comparative studies showed that the way of homogenizing of the components does practically not affect the main mechanical properties of the blends when pressed at temperatures ≥ 160°C. Of special interest are the characteristics of those systems where ultra-high molecular weight polyethylene is the matrix component.
    Notes: Untersucht wurden binäre Mischungen von Polyethylenen hoher Dichte rnit normaler und ultrahochmolekularer Molmasse, die auf zweierlei Weise - in Pulverform oder durch Walzen im Schmelzezustand - homogenisiert und bei Temperaturen zwischen 140 und 220°C gepreßt waren.Es wurde festgestellt, daß die Art der Homogenisierung der Komponenten praktisch keinen Einfluß auf die Eigenschaften bei Preßtemperaturen ≥ 160°C hat. Von besonderem Interesse sind die Eigenschaften der Systeme, in welchen das ultrahochmolekulare Polyethylen die Rolle der Matrixkomponente spielt.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052170105
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  • 178
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    Rôle des pigments dans une réaction de polymérisation sous lumière UV-visible (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 218 (1994), S. 81-109 
    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: Das Verhalten eines neuartigen photoinitiierenden Systems, das die Polymerisation von pigmenthaltigen Schichten großer Dicke in einem Reaktionsschritt gestattet, wird dargestellt. Die verschiedenen Wechselwirkungen, die in einem pigmenthaltigen System auftreten, werden qualitativ beschrieben, und der Anteil der von einem Photoinitiator absorbierten Lichtintensität wird berechnet. Neben dem Absorptions- und Reflexionsverhalten von verschiedenen Pigmentklassen werden die optischen Eigenschaften verschiedener Strahlungsquellen untersucht, um die Strahlungsbereiche zu finden, die am besten mit den optischen Parametern der Pigmente korrespondieren. Weiterhin wird die Beschleunigung von Polymerisationen durch die photokatalytische Wirkung einiger Pigmente behandelt.
    Notes: Ce travail sur le rôe des pigments définit le comportement d'un nouveau systeme photosensible qui permet de polymériser des milieux épais et pigmentés selon un procédé en une seule étape. Les différentes interactions présentes en milieu pigmenté sont décrites de façon qualitative, et la part de l'intensité lumineuse absorbée par un photo-amorceur dans un systéme pigmenté est evaluée. Les propriétés optiques telles que l'absorption et la réflectance des différentes familles chimiques de pigments sont déterminées, et, en paralléle, les propriétés optiques des différentes sources d'irradiation sont étudiées de manière à répondre au mieux aux fenêtres de transmission des pigments. L'effet photocatalytique de certains pigments est mentionné, ceci afin d'amkliorer la réaction de polymérisation.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052180107
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  • 179
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    Molar mass distribution of polybutadiene synthesized with nickel-based Ziegler-Natta catalysts, I (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 218 (1994), S. 153-162 
    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 Herstellung von cis-1,4-Polybutadien erfolgte mittels Polymerisation von 1,3-Butadien mit einem Katalysatorsystem, das in einer zweistufigen Reaktion gebildet wird: (1) BF3 · O(C2H5)2 und Al(C2H5)3, (2) Ni(OOC8H15)2 und Al(C2H5)3, genannt in-situ-Katalysatorsystem.Die Molmassenverteilungen (MMD) der erhaltenen Polymeren sind mit der Größenausschlußchromatographie (SEC) untersucht worden. Sie lassen sich mit Summen aus Schulz-Flory-Funktionen (SFF) beschreiben. Veränderte Katalysatorformierungs- und Polymerisationsbedingungen beeinflussen die Parameter der SFF. Veränderte Peakflächen und Molmassenmittelwerte der Einzelpeaks zeigen, daß die Polymerisation über mehrere Arten aktiver Zentren verläuft.
