Sodium Selenide Toxicity Is Mediated by O2-Dependent DNA Breaks

Hydrogen selenide is a recurrent metabolite of selenium compounds. However, few experiments studied the direct link between this toxic agent and cell death. To address this question, we first screened a systematic collection of Saccharomyces cerevisiae haploid knockout strains for sensitivity to sodium selenide, a donor for hydrogen selenide (H2Se/HSe−/Se2−). Among the genes whose deletion caused hypresensitivity, homologous recombination and DNA damage checkpoint genes were over-represented, suggesting that DNA double-strand breaks are a dominant cause of hydrogen selenide toxicity. Consistent with this hypothesis, treatment of S. cerevisiae cells with sodium selenide triggered G2/M checkpoint activation and induced in vivo chromosome fragmentation. In vitro, sodium selenide directly induced DNA phosphodiester-bond breaks via an O2-dependent reaction. The reaction was inhibited by mannitol, a hydroxyl radical quencher, but not by superoxide dismutase or catalase, strongly suggesting the involvement of hydroxyl radicals and ruling out participations of superoxide anions or hydrogen peroxide. The •OH signature could indeed be detected by electron spin resonance upon exposure of a solution of sodium selenide to O2. Finally we showed that, in vivo, toxicity strictly depended on the presence of O2. Therefore, by combining genome-wide and biochemical approaches, we demonstrated that, in yeast cells, hydrogen selenide induces toxic DNA breaks through an O2-dependent radical-based mechanism

Studies on central baffin vegetation I. Bray Island

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43889/1/11258_2004_Article_BF00299587.pd

Relationship between rearing practices and eating quality traits of the muscle rectus abdominis of Charolais heifers

International audienceNinety-nine Charolais heifers with an average age of 3 3 months and an average carcass weight of 3 81 kg were used to study the relationship between rearing practices and eating meat quality traits. Farm surveys were carried out to collect information about heifer rearing before weaning, during the growth period and during the finishing stage. The quality of meat from the M. rectus abdominis excised 24 h post mortem was scored between 0 and 10 by sensory analysis using four descriptors: initial tenderness, overall tenderness (OT), juiciness and flavour intensity. Intramuscular fat content was also measured. Four classes of rearing practices were differentiated by multiple correspondence analysis and hierarchical cluster analysis. The class I was based on a low feeding level during the growth period and a diet of hay and straw complemented with 8 kg of concentrates in the barn during the finishing period. A medium feeding level during the growth period and a finishing diet of grass at pasture and 6 kg of concentrates defined the class 3. The class 2 was linked to a high feeding level during the growth period and a supply of roughage and 6 kg of concentrates at pasture during the finishing stage. The class 4 was based on a high feeding level during the growth period and a finishing stage in the barn with maize silage and 5 kg of concentrates. There were no differences in meat juiciness and meat flavour intensity among the four practice classes. The classes 2 and 4 produced the tenderest meat (OT score: 5.5/10; p = 0.002), regardless of the finishing stage and the forage given to the animals. These classes were characterized by the highest feeding level, which allowed slaughter at a young age (32 months) resulting in the highest carcass weight (380 kg). The classes I and 3 classes were linked to the lowest tenderness (OT score: 4.8;p=0.002) although the intramuscular fat content was equivalent to the classes 2 and 4 (17.8% in average). The classes I and 3 were characterized by a moderate growth period due to a low feeding level and a short finishing stage (108 to 13 5 days). Indeed, the finishing period did not allow the animals to recover the growth deficit brought about by the growth period. This type of farming practice required slaughter at a more advanced age (35.9 months) for equivalent carcass weights of 389 kg

Différenciation de la qualité sensorielle des viandes par le mode de conduite chez la génisse Charolaise

Qualité des produitsNational audienc

Type 3 resistant starch: influence on human gut microbiota and inflammatory response using complementary in vitro approaches

International audienc

Différenciation de la qualité sensorielle des viandes par le mode de conduite chez la génisse Charolaise

Qualité des produitsNational audienc

Increased topsoil mineral nutrient concentrations under exotic invasive plants in belgium

Exotic invasive plants can alter ecosystem processes. For the first time in Europe, we have analysed the impacts of exotic invasive plants on topsoil chemical properties. At eight sites invaded by five exotic invasive species (Fallopia japonica, Heracleum mantegazzianum, Solidago gigantea, Prunus serotina and Rosa rugosa), soil mineral element composition was compared between invaded patches and adjacent, uninvaded vegetation. We found increased concentrations of exchangeable essential nutrients under the canopy of exotic invasive plants, most strikingly so for K and Mn (32% and 34% increase, respectively). This result fits in well with previous reports of enhanced N dynamics in invaded sites, partly due to higher net primary productivity in exotic invasive plants compared to native vegetation