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  • 1990-1994  (11,164)
  • General Chemistry  (6,129)
  • Biochemistry and Biotechnology  (4,119)
  • Rat  (915)
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  • 101
    Electronic Resource
    Electronic Resource
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02244774
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  • 102
    Electronic Resource
    Electronic Resource
    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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  • 103
    Electronic Resource
    Electronic Resource
    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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  • 104
    Electronic Resource
    Electronic Resource
    Up-regulation of β1-adrenergic receptors in rat brain after chronic citalopram and fluoxetine treatments (1994)
    Springer
    Psychopharmacology 115 (1994), S. 543-546 
    Details
    ISSN: 1432-2072
    Keywords: β1-adrenergic receptors ; Rat ; Brain ; Citalopram ; Fluoxetine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Quantitative receptor autoradiography was used to study the effects of the selective serotonin reuptake inhibitors citalopram and fluoxetine and the tricyclic antidepressant imipramine on the regulation of β1-adrenergic receptors in the rat brain. Rats were treated with saline, citalopram (10 mg kg−1), fluoxetine (10 mg kg−1), or imipramine (15 mg kg−1) SC once daily for 14 days. [125I]Iodocyanopindolol binding to β1-adrenergic receptors was found to increase significantly in the caudate-putamen and the somatosensory areas of the frontal cortex after both citalopram and fluoxetine treatments. Imipramine treatment elicited a marked decrease in β1 binding in the outer laminae of the cingulate cortex, as well as in the motor and somatosensory areas of the frontal cortex. In a separate experiment, rats were treated with saline, citalopram (2.5, 10 and 20 mg kg−1) or fluoxetine (2.5, 10 and 20 mg kg−1) SC once daily for 14 days. The effects of citalopram and fluoxetine on β1 receptors in the somatosensory cortex and caudate-putamen were replicated. These results demonstrate that chronic administration of selective serotonin reuptake inhibitors, in contrast to imipramine, can cause a regional up-regulation of β1-adrenergic receptors in the rat brain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02245579
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  • 105
    Electronic Resource
    Electronic Resource
    Facilitated acquisition of a temporal discrimination following destruction of the ascending 5-hydroxytryptaminergic pathways (1994)
    Springer
    Psychopharmacology 116 (1994), S. 373-378 
    Details
    ISSN: 1432-2072
    Keywords: 5-Hydroxytryptamine ; 5,7-Dihydroxytryptamine ; Operant behaviour ; Timing ; Interval bisection procedure ; Acquisition ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This experiment examined the effect of destroying the 5-hydroxytryptaminergic (5HTergic) pathways on the acquisition and performance of discrimination between two brief time intervals. Rats that had received injections of 5,7-dihydroxytryptamine into the dorsal and median raphe nuclei, and sham-lesioned control rats were trained in a series of discrete trials to press lever A following a 200-ms presentation of a light stimulus and lever B following an 800-ms presentation of the same stimulus. Both groups gradually acquired accurate performance, attaining 80%–85% accuracy by the end of 40 sessions. The lesioned group learnt the task significantly faster than the control group. When stable performance had been attained, “probe” trials were introduced in which the light was presented for intermediate durations. Both groups showed sigmoid functions relating percent choice of lever B to log stimulus duration. The bisection point (duration corresponding to 50% choice of lever B) did not differ significantly between the two groups; however, the Weber fraction was significantly smaller in the lesioned group than in the control group. The levels of 5HT and 5-hydroxy-indole-acetic acid were markedly reduced in the brains of the lesioned rats, but the levels of noradrenaline and dopamine were not altered. The results indicate that destruction of the 5HTergic pathways facilitates acquisition of a temporal discrimination. The lack of an effect of the lesion on the bisection point contrasts with our previous finding using longer stimulus durations; it is suggested that different behavioural processes may underlie millisecond-range and second-range temporal discrimination, and that these may be differently affected by 5HT depletion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02245343
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  • 106
    Electronic Resource
    Electronic Resource
    The atypical antipsychotic, remoxipride, blocks phencyclidine-induced disruption of prepulse inhibition in the rat (1994)
    Springer
    Psychopharmacology 116 (1994), S. 437-442 
    Details
    ISSN: 1432-2072
    Keywords: Antipsychotic agents ; Acoustic startle ; Prepulse inhibition ; Schizophrenia ; Phencyclidine ; Remoxipride ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effect of various typical (haloperidol) and atypical (clozapine, raclopride, remoxipride) antipsychotics on phencyclidine (PCP)-induced disruption of sensorimotor gating was tested in rats using an acoustic startle paradigm. Clozapine (4–40 µmol/kg), haloperidol (1–5 µmol/kg) and raclopride (1–12 µmol/kg) failed to reverse PCP-induced disruption of prepulse inhibition (PPI) of the acoustic startle response. In contrast, remoxipride (12–60 µmol/kg) caused a dose-dependent block of this effect. PCP-induced disruption of PPI is a widely accepted animal model of a corresponding behavioural deficit observed in schizophrenia although little evidence has been presented that it is in fact sensitive to antipsychotic agents. The present results indicate that remoxipride behaves in a unique way in this model compared to clozapine, haloperidol and raclopride.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02247475
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  • 107
    Electronic Resource
    Electronic Resource
    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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  • 108
    Electronic Resource
    Electronic Resource
    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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  • 109
    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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  • 110
    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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  • 111
    Electronic Resource
    Electronic Resource
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02247471
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  • 112
    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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  • 113
    Electronic Resource
    Electronic Resource
    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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  • 114
    Electronic Resource
    Electronic Resource
    Regional brain distribution of risperidone and its active metabolite 9-hydroxy-risperidone in the rat (1994)
    Springer
    Psychopharmacology 114 (1994), S. 53-62 
    Details
    ISSN: 1432-2072
    Keywords: Risperidone ; 9-Hydroxy-risperidone ; Active metabolite ; Antipsychotic ; 5-HT2 Antagonist ; Dopamine-D2 antagonist ; Pharmacokinetics ; Regional brain distribution ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Risperidone is a new benzisoxazole antipsychotic. 9-Hydroxy-risperidone is the major plasma metabolite of risperidone. The pharmacological properties of 9-hydroxy-risperidone were studied and appeared to be comparable to those of risperidone itself, both in respect of the profile of interactions with various neurotransmitters and its potency, activity, and onset and duration of action. The absorption, plasma levels and regional brain distribution of risperidone, metabolically formed 9-hydroxy-risperidone and total radioactivity were studied in the male Wistar rat after single subcutaneous administration of radiolabelled risperidone at 0.02 mg/kg. Concentrations were determined by HPLC separation, and off-line determination of the radioactivity with liquid scintillation counting. Risperidone was well absorbed. Maximum plasma concentrations were reached at 0.5–1 h after subcutaneous administration. Plasma concentrations of 9-hydroxy-risperidone were higher than those of risperidone from 2 h after dosing. In plasma, the apparent elimination half-life of risperidone was 1.0 h, and mean residence times were 1.5 h for risperidone and 2.5 h for its 9-hydroxy metabolite. Plasma levels of the radioactivity increased dose proportionally between 0.02 and 1.3 mg/kg. Risperidone was rapidly distributed to brain tissues. The elimination of the radioactivity from the frontal cortex and striatum—brain regions with high concentrations of 5-HT2 or dopamine-D2 receptors—became more gradual with decreasing dose levels. After a subcutaneous dose of 0.02 mg/kg, the ED50 for central 5-HT2 antagonism in male rats, half-lives in frontal cortex and striatum were 3–4 h for risperidone, whereas mean residence times were 4–6 h for risperidone and about 12 h for 9-hydroxy-risperidone. These half-lives and mean residence times were 3–5 times longer than in plasma and in cerebellum, a region with very low concentrations of 5-HT2 and D2 receptors. Frontal cortex and striatum to plasma concentration ratios increased during the experiment. The distribution of 9-hydroxy-risperidone to the different brain regions, including frontal cortex and striatum, was more limited than that of risperidone itself. This indicated that 9-hydroxy-risperidone contributes to the in vivo activity of risperidone, but to a smaller extent than would be predicted from plasma levels. AUCs of both active compounds in frontal cortex and striatum were 10–18 times higher than those in cerebellum. No retention of metabolites other than 9-hydroxy-risperidone was observed in any of the brain regions investigated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02245444
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  • 115
    Electronic Resource
    Electronic Resource
    Discriminative stimulus properties of cocaine: modulation by dopamine D1 receptors in the nucleus accumbens (1994)
    Springer
    Psychopharmacology 115 (1994), S. 110-114 
    Details
    ISSN: 1432-2072
    Keywords: Cocaine ; Drug discrimination ; Nucleus accumbens ; Dopamine D1 and D2 receptors ; Microinjection ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Dopamine (DA) D1 and D2 receptors are involved in mediating the behavioral effects of cocaine, including its discriminative stimulus properties. The purpose of the present study was to investigate the role of the nucleus accumbens and, in particular, accum bens DA D1 receptors in modulating the stimulus effects of cocaine. Thus, rats were trained to discriminate cocaine (10 mg/kg, IP) from saline using a two-lever, water-reinforced FR 20 drug discrimination task. In substitution tests, systemic (IP) administration of cocaine (0.625–20 mg/kg) produced a dose-related increase in cocaine-appropriate responding. Microinjections of cocaine (2.5–40 µg) into the nucleus accumbens also engendered dose-dependent and complete substitutions (〉 80% drug-lever responding) for the systemic training dose of cocaine, whereas intra-accumbens artificial cerebrospinal fluid (1 µl/side) produced primarily saline-appropriate responding. In antagonism tests, pretreatment with the DA D1 antagonist SCH 23390 (3–12 µg/kg) completely antagonized (〈20% drug-lever responding) a dose of cocaine (5 mg/kg) that produced greater than 90% cocaine-lever responding when given alone. Additionally, intra-accumbens injections of SCH 23390 (0.025–0.4 µg) prior to systemic cocaine (5 mg/kg) also significantly blocked the cocaine stimulus. The present results confirm the importance of the nucleus accumbens in mediating the discriminative stimulus properties of cocaine and suggest a primary role of accumbens DA D1 receptors in modulating this behavior.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02244759
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    Evaluation of the discriminative stimulus effects of the novel sedative-hypnotic CL 284,846 (1994)
    Springer
    Psychopharmacology 115 (1994), S. 289-296 
    Details
    ISSN: 1432-2072
    Keywords: CL 284,846 ; Drug discrimination ; Sedative ; Hypnotic ; Anxiolytic ; Rat ; Benzodiazepine receptors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract CL 284,846,N-[3-(3-cyanopyrazolo[1, 5-a]pyrimidin-7-yl)phenyl)]-N-ethylacetamide, is a novel non-benzodiazepine sedative-hypnotic with benzodiazepine-like sedative effects, but with less apparent liability for accompanying undesired side effects. In an effort to further characterize its pharmacological activity, CL 284,846 (3.0 mg/kg, IP, 30 min pretreatment) was established as a discriminative stimulus (DS) in rats (n=7). CL 284,846 (0.3–10.0 mg/kg) showed a dose-related increase in drug-appropriate responding up to the training dose and a dose-related decrease in response rate. The benzodiazepine agonist triazolam (0.1–1.0 mg/kg), the benzodiazepine partial agonist Ro 17-1812 (0.3–3.0 mg/kg) and the triazolopyridazine CL 218,872 (1.0–3.0 mg/kg) substituted for CL 284,846 in all rats, whereas the imidazopyridines zolpidem (3.0–10.0 mg/kg) and alpidem (10.0–30.0 mg/kg), the benzodiazepine partial agonist bretazenil (0.03–10.0 mg/kg) and the novel putative anxiolytic CL 273,547 (10.0–56.0 mg/kg) substituted in most, but not all, rats. Ro 17-1812, bretazenil, and CL 218,872 had no effect on response rate while the other drugs showed a concomitant decrease in rate. The 5-HT1A agonist buspirone (1.0–10.0 mg/kg) and the barbiturate pentobarbital (3.0–17.0 mg/kg) failed to substitute for CL 284,846 up to rate-decreasing doses. The benzodiazepine antagonist flumazenil (3.0–10.0 mg/kg) blocked the DS effects of CL 284,846 in most rats with no effect on response rate. Taken together, these results suggest that the DS effects of CL 284,846 are mediated via benzodiazepine receptors; however, the DS profile of CL 284,846 remains distinct from both benzodiazepine and non-benzodiazepine sedative-hypnotic drugs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02245068