    Notes: Cis-1,4-polybutadiene was produced by polymerization of 1,3-butadiene using a catalyst system formed by a two-step formation, Namely (1) BF3 . O(C2H5)2 and Al(C2H5)3, (2) Ni(OOC8H15)2 and Al(C2H5)3 named in-situ-catalyst.The molar mass distributions (MMD) of the polybutadienes are investigated by means of size exclusion chromatography (SEC). The MMD's were fitted by a sum of Schulz-Flory-Functions (SFF). Changed catalyst formation and polymerization conditions influenced the parameters of the SFF. Changed areas and changed molar mass averages indicate a polymerization with more than one peak maximum and kind of active species and lead to a better understanding of the polymerization.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052180111
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  • 180
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    Synthesis and characterization of epoxy resins containing chromium acrylate (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 219 (1994), S. 1-10 
    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: Durch Umsetzung von Chromacrylat mit Bisphenol A und einem Überschuß Epichlorhydrin wurden neuartige Epoxid-Harze hergestellt. Epoxy-Äquivalentgewicht, Gehalt an Hydroxygruppen und hydrolysierbarem Chlor sowie die Viskosität wurden bestimmt, und die Harze wurden mittels IR- und 1H-NMR-Spektroskopie charakterisiert. Die thermischen Eigenschaften der bei 30°C für 24 h mit Ciba Geigy HY 850 (aliphatisches Amin) gehärteten Harze wurden gemessen. Die Harze besitzen eine gute thermische und chemische Stabilität und eine gute elektrische Leitfähigkeit. Die Reaktion verläuft nach erster Ordnung; die Aktivierungsenergie beträgt 47 kJ mol-1 bzw. 34 kJ mol-1 mit bzw. ohne Chromacrylat. Aus spektroskopischen Untersuchungen wird geschlossen, daß das Chrom mit Bisphenol A einen Komplex bildet, der die Epoxidierung beschleunigt.
    Notes: Novel epoxy resins containing chromium acrylate have been synthesized by reacting chromium acrylate with bisphenol-A and excess epichlorohydrin. The quantities such as epoxy equivalent weight, hydroxy content, hydrolyzable chlorine content and viscosity have been determined. The resins have been characterized by IR and 1H NMR spectroscopy. The cured resins were evaluated for thermal properties. The curing of resins was carried out with Ciba Geigy HY 850 (aliphatic amine adduct) at 30°C for 24 h. The cured resins have excellent thermal and chemical resistance, in addition to an excellent electrical conductivity. The reaction follows first order kinetics with an activation energy of 47 kJ mol-1 and 34 kJ mol-1 in the presence and absence of chromium acrylate, respectively. The chromium forms a complex with bisphenol-A, as indicated by spectroscopic studies, which increases epoxidation.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052190101
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  • 181
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    Interpenetrating polymer networks based on liquid natural rubber. 1. Synthesis and effect of nco/oh ratio on physical and mechanical properties (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 219 (1994), S. 67-76 
    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: Interpenetrierende Polymernetzwerke (IPNs) aus Polystyrol und Polyurethan auf der Basis von hydroxyterminiertem Naturkautschuk mit unterschiedlichen NCO/OH-Verhältnissen wurden unter verschiedenen Reaktionsbedingungen hergestellt und zu widerstandsfähigen Filmen verarbeitet. Die IPNs wurden durch ihre physikalischen, mechanischen und morphologischen Eigenschaften wie Dichte, Shore-A-Härte, Vernetzungsdichte, Zugfestigkeit und Reißdehnung charakterisiert. Mit steigendem Polystyrolgehalt erhöhen sich auch Dichte, Shore-A-Härte und Zugfestigkeit, während die Reißdehnung abnimmt. Die Untersuchungen der Vernetzungsdichte lassen eine Phasenumkehr vermuten.
    Notes: Interpenetrating polymer networks (IPNs) of polyurethane based on hydroxyterminated natural rubber with varying NCO/OH ratios and polystyrene were synthesized under different experimental conditions. These IPNs were found to make tough films. The IPNs were characterized by their physical, mechanical and morphological properties like density, Shore-A hardness, crosslink density, tensile strength and elongation at break. The IPNs exhibited an increasing trend in density, Shore-A hardness and tensile strength with increasing polystyrene content, while elongation at break decreased with similar variation in polystyrene content. The crosslink density measurements indicated a possible phase inversion process.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052190106
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  • 182
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    Plasma treatment of polyethylene ultrafiltration membranes (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 219 (1994), S. 117-124 
    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 einer Plasmabehandlung von Ultrafiltrationsmembranen aus Polyethylen auf die Fouling- und Reinigungseigenschaften bei der Filtration von Rinderserumalbumin werden diskutiert. Bei 2,45 GHz erzeugtes Luft-Plasma steigert die Hydrophilie der Membranoberfläche von 0 auf 60%. Der Durchfluß bleibt bei 90 bis 99%. Mit Plasma behandelte Membranen sind leichter zu reinigen als unbehandelte; dennoch sind sie anfälliger für die Ablagerung von Rinderserumalbumin.
