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Biomedical subjects

F Henn

Publications and source records attributed to F Henn.

17 recordsLinked to original sources
PubMed2005

Simple model for ac ionic conduction in solids.

We present a model for the ac conduction in ionically conducting solids that takes into account, in a simple way, the interaction between carriers. The Coulomb force forms an "ionic atmosphere" that exerts a restoring force on a central ion, whose motion corresponds to an overdamped oscillator. We consider the effect of the relaxation of the ionic atmosphere by introducing an additional equation for the displacement of the potential toward the particle position. The general behavior of the ac conductivity can be understood in terms of two types of motions: motion of the bound ion at high frequencies determined by microscopic friction, and a much slower motion coupled to the surrounding carriers relaxation at low frequencies.

Journal Article↗
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

Needs for mental health care and service provision in single homeless people.

BACKGROUND: Specific problems in sampling methodology, case-finding strategies and a standardised needs assessment in mentally ill homeless people have contributed to their being neglected as a mental health care clientele. METHOD: We assessed a representative sample of homeless people (n=102) in the highly industrialised city of Mannheim (Germany) regarding their prevalence of mental disorders (using the SCID) and their needs for mental health care (using the NCA). RESULTS: We found high prevalences, with 68.6% of all assessed homeless persons having a current mental disorder. Thus, needs for mental health care were very common, with unmet needs predominating in all problem areas, which was supported by a very weak service utilization. Thus, even in a region with a comprehensive community mental health care network, like the study area, mentally ill homeless people are widely under-provided. CONCLUSIONS: Results suggest that the traditional shelter system for homeless people carries most of the mental health care burden for their clientele and must be supported by adequate interventions from community-based mental health care services. A closer connection of both sectors and a better co-ordination of the care offers seems to be a prerequisite for helping to reduce unmet mental health care needs in this specific high-risk group.

Adolescent↗
PubMed2001

Mice with targeted mutations of glucocorticoid and mineralocorticoid receptors: models for depression and anxiety?

Impaired corticosteroid receptor signaling is a key mechanism in the pathogenesis of stress-related psychiatric disorders such as depression and anxiety. Since in vivo expression and functional studies of corticosteroid receptors are not feasible in the human central nervous system, such analyses have to be done in animal models. Transgenic mice with mutations of corticosteroid receptors are promising tools, which allow us to investigate the role of these proteins in the pathogenesis of symptoms characteristic for depression and anxiety. This review summarizes the neuroendocrinological and behavioral findings that have been obtained in six different mouse strains with specific mutations that influence the expression or the function of the glucocorticoid or the mineralocorticoid receptor (MR). The analyses of these mice helped to define molecular concepts of how corticosteroid receptors regulate the activity of the hypothalamic-pituitary-adrenal (HPA) system. Furthermore, some of these mutant mice exhibited characteristic alterations in behavioral tests for anxiety and despair. However, so far, none of the mouse strains described here can be viewed as an animal model of a specific psychiatric disease defined by common diagnostic criteria. Using high throughput technologies for the identification of genes regulated by glucocorticoid receptor (GR) and MR in brain areas responsible for specific symptoms of stress-related disorders will yield potential new drug targets for the treatment of depression and anxiety.

Animals↗
PubMed2001

[How do mentally ill homeless persons evaluate their quality of life].

Besides pronounced deficiencies in psychiatric research concerning homeless mentally ill in Germany, studies concerned with the quality of life of homeless mentally ill were missing until now. This study reveals in a representative sample of 102 homeless people from the City of Mannheim, Germany that--compared to the homeless without psychiatric disorders of the sample--the mentally ill homeless (prevalence 68.6%) have significantly different subjective views of their quality of life regarding the items "state of health", "physical capabilities" and "support from others". The differences were even stronger if the homeless mentally ill were compared to a group of non-homeless mentally ill schizophrenic patients (n = 104), cared for in the City's well-equipped community care services. Community care patients reported a significantly better quality of life in respect of 11 items. These results were seen as a success of the concept of community-based mental health care. The consequences for improving care strategies for homeless mentally ill are discussed.

Activities of Daily Living↗
PubMed2000

Acute stress induced modifications of calcium signaling in learned helpless rats.

Previous reports have demonstrated reduced elevations of free intracellular calcium concentration in blood cells of depressed patients after various stimuli. Therefore, a disturbance of intracellular calcium (Ca2+) homeostasis has been postulated to be involved in the pathophysiology of mood disorders. It was the aim of the present study to investigate whether Ca2+ signaling was affected in spleen T-lymphocytes of rats submitted to a learned helplessness paradigm, an animal model of depression with a high level of construct, face and predictive validity. In addition, we tested for effects of acute stress on the Ca2+ signaling in helpless rats, as compared to non-stressed rats. It was found that mitogen-induced Ca2+ signaling only tended to be reduced in helpless rats. However, when helpless rats were submitted to acute immobilization stress, Ca2+ signaling appeared to be significantly blunted, whereas the same stressor did not affect Ca2+ signaling in the non-helpless control rats. These acute stress-induced differences in Ca2+ signaling were not paralleled by a differential increase in plasma corticosterone. It is hypothesized that blunted Ca2+ signaling, as assessed in spleen T-lymphocytes of helpless rats, may be a correlate of the increased vulnerability of helpless rats to acute stressors.

Animals↗
PubMed1998

Production of the Fos protein after contextual fear conditioning of C57BL/6N mice.

