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Biomedical subjects

P Vetter

Publications and source records attributed to P Vetter.

At least 19 recordsLinked to original sources
PubMed2001

Lack of association between schizophrenia and the phospholipase-A(2) genes cPLA2 and sPLA2.

The well-established role of genetic factors in the etiology of schizophrenia together with reports of allelic association with cPLA2, a phospholipase-A(2) gene, a reported increase of phospholipase-A(2) activity, and the phospholipase-A(2) hypothesis of Horrobin et al. [1995: Med Hypotheses 45:605-613] strongly support cPLA2 (PLA2G4A) and sPLA2 (PLA2G1B) as candidate genes for schizophrenia. In search for allelic association between these phospholipase-A(2) genes and schizophrenia, two samples of Chinese and European origins, in total 328 unrelated schizophrenic patients and their parents, were investigated using Falk and Rubinstein's haplotype relative risk method. Both genes showed marginally significant evidence for association in the total sample (P <or= 0.05), which, however, did not survive the Bonferroni correction for multiple testing. In conclusion, our results do not provide support for the phospholipase-A(2) hypothesis of schizophrenia. Additional studies will be necessary to rule out a possible confounding effect of niacin sensitivity as postulated by Hudson et al. [1999: Biol Psychiatr 46:401-405].

Adolescent↗
PubMed2001

The influence of previous experience on predictive motor control.

Anticipating the consequences of our motor commands is a fundamental component of sensorimotor control. For example, when one hand pulls on an object held in the other, the restraining hand generates an anticipatory increase in grip force thereby preventing the object from slipping. To investigate how such anticipation is learned subjects held an object, whose properties were under computer control, between their hands. This allowed instant changes in the behaviour of the manipulated object on a trial by trial basis. The extent of grip force modulation seen in one hand, when the other pulled on the object was found to depend in a systematic way on the object's properties experienced over at least the previous three trials.

Adult↗
PubMed2001

No association between dopamine D2 receptor gene (DRD2) and human intelligence.

Significantly diminished intellectual functioning, as indicated by appropriately administered IQ tests with scores below 70, is a frequent mental handicap leading to severe social disadvantages and serves as a paradigm for molecular genetic research of complex disorders and traits due to its multitude of known and unknown, genetic as well as environmental causes. Since the number of confounding variables is expected to be considerably reduced in the normal population at the opposite ends of the IQ distribution, we employed a contrast of extremes approach by comparing adults of high (N = 71) and average IQ (N = 78) in association studies to search for genes involved in the multigenic forms of familial mental retardation. The dopamine D2 receptor gene (DRD2) was chosen as a candidate gene for general cognitive ability (g) since it has been found to be associated with visuospatial ability which in turn is highly correlated with g. Confirming two similar studies in children, however, no significant differences were obtained. Given three negative studies, the DRD2 gene is unlikely to pay a major role in g.

Adult↗
PubMed2001

Propagation of action potentials in dendrites depends on dendritic morphology.

Action potential propagation links information processing in different regions of the dendritic tree. To examine the contribution of dendritic morphology to the efficacy of propagation, simulations were performed in detailed reconstructions of eight different neuronal types. With identical complements of voltage-gated channels, different dendritic morphologies exhibit distinct patterns of propagation. Remarkably, the range of backpropagation efficacies observed experimentally can be reproduced by the variations in dendritic morphology alone. Dendritic geometry also determines the extent to which modulation of channel densities can affect propagation. Thus in Purkinje cells and dopamine neurons, backpropagation is relatively insensitive to changes in channel densities, whereas in pyramidal cells, backpropagation can be modulated over a wide range. We also demonstrate that forward propagation of dendritically initiated action potentials is influenced by morphology in a similar manner. We show that these functional consequences of the differences in dendritic geometries can be explained quantitatively using simple anatomical measures of dendritic branching patterns, which are captured in a reduced model of dendritic geometry. These findings indicate that differences in dendritic geometry act in concert with differences in voltage-gated channel density and kinetics to generate the diversity in dendritic action potential propagation observed between neurons. They also suggest that changes in dendritic geometry during development and plasticity will critically affect propagation. By determining the spatial pattern of action potential signaling, dendritic morphology thus helps to define the size and interdependence of functional compartments in the neuron.

