Summary
The surface morphology of rabbit spermatozoa, fixed in situ (female reproductive tract) and prepared for scanning electron microscopy by critical point drying, was studied for as many as 36 hours post coitum. The findings demonstrate that 1) spermatozoa in the reproductive tract following coitus exist as a heterogenous, morphological population and 2) with time, shifts within this population from one predominant morphology to another take place.
In the fresh ejaculate, most spermatozoa have intact surfaces free of membranous disruptions. With time, a process of labilization (denudation) of the membranes covering the acrosomal region occurs in a progressively larger proportion of spermatozoa. The labilization originates by a process of vesiculation and/or vacuolation and leads to the appearance of a series of small fenestrations or perforations of the surface membranes. The perforations coalesce, and gradually larger areas of the surface membranes are eroded such that by 15 hours post coitum, the outer acrosomal membrane, as well as other acrosomal areas, are to varying degrees, directly exposed to the uterine milieu.
Secretory granules, picked up by cilia and transferred to the spermatozoa become localized over the acrosomal region shortly after coitus. The possible significance of these time-dependent, morphological events with the phenomena of capacitation and the “true” and “false” acrosome reactions are discussed.
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This investigation was partially supported by NIH grant HD-04274 and by a special fund of the Italian Foreign Office and was made in the Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado. We are indebted to Professor Keith R. Porter for his generosity in making laboratory facilities available.
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Motta, P., Van Blerkom, J. A scanning electron microscopic study of rabbit spermatozoa in the female reproductive tract following coitus. Cell Tissue Res. 163, 29–44 (1975). https://doi.org/10.1007/BF00218589
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DOI: https://doi.org/10.1007/BF00218589