    Notes: The effect of plasma treatment of polyethylene ultrafiltration membranes on fouling and cleaning phenomena during filtration of bovine serum albumin solutions is discussed. Air-plasma of 2.45 GHz raises the membrane surface hydrophilicity from 0 up to 60%. The flux is maintained at 90-99%. Plasma-treated membranes are easier to clean than untreated polyethylene membranes. Despite that, the plasma-modified membranes are susceptible to more intensive deposition of albumin.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052190110
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    Preparation and characteristics of immobilized glucose oxidase on membranes of photosensitive polymers (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 219 (1994), S. 101-115 
    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 Immobilisierung von Glucose-Oxidase in einer Poly(vinylalkohol) (PVAL)-Membran in Gegenwart von UV-Photoinitiatoren wurde untersucht. Enzym-Membranen wurden aus PVAL-Diazoharz- und PVAL-Photoinitiator-Systemen durch Vernetzung mit UV-Licht hergestellt. Mit diesen immobilisierten Glucose-Oxidase-Membranen wurde eine wirkungsvolle Enzymelektrode entwickelt, deren Eigenschaften untersucht wurden. Der Einfluß der Photoinitiatorkonzentration in Poly(vinylalkohol) und der UV-Bestrahlungsdauer auf den Grad der Unlöslichkeit sowie die Aktivitätsausbeute der Membran wurden mit Glucose als Substrat untersucht. Temperatur- und pH-Abhängigkeit der relativen Aktivität, Stabilität bei mehrmaligem Gebrauch, Lagerstabilität und Kalibrierungsdiagramme der Enzym-Membranen wurden ermittelt. Eine beim Erstgebrauch auftretende Instabilitätserscheinung der Membranen wurde ebenfalls untersucht.
    Notes: A study of the immobilization of glucose oxidase on a poly(vinyl alcohol) (PVAL) membrane in the presence of UV sensitizers was carried out. Enzyme membranes were prepared from PVAL-diazoresin and PVAL-sensitizer systems, crosslinked by means of UV irradiation. An effective enzyme electrode was developed by using the immobilized glucose oxidase membrane, and its characteristics were investigated. The effects of the concentration of sensitizers in poly(vinyl alcohol) and UV irradiation time on the degree of insolubility as well as the activity yield of the membrane were examined for the immobilized glucose oxidase using glucose as a substrate. Temperature and pH dependences of the relative activity, stability in repeated use, storage stability and calibration plots of the enzyme membranes were evaluated. The unstability phenomenon, found in the initial use of the immobilized glucose oxidase membrane, which was prepared from PVAL-sensitizer system, was also investigated.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052190109
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  • 184
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    Auswirkungen von Sterilisationsverfahren auf biologisch abbaubare Kunststoffe (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 219 (1994), S. 11-26 
    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: Biopol, Biocellat and Mater-Bi, three biologically decomposable plastics have been tested for their use in medical industries. Biopol did not loose its stress and stiffness under sterilisation, and was also resistant against temperature and alcohol. Mater-Bi and Biocellat, the two other materials, did not satisfy the test applications. Water vapor sterilisation, temperature up to 60°C, at higher temperatures this material will embrittle.
    Notes: Für den Einsatz biologisch abbaubarer Kunststoffe in der pharmazeutischen Industrie und Medizintechnik wurden Produkte verschiedener Hersteller, wie Biopol, Biocellat und Mater-Bi untersucht. Dabei zeigte vor allem Biopol das notwendige Anforderungsprofil, d.h. die Anwendbarkeit aller Sterilisationsverfahren ohne Festigkeitsbzw. Steifigkeitsverluste sowie Temperatur- und Alkoholbeständigkeit. Dagegen wiesen die Werkstoffe Mater-Bi und Biocellat einige Schwachstellen auf. Bei Mater-Bi lagen diese bei der Wasserdampfsterilisation sowie bei der geringen thermischen und Medienbeständigkeit. Biocellat versprödet dagegen durch die erhöhte Temperatur bei der Dampfsterilisation, d.h. daß ein Einsatz über 60°C nicht möglich wäre.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052190102
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  • 185
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    Polymers and copolymers based on vinyl tetrazoles, 2Part 1 cf.10.. Alkylation of poly(5-vinyl tetrazole) (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 219 (1994), S. 89-99 
    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 Alkylierung von Poly(5-vinyltetrazol) mit Dimethylsulfat und tert-Butylalkohol sowie Alkylhalogeniden RHal (R=CH3, C2H5, CH2—CH=CH2, n-C4H9 und t-C4H9) und die Kinetik dieser Reaktion wurden untersucht, um eine neue Herstellungsmethode für tetrazolhaltige Polymere mit wertvollen Eigenschaften zu entwickeln. Die vergleichenden Untersuchungen über die isomere Zusammensetzung und die spektroskopischen Daten von Poly(N-alkyl-5-vinyltetrazol)en, die durch die Alkylierung von Poly(5-vinyltetrazol) sowie durch die Copolymerisation der entsprechenden Monomeren hergestellt wurden, wurden mit IR-, 1H-NMR- und 13C-NMR-Spektroskopie durchgeführt. Der Alkylierungsumsatz beträgt bis zu 99,8%; dadurch können polymere Produkte erhalten werden, deren Zusammensetzung, Struktur und Eigenschaften denen der Homo- und Copolymeren sehr ähnlich sind.
