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G. T. Taylor, J. Weiss and T. Frechmann

Summary. Epididymal sperm quantity and quality were examined throughout the reproductive lifespan of sexually experienced and inexperienced rats. Males were housed with gonadally intact or ovariectomized females for 2 weeks to 1 year, and epididymides were analysed 1 week to 9 months after the females were removed. Results for the virgin males suggest a peak in sperm numbers at 6 months of age followed by a gradual decline and then notable decrements in sperm numbers and motility by 24 months of age. The same general pattern emerged for sexually experienced males, with two exceptions. There was a chronic increase of sperm numbers relative to those of virgin males at every age examined, and the decline in spermatozoa with ageing was slowed by previous sexual contact. The implications of these data for the ontogeny of fertility are not readily apparent because the epididymis remained reproductively functional throughout the lifespan. We do, however, suggest that epididymides are sensitive to experiential and hormonal changes during adulthood and, most important, the effects of these changes are maintained chronically and into old age.

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G. T. Taylor, J. Weiss, T. Frechmann and J. Haller

Summary. The temporal changes in epididymal sperm numbers during the month after sexual contact were examined in 80 adult albino rats. The comparably sexually experienced males in 6 experimental groups were allowed 3 ejaculations with ovariectomized females in which oestrus was induced by hormone injections. Epididymides were removed from the experimental males 1 h, 1 day, 2 days, 3 days, 7 days or 30 days later. Control males were sexually inexperienced or sexually experienced and living with females. Epididymal sperm counts revealed a pattern that resembled an inverted V-shaped function with a peak at 48 h after copulation. We suggest that sexual activity provokes an acute attentuation of sperm disposal within the epididymis with the result that more spermatozoa are available for ejaculation during sexually active times.

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T. J. Weiss, R. F. Seamark, J. E. A. McIntosh and R. M. Moor

Summary.

This study was undertaken (i) to establish a relationship between cyclic AMP (cAMP) production and the degree of LH and FSH stimulation; (ii) to determine the effects of various gonadotrophins on follicular formation of cAMP; and (iii) to identify the precise intrafollicular site of cAMP formation.

The formation of cAMP increased rapidly in follicles exposed to LH. Maximum concentrations were reached after 90 min and were maintained for 180 min. Extracellular release of cAMP increased steadily throughout the 180-min experimental period. Tissue levels of cAMP increased proportionally and significantly when LH concentrations in the medium were increased from 0 to 200 mi.u. ml-1.

Tissue levels of cAMP were significantly increased by HCG, prostaglandin E-2 and noradrenaline, but not by prolactin, prostaglandin F-2α, serotonin or melatonin.

Cyclic AMP formation occurred predominantly in the thecal compartment; the membrana granulosa contributed less than 3 % of the total amount of cAMP formed after gonadotrophic stimulation. A significant amount of cAMP from the thecal cells was released into the extracellular compartment and appeared to pass into the granulosa cells.