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    Caffeine augmentation of electroconvulsive seizures (1994)
    Springer
    Psychopharmacology 115 (1994), S. 320-324 
    Details
    ISSN: 1432-2072
    Keywords: Caffeine ; Electroconvulsive shock ; Seizure ; Rat ; Electroencephalography ; Convulsions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Caffeine has been used clinically to increase seizure length in electroconvulsive treatment (ECT). The present study was designed to establish an animal model of caffeine-augmented seizures for further study of mechanisms and effects of pharmacological manipulation of seizure length. Increasing doses of caffeine (0–200 mg/kg, IP) were given before electroconvulsive stimulation (ECS) in rats and resulting seizure lengths were quantified by timing of classical tonic-clonic convulsive movements. With this paradigm, caffeine led to a dose-dependent increase in seizure duration. This proconvulsant action of caffeine was detectable within 1 min after dosing, persisted for at least 230 min and was reversible. The results suggest that seizure length is a practicable measure in pharmacological modification of electroconvulsive seizures. They also suggest that pharmacologically-modified ECS can be modeled effectively in animals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02245072
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    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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    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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    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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    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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    An examination of the behavioural specificity of hypophagia induced by 5-HT1B, 5-HT1C and 5-HT2 receptor agonists using the post-prandial satiety sequence in rats (1994)
    Springer
    Psychopharmacology 113 (1994), S. 369-377 
    Details
    ISSN: 1432-2072
    Keywords: 5-HT1B ; 5-HT1C ; 5-HT2 receptors ; Feeding ; Satiety sequence ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Previous studies have shown that administration of 5-HT1B, 5-HT1C or 5-HT2 agonists decreases food intake in rats. However, it has not been established whether these drugs induce satiety or decrease feeding by a non-specific mechanism. In the present study the post-prandial satiety sequence was used to characterise the actions of the 5-HT2 receptor agonist, 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI), the 5-HT1B/5-HT1C receptor agonists, 1-(3-chorophenyl) piperazine (mCPP) and 1-[3-(trifluoromethyl)phenyl] piperazine (TFMPP), and the 5-HT1B agonist, 5-methoxy-3-(1,2,3,6-tetrahydro-4-pyridinyl)H-indole (RU 24969), on feeding in rats. All four compounds reduced food intake in rats that had been food deprived overnight. The 5-HT1B/5-HT1C agonists, TFMPP (at a dose of 1.0 mg/kg) and mCPP (at a dose of 3.0 mg/kg), appeared to produce satiety as their effects on the satiety sequence were similar to those induced by a food pre-load. In contrast, the 5-HT1B agonist RU 24969 and the 5-HT2 agonist DOI did not produce behavioural profiles that resembled satiety. Thus, RU 24969 elevated active behaviours and did not accelerate resting whereas DOI appeared to induce hypophagia by a non-specific fragmentation of behaviour. The results suggest that simultaneous activation of 5-HT1B and 5-HT1C receptors may be sufficient to elicit behaviourally specific satiety in the rat. In contrast, selective activation of 5-HT2 receptors does not induce satiety but elicits active behaviours and decreases feeding by response competition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02245211
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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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    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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    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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    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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    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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    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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    Effects of chronic phenylpropanolamine infusion and termination on body weight, food consumption and water consumption in rats (1994)
    Springer
    Psychopharmacology 114 (1994), S. 513-519 
    Details
    ISSN: 1432-2072
    Keywords: Phenylpropanolamine ; Body weight ; Food consumption ; Water consumption ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The present study determined the effect of chronic PPA infusion and withdrawal on weight regulation. Male Sprague-Dawley rats received PPA (0, 90 or 180 mg/kg) via miniosmotic pumps for 2 weeks. Body weight and food and water consumption were measured daily before, during, and for 2 weeks after PPA infusion. Additionally, body weight was measured once 6 weeks after the last day of drug administration. PPA infusion produced dose-dependent reductions in body weight and food consumption throughout drug administration. During the first week of PPA termination, food consumption returned to control levels; however, body weights of drug-treated animals remained below those of controls throughout the 6-week post-drug period. PPA depressed water intake during the first week of drug administration, but tolerance to this effect developed by the second week of administration. These results suggest chronic PPA infusion produces persistent appetite suppression and weight loss and that discontinuation of PPA does not result in hyperphagia or rapid weight gain. These findings may have clinical significance for the many individuals who wish to lose weight but have difficulty reducing intake without pharmacologic assistance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02249344
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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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  • 132
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    Evidence for altered α2-adrenoceptor function following isolation-rearing in the rat (1994)
    Springer
    Psychopharmacology 116 (1994), S. 183-190 
    Details
    ISSN: 1432-2072
    Keywords: Isolation rearing ; α2-Adrenoceptor ; Clonidine ; Mydriasis ; Hypoactivity ; [3H]-Idazoxan binding ; cAMP ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This study investigated central α2-adrenoceptor function in differentially reared rats. Rats reared from weaning were either housed singly or in groups of five. Measurements of spontaneous ambulatory activity at 4 weeks postweaning showed that isolates were more hyperactive on exposure to a novel environment than grouped rats. α2-Adrenoceptors were investigated using α2-adrenoceptor agonist-induced behaviours, [3H]-idazoxan binding and measurement of forskolin-stimulated cyclic AMP accumulation. Clonidine (0.001–1.0 mg/kg IP) induced mydriasis in both groups with no difference observed in the response between the isolation and group-reared animals. Clonidine (0.01–0.5 mg/kg IP) induced hypoactivity in both groups, with the effect significantly greater in the isolation-reared rats. Idazoxan markedly attenuated both responses, confirming their induction by α2-adrenoceptor stimulation. Clonidine-induced hypoactivity and mydriasis are mediated by pre- and postsynaptic α2-adrenoceptors, respectively; therefore the results suggest rats reared in isolation have enhanced presynaptic but unchanged postsynaptic α2-adrenoceptor function. Saturation binding experiments using [3H]-idazoxan were undertaken to determine α2-adrenoceptor number (Bmax) and affinity (Kd) in membranes prepared from the frontal cortex and hippocampus. Analysis of binding data revealed an increase in receptor number in the hippocampus of isolates. Cyclic AMP accumulation was measured in hippocampal slices from differentially reared rats. Isolation-rearing did not affect cyclic AMP accumulation in response to stimulation by forskolin (30 µM). However, the selective α2-adrenoceptor agonist, UK14304, produced a significantly greater inhibition of cyclic AMP accumulation in slices from isolated rats, confirming changes in α2-adrenoceptor function following isolation rearing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02245061
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    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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  • 134
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    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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    Stereospecific reversal of stress-induced anhedonia by mianserin and its (+)-enantiomer (1994)
    Springer
    Psychopharmacology 116 (1994), S. 523-528 
    Details
    ISSN: 1432-2072
    Keywords: Chronic mild stress ; Anhedonia ; Sucrose drinking ; Place conditioning ; Mianserin ; (+)-Mianserin ; Dopamine ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Chronic sequential exposure to a variety of mild unpredictable stressors has previously been found to depress the consumption of a dilute (1%) sucrose solution and to inhibit food-induced place preference conditioning. In the present study, using a simplified version of the mild stress procedure, the decreased sucrose intake was reversed by chronic (4 weeks) treatment with the atypical antidepressant mianserin. The racemic compound (±)-mianserin (5 mg/kg per day) and one of its enantiomers, (+)-mianserin (2.5 mg/kg) were effective in this model; a lower dose of (±)-mianserin (2.5 mg/kg), and the other enantiomer, (−)-mianserin (2.5 mg/kg), were ineffective. Vehicle-treated stressed animals were also subsensitive to food reward in the place conditioning procedure: normal place preference conditioning was reinstated by chronic treatment with (±)-mianserin (5 mg/kg) or (+)-mianserin, but not by the lower dose of (±)-mianserin (2.5 mg/kg) or by (−)-mianserin. Raclopride (100 µg/kg) reinstated the decrease in sucrose intake in stressed animals successfully treated with (±)- or (+)-mianserin. The results suggest that (+)-mianserin is the active enantiomer in reversing chronic mild stress-induced anhedonia, and further support the hypothesis of a dopaminergic mechanism of antidepressant action in this paradigm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02247488
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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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    Effects of the calcium antagonist isradipine on cocaine intravenous self-administration in rats (1994)
    Springer
    Psychopharmacology 113 (1994), S. 378-380 
    Details
    ISSN: 1432-2072
    Keywords: Cocaine ; Self-administration ; Calcium antagonists ; Isradipine ; Dopamine ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effect of isradipine, a dihydropyridine calcium antagonist, on cocaine intravenous self-administration in rats was investigated. Administration of (±)isradipine (1.25–5 mg/kg SC) 2 h before the cocaine self-administration session induced a significant and dose-dependent increase in the number of coacine injections with respect to basal values. This effect was sterospecific, with the (+) form of isradipine being active, while the (−) stereoisomer was ineffective. These results suggest that isradipine antagonizes the rewarding properties of cocaine, possibly by inhibiting those dopaminergic systems related to reward mechanisms. These results further indicate a possible use of isradipine, or structurally similar compounds, in the treatment of cocaine related disorders.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02245212
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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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  • 139
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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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  • 140
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    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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    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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    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.
