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  • 1
    Digitale Medien
    Digitale Medien
    Highly stable biosensor using an artificial enzyme (1987)
    s.l. : American Chemical Society
    Analytical chemistry 59 (1987), S. 536-537 
    Details
    ISSN: 1520-6882
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/ac00130a038
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  • 2
    Digitale Medien
    Digitale Medien
    Regulation of the extent of polyadenylation of vasopressin and growth hormone mRNAs in response to physiological stimuli
    Amsterdam : Elsevier
    Regulatory Peptides 45 (1993), S. 37-41 
    Details
    ISSN: 0167-0115
    Schlagwort(e): Anterior pituitary gland ; Dehydration ; Hypothalamus ; Poly(A) tail ; Transgenic mouse
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Medizin
    Materialart: Digitale Medien
    URL: http://linkinghub.elsevier.com/retrieve/pii/0167-0115(93)90179-C
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  • 3
    Digitale Medien
    Digitale Medien
    Neurogenic diabetes insipidus in children with hypoxic encephalopathy: Six new cases and a review of the literature (1996)
    Springer
    European journal of pediatrics 155 (1996), S. 245-248 
    Details
    ISSN: 1432-1076
    Schlagwort(e): Hypoxia/ischaemia ; Hypoxic encephalopathy ; Neurogenic diabetes insipidus ; Polyuria
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Hypoxic encephalopathy is rarely mentioned as a cause of neurogenic diabetes insipidus (DI) in children. We here report six cases of DI which occurred after severe hypoxic/ischaemic brain damage and include a review of the literature on 28 paediatric cases of neurogenic DI due solely to severe hypoxia/ischaemia. Airway obstruction, haemorrhagic shock and sudden infant death syndrome are the three major causes of hypoxia/ischaemia. The ages (25/28) ranged from 0.03 to 18 years (mean 7.27 years, median 5 years). The intervals between the hypoxic insult and the onset of DI (23/28) ranged from 0.08 days (2 h) to 13 days (mean 4.07 days, median 3.5 days). Linear regression analysis revealed no significant correlation between the age and the interval. Nineteen cases (82.6%) developed DI within 6 days after the hypoxic/ischaemic insult. Only two neonates survived with developmental delay. The remaining 26 cases died. Conclusion Neurogenic DI can be caused by hypoxia/ischaemia and is an ominous sign of severe brain damage in children with hypoxic encephalopathy. It is important to recognize this potential sequel by regularly monitoring intake and output, plasma sodium level, and urine specific gravity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01953946
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  • 4
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): 5-Hydroxytryptamine ; 5,7-Dihydroxytryptamine ; Operant behaviour ; Timing ; Interval bisection procedure ; Acquisition ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02245343
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  • 5
    Digitale Medien
    Digitale Medien
    Effect of destruction of noradrenergic neurones with DSP4 on performance on a free-operant timing schedule (1998)
    Springer
    Psychopharmacology 136 (1998), S. 235-242 
    Details
    ISSN: 1432-2072
    Schlagwort(e): Key words DSP4 ; Noradrenaline ; Operant behaviour ; Timing ; Behavioural switching ; Arousal
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract This experiment examined the effect of destroying central noradrenergic neurones, using the selective neurotoxin DSP4 [N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine], on performance in a free-operant timing schedule. Rats received either systemic treatment with DSP4 or vehicle-alone injections. They were trained to press levers for a sucrose reinforcer. Training sessions consisted of 40, 50-s trials in which reinforcers were available on a variable-interval 25-s schedule; in the first 25 s of each trial, reinforcers were only available for responses on lever A, whereas in the last 25 s reinforcers were available only for responses on lever B. Data were collected from probe trials (four per session), in which no reinforcers were delivered, during the last ten of 60 training sessions. Both groups showed decreasing response rates on lever A, and increasing response rates on lever B, as a function of time from the onset of the trial. Quantitative indices of timing behaviour were derived from a two-parameter logistic function fitted to the relative response rates on lever B (response rate on lever B, expressed as a percentage of overall response rate); this function accounted for 〉 90% of the data variance in each group. The DSP4-treated group showed a significantly lower value of the indifference point (i.e. the time corresponding to 50% responding on lever B) than the control group. The slope of the function and the rate of switching between response alternatives did not differ significantly between the two groups. The concentrations of noradrenaline were markedly reduced in the neocortex and hippocampus of the DSP4-treated group, but the concentrations of dopamine, 5-hydroxytryptamine and 5-hydroxyindoleacetic acid were not significantly altered. It is suggested that results may be consistent with a role of the dorsal ascending noradrenergic pathway in behavioural “arousal”.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002130050561
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  • 6
    Digitale Medien
    Digitale Medien
    Effect of central 5-hydroxytryptamine depletion on performance in the free-operant psychophysical procedure: facilitation of switching, but no effect on temporal differentiation of responding (1999)
    Springer
    Psychopharmacology 143 (1999), S. 166-173 
    Details
    ISSN: 1432-2072
    Schlagwort(e): Key words 5-Hydroxytryptamine ; 5 ; 7-Dihydroxytryptamine ; Operant behaviour ; Timing ; Switching
