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The sera of ninety-six reproductively normal cows and twenty-sex artificial insemination bulls were typed for transferrin and for J antigen. Fertility of the cows was measured by examination of the genital tracts between 2 and 26 days after insemination at post-mortem or laparotomy. No significant relationship was observed between fertility and transferrin type or J antigen in these experimental animals. The results of approximately 90,000 inseminations with semen from the twenty-six bulls were also studied in relation to these types and again there was no useful association.

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H. Anne Leaver and G. S. Boyd

Summary. Immature rats were injected with PMSG (Day 0) and hCG (Day 3). PMSG caused an increase in cholesterol side-chain cleavage activity and the concentration of its terminal oxidase, cytochrome P-450, and an increase in cholesterol ester hydrolase activity in ovarian homogenates; the activity of both enzymes was further increased after hCG injection. Cholesterol ester hydrolase activity/mg ovarian wet weight was unchanged between Days 0 and 13, but the concentration of cytochrome P-450/mg wet weight increased 3-fold between Days 5 and 6. Cholesterol side-chain cleavage activity, measured in terms of pregnenolone production/mg wet weight, showed its largest increase (10-fold) between Days 6 and 7. Addition of exogenous cholesterol maintained the rate of pregnenolone production in incubated ovarian homogenates on Days 7–9.