    Type of Medium: Electronic Resource
    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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    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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    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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  • 147
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    Post-irradiation bladder dysfunction: muscle strip findings (1994)
    Springer
    Urological research 22 (1994), S. 51-55 
    Details
    ISSN: 1434-0879
    Keywords: Bladder dysfunction ; Muscle strip ; Rat ; X-irradiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Strips of rat detrusor muscle were studied in an organ bath 6 months after X-irradiation at doses of 15 and 25 Gy; cystometric studies in these animals had shown a persistent and significant reduction in compliance. The organ bath study demonstrated an increase in the purinergie sensitivity of irradiated detrusor muscle as compared with control. This was significant: p〈0.0145 for the 25 Gy dose group (n=8) and p〈0.0456 for the 15 Gy group (n=8) at an α,β-methylene-ATP concentration of 10-4 M (Mann-Whitney U-Test). There was no difference in sensitivity to cholinergic or noradrenergic stimulation, or to electrical stimulation of the transmural nerves. The finding of purinergic hypersensitivity in irradiated muscle, coupled with ultrastructural evidence of a neural injury, raises the interesting possibility that a denervation super-sensitivity phenomenon may contribute to the pathophysiology of post-irradiation bladder dysfunction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00431549
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  • 148
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    Pyelonephritis: renal urokinase and sialidase (neuraminidase) activity in rats fed a standard laboratory diet (1994)
    Springer
    Urological research 22 (1994), S. 57-60 
    Details
    ISSN: 1434-0879
    Keywords: Kidney ; Pyelonephritis ; Rat ; Sialidase (neuraminidase) ; Urokinase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Renal stone formation can be caused by many different and varied disturbances, some of which are poorly understood. The relationship between urinary infection and renal stone formation has not been completely clarified. It is argued that renal stones form primarily as a consequence of the hydrolysis of urea by the bacterial enzyme urease. However, no explanation is given for microorganisms that produce urease only occasionally or not at all. The question arises as to wheter the infection-induced microorganisms might not be playing a double role in renal stone formation by not only producting urease, but also by affecting in vivo urokinase (UK) and sialidase (SA) activity. With this in mind, the effect of Escherichia coli on renal UK and SA activity has been studied in male rats with a normal diet. The renal UK (P=0.208) and SA (P=0.2135) activities did not differ significantly between the two kidneys of the same rat. In contrast, when drainage from one kidney of a rat was externally obstructed, the UK and SA activities differed significantly between kidneys (P〈0.015). An increase in UK (r=0.6456, P〈0.0001) and SA (r=0.7507, P〈0.0001) activity was observed over time in the obstructed kidney. Subcutaneous injections with E. coli reduced the UK activity of the obstructed kidney significantly (p=0.0171). However, the SA activity remained the same (P=0.3929). This decrease in the UK activity in the presence of microorganisms may result in an increase in the uromucoid concentration, leading to renal stone formation in the presence of increased salt precipitation on the uromucoid as caused by the urease producing microorganisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00431551
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  • 149
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    The effect of active immunization against gonadotropin-releasing hormone on the ultrastructure of the rat ventral prostate (1994)
    Springer
    Urological research 22 (1994), S. 107-113 
    Details
    ISSN: 1434-0879
    Keywords: GnRH-DT vaccine ; Testosterone ; Ultrastructure ; Rat ; Prostate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To evaluate the effects of active immunization against gonadotropin-releasing hormone (GnRH) on the ultrastructure of the rat ventral prostate, male Sprague-Dawley rats received three consecutive intramuscular injections of 10 μg/100g body weight (D-Lys6)-GnRH-diphtheria toxoid conjugate (GnRH-DT vaccine). Following immunization, test animals developed sufficiently high antibody titres to block the pituitary gonadal axis. Consequently testosterone values dropped to the levels in castrates. This therapy leads to atrophy of the prostate. Following immunization a strong immunological response, indicating the presence of considerable amounts of a GnRH-like peptide, was observed in the ventral prostates as early as 14 days after the first injection of GnRH-DT. Immunoneutralisation of GnRH-like activity may contribute to the effects observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00311001
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  • 150
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    Elevated concentrations of the β-subunit of S100 protein in renal cell tumors in rats (1994)
    Springer
    Urological research 22 (1994), S. 251-255 
    Details
    ISSN: 1434-0879
    Keywords: S100 protein ; Rat ; Carcinogenesis ; Renal neoplasms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Concentrations of α and β-subunits of S100 protein (S100-α and S100-β) in rat kidney neoplasms, including renal cell and mesenchymal tumors, were determined using a highly sensitive enzyme immunoassay, and both types immunohistochemically localized in tissue sections. Concentration of S100-α in each histological type of rat tumor were lower than in normal kidney, whereas levels of S100-β (mean±SE: 29.7±14.2 ng/mg protein, n=15) in renal cell tumors were significantly higher than in normal kidneys (0.55±0.06 ng/mg protein, n=7), or mesenchymal tumors (1.21±0.43 ng/mg protein, n=9). In normal rat kidney tissues S100-α was immunohistochemically positive in epithelial cells of the distal tubules, the thin limbs of loops of Henle, and the collecting ducts. No appreciable immunostaining for S100-β was found in any nephron segment. Both S100-α and S100-β were positive for renal cell tumors, indicating new appearance of the latter during renal carcinogenesis in rats.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00541902
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  • 151
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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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  • 152
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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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  • 153
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    Protein folding: Predicting predicting (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 19 (1994), S. 1-3 
    Details
    ISSN: 0887-3585
    Keywords: protein folding ; protein conformation ; Paracelsus award ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340190102
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  • 154
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    Structure of trichosanthin at 1.88 Å resolution (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 19 (1994), S. 4-13 
    Details
    ISSN: 0887-3585
    Keywords: trichosanthin ; ribosome-inactivating proteins ; crystal structure ; orthorhombic ; molecular replacement ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Trichosanthin (TCS) is one of the single chain ribosome-inactivating proteins (RIPs). The crystals of the orthorhombic form of trichosanthin have been obtained from a citrate buffer (pH 5.4) with KC1 as the precipitant. The crystal belongs to the space group P212121 with a = 38.31, b = 76.22, c = 79.21 Å. The structure was solved by molecular replacement method and refined using the programs XPLOR and PROLSQ to an R-factor of 0.191 for the reflections within the 6-1.88 Å resolution range. The bond length and bond angle in the protein molecule have root-mean-square deviations from ideal value of 0.013 Å and 3.3°, respectively. The refined model includes 247 residues and 197 water molecules. The TCS molecule consists of two structural domains. The large domain contains six α-helices, a six stranded sheet, and an antiparallel β-sheet. The small domain has a largest α-helix, which shows a distinct bend. The possible active site of the molecule located on the cleft between two domains was proposed. In the active site Arg-163 and Glu-160, Glu-189 and Arg-122 form two ion pairs, Glu-189 and Gln-156 are hydrogen bonded to each other. Three water molecules are bonded to the residues in the active site region. The structures of TCS molecule and ricin A-chain (RTA) superimpose quite well, showing that the structures of the two protein molecules are homologous. Comparison of the structures of the TCS molecule in this orthorhombic crystal with that in the monoclinic crystal indicates that there are no essential differences of the structures between the two protein crystals. © 1994 Wiley-Liss, Inc.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340190103
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  • 155
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    Crystallization and preliminary X-ray crystallographic analysis of phospholipid transfer protein from maize seedlings (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 19 (1994), S. 80-83 
    Details
    ISSN: 0887-3585
    Keywords: maize protein ; crystals ; X-ray diffraction ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Phospholipid transfer protein from maize seedlings has been crystallized using trisodium citrate as precipitant. The crystal belongs to the orthorhombic space group P212121 with unit cell dimensions of a = 24.46 Å, b = 49.97 Å, and c = 69.99 Å. The presence of one molecule in the asymmetric unit gives a crystal volume per protein mass (Vm) of 2.36 Å 3/Da and a solvent content of 48% by volume. The X-ray diffraction pattern extends at least to 1.6 Å Bragg spacing when exposed to both CuKα and synchrotron X-rays. A set of X-ray data to approximately 1.9 Å Bragg spacing has been collected from a native crystal. © 1994 Wiley-Liss, Inc.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340190111
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  • 156
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    α-Helix-forming propensities in peptides and proteins (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 19 (1994), S. 85-97 
    Details
    ISSN: 0887-3585
    Keywords: protein conformation ; secondary structure ; protein folding ; helix stability ; helix formation ; conformational entropy ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Much effort has been invested in seeking to understand the thermodynamic basis of helix stability in both peptides and proteins. Recently, several groups have measured the helix-forming propensities of individual residues (Lyu, P. C., Liff, M. I., Marky, L. A., Kallenbach, N. R. Science 250:669-673, 1990; O'Neil, K. T., DeGrado, W. F. Science 250:646-651, 1990; Padmanabhan, S., Marqusee, S., Ridgeway, T., Laue, T. M., Baldwin, R. L. Nature (London) 344:268-270, 1990). Using Monte Carlo computer simulations, we tested the hypothesis that these differences in measured helix-forming propensity are due primarily to loss of side chain conformational entropy upon helix formation (Creamer, T. P., Rose, G. D. Proc. Natl. Acad. Sci. U.S.A. 89:5937-5941, 1992). Our previous study employed a rigid helix backbone, which is here generalized to a completely flexible helix model in order to ensure that earlier results were not a methodological artifact. Using this flexible model, side chain rotamer distributions and entropy losses are calculated and shown to agree with those obtained earlier. We note that the side chain conformational entropy calculated for Trp in our previous study was in error; a corrected value is presented. Extending earlier work, calculated entropy losses are found to correlate strongly with recent helix propensity scales derived from substitutions made within protein helices (Horovitz, A., Matthews, J. M., Fersht, A. R. J. Mol. Biol. 227:560-568, 1992; Blaber, M., Zhang, X.-J., Matthews, B. M. Science 260:1637-1640, 1993). In contrast, little correlation is found between these helix propensity scales and the accessible surface area buried upon formation of a model polyalanyl α-helix. Taken in sum, our results indicate that loss of side chain entropy is a major determinant of the helix-forming tendency of residues in both peptide and protein helices. © 1994 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340190202
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  • 157
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    Searching protein structure databases has come of age (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 19 (1994), S. 165-173 
    Details
    ISSN: 0887-3585
    Keywords: algoriths ; structure alignment ; Protein Data Bank ; protein superfamilies ; structural homology ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The number of protein structures known in atomic detail has increased from one in 1960 (Kendrew, J. C., Strandberg, B. E., Hart, R. G., Davies, D. R., Phillips, D. C., Shore, V. C. Nature (London) 185:422-427, 1960) to more than 1000 in 1994. The rate at which new structures are being published exceeds one a day as a result of recent advances in protein engineering, crystallography, and spectroscopy. More and more frequently, a newly determined structure is similar in fold to a known one, even when no sequence similarity is detectable. A new generation of computer algorithms has now been developed that allows routine comparison of a protein structure with the database of all known structures. Such structure database searches are already used daily and they are beginning to rival sequence database searches as a tool for discovering biologically interesting relationships. © 1994 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/prot.340190302
