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Search for other papers by H. M. MARSDEN in
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Search for other papers by F. H. BRONSON in
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SUMMARY
The effects were evaluated of exposing female C57BL/6J mice to different male and female environments before pairing on attainment of oestrus after pairing. In Expt. I, grouped female mice were exposed for 2 days to male urine of the same strain, a different strain (CBA/J), a different species (Peromyscus maniculatus bairdii), or to female urine of the same strain. Male urine of the same strain accelerated attainment of oestrus; exposure to male urine of a different species did not. Results on the significance of strain specificity were inconclusive. In Expt. II, grouped females were isolated in clean cages for 2 days before pairing, with and without exposure to male urine. A high degree of synchrony was obtained on the first night after pairing in both groups (about 60% of all females which mated in 4 days). Apparently, synchrony of oestrus in grouped females is as much, or more, a result of a release from the oestrus-suppressing effects of crowding (in all-female groups) as of stimulation by the odour of the male (male urine). Synchrony after pairing was also found in two albino strains of mice (SWR/J and SJL/J) which had been reared together in small groups.
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Search for other papers by T. H. HAMILTON in
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SUMMARY
Two experiments were performed to examine variations in whole-organ concentrations of RNA, DNA and protein, and specific activities of RNA in vivo in the mouse oviduct and uterus during the oestrous cycle and early pregnancy. Concentrations of DNA did not vary in the oviduct at any stage of the reproductive cycle in either study. In the first experiment with Yale Swiss mice, the concentration of RNA in the oviduct was highest at pro-oestrus, somewhat lower at mid-day of oestrus, and lowest on days 2, 4 and 12 after insemination. Concentrations of RNA were essentially identical in the oviducts of inseminated and non-inseminated females at mid-day of the day following ovulation. The second experiment, using CF-1 mice, confirmed these results, and, in addition, examined oviducal and uterine uptake and incorporation of [3H]uridine. Incorporation of the radioactive precursor into RNA was highest in the oviduct at mid-day of pro-oestrus, was markedly decreased before ovulation, and remained relatively low during the period of egg transport in both inseminated and non-inseminated mice. Most of the RNA necessary for appropriate oviducal function during zygote transport, therefore, is synthesized well before ovulation, and relatively little is formed during the 3 days of tubal residence. The general pattern of incorporation of [3H]uridine into RNA in the uterus appeared basically similar to that shown by the oviduct, except at mid-pregnancy when transcriptional activity of the oviduct genome was relatively low. The two organs also differed markedly in the magnitude of the pro-oestrous surge in RNA synthesis and accumulation, with the uterus showing a greater increase.
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SUMMARY
Gonadectomized female C57BL/6J mice were caged with males to determine the effect of male stimuli on release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Concentrations of hypophysial and plasma FSH were significantly higher after 3 days of exposure to males when compared with controls maintained in the absence of a male. Hypophysial and plasma concentrations of LH were also higher in females caged with males, but not significantly so. Ovariectomized females were given 0·01 μg. oestradiol benzoate daily for 4 days in a second experiment and the effect of cohabitation re-evaluated. There were no significant effects of exposure to males on either FSH or LH after the oestradiol injections. Therefore the presence of males enhances synthesis and release of FSH in gonadectomized females. In addition, the results of the second experiment suggest that oestrogen interferes with this response in some way, possibly blocking the neural pathway utilized by male stimuli.