Action Potentials↗
PubMed2000

The CNS updates its context estimate in the absence of feedback.

Human motor behaviour is remarkably accurate and appropriate even though our bodies and the objects we interact with change over time. To achieve such performance the motor system has to tailor the motor commands to the current context, that is the properties of objects in the world and the prevailing environmental conditions. The current context can be estimated by integrating two sources of information, sensory feedback and knowledge about how the context is likely to have changed from the previous estimate. Here we show that in the absence of sensory feedback about the context the second process is able to extrapolate the likely evolution of the context without requiring awareness that the context is changing.

Adult↗
PubMed2000

Reliability and stability of contingent negative variation.

Reliability parameters of a test indicate the stability (and quality) of the test itself. Reliability coefficients greater than 0.70 suggest an attribute as being sufficiently stable over time to be characterized as a trait. Reliability parameters of contingent negative variation (CNV) amplitudes in 27 healthy individuals were determined using a test-retest design. CNV was recorded at Cz, with an interstimulus interval of 3 s, on 2 separate occasions: initial session and 10 days later. Correlation coefficients between the 2 recording sessions were 0.675 for the total-CNV (tCNV), 0.855 for the early component (iCNV), 0.631 for the late component (lCNV), and 0.420 for the post-imperative negative variation (PINV). Statistical retest parameters for Spearman Brown were 0.806 for tCNV, 0.922 for iCNV, 0.774 for lCNV, and 0.655 for PINV. The iCNV, more than the other parameters, remained stable over the period of 10 days. It is suggested that the described standardized CNV recording procedure ensures reproducible and stable results in healthy subjects.

Adult↗
PubMed2000

Context estimation for sensorimotor control.

Human motor behavior is remarkably accurate and appropriate even though the properties of our own bodies as well as the objects we interact with vary over time. To adjust appropriately, the motor system has to estimate the context, that is the properties of objects in the world and the prevailing environmental conditions. Here we show that to determine the current context the CNS uses information from both prior knowledge of how the context might evolve over time and from the comparison of predicted and actual sensory feedback. We show that these two sources of information may be modeled within the CNS and combined to derive an accurate estimate of the context which adjusts motor command selection. This provides a novel probabilistic framework for sensorimotor control.

Adaptation, Physiological↗
PubMed1999

Regulation of synaptic transmission in the mossy fibre-granule cell pathway of rat cerebellum by metabotropic glutamate receptors.

The role of metabotropic glutamate receptors (mGluRs) in the mossy fibre-granule cell pathway in rat cerebellum was studied using slice preparations and electrophysiological techniques. Application of the group I selective agonist (S)-3,5-dihydroxyphenylglycine (DHPG) evoked, in a concentration-dependent manner (EC50 = 33 microM), a depolarising/hyperpolarising complex response from granule cells which was preferentially inhibited by the group I selective antagonist (S)-4-carboxyphenylglycine (4CPG). The group III selective agonist L-amino-4-phosphonobutyrate (AP4) evoked a hyperpolarising response (EC50 = 10 microM) which was inhibited by the group II/III selective antagonist (S)-alpha-methyl-4-phosphonophenylglycine (MPPG). The group II agonist (2S,2'R,3'R)-2-(2',3'-dicarboxylcyclopropyl)glycine (DCG-IV) elicited no measurable voltage change. The amplitude of the synaptically-mediated mossy fibre response in granule cells was unaffected during application of AP4, was reduced by DHPG and was enhanced by DCG-IV (EC50 = 80 nM). These effects were inhibited by the group selective antagonists 4CPG and (2S,1'S,2'S,3'R)-2-(2'-carboxy-3'-phenylcyclopropyl)glycine (PCCG-4), respectively. Further investigation using patch-clamp recording revealed that DCG-IV potently inhibited spontaneous GABAergic currents. We conclude that group I and III (but not group II) mGluRs are functionally expressed by granule cells, whereas unexpectedly group II or III mGluRs do not appear to be present presynaptically on mossy fibre terminals. Group II mGluRs are located on Golgi cell terminals; when activated these receptors cause disinhibition, a function which may be important for gating information transfer from the mossy fibres to the granule cells.

