Comptes rendus des seances de l'Academie des sciences. Serie III, Sciences de la vie最新文献

In vivo studies indicate that FSH can modulate Leydig cells steroidogenic activity. However, in the testis only Sertoli cells contain specific FSH receptors. In order to clarify the mechanism by which FSH exerts this effect on testicular steroidogenesis, purified Pig Leydig and Sertoli cells were cultured alone or in co-culture. Leydig cell activity has been evaluated by two parameters: 1. hCG-stimulated testosterone secretion. 2. LH/hCG binding sites. FSH does not stimulate these two parameters of purified Leydig cells when cultured alone. On the other hand, when Leydig cells are co-cultured with Sertoli cells, FSH significantly increases these two parameters of Leydig cell function. These results suggest that the effect of FSH on Leydig cells is not direct but mediated by Sertoli cells.

Plasma testosterone binding activity was determined by an equilibrium dialysis method in the male of Lacerta vivipara during the annual cycle of activity (from March to September). Capacity showed significant variations during the sexual cycle although affinity remained constant. The variations of capacity were then compared with plasma testosterone levels measured by radioimmunoassay and plasma proteins content measured by the Lowry method. The three parameters showed parallel seasonal evolution except in May-June when binding activity increased although plasma testosterone and protein levels fell. The physiological meaning of this conspicuous phenomenon is discussed=an active mechanism of strengthening of the atrophy of accessory sexual organs is hypothesized. Furthermore, the increase of the binding activity which occurs in autumn and is parallel to the levels of testosterone must prevent these accessory organs from a full resumption of activity before the retreat since the lizard is a hibernating animal. These results emphasize the key role played by specific plasma binding proteins in the modulation of steroid hormone action.

Free and peptidic amino acids were measured in the seminal plasma of carp. Some acids such as glutamic acid and glutamine, taurine, glycine and proline were exceptionally abundant, while others like lysine, arginine and histidine were found in small amounts. Generally, the amino acid level was higher in carp seminal plasma than in that of other Vertebrate species. As this level was systematically higher than in the blood plasma, it is supposed that there was neoformation of an original fluid in the genital tract.

Specific high affinity binding sites for thyrotropin-releasing hormone (TRH) were demonstrated on cellular membranes from human prolactin-secreting adenomas in spite of the lack of in vivo prolactin response to TRH. One binding site was characterized. The mean value for the Kd from four adenomas was 64.8 +/- 12.5 nM. The maximal number of binding sites varied from one adenoma to another (from 80 to 450 fmoles/mg membrane proteins).

We demonstrate that the interactions between the uterine cytosol proteins of 24 day old Rats and estradiol-17 beta (E2) are significantly influenced by physiological concentrations of non esterified fatty acids (2. 10(-4)M). We show that the specific binding of the hormone to the 8S uterine receptor, is markedly inhibited (50-80%) by the unsaturated fatty acids. The observed inhibition is a function both of acid dose and acid unsaturation degree. The polyunsaturated arachidonic and docosahexaenoic acids are the strongest inhibitors, whereas the saturated palmitic and stearic acids do not displace the E2 from the 8S receptor.

Electrical and mechanical activities of frog skeletal muscle fibres were simultaneously investigated under conditions which allow the development of a strontium permeability. It was shown that the contraction elicited by a long lasting Sr response depends upon two mechanisms: a potential dependent one, and a mechanism which is related to the entry of Sr ions into the cell through the tubular membrane.

Human red cells lysis produced by adriamycin in vitro was investigated both in phosphate medium pH7 and in human serum. Drug induced hemolysis, that appeared with concentrations markedly above plasmatic levels seen in therapeutic, was stongly enhanced by serum. It is the first relations of modulation through a human serum factor of a biological action of adriamycin.

Pregnant Mice were stimulated with two substances, an antibronchitic lysate (LAB) and diethyldithiocarbamate (DTC). PFC response was studied in mothers and their offspring for 6 weeks after birth. An increase in PFC response was noted in the immunostimulated adult Mice. In the newborn Mice, the number of PFC increased between the 1st and 6th week. In comparison with controls, PFC response appeared later in the newborns to LAB-stimulated mothers and earlier in those to DTC-stimulated mothers.

Using a specially designed push-pull cannula stereotaxically implanted into the 3rd ventricle, a pulsatile secretion of IR-SRIF with a circhoral periodicity was detected in male rats. At 30 min. to 1 h 1/2 intervals the secretion rate of the neuropeptide rose from a baseline rate of 14.5 +/- 0.5 pg/10 min., corresponding to a baseline concentration of 60 +/- 2 pg/ml to peaks of 50 +/- 5 pg/10 min. or 210 +/- 22 pg/ml, respectively. This pulsatile pattern was restricted to rats where histological examination showed no dilation pictures of the ventricle. The possible origin and function of intra-ventricular IR-SRIF are discussed.