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This study describes for the first time the occurrence of seasonal variations in the semen of free-ranging rhesus monkeys (Macaca mulatta). During the breeding season, the animals produce semen which is normal in volume, quality, and physical characteristics, and contains a highly uniform population of motile and structurally normal spermatozoa; during the nonbreeding season, the animals either do not respond to electrostimulation, or they produce only minimal volumes of an ejaculate with abnormal physical characteristics, and consisting of a markedly reduced number of spermatozoa which are mostly nonmotile, structurally anomalous, degenerating and/or undergoing massive phagocytosis by macrophages. Testicular biopsy specimens from the same animals disclose that these semen variations are accounted for by marked differences in the activity of the seminiferous tubules which show florid spermatogenesis during the breeding season, and nearly complete spermatogenic arrest during the nonbreeding season. The seasonal variations noted in this study correlate well with other anatomical and physiological changes known to occur in these animals in association with their annual reproductive cycle, and provide another element of distinction between free-ranging and laboratory macaques where these seasonal fluctuations are either suppressed or greatly reduced.

The localization of angiotensin converting enzyme (ACE) in the gonads of the normal rabbit was studied by immunofluorescence and immunoelectron microscopy. The enzyme is present in the cytoplasm of testicular spermatids and of epididymal and ejaculated spermatozoa, and on the surface of follicular and tubal cocytes. These findings support the hypothesis that ACE has a role in gamete maturation and in fertilization.

In the course of a study on the morphogenesis of the adrenal gland in random-bred Swiss albino mice, we noted the presence of ectopic germ cells in the adrenal cortexes and medullas in animals of both sexes, from day 12 1/2 of fetal development to postnatal day 12. Up to day 15 of fetal development, the cells exhibited characteristics of primordial germ cells. At day 17, and irrespective of the sex of the fetus, they all entered meiosis in synchrony with those in the ovary. Postnatally, in females as well as males, all ectopic germ cells displayed morphologic characteristics identical to those of young oocytes in unilaminar ovarian follicles. No germinal elements were seen in the adrenal glands past day 12 of life. Our study shows that mammalian germ cells are capable of undergoing sustained differentiation outside the gonads and that, in ectopic sites, they all differentiate into oocytes as they normally would in the ovary, even in males.

One hundred fifty-nine human oocytes cultured from a minimum of 24 to a maximum of 53 h were studied by means of serial sectioning for high-resolution microscopy. On the basis of the morphologic characteristics displayed at the end of the culture period, 61 oocytes had remained meiotically inactive, 35 had resumed meiotic maturation and 42 had matured. In general, the fine morphologic features of the oocytes in the three groups were found to be similar to those of human oocytes at comparable stages of maturation in ovarian follicles: this demonstrates, morphologically at least, that the in vitroexperiments are valid models for studying human oocyte maturation. New observations resulting from this study concern the morphological changes associated with resumption of meiotic prophase which were observed in seven oocytes, the frequent presence in immature oocytes of eccentrically located nuclei and chromosomes, and the occurrence of maturation anomalies whose incidence, however, was extremely low.

This report describes the sequential changes associated with transformation of quiescent ovarian follicles into follicles with distended antra. Emphasis is placed on the fine morphology of the cells of the follicle wall and cumulus oophorus whose structural changes are correlated with physiologic aspects of oocyte maturation. The observations made in this study seem to indicate that most of these changes are directed at providing the oocyte with an environment suited for its maturation, and with substances necessary for its metabolism.