Introduction

Abstract

Spermatogenesis is a complex process of differentiation, involving germ-cell proliferation and renewal, meiosis, and spermiogenesis under the influence of Sertoli cells. It is characterized by complex morphological and biochemical transformations that lead to the formation of a highly specialized cell, the haploid spermatozoon. The spermatozoa are genetically diverse owing to the meiotic events of gene recombination and chromosome reassortment. The Sertoli cells forming the critical site for FSH and androgen-mediated biosynthetic events play important roles in the regulation of proliferation and differentiation of germ-cells in the seminiferous epithelium. The considerable progress evident in research on the normal development, differentiation, structure, biochemistry and physiology of spermatozoa in mammals owes much to the perfection of older and the evolvement of new techniques of transmission and scanning electron microscopy, lectin labelling and binding, histochemistry, autoradiography, biochemistry, quantitative research, biophysics, immunology, etc., which have been applied to the study of germ-cells and Sertoli cells both in vivo and in vitro. It is now possible to culture discrete segments of seminiferous epithelium at specific stages of spermatogenesis and separate germ-cells or Sertoli cells, thus allowing the investigator to isolate and monitor specific cell-mediated events. Electron microscopy of thin sections, surface replicas, freeze-cleaving and freeze-etching has made it possible to split the sperm specializations within the plane of the membrane specializations that may be important to the acrosome reaction and to gamete recognition and membrane fusion, which constitute the fundamental events of fertilization (Yanagimachi 1978a, Metz 1978, Shapiro and Eddy 1980, Clegg 1983, Shapiro 1984).