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Staphylococcus aureus is responsible for a wide range of infections in human and animals. We found that S aureus slowed down host cell proliferation and induced a cytopathic effect. We demonstrated that S aureus induced a G2/M phase transition delay in host cells, which was associated with accumulation of the cyclin-dependent kinase Cdk1/cdc2 and unphosphorylated histone H3. We found that a G2 phase delay was preferential for bacterial internalization and intracellular proliferation. Using size exclusion chromatography and mass spectroscopy analysis, we identified phenol-soluble modulin alpha (PSMα) peptides as the candidates for this effect. The implication of PSMα in cell cycle alteration was confirmed by testing of synthetic PSMα and by comparison of LACwt with the isogenic mutant LAC∆psm, which lacks the operon encoding PSMα. The delay was associated with a decrease of defensins expression in a G2 phase, suggesting that PSMα-induced G2/M phase transition delay deteriorates antibacterial state of the epithelial surface.Investigation of the response to Escherichia coli and S. aureus showed a higher expression of key cytokines IL-6, IL-8, as well as IL-32 (which is involved in dendritic cell maturation) in E. coli-infected host cells. Comparison of cytokines expression in response to LACwt with isogenic mutants, which lack the operon encoding PSMs, show that PSMs inhibit interleukins production, thus impair the innate and adaptive immune response during S. aureus infection. Therefore we show, that PSMs alter the host cell cycle, resulting in a reduction of defense response of host’ cells, that reveal a newly-identified mechanism for promoting infection.

The present situation and perspectives on milking and milk production of dairy sheep in Europe, the Middle East and North America

15 crossbred dairy cows divided into control (basal diet; n=7) and restricted diet (60% grass silage and 40% hay; n=8) groups. Milk yield and composition were determined, and mammary glands were removed and weighed after 11 weeks of lactation. Results revealed that milk yield was lower in restricted diet group from calving to slaughter. Restricted feeding decreased milk protein content and milk lactose content with similar milk fat composition. Mammary glands of restricted diet group cows were lighter than control. Apoptosis in the mammary gland was higher in the restricted diet animals. It is concluded that lower milk yield induced by nutrient restriction in lactating dairy cows is partly due to the lower number of mammary cells.

The aim of this study was to investigate the effects of a severe nutrient restriction on mammary tissue morphology and remodeling, mammary epithelial cell (MEC) turnover and activity, and hormonal status in lactating dairy cows. We used 16 Holstein × Normande crossbred dairy cows, divided into 2 groups submitted to different feeding levels (basal and restricted) from 2 wk before calving to wk 11 postpartum. Restricted-diet cows had lower 11-wk average daily milk yield from calving to slaughter than did basal-diet cows (20.5 vs. 33.5kg/d). Feed restriction decreased milk fat, protein, and lactose yields. Restriction also led to lower plasma insulin-like growth factor 1 and higher growth hormone concentrations. Restricted-diet cows had lighter mammary glands than did basal-diet cows. The total amount of DNA in the mammary gland and the size of the mammary acini were smaller in the restricted-diet group. Feed restriction had no significant effect on MEC proliferation at the time of slaughter but led to a higher level of apoptosis in the mammary gland. Gelatin zymography highlighted remodeling of the mammary extracellular matrix in restricted-diet cows. Udders from restricted-diet cows showed lower transcript expression of a-lactalbumin and kappa-casein. In conclusion, nutrient restriction resulted in lower milk yield in lactating dairy cows, partly due to modulation of MEC activity and a lower number of mammary cells. An association was found between feed restriction-induced changes in the growth hormone-insulin-like growth factor-1 axis and mammary epithelial cell dynamics.

Many molecules are inducibly localized in lipid rafts, and their alteration inhibits early activation events, supporting a critical role for these domains in signaling. Using confocal microscopy and cellular fractionation, we have shown that the pool of Bad, attached to lipid rafts in proliferating cells, is released when cells undergo apoptosis. Kinetic studies indicate that rafts alteration is a consequence of an intracellular signal triggered by interleukin-4 deprivation. Growth factor deprivation in turn induces PP1α phosphatase activation, responsible for cytoplasmic Bad dephosphorylation as well as caspase-9 and caspase-3 activation. Caspases translocate to rafts and induce their modification followed by translocation of Bad from rafts to mitochondria, which correlates with apoptosis. Taken together, our results suggest that alteration of lipid rafts is an early event in the apoptotic cascade indirectly induced by interleukin-4 deprivation via PP1α activation, dephosphorylation of cytoplasmic Bad, and caspase activation.

National audience; Several experiments were conducted for evaluating the effects of once daily milking (ODM) in Lacaune dairy ewes throughout the milking period. Milk production and composition, udder health, daily feed intake and energy metabolism were individually monitored. The effects of adopting ODM at the farm and the production region levels were also modelled. Individual milk yield was 14% lower either in adult or primiparous ewes. Milk fat and protein contents were lower and higher, respectively, when ewes were fed ad libitum; however, these parameters were almost not modified when diets were adjusted to the actual milk yield. Dry matter intake was not affected by ODM, which led to a marked positive energy balance in ODM ewes. The last was well illustrated by the metabolic profile of the ewes, showing lower body reserves mobilization in ODM ewes. The udder morphology and functioning was only disturbed during the first week of ODM, but it was rapidly recovered without associated further health constraints. At the farm level, adopting the ODM regime showed a decrease in the global farm incomes, possibly to be recovered by starting ODM in the mid-lactation or prolonging the milking period length. Further researches will be required for characterizing in a deeper way the related effects of applying ODM under different feeding and management situations at the flock, farm and regional production scales.; Une série d’expérimentations a été conduite pour mesurer l’impact de la monotraite à l’échelle de la lactation de brebis laitières de race Lacaune. La production de lait et sa composition, la physiologie et la morphologie de la mamelle, l’ingestion et le métabolisme énergétique ont été mesurés tout au long de la période de traite, du sevrage au tarissement. L’impact de la monotraite a été modélisé à l’échelle de l’exploitation et du bassin de production. La perte de lait a été de 14% chez les multipares comme les primipares. Selon la ration offerte, le taux butyreux a diminué ou a eu tendance à augmenter, alors que le taux protéique n’a pas été modifié ou a augmenté en lien avec une augmentation des protéines solubles. Les quantités ingérées n’étaient pas différentes entre brebis en traite biquotidienne et monotraite, ce qui a entraîné un bilan énergétique positif supérieur pour ces dernières. Cela s’est traduit par des taux d’acides gras non estérifiés rapidement plus bas et de leptine supérieurs. La mamelle a été perturbée dans les premiers jours de monotraite, mais a rapidement retrouvé son intégrité du fait d’une bonne plasticité sans aucune conséquence sur sa santé. Au niveau de l’exploitation, la monotraite entraîne une perte de revenu qui peut être compensée en tout ou partie par un passage en monotraite à un stade plus tardif ou un allongement de la période de traite. Des travaux complémentaires conduits à l’échelle de l’exploitation permettraient de mieux préciser les répercussions de cette pratique à ce niveau et à celui du bassin de production.