Animals↗
PubMed1999

Evidence for an eye-centered spherical representation of the visuomotor map.

During visually guided movement, visual coordinates of target location must be transformed into coordinates appropriate for movement. To investigate the representation of this visuomotor coordinate transformation, we examined changes in pointing behavior induced by a local visuomotor remapping. The visual feedback of finger position was limited to one location within the workspace, at which a discrepancy was introduced between the actual and visually perceived finger position. This remapping induced a change in pointing that extended over the entire workspace and was best captured by a spherical coordinate system centered near the eyes.

Adult↗
PubMed1996

Clinical and psychosocial variables in different diagnostic groups: their interrelationships and value as predictors of course and outcome during a 14-year follow-up.

A 14-year follow-up study was conducted on 214 patients from the diagnostic groups schizophrenia, affective psychosis, and neurosis to determine the relationships between various clinical and psychosocial variables and to assess their value as predictors of long-term course and outcome. Particular emphasis was placed on ascertaining the interrelationships between the variables within the individual diagnostic groups. The results indicate that for schizophrenia, severity of disease at discharge from index hospitalization was the principal predictor of the number and duration of further hospitalizations. Furthermore, it predicted the severity of illness and social functioning at follow-up. For affective psychosis, the Global Assessment Scale score predicted the number and duration of further hospitalizations. Severity of illness, social functioning, and age at first hospitalization were predictors of occupational development. For neurotic disorders, severity of disease and social adjustment at discharge from index hospitalization were each predictors of themselves at final follow-up. In addition, age at first hospitalization was an important predictor of most course and psychosocial variables. Among the endogenous course variables within the schizophrenic group, the number and duration of further hospitalizations had a substantial bearing on severity of illness and social functioning at follow-up. For affective psychoses, indicators of occupational development and number of hospitalizations had an impact on severity of illness and social functioning at follow-up. Our findings reveal a good overall predictive value for the clinical and psychosocial variables within each of the diagnostic categories studied.

Adult↗
PubMed1993

Stability of diagnoses in various psychiatric disorders: a study of long-term course.

The frequency of diagnostic shift was investigated in 267 patients diagnosed with various psychiatric disorders according to the 9th revision of the International Classification of Diseases (ICD-9). Forty-six patients fulfilled the diagnostic criteria for schizophrenic psychosis, 71 for affective psychosis, 66 for neurotic disorder, 24 for personality disorder, and 40 for psychogenic reaction. The remaining 20 patients were diagnosed with heterogenous disorders. The mean follow-up time was 12.5 years. Every episode of inpatient treatment was diagnosed cross-sectionally. Patients with an initial episode of schizophrenic psychosis showed by far the greatest stability (93%). A high stability was found in patients diagnosed with neurotic disorders (79%). Forty-two patients with an index diagnosis of affective psychosis suffered more than one type of episode during the course of disease. The lowest stability was noted in patients with a psychogenic reaction (10%). Eleven percent of patients with a final diagnosis of schizophrenia had an index diagnosis of psychogenic reaction. Our findings demonstrate that the course of disease should be considered in making the final diagnosis.

Adult↗
PubMed1992

Falling spells associated with antidepressant drug treatment.

Six patients experienced falling spells concurrent with the intake of antidepressant drugs in high doses or in moderate doses combined with other psychotropic drugs. The close temporal correlation between drug ingestion and the falling spells and their immediate termination after reduction or discontinuation of medication suggests that these drugs caused the falls. Further factors predisposing to the falling spells remain to be defined.

Aged↗
PubMed1992

[The favorable effect of group housing on the occupational performance of psychiatrically handicapped patients].