Male C57BL/6N mice were chosen to determine Fos production during acquisition of context-dependent fear and after re-exposure to the conditioning context. Fear-conditioning was induced by a single exposure of mice to a context followed by an electric shock. Control groups consisted of mice exposed to context only (Context group) or to an immediate electric shock. When contextual retention was measured 24 h after conditioning (retention test 1), significant contextual generalization was observed. However, when animals were exposed to a different context from days 2-5 after conditioning and then tested for retention on day 6 (retention test 2), generalization was markedly reduced. After the training, the fear-conditioned mice produced higher Fos levels than mice exposed to an immediate shock in the hippocampus, medial amygdaloid nucleus and parietal somatosensory cortex. Both shock groups produced significantly more Fos than the Context group in the central nucleus of the amygdala. After retention test 1, fear-conditioned mice generated more Fos in the hippocampus and central amygdaloid nucleus than the two control groups. However, all groups exhibited similarly low Fos production after retention test 2. The results demonstrated that simultaneous Fos production in the hippocampus, central and medial nuclei of amygdala and somatosensory parietal cortex closely paralleled the ability of mice to acquire conditioned fear. In contrast, Fos production after the retention tests did not correlate with the expression of conditioned fear.

Amygdala↗
PubMed1992

Low cerebellar metabolism in medicated patients with chronic schizophrenia.

Because of the frequent association of cerebellar structural defects with schizophrenia, the authors reanalyzed the metabolic brain images of patients with chronic schizophrenia to assess if they had abnormalities in cerebellar metabolism. They used carbon-11-2-deoxyglucose and positron emission tomography to study 18 medicated patients with chronic schizophrenia and 12 normal comparison subjects. Patients with schizophrenia showed significantly lower absolute and relative metabolism in the cerebellum than normal subjects.

Adult↗
PubMed1991

Modulation of [3H]paroxetine binding to the 5-hydroxytryptamine uptake site in an animal model of depression.

The effects of learned helplessness on the 5-hydroxytryptamine (5-HT) uptake site were studied in rats using [3H]paroxetine binding. This ligand was chosen because it was demonstrated to label directly the 5-HT uptake site whereas the [3H]imipramine binding site has been demonstrated to be heterogeneous in nature. Moreover, [3H]imipramine appears to bind to a presynaptic recognition site different from the uptake site. Exposure to uncontrollable shock training and testing resulted in an overall increase in [3H]paroxetine binding in all the groups studied [nonhelpless (NLH), learned helpless (LH), spontaneously helpless (SPLH)] as compared to naive controls (NC). However, the increase in [3H]paroxetine binding was significantly higher in the LH and SPLH groups. The maximum number of [3H]paroxetine binding sites in the rat hippocampus was increased significantly in learned helpless rats (LH and SPLH) at day 4 and day 30 after the shock escape test as compared to NC and NLH rats. By contrast, in the rat hypothalamus the maximum number of [3H]paroxetine binding sites was reduced significantly in the LH rats as compared to naive controls and NLH rats during the same time course. There was no change in [3H]paroxetine binding sites in any other brain regions examined in LH, NLH, and NC rats. The results suggest that a hippocampal hypothalamic connection might play a role in the serotonergic mediation of learned helpless behavior.

Animals↗
PubMed1990

Effects of bilateral adrenalectomy on the induction of learned helplessness behavior.

In the learned helplessness model of depression, naive Sprague-Dawley rats are exposed to a 40-minute uncontrollable shock training and are subsequently tested in a shock escape paradigm. "Helpless rats" exhibit 11 to 15 failures in a 15-trial test while "nonhelpless" rats and naive controls score 0 to 5 failures in the same test. We report on the effect of bilateral adrenalectomy on the induction of learned helplessness. Most of the adrenalectomized rats (70%) became helpless whereas sham controls responded to the training and testing similarly to naive nonoperated rats (20% to 30% helpless). This increase in behavioral deficits after adrenalectomy was reversed by administration of corticosterone, the naturally occurring glucocorticoid in rat. We conclude that secretion from the adrenal cortex is necessary for the incorporation of a learned response after stress and that a dysregulation of the hypothalamic-pituitary-adrenal axis seems to be involved in helpless behavior.

Adrenalectomy↗
PubMed1981

On the Ca2+-permeability of neurons and glia.

Fractions enriched in pinched-off nerve terminals and astrocytic glial cells were used to analyse the permeability of Ca++ of the two membranes. Three experimental models were used to illustrate a principle difference of the excitatory versus the no-excitatory cell membrane, with respect to Ca-permeability. The effect of an increased [Ca++] on 86Rb+ and 3H-GABA transport was measured in medium containing low and high [K+]. The possibility of GABA stimulation of release of preaccumulated 45Ca+4 with low and high [K+] was compared in neurons and glia. Finally, the effect of depolarizing [K+] on the transmembranal Ca++-gradient was measured by comparing the efficacy of the Ca-ionophore A23187 to depolarize or to inhibit the 3H-GABA uptake at these different [K+]. The data essentially confirms the picture of a potential dependent Ca++-permeability in the neuron, while the permeability of the glial cells seems a "true" constant. It might be relevant to suggest the astrocyte a role as a "Ca-buffer" with possibilities to control extracellular Ca+4 in cases of hyperactivity, this in analogy with what has been suggested for K+.

Animals↗