    Notes: Alkylation of poly(5-vinyl tetrazole) with dimethyl sulfate and tert-butyl alcohol as well as with alkyl halides RHal (R=CH3, C2H5, CH2—CH=CH2, n-C4H9, t-C4H9) has been studied under various conditions in order to develop a new method of synthesis of tetrazole-containing polymers having a complex of valuable properties. The kinetic study of the process and comparison of isomeric compositions and spectroscopic characteristics (IR, 1H NMR and 13C NMR) of poly(N-alkyl-5-vinyl tetrazole)s synthesized by alkylation of poly(5-vinyl tetrazole) and of those prepared by (co)polymerization of the corresponding vinyl tetrazoles have been carried out. The alkylation is found to proceed to high conversion extents (up to 99.8%) and enables to obtain a wide variety of polymeric products having the composition, structure and properties very similar to those of homo- and copolymers.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052190108
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  • 186
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    Dyes for nonlinear optics prepared from 2-hydroxyethyl methacrylate. Nonlinear properties of the resulting copolymers (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 220 (1994), S. 75-87 
    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: Farbstoffe mit nichtlinearen optischen Eigenschaften wurden in einer zweistufigen Synthese aus 2-Hydroxyethylmethacrylat (HEMA), 4-Carboxybenzaldehyd und verschiedenen Anilinderivaten hergestellt. Die Farbstoffe (aromatische Iminester von HEMA) wurden mit Styrol copolymerisiert, die erhaltenen Copolymere wurden mit DSC sowie IR-, 1H NMR- und UV-VIS-Spektroskopie charakterisiert, und ihre nichtlinearen Eigenschaften wurden untersucht. Es zeigte sich, daß die nichtlinearen Koeffizienten d31 und d33 vom Farbstoffgehalt der Copolymeren und der Art der elektronenspendenden Gruppen abhängig sind.
    Notes: Dyes for nonlinear optics have been synthesized in two steps from 2-hydroxyethyl methacrylate (HEMA), 4-carboxybenzaldehyde and various substituted anilines. The obtained dyes (aromatic imine esters of HEMA) have been copolymerized with styrene, the copolymers characterized by DSC as well as IR, 1H NMR and UV-VIS spectroscopy, and studied for their nonlinear properties. The d31 and d33 nonlinear coefficients proved to be dependent on the dye content of the copolymers and on the nature of electrondonating groups.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052200107
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    Viscosity behaviour of multivalent metal ion-containing carboxymethyl cellulose solutions (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 220 (1994), 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: Der Einfluß von Ca2+-bzw. Al3+-Ionen auf das Viskositätsverhalten (Salzverträglichkeit) wäßriger Lösungen von Natriumcarboxymethylcellulose (CMC) sowohl mit unterschiedlichem Polymerisationsgrad (DP) als auch mit unterschiedlichem Substitutionsgrad (DS) und verschiedenartiger Substitutentenverteilung wurde untersucht. Aus Viskositätsmessungen mit einem Rotationsviskosimeter bei einer Scherrate von 500 s-1 geht hervor, daß die relative Abnahme der Viskosität im Ergebnis des Zusatzes der mehrwertigen Metallkationen unabhängig vom DP (im Bereich von 160 bis 900) der CMC ist. Homogen hergestellte CMC-Proben 2 mit einem größeren Gehalt an 2,3,6-Tri-O-carboxymethylglucose-Einheiten in der Polymerkette weisen im Vergleich zu heterogen hergestellten CMCs 1 bei gleichem Gesamt-DS eine höhere Salzverträglichkeit auf.
