Lack of a head in human spermatozoa from sterile patients: a syndrome associated with impaired fertilization.

Three patients with primary sterility in whom the majority of spermatozoa lacked a normally implanted head are presented. A small cephalic knob was evident in most of them by routine colorimetric techniques, and the Feulgen reaction failed to show any deoxyribose nucleic acid. The morphologic features of the tails was normal. Few loose sperm heads were observed in the ejaculates. Even though motility was decreased, there were numerous acephalic sperms with different degrees of forward motility. Electron microscopy showed a well-organized structure of the centrioles and connecting piece, which were located in the neck region within a small cytoplasmic mass, but no chromatin was detected in any case. Studies on immature spermatids present in semen evidenced an independent anomalous development of heads and tails and suggested that they became separated at the end of spermatid maturation. This anomaly, of probable genetic origin, is interpreted to be due either to an alteration in the mechanism of migration and positioning of the tail on the caudal pole of the nucleus or to an interference with the formation of the implantation fossa of the head, which normally accommodates the connecting piece.