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  • 158
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    HOOK: A program for finding novel molecular architectures that satisfy the chemical and steric requirements of a macromolecule binding site (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 19 (1994), S. 199-221 
    Details
    ISSN: 0887-3585
    Keywords: multicopy simulation search ; rational drug design ; database search ; computer-aided design ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A program (HOOK) is described for generating potential ligands that satisfy the chemical and steric requirements of the binding region of a macromolecule. Functional group sites with defined positions and orientations are derived from known ligand structures or the multicopy simulation search (MCSS) method (Miranker, A., Karplus, M. Proteins 11:29-34, 1991). HOOK places molecular “skeletons” from a database into the protein binding region by making bonds between sites (“hooks”) on the skeleton and functional groups. The nonpolar interactions with the binding region of candidate molecules are assessed by use of a simplified van der Waals potential. The method is illustrated by constructing ligands for the sialic acid binding site of the hemagglutinin from the influenza A virus and the active site of chloramphenicol acetyltransferase. Aspects of the HOOK program that lead to a highly efficient search of 105 or more skeletons for binding to 102 or more functional group minima are outlined. © 1994 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340190305
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  • 159
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    Structural modeling and electrostatic properties of aspartate transcarbamylase from Saccharomyces cerevisiae (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 19 (1994), S. 230-243 
    Details
    ISSN: 0887-3585
    Keywords: aspartate transcarbamylase ; multienzyme complex ; comparative structure modeling ; allosteric enzymes ; molecular evolution ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: In Saccharomyces cerevisiae the first two reactions of the pyrimidine pathway are catalyzed by a multifunctional protein which possesses carbamylphosphate synthetase and aspartate transcarbamylase activities. Genetic and proteolysis studies suggested that the ATCase activity is carried out by an independently folded domain. In order to provide structural information for ongoing mutagenesis studies, a model of the three-dimensional structure of this domain was generated on the basis of the known X-ray structure of the related catalytic subunit from E. coli ATCase. First, a model of the catalytic monomer was built and refined by energy minimization. In this structure, the conserved residues between the two proteins were found to constitute the hydrophobic core whereas almost all the mutated residues are located at the surface. Then, a trimeric structure was generated in order to build the active site as it lies at the interface between adjacent chains in the E. coli catalytic trimer. After docking a bisubstrate analog into the active site, the whole structure was energy minimized to regularize the interactions at the contact areas between subunits. The resulting model is very similar to that obtained for the E. coli catalytic trimer by X-ray crystallography, with a remarkable conservation of the structure of the active site and its vicinity. Most of the interdomain and intersubunit interactions that are essential for the stability of the E. coli catalytic trimer are maintained in the yeast enzyme even though there is only 42% identity between the two sequences. Free energy calculations indicate that the trimeric assembly is more stable than the monomeric form. Moreover an insertion of four amino acids is localized in a loop which, in E. coli ATCase, is at the surface of the protein. This insertion exposes hydrophobic residues to the solvent. Interestingly, such an insertion is present in all the eukaryotic ATCase genes sequenced so far, suggesting that this region is interacting with another domain of the multifunctional protein. © 1994 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340190307
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  • 160
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    Masthead (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 19 (1994) 
    Details
    ISSN: 0887-3585
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340190401
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  • 161
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    Where is NMR taking us?This article is a US Government work and, as such, is in the public domain in the United States of America. (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 19 (1994), S. 273-276 
    Details
    ISSN: 0887-3585
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340190402
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  • 162
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    Crystallographic analysis of oxygenated and deoxygenated states of arthropod hemocyanin shows unusual differences (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 19 (1994), S. 302-309 
    Details
    ISSN: 0887-3585
    Keywords: dinuclear copper site ; hemocyanin ; oxygen binding ; allosteric regulation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The X-ray structure of an oxygenated hemocyanin molecule, subunit II of Limulus polyphemus hemocyanin, was determined at 2.4 Å resolution and refined to a crystallographic R-factor of 17.1%. The 73-kDa subunit crystallizes with the symmetry of the space group R32 with one subunit per asymmetric unit forming hexamers with 32 point group symmetry. Molecular oxygen is bound to a dinuclear copper center in the protein's second domain, symmetrically between and equidistant from the two copper atoms. The copper-copper distance in oxygenated Limulus hemocyanin is 3.6 ± 0.2 Å, which is surprisingly 1 Å less than that seen previously in deoxygenated Limulus polyphemus subunit II hemocyanin (Hazes et al., Protein Sci. 2:597, 1993). Away from the oxygen binding sites, the tertiary and quaternary structures of oxygenated and deoxygenated Limulus subunit II hemocyanins are quite similar. A major difference in tertiary structures is seen, however, when the Limulus structures are compared with deoxygenated Panulirus interruptus hemocyanin (Volbeda, A., Hol, W. G. J. J. Mol. Biol. 209:249, 1989) where the position of domain 1 is rotated by 8° with respect to domains 2 and 3. We postulate this rotation plays an important role in cooperativity and regulation of oxygen affinity in all arthropod hemocyanins. © 1994 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/prot.340190405
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  • 163
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    Masthead (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 20 (1994) 
    Details
    ISSN: 0887-3585
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340200301
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  • 164
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    Preliminary crystallographic analysis of an enzyme involved in erythromycin biosynthesis: Cytochrome P450eryF (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 20 (1994), S. 197-201 
    Details
    ISSN: 0887-3585
    Keywords: cytochrome P450 ; erythromycin ; P450eryF ; crystallization ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Cytochrome P450eryF was overexpressed in Escherichia coli and purified in high yield. Crystals of the protein in the presence of the substrate, 6-deoxyerythronolide B, have been obtained by the hanging drop vapor diffusion method, using polyethylene glycol 4000 as a precipitant. The crystals belong to the orthorhombic space group P212121 with unit cell dimensions of a = 54.16 Å, b = 79.67 Å, and c = 99.48 Å and one molecule per asymmetric unit. A complete native data set has been collected to a resolution of 2.1 Å, and anomalous dispersion difference Patterson maps have revealed the location of the single heme iron atom. © 1994 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340200210
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  • 165
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    Pyrrolidone carboxyl peptidase (Pcp): An enzyme that removes pyroglutamic acid (pGlu) from pGlu-peptides and pGlu-proteins (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 20 (1994), S. 34-51 
    Details
    ISSN: 0887-3585
    Keywords: enzymology ; protein structure ; biochemical properties ; gene characterization ; bacterial diagnosis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Pyrrolidone carboxyl peptidase (EC 3.4.11.8) is an exopeptidase commonly called PYRase, which hydrolytically removes the pGlu from pGlu-peptides or pGlu-proteins.pGlu also known as pyrrolidone carboxylic acid may occur naturally by an enzymatic procedure or may occur as an artifact in proteins or peptides. The enzymatic synthesis of pGlu suggests that this residue may have important biological and physiological functions. Several studies are consistent with this supposition.PYRase has been found in a variety of bacteria, and in plant, animal, and human tissues For over two decades, biochemical and enzymatic properties of PYRase have been investigated. At least two classes of PYRase have been characterized. The first one includes the bacterial and animal type I PYRases and the second one the animal type II and serum PYRases. Enzymes from these two classes present differences in their molecular weight and in their enzymatic properties.Recently, the genes of PYRases from four bacteria, have been cloned and characterized, allowing the study of the primary structure of these enzymes, and their over-expression in heterelogous organisms. Comparison of the primary structure of these enzymes revealed striking homologies.Type I PYRases and bacterial PYRases are generally soluble enzymes, whereas type II PYRases are membrane-bound enzymes. PYRase II appears to play as important a physiological role as other neuropeptide degrading enzymes. However, the role of type I and bacterial PYRases remains unclear.The primary application of PYRase has been its utilization for some protein or peptide sequencing. Development of chromogenic substrates for this enzyme has allowed its use in bacterial diagnosis. © 1994 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/prot.340200106
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  • 166
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    Structure and dynamics of the neutrophil defensins NP-2, NP-5, and HNP-1: NMR studies of amide hydrogen exchange kinetics (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 20 (1994), S. 52-67 
    Details
    ISSN: 0887-3585
    Keywords: nuclear magnetic resonance ; defensin ; hydrogen exchange ; antimicrobial peptides ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The exchange kinetics for the slowly exchanging amide hydrogens in three defensins, rabbit NP-2, rabbit NP-5, and human HNP-1, have been measured over a range of pH at 25°C using 1D and 2D NMR methods. These NHs have exchange rates 102 to 105 times slower than rates from unstructured model peptides. The observed distribution of exchange rates under these conditions can be rationalized by intramolecular hydrogen bonding of the individual NHs, solvent accessibility of the NHs, and local fluctuations in structure. The temperature dependencies of NH chemical shifts (NH temperature coefficients) were measured for the defensins and these values are consistent with the defensin structure. A comparison is made between NH exchange kinetics, NH solvent accessibility, and NH temperature coefficients of the defensins and other globular proteins. Titration of the histidine side chain in NP-2 was examined and the results are mapped to the three-dimensional structure. © 1994 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340200107
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    A Connected-cluster of hydration around myoglobin: Correlation between molecular dynamics simulations and experiment (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 18 (1994), S. 133-147 
    Details
    ISSN: 0887-3585
    Keywords: myoglobin ; simulation ; hydration ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: An analysis of a molecular dynamics simulation of metmyoglobin in an explicit solvent environment of 3,128 water molecules has been performed. Both statics and dynamics of the protein-solvent interface are addressed in a comparison with experiment. Three-dimensional density distributions, temperature factors, and occupancy weights are computed for the solvent by using the trajectory coordinates. Analysis of the hydration leads to the localization of more than 500 hydration sites distributed into multiple layers of solvation located between 2.6 and 6.8 Å from the atomic protein surface. After locating the local solvent density maxima or hydration sites we conclude that water molecules of hydration positions and hydration sites are distinct concepts. Both global and detailed properties of the hydration cluster around myoglobin are compared with recent neutron and X-ray data on myoglobin. Questions arising from differences between X-ray and neutron data concerning the locations of the protein-bound water are investigated. Analysis of water site differences found from X-ray and neutron experiments compared with our simulation shows that the simulation gives a way to unify the hydration picture given by the two experiments. © 1994 John Wiley & Sons, Inc.
