Reproduction, nutrition, developpement最新文献

Mean duodenal flow of bacterial DM (5130 +/- 358 g/d) represented 60% of total duodenal DM flow in dairy cows fed hay and concentrate (50/50). Contribution of solid-adherent bacteria (SAB) to the total bacteria entering the small intestine amounted to 71%. It must be taken into account in the estimation of the duodenal flow of bacterial compounds.

To explain the retention of large particles in the reticulum, in vitro sedimentation, sorting of particles by gas production and flow of contents through a hole simulating the reticulo-omasal orifice (ROO) were examined. Removal of large particles from the floor of the reticulum by gas production and a sieving mechanism through the ROO are discussed.

Contractions of the fluid-filled RR dependent upon the activity of the myenteric plexus were observed within 2 weeks after vagotomy in sheep maintained on a liquid diet. Spontaneous but not adrenergic evoked rumination was recorded beyond the 5th week after vagotomy. The observation of ruminating-like activity during 120 to 200 min per day in chronically-vagotomized sheep indicates that the onset of rumination does not require a gastric afferent pathway.

Rape-oil was continuously infused (1.1 kg/d) during at least 3 weeks in 9 cows after the second month of lactation. Oil-free dry matter intake was decreased (-2.6 kg/d) as well as milk protein content (-2.7 g/l). A loss of empty body weight occurred during oil infusion. Preprandial blood glucose tended to decrease, whereas 3-OH-butyrate and non-esterified fatty acids (NEFA) tended to increase. Post-prandial NEFA, and NEFA after isoproterenol injection, were increased, as well as mammary apparent extraction of blood triglycerides.

Urea, compared with deuterium oxide (D2O) as a reference, was used as a body marker to estimate body water volume in ten 2-month old nursing foals. Plasma urea clearance was regular over 10 h and the R2 of the disappearance curve was between 0.93 and 0.98. Mean urea space was about 4% lower than D2O space, but the standard deviation of the proportion of water in body weight was higher with urea (3.8%) than with D2O (1.6%). Calculated urea entry rate was 49 mg/h/kg LW0.75.

In preruminant calves total splanchnic production of immunoreactive somatostatin and gastrin did not change when casein was replaced by whey protein in the diet, but gastrin secretion was more rapid for the first 3 postprandial hours. Loss during passage through the liver was equivalent to splanchnic production for somatostatin, but was very low for gastrin.

Chick muscle cells differentiating in vitro in the absence of nerve cells produce asymmetric forms of acetylcholinesterase (AChE) only if they originate from muscles which accumulate these forms in ovo (i.e. after embryonic day 5). The presence of nerve cells does not induce the synthesis of A forms in cultures of 5 day-old myoblasts and does not increase their proportion in cultures of 7 day-old myoblasts. Thus, the capacity to synthesize (or assemble) the complex polymeric forms of AChE does not reflect a direct neural influence but might rather be considered as an intrinsic property of the "late" categories of myoblasts that sequentially occur during the differentiation of leg muscles. We studied the synthesis of ChE molecular forms in the mouse muscle C2 cell line. From these experiments we suggest that the synthesis of A forms (or their assembly) can take place as soon as the cells are withdrawn from the cell cycle, but does not require cell fusion by itself. These observations are related to other recent studies that challenge the validity of A forms as topographical/physiological markers of neuromuscular interactions.

Scanning Electron Microscope (SEM) was used to examine villous structures at different parts in the small intestines of 22-week-old chickens. Duodenum revealed plate-like villi with large number of goblet cells on the duodenal epithelium. Jejunum and ileum both revealed leaf-like villi, but the amount of goblet cells was greater in the jejunum. A putative effect of villous structures on the intestinal digestion and absorption is discussed.

This study concerns the immunoreactive somatomedin C secretion by prepubertal rabbit epiphyseal chondrocytes cultured in a defined serum-free medium. In such culture conditions, chondrocytes mainly synthesized Type II collagen (80% of total collagen) during 10 days. A small amount of Type I collagen was also found with a significant (p less than 0.05) higher level during the period of cell multiplication (6.4 +/- 1.5%) than when cells reached confluency (0.9 +/- 0.2%). During the 10 days of culture without serum and without hormone added, a Sm-C/IGF1 activity was measured by RIA at a mean level of 30 +/- 5 mU/ml/10 micrograms DNA. This value was significantly higher (p less than 0.001) than in the medium not incubated with the cells (1.7 +/- 0.9 mU/ml). When hGH was added to the culture medium during the period of cell division, the level of Sm-C/IGF1 activity was significantly elevated at 39 +/- 4 mU/ml/10 micrograms DNA (p less than 0.05) and at 55 +/- 3 mU/ml/10 micrograms DNA (p less than 0.001) with 50 ng/ml and 100 ng/ml hGH concentrations respectively. On the contrary, no difference was observed at confluency in treated and non treated cells.

The effects in vitro of monensin on the secretory pathway of caseins in lactating rabbit mammary gland fragments were investigated. Addition of monensin (0.1 microM or 1 microM) to the incubation medium induced a dilatation of Golgi saccules and vesicles and a decrease of the relative volume of microvesicles. Dilated vesicles did not contain acid phosphatase. Neosynthesized proteins were localized by electron microscope autoradiography near the membranes of dilated vesicles. 1 microM monensin did not inhibit basal secretion of neosynthesized caseins (radioactive caseins, labelled during a 3 min pulse, released into the medium), but increased basal secretion of total beta-caseins (measured by radioimmunoassay). Monensin abolished all the effects of prolactin (increase in the relative volume of Golgi microvesicles and stimulation of secretion of total and neosynthesized caseins). These results show that monensin provokes simultaneously modifications in the Golgi apparatus morphology and inhibition of the prolactin stimulating effect. Moreover, secretion of intracellular caseins is differently modified, depending probably on whether caseins are neosynthesized or stored.