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Biomedical subjects

A Jost

Publications and source records attributed to A Jost.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1984

Effect of serum on organogenesis of the rat testis in vitro.

It was observed previously that primordia of fetal rat testes when explanted in vitro in a synthetic medium at the outset of sexual differentiation differentiate seminiferous cords during the following days, but that the addition of 15% fetal bovine serum prevents this morphogenesis. In the present study, human, horse, bovine calf, and rat sera were shown to exert the same effect. Very low concentrations of human or fetal bovine serum (0.5 or 1%) were sufficient to produce the serum effect, which was only slightly reduced when the serum was heated. The serum activity was not removed by dialysis (membrane cut-off 15 000), but it disappeared after treatment with trichloroacetic or perchloric acids or after trypsin digestion. Partial purification of the active factor(s) from human serum was achieved by successive gel filtration, affinity chromatography, and ion exchange chromatography. Analysis of the active fractions by electrofocusing and immunoelectrophoresis placed the activity within the alpha globulin group. Among a series of purified serum proteins tested, alpha 2-HS-glycoprotein was found to exhibit the serum effect, though this activity was heat labile.

Animals↗
PubMed1984

Dissociation between testicular organogenesis and endocrine cytodifferentiation of Sertoli cells.

Differentiation of the rat testis from the undifferentiated primordium begins with the appearance of a new cell type characterized by a large and clear cytoplasm. These cells aggregate, enclose germ cells, and progressively form seminiferous cords. Therefore, they were considered primordial Sertoli cells. A similar process was obtained in vitro in explants cultured in a synthetic medium. On the contrary, when fetal calf serum was added to the medium, the organization of seminiferous cords was impaired; large clear cells appeared, but they did not aggregate. Instead, they remained scattered throughout the abnormal gonad. The present experiments were undertaken to verify whether these cells are in fact Sertoli cells. The production of Müllerian inhibitor is a marker of fetal Sertoli cells. Therefore, undifferentiated gonadal primordia from 12-day 16-hr old male rat fetuses were cultured for 2 days in vitro with serum and then associated for 3 days with 14.5-day-old sex ducts from female fetuses. Müllerian ducts were inhibited as well by the abnormal cordless gonads as by those with differentiated sex cords. These experiments confirm previous views on testicular development and demonstrate that differentiation of Sertoli cells may take place quite independently of the testicular cord formation.

Animals↗
PubMed1984

Initial phases of the rat testis differentiation in vitro.

Rat gonadal primordia with their supporting mesonephroi were explanted in vitro at the undifferentiated stage (12 days 16 h after fertilization), at the outset of testicular differentiation (13 days 9 h) or when already containing seminiferous cords. The younger foetuses were sexed with the sex chromatin test in the amniotic membrane. The basal medium was CMRL 1066 and the culture period, 1 to 4 days. Testicular differentiation resulted from the appearance of large clear cells, the primordial Sertoli cells, and from their aggregation into seminiferous cords. Addition of 15% foetal calf serum to the medium prevented the differentiation of seminiferous cords, but large clear cells appeared. In testes from 14- or 15-day-old foetuses, the seminiferous cords disintegrated under the influence of serum. The serum did not prevent the differentiation of Sertoli cells, but impaired organogenesis or maintenance of the early seminiferous cords. The results support previous histological observations on the initial stages of testicular differentiation.

Animals↗
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↗
PubMed1982

[Precocious production of müllerian inhibitor by the fetal rabbit testis].

The production of müllerian inhibitor (or anti-müllerian hormone) by the testes of the Rabbit fetus was studied in vitro by co-culturing them with castrated genital tracts from 14.5 day old female Rat fetuses for three days. Under these conditions testes from 14 day old Rabbit fetuses were inactive. The testes from 15, 16 and 17 day old fetuses in which seminiferous cords are forming, had anti-müllerian activity, the older the stronger. In vivo this activity does not prevent the Müllerian ducts from growing in male Rabbits as well as in females until near to day 20; in vitro the fetal Rat ducts also grew in length despite the testicular anti-müllerian activity.

Animals↗
PubMed1981

[Effect of fetal calf serum on the in vitro differentiation or maintenance of the seminiferous cords of the testis of the fetal rat].

The differentiation of seminiferous cords can be obtained in in vitro cultures, in a synthetic medium, of undifferentiated fetal Rat gonads. In older testes the seminiferous cords are maintained under these conditions. On the contrary, adding 15% fetal Calf serum to the medium prevents the differentiation of the seminiferous cords or provokes the disruption of the already formed cords (days 14 and 15). These actions are exerted upon the fetal Sertoli cells.

Animals↗