    Additional Material: 13 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340180206
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    Evaluation of the conformational free energies of loops in proteins (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 18 (1994), S. 119-132 
    Details
    ISSN: 0887-3585
    Keywords: electrostatics ; protein conformation ; DelPhi ; hydrophobicity ; RNase H ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: In this paper we discuss the problem of including solvation free energies in evaluating the relative stabilities of loops in proteins. A conformational search based on a gas-phase potential function is used to generate a large number of trial conformations. As has been found previously, the energy minimization step in this process tends to pack charged and polar side chains against the protein surface, resulting in conformations which are unstable in the aqueous phase. Various solvation models can easily identify such structures. In order to provide a more severe test of solvation models, gas phase conformations were generated in which side chains were kept extended so as to maximize their interaction with the solvent. The free energies of these conformations were compared to that calculated for the crystal structure in three loops of the protein E. coli RNase H, with lengths of 7, 8, and 9 residues. Free energies were evaluated with a finite difference Poisson-Boltzmann (FDPB) calculation for electrostatics and a surface area-based term for nonpolar contributions. These were added to a gas-phase potential function. A free energy function based on atomic solvation parameters was also tested. Both functions were quite successful in selecting, based on a free energy criterion, conformations quite close to the crystal structure for two of the three loops. For one loop, which is involved in crystal contacts, conformations that are quite different from the crystal structure were also selected. A method to avoid precision problems associated with using the FDPB method to evaluate conformational free energies in proteins is described. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340180205
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    Crystallization and structural analysis of bullfrog red cell L-subunit ferritins (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 18 (1994), S. 107-118 
    Details
    ISSN: 0887-3585
    Keywords: protein crystallography ; four helix bundle ; iron ; macromolecular assembly ; regulation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Ferritin is a 24 subunit protein that controls biomineralization of iron in animals, bacteria, and plants. Rates of mineralization vary among members of the ferritin family, particularly between L and H type subunits of animal ferritins which are differentially expressed in various cell types. To examine ferritin from a highly differentiated cell type and to clarify the relationship between ferritin structure and function, bullfrog red cell L ferritin has been cloned, overexpressed in E. coli, and crystallized under two conditions. Crystals were obtained at high ionic strength in the presence of MnCl2 at a concentration comparable to that of the protein and in the presence of MgCl2 at a concentration much higher than that of the protein. Under both crystallization conditions, the crystals are tetragonal bipyramids in the space group F432 with unit cell dimensions a=b=c= 182 ± 0.5 Å. Crystals obtained in the presence of manganese and ammonium sulfate diffract to 1.9 Å, while those obtained in the presence of magnesium and sodium tartrate diffract to 1.6 Å. Isomorphous crystals have been obtained under similar conditions for a site-directed mutant with a reduced mineralization rate in which Glu-57, -58, -59, and -61 are all replaced by Ala. The structure of wild type L-subunit with magnesium has been solved by molecular replacement using the calcium salt of human liver H subunit (Lawson et al., Nature (London) 349:541-544, 1991) as the model. The crystallographic R factor for the 6-2.2 Å shell is 0.21. The overall fold of human H and bullfrog L ferritins is similar with an rms difference in backbone atomic positions of 0.97 Å. The largest structural differences occur in the D helix and the loop connecting the D and E helices of the four helix bundle. Because red cell L ferritin and liver H ferritin show differences in both rates of mineralization and three-dimensional structure, more detailed comparisons of these structures are likely to shed new light on the relationship between conformation and function. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340180204
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    Distribution function implied dynamics versus residence times and correlations: Solvation shells of myoglobin (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 18 (1994), S. 148-160 
    Details
    ISSN: 0887-3585
    Keywords: myoglobin ; solvation ; dynamics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The dynamics of water at the protein-solvent interface is investigated through the analysis of a molecular dynamics simulation of metmyoglobin in explicit aqueous environment. Distribution implied dynamics, harmonic and quasiharmonic, are compared with the simulated macroscopic dynamics. The distinction between distinguishable solvent molecules and hydration sites developed in the previous paper is used. The simulated hydration region within 7 Å from the protein surface is analyzed using a set of 551 hydration sites characterized by occupancy weights and temperature B-factors determined from the simulation trajectory. The precision of the isotropic harmonic and anisotropic harmonic models for the description of proximal solvent fluctuations is examined. Residence times and dipole reorientation times of water around the protein surface are compared with NMR and ESR results. A correlation between diffraction experiment quantities such as the occupancy weights and temperature factors and the residence and correlation times resulting from magnetic resonance experiments is found via comparison with simulation. © 1994 John Wiley & Sons, Inc.
    Additional Material: 16 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340180207
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  • 171
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    Crystallization and preliminary structural studies of a chorismate mutase catalytic antibody complexed with a transition state analog (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 18 (1994), S. 198-200 
    Details
    ISSN: 0887-3585
    Keywords: catalytic antibody ; chorismate mutase ; crystallization ; X-ray diffraction ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The Fab′ fragment of a catalytic antibody with chorismate mutase activity has been crystallized as a complex with the transition-state analog hapten. The complex was crystallized by the vapor diffusion method using ammonium sulfate as the precipitant. The crystals belong to the orthorhombic space group P212121 with unit cell dimensions a = 37.1 Å, b = 63.3 Å, c = 178.5 Å, and there is one Fab' molecule per asymmetric unit. The crystals diffract X-rays to at least 3.0 Å and are suitable for X-ray crystallographic studies. © 1994 John Wiley & Sons, Inc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340180211
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  • 172
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    Structural analysis of two crystal forms of lentil lectin at 1.8 Å resolution (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 20 (1994), S. 330-346 
    Details
    ISSN: 0887-3585
    Keywords: lentil lectin ; legume lectin ; lectin ; side chain clusters ; sugar-protein interactions ; phosphate binding ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The structures of two crystal forms of lentil lectin are determined and refined at high resolution. Orthorhombic lentil lectin is refined at 1.80 Å resolution to anR-factor of 0.184 and monoclinic lentil lectin at 1.75 Å resolution to anR-factor of 0.175. These two structures are compared to each other and to the other available legume lectin structures. The monosaccharide binding pocket of each lectin monomer contains a tightly bound phosphate ion. This phosphate makes hydrogen bonding contacts with Asp-81β, Gly-99β, and Asn-125β, three residues that are highly conserved in most of the known legume lectin sequences and essential for monosaccharide recognition in all legume lectin crystal structures described thus far. A detailed analysis of the composition and properties of the hydrophobic contact network and hydrophobic nuclei in lentil lectin is presented. Contact map calculations reveal that dense clusters of nonpolar as well as polar side chains playa major role in secondary structure packing. This is illustrated by a large cluster of 24 mainly hydrophobic amino acids that is responsible for the majority of packing interactions between the two β-sheets. Another series of four smaller and less hydrophobic clusters is found to mediate the packing of a number of loop structures upon the front sheet. A very dense, but not very conserved cluster is found to stabilize the transition metal binding site. The highly conserved and invariant nonpolar residues are distributed asymmetrically over the protein. © 1994 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340200406
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  • 173
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    Helix packing in proteins: Prediction and energetic analysis of dimeric, trimeric, and tetrameric GCN4 coiled coil structures (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 20 (1994), S. 105-123 
    Details
    ISSN: 0887-3585
    Keywords: structure prediction ; helix to helix packing ; coiled coils ; leucine zippers ; heptad repeats ; molecular dynamics ; simulated annealing ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A simulated annealing method for atomic resolution structure prediction of α-helical coiled coil proteins is described which draws upon knowledge of the oligomerization state, the helix directionality, and the properties of heptad repeat sequences. Unknown structural parameters, such as the coiled coil twist angle and the side chain conformations, are heavily sampled while allowing for flexibility in the helix backbone geometry. Structures of the wild-type GCN4 dimer [O'Shea et al., Science 254:539-544, 1991] and a mutant tetramer [Harbury et al., Science 292:1401-1407, 1993] have been generated and compared with the X-ray crystal structures. The wild-type dimer model has a root mean square coordinate deviation from the crystal structure of 0.73 Å for nonhydrogen atoms in the dimerization interface. Structures of a mutant dimer and a mutant trimer have been predicted. Packing energetics were analyzed for core leucine and isoleucine side chains in dimeric and tetrameric coiled coils. Strong packing preferences were found in the dimers but not in the tetramers. Thus, packing in the dimer may be responsible for the switch from a two-stranded to a four-stranded coiled coil caused by the GCN4 leucine zipper mutations. © 1994 Wiley-Liss, Inc.