    Notes: The influence of Ca2+-and Al3+-ions, respectively, upon the viscosity behaviour (so-called salt tolerance) of aqueous solutions of sodium carboxymethyl cellulose (CMC) with different degree of polymerization (DP) and, on the other hand, with both different degree of substitution (DS) and distribution of substituents, was investigated. Viscosimetry by means of a rotational rheometer at a shear rate of 500 s-1 shows that the relative drop in viscosity as a result of addition of the multivalent metal cations is independent of DP (ranging from 160 to 900) of the CMC samples. Homogeneously synthesized CMCs (2) with a higher content of 2,3,6-tri-O-carboxymethyl glucose units in the polymer chain possess a significantly higher salt tolerance than those (1) prepared under heterogeneous reaction conditions at comparable total DS values.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052200111
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    Modification of melamine-formaldehyde moulding compounds with ethylene/vinyl acetate copolymers (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 222 (1994), S. 61-87 
    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: Melamin-Formaldehyd-Harz-Formmassen (MF) wurden durch mechanisches Mischen mit Ethylen-Vinylacetat-Copolymeren (EVA) und teilverseiftem EVA modifiziert, wobei Etherbindungen zwischen dem hydrolysierten EVA und dem MF-Harz nachgewiesen werden konnten, die die mechanischen Eigenschaften von spritzgepreßten Formteilen im Vergleich zur Modifizierung mit EVA verbessern. Der Zusatz solcher Modifikatoren erhöht die Duktilität und verringert im Falle von EVA die Nachschwindung der überaus steifen MF-Matrix, solange der Modifikatoranteil gering bleibt. Dagegen werden die Steifigkeit und die Wärmeformbeständigkeit verschlechtert. Die durch solche unvernetzten Polymeren erreichbare Steigerung der Schlagzähigkeit bleibt allerdings unzureichend.
    Notes: Melamine-formaldehyde moulding compounds (MF) were modified by mechanical mixing with ethylene/vinyl acetate copolymers (EVA) and with partially hydrolysed EVA. Ether linkages between the hydrolysed material and the MF resin improve the mechanical properties of the transfer moulded parts containing the hydrolysed material compared to those made with EVA. The use of both modifying polymers improves the ductility and, in case of the partially hydrolysed material, the postshrinkage of the extremely rigid MF matrix, as long as the modification polymer content is kept low. On the contrary, Young's modulus and the heat deflection temperature are deteriorated. The improvement in impact strength by use of those uncrosslinked polymers is still insufficient.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052220106
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    Synthesis and properties of biodegradable copolyesteramides: Nylon 6,6/∊-caprolactone copolymers, 1 (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 222 (1994), S. 111-123 
    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 Reihe von Copolyesteramiden mit Molekulargewichten zwischen 1000 und 7000 (GPC, NMR) wurden aus Adipinsäure/1,6-Hexandiamin/∊-Caprolacton bzw. Nylon 6,6-Salz/∊-Caprolacton hergestellt. Die thermischen Eigenschaften der synthetisierten Polymeren (Glasübergangs-, Schmelz-, und Zersetzungstemperaturen, Schmelzenthalpien) wurden durch DSC- und TGA-Messungen bestimmt und in Bezug auf das Comonomerverhältnis in der Ausgangsmischung diskutiert. Die Übereinstimmung der Copolymerzusammensetzung mit dem Ausgangscomonomerverhältnis wurde mit FT-IR- und NMR-Spektroskopie untersucht. Die Bioabbaubarkeit der Copolyesteramide wurde durch enzymatische Hydrolyse geprüft.
    Notes: A series of copolyesteramides based on adipic acid/1,6-hexane diamine/∊-caprolactone and Nylon 6,6 salt/∊-caprolactone were synthesized. Their molecular weights, determined by gel permeation chromatography and NMR spectroscopy, were found to lie within the range from 1000 up to 7000. Their thermal properties (glass transitions, melting points and heats of melting, and decomposition temperatures) were recorded with diferential scanning calorimetry and thermogravimetry, respectively, and correlated to the comonomer feed composition. The FT-IR and NMR spectra were also recorded in order to confirm the composition of the copolyesteramides and to compare them with that of the comonomer feed. The biodegradability of the synthesized copolymers was tested by enzymatic hydrolysis.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052220109
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  • 190
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    Study of the condensation products of abietic acid with formaldehyde at high temperatures (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 222 (1994), S. 165-174 
    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: Durch sulfonsäurekatalysierte Umsetzung von Abietinsäure und Paraformaldehyd bei hohen Temperaturen wurden neuartige Kondensationsprodukte erhalten. Als Nebenprodukte der Polykondensation werden eine Ketoverbindung sowie Wasser und Kohlendioxid gebildet. Die Carboxygruppen der Abietinsäure sind an der Kondensationsreaktion beteiligt. In Abwesenheit von Paraformaldehyd wurde das Abietinsäure/Sulfonsäurekatalysator-System untersucht, um zusätzliche Informationen über die Reaktion zu erhalten. Der Reaktionsverlauf hängt von der Temperatur und der chemischen Struktur des Katalysators ab. Ein möglicher Reaktionsmechanismus der Kondensation wird diskutiert.
