Université de Sherbrooke

About: Université de Sherbrooke is a education organization based out in Sherbrooke, Quebec, Canada. It is known for research contribution in the topics: Population & Receptor. The organization has 14922 authors who have published 28783 publications receiving 792511 citations. The organization is also known as: Universite de Sherbrooke & Sherbrooke University.

Life History Consequences of Variation in Age of Primiparity in Bighorn Ewes

Abstract: We investigated the life history consequences of age at primiparity in two marked populations of bighorn sheep (Ovis canadensis), studied for 19 and 12 yr. Some ewes first lambed at 2 yr of age, others at 3 or 4 yr. Lambs of 2-yr-old ewes were smaller and less viable than lambs of older ewes. Lactation at 2 yr did not affect survival to 3 yr, but in one population it was associated with reduced survival from 3 to 4 yr. Two yr olds that weaned lambs gained less mass during summer than other 2 yr olds. Overwinter mass loss from 2 to 3 yr was correlated with autumn body mass, and was lower for parous than for nonporous ewes. Reproductive success at 3 yr was independent of reproductive status at 2 yr. At 4 yr, ewes that lactated as 2 yr olds were smaller than ewes that had not lactated as 2 yr olds. In one population, negative effects of early maturation upon mass gain and subsequent reproductive success became evident at high density, and very few 2 yr olds lambed when population density was high. The lifetime reproductive success of early- maturing ewes was not lower than that of late-maturing ewes. To account for individual variation in initial reproductive potential, we controlled body mass as a yearling, a variable that affected reproductive success. Mass as a yearling, however, did not interact with age of primiparity to affect survival, growth, or reproductive success. Uncertainties about re- source availability and possible effects of genotype and body fat may explain why many ewes postponed their first reproduction despite apparently low life history costs of early maturation.

Electrokinetic Properties which Control the Coagulation of Silicate Cement Suspensions during Early Age Hydration

Abstract: The coagulation of cement particles during early age hydration has been previously identified as the first step of the setting and hardening of cement pastes. By hydrating Ca3SiO5and a silicate-rich clinker under controlled conditions, a correlation between the coagulation of the suspensions and the electrokinetic properties of particles is established. The zeta potential, and hence the surface charge, of particles in suspension depends on the calcium content of the medium. At low concentrations of Ca2+, the zeta potential of Ca3SiO5particles, calcium silicate hydrate (C–S–H), and clinker is negative (<−30 mV) and the suspensions are well dispersed. A strong coagulation occurs at intermediate concentrations (1 to 10 mmol/L of Ca2+) as the zeta potential becomes weaker under these conditions. The mean diameter of the aggregates decreases at high Ca2+concentrations, where the zeta potential of the particles is high and positive.

Altered D-chiro-inositol urinary clearance in women with polycystic ovary syndrome.

Abstract: OBJECTIVE —Evidence suggests that some actions of insulin are effected by inositolphosphoglycan (IPG) mediators. We hypothesize that a deficiency in D- chiro -inositol (DCI) and/or a DCI-containing IPG (DCI-IPG) may contribute to insulin resistance in humans. RESEARCH DESIGN AND METHODS —To assess this possibility in polycystic ovary syndrome (PCOS), we determined insulin sensitivity ( S i by frequently sampled intravenous glucose tolerance test), plasma and urinary DCI and myo -inositol (MYO) levels (by gas chromatography/mass spectrometry), and the release of insulin and DCI-IPG during the oral glucose tolerance test (area under the curve [AUC]) in 23 women with PCOS and 26 normal women. RESULTS —Women with PCOS were heavier than control subjects ( P = 0.002 for BMI), but also had decreased S i ( P insulin ( P DCI ) was increased almost sixfold in PCOS compared with normal women ( P = 0.001), but not MYO clearance ( P = 0.10). uCl DCI correlated inversely with S i when all women were analyzed together ( n = 49, r = −0.50, P S i . Finally, the ratio of AUC DCI-IPG to AUC insulin was decreased threefold in women with PCOS ( P CONCLUSIONS —uCl DCI is inversely correlated with insulin sensitivity in women and is a strong independent predictor of insulin resistance in multivariate models. PCOS, which is characterized by insulin resistance, is associated with a selective increase in uCl DCI and impaired DCI-IPG release in response to insulin. These findings are consistent with a defect in tissue availability or utilization of DCI in PCOS that may contribute to the insulin resistance of the syndrome.