Comptes rendus hebdomadaires des seances de l'Academie des sciences. Serie D: Sciences naturelles最新文献

The study of the growth of Prorocentrum micans E. submitted to sublethal doses of cadmium demonstrated a high sensitivity of this Dinoflagellate to the polluant starting with concentration of 5 microgram/l. The uptake of cadmium was measured by pulse polarographic analysis of the filtered culture medium. Structural modifications, not apparent in living cells, are visible after fixation. The high sensitivity of Prorocentrum micans to cadmium, also its easy culture, makes it a suitable pollution indicator of this heavy metal.

Plasma testosterone levels change with annual sexual cycle of the stone marten. Very low during the decrease and the quiescence of the testis, it rises during the testis onset and reaches a maximal peak during the coït period (May to July).

Using the lymphocyte reaction (MLR) as an in vitro model of allogeneic response we have demonstrated that red blood cells (RBC), when phagocytosed by monocytes present in the reaction, induce almost complete suppression of the MLR. A similar effect is achieved by the RBC lysate or purified hemoglobin. These data strongly suggest that the better graft tolerance apparently induced by blood transfusion given to the recipient at the time of transplantation may result from a non specific immunodepressive process induced by the injected erythrocytes, and mediated by the monocyte.

Two platinum derivatives, cis-PtCl2(NH3)2 and PtCl6(NH4)2 have been studied for their effects on the Rat on cytochrome P450 in hepatic parenchyma on zoxazolamine-hydroxylase, a typical inducible system and on the two isoenzymes of dimethyl-nitrosamine demethylase, typical repressible systems. The inhibitory effect of PtCl6(NH4)2 on zoxazolamine-hydroxylase activity, previously shown by the authors, has been confirmed. The cis-PtCl2(NH3)2 also significantly inhibits zoxazolamine-hydroxylase activity. On the other hand, both of the platinum derivatives decrease cytochrome P450 level and enhance the dimethyl-nitrosamine metabolism. These various effects and their relationship are discussed.

15 days after experimental infection with human adenovirus 5, C57 Bl/6 murine spleen cells were found to have altered in vitro properties. Proliferative response to phytohemagglutinine was slightly increased while the allogeneic response was decreased and the capability to stimulate allogeneic cells was significantly diminished. The degree of expression of surface antigens responsible for allogeneic stimulation is influenced by many regulatory factors, still poorly defined; alteration of some factors of antigenicity may result, directly or indirectly, from certain viral infections.

Double-labeled bile ([U. 3H glycerol] [1. 14C linoleic acid])--in which about 70% of labeling 14C and 80% of labeling 3H of total lipids were borne by phosphatidylcholines (PC), (isotopic ratio of these PC was equal to 1)--was introduced into the duodenum of test Rats, some of them with a bile fistula. As low amounts of the hydrolysis products of biliary PC were found in the intestinal lumen, a higher hydrolysis must occur further (brush border, enterocyte ?) because, in the mucosa, the highest labeling 14C was present as triglycerides and PC have an isotopic ratio 3H/14C higher than 1. As in the lumen the isotopic ratio 3H/14C of PC was higher than 1 and increased with the time elapsed, this finding suggests that mucosal PC were added to biliary PC (secretion or desquamation ?) unless these modifications were due to luminal micro-organisms. As test Rat bile was poorly labeled a very weak enterohepatic circulation of biliary diunsaturated PC may exist.

Scanning electron microscopic observation of plastic casts of human chorionic villi vasculature has demonstrated that in the area of placental exchange two blood capillary networks are present: the paravascular and the villous capillary networks. S.E.M. provides precise information on the shape and anatomical relations of these blood capillary networks.

Important amounts of nicotinic acid appear in the growth medium of neuroblastoma cell cultures. It is shown that an enzyme released by the cells into the growth medium deamidates the nicotinamide supplied by the growth medium to nicotinic acid.

Mice peritoneal macrophages cultured in vitro release a prostaglandin-like activity as evaluated by a bio-assay using Rat stomach fundus. The prostaglandin release is greatly increased when macrophages are incubated with the supernatant of mixed lymphocyte cultures between recipient and donor of a skin allograft. This phenomenon was found in all strains of Mice tested except C3H/HeJ Mice, a strain already known for its defective responsiveness to bacterial lipopolysaccharide (LPS).

Egg lipovitellins of Orchestia gammarella tested by electrophoresis on gels of different acrylamide concentrations, following the procedure of Hedrick and Smith (1968), display a migration pattern identical to that of proteins with molecular weights of congruent to 3.2 x 10(5) (lipovitellin I) and congruent to 5.5 x 10(5) (lipovitellin II) respectively. Since their molecular weight remains constant during embryogenesis, the changes of their relative mobility in disc gels indicates alterations in their ionic charges.