    Additional Material: 14 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340200202
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  • 174
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    A special-purpose computer for molecular dynamics: GRAPE-2A (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 20 (1994), S. 139-148 
    Details
    ISSN: 0887-3585
    Keywords: hardware ; molecular dynamics ; simulation ; special-purpose computer ; supercomputing ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Molecular dynamics simulations have been extensively used in research of proteins. Since these simulations are quite computer intensive, their acceleration is of main interest of the research. In molecular dynamics simulations, almost all computing time is consumed in calculating the forces between particles, e.g., Coulomb and van der Waals forces. We have designed and built GRAPE-2A (GRAvity PipE 2A), a special-purpose computer for use in simulations of classical many-body systems. GRAPE-2A calculates forces exerted on a particle from the other particles. GRAPE-2A can calculate force of an arbitrary functional form of a central force. The host computer, which is connected to GRAPE-2A through the VME bus, performs other calculations such as time integration. The peak speed of GRAPE-2A is 180 Mflops. We can also stimulate systems with periodic boundary conditions by the Ewald method, using GRAPE-2A and another special-purpose computer, WINE (Wave space INtegrator for the Ewald method). © 1994 Wiley-Liss, Inc.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340200204
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  • 175
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    Crystallization and preliminary crystallographic studies of the precursor and mature forms of a neutral lipase from the fungus Rhizopus delemar (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 18 (1994), S. 301-306 
    Details
    ISSN: 0887-3585
    Keywords: triglyceride lipase ; proenzyme ; molecular replacement ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A neutral lipase from the filamentous fungus Rhizopus delemar has been crystallized in both its proenzyme and mature forms. Although the latter crystallizes readily and produces a variety of crystal forms, only one was found to be suitable for X-ray studies. It is monoclinic (C2, a = 92.8 Å, b = 128.9 Å, c = 78.3 Å, β = 135.8) with two molecules in the asymmetric unit related by a noncrystallographic diad. The prolipase crystals are orthorhombic (P212121, with a = 79.8 Å, b = 115.2 Å, c = 73.0 Å) and also contain a pair of molecules in the asymmetric unit. Initial results of molecular replacement calculations using the refined coordinates of the related lipase from Rhizomucor miehei identified the correct orientations and positions of the protein molecules in the unit cells of crystals of both proenzyme and the mature form. © 1994 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340180311
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  • 176
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    Correlated mutations and residue contacts in proteins (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 18 (1994), S. 309-317 
    Details
    ISSN: 0887-3585
    Keywords: protein structure prediction ; predicted contact maps ; correlated mutations ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The maintenance of protein function and structure constrains the evolution of amino acid sequences. This fact can be exploited to interpret correlated mutations observed in a sequence family as an indication of probable physical contact in three dimensions. Here we present a simple and general method to analyze correlations in mutational behavior between different positions in a multiple sequence alignment. We then use these correlations to predict contact maps for each of 11 protein families and compare the result with the contacts determined by crystallography. For the most strongly correlated residue pairs predicted to be in contact, the prediction accuracy ranges from 37 to 68% and the improvement ratio relative to a random prediction from 1.4 to 5.1. Predicted contact maps can be used as input for the calculation of protein tertiary structure, either from sequence information alone or in combination with experimental information. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340180402
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  • 177
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    Expression, purification, and crystallization of restriction endonuclease PvuII with DNA containing its recognition site (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 19 (1994), S. 77-79 
    Details
    ISSN: 0887-3585
    Keywords: endonuclease overexpression ; crystallization ; X-ray diffraction ; protein-DNA complex ; Type II restriction enzyme ; vapor diffusion ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: We have overexpressed the type II restriction endonuclease PvuII (R.PvuII) in E. coli, prepared large amounts of the homogeneous enzyme, and crystallized it with an oligonucleotide carrying a PvuII recognition site. The cocrystals are orthorhombic space group P212121 with cell constants a = 95.8 Å, b = 86.3 Å, c = 48.5 Å, and diffract X-rays to at least 2.7 Å. There is a complex of two protein subunits and one oligonucleotide duplex in the asymmetric unit. © 1994 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340190110
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  • 178
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    Investigation of the functional interplay between the primary site and the subsite of RNase T1: Kinetic analysis of single and multiple mutants for modified substrates (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 18 (1994), S. 318-323 
    Details
    ISSN: 0887-3585
    Keywords: ribonuclease T1 ; functional cooperativity ; double mutant cycle ; subsite ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: We report on the functional cooperativity of the primary site and the sub-site of ribonuclease T1 (RNase T1; EC 3.1.27.3). The kinetic properties of the single Tyr-38-Phe and Asn-98-Ala mutants have been compared with those of the corresponding double mutant. The Tyr-38-Phe mutation has been used to probe enzyme-substrate interactions at the primary site; the Asn-98-Ala mutation monitors subsite interactions.1 In addition to the dinucleoside phosphate substrate GpC, we measured the kinetics for GpMe, a synthetic substrate in which the leaving nucleoside cytosine has been replaced by methanol. All data were combined in a triple mutant box to analyze the interplay between Tyr-38, Asn-98, and the leaving group. The free energy barriers to kcat, introduced by the single Tyr-38-Phe and Asn-98-Ala mutations are not additive in the corresponding double mutant. The energetic coupling between both mutations is independent of the binding of the leaving cytosine at the subsite. We conclude that the coupling of the Tyr-38-Phe and Asn-98-Ala mutations arises through distortion or reorientation of the 3′-guanylic acid moiety bound at the primary site. The experimental data indicate that the enzyme-substrate interactions beyond the scissile phosphodiester bond contribute to catalysis through the formation of new or improved contacts in going from ground state to transition state, which are functionally independent of primary site interactions. © 1994 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340180403
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  • 179
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    1.56 Å structure of mature truncated human fibroblast collagenase (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 19 (1994), S. 98-109 
    Details
    ISSN: 0887-3585
    Keywords: crystallography ; hydroxamate ; high resolution ; metalloproteinase ; zinc ; X-ray ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The X-ray crystal structure of a 19 kDa active fragment of human fibroblast collagenase has been determined by the multiple isomorphous replacement method and refined at 1.56 Å resolution to an R-factor of 17.4%. The current structure includes a bound hydroxamate inhibitor, 88 waters and three metal atoms (two zincs and a calcium). The overall topology of the enzyme, comprised of a five stranded β-sheet and three α-helices, is similar to the thermolysin-like metalloproteinases. There are some important differences between the collagenase and thermolysin families of enzymes. The active site zinc ligands are all histidines (His-218, His-222, and His-228). The presence of a second zinc ion in a structural role is a unique feature of the matrix metalloproteinases. The binding properties of the active site cleft are more dependent on the main chain conformation of the enzyme (and substrate) compared with thermolysin. A mechanism of action for peptide cleavage similar to that of thermolysin is proposed for fibroblast collagenase. © 1994 Wiley-Liss, Inc.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340190203
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    Kinetic study on myoglobin refolding monitored by five optical probe stopped-flow methods (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 19 (1994), S. 110-119 
    Details
    ISSN: 0887-3585
    Keywords: folding intermediate ; urea denaturation ; stopped-flow circular dichroism ; molten globule ; hemindicyanide ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The refolding kinetics of horse cyanometmyoglobin induced by concentration jump of urea was investigated by five optical probe stopped-flow methods: absorption at 422 nm, tryptophyl fluorescence at around 340 nm, circular dichroism (CD) at 222 nm, CD at 260 nm, and CD at 422 nm. In the refolding process, we detected three phases with rate constants of 〉 1 × 102 s-1, (4.5-9.3) S-1, and (2-5) × 10-3 s-1. In the fastest phase, a substantial amount of secondary structure (40%) is formed within the dead time of the CD stopped-flow apparatus (10.7 ms). The kinetic intermediate populated in the fastest phase is shown to capture a hemindicyanide, suggesting that a “heme pocket precursor” recognized by hemindicyanide must be constructed within the dead time. In the middle phase, most of secondary and tertiary structures, especially around the captured hemindicyanide, have been constructed. In the slowest phase, we detected a minor structural rearrangement accompanying the ligand-exchange reaction in the fifth coordination of ferric iron. We present a possible model for the refolding process of myoglobin in the presence of the heme group. © 1994 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340190204
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  • 181
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    Decoupling of melting domains in immobilized ribonuclease A (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 19 (1994), S. 120-131 
    Details
    ISSN: 0887-3585
    Keywords: enzymes ; protein immobilization ; microcalorimetry ; protein melting domains ; protein DSC ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Ribonuclease A has been immobilized on silica beads through glutaraldeyde-mediated chemical coupling in order to improve the stability of the protein against thermal denaturation. The thermodynamic and binding properties of the immobilized enzyme have been studied and compared with those of the free enzyme. The parameters describing the binding of the inhibitor 3′ -CMP (Ka and ΔH) as monitored by spectrophotometry and calorimetry were not significantly affected after immobilization. Conversely both the stability and unfolding mechanism drastically changed. Thermodynamic analysis of the DSC data suggests that uncoupling of protein domains has occurred as a consequence of the immobilization. The two state approximation of the protein unfolding process is not longer valid for the immobilized RNase. Protein stability strongly depends on the hydrophobicity properties of the support surface as well as on the presence of the inhibitor and pH. For example, after immobilization on a highly hydrophobic surface, the enzyme is partially in the unfolded state. The binding of a ligand is able to reorganize the protein structure into a native-like conformation. The refolding rates are different for the two protein domains and vary as a function of pH and presence of the inhibitor 3′-CMP. © 1994 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
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  • 182
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    Recognition of distantly related proteins through energy calculations (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 19 (1994), S. 132-140 
    Details
    ISSN: 0887-3585
    Keywords: distant protein folds ; sequence homology ; database searching ; profile analysis ; protein structure comparison ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A new method to detect remote relationships between protein sequences and known three-dimensional structures based on direct energy calculations and without reliance on statistics has been developed. The likelihood of a residue to occupy a given position on the structural template was represented by an estimate of the stabilization free energy made after explicit prediction of the substituted side chain conformation. The profile matrix derived from these energy values and modified by increasing the residue self-exchange values successfully predicted compatibility of heatshock protein and globin sequences with the three-dimensional structures of actin and phycocyanin, respectively, from a full protein sequence databank search. The high sensitivity of the method makes it a unique tool for predicting the three-dimensional fold for the rapidly growing number of protein sequences. © 1994 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340190206
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    Characterization of two crystal forms of Clostridium thermocellum endoglucanase CelC (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 19 (1994), S. 158-160 
    Details
    ISSN: 0887-3585
    Keywords: crystallization ; cellulases ; X-ray crystallography ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Endoglucanase CelC from Clostridium thermocellum expressed in Escherichia coli has been crystallized in two different crystal forms by the hanging drop method. Crystals of form I were grown with polyethylene glycol as a precipitant. They are orthorhombic, space group P212121, with cell dimensions a =51.4 Å, b =84.3 Å, and c =87.5 Å. Crystals of form II, obtained in ammonium sulfate solutions, belong to the tetragonal space group P41212 (or P43212) with cell dimensions of a = b = 130.7 Å and c = 69.6 Å. Diffraction data to 2.8 Å resolution were observed for both crystal forms with a rotating anode generator. Preliminary oscillation images of the orthorhombic form I crystals using a synchrotron radiation source show diffraction to 2.2 Å resolution, indicating that these crystals are suitable for high resolution crystallographic analysis. © 1994 Wiley-Liss, Inc.
