Reproduction, nutrition, developpement最新文献

The peripheral blood and milk contain two steroids, whose concentrations can be monitored and used as a tool for pregnancy diagnosis in cattle: (1) Progesterone of maternal origin, which must be assayed between days 21-24 after Al, allows very early diagnosis of non pregnancy or of gestation onset, (2) Oestrone sulfate secreted by the feto-placental unit is a good means for confirming pregnancy over 110 days after Al. Both steroids have been assayed in a very high number of samples by RIA in so-called centralized diagnosis laboratories. These have many advantages and usually are of a very high standard. Accuracy of these diagnoses has been evaluated in a large number of experimental series and is well known (93-100% for early non pregnancy diagnosis). EIA kits for progesterone have been on the market for 2-3 years. But a more simple test to be used by the farmer himself is now available. It is a so-called dipstick test (Bovitest - ND - Clonatec), including control and test pads on the stick itself plus the conjugate and a soluble substrate. Reading and interpretation ar made by single observation according to the intensity of the blue colour on the test pad compared to that on the control. There is a good agreement between the results of the RIA procedure (used as a reference) and those of this dipstick test. A field study on a quite large basis was undertaken to evaluate the accuracy of the diagnosis made according to this on the farm test. It was very similar to that found by RIA.(ABSTRACT TRUNCATED AT 250 WORDS)

In domestic mammals, the optimum time for embryo transfer greatly depends upon the species and its embryo chronology development and the technique used. Three different models (rabbit, pig, bovine) have been studied to set up the importance of cycle synchrony between donor and recipient. In the rabbit, the best survival rates were obtained after tubal transfer to highly synchronous recipients even for frozen or cultured embryos. In the pig, there was no survival difference after embryo transfer on D2 (oviduct) or D6 (uterus) and an asynchrony up to 24 h was possible. In the bovine, embryo transfer is usually performed at the blastocyst stage directly into the uterus. A retrospective study over 2,000 recipients indicates that the highest pregnancy rates were obtained when the recipient was in heat 12 to 24 h before the donor.

The immunology of pregnancy involves a series of systemic and above all local events, at the feto-maternal interface. These immunological events may explain the paradoxical non-rejection and development of the allogeneic conceptus within of the maternal body. The immunodeviation of the maternal immune system towards fetal tolerance may be altered or insufficient leading to true abortive diseases. The alteration of this tolerance may be the result of auto-immune abnormalities, particularly when autoantibodies are discovered in woman's serum. These antibodies are the antithromboplastin, antiphospholipid and antinuclear antibodies. They can be responsible for abortion even if the clinical symptoms of the lupus disease are absent. Abortive events occur at all stages of pregnancy. Table 1 shows that abortions with autoantibodies are more frequent when the accident occurs in the late stage of pregnancy. The therapy with corticoids and aspirin will be modulated in connection with the results. The second immune etiology is an insufficient production of immunological events usually involved in normal pregnancies. The current means available to detect this incompetency are imperfect because only systemic factors may be explored when local events are the most involved. We found a good correlation, in these women with recurrent early abortions of unknown etiology, between the production of anti-husband lymphocytes (AAP) and the success of a subsequent pregnancy. Women who suffer from recurrent spontaneous abortions of unknown etiology, without autoimmune abnormalities and without antipaternal antibodies (AAP), may profit from a therapy using the husband's leucocyte injections, which allows them to give birth to a normal child in 85% of the cases, whereas without treatment the success rate is only 37% of the pregnancies. When this therapy is applied in accurate conditions, its inocuousness seems well established. Another kind of this immunomodulator therapy has been reported: it uses unrelated donor leucocytes. Its efficiency seems to be similar to that of the husband's leucocyte injections.

Young crossbred lambs and Suffolk rams were exposed to photoperiods stimulatory to growth or reproduction respectively. Whereas long days are known to facilitate rate of gain, feed efficiency and carcass yield in young market lambs, exposure to decreasing daylengths or short days is necessary for successful reproduction of the species. Successful substitution of a "skeleton" long photoperiod (7L:9D:1L:7D) for long photoperiod (16L:8D) exposure to growing lambs to improve performance provides strong support for the conclusion that long-day stimulation is not the result of the interval of day being illuminated but rather the time interval between two periods within a day which is illuminated. The same "skeleton" long photoperiod (7L:9D:1:7D) is shown to substitute effectively for a long (16L:8D) photoperiod when used alternately with a short (8L:16D) photoperiod in eight-week light cycle exposure of mature Suffolk rams. Light cycles of this duration entrain LH, testosterone and testicular weight and stimulate reproductive activity to a level comparable to that observed in rams during the normal breeding season. Evidence is presented that the relatively short eight-week light cycles prevent photorefractoriness from occurring and thereby can maintain indefinitely the behavioral and gametogenic activities required of the breeding ram. Implementation of short days combined with alternating "skeleton" long days should be energy efficient and may prove useful for application to sire management.