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract This experiment examined the effect of destroying the ascending 5-hydroxytryptaminergic (5-HTergic) pathways on timing and switching behaviour in the free-operant psychophysical procedure. Rats received injections of 5,7-dihydroxytryptamine into the dorsal and median raphe nuclei or sham lesions. They were trained to press levers for sucrose reinforcement; sessions consisted of fifty 50-s trials in which reinforcers were available on a variable-interval 30-s schedule. In the first 25 s, of each trial, reinforcement was only available for responses on lever A; in the last 25 s, it was available only for responses on lever B. In phase 1 (70 sessions) repetitive switching between the levers was prevented by withdrawal of lever A after the first response on lever B in each trial; in phase 2 (40 sessions) this constraint on switching was removed; in phase 3 (40 sessions) the constraint was reinstated. Data were collected from probe trials (four per session) in which no reinforcers were delivered, during the last ten sessions of each phase. In all phases, both groups showed declining response rates on lever A and increasing response rates on lever B as a function of time from the onset of the trial. Response rate on lever B, expressed as percentage of overall response rate, could be described by a two-parameter logistic function. Removal of the constraint on switching reduced the slope of the function without changing the indifference point (time corresponding to 50% responding on lever B). The parameters of the timing function did not differ between the groups in any of the phases. However, the lesioned group showed a greater enhancement of switching rate during phase 2 than the control group. The levels of 5-HT and 5-hydroxyindoleacetic acid were reduced in the brains of the lesioned rats, but the levels of noradrenaline and dopamine were not altered. The results provide further evidence for the involvement of the ascending 5-HTergic pathways in switching between response alternatives, but cast doubt on our previous suggestion that the effects of 5-HT depletion on temporal differentiation of behaviour are mediated by facilitated switching.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002130050932
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  • 7
    Digitale Medien
    Digitale Medien
    Effect of central 5-hydroxytryptamine depletion on changeover behaviour in concurrent schedules of reinforcement (1999)
    Springer
    Psychopharmacology 144 (1999), S. 264-271 
    Details
    ISSN: 1432-2072
    Schlagwort(e): Key words 5-Hydroxytryptamine ; 5 ; 7-Dihydroxytryptamine ; Operant behaviour ; Concurrent schedules ; Switching
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract   Rationale: Previous experiments have shown that rats whose 5-hydroxytryptaminergic (5-HTergic) pathways have been destroyed exhibit higher rates of switching between response alternatives on various temporal differentiation schedules. Objective: This paper reports two experiments investigating the effect of central 5-HT depletion on switching between concurrent schedules of reinforcement which do not entail temporal differentiation of behaviour. Methods: Rats received injections of 5,7-dihydroxytryptamine into the dorsal and median raphe nuclei or sham lesions. They were trained to press levers for sucrose reinforcement. In experiment 1, the rats were exposed to concurrent pairs of variable-time (VT) schedules specifying equal inter-reinforcement intervals; responses on a single ”changeover lever” alternated between the two VT schedules. In experiment 2, the rats were exposed to concurrent pairs of variable-interval (VI) schedules specifying equal inter-reinforcement intervals; responses on one lever (”VI lever”) earned reinforcers, while responses on the other lever (”changeover lever”) alternated between the two VI schedules. Results: In experiment 1, both groups showed longer ”dwell-times” (intervals between successive changeover responses) when a reinforcer was delivered in the ”dwell” than when no reinforcer was delivered (”win-stay” effect). The lesioned rats showed higher rates of changeover responding and shorter dwell-times (with and without reinforcer delivery) than the sham-lesioned group. In experiment 2, the rate of responding on the VI lever did not differ significantly between the two groups; however, the lesioned rats showed higher rates of changeover responding, shorter dwell-times (with and without reinforcer delivery) and smaller numbers of inter-changeover responses on the VI lever than the sham-lesioned group. In both experiments, the levels of 5-HT and 5-hydroxyindoleacetic acid were reduced in the brains of the lesioned rats, but the levels of noradrenaline and dopamine were not altered. Conclusions: These results provide further evidence for the involvement of the ascending 5-HTergic pathways in behavioural ”switching”, and indicate that this is not restricted to temporal differentiation schedules.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002130051002
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  • 8
    Digitale Medien
    Digitale Medien
    Theory and method in the quantitative analysis of ”impulsive choice” behaviour: implications for psychopharmacology (1999)
    Springer
    Psychopharmacology 146 (1999), S. 362-372 
    Details
    ISSN: 1432-2072
