Biomedical subjects

Stéphane Dupas

Publications and source records attributed to Stéphane Dupas.

4 recordsLinked to original sources

PubMed2006

Genome ecosystem and transposable elements species.

Transposable elements are known to be "selfish DNA" sequences able to spread and be maintained in all genomes analyzed so far. Their evolution depends on the interaction they have with the other components of the genome, including genes and other transposable elements. These relationships are complex and have often been compared to those of species living and competing in an ecosystem. The aim of this current work is a proposition to fill the conceptual gap existing between genome biology and ecology, assuming that genomic components, such as transposable elements families, can be compared to species interacting in an ecosystem. Using this framework, some of the main models defined in the population genetics of transposable elements can then been reformulated, and some new kinds of realistic relationships, such as symbiosis between different genomic components, can then be modelled and explored.

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PubMed2006

Brief report: graduated compression stocking thromboprophylaxis for elderly inpatients: a propensity analysis.

BACKGROUND: Graduated compression stockings (GCS) are often used for deep vein thrombosis prophylaxis in nonsurgical patients, although evidence on their effectiveness is lacking in this setting. OBJECTIVE: To determine whether prophylaxis with GCS is associated with a decrease in the rate of deep vein thrombosis in nonsurgical elderly patients. METHODS: Using original data from 2 multicenter nonrandomized studies, we performed multivariable and propensity score analyses to determine whether prophylaxis with GCS reduced the rate of deep vein thrombosis among 1,310 postacute care patients 65 years or older. The primary outcome was proximal deep vein thrombosis detected by routine compression ultrasonography performed by registered vascular physicians. RESULTS: Proximal deep vein thrombosis was found in 5.7% (21/371) of the GCS users and in 5.2% (49/939) of the GCS nonusers (odds ratio [OR], 1.09; 95% confidence interval [CI], 0.64-1.84). Although adjusting for propensity score eliminated all differences in baseline characteristics between users and nonusers, the OR for proximal deep vein thrombosis associated with GCS remained nonsignificant in propensity-stratified (adjusted OR, 1.11; 95% CI, 0.59-2.10) and propensity-matched (conditional OR, 0.92; 95% CI, 0.42-2.02) analysis. Similar figures were observed for distal and any deep vein thrombosis. The rates of deep vein thrombosis did not differ according to the length of stockings. CONCLUSIONS: Prophylaxis with GCS is not associated with a lower rate of deep vein thrombosis in nonsurgical elderly patients in routine practice. Randomized studies are needed to assess the efficacy of GCS when properly used in this setting.

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PubMed2004

Evolution of hemocyte concentration in the melanogaster subgroup species.

We explore two possible hypotheses about the ecological factors driving the evolution of hemocyte load in insects. The first is parasite infection risk, its variability and the genetic diversity of parasites. The other supposes that all the other factors of environmental stress drive the evolution through a pleiotropic selection on metabolic rate. The two hypotheses are tested with data on hemocyte load and ecology of six Drosophila species of the melanogaster subgroup. Hemocyte load correlates significantly with the parasite-driven selection index, but not with the stress selection index. The result being based on too little data to conclude definitely, this work must be considered more as a methodological research based on published results on insect physiology immunity and ecology rather than an empirical evidence of such a relationship.

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PubMed2003

Diversifying selection in a parasitoid's symbiotic virus among genes involved in inhibiting host immunity.

During parasitization of their hosts some insect parasitoids deliver resident viruses which encode genes that must be expressed in the host for successful parasitization. Among these viruses the Campoletis sonorensis Ichnovirus has been well studied and encodes a cys-motif gene family implicated in disruption of host immunity and other physiological systems. Members of this gene family encode one or more intercystine-knot structural motifs in which the non-cysteine residues of the motif are variable. We analyzed patterns of synonymous and non-synonymous substitution within the cys-motif to investigate the evolution of this gene family and the likelihood of virus-host gene coevolution. Maximum likelihood techniques suggest positive selection acts on 8 of 51 codons in the aligned cysteine-rich region. Although the detected positive selection was not strong, it likely contributes to the diversification of this gene family. Comparison of selection pressure relative to tertiary structure of the VHv1.1 cys-motif protein suggests that the hypervariable sites are exposed. Furthermore, invariant residues in the motif exhibit a region-specific pattern of codon bias, suggesting there are unusual mechanisms of effecting selection pressure at work in this system, though the mechanism has yet to be studied. The positive selection and duplication of both the gene family and the cys-motif implies either selection is driving the molecular radiation of immune suppressive genes toward novel hosts, or molecular coevolution with host targets.

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