Reproduction, nutrition, developpement最新文献

Membrane preparations were obtained by differential centrifugations of ewe mammary gland homogenates. These membrane preparations contained specific receptors for IGF1 and IGF2 which possess high affinities for their specific ligands (Ka .5 to 1.5 10(9) M-1). Maximum binding of 125I IGF1 was obtained after 48 h at 4 degrees C. This binding was inhibited by unlabelled IGF1 (ED50 = 14 ng/ml), partially inhibited by high concentrations of insulin (50 micrograms/ml). Prolactin (oPRL), growth hormone (bGH) or relaxin (Rel) were without effect. Maximum binding of 125I IGF2 was obtained after 6 h at 20 degrees C. This binding was inhibited by unlabelled IGF2 (ED50 = 44 ng/ml), partially inhibited by IGF1 (ED50 = 200 ng/ml) and unmodified by INS, PRL, bGH or Rel. Receptor numbers for IGF1 were significantly higher (p less than 0.01) on day 100 of pregnancy (N = 480 +/- 17 fmoles/mg proteins) compared to day 20 of lactation (N = 174 +/- 21 fmoles/mg). The numbers of IGF2 receptors were always higher than those of IGF1 receptors. During pregnancy the numbers of IGF2 receptors (N = 1,860 +/- 157 fmoles/mg) were also higher than during lactation. These results suggest that the mammary gland may constitute a target organ for IGFs. These factors could be involved in the regulation of mammary gland development and during cell differentiation.

Rabbit zonae pellucidae were isolated using a modified technique of Dunbar et al. (1980). Zonae pellucidae were solubilized in saline phosphate buffer (pH 7.8) for 30 min at 70 degrees C. One dimensional SDS-PAGE analysis showed that zona pellucida is essentially composed of three major proteins with apparent molecular weights of 200 (275-165) kd, 100 (135-96) kd and 75 (96-51) kd. Preincubation of sperm with heat-solubilized zonae pellucidae (SZP) (5 to 8 SZP/microliters) did not reduce sperm binding ability. By contrast, it significantly decreased the percentage of penetrated eggs (20 versus 73% for the control) and significantly reduced the fertilization rate (10 versus 55% for the control). Ultrastructural analysis of several oocytes in the two groups demonstrated that inhibition of fertilization was not due to the inhibition of sperm-zona binding ability but essentially resulted from the impairment of sperm penetration through the zona pellucida.

Large follicles were obtained from sheep ovaries during the follicular phase, dissected and incubated for 24 h in a perifusion system. Continuous flow of B2 medium gassed with O2 and CO2 and supplemented with FSH/LH pulses every other hour enabled us to measure the steroid secretion rates of each follicle. At the end of the perifusion, the follicles were processed for histological examination. It was demonstrated that 70% of the follicles were healthy after 24 h of perifusion. This was associated with a high secretion rate of oestradiol compared to atretic follicles. In contrast testosterone and progesterone secretion rates were similar in healthy and atretic follicles. In both healthy and atretic follicles, repeated gonadotrophin pulses produced increases in steroid production. Such a perifusion system might be a valuable tool to study between and within-follicle interactions to get new insights in paracrine and autocrine regulations in the ovary.

Thyroid hormones were measured in plasma of genetically lean (LL) or fat (FL) chickens at different ages. No differences were observed at hatching or at adult age. More triiodothyronine (T3) and less thyroxine (T4) were found in the plasma of LL than in FL at the fed state during the growth period. This difference disappeared as the birds approached sexual maturity. Dietary supplementation by T3 increased the plasma concentration of T3 at the fed state. It did not influence growth rate, feed efficiency and body temperature. T3 supplementation tended to decrease abdominal fat proportion. It is suggested that the difference in plasma T3 would account for only a small proportion of the between-genotype differences in fattening.

Vitellogenin was obtained from three year-old vitellogenic trout. Two procedures of isolation were compared: dialysis against distilled water and ultracentrifugation in the density interval 1.21-1.28 g/ml. Similar patterns were observed by gel filtration and electrophoresis for both preparations of vitellogenin, indicating that electric charge and molecular weight were not modified by either procedure. The apparent Mr of the native form was 560,000 in gel filtration, whereas that of the monomer was estimated as 170,000 by sodium dodecylsulfate-polyacrylamide gel electrophoresis. Minor proteins were also detected (100,000-88,000-78,000). The main components were protein (79%), and lipids (19%), Carbohydrates accounted for 0.3% when protein phosphorus and calcium each represented 0.7% of total weight. Phospholipids (70% of total lipids) mainly consisted of phosphatidylcholine in which n-3 docosahexanenoic acid accounted for one-third of total fatty acids. The results show the high levels of essential fatty acids in structural lipids which are known to be involved in embryo development.

