Biomedical subjects

A Jost

Publications and source records attributed to A Jost.

At least 73 records · Page 4Linked to original sources

PubMed1976

[The first manifestations of freemartinism in the calf fetus do not depend on XX/XY chromosomal chimerism].

In order to investigate the eventual role of XX/XY chimerism in freemartinism the vascular anastomoses between twin fetuses were surgically suppressed in litters with several fetuses, before the appearance of the first sexual anomalies. In three female fetuses isolated from their co-twins on days 37 and 45, the initial freemartin effect of gonadal and Müllerian inhibition was absent, in spite of an important XX/XY chimerism in the liver.

Animals↗

PubMed1976

Growth hormone in encephalectomized rat fetuses, with comments on the effects of anesthetics.

Plasma and pituitary immunoreactive growth hormone (GH) was measured in 21.5-day-old rat fetuses under various experimental conditions. Encephalectomy on day 19.5 was used as a method for depriving the fetus of its hypothalamus. The fetuses were recovered on day 21.5 under maternal pentobarbital anesthesia. Total encephalectomy or partial encephalectomy (ablation of superficial brain structures) similarly affected fetal growth. The mean GH contents of the pituitaries were not significantly different in the four groups of fetuses studied: controls from intact females (1.38 +/- 0.19 mug/gland), controls from females submitted to surgery on day 19 (1.47 +/- 0.13 mug/gland), surgically encephalectomized fetuses (1.13 +/- 0.12 mug/gland), sham-operated fetuses (1.19 +/- 0.10 mug/gland). The mean plasma GH levels were the same in control fetuses of intact females (147 +/- 8 ng/ml) and in control fetuses of females submitted to surgery (168 +/- 9 ng/ml). The values were lower in sham-operated fetuses (118 +/- 11 ng/ml) and considerably reduced (P less than 0.001) in encephalectomized fetuses (60 +/- 8 ng/ml). Plasma GH was higher in the fetuses of females killed less than 2 min earlier, than in the fetuses of anesthetized females. In dams anesthetized with pentobarbital or ether, the fetal plasma levels of GH were not different after 15 or 45 min of maternal anesthesia. Under maternal urethane anesthesia, the fetal plasma GH was at 15 min significantly lower than it was under (P less than 0.01) or pentobarbital (P less than 0.05); 30 min later, it had increased by 40% (P less than 0.025). It appears that the release of GH in the fetus can be modified by anesthetics, and that some GH still is released by the pituitary gland in the absence of the hypothalamus.

Anesthetics↗

PubMed1976

Effect of environmental temperature on glucose-induced insulin response in the newborn rat.

Blood glucose and plasma insulin and glucagon concentrations were determined in full-term rats delivered by cesarean section and exposed to 37 degrees C. or 24 degrees C. environmental temperature during the first hours of extrauterine life. When newborn rats were maintained at thermal neutrality (37 degrees C.), a transient period of hypoglycemia of two hours occurred, associated with a rapid fall in plasma insulin and a rise in plasma glucagon concentrations. During cold exposure (24 degrees C.), the blood glucose level remained stable over the four hours studied; the decrease of plasma insulin was sluggish while the rise of plasma glucagon was unchanged. In newborn rats maintained at 37 degrees C., an intraperitoneal glucose load one hour after delivery produced a marked rise in blood glucose and plasma insulin concentrations one hour later. The distribution of experimental points suggested a sigmoidal dose-response curve. By contrast in newborn rats kept at room temperature (24 degrees C.) the same glucose load did not induce any increase in plasma insulin in spite of hyperglycemia. However, phentolamine resulted in pronounced plasma insulin rise in hypothermic newborns in response to glucose administration. From these observations it is concluded that the in-vivo unresponsiveness of the beta cells to glucose at birth, reported by others, is mainly due to the experimental conditions.

Age Factors↗

PubMed1976

[Chronology of development of the genital tract of the calf fetus].

The chronology and the modalities of the differentiation of the genital apparatus were studied in 187 calf fetuses whose insemination age was exactly known (between 32 and 110 days). Male. In the male, the first seminiferous cords form around days 41-42, the interstitial cells appear 2 or 3 days later. From days 60-70 on, the rete testis is made of tubules with an open lumen, which connect the seminiferous cords. The masculinisation of the external genitalia begins as early as day 47 by a rapid increase of the anogenital distance: on day 60, the penis opens under the umbilicus and the scrotum is well differentiated. The regression of the Müllerian ducts starts at the level of their anterior (tubal) part on day 50, when their diameter decreases. From day 58 on, the oviducts become discontinuous and they are almost completely absent by day 63; the uterine horns and the vagina have dissappeared by day 80. The masculinization of the internal genitalia occurs during two phases: 1) between days 56 and 58: the early buds of the seminal vesicles and of the prostate appear, as well as the first differences at the level of the urogenital connections and of the Cowper's glands; a supra-urethral diverticulum develops at the level of the posterior prostatic urethral flexure; the non sexual urethra remains short. 2) After day 70 take place: the differentiation of the epididymides the branching of the seminal vesicles and the stabilization of the Wolffian ducts (after a transitory diminution of their diameter between days 60 and 80). Female. In the female, sexual organogenesis proceeds later than in males. The Müllerian ducts (which show a transitory reduction of their diameter at their tubal level between days 50 and 60) develop steadily after day 60 at the level of their uterine horns and of the vagina; simultaneously the non sexual urethra lengthens rapidly. A suburethral diverticulum, which is absent in the male, develops at the level of the urogenital connections, between days 60-70. The regression of the Wolffian ducts takes place after day 70 when the mesonephros disappear; they first become discontinuous in their median part (at the uterine level) between days 77-80, but important remains of these ducts still persist on day 110, in the posterior part of the vagina. The first primordial ovarian follicles form only after day 100 approximately.

Animals↗

PubMed1975