688 research outputs found
Nouvelle approche des migrations scientifiques internationales
International audienc
Characterization of a naphthalene dioxygenase endowed with an exceptionally broad substrate specificity toward polycyclic aromatic hydrocarbons
International audienceIn Sphingomonas CHY-1, a single ring-hydroxylating dioxygenase is responsible for the initial attack of a range of polycyclic aromatic hydrocarbons (PAHs) composed of up to five rings. The components of this enzyme were separately purified and characterized. The oxygenase component (ht-PhnI) was shown to contain one Rieske-type [2Fe-2S] cluster and one mononuclear Fe center per alpha subunit, based on EPR measurements and iron assay. Steady-state kinetic measurements revealed that the enzyme had a relatively low apparent Michaelis constant for naphthalene (Km= 0.92 ± 0.15 ”M), and an apparent specificity constant of 2.0 ± 0.3 ”M-1 s-1. Naphthalene was converted to the corresponding 1,2-dihydrodiol with stoichiometric oxidation of NADH. On the other hand, the oxidation of eight other PAHs occurred at slower rates, and with coupling efficiencies that decreased with the enzyme reaction rate. Uncoupling was associated with hydrogen peroxide formation, which is potentially deleterious to cells and might inhibit PAH degradation. In single turnover reactions, ht-PhnI alone catalyzed PAH hydroxylation at a faster rate in the presence of organic solvent, suggesting that the transfer of substrate to the active site is a limiting factor. The four-ring PAHs chrysene and benz[a]anthracene were subjected to a double ring-dihydroxylation, giving rise to the formation of a significant proportion of bis-cis-dihydrodiols. In addition, the dihydroxylation of benz[a]anthracene yielded three dihydrodiols, the enzyme showing a preference for carbons in positions 1,2 and 10,11. This is the first characterization of a dioxygenase able to dihydroxylate PAHs made up of four and five rings
Split Spectrum Modifié pour la détection d'échos ultrasonores multiples
Cette communication présente une variante de l'algorithme Split Spectrum Processing (SSP) adaptée pour la détection d'échos ultrasonores spéculaires dans un milieu biologique. Nous montrons en particulier comment augmenter la résolution de la méthode par la réduction des interférences dans le plan temps-fréquence du SSP. Ce plan est obtenu par découpage spectral avec un banc de filtres Gaussiens (équivalent à une transformée de Gabor)
Synthesis of branched-phosphodiester and mannosecentered fucosylated glycoclusters and their binding studies with Burkholderia ambifaria lectin (BambL)
Universite Montpellier 2, Region RhoËne-Alpes Cluster Chimie. A.A.International audienceFive fucosylated glycoclusters exhibiting 4, 6 or 8 residues were synthesised with two different spatial environments based on mannose-centered and branched-phosphodiester scaffolds. Their synthesis was performed in solution using phosphoramidite chemistry to generate phosphodiester linkages, combined with Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC). The multivalent ligands were evaluated for their ability to bind to Burkholderia ambifaria Lectin (BambL). Binding evaluation was performed through inhibition of hemagglutination (HIA), surface plasmon resonance (SPR) and isothermal titration microcalorimetry (ITC). All fucosylated glycoclusters exhibited a higher affinity to BambL than methyl α-L-fucoside. A dissociation constant of 43 nM was observed for the fucocluster exhibiting four residues with the branched-phosphodiester spatial environment corresponding to a 22-fold increase in comparison with methyl α-L-fucoside. These multivalent fucoclusters represent the first example of ligands of high affinity to BambL
Staphylococcus aureus seroproteomes discriminate ruminant isolates causing mild or severe mastitis
Staphylococcus aureus is a major cause of mastitis in ruminants. In ewe mastitis, symptoms range from subclinical to gangrenous mastitis. S. aureus factors or host-factors contributing to the different outcomes are not completely elucidated. In this study, experimental mastitis was induced on primiparous ewes using two S. aureus strains, isolated from gangrenous (strain O11) or subclinical (strain O46) mastitis. Strains induced drastically distinct clinical symptoms when tested in ewe and mice experimental mastitis. Notably, they reproduced mild (O46) or severe (O11) mastitis in ewes. Ewe sera were used to identify staphylococcal immunoreactive proteins commonly or differentially produced during infections of variable severity and to define core and accessory seroproteomes. Such SERological Proteome Analysis (SERPA) allowed the identification of 89 immunoreactive proteins, of which only 52 (58.4%) were previously identified as immunogenic proteins in other staphylococcal infections. Among the 89 proteins identified, 74 appear to constitute the core seroproteome. Among the 15 remaining proteins defining the accessory seroproteome, 12 were specific for strain O11, 3 were specific for O46. Distribution of one protein specific for each mastitis severity was investigated in ten other strains isolated from subclinical or clinical mastitis. We report here for the first time the identification of staphylococcal immunogenic proteins common or specific to S. aureus strains responsible for mild or severe mastitis. These findings open avenues in S. aureus mastitis studies as some of these proteins, expressed in vivo, are likely to account for the success of S. aureus as a pathogen of the ruminant mammary gland
Value and monitoring of biodiversity on Moorea Island, French Polynesia: a methodological approach of terrestrial and marine ecosystems
The island of Moorea in French Polynesia is representative
of a relatively well preserved small tropical oceanic island but both its terrestrial and marine ecosystems
are currently under strong anthropogenic pressures. The terrestrial ecosystems are facing an increasing urbanization,
and the destruction and modification of their natural habitats by cultivation and forestry plantations,
accidental or intentional fires, and particularly by the invasion of alien plant and animal species. Coastal areas
and reef ecosystems are threatened by shoreline artificialization, sedimentation due to soil erosion, increasing
uses of marine and lagoon resources and frequency of coral bleaching events. A significant erosion of terrestrial
and marine biodiversity is observed on the island since the last decades. In the context of the Land Management
Plan (PGA) and Marine Area Management Plan (PGEM) recently set up in the island by local authorities,
scientific surveys and inventories were made in 2006 in order to assess the status of terrestrial biodiversity (vascular
plants) and marine biodiversity (reef fishes) and compare areas with different anthropogenic pressures.
