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A Jost

Publications and source records attributed to A Jost.

At least 55 records · Page 3Linked to original sources
PubMed1981

Early stages of testicular differentiation in the rat.

The initial phases of the development of the seminiferous cords (future seminiferous tubules) were studied with histological techniques and with electron microscopy. On day 14 after fertilization, seminiferous cords are well differentiated in the anterior part of the testis near the mesonephric tubules. They comprise Sertoli cells which encompass the primordial germ cells. The Sertoli cells shows an expanded clear cytoplasm and microfilaments beneath the outer surface; they differentiate complex contact zones. On day 13 a few cells localized near the mesonephric tubules display the characteristics of the Sertoli cells. These cells become more and more numerous. They aggregate and they form the seminiferous cords. The primordia of male gonads explanted in vitro on the mesonephros, realize testicular organogenesis in a synthetic medium. Adding 15% fetal calf serum to the medium prevents the morphogenesis of the testicular cords, although the Sertoli cells seem to differentiate morphologically and physiologically. In these gonads differentiation of the Sertoli cells was obtained but their aggregation and the morphogenesis of the seminiferous cords were prevented. This gives new insights into testicular morphogenesis and probably provides an experimental model for a new type of gonadal anomaly.

Animals↗
PubMed1980

[Pleuro-pulmonary actinomycosis. Report of 4 cases].

Four cases of pulmonary actinomycosis are reported. Two cases (1978, 1979) were diagnosed on microscopic examination of lung parenchyma excised on suspicion of bronchogenic carcinoma. The third case was diagnosed retrospectively by reexamining the slides of a patient operated on in 1965, who presented with a similar history and chest X-ray. The fourth was diagnosed at autopsy in a patient who committed suicide. Actinomycosis is a rare disease which affects the lung in 15--20% of cases. Despite its name, actinomycosis is not due to a fungus but to an anaerobic gram-positive bacillus. The germ is a saprophyte of the human digestive tract and is very sensitive to penicillins. It may become pathogenic in a compromised host and usually produces cervico-facial lesions which develop by continuity from mouth mucosa. Abdominal or, more rarely, pulmonary lesions are due to ingestion or inhalation of infected material. Chest X-ray appearance of pulmonary actinomycosis mimics that of bronchogenic carcinoma. Actinomyces culture is difficult, and diagnosis is often based on microscopic examination of the surgical specimen only. Antibiotic therapy is a mandatory complement to surgical treatment.

Actinomyces↗
PubMed1980

The initial phases of testicular organogenesis in the rat. An electron microscopy study.

The paper is devoted to the study of the very first stages of testicular organogenesis in the rat, i.e. to the study of the initial stages of formation of the seminiferous cords. It takes over and extends the results of a previous histological study (Jost, 1972). The tissues were fixed with glutaraldehyde or glutaraldehyde-paraformaldehyde and post-fixed with osmium tetroxide. Examination with the optical microscope of semi-thick sections confirms that the differentiation begins at the stage of 13 days after fertilization; an increasing number of primitive Sertoli cells appear, first in the depth of the gonad, join each other and form the seminiferous cords. Study with the electron microscope reveals three characteristic criteria of the early differentiation of the Sertoli cells, namely : 1) an abundant cytoplasm, only slightly dense to electrons and containing short laminae or vesicles of rough endoplasmic reticulum; 2) complex contact zones involving infoldings and interdigitations of the membranes; 3) a layer of microfilaments beneath the flattened surface of the cells, that limits the outer surface of the seminiferous cords. These differentiation processes taking place at the stage of 13 days, are described.

Animals↗
PubMed1980

[Gallbladder duplication and accessory gallbladders].

Double gallbladders represent a large spectrum of malformations; on an embryological base these anomalies are divided into true duplications and accessory gallbladders according to whether both cystic ducts are fused or separated to join the common bile duct. The authors have observed four cases one of which is discussed for diagnostic and therapeutic considerations.

Adult↗
PubMed1980

Development of the thyroid gland in the rat fetus in vivo. An ultrastructural and radioautographic study.

A study of the differentiation of the thyroid follicles was carried out in rat fetuses between day 14 of pregnancy, when cellular polarization begins and day 18, when completely formed follicular lumina are differentiated. After day 18, only the shape and the size of the lumina undergo modifications. The mechanism of folliculogenesis involves the participation of several structures. At 14 days of pregnancy, adherens type contact zones with membrane densification appear between the cells. These junctional zones spread out and form infoldings which deeply penetrate the cytoplasm. Golgi vesicles migrate to these zones and they fuse among themselves and with the contact membranes : follicular cavities result which can be recognized as soon as day 16 of pregnancy. A radioautographic study showed the beginning of iodide organification at 17 days 11 hours of pregnancy. From this time onward silver grains were seen over the follicular cavity, even it is still incompletely formed.

Animals↗
PubMed1979

[Plasma growth hormone in the rabbit fetus. Relation to maturation of the liver and lung].

