Modélisation dynamique de systèmes génétiques de régulation. II. L'induction de l'opéron lactose d'Escherichia coli : étude qualitative et numérique du modèle

International audienc

Modélisation dynamique de systèmes génétiques de régulation I. L'induction de l'operon lactose d'Escherichia coli: élaboration d'un modèle

International audienc

Minimum Antibiotic Levels for Selecting a Resistance Plasmid in a Gnotobiotic Animal Model

The minimum antibiotic concentrations for selecting an R plasmid in vivo were determined in germfree rates colonized by two isogenic strains of Escherichia coli, one of which carried an R plasmid. Seventy groups of three gnotobiotic mice were given low doses of ampicillin, colistin, flumequin, gentamicin, tetracycline, or streptomycin via drinking water for 2 weeks. The equilibrium between susceptible and resistant populations of bacteria was monitored daily in feces and compared with that of control mice given pure water. This model yielded reproducible data, and dose and response were strongly correlated. The minimum selecting doses ranged from 0.9 te 12.8 µg/ml of water, depending on the antibiotic and the R plasmid. The use of mathematical models and complementary in vitro experiments accounted for the effect of the low antibiotic levels

ProDom and ProDom-CG: tools for protein domain analysis and whole genome comparisons

ProDom contains all protein domain families automatically generated from the SWISS-PROT and TrEMBL sequence databases (http://www.toulouse. inra.fr/prodom.html ). ProDom-CG results from a similar domain analysis as applied to completed genomes (http://www.toulouse.inra.fr/prodomCG.html ). Recent improvements to the ProDom database and its server include: scaling up to include sequences from TrEMBL, addition of Pfam-A entries to the set of expert validated families, assignment of stable accession numbers, consistency indicators for domain families, domain arrangements of sub-families and links to Pfam-A

Targeting colon luminal lipid peroxidation limits colon carcinogenesis associated with red meat consumption

Red meat is probably carcinogenic to humans (WHO/IARC class 2A), in part through heme iron-induced lipoperoxidation. Here, we investigated whether red meat promotes carcinogenesis in rodents and modulates associated biomarkers in volunteers, speculating that an antioxidant marinade could suppress these effects via limitation of the heme induced lipid peroxidation. We gave marinated or non-marinated beef with various degrees of cooking to azoxymethane-initiated rats, Min mice, and human volunteers (crossover study). Mucin-depleted foci were scored in rats, adenoma in Min mice. Biomarkers of lipoperoxidation were measured in the feces and urine of rats, mice, and volunteers. The organoleptic properties of marinated meat were tested. Fresh beef increased colon carcinogenesis and lipoperoxidation in rats and mice and lipoperoxidation in humans. Without an adverse organoleptic effect on meat, marinade normalized peroxidation biomarkers in rat and mouse feces, reduced peroxidation in human feces and reduced the number of Mucin-depleted foci in rats and adenoma in female Min mice. This could lead to protective strategies to decrease the colorectal cancer burden associated with red meat consumption