An in vitro system has been developed which induces full meiotic maturation in 98% ovarian sheep oocytes isolated from follicles 2-6 mm in diameter. 45.7% of these were fertilized, determined by the presence of two pronuclei, extrusion of the second polar body and the presence of the sperm flagellum. This culture system was used to describe the morphological changes during meiotic maturation, examining the nucleus, the cytoplasm and cumulus (corona)-oocyte relationship. 24 h are required for maturation of sheep oocytes. The culture medium must contain FSH, LH (10 micrograms/ml of each), estradiol-17 beta (1 micrograms/ml) and coculture of 10(6) mural granulosa cells in suspension (Crozet et al., 1987). Nuclear changes were the first evident transformations, showing that chromatin condensation leads to nuclear deformation, to germinal vesicle breakdown and to formation of the first and second meiotic metaphases. The axis of both spindles are oriented perpendicularly to the egg membrane. At each pole a bent disc composed of filamentous material represents the microtubule organizing centers (MTOC). The key event may be the initiation and control of chromosome condensation. Cytoplasmic changes include the development of a cortical layer of 1-4 microns thickness poor in cell organelles. Golgi complexes are localized in three distinct areas with possibly different functions: (1) around the germinal vesicle; (2) in the oocyte cortex, of regular distance; (3) in the central part of the oocyte. Cortical granules (CG) of different maturation stages (condensation) form clusters near the peripheral Golgi complexes while at Meta I they form a nearly continuous single layer. At Meta II the CGs are apparently anchored to the cell membrane by means of small spokes. The cumulus (corona) cells are attached by junctional complexes to each other and to the oocyte. Foot processes cross the zona and indent the oocyte. The termini are gradually exteriorized and contacts must be broken to isolate the oocyte. The sum of all the above changes represent meiotic maturation.

Two-compartment time-independent model (2C) and one-compartment time-dependent model (1C) of degree 2 for concentrates and 3 for forages provided estimates of total mean retention time (MRT) in the digestive tract which were similar to direct calculations but more variable. Model 1C was found superior in fitting the data.

The epididymis is the target of different infections that interfere first with the physiological capacity of the organ and furthermore with the transit of spermatozoa. Epididymal blocks do interfere with testicular function in about 20% of the cases. According to the pathological agents epididymal blocks will be located either in the initial segments of the epididymis (tuberculosis) or in the lower segments of the organ (gonococcus) or they can interfere with the total structure (chlamydia). Epididymal blocks can be either complete or incomplete and the transit difficulties create lesions of the tubules due to progressive rupture and secondary fibrosis.

In cases of congenital absence of vas deferens (9 patients) or after failure of previous epididymovasostomy (2 patients), in vitro fertilization (IVF) was attempted with spermatozoa surgically obtained at the epididymal caput level. These sperm populations showed little progressive motility (5.9 +/- 6.5%) and an marked necrozoospermia (19.3 +/- 17.4%). Stimulation by caffeine (4.5 mM) alone or associated with heterologue normal seminal fluid resulted in most of the cases in an initiation of motility with an improvement of the progressive velocity. In 9 IVF attempts, 31 mature oocytes were inseminated with 5.10(3) to 1.5.10(6) motile spermatozoa. The dynamic characteristics in 3 inseminated sperm populations were Vp (24.2 +/- 8.3 microns/s), Ah (8.6 +/- 2.0 microns) at room temperature. Sperm binding to zona pellucida was decreased (0 to about 20 spermatozoa per oocyte) and there was no fertilization. In the same period, 21 attempts of intra uterine insemination and 14 attempts of intracervical inseminations were made in 5 couples who remained infertile after patent high epididymovasostomy (4) or vasovasostomy (1) and having immature spermatozoa stimulated as previously described. Antisperm antibodies were detected on the ejaculated spermatozoa in four men. No pregnancy was obtained with these immature stimulated spermatozoa. The fertility of the female partners was confirmed in 3 women after insemination with donor sperm.

Plasma concentrations of cortisol and glucagon have been measured in preruminant lambs after feeding a meal containing either 2.3 or 10.6 g leucine/100 g dry matter and were found similar. These two hormones are probably not involved in the effects induced by dietary leucine excess.