Day 25 after insemination is a date of peculiar importance in the maturation of several organs in the Rabbit fetus. From day 25 onward the fetal liver stores increasing amounts of glycogen and the lung stores increasing amounts of lecithins, concomitant with sudden rise in the activity of lung phosphatidic-acid phosphohydrolase. Earlier studies on decapitated fetuses established that glycogen storage in the liver is dependent on a dual hormonal control, comprising a pituitary hormone like growth hormone or prolactin (some placental hormones share the same activity) and corticosteroids (Jost, 1961). Since the variations in endogenous corticosteroids do not seem to herald these liver or lung changes (Mulay et al., 1973), a study was made of growth hormone. Plasma immunoreactive growth hormone--determined with a heterologous Rat system (Kervran et al., 1976)--increases eightfold between days 23 and 25. During the same time plasma prolactin does not change according to McNeily and Friesen, 1978, and to unpublished data obtained with Dr McNeilly. In preliminary assays, Rat growth hormone was seen to increase phosphorylase "a" activity in the lung of 18.5 day-old Rat fetuses, thus anticipating normal development. We suggest that growth hormone plays a role in initiating liver and lung maturation.

Age Factors↗
PubMed1979

Glucocorticosteroid receptors in the liver of normal and decapitated rabbit foetuses.

The affinity and the number of receptor sites for the synthetic steroid triamcinolone acetonide were studied in the livers of foetal rabbits. Twenty-two-, 24- and 29-day-old control and 29-day-old foetuses decapitated on day 22 were used to determine whether a change in steroid receptors occurs in the liver when it accumulates glycogen, and whether decapitation impairs such a change. Steroid receptors were found as early as day 22, when they were as numerous (0.091 pmol/mg protein) as on days 24 (0.098 pmol/mg) and 29 (0.104 pmol/mg). The binding affinity was found to be slightly higher on day 24 than on day 22 and it remained the same on days 24 and 29. The binding affinity of the receptors was the same in decapitated foetuses as in 29-day-old controls but the number of sites was slightly lower. The labelled steroid was transferred to the nucleus of the liver cells in vivo. It seems unlikely that steroid receptors are the limiting factor preventing the accumulation of glycogen in the liver of the rabbit foetus before day 26 or after decapitation.

Animals↗
PubMed1978

The endocrine pancreas of the fetus from diabetic pregnant rat.

Diabetes was induced in female rats by streptozotocin administration prior to mating. Pregnant rats were divided into "severe diabetics" (blood glucose concentration above 300 mg/100 ml) and "mild diabetics" (blood glucose ranging from 100 to 200 mg/100 ml). When compared to control fetuses, fetuses from severely diabetic mothers showed a slight decrease of body weight on days 20.5 and 21.5. Fetal pancreatic insulin stores and plasma insulin concentrations were decreased at 19.5, 20.5 and 21.5 days. The insulin response to glucose was impaired both in vivo and in vitro. In contrast, fetuses from mildly diabetic females showed no change in body weight. Pancreatic and plasma insulin concentrations were increased at 19.5, 20.5 and 21.5 days. The response of the beta cells of term fetuses of mild diabetics to glucose stimulation was enhanced in vitro. These results are consistent with the hyperglycaemia-hyperinsulinaemia theory with regard to the fetuses from mildly diabetic rats and with an impairment of insulin biosynthesis and release in fetuses from severely diabetic females.

Animals↗
PubMed1977

Simultaneous prevention of blood abnormalities and hereditary congenital amputations in a brachydactylous rabbit stock.

Hematological and histological studies of the rabbit brachydactyly mutant were made to clarify the question of the blood abnormality that had previously been implicated in the teratogenic process leading to congenital amputation. The hemoglobin of fetal and adult br/br rabbits, studied by electrophoresis and cyanmethemoglobin assay, exhibited no differences from that of controls. The br/br fetuses were polycythemic and severely macrocytic. Fetal limb vessels showed thrombosis leading to hemorrhages in the extremities. The hepatic tissue was abnormal, being particularly poor in hematopoietic cells; blood cell macrocytosis was attributed to impaired erthropoiesis. Treatment of pregnant rabbits with folic acid plus vitamin B12 or with folinic acid was able simultaneously to prevent the fetal blood cell macrocytosis and the congenital abnormalities.

Abnormalities, Multiple↗
PubMed1977

Hyperglycemia and glycogen storage in the rabbit fetal liver. Role of age and hormonal status.

A 2-hour glucose infusion to pregnant rabbits resulted in fetal hyperglycemia. The question was studied whether this hyperglycemia would induce an increase in the concentration of glycogen in the fetal liver. The result depended upon the age of the fetus. In 24- or 25-day-old fetuses hyperglycemia did not increase the liver glycogen. On the contrary, on day 26, 27 and 28, the glycogen content in the liver was approximately twice as high as in controls. However, in fetuses which were decapitated on day 24 and studied on day 26, the maternal glucose infusion did not increase the glycogen stores. But in those fetuses decapitated on day 25 hyperglycemia provoked glycogen deposition. The activity of liver glycogen synthetase (active form alpha and total form a + b) increased between days 24 and 28 in control fetuses. Some increase of the alpha form already occurs between days 24 and 25. In fetuses decapitated on day 23, the alpha form was found almost as low on day 31 as it was on day 23. The incapacity of the liver of fetuses under 26 days of age or of those decapitated before day 25 to store glycogen under conditions of hyperglycemia probably results from a low glycogen synthetase activity.

Animals↗