    Notes: New condensation products have been synthesized by heating abietic acid and formaldehyde at high temperatures in the presence of sulfonic-type acid catalysts. The main polycondensation reaction is associated with a secondary one which leads to a ketonic compound, carbon dioxide and water. The carboxylic groups of abietic acid participate in this condensation reaction. The behaviour of the abietic acid-sulfonic acid catalyst system was studied in absence of formaldehyde to acquire additional information about the reaction. The process is defined by the reaction temperature and chemical nature of the catalyst. A possible mechanism of the condensation reaction is discussed on the basis of the obtained results.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052220112
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  • 191
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    Tailored polymers by cationic ring-opening polymerization (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 223 (1994), S. 1-11 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: After a general classification of the cationic ring-opening polymerizations (CROP's) according to their polymerization mechanism, a number of examples of tailored polymers based on CROP are presented. The monomers used for the synthesis of these tailored structures are tetrahydrofuran (THF), N-tert-butyl aziridine (TBA), 2-methyl-1,3-oxazoline (MeOX) and 1,3-dioxolane (DXL).The polymer structures include different block and graft copolymers, macromonomers, star-shaped polymers, polymer networks and interpenetrating polymer networks (IPNs).
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052230101
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  • 192
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    Massgeschneiderte PolymereVortrag anläßlich der Tagung der Fachgruppe “Makromolekulare Chemie” der Gesellschaft Deutscher Chemiker über “Fortschritte in der Polymersynthese” in Bad Nauheim, 21.-22. März 1994. Synthesestrategien für Telechele, Makromonomere, Block- und Pfropfcopolymere (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 223 (1994), S. 29-46 
    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 diesem Beitrag wird ein überblick über neuere Entwicklungen auf dem Gebiet der Synthese von Telechelen, Makromonomeren, Block- und Pfropfcopolymeren gegeben. Synthesestrategien aus den Bereichen der Polykondensation, der radikalischen, anionischen und kationischen Polymerisation, der Kettenspaltung sowie der Criss-Cross-Cycloaddition werden diskutiert.
    Notes: New developments in the synthesis of telechelics, macromonomers, block- and graftcopolymers are presented. Synthetic strategies for them are demonstrated with examples from different fields such as polycondensation, radical, anionic, and cationic polymerization, chain cleavage and criss-cross-cycloaddition.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052230103
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  • 193
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    Alkane als initiatoren zur radikalischen polymerizationHerrn Professor Dr. rer. nat. Dr.-Ing. E.h. Hansjörg Sinn mit den besten Wünschen zum 65. Geburtstag gewidmet (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 223 (1994), S. 69-79 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Alkanes with highly substituted carbon-carbon bonds can be cleaved in free radicals by homolytic dissociation under the influence of thermal energy. The energy of dissociation is mainly determined by the type and size of the respective substituents. For tetraarylbutane dinitriles the temperatures of decomposition are in the range of other technically used initiators. But nevertheless, these compounds are up to now rather seldom used to initiate free radical polymerizations. This is connected with the special mechanism of initiation: the formed highly substituted alkyl radicals are relatively stable and show only a rather low reactivity against the usually used monomers. Therefore, in the beginning of the polymerization the radical concentration is rather high which leads not only to addition to monomers but also to a pronounced primary radical termination. In some cases this termination process is reversible which results in an unusual polymerization kinetics. Depending on the type of monomer and the degree of reversibility of the primary radical termination, either a period of “dead-end” polymerization follows or the cleavage of the oligomers at the chain end results in a re-initiation process with a “normal” polymerization with increased rate. The reaction mechanism, kinetics and some possible applications of such initiating alkanes are reported.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052230106
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  • 194
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    Cycloolefin-copolymere: Eine neue klasse transparenter thermoplasteHerrn Prof. Dr. H. Sinn zum 65. Geburtstag gewidmet. (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 223 (1994), S. 121-133 
    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: Untersuchungen wesentlicher Aspekte der Polymerisation und der Eigenschaftsmodifikation auf Metallocen-Katalyse basierender Cycloolefin-Copolymere (COC) zeigen, daß mit dieser Monomer-Katalysator-Kombination eine neue Klasse transparenter Thermoplasten zugänglich gemacht wird. COC können mit Metallocenen in beliebiger zusammensetzung und mit kontrollierter Mikrostruktur hergestellt werden. Die somit erreichte und durch zusätzliche Modifikationen noch erweiterbare Breite des Eigenschaftsspektrums ermöglicht vielfältige Anwendungen dieser neuen Polymerklasse. Die wichtigsten Schlüsselfaktoren im rohstofflich-technologischen Bereich, die diese Struktur- und Eigenschaftsvielfalt ergeben, werden beispielhaft beschrieben.
