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.

H2A.Z Is Required for Global Chromatin Integrity and for Recruitment of RNA Polymerase II under Specific Conditions

Abstract: Evolutionarily conserved variant histone H2A.Z has been recently shown to regulate gene transcription in Saccharomyces cerevisiae. Here we show that loss of H2A.Z in this organism negatively affects the induction of GAL genes. Importantly, fusion of the H2A.Z C-terminal region to S phase H2A without its corresponding C-terminal region can mediate the variant histone's specialized function in GAL1-10 gene induction, and it restores the slow-growth phenotype of cells with a deletion of HTZ1. Furthermore, we show that the C-terminal region of H2A.Z can interact with some components of the transcriptional apparatus. In cells lacking H2A.Z, recruitment of RNA polymerase II and TATA-binding protein to the GAL1-10 promoters is significantly diminished under inducing conditions. Unexpectedly, we also find that H2A.Z is required to globally maintain chromatin integrity under GAL gene-inducing conditions. We hypothesize that H2A.Z can positively regulate gene transcription, at least in part, by modulating interactions with RNA polymerase II-associated factors at certain genes under specific cell growth conditions.

Management and Outcomes of a First Recurrence of Clostridium difficile-Associated Disease in Quebec, Canada

Abstract: Background. During an epidemic of Clostridium difficile–associated disease (CDAD) caused by a strain that is a hyper-producer of toxins A and B, the frequency of a first recurrence after metronidazole treatment of the initial episode doubled in 2003–2004, compared with 1991–2002. Methods. To examine whether administration of metronidazole as treatment for a first recurrence of CDAD remained appropriate, we reviewed data for patients with CDAD diagnosed in a hospital in Quebec, Canada, during 1991–2005, who experienced a first recurrence. The frequency of a second recurrence within 60 days after the first one was measured using Kaplan-Meier analysis. Cox regression was used for multivariate analysis. Results. A total of 463 patients had a first recurrence of CDAD, of whom 154 (33.3%) experienced a second recurrence. Independent predictors of a second recurrence were age and duration of hospitalization after the first recurrence; this latter finding suggested that many such episodes were reinfections rather than relapses. Neither choice of treatment drug (metronidazole or vancomycin) nor use of the same drug for treatment of first recurrence, as had been used during the initial episode, was associated with increased risk of a second recurrence. However, 51 patients (11.0%) developed at least 1 complication (i.e., shock, need for colectomy, megacolon, perforation, or death within 30 days) during the first recurrence. Older age, a high leukocyte count, and renal failure at first recurrence were strongly associated with a complicated CDAD. Conclusions. Metronidazole is not inferior to vancomycin for treatment of patients with a first recurrence of CDAD, but the risk of complications with any treatment of CDAD may be higher than has previously been documented.

Morphological study of hydroxyapatite nanocrystal suspension.

Abstract: Nanometer size hydroxyapatite (HA) crystals are prepared by a wet chemical precipitation method at different synthesis temperatures and with various reactant addition rates. The resulting aqueous suspensions are studied in terms of morphology (transmission electron microscope, specific surface area), phase (X-ray diffraction, electron diffraction and infrared spectroscopy) and rheological properties. This work shows that shape, size and specific surface area of the HA nanoparticles are very sensitive to the reaction temperature and also to the reactant addition rate. The measured pH at the end of synthesis, which is strongly linked with the reactant addition rate, is a key parameter which can be used to determine the purity of the synthesized HA nanocrystal and also for the stabilization (dispersion) of the suspension. HA nanoparticles synthesized at low temperature (T < 6°C) are monocrystalline. A transition temperature (T=60 °C) can be defined as a limit for the synthesis of monocrystalline HA nanocrystals, above this critical temperature nanocrystals become polycrystalline. HA monocrystals adopt a needle shape and are oriented following the c-axis of the hexagonal HA structure. The as-synthesized suspension is then concentrated and the effect of a dispersing agent addition, which is needed to get a high solid/liquid ratio coupled with good flowability of the suspension, is also shown, because this suspension is used in the suspension plasma spraying process.

Identifying authoritative actors in question-answering forums: the case of Yahoo! answers

Abstract: We consider the problem of identifying authoritative users in Yahoo! Answers. A common approach is to use link analysis techniques in order to provide a ranked list of users based on their degree of authority. A major problem for such an approach is determining how many users should be chosen as authoritative from a ranked list. To address this problem, we propose a method for automatic identification of authoritative actors. In our approach, we propose to model the authority scores of users as a mixture of gamma distributions. The number of components in the mixture is estimated by the Bayesian Information Criterion (BIC) while the parameters of each component are estimated using the Expectation-Maximization (EM) algorithm. This method allows us to automatically discriminate between authoritative and non-authoritative users. The suitability of our proposal is demonstrated in an empirical study using datasets from Yahoo! Answers.