IDENTIFICATION OF THE MIDPIECE AND TAIL OF THE SPERMATOZOON DURING FERTILIZATION OF HUMAN EGGS <i>IN VITRO</i>

Abstract

Positive identification of the sperm midpiece and tail in the vitellus establishes beyond reasonable doubt that pronucleate eggs are undergoing fertilization. Previously Edwards, Bavister &amp; Steptoe (1969) tentatively identified sperm midpieces in pronucleate human eggs fertilized in vitro. Unequivocal evidence of midpieces and tails in eggs undergoing fertilization is now presented. Oocytes recovered from two ovaries excised 3 hr previously were cultured in a mixture containing three parts follicular fluid : one part of Bavister's medium (Bavister, 1969). Four samples of follicular fluid were used, three being straw-coloured and a fourth, which was slightly pink, probably came from an atretic follicle. After 36 to 37 hr in culture, the eggs were washed through two or three changes of Bavister's medium, the dilution of the follicular fluid being approximately 1:100. Ejaculated spermatozoa were washed twice in this medium and then added to some of the eggs at a concentration of