In this review, the results obtained in commercial livestock with certain beta-adrenergic agonists (clenbuterol and cimaterol) having an anabolic potential associated with lipid mobilizing properties are considered. The first chapter summarizes major data concerning the effects of beta-agonists on growth and carcass composition in cattle, sheep and pigs. The effect of clenbuterol and cimaterol on carcass quality is to increase the deposition of protein while reducing fat accretion. Then, we briefly consider the physiology and pharmacology of the sympathoadrenal system with a special attention to the distribution and properties of beta-adrenoceptors of various tissues which are putative targets for the beta-adrenergic agonists. Several mechanisms liable to be responsible for the anabolic action of these compounds are also discussed. This chapter includes the evaluation of the effects of beta-agonist on central nervous system and pancreas. A special attention is devoted to their metabolic impact on adipose tissue and muscle. In isolated fat cells, beta-agonists promote stimulation of lipolysis associated with reduction of lipogenesis and of insulin action. The in vitro effects on adipocytes are consistent with the in vivo effects of the compounds. Beta-agonist impact on protein synthesis and muscle accretion is also discussed with reference: 1) to the vascular effects of the compounds that should modify the nutrient flow into the muscle, 2) to a reduction of proteolysis mainly observed for the moment in in vitro studies, 3) to the possible beta-adrenergic-dependent enhancement of insulin action on the muscle. However, more direct experimental evidence is still needed to clearly assess the nature of the action(s) of such anabolic agents on muscle.

The pineal gland is known to play a central role in the photoperiodic control of reproduction in seasonal breeders. The present review, based on experimental data obtained in four different species of hamster, the Syrian or golden, the Djungarian or Siberian, the Turkish and the European, attempts to evaluate the role of the pineal in this phenomenon, the message which is conveyed from this gland as well as the mechanism of action of this message. Melatonin one of the 5-methoxyindoles rhythmically synthesized in the pineal gland, appears to be the pineal hormone conveying the photoperiodic message. The importance of the duration of the nocturnal peak of circulating melatonin is now well established, but our knowledge on the sites of action and on the mechanisms of action of melatonin is still rather poor. The presently available data suggest that melatonin can act at different levels, either on specific receptors, on receptors of other transmitters, on various molecular processes after diffusion in the cell or indirectly via effects on other endocrine hormones, e.g. gonadal steroids.

The experiments which have provided insight into the role of the pineal gland and melatonin in sheep reproduction are reviewed. There is now strong evidence that timed daily melatonin administration and continuous administration via implants are equally effective in promoting the same physiological consequences as short daylength. Thus melatonin treatments lasting six weeks can result in an advance of the breeding season and an advance in the seasonal peak in ovulation rate. Much longer periods of exposure to melatonin or long-term pinealectomy result in a different response. In the second part of this review the long-term effects of pineal manipulation in juvenile and pubertal ewes are compared and contrasted. Five years after pinealectomy (at 7.5 months) ewes displayed normal timed breeding seasons without exhibiting a normal annual pattern of LH sensitivity to oestradiol. Pinealectomy at 2.5 months of age resulted in delayed puberty and breeding seasons out of synchrony with normal ewes two years later. These animals maintained an LH sensitivity to oestradiol consistent with their own breeding season. Melatonin implants which delivered melatonin for over a year caused similar effects as pinealectomy at 2.5 months but had essentially opposite effects to pinealectomy in adults. These results generate many questions about the different perception of the melatonin signal in prepubertal versus adult ewes and the factors involved in the onset and offset of the breeding season.

A morphometric study of the principal epithelial cells of the epididymis has been carried out in six young adult men. Samples were taken in the head, body and tail of the epididymis and processed for ultrastructural study. The cytoplasm was subdivided into four zones. Their section areas were measured by planimetry and the volume density of cytoplasmic organelles assessed using the point-counting method. The general organization of the principal cells of the epididymis was identical along the duct. Quantitative analysis revealed that cells of the head contained significantly larger amounts of coated-vesicles and of Golgi saccules than the body and the tail. The functional implications of these results is important for the understanding of receptor-mediated endocytosis and protein synthesis in the different parts of the human epididymal duct.

The detachment of adherent bacteria from feed particles in the abomasum of sheep was assessed by in sacco and in vitro trials using 15N labelled bacteria. This detachment was similar amongst the feed residues tested (40.5%). However, bacteria were found to stick stronger on small (less than 250 microns) than on large particles.

The nylon bag technique, standardized for studies in the rumen, was extended to the abomasum, small and large intestines. This simple and physiological method provided valuable information on the nitrogen digestion of several feeds.