    Additional Material: 1 Ill.
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    Masthead (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 19 (1994) 
    Details
    ISSN: 0887-3585
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340190301
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  • 185
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    The closed conformation of a highly flexible protein: The structure of E. coli adenylate kinase with bound AMP and AMPPNPThe structure is listed as 1ANK in the Brookhaven Protein Data Bank. (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 19 (1994), S. 183-198 
    Details
    ISSN: 0887-3585
    Keywords: X-ray crystallography ; Rfree ; ATP and AMP binding sites ; Mg2+ coordination ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The structure of E. coli adenylate kinase with bound AMP and AMPPNP at 2.0 Å resolution is presented. The protein crystallizes in space group C2 with two molecules in the asymmetric unit, and has been refined to an R factor of 20.1% and an Rfree of 31.6%. In the present structure, the protein is in the closed (globular) form with the large flexible lid domain covering the AMPPNP molecule. Within the protein, AMP and AMPPNP, an ATP analog, occupy the AMP and ATP sites respectively, which had been suggested by the most recent crystal structure of E. coli adenylate kinase with AP5A bound (Müller and Schulz, 1992, ref. 1) and prior fluorescence studies (Liang et al., 1991, ref. 2). The binding of substrates and the positions of the active site residues are compared between the present structure and the E. coli adenylate kinase/Ap5A structure. We failed to detect a peak in the density map corresponding to the Mg2+ ion which is required for catalysis, and its absence has been attributed to the use of ammonium sulfate in the crystallization solution. Finally, a comparison is made between the present structure and the structure of the heavy chain of muscle myosin. © 1994 Wiley-Liss, Inc.
    Additional Material: 13 Ill.
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  • 186
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    Conformational analysis of hemopexin by fourier-transform infrared and circular dichroism spectroscopy (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 20 (1994), S. 185-190 
    Details
    ISSN: 0887-3585
    Keywords: heme ; secondary structure ; conformation ; hemopexin ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Hemopexin is a serum glyco-protein that binds heme with the highest known affinity of any characterized heme-binding protein and plays an important role in receptormediated cellular heme uptake. Complete understanding of the function of hemopexin will require the elucidation of its molecular structure. Previous analysis of the secondary structure of hemopexin by far-UV circular dichroism (CD) failed due to the unusual positive ellipticity of this protein at 233 nm. In this paper, we present an examination of the structure of hemopexin by both Fourier-transform infrared (FTIR) and circular dichroism spectroscopy. Our studies show that hemopexin contains about 55% β-structure, 15% α-helix, and 20% turns. The two isolated structural domains of hemopexin each have secondary structures similar to hemopexin. Although there are significant tertiary conformational changes indicated by the CD spectra, the overall secondary structure of hemopexin is not affected by binding heme. However, moderate changes in secondary structure do occur when the heme-binding domain of hemopexin associates with heme. In spite of the exceptionally tight binding at neutral pH, heme is released from the bis-histidyl heme-hemopexin complex at pH 5.0. Under this acidic condition, hemopexin maintains the same overall secondary structure as the native protein and is able to resume the heme-binding function and the native structure of the hemeprotein (as indicated by the CD spectra) when returned to neutral pH. We propose that the state of hemopexin identified in vitro at pH 5.0 resembles that of this protein in the acidic environment of the endosomes in vivo when hemopexin releases heme during receptor-mediated endocytosis. © 1994 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340200208
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  • 187
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    Crystallization of a scRIP - gelonin isolated from plant seeds Gelonium multiforum (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 19 (1994), S. 340-342 
    Details
    ISSN: 0887-3585
    Keywords: protein ; ribosome ; inactivation ; toxin ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Single crystals of the protein gelonin isolated from the seeds of Gelonium multiforum have been grown at room temperature by vapor diffusion method. The crystals are monclinic with a = 49.4 Å, b = 44.9 Å, c = 137.4 Å, and β = 98.3°. The space group is P21, with two molecules in the asymmetric unit which are related by a noncrystallographic 2-fold axis along ψ =13° and φ =88°. The crystals diffract X-rays to high resolution, making it possible to obtain an accurate structure of this single chain ribosome inactivating protein. © 1994 Wiley-Liss, Inc.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340190409
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  • 188
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    Homologous modeling of the lysosomal protective protein/carboxypeptidase L: Structural and functional implications of mutations identified in galactosialidosis patients (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 18 (1994), S. 81-93 
    Details
    ISSN: 0887-3585
    Keywords: serine carboxypeptidase ; protein modeling ; mutation analysis ; comparative modeling ; cathepsin A ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The deficiency of the lysosomal protective protein/carboxypeptidase L (CARB L) causes the lysosomal storage disorder, galactosialidosis, characterized by neuraminidase and β-galactosidase deficiencies in patients' cells. The three enzymes form a complex inside the lysosome, and the neuraminidase and β-galactosidase deficiencies are secondary to CARB L deficiency. Sequence similarity and common enzymological properties suggest that the protomeric tertiary structure of CARB L is conserved within a family of serine carboxypeptidases which includes the yeast carboxypeptidase Y, killer expression I gene product and several plant carboxypeptidases. We used this homology to build a model of the CARB L structure based on the recently published X-ray atomic coordinates of the wheat carboxypeptidase II (CPDW-II) which shares 32% primary structure identity with CARB L. Small insertions and deletions were accommodated into the model structure by energy minimization using the DREIDING II force field. The Cα atomic-coordinates of the final CARB L model have a RMS shift of 1.01 Å compared to the corresponding conserved residues in the CPDW-II template structure. The correct orientation of the homologous catalytic triad residues Ser150, His429 and Asp392, the potential energy calculations and the distribution of hydrophobic and hydrophillic residues in the structure all support the validity of the CARB L model. Most missense mutations identified in galactosialidosis patients were located in secondary structural elements except for the Tyr211→Asn mutation which is in a loop. The other mutant residues have their side chains deeply buried in the central β-sheet of the model structure except for the Phe412→Val mutation which is located in the dimer interface. The predicted effects of specific mutations on CARB L structural stability correlates well with recently published transient expression studies of mutant CARB L (Shimmoto, M. et al., J. Clin. Invest., 91:2393-2399, 1993). © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340180110
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  • 189
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    Molecular dynamics simulations of trp apo-and holorepressors: Domain structure and ligand-protein interaction (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 20 (1994), S. 248-258 
    Details
    ISSN: 0887-3585
    Keywords: molecular dynamics ; trp-repressor ; ligand ; domain ; dynamic cross-correlation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Molecular dynamics simulations of the apo- and holo-forms of thetrp-repressor protein were performed under extensively solvated conditions in order to elucidate their dynamic structures and ligand-protein interactions. The root mean square fluctuations calculated from the trajectories agreed with those calculated from X-ray temperature factors. Distance, distance fluctuation, and dynamic cross-correlation maps were drawn to provide information on the dynamic structures and communications among the domains. A three-domain format has been proposed for the crystal structure (Zhang et at., Nature 327:591-597, 1987) namely, helices A-C and F of both subunits make up a central core, and D and E of each subunit forms a DNA binding head. The results of the simulations were mostly consistent with the three-domain format. However, helix F was more flexible and freer than other parts of the central core. The turn DE, the helix-turn-helix DNA binding motif, was free from interactions and correlations with other domains in both forms of the repressor. A comparison of the simulations of the aporepressor and holorepressor showed that tryptophan binding made the DNA-binding helix D more flexible but helix F less flexible. Several amino acid residues in contact with the bound tryptophan were identified as making concerted motions with it. Interaction energies between the corepressor and the amino acid residues of the protein were analyzed; the results were mostly consistent with the mutational experiments. © 1994 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340200305
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  • 190
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    Protein simulations using techniques suitable for very large systems: The cell multipole method for nonbond interactions and the Newton-Euler inverse mass operator method for internal coordinate dynamics (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 20 (1994), S. 227-247 
    Details
    ISSN: 0887-3585
    Keywords: cell multipole method ; Newton-Euler inverse mass operator ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Two new methods developed for molecular dynamics simulations of very large proteins are applied to a series of proteins ranging up to the protein capsid of tomato bushy stunt virus (TBSV).For molecular dynamics of very large proteins and polymers, it is useful to carry out the dynamics using internal coordinates (say, torsions only) rather than Cartesian coordinates. This allows larger time steps, eliminates problems with the classical description of high energy modes, and focuses on the important degrees of freedom. The resulting equation of motion has the form where for T is the vector of generalized forces, M(θ) is the moments of inertia tensor, is the vector of torsions, and C is a vector containing Coriolis forces and nonbond forces. The problem is that to calculate the acceleration vector from M, C, and Trequires inverting. M(θ), an order N3calculation. Since the number of degrees of freedom might be 300,000 for a million atom system, solving these equations every time step is impractical, restricting internal coordinate methods to small systems. The new method, Newton-Euler Inverse Mass Operator (NEIMO) dynamics, constructs the torsional accelerations vector directly by an order N process, allowing internal-coordinate dynamics to be solved for super larger (million atom) systems, The first use of the NEIMO method for molecular dynamics of proteins is presented here.A second serious difficulty for large proteins is calculation of the nonbond forces. We report here the first application to proteins of the new Cell Multipole Method (CMM) to evaluate the Coulomb and van der Waals interactions. The cost of CMM scales linearly with the number of particles while retaining an accuracy significantly better than standard non bond methods (involving cutoffs).Results for NEIMO and CMM are given for simulations of a wide range of peptide and protein systems, including the protein capsid of TBSV with 488,000 atoms. The computational times for NEIMO and CMM are demonstrated to scale linearly with size. With NEIMO the dynamics time steps can be as large as 20 fs (for small peptides), much larger than possible with standard Cartesian coordinate dynamics.For TBSV we considered both the normal form and the high pH form, in which the Ca2+ ions are removed. These calculations lead to a contraction of the protein for both forms (probably because of ignoring the RNA core not observed in the X-ray). © 1994 Wiley-Liss, Inc.