Studies conducted on the flora and the vegetation at low and middle elevation along altitudinal transects show
that the plant invasion process is related to climatic and topographic factors, and species autoecology. The
marine study aims to compare the protected areas with control areas in order to test the effectiveness of protection
measures and to propose a streamlined monitoring protocol. A methodological study in both terrestrial
and marine ecosystems was conducted in order to propose biodiversity indicators which are crucial for decision
making in conservation and sustainable development of island biodiversity. We used Geographic Information
System (GIS) as a fast and intuitive tool for mapping indicators and their variability. This methodological
approach developed on the island of Moorea could be used as a model for other tropical islandsMoorea est une petite ßle océanique tropicale de la Polynésie française relativement bien préservée,
mais dont les Ă©cosystĂšmes terrestres et marins sont actuellement soumis Ă de fortes pressions anthropiques.
Le milieu terrestre est confronté à une urbanisation croissante, à la destruction ou à la modification des habitats
naturels pour lâextension des cultures ou des plantations forestiĂšres, aux incendies volontaires ou accidentels, et
particuliĂšrement Ă lâinvasion dâespĂšces vĂ©gĂ©tales et animales introduites. Les zones cĂŽtiĂšres et les rĂ©cifs coralliens sont menacĂ©s par de multiples perturbations telles que lâartificialisation des lignes de rivage, lâapport de sĂ©diments
dus Ă lâĂ©rosion des sols, lâaugmentation des usages des ressources marines et lagonaires et de la frĂ©quence des
phĂ©nomĂšnes de blanchissement du corail. Une Ă©rosion sensible de la biodiversitĂ© terrestre et marine de lâĂźle est
observĂ©e depuis les derniĂšres dĂ©cennies. Dans le cadre du Plan GĂ©nĂ©ral dâAmĂ©nagement (PGA) et du Plan de
Gestion de lâEspace Maritime (PGEM) mis en place par les autoritĂ©s locales, des inventaires scientifiques ont Ă©tĂ©
rĂ©alisĂ©s en 2006 dans le but dâĂ©valuer lâĂ©tat de la biodiversitĂ© terrestre (plantes vasculaires) et marine (poissons
récifaux) et de comparer des zones soumises à différentes perturbations. Les études réalisées sur la flore et la végétation
de basse et moyenne altitude le long de transects altitudinaux montrent des processus dâinvasion vĂ©gĂ©tale
différents en relation avec les facteurs climatiques, topographiques et autoécologiques des espÚces. Les études
en milieu marin visent Ă comparer des aires protĂ©gĂ©es Ă des aires tĂ©moins afin de suivre lâefficacitĂ© des mesures
de gestion. La rĂ©flexion mĂ©thodologique menĂ©e parallĂšlement sur les deux Ă©cosystĂšmes a pour but dâillustrer
différents indices de biodiversité nécessaires à la prise de décision en matiÚre de conservation ou de développement
durable de la biodiversitĂ© insulaire et de rĂ©aliser un Ă©tat de rĂ©fĂ©rence pour Ă©tablir un diagnostic sur lâĂ©tat de
la biodiversitĂ©. La reprĂ©sentation cartographique des indices Ă lâaide dâun SIG, illustrĂ©e dans cette Ă©tude avec la
richesse spécifique terrestre et marine, permet une lecture intuitive et rapide de la variabilité de cet indice dont la
restitution est basĂ©e sur une standardisation du nombre dâespĂšces. Cette approche mĂ©thodologique dĂ©veloppĂ©e sur
lâĂźle de Moorea pourrait servir de modĂšle pour dâautres Ăźles tropicale
Endemic Human Monkeypox, Democratic Republic of Congo, 2001â2004
By analyzing vesicle fluids and crusted scabs from 136 persons with suspected monkeypox, we identified 51 cases of monkeypox by PCR, sequenced the hemagglutinin gene, and confirmed 94% of cases by virus culture. PCR demonstrated chickenpox in 61 patients. Coinfection with both viruses was found in 1 additional patient
Using Remote Sensing to Map the Risk of Human Monkeypox Virus in the Congo Basin
Although the incidence of human monkeypox has greatly increased in Central Africa over the last decade, resources for surveillance remain extremely limited. We conducted a geospatial analysis using existing data to better inform future surveillance efforts. Using active surveillance data collected between 2005 and 2007, we identified locations in Sankuru district, Democratic Republic of Congo (DRC) where there have been one or more cases of human monkeypox. To assess what taxa constitute the main reservoirs of monkeypox, we tested whether human cases were associated with (i) rope squirrels (Funisciurus sp.), which were implicated in monkeypox outbreaks elsewhere in the DRC in the 1980s, or (ii) terrestrial rodents in the genera Cricetomys and Graphiurus, which are believed to be monkeypox reservoirs in West Africa. Results suggest that the best predictors of human monkeypox cases are proximity to dense forests and associated habitat preferred by rope squirrels. The risk of contracting monkeypox is significantly greater near sites predicted to be habitable for squirrels (ORÂ =Â 1.32; 95% CI 1.08â1.63). We recommend that semi-deciduous rainforests with oil-palm, the rope squirrelâs main food source, be prioritized for monitoring
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