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Biomedical subjects

Philippe Chouteau

Publications and source records attributed to Philippe Chouteau.

6 recordsLinked to original sources
PubMed2006

The nonstructural 5A protein of hepatitis C virus genotype 1b does not contain an interferon sensitivity-determining region.

BACKGROUND: The nonstructural (NS) 5A protein of hepatitis C virus (HCV) has been suggested to contain an interferon (IFN) sensitivity-determining region (ISDR). METHODS: We studied whether the degree of viral decline on day 1 is associated with differences in NS5A amino acid sequences among patients receiving IFN- alpha. RESULTS: Phylogenetic analyses of the full-length protein and of functional domains showed no relationship between the baseline protein sequence and the antiviral response. NS5A quasispecies sequences showed no differences in the number of mutations in the putative ISDR relative to a prototype sequence between responders and nonresponders or according to IFN- alpha antiviral efficacy. No relationship was found between antiviral efficacy at 24 h and the baseline sequence of any NS5A region. Amino acid changes were observed in a few cases at 24 h in both responders and nonresponders, but no consistent pattern of amino acid shifts was observed, ruling out the possibility that IFN- alpha selected IFN-resistant variants. CONCLUSION: Our findings show that there is no ISDR in the HCV genotype 1 NS5A protein and that the NS5A sequence does not influence the capacity of IFN- alpha to block viral replication. The findings do not rule out a role for NS5A in subsequent viral clearance.

Adult↗
PubMed2006

Influences of the season and the habitat structure on the foraging ecology of two coua species in the western dry forest of Madagascar.

I studied the foraging ecology of Coquerel's Coua (Coua coquereli) and Giant Coua (Coua gigas), which occur in the dry forest in west Madagascar. This kind of forest is characterised by an alternating of a dry and a rainy season. The foraging behaviour was described in several dimensions: i.e. height and proportion of perching, rate of capture (estimating the food availability), foraging techniques, substrates used, type and size of the captured prey. Their foraging behaviour was different according to the season and to the proximity of water. Habitat structure was important to take in consideration to study their foraging behaviour. They tended to use the same pattern of techniques and substrates, but differed by the proportions they used these variables and also by the possibility to climb into the dense understorey vegetation. Seasonal variation has probably an important effect on the prey availability and the nature of prey captured. The diet of both species is also discussed. I suggest that change in habitat structure and resources levels could be important to take in consideration for the conservation of these forest birds.

Animals↗
PubMed2005

Hepatitis C virus-induced hepatocellular steatosis.

Two distinct forms of hepatocellular steatosis can be seen in patients with chronic hepatitis C virus (HCV) infection. Classical metabolic risk factors for hepatocellular steatosis account for the vast majority of cases of steatosis in patients infected by non-genotype 3 HCV strains. In contrast, in patients infected by HCV genotype 3, steatosis is generally induced by the virus itself through a direct cytopathic effect, the mechanisms of which remain debated. Mixed forms of steatosis can also be seen in HCV genotype 3-infected patients with metabolic risk factors. Hepatocellular steatosis appears to be associated with more rapid progression of hepatic fibrosis. However, it is unclear whether this association is due to steatosis itself, or rather to metabolic and host factors that promote steatosis and fibrosis concomitantly. This review discusses current knowledge of HCV-induced steatosis and its relation to chronic HCV-associated liver disease.

Fatty Liver↗
PubMed2004

Habitat selection and density of couas in Madagascar: implication for their conservation.

The forests in Madagascar are threatened by logging and burning. Because of their importance for biodiversity conservation, monitoring their animal populations is also important. We worked at two stations in the western dry forest where we studied three species of terrestrial couas in several forest plots, which differed in their degradation state. Some were burnt; others were logged. By measuring vegetation characteristics and bird densities, it was possible to indicate which characteristics were important for these birds and which conservation measures would be necessary to apply for this forest.

Conservation of Natural Resources↗
PubMed2004

The impacts of logging on the microhabitats used by two species of couas in the western forest of Madagascar.

Habitat structure is important to consider in all ecological studies considering the relationships between animals and their environment. Habitat structure can be studied at different scales, from landscape to microhabitat. I studied here the response of two endemic terrestrial birds living in the dry forest of Madagascar. These birds belong to the genus Coua. The study is made at the microhabitat scale in a gallery forest, which has been logged selectively in order to limit the degradation of the forest. Selective logging is promoted to be respectful of the environment by allowing us to exploit the forest without destroying it and the wildlife encountered here. At the microhabitat scale, I underline that selective logging does not affect the Coquerel's coua, which can exploit new microhabitats and increase its density. On the other hand, the giant coua was affected by the restriction of optimal microhabitats for foraging. This species could be adapted to the new habitat by modifying its favourite foraging sites, but by decreasing also the population density. This species was affected by forest degradation, even considered as not destroying. At last, I considered how Coquerel's coua could be used as umbrella species for the endangered mesite.

Animals↗