    Additional Material: 21 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340200304
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  • 191
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    A surface mutant (G82R) of a human α-glutathione S-transferase shows decreased thermal stability and a new mode of molecular association in the crystal (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 20 (1994), S. 259-263 
    Details
    ISSN: 0887-3585
    Keywords: glutathione S. transferase ; temperature-sensitive protein ; chimeric protein ; mutant protein ; X-ray analysis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A chimeric enzyme (GST121) of the human α-glutathione S-transferases GST1-1 and GST2-2, which has improved catalytic efficiency and thermostability from its wild-type parent proteins, has been crystallized in a space group that is isomorphous with that reported for crystals of GST1-1. However, a single-site (G82R) mutant of GST121, which exhibits a significant reduction both in vitro and in vivo in protein thermostability, forms crystals that are not isomorphous with GST1-1. The mutant protein crystallizes in space group P212121, with cell dimensions a = 49.5, b = 92.9, c = 115.9 Å, and one dimer per asymmetric unit. Preliminary crystallographic results show that a mutation of the surface residue Gly 82 from a neutral to a charged residue causes new salt bridges to be formed among the GST dimers, suggesting that the G82R mutant might aggregate more readily than does GST121 in solution resulting in a change of its solution properties. © 1994 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340200306
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  • 192
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    Polar and nonpolar atomic environments in the protein core: Implications for folding and binding (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 20 (1994), S. 264-278 
    Details
    ISSN: 0887-3585
    Keywords: hydrophobic interactions ; protein stability ; hydrophobicity scale ; protein mutant stability ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Hydrophobic interactions are believed to play an important role in protein folding and stability. Semi-empirical attempts to estimate these interactions are usually based on a model of solvation, whose contribution to the stability of proteins is assumed to be proportional to the surface area buried upon folding. Here we propose an extension of this idea by defining an environment free energy that characterizes the environment of each atom of the protein, including solvent, polar or nonpolar atoms of the same protein or of another molecule that interacts with the protein. In our model, the difference of this environment free energy between the folded state and the unfolded (extended) state of a protein is shown to be proportional to the area buried by nonpolar atoms upon folding. General properties of this environment free energy are derived from statistical studies on a database of 82 well-refined protein structures. This free energy is shown to be able to discriminate misfolded from correct structural models, to provide an estimate of the stabilization due to oligomerization, and to predict the stability of mutants in which hydrophobic residues have been substituted by site-directed mutagenesis, provided that no large structural modifications occur. © 1994 Wiley-Liss, Inc.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340200307
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  • 193
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    An evaluation of implicit and explicit solvent model systems for the molecular dynamics simulation of bacteriophage T4 lysozyme (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 18 (1994), S. 19-33 
    Details
    ISSN: 0887-3585
    Keywords: Discover program ; protein dynamics ; computer simulation ; protein motions ; counterions ; dielectric ; protein electrostatics ; aqueous simulation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: In this report we examine several solvent models for use in molecular dynamics simulations of protein molecules with the Discover program from Biosym Technologies. Our goal was to find a solvent system which strikes a reasonable balance among theoretical rigor, computational efficiency, and experimental reality. We chose phage T4 lysozyme as our model protein and analyzed 14 simulations using different solvent models. We tested both implicit and explicit solvent models using either a linear distance-dependent dielectric or a constant dielectric. Use of a linear distance-dependent dielectric with implicit solvent significantly diminished atomic fluctuations in the protein and kept the protein close to the starting crystal structure. In systems using a constant dielectric and explicit solvent, atomic fluctuations were much greater and the protein was able to sample a larger portion of conformational space. A series of nonbonded cutoff distances (9.0, 11.5, 15.0, 20.0 Å) using both abrupt and smooth truncation of the nonbonded cutoff distances were tested. The method of dual cutoffs was also tested. We found that a minimum nonbonded cutoff distance of 15.0 Å was needed in order to properly couple solvent and solute. Distances shorter than 15.0 Å resulted in a significant temperature gradient between the solvent and solute. In all trajectories using the proprietary Discover switching function, we found significant denaturation in the protein backbone; we were able to run successful trajectories only in those simulations that used no switching function. We were able to significantly reduce the computational burden by using dual cutoffs and still calculate a quality trajectory. In this method, we found that an outer cutoff distance of 15.0 Å and an inner cutoff distance of 11.5 worked well. While a 10 Å shell of explicit water yielded the best results, a 6 A shell of water yielded satisfactory results with nearly a 40% reduction in computational cost. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340180105
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  • 194
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    Collective motions in proteins investigated by X-ray diffuse scattering (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 18 (1994), S. 34-48 
    Details
    ISSN: 0887-3585
    Keywords: normal mode refinement ; correlation function ; intra- and intermolecular correlation ; higher order scattering ; human lysozyme ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: We have developed theoretical models for analysis of X-ray diffuse scattering from protein crystals. A series of models are proposed to be used for experimental data with different degrees of precision. First, we propose the normal mode model, where conformational dynamics of a protein is assumed to occur mostly in a limited conformational subspace spanned by a small number of low-frequency normal modes in the protein. When high precision data are available, variances and covariances of the normal mode variables can be determined from experimental data using this model. For experimental data with lower degrees of precision, we introduce a series of simpler models. These models express the covariance matrix using relatively simple empirical correlation functions by assuming the correlation between a pair of atoms to be isotropic. As an application of these simpler models, we calculate diffuse-scattering patterns from a human lysozyme crystal to examine how each adjustable parameter in the models affects general features of the resulting patterns. The results of the calculation are summarized as follows. (1) The higher order scattering makes a significant contribution at high resolutions. (2) The resulting simulated patterns are sensitive to changes in correlation lengths of about 1 Å, as well as to changes of the functional form of the correlation function. (3) But only the “average” value of the intra- and intermolecular correlation lengths seems to determine the gross features of the pattern. (4) The effect of the atom-dependent amplitude of fluctuations is difficult to observe. © 1994 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1002/prot.340180106
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  • 195
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    X-ray structures of fragments from binding and nonbinding versions of a humanized anti-CD18 antibody: Structural indications of the key role of VH residues 59 to 65 (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 18 (1994), S. 49-62 
    Details
    ISSN: 0887-3585
    Keywords: protein ; mutation ; Fab ; Fv ; complementarity determining region ; hypervariability ; integrin ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: X-ray crystal structures of fragments from two different humanized antiCD18 antibodies are reported. The Fv fragment of the nonbinding version has been refined in space group C2 with a=64.2 Å, b=61.3 Å, c=51.8 Å, and β=99° to an R-value of 18.0% at 1.9 Å, and the Fab fragment of the tight-binding version has been refined in space group P3 with a=101. Å and c=45.5 Å to an R-value of 17.8% at 3.0 Å resolution. The very large difference in their binding affinity (〉1000-fold) is attributed to large and local structural differences in the C-terminal part of CDR-H2, and from this we conclude there is direct contact between this region and antigen when they combine. X-ray structures of antibody-antigen complexes available in the literature have yet to show this part of CDR-H2 in contact with antigen, despite its hypervariable sequence. Implications of this result for antibody humanization are discussed. © 1994 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340180107
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  • 196
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    Entropy in biological binding processes: Estimation of translational entropy loss (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 18 (1994), S. 63-67 
    Details
    ISSN: 0887-3585
    Keywords: entropy ; thermodynamics ; binding energetics ; translational entropy ; macromolecular interactions ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The loss of translational degrees of freedom makes an important, unfavorable contribution to the free energy of binding. Examination of experimental values suggest that calculation of this entropy using the Sackur-Tetrode equation produces largely overestimated values. Better agreement is obtained using the cratic entropy. Theoretical considerations suggest that the volumes available for the movement of a ligand in solution and in a complex are rather similar, suggesting also that the cratic entropy provides the best estimate of the loss of translational entropy. © 1994 John Wiley & Sons, Inc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340180108
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    Masthead (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 18 (1994) 
    Details
    ISSN: 0887-3585
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340180201
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  • 198
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    Molecular surface representations by sparse critical points (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 18 (1994), S. 94-101 
    Details
    ISSN: 0887-3585
    Keywords: surface representation ; molecular recognition ; protein docking ; surface triangulation ; molecular graphics ; molecular visualization ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: We have defined a molecular surface representation that describes precisely and concisely the complete molecular surface. The representation consists of a limited number of critical points disposed at key locations over the surface. These points adequately represent the shape and the important characteristics of the surface, despite the fact that they are modest in number. We expect the representation to be useful in areas such as molecular recognition and visualization. In particular, using this representation, we are able to achieve accurate and efficient protein-protein and protein-small molecule docking. © 1994 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340180111
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  • 199
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    Introducing “Future Directions” (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 18 (1994), S. i 
    Details
    ISSN: 0887-3585
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340180202
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  • 200
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    Crystallization and characterization of colicin E1 channel-forming polypeptides (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 19 (1994), S. 150-157 
    Details
    ISSN: 0887-3585
    Keywords: X-ray crystallography ; membrane protein ; ion channels ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Crystals of the channel-forming domain of colicin E1 from E. coli were grown by vapor diffusion at pH 6.4 and higher pH values. Cleavage of the colicin molecule with trypsin or thermolysin produced two of the pore-forming polypeptides used in these experiments. The third polypeptide was purified from a constructed plasmid that overexpresses only the C-terminal domain of colicin E1. Polypeptide crystals are tetragonal with space group I4, have one monomer in the asymmetric unit, and diffract to 2.2-2.4 Å. Unit cell parameters for the tryptic and thermolytic polypeptides are a = 102.9 Å and c = 35.6 Å. Crystals of the overexpressed polypeptide have unit cell parameters of a =87.2 Å and c =59.1 Å. The crystals were characterized by precession photography, and native data sets of each channel-forming fragment were collected on a Siemens-Nicolet area detector. The crystallization and characterization of these polypeptides are the first steps in the structure determination of the channel-forming domain of colicin E1. © 1994 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/prot.340190208
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