Response of Lacustrine Biota to Late Holocene Climate and Environmental Conditions in Northernmost Ungava (Canada)

Sediment cores from three lakes located in the northernmost region of Ungava, Québec (Canada) were examined to define aquatic community and ecosystem variability during the Late Holocene period. A chironomid-based transfer function was used to reconstruct August air temperature trends, and lacustrine primary production was inferred from sedimentary biogenic silica content and siliceous microfossil abundances. Trends in primary production, sediment organic matter content (estimated through loss on ignition), and chironomid-inferred temperature were compared to explore potential effects of environmental change on biotic assemblage composition at centennial to millennial time scales. Although no direct correlation between chironomid-inferred August air temperature and primary production was observed, we found indications that both chironomid and diatom communities were responding to the same overarching regional climatic and environmental processes. Over the last decade, northern Québec has been undergoing notable, rapid warming that contrasts with the relative inertia of the past few millennia. This study provides a baseline against which recent and future environmental changes in this region can be compared. Les archives sédimentaires couvrant la période de l’Holocène tardif ont été examinées dans trois lacs situés dans la région du nord de l’Ungava, au Québec (Canada). Un modèle d’inférence basé sur les assemblages de chironomides a été utilisé pour reconstruire la variabilité des températures de l’air du mois d’août, et la production primaire lacustre a été inférée par le contenu sédimentaire en silice biogénique et les abondances des microfossiles siliceux. Les variations historiques de la production primaire, du contenu organique du sédiment (évalué par la perte au feu) et les températures inférées ont été comparées afin d’explorer les effets potentiels des changements environnementaux sur la composition des assemblages à différentes échelles temporelles (centenaires à millénaires). Malgré le fait qu’aucune corrélation directe n’ait été observée entre les températures inférées en août et la productivité primaire, certaines indications suggèrent que les communautés de chironomides et de diatomées répondaient aux mêmes processus climatiques et environnementaux régionaux. Au cours de la dernière décennie, le nord du Québec a connu un réchauffement rapide et marqué, contrastant avec l’inertie relative des derniers millénaires. Cette étude fournit le scénario de référence par rapport auquel les changements environnementaux actuels et futurs pourront être comparés dans cette région

Biodiversity patterns of Arctic diatom assemblages in lakes and streams : Current reference conditions and historical context for biomonitoring

1. Comprehensive assessments of contemporary diatom distributions across the Arctic remain scarce. Furthermore, studies tracking species compositional differences across space and time, as well as diatom responses to climate warming, are mainly limited to paleolimnological studies due to a lack of routine monitoring in lakes and streams across vast areas of the Arctic. 2. The study aims to provide a spatial assessment of contemporary species distributions across the circum-Arctic, establish contemporary biodiversity patterns of diatom assemblages to use as reference conditions for future biomonitoring assessments, and determine pre-industrial baseline conditions to provide historical context for modern diatom distributions. 3. Diatom assemblages were assessed using information from ongoing regulatory monitoring programmes, individual research projects, and from surface sediment layers obtained from lake cores. Pre-industrial baseline conditions as well as the nature, direction and magnitude of changes in diatom assemblages over the past c.200 years were determined by comparing surface sediment samples (i.e. containing modern assemblages) with a sediment interval deposited prior to the onset of significant anthropogenic activities (i.e. containing pre-1850 assemblages), together with an examination of diatoms preserved in contiguous samples from dated sediment cores. 4. We identified several biotypes with distinct diatom assemblages using contemporary diatom data from both lakes and streams, including a biotype typical for High Arctic regions. Differences in diatom assemblage composition across circum-Arctic regions were gradual rather than abrupt. Species richness was lowest in High Arctic regions compared to Low Arctic and sub-Arctic regions, and higher in lakes than in streams. Dominant diatom taxa were not endemic to the Arctic. Species richness in both lakes and streams reached maximum values between 60°N and 75°N but was highly variable, probably reflecting differences in local and regional environmental factors and possibly sampling effort. 5. We found clear taxon-specific differences between contemporary and pre-industrial samples that were often specific to both ecozone and lake depth. Regional patterns of species turnover (β-diversity) in the past c.200 years revealed that regions of the Canadian High Arctic and the Hudson Bay Lowlands to the south showed most compositional change, whereas the easternmost regions of the Canadian Arctic changed least. As shown in previous Arctic diatom studies, global warming has already affected these remote high latitude ecosystems. 6. Our results provide reference conditions for future environmental monitoring programmes in the Arctic. Furthermore, diatom taxa identification and harmonisation require improvement, starting with circum-Arctic intercalibrations. Despite the challenges posed by the remoteness of the Arctic, our study shows the need for routine monitoring programmes that have a wide geographical coverage for both streams and lakes

