Longitudinal section of a sperm head showing the perforatorium (p), acrosomal vesicle
(a), and extra-acrosomal tissue (e).
Store-operated calcium channels trigger exocytosis of the sea urchin sperm acrosomal vesicle
It is placed in the cellular nucleus apix and presents several parts: primary acrosomal vesicle
, secondary acrosomal vesicle
, axial rod and capitullum, acrosomal tube and periaxial sheath (Fig.
This interaction initiates the acrosome reaction, resulting in the exocytosis of the acrosomal vesicle
and exposing the previously hidden inner acrosomal membrane including the basal ring.
During the spermiogenesis process of isogenic black mice, it was observed in early spermatids (round) at Golgi phase, some changes in the Golgi apparatus region, which contributes with carbohydrate-rich material to form 2 or 3 pro-acrosome granules that associate to form the acrosome granule contained in an acrosomal vesicle
. In this phase, the cells presented spheroidal nucleus and rugous endoplasmatic reticