Reproduction, nutrition, developpement最新文献

Two experiments were carried out to study the biliary acids in the rabbit gallbladder. The first studied the effect of diet: commercial rabbit feed, 70% lucerne diet, 70% beet pulp diet. The second experiment studied biliary acids in two groups of young rabbits sacrificed at 28 and 33 days of age, respectively. The concentrations of cholic and glycocholic acids were shown to vary significantly with diet. The composition of the bile of young rabbits differed from that of adults.

Ketogenesis was measured in isolated liver cells from fed or 48 h starved rabbits given either a low fat diet (3%) or a high fat diet (18%). In the fed rabbits, ketogenesis with butyrate, octanoate and oleate was greatly enhanced by the high fat diet. In the starved animals the increase in ketogenesis was moderate and only observed with oleate and butyrate. Results are discussed in relation to in vivo observations.

Mitogenic activity of culture media having contained either unfertilized or cleaved embryos have been studied. In these media human eggs have been cultured for one day, beginning 20 hours following in vitro insemination. B-lymphocyte proliferation was estimated by thymidine incorporation following 3 day culture in the presence of eggs or embryo culture media. No reproducible effect on B lymphocyte proliferation was observed. Therefore the viability of embryos could not be ascertained by the mitogenic activity of their culture media.

HCG levels have been studied in 76 patients following laparoscopic treatment using laparotomy. This shows that early detection of treatment failure is possible of ectopic pregnancy. The decrease of HCG was the same as after conservative treatment from the third or fifth post-operative day onwards. The authors report a scheme for the post-operative follow-up after laparoscopic treatment of ectopic pregnancy based on the rate of HCG decrease.

The pineal gland is essential for the perception of photoperiod change in many species. Information about photoperiod length is conveyed through pineal secretion of the methoxyindole melatonin. Melatonin, suitably administered in physiological quantities is equipotent with artificial photoperiod in the induction of photoperiodic responses. Most experimental work suggests that it is the duration of high night time melatonin secretion (positively correlated with the length of the natural or artificial dark phase) which conveys the photoperiodic signal. Continuous release implants induce short day effects in ewes, entirely comparable to daily feeding of melatonin or short photoperiod. A minimum duration of secretion rather than a specific duration is therefore probably critical to short day effects. There appears to be a seasonal variation in sensitivity to short day melatonin effects (induction of early oestrus) which can be shifted to an earlier time of year following one oestrus advance the previous year. Short duration melatonin is read as a long day even secreted with 22 hour periodicity, suggesting a lack of circadian variation in sensitivity to melatonin.

Recent experiments using nuclear transfer between mouse embryos shows that the parental genomes are not equivalent: both of them must be present at least in a part of the blastomeres to allow full term development of the embryo. The paternal genome is preferentially involved in the development of trophoectodermic cells and appears to be eliminated from the primitive ectoderm when kept alone in androgenetic cells aggregated with normal ones. Differences of expression between parental genomes affect not only the X chromosome, but also several autosomes as evidenced by genetic analysis using meiotic non-disjunction. The nature of the imprinting mechanism that leads to the modification of parental homologous chromosomes is unknown. From experiments involving a particular strain of mice called DDK it appears that the egg cytoplasm may exert a specific action not only on the male pronucleus at the one-cell stage, but also on the paternal contribution of the diploid nucleus of the embryo at the 2-cell stage; a paternal developmental effect on the cytoplasm of one-cell stage embryo can also be demonstrated. These results show that nucleocytoplasmic interactions regulate early paternal gene expression differently from the maternal one.

Using superfused rat pituitary cells we showed that the growth hormone-releasing factor (GRF) and prostaglandin E2 (PGE2) increased growth hormone (GH) secretion in a similar manner in terms of kinetics and amplitude of responses. Moreover, our data suggest that they stimulate GH secretion mainly by cAMP-dependent mechanisms.

The use of Cr-EDTA for estimation of intra-diurnal variations of the reticulo-ruminal fill was studied using six sheep fed ad lib. grass hay twice a day. The results are compared with those obtained by manual emptying of the reticulo-rumen.

The present study is based on the comparison between the radioautographic analysis of the fate of the androgen-binding protein purified from rat testes (HPLC) subsequently iodinated and injected into the epididymal lumen using a micromanipulator, and the biochemical analysis of the binding capacities of this molecule to soluble epididymal membrane extracts using HPLC and ultracentrifugation. The various experimental conditions used here allowed to demonstrate that ABP was internalized by the epididymal epithelium and to state that this internalization was not a non specific fluid phase endocytosis but a receptor-mediated-mechanism. Indeed, from a morphological stand point, the labeled ABP was associated rather with the membranes of the endocytic apparatus than with its content. In addition, from the two lumenal cell types able to resorb seminal fluid products, only the principal cells took up the labeled ABP. Our results clearly showed that this internalization was correlated with the presence of a 125I.ABP binding protein. Since the binding of this protein molecule to ABP was saturable and Calcium and pH dependent, it is strongly suggested that this molecule behaves as a receptor, the ligand (or one of the ligands) of which could be ABP.