Effects of postnatal exposure to a mixture of polychlorinated biphenyls, p,p'-dichlorodiphenyltrichloroethane, and p-p'-dichlorodiphenyldichloroethene in prepubertal and adult female Sprague-Dawley rats.

The postnatal period is a critical phase of development and a time during which humans are exposed to higher levels of persistent organic pollutants (POPs), than during subsequent periods of life. There is a paucity of information describing effects of postnatal exposure to environmentally relevant mixtures of POPs, such as polychlorinated biphenyls (PCBs), p,p'-dichlorodiphenyltrichloroethane (DDT), and p,p'-dichlorodiphenyldichloroethene (DDE). To provide data useful for the risk assessment of postnatal exposure to POPs, mixtures containing 19 PCBs, DDT, and DDE were prepared according to their concentrations previously measured in the milk of Canadian women, and dose-response effects were tested on the proliferation of MCF7-E3 cells in vitro, and in vivo experiments.

Glucocorticoids inhibit the transcriptional response of the uncoupling protein-1 gene to adrenergic stimulation in a brown adipose cell line.

Glucocorticoids may inhibit brown adipose tissue (BAT) thermogenesis acting at a central level as well as reducing the responses of the tissue to adrenergic stimulation in vivo. This latter effect is not well understood. We investigated whether or not glucocorticoids directly reduce the expression of the key molecule for BAT thermogenesis, uncoupling protein-1 (UCP1), and if so, to what extent and by what mechanisms.

Levels of messenger RNA encoding ovarian receptors for FSH and LH in cattle during superovulation with equine chorionic gonadotrophin versus FSH.

This study tested the hypothesis that luteal LH receptor (LHr) and follicular LHr and FSH receptor (FSHr) steady-state mRNA levels are greater during superovulation with equine chorionic gonadotrophin (eCG) compared with that with FSH. Heifers were stimulated with eCG (n = 10) or FSH (n = 10), and ovaries were recovered the day before and at 12 and 24 h after luteolysis was induced with prostaglandin F2 alpha (PGF2 alpha). Total RNA was purified from individual follicles and corpora lutea.

Ovarian follicular steroidogenic acute regulatory protein, low-density lipoprotein receptor, and cytochrome P450 side-chain cleavage messenger ribonucleic acids in cattle undergoing superovulation.

Ovarian hyperstimulation with eCG in cattle results in increased plasma estradiol and progesterone concentrations, whereas hyperstimulation with FSH increases only estradiol concentrations. This study tested the hypothesis that eCG, compared to FSH, increases mRNA abundance for steroidogenic acute regulatory protein (StAR), low-density lipoprotein receptor (LDL-R), and/or cytochrome P450 cholesterol side-chain cleavage (P450scc), the main elements of the progesterone biosynthetic pathway. Heifers were stimulated with eCG (n = 10) or commercial FSH (n = 10), and ovaries were removed by colpotomy the day before and at 12 and 24 h after luteolysis was induced with prostaglandin (PG) F2alpha.

Follicular 3 beta-hydroxysteroid dehydrogenase and cytochromes P450 17 alpha-hydroxylase and aromatase messenger ribonucleic acids in cattle undergoing superovulation.

In this study, we tested the hypothesis that there is altered abundance of transcripts of genes coding for the enzymes cytochrome P450 17 alpha-hydroxylase (P450(17 alpha)), cytochrome P450 aromatase (P450arom), and 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) in follicles of cattle hyperstimulated with eCG compared to FSH. Treatments were initiated on Day 10 of the cycle, and all cows received prostaglandin (PG) on Day 12. In experiment 1, blood samples were taken to determine plasma progesterone and estradiol concentrations during ovarian stimulation.