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Biomedical subjects

A Jost

Publications and source records attributed to A Jost.

At least 19 recordsLinked to original sources
PubMed1992

[Clinical and laboratory differentiation of alcohol withdrawal syndrome ("predelirium") and alcoholic delirium].

In a retrospective study, data from 99 male and female inpatients with alcohol withdrawal syndrome or alcohol withdrawal delirium, treated between 1977 and 1987, were analyzed. DSM-III criteria were used to assign the diagnosis of either withdrawal delirium (with obligatory clouding of consciousness) or alcohol withdrawal syndrome (without disturbances of consciousness and/or perception). No statistically significant differences between the two groups were found with respect to the red and white blood count, liver enzymes, and electrolytes. Significant differences were found in calcium levels, lymphocyte counts, and in electrophoresis. However, these differences are of no use for diagnostic purpose. Moreover, they are unspecific with respect to etiology. Hence, the distinction between alcohol withdrawal syndrome and alcohol withdrawal delirium can only be made clinically, i.e., it is dependent on the presence or absence of a clouded consciousness. This is in line with the findings published by other investigators. In the light of our metabolic findings, alcohol withdrawal syndrome and alcohol withdrawal delirium represent the two extremes of a continuum rather than two separate nosological entities.

Adult↗
PubMed1991

Sertoli cells and testicular differentiation in the rat fetus.

The fetal testis is not merely a precursor of the adult organ: it is indeed an endocrine gland whose function is the masculinization of the fetus. It differs physiologically and morphologically from the adult testis. In this paper, the first stages of testicular differentiation in the rat are described, with special emphasis on the ultrastructural aspects. At the stage of 13.5 days after fertilization, the first Sertoli cells differentiate; they are characterized by a voluminous and little electron dense cytoplasm, a well-developed RER formed by vesicles and short cisternae filled with a flocculent material. Progressively, they polarize and adhere to one another by adherens-like junctions and cytoplasmic interdigitations to form the differentiating seminiferous cords. In the basal part of the Sertoli cells, a mat of microfilaments differentiates under the plasmalemma, while cytoplasmic blebs protruding in the extracellular space tend to disappear. A continuous basal lamina delineating the seminiferous cords begins to appear on day 14.5 and becomes widespread on day 15.5. These observations, when compared with other data from the literature, emphasize the fact that the differentiation of the Sertoli cells is the first morphological event during testicular differentiation. A possible role of the Sertoli cells in the subsequent organogenesis of the testis is suggested.

Animals↗
PubMed1988

Control mechanisms of testicular differentiation.

In this paper the importance of unknown factors responsible for the initial differentiation of a gonadal primordium is stressed. The hypothesis that in the absence of testis determining genes (TDG) the indifferent gonad is programmed to become an ovary is considered further. The TDG(s) are expressed only among cells already marked as gonadal cells, and they seem mainly to change the chronological sequence and intensity of expression of processes common to both sexes. The chronology of the normal events necessary for testicular differentiation and the fact that some of these events can be dissociated from one another under experimental conditions in vitro, suggest that many genes are involved in testicular differentiation and that the so-called testis-determining genes are probably regulatory genes.

Animals↗
PubMed1988

Experimental control of the differentiation of Leydig cells in the rat fetal testis.

In the developing fetal testis, in vitro as well as in vivo, two kinds of endocrine cells differentiate successively: Sertoli cells, which produce the Müllerian inhibitor (or anti-Müllerian hormone) and aggregate with germ cells into seminiferous cords; and Leydig cells, which release androgens. Serum added to the synthetic culture medium prevents the morphogenesis of the seminiferous cords but not the cytodifferentiation of the endocrine cells. L-Azetidine 2-carboxylic acid (LACA), a proline competitor, introduced into the medium also prevents differentiation of seminiferous cords. In the present experiments, the effects of LACA on the endocrine cells were studied. It did not suppress production of the Müllerian inhibitor, but it opposed differentiation of Leydig cells. Histochemically detectable 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) was virtually absent and the release of testosterone, delta 4-androstenedione, 17-hydroxyprogesterone, or progesterone into the medium became undetectable. Moreover, dibutyryl cAMP added to the medium during the final day in vitro had very little effect on the parameters of steroidogenesis. An excess of proline added to the LACA-containing medium permitted normal morphogenesis of seminiferous cords, normal steroidogenesis, and normal response to cAMP. LACA did not prevent the appearance of 3 beta-HSD activity in the adrenals, nor did it reduce the expression of laminin and fibronectin (data not shown) in the mesonephric structures as much as in the testes. The differentiation of the testis and especially of the Leydig cells appears to have special requirements for proline.

17-alpha-Hydroxyprogesterone↗
PubMed1986

[Isolation by binding to ultrafiltration membranes of a testicular factor limiting the number of germ cells in fetal ovary of rats in vitro].

The medium used for culturing in vitro fetal or neonatal testes, when used subsequently to culture for 4 days ovaries from 13.5 day old rat fetuses, has the property of severely limiting the number of ovarian germ cells. The non-dialysable factor(s) responsible for the observed effect binds to ultrafiltration membranes (Diaflo, Amicon) and can be eluted from these membranes with fresh medium added 1 M NaCl.

