title: Alteration in surface charge of chimpanzee sperm during epididymal transit and at ejaculation.
abstract: To further investigate changes in the sperm surface occurring during epididymal transit and after ejaculation, the surface negative charge on the head of chimpanzee sperm recovered from the caput (n = 4) and cauda epididymis (n = 3) and from the ejaculate (n = 4) was measured. Washed sperm were exposed to colloidal iron at pH 1.6, washed, mounted on carbon plates, and examined in a scanning electron microscope equipped with an energy dispersive X-ray analyzer. This technique permits evaluation of individual sperm in a population and provides information not available when the entire population is measured as a whole. The results demonstrate a net increase in negative charge during epididymal transit and after ejaculation and a change in charge distribution within the population from a unimodal to a tetra modal distribution. Caput sperm showed a unimodal distribution with a mode of 20 +/- 2%. Cauda sperm showed three modes at 23 +/- 1, 34 +/- 3, and 41 +/- 3%. Ejaculated sperm showed four modes at 21 +/- 3, 31 +/- 4, and 40 +/- 2, and 46 +/- 2%. The sperm population in the chimpanzee epididymis and ejaculate is not homogeneous, and this technique will aid in future measurement of fertility of subpopulations of sperm in the ejaculate.
mesh_terms: D000818:Animals; D004542:Ejaculation; D004594:Electrophysiology; D004822:Epididymis; D008297:Male; D002679:Pan troglodytes; D013077:Sperm Head / Q000502:physiology; D013081:Sperm Motility; D013094:Spermatozoa / Q000502:physiology* / Q000648:ultrastructure; D013499:Surface Properties