    Notes: Investigation of the polymerization process and property modification of metallocene-based cycloolefin copolymers (COC) shows that this monomer-catalyst combination enables synthesis of a new class of transparent thermoplastic polymers. Metallocene catalysis offers much opportunity to vary the composition and microstructure of the copolymers. The breadth of the polymer spectrum which can be further widened by polymer modification enables many applications for this new class of thermoplastics. The key parameters that control structure and properties in the COC family are discussed in this paper.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052230109
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  • 195
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    Funktionalisierte Kammpolymere: Synthesen, modifizierung und anwendungen (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 223 (1994), S. 165-175 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The present paper deals with the synthesis and modification of functionalized polymers characterized by a special molecular architecture. The reactivity of a functionalized polymer with comb-like structure can be controlled in a significant manner by the crystalline order of the side chains. In contrast, photocrosslinking of comblike polymers containing cinnamic components in the side chains influences the crystallization process. The air drying process of a modified polybutadiene system with comb-like structure was shown to depend sensitively on the side chain order. Enzymatic synthesis of new monomers and polymers is briefly reviewed. The complexing capability of cyclodextrines were used to synthesize polyrotaxanes. Finally, the synthesis of a chiral polymerizable dendrimer containing eight estergroups in the monomer unit is presented.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052230112
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  • 196
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    Intramolekular vernetzte poly(organosiloxan)partikel (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 223 (1994), S. 203-216 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Intramolecularly crosslinked poly(organosiloxane) particles are prepared by means of emulsion polycondensation or emulsion polymerization of alkoxysilanes or cyclic organic siloxanes. Starting from these intramolecularly crosslinked poly(organosiloxane) particles, graft copolymers are obtained by free-radical emulsion polymerization of unsaturated olefinic monomers (e.g. acrylates, styrene) in the presence of (functionalized) organosiloxanes. Intramolecularly crosslinked poly(siloxane) particles and their graft copolymers are characterized by means of light scattering (in dispersion), electron microscopy and thermal analyses (DSC, DMTA).
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052230115
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  • 197
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    Study on poly(2,6-dimethyl-1,4-phenylene oxide)/SBS triblock copolymer blends (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 214 (1994), S. 153-167 
    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 Zusammenhang zwischen der Mischbarkeit und den physikalischen Eigenschaften von Polymerblends aus Poly(2,6-dimethyl-1,4-phenylenoxid) (PPO), die in unterschiedlichen Zusammensetzungen in einem Doppelschneckenextruder mit Polystyrol, schlagzähem Polystyrol oder Styrol-Butadien-Copolymeren hergestellt wurden, wird diskutiert. Die Verträglichkeit der Komponenten wurde mittels DSC und DMA, die Morphologie der Blends mittels SEM untersucht. Mit abnehmendem Polystyrolanteil wurde eine schlechtere Mischbarkeit bei den Blends beobachtet, deren Kerbschlagempfindlichkeit sich erhöhte. Die Untersuchungsergebnisse werden mit dem Micellmodell interpretiert.
    Notes: The relationship between the miscibility and the physical properties of polymer blends of poly(2,6-dimethyl-1,4-phenylene oxide) and polystyrene (PS), high-impact polystyrene (IPS) and poly(styrene-block-butadiene-block-styrene) (SBS), which are blended in different compositions by a twin-screw extruder is discussed. The three types of SBS that were used are SBS1, SBS2 and SBS3 having different styrene/butadiene ratios. Dynamic mechanical analysis and differential scanning calorimetry were used to study the miscibility. The morphology was examined by SEM. The miscibility of the blends decreases with decreasing PS content. The notch sensitivity is improved by blending. Finally, the micelle model was used to explain the testing phenomena.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052140114
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  • 198
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    Water-soluble polyamides as potential drug carriers, VIIPresented in part at the Symposium on Water-soluble Polymers, 198th National Meeting Am. Chem. Soc., Miami Beach, Florida, 10-16 September 1989. For Part VI, cf1.. Synthesis of polymers containing intrachain- or extrachain-type amine ligands by interfacial polymerization (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 214 (1994), S. 137-152 
    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: Aliphatische Polyamide mit Poly(ethylenoxid)-Kettensegmenten unterschiedlicher Länge wurden durch Grenzflächenpolymerisation aus Succinylchlorid und Jeffamine ED-900 (O,O'-Bis(2-aminopropyl)poly(ethylenglykol) 800) bzw. Jeffamine ED-2001 (O,O'-Bis(2-aminopropyl)poly(ethylenglykol) 1900) zur Verwendung als Trägersubstanzen für Medikamente synthetisiert. Copolyamide mit kurzkettigen Diamin- und Jeffamine-Segmenten sowie Polyamide aus Cystin und Diamineinheiten wurden auf die gleiche Weise hergestellt. Die Polymerisationen wurden im zweiphasigen System Dichlormethan/Wasser bei Temperaturen um 0°C durchgeführt. Die Polymerprodukte wurden durch stufenweise Dialyse in wäßriger Phase bis zu einem Molekulargewicht von 25000 fraktioniert, nach Gefriertrocknung als wasserlösliche Harze oder Feststoffe erhalten und durch Mikroanalyse sowie 1H NMR-Spektroskopie charakterisiert. Die inhärenten Viskositäten liegen im Bereich von 10-20 ml/g. Die Eignung eines repräsentativen Zielmoleküls zur Bindung von Medikamenten wurde durch eine kovalente Verankerung einer als Medikamentmodell fungierenden Ferrocen-Verbindung untersucht. Dabei wurde ein wasserlösliches Polymer-Ferrocen-Konjugat erhalten.
