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A. B. Fajer

Summary. The metabolism of glucose changed significantly at the time of the onset of meiosis in the hamster ovary. There was a large drop in the CO2 evolution from labelled glucose and it could be attributed to alterations in the metabolic patterns in the germ cells which represented 80–90% of the ovarian cell population at the time of the studies. The reduced glycolytic metabolism was well established in the oocyte at the diplotene stage of the first meiotic division.

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Ovulation was induced in sexually immature squirrel monkeys by pmsg-hcg injections and pregnenolone and progesterone concentrations were determined in the ovarian venous blood. Extensive follicular growth does not permit the diagnosis of ovulation without histological examination of the ovaries. Ovulation was followed by extensive luteinization and detectable amounts of pregnenolone and progesterone 2 days after treatment but, by 5 days after treatment, only five out of eleven animals had detectable hormone concentrations. The interstitial tissue is suggested as the source of pregnenolone.

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Since Robson & Botros (1961) described the inhibitory effect of 5-hydroxytryptamine (5-HT) on the sexual development of mice, the hypothalamus has been postulated as a possible site for the action of the exogenous 5-HT. In the rat, introduction of serotonin directly into the third ventricle prevented maturation in normal female animals (Corbin & Schottelius, 1961) and delayed vaginal opening from an average of 39·7 to 47·6 days (O'Steen, 1965) when administered to young animals. Koe & Weissman (1966) have established that parachlorophenylalanine (p-CPA) markedly lowers the concentration of 5-HT in brain and other tissues and that, in brain, there is only a slight decrease in the levels of norepinephrine. The investigation reported here was designed to determine if the depletion of 5-HT in the
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Esterified and non-esterified (free) cholesterol concentrations were determined in the hamster ovary and isolated corpora lutea during the oestrous cycle, pregnancy and lactation. A significant decrease was observed in the esterified fraction between pro-oestrus and oestrus. The administration of phenobarbital at pro-oestrus prevented ovulation and the fall in the concentration of cholesterol esters. Luteal sterols, in cycling animals, expressed as mg/100 mg ovary were 16·3 to 19·0% and 4·3 to 7·5% of the total ovarian free and esterified cholesterol, respectively.

During pregnancy, concentrations of esterified cholesterol were lower than those found during the cycle. Of the total ovarian cholesterol, 38·7% of the free and 10·3% of the esterified fractions were found in the corpora lutea.

During both the oestrous cycle and pregnancy, a larger proportion of cholesterol was found in the interstitial cells and follicular elements rather than in the corpora lutea. This finding is supported by the high concentrations observed during lactation, when no corpora lutea are formed.