InP and GaAs characterization with variable stoichiometry obtained by molecular spray

Both InP and GaAs surfaces were studied in parallel. A molecular spray technique was used to obtain two semiconductor surfaces with different superficial compositions. The structures of these surfaces were examined by electron diffraction. Electron energy loss was measured spectroscopically in order to determine surface electrical characteristics. The results are used to support conclusions relative to the role of surface composition in establishing a Schottky barrier effect in semiconductor devices

Reduced Cortisol and Metabolic Responses of Thin Ewes to an Acute Cold Challenge in Mid-Pregnancy: Implications for Animal Physiology and Welfare

Background: Low food availability leading to reductions in Body Condition Score (BCS; 0 indicates emaciation and 5 obesity) in sheep often coincides with low temperatures associated with the onset of winter in New Zealand. The ability to adapt to reductions in environmental temperature may be impaired in animals with low BCS, in particular during pregnancy when metabolic demand is higher. Here we assess whether BCS affects a pregnant animal’s ability to cope with cold challenges. Methods: Eighteen pregnant ewes with a BCS of 2.760.1 were fed to attain low (LBC: BCS2.360.1), medium (MBC: BCS3.260.2) or high BCS (HBC: BCS3.660.2). Shorn ewes were exposed to a 6-h acute cold challenge in a climate-controlled room (wet and windy conditions, 4.460.1uC) in mid-pregnancy. Blood samples were collected during the BCS change phase, acute cold challenge and recovery phase. Results: During the BCS change phase, plasma glucose and leptin concentrations declined while free fatty acids (FFA) increased in LBC compared to MBC (P,0.01, P,0.01 and P,0.05, respectively) and HBC ewes (P,0.05, P,0.01 and P,0.01, respectively). During the cold challenge, plasma cortisol concentrations were lower in LBC than MBC (P,0.05) and HBC ewes (P,0.05), and FFA and insulin concentrations were lower in LBC than HBC ewes (P,0.05 and P,0.001, respectively). Leptin concentrations declined in MBC and HBC ewes while remaining unchanged in LBC ewes (P,0.01). Glucose concentrations and internal body temperature (Tcore) increased in all treatments, although peak Tcore tended to be higher in HBC ewes (P,0.1). During the recovery phase, T4 concentrations were lower in LBC ewes (P,0.05). Conclusion: Even though all ewes were able to increase Tcore and mobilize glucose, low BCS animals had considerably reduced cortisol and metabolic responses to a cold challenge in mid-pregnancy, suggesting that their ability to adapt to cold challenges through some of the expected pathways was reduced

Photoperiod and nutritional status modulate the expression of the gene encoding leptin in ovine perirenal adipose tissue

"Chantier qualité spécifique "Auteurs Externes" département de Génétique animale : uniquement liaison auteur au référentiel HR-Access "International audienc

Glucose-6-phosphate dehydrogenase and leptin are related to marbling differences among Limousin and Angus or Japanese Black x Angus steers

This work investigated the metabolic basis for the variability of carcass and i.m. adiposity in cattle. Our hypothesis was that the comparison of extreme breeds for adiposity might allow for the identification of some metabolic pathways determinant for carcass and i.m. adiposity. Thus, 23- to 28-mo-old steers of 3 breeds, 2 with high [Angus or Japanese Black x Angus (J. Black cross)] and 1 with low (Limousin) i.m. and carcass adiposity, were used to measure activities or mRNA levels, or both, of enzymes involved in de novo lipogenesis [acetyl-coA carboxylase, fatty acid synthase (FAS), glucose-6-phosphate dehydrogenase (G6PDH), malic enzyme], circulating triacylglycerol (TAG) uptake (lipoprotein lipase), and fatty acid esterification (glycerol-3-phosphate dehydrogenase), as well as the mRNA level of leptin, an adiposity-related factor. In a first study, enzyme activities were assayed in the s.c. adipose tissue (AT), the oxidative rectus abdominis, and the glycolytic semitendinosus muscles from steers finished for 6 mo. Compared with Angus or J. Black cross, Limousin steers had a 27% less (P = 0.003) rib fat thickness, and 23 and 29% less (P ≤ 0.02) FAS and G6PDH activities in s.c. AT. In rectus abdominis and semitendinosus, the 75% less (P < 0.001) TAG content was concomitant with 50% less (P < 0.001) G6PDH activity. In a second study, enzyme activities plus mRNA levels were assayed in an oxido-glycolytic muscle, the longissimus thoracis (LT), in the i.m. AT dissected from LT, and in s.c. AT from the same Limousin steers and from Angus steers finished for 10 mo. Compared with Angus, the 50% less (P < 0.001) rib fat thickness in Limousin contrasted with the 1.1- to 5.8-fold greater (P ≤ 0.02) mRNA levels or activities, or both, of acetyl-coA carboxylase, G6PDH, lipoprotein lipase, and glycerol-3-phosphate dehydrogenase in s.c. AT. Conversely, the 90% less (P < 0.001) TAG content in Limousin LT was concomitant to the 79 and 83% less (P ≤ 0.002) G6PDH activity and leptin mRNA level. Such differences could arise from a greater number of adipocytes in LT from Angus steers because no difference was found between Limousin and Angus for G6PDH activity and leptin mRNA in i.m. AT. We conclude that FAS and G6PDH in s.c. AT could be involved in differences in carcass adiposity, but this relationship disappeared when the fatness increased strongly. Leptin and G6PDH are related to the expression of marbling whatever the body condition and thus could be relevant indicators of marbling in beef cattle

Lipogenesis in subcutaneous adipose tissue and in oxidative or glycolytic muscles from Angus, Black Japanese × Angus and Limousin steers

The impacts of the breed and/or anatomical sites on enzyme activities linked to de novo lipogenesis and esterification were investigated. Samples of subcutaneous adipose tissue (SCAT), rectus abdominis (RA) and semitendinosus (ST) muscles were obtained from Limousin, Angus and Black Japanese × Angus steers to assay fatty acid synthase (FAS), glucose-6-phosphate dehydrogenase (G6PDH), malic enzyme (ME) and glycerol-3-phosphate dehydrogenase (G3PDH) activities. FAS (P=0.03) and G6PDH (P=0.02) activities expressed per mg of soluble protein were lower in SCAT, RA and ST from Limousin than from Angus and Black Japanese × Angus. Whatever the breed, FAS, ME, G6PDH activities were higher (P<0.0001), and G3PDH activity was lower (P<0.0001), in SCAT than in muscles. G3PDH activity was lower (P<0.05) in the oxidative RA than in the glycolytic ST. Significant interaction between breed and anatomical sites were observed for FAS (P=0.01), G6PDH (P=0.004) and G3PDH (P<0.0001) which indicated that (i): breed effect on FAS and G6PDH activities was only significant in SCAT, (ii): anatomical site differences for G3PDH activities were dependent on the breed, the decreasing rank order was SCAT<RA<ST in Angus and Black Japanese x Angus, and SCAT<RA<ST in Limousin steers

Study of lipoprotein lipase mRNAs in ovine adipose tissue by quantitative fluorescence polymerase chain reaction

International audienc

Glucose-6-Phosphate dehydrogenase and leptin are linked to marbling differences between Limousin and angus or japanese black x angus steers

International audienc