    Notes: Aliphatic polyamides comprising poly(ethylene oxide) chain segments of various lengths, designed for use as drug carriers, are synthesized by interfacial polymerization of succinyl chloride with the two Jeffamine types ED-900 and ED-2001, formally described by the supplier as O,O'-bis(2-aminopropyl)poly(ethylene glycol) 800 and O,O'-bis(2-aminopropyl)poly(ethylene glycol) 1900. Copolyamides comprising both short-chain diamine and Jeffamine segments are similarly prepared, as are polyamides made up of cystine and diamine segments. The polymerizations are performed in a two-phase methylene chloride-water system at temperatures near or below 0°C. The product polymers, crudely fractionated by staged aqueous-phase dialysis at an ultimate molecular-mass cut-off of 25000, are collected after freeze-drying as water-soluble resins or solids and are characterized microanalytically and by 1H NMR spectroscopy. Inherent viscosities are in the range of 10-20 ml g-1. The drug-binding potential of a representative target polymer is probed by the covalent anchoring of a ferrocene compound used as a drug model, giving a water-soluble polymer-ferrocene conjugate.
    Additional Material: 2 Tab.
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    URL: http://dx.doi.org/10.1002/apmc.1994.052140113
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  • 199
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    Studies on vinyl ester resin and its urethane derivative as coating materials (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 214 (1994), S. 211-216 
    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: Über die Anwendung von Vinylesterharzen aus dem Diglycidylether von Bisphenol A sowie dessen Urethanderivat als Beschichtungsmaterial wird berichtet. Die mit den Harzen beschichteten Flußstahlplatten wurden auf Oberflächenglanz, Kratzfestigkeit und Chemikalienbeständigkeit untersucht. Harze mit Styrolanteil zeigen deutlich verbesserte Beschichtungseigenschaften.
    Notes: The present paper is concerned with the coating applications of a vinyl ester resin derived from diglycidyl ether of bisphenol-A and its urethane derivative. The mild steel panels coated with the synthesized resins were evaluated for their gloss on the surface, scratch hardness and chemical resistance. The incorporation of styrene in the resin systems improves the properties of coatings remarkably.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052140118
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  • 200
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    Silica gel supported zirconocene dichloride/methylalumoxane catalysts for ethylene polymerization: Effects of heterogenation on activity, polymer microstructure and product morphology (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 215 (1994), S. 47-57 
    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: Das Katalysatorsystem Zirkonocendichlorid/Methylalumoxan wurde auf Siliciumdioxid aufgebracht, um Katalysatoren fur die Suspensions- order Gasphasenpolymerisation von Ethylen herzustellen. Die häochste Aktivitäat wurde für eine sandwichartige, dreilagige Verankerung von Zirkonzentren auf der Träageroberfläache gefunden. Dieneuen Katalysatorsysteme besitzen eine im Vergleich zu den entsprechenden homogenen Katalysatoren geringere Aktivitäat. Die Immobilisierung der aktiven Katalysatorzentren führt zu einer deutlichen Erhäohung der Polymermolmassen. Dabei bleibt die enge Molekulargewichtsverteilung der Polymerprodukte nahezu erhalten. Solche auf Träager aufgebrachte Metallocen-Katalysatoren käonnten für die Herstellung von Polyethylenen mit kontrollierter Rheologie Anwendung finden.
    Notes: The system zirconocene dichloride/methylalumoxane was supported on silica in order to provide ethylene polymerization catalysts for suspension or gas phase processes. Highest activity was found for a sandwich-like, three layer anchoring of the zirconium centers on the support surface. The new catalyst systems show a decrease of activity compared to polymerization experiments in homogeneous phase. However, the molecular weights are increased and the weight distributions remain narrow by immobilization of the active catalyst sites. Those supported metallocene catalysts could find application for the synthesis of polyethylene materials with controlled rheology.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052150105
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