The Disulfide Bonds in Glycoprotein E2 of Hepatitis C Virus Reveal the Tertiary Organization of the Molecule

Hepatitis C virus (HCV), a major cause of chronic liver disease in humans, is the focus of intense research efforts worldwide. Yet structural data on the viral envelope glycoproteins E1 and E2 are scarce, in spite of their essential role in the viral life cycle. To obtain more information, we developed an efficient production system of recombinant E2 ectodomain (E2e), truncated immediately upstream its trans-membrane (TM) region, using Drosophila melanogaster cells. This system yields a majority of monomeric protein, which can be readily separated chromatographically from contaminating disulfide-linked aggregates. The isolated monomeric E2e reacts with a number of conformation-sensitive monoclonal antibodies, binds the soluble CD81 large external loop and efficiently inhibits infection of Huh7.5 cells by infectious HCV particles (HCVcc) in a dose-dependent manner, suggesting that it adopts a native conformation. These properties of E2e led us to experimentally determine the connectivity of its 9 disulfide bonds, which are strictly conserved across HCV genotypes. Furthermore, circular dichroism combined with infrared spectroscopy analyses revealed the secondary structure contents of E2e, indicating in particular about 28% β-sheet, in agreement with the consensus secondary structure predictions. The disulfide connectivity pattern, together with data on the CD81 binding site and reported E2 deletion mutants, enabled the threading of the E2e polypeptide chain onto the structural template of class II fusion proteins of related flavi- and alphaviruses. The resulting model of the tertiary organization of E2 gives key information on the antigenicity determinants of the virus, maps the receptor binding site to the interface of domains I and III, and provides insight into the nature of a putative fusogenic conformational change

Trace metal remobilization following the resuspension of Saguenay Fjord sediments

The Saguenay Fjord sediments are characterized by high trace metal, organic matter and iron monosulphide (AVS) concentrations. The presence of important maritime activities, as well as dredging operations and natural slumpling events, contribute to the resuspension of the Fjord sediments and changes in their redox conditions.The objective of this research was to determine the impact of sediment resuspension on the remobilization of trace metals (e.g. Hg, Cu, Ni, Pb, As, Fe and Mn). in the water column. Once dissolved in the water column, the trace metals are subjected to a suite of geochemical processes, while remaining available for the uptake by the biota, until they find their way out of the fjord or back into the sediments. The results of the resuspension experiments conducted in the laboratory reflect the reactivity of these anoxic sediments as well as the trace metal desorption and readsorption kinetics. By monitoring the behaviour of different metals we were able to differentiate between the reactivity of those metals which are preferentially associated with the sulphides and organic matter. (Abstract shortened by UMI.

Activité paraoxonase 1 sérique (marqueur des accidents vasculaires cérébraux ischémiques)

LIMOGES-BU Médecine pharmacie (870852108) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

La prescription médicamenteuse chez la personne âgée, poly-pathologique, en perte d'autonomie et hébergée en institution (étude EVAL-EHPAD en Limousin)

LIMOGES-BU Médecine pharmacie (870852108) / SudocLYON1-BU Santé (693882101) / SudocSudocFranceF

Les discours des institutions pénales à l’épreuve du numérique : entre extension de la conflictualité et déformalisation du discours

International audienc

Le discours institutionnel de la force publique sur les réseaux sociaux numériques

Entretien avec Charlotte Pasco, community manager de la police nationale, réalisé par Isabelle Huré et Guillaume Le Saulnier Introduction Dans le cadre de la coordination du dossier de Semen sur les discours des institutions pénales à l’épreuve du numérique, nous avons interviewé Charlotte Pasco, community manager de la police nationale. La communication mass- médiatique et numérique est une préoccupation croissante pour la force publique, au sens où elle s’institutionnalise et se professionn..

La communication de la police nationale sur les réseaux sociaux numériques : de la quête de likes aux techniques de gouvernementalité

International audienc

Le discours institutionnel de la force publique sur les réseaux sociaux numériques

National audienc