    Schlagwort(e): Key words Impulsive choice ; Delay of reinforcement ; Probability of reinforcement ; Hyperbolic discounting functions ; Indifference equations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract  Impulsive choice refers to the selection of small immediate gains in preference to larger delayed gains, or the selection of large delayed penalties in preference to smaller immediate penalties. Current theoretical interpretations of impulsive choice are reviewed, and a synthesis of these ideas, the ”multiplicative hyperbolic model of choice”, is presented. The model assumes that the value of a positive reinforcer increases as a hyperbolic function of its size, and decreases as a hyperbolic function of its delay and the odds against its occurrence. Each hyperbolic function contains a single discounting parameter which quantifies the organism’s sensitivity to the variable in question. The hyperbolic discounting functions combine multiplicatively to determine the overall value of the reinforcer. Equivalent functions are postulated to govern the (negative) value of aversive events, the net value of an outcome reflecting the algebraic sum of the positive and negative values. The model gives rise to a quantitative methodology for studying impulsive choice, based on a family of linear indifference (null) equations, which describe performance under conditions of indifference, when the values of the reinforcers are assumed to be equal. This methodology may be used to identify individual differences in sensitivity to the magnitude, delay and probability of reinforcement. The methodology is also suitable for the quantitative evaluation of the effects of some pharmacological interventions on discounting parameters. Recent psychopharmacological studies of impulsive choice are reviewed, and the utility of indifference equations for extending this work, and developing a quantitative psychopharmacology of impulsive choice is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/PL00005482
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  • 9
    Digitale Medien
    Digitale Medien
    The role of the ascending 5-hydroxytryptaminergic pathways in timing behaviour: further observations with the interval bisection task (1995)
    Springer
    Psychopharmacology 120 (1995), S. 213-219 
    Details
    ISSN: 1432-2072
    Schlagwort(e): 5-hydroxytryptamine ; 5,7-Dihydroxytryptamine ; Operant behaviour ; Timing ; Interval bisection procedure ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract This experiment examined the effect of destroying the 5-hydroxytryptaminergic (5HTergic) pathways on rats' ability to discriminate between two durations. Rats received injections of 5,7-dihydroxytryptamine into the median and dorsal raphe nuclei or sham lesions. They were trained to press lever A following a 2-s presentation of a light and lever B following an 8-s presentation of the light. For some rats, the levers were inserted into the chamber immediately after stimulus presentation (“no-poke-requirement”); for others, the levers were not inserted until a flap covering the food tray positioned midway between the levers had been depressed (“poke-requirement”). When stable performance was attained, “probe” trials were introduced in which the light was presented for intermediate durations. Logistic functions were derived relating percent choice of lever B to log stimulus duration. Under the “no-poke-requirement” condition, the bisection point (duration yielding 50% choice of lever B) was shorter in the lesioned rats than in the control rats. Under the “poke-requirement” condition, this effect of the lesion was attenuated. There was no effect of the lesion on the Weber fraction under either condition. The levels of 5HT and 5-hydroxyindoleacetic acid were reduced in the brains of the lesioned rats, but the levels of noradrenaline and dopamine were not altered. It is proposed that rats may attain accurate timing under the interval bisection task by moving from one lever to the other during stimulus presentation; this movement may be facilitated by destruction of the 5HTergic pathways. Accurate timing is still possible when this movement is suppressed by the introduction of a “poke requirement”; however, in this case timing is not affected by 5HT depletion.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02246196
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  • 10
    Digitale Medien
    Digitale Medien
    Effect of destruction of the 5-hydroxytryptaminergic pathways on behavioural timing and “switching” in a free-operant psychophysical procedure (1996)
    Springer
    Psychopharmacology 127 (1996), S. 346-352 
    Details
    ISSN: 1432-2072
    Schlagwort(e): Key words 5-Hydroxytryptamine ; 5 ; 7-Dihydroxytryptamine ; Operant behaviour ; Timing ; Behavioural switching
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract This experiment examined the effect of destruction of the ascending 5-hydroxytryptaminergic (5HTergic) pathways on performance in a free-operant timing schedule. Rats received either injections of 5,7-dihydroxytryptamine into the dorsal and median raphe nuclei or sham lesions. They were trained to press levers for a sucrose reinforcer. Training sessions consisted of 40, 50-s trials in which reinforcers were available on a variable-interval 25-s schedule; in the first 25 s of each trial, reinforcers were only available for responses on lever A, whereas in the last 25 s reinforcers were available only for responses on lever B. Data were collected from probe trials (four per session) in which no reinforcers were delivered, during the last ten of 50 training sessions. Both groups showed decreasing response rates on lever A and increasing response rates on lever B as a function of time from the onset of the trial. Response rate on lever B, expressed as a percentage of overall response rate, could be described by a two-parameter logistic function; neither the indifference point (i.e. the time corresponding to 50% responding on lever B) nor the slope of the function differed between the two groups. However, the lesioned group showed a higher rate of switching between response alternatives than the sham-lesioned group. The levels of 5HT and 5-hydroxyindoleacetic acid were reduced in the brains of the lesioned rats, but the levels of noradrenaline and dopamine were not significantly altered. The results confirm previous findings that behaviour in timing schedules is sensitive to destruction of the central 5HTergic pathways, and suggest that these pathways may contribute to the inhibitory regulation of switching between behavioural states.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002130050096
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