A cohort of psychiatrically disabled persons was investigated to determine whether work performance changed after entry into a residential commune. Both before and after entering the commune, a differentiated spectrum of work opportunities graded according to performance requirements had been available. A clear enhancement of work performance was found following entry into the residential commune. In a further step, variables associated with above- or below-average increases in work performance were identified. On the whole, the results underscore the value of residential communes in the vocational rehabilitation of psychiatrically disabled persons.

Activities of Daily Living↗
PubMed1992

[Duration of inpatient treatment of various psychiatric disease categories. A follow-up study].

The frequency and duration of in-patient treatment in psychiatric and general hospitals was observed over an average 14-year period for 328 patients with different psychiatric diseases. Schizophrenics were more frequently admitted and spent longer in psychiatric institutions than all other diagnostic groups, but were admitted less frequently and for shorter periods to general hospitals. Patients suffering from organic mental illness and those with neurotic disorders had more frequent and longer periods of general hospital care. Drug dependent and neurotic patients were hospitalised more frequently and longer for psychiatric rather than for medical reasons in general hospitals. The total frequency and duration of psychiatric in-patient treatment was distinctly less frequent and of shorter duration for neurotic disorders as compared with schizophrenic or affective psychoses.

Adult↗
PubMed1991

[Cerebral ischemia in young adults].

An overview is given over etiology and prognosis of cerebral ischemias until the age of 40. In a time period of 19 years, 168 patients were diagnosed with cerebral ischemia until the age of 40 (91 females, 77 males). The most frequent etiology is premature atherosclerosis in patients with vascular risk factors (up to 50%). Cardiogenic embolism is responsible for 1 to 34% of the cases: cardiac valve diseases and endocarditis being the most frequent sources. In 2 to 19% a vasculitis is diagnosed. While infectious arteritis is especially frequent in countries of the third world, immunovasculitides are common in Europe and the USA. Noninflammatory vasculopathies include spontaneous or traumatic dissection, fibromuscular dysplasia and vascular malformations. A migrainous stroke is especially frequent in female smokers with intake of oral contraceptives. During pregnancy both sinus thrombosis and arterial ischemia occur. Hematologic causes for ischemia are polycythemia, thrombocytosis and genetic diseases (sickle cell anemia, AT3-deficiency). Cerebral ischemia may occur in connection with the ingestion of ergot-derivates. The prognosis of cerebral ischemia in young adults is better than in older stroke-patients.

Adolescent↗
PubMed1991

Psychiatric and somatic hospitalisations of different diagnostic groups: a long-term follow-up study.

Out of 328 cases with different diagnoses, including those without pathological findings at follow-up, the frequency and duration of in-patient treatment in psychiatric and somatic institutions was observed over an average 14-year period. Schizophrenics were more frequently and longer in psychiatric institutions, but they were less frequently and for shorter periods in somatic care compared with all other diagnostic groups. Patients suffering from affective psychosis had comparatively long psychiatric and somatic periods of hospitalisation. Dependents were hospitalised more frequently and longer for psychiatric rather than for medical reasons in somatic institutions. The total psychiatric in-patient treatment time was distinctly shorter for neurotic disorders compared with schizophrenic psychosis or affective psychosis cases.

Adult↗
PubMed1991

[Affective and schizophrenic syndromes in multiple sclerosis. Review of the literature and case reports].

Based on reports of three cases, the manic, depressive, schizophrenic and organic mental symptoms coincident to multiple sclerosis (MS) are described. The literature indicates an increased prevalence of psychiatric disturbances in MS. However, the relation between the psychiatric and the neurological disorders remains speculative. The temporal covariance and responsiveness to pharmacotherapy of the psychiatric and neurological symptoms of MS as well as the localisation of MS foci in diagnostic procedures (CT, MRI) are discussed in the light of the literature. The present authors hypothesize that every disturbance of the central nervous system (CNS), especially if chronic-inflammatory and multilocal, increases the probability that psychiatric symptoms will arise (as measured on a continuum ranging from "psychically conspicuous" to "psychically inconspicuous"). To this extent, then, MS would be comparable to other chronic-inflammatory CNS disorders such as AIDS, neuroborrelioses, syphilis and certain forms of viral encephalitis.

Adult↗