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Biomedical subjects

B Claustrat

Publications and source records attributed to B Claustrat.

144 records · Page 8Linked to original sources
PubMed1976

Leydig-cell agenesis: a cause of male pseudohermaphroditism.

We studied a 35-year-old patient with female external genitalia, primary amenorrhea and XY karytotype. Plasma testosterone was 10 ng per deciliter, which did not change after administration of human chorionic gonadotropin, increased to 22 ng per deciliter after ACTH, and decreased to 0.9 ng per deciliter after dexamethasone. Plasma delta 4-androstenedione, dehydroepiandrosterone and 17-hydroxyprogesterone were in the normal range. Plasma luteinizing hormone was high, but follicle-stimulating hormone normal (7.5 mlU per milliliter). There were two testes with epididymis and vas deferens, but no Mullerian structures. Microscopical examination showed hyalinization of tubules, which were lined by normal Sertoli cells and occasional immature germ cells. No Leydig cells were seen. After castration follicle-stimulating hormone increased to 43 mlU per milliliter. We conclude that this case of male pseudohermaphroditism was probably due to a Leydig-cell agenesis, that the epididymis and vas deferens can be developed in such a condition and the follicle-stimulating hormone secretion is regulated, at least in part, by a non-androgen substance secreted by Sertoli cells.

Adrenal Glands↗
PubMedDate not supplied

Regulation of melatonin production by catecholamines and adenosine in a photoreceptive pineal organ. An in vitro study in the pike and the trout.

The pineal organ of fish contains photoreceptor cells with structural and functional analogies to retinal photoreceptors. In these cells, the light/dark (LD) cycle influences the production of melatonin by controlling the activity of one of its synthetizing enzymes, serotonin N-acetyltransferase (NAT). The daily rhythm in NAT activity is generated endogenously in the pike but not in the trout pineal. We report here that in addition to the LD information, chemical factors are also involved in the control of melatonin production. Adenosine and two of its analogs stimulated or inhibited NAT activity and melatonin release in cultured pike and trout pineals, depending on the experimental conditions. It is believed that the nucleoside, produced locally, exerts a modulatory role on the neurohormonal output via still enigmatic mechanisms, involving a transmembranous carrier. Nocturnal melatonin production in cultured pike pineals was inhibited by alpha-adrenergic agonists and stimulated by a beta-adrenergic agonist. No effect could be induced in trout pineals cultured under similar conditions. Because melatonin production by pineal photoreceptors is apparently regulated by both light and chemical inputs, we propose they might be multieffector cells.

Adenosine↗
PubMedDate not supplied

5-Methoxypsoralen inhibits 6-hydroxylation of melatonin in the rat.

Pharmacokinetic studies of exogenous melatonin (100 or 1 micrograms) administered to 5-methoxypsoralen (MOP)-treated rats, showed that MOP administration induced an increase in the half-life of melatonin from 22 to 67 min. This delayed degradation of melatonin was the consequence of 5-MOP-induced inhibition of the 6-hydroxylation of melatonin. Under in vitro experimental conditions, 5-MOP did not affect melatonin synthesis and release. These results demonstrate that the elevated plasma melatonin concentrations observed in vivo following 5-MOP administration is due to inhibition of the hydroxylation of endogenous melatonin.

5-Methoxypsoralen↗
PubMedDate not supplied

[Seasonal rhythm of melatonin in manic depressive patients].

Melatonin is secreted by the pineal gland with a circadian and a circannual rhythm. For some authors the circadian rhythm is modified during depressive states. The present study evaluates the melatonin circannual rhythm in five manic-depressive patients. Each patient is clinically and biologically evaluated every month during one year. The results of the present study show a lack of clinical relapse and a lack of seasonal variation of plasma melatonin level.

Adult↗
PubMedDate not supplied

[Melatonin and schizophrenia].

Many research studies have been conducted with melatonin, a pineal hormone, in psychiatry. Studies with melatonin in schizophrenic patients are rare. Blood plasma samples were drawn at 24 hours and 12 hours in 23 schizophrenic subjects and 26 controls, during the same season. Plasma melatonin levels were obtained using a specific radioimmunoassay technique. The 24 hours levels significant decreased in schizophrenic patients compared with controls (p less than 0.01). Methodology, specificity of results and concomitant study of cortisol levels are discussed.

Adult↗
PubMedDate not supplied

[Daily profiles of melatonin, cortisol and gonadotropins in 8 adolescents with anorexia nervosa].

From a biological study of 8 patients with anorexia nervosa and an analysis of the daily profiles of gonadotropins, cortisol and melatonin, the authors discuss the possible relationship between anorexia nervosa and affective disorders. At the initial phase of the illness, plasmatic levels of FSH, LH and oestradiol were very low. 24-hour plasma cortisol values were comparable with those of a depressive population; when weight loss was equal to or higher than 25% of the initial weight, there was no suppression by dexamethasone. The daily profile of melatonin was maintained, with melatonin plasma levels significatively higher than in a control group of depressed patients.

Adolescent↗
PubMedDate not supplied

[Effect of acute administration of antidepressive agents at 2 P.M. on plasma and pineal levels of melatonin in the rat].

The authors measured the effect of different antidepressant drugs on the pineal production of melatonin in order to see if this test can be used in an antidepressants screening protocol. Six antidepressant drugs belonging to different pharmacologic classes have been tested. The results show that all the molecules used enhance the plasmatic and pineal concentration of melatonin. However the selectivity of this test must be reinforced by using classical methods for the detection of an antidepressant effect.

Animals↗
PubMedDate not supplied

[Melatonin. Chronobiologic peripheral endocrine index in depressive states].

The chronobiological studies with melatonin constitute valid arguments to consider melatonin as a peripheral index of depressive disorders. In a group of patients with major depression, we reported a lowering of melatonin nocturnal plasma levels, associated with cortisol hypersecretion. A similar lowering of melatonin was observed in a group of patients with cluster headaches, but without quantitative modification of cortisol secretion. Other studies are necessary in order to determine wether melatonin may be considered as a "state marker" of depression itself or a marker of the genetic vulnerability to depression.

Adult↗
PubMedDate not supplied

Plasma 6-hydroxymelatonin, 6-sulfatoxymelatonin and melatonin kinetics after melatonin administration to rats.

A specific, sensitive and reproducible high-performance liquid chromatographic (HPLC) method is described for the simultaneous measurement of 6-hydroxymelatonin and melatonin in rat plasma. Using this technique, a dose-dependent increase in 6-hydroxymelatonin concentration was observed 10 min after administration of different doses of melatonin. Plasma 6-hydroxymelatonin represented 1% of plasma melatonin, irrespective of the melatonin dose administered. After administration of 100 micrograms melatonin, 6-hydroxymelatonin could be detected in plasma from 7.5 to 60 min. In the same experiment, plasma 6-sulfatoxymelatonin concentrations determined by radioimmunoassay could be detected from 7.5 to 120 min. This HPLC technique allows the measurement of 6-hydroxymelatonin together with melatonin. Combined with an RIA for 6-sulfatoxymelatonin, it could be useful in determining the site of action of drugs affecting melatonin metabolism.

Animals↗