An ultrastructural study of the head region of bovine spermatozoa

Publisher Website
Google Scholar
Abstract
Differential interference micrographs, electron micrographs of thin sections, and electron micrographs of freeze-etched preparations have been used in a coordinated study of the head structure of bovine spermatozoa. The equatorial segment can be visualized by all three methods but it is more clearly defined in aged cells in which the plasmalemma covering the apical region is loosened. The thinning of the acrosome in the equatorial segment allows the penetration of postnuclear-cap material both into the subacrosomal space and into the transition zone between the acrosome and the plasmalemma to produce an 'overlap' structure in this region.The plasmalemma cleaves predominantly in the median hydrophobic zone and this cleavage plane is both distorted by underlying structures and physically modified by its apposition to these structures. These physical modifications are reflected in the formation of 'plaques' by departures from the median cleavage plane in some areas and in the arrangements of globular particles, which are equated with protein complexes. Rings of globular particles within the cleavage plane of the plasmalemma are coincident with underlying nuclear pores in the diverticula. The median cleavage of the outer acrosomal membrane exposes numerous globular particles in linear arrays. Spiralized linear structures resembling microtubules are seen in the postnuclear cap.