Animals↗
PubMed1986

[New data on the hormonal requirement of the pregnant rabbit: partial pregnancies and fetal abnormalities after treatment with a hormonal antagonist given at a sub-abortive dosage].

Evolution of pregnancy in rabbits depends upon ovarian progesterone. A deficiency in ovarian hormones was observed a long time ago to result either in abortion or in "partial pregnancy" or even in fetal anomalies. Administration to pregnant rabbits, from day 11 on, of a hormonal antagonist known for its anti-progesterone activity, RU486, at a sub-abortive dosage, reproduces the effects of ovarian hormone deficiencies.

Abnormalities, Drug-Induced↗
PubMed1985

Dissociation between testicular morphogenesis and functional differentiation of Leydig cells.

The aim of the study was to determine whether Leydig cells differentiate in vitro in gonads in which the formation of seminiferous cords is prevented by culture in a medium containing fetal calf serum. Appearance of 3 beta-hydroxysteroid dehydrogenase-positive cells and release of testosterone in the medium occurred at the same age irrespective of whether or not the gonads developed seminiferous cords. It is concluded therefore that testicular morphogenesis with the formation of seminiferous cords is not a prerequisite for the emergence and functional differentiation of Leydig cells.

3-Hydroxysteroid Dehydrogenases↗
PubMed1985

[Effect of the fetal testis on the number of germ cells in the fetal ovary of rats in vitro].

When ovaries from 13.5-day-old fetuses are explained and cultured in vitro for 4 days in a synthetic medium, the number of germ cells increases 6 fold, on average. This increase is only approximately 2 fold if a pair of 16.5-day fetal testes is cultured together with the ovaries or if the ovaries are cultured in a medium in which testes have previously been grown for 4 days. The effect of the latter medium persists if it is dialysed against fresh medium, which suggests that the conditioned medium contains one or several substance(s) of molecular weight superior to the cut-off of the membrane. The testicular effect seems to be effective mainly during the final phase of intense multiplication of the germ cells.

Animals↗
PubMed1985

[Effect of an analog of proline (L-azetidine-2-carboxylic acid) on in vitro differentiation of the rat fetal testis].

The initial stages of the development of the seminiferous cords involve the differentiation and the aggregation of primordial Sertoli cells opposite to cells which acquire a mesenchymal-like aspect. The hypothesis that the development of the seminiferous cords depends on epithelial-mesenchymal relations between the two cell types was submitted to experimental test. Male gonadal primordia of rat fetuses were cultured in vitro in a synthetic medium containing the proline competitor, L-Azetidine-2-Carboxylic Acid. This drug is known to disturb the synthesis and secretion of collagen and proline-containing proteins. It prevents testicular organogenesis or destroys it if it has begun. It suppresses the expression of laminin and fibronectin in the gonadal primordium. These observations are taken as evidence that cellular correlations of the epithelial-mesenchymal type play a role in the development of the testis as they do in that of other organs.

Animals↗
PubMed1984

Pseudohypergonadotropinemia and pseudohyperprolactinemia induced by heterophilic antibodies?

The serum of 20 apparently hypergonadotropic and/or hyperprolactinemic patients (14 females, 6 males, ages 13-75 years) without evidence of neoplasia or pituitary adenomas was found to contain a large amount of molecular material (MW ca. 100,000) resulting in factitiously elevated levels of peptide hormones when measured by double-antibody radioimmunoassay with a long second incubation time. The interference by this material with the test system could be avoided by using polyethylene glycol (PEG) for the separation of free from bound antigen, or by preincubation of the samples with normal rabbit serum. No definite disease process can as yet be linked to these findings. They rather seem to be caused by the presence of heterophilic antibodies in serum, as the serum of approximately one half of the patients was found to give a positive Paul-Bunnell test. Moreover, the beta hCG activity in the urine of these patients was low, probably as a result of the low clearance of substances with igh MW. It is therefore suggested to apply to following diagnostic measures before clinical consequences are being considered in a case of hypergonadotropinemia and/or hyperprolactinemia without pertinent clinical findings: (1) validation of the immunoassay, (2) preincubation of the samples with serum from other species, (3) the use of another separation procedure than the double-antibody method, and (4) measurement of the respective hormone in urine.

Adolescent↗
PubMed1983

Genetic and hormonal factors in sex differentiation of the brain.

The mode of chromosomal sex determination is opposite in mammals and in birds, the heterogametic sex being male in the former and female in the latter. This difference is parallel by a basic program of development of sex characters in the absence of gonads; this program is feminine in mammals and male in birds. 'Defeminization' is produced by the testes in male mammals, and 'demasculinization' is produced by the ovary in female birds. The same difference prevails in the permanent organizational effects of sex hormones on the neural structures mediating sex behavior, during a critical period. In mammals, especially in the rat, testosterone released by the testis controls the various sex characters. It can work as such, or after being converted locally into dihydrotestosterone or estradiol, in the cells of the end organ. Estradiol seems to be the actual intracellular 'defeminizing' agent in the central nervous system. In birds, especially in quail, accumulating data suggest that estradiol is the intracellular 'demasculinizing' agent.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