In vitro effects of dexamethasone on mouse ovarian function and pre-implantation embryo development.

The effect of dexamethasone (5-80 microg/ml) on ovarian function and embryo development was studied in mice. The follicle bio-assay revealed no effects of DEX up to 40 microg/ml on folliculogenesis and oogenesis, whereas 80 microg/ml hampered follicle differentiation and oocyte maturation. Androgen, estrogen and progestin secretion patterns were strongly impaired at all doses levels.

Severity of E. coli mastitis is mainly determined by cow factors.

Intramammary infections of dairy cows with Gram-positive bacteria such as Staphylococcus aureus (major cause of mastitis) have received a lot of attention because of their major economic impact on the dairy farm through production losses induced by an increase in somatic cell count. Management strategies, including greater awareness for efficient milking and hygienic measures, have limited the spread of Gram-positive bacteria and resulted in a significant decrease of proportion of S. aureus isolates and subclinical mastitis worldwide.

Sex steroid hormones do not influence the oxidative burst activity of polymorphonuclear leukocytes from ovariectomized cows in vitro.

During the periparturient period, dairy cows are subjected to physiological changes that may induce immunosuppression and an increased susceptibility of the animal to bacterial infections such as mastitis. The incidence of clinical environmental mastitis is high during the last period of gestation, at parturition and during the first month of lactation, suggesting a potential influence of sex steroid hormones. Efficient functioning of polymorphonuclear leukocytes (PMN) is necessary during the early phase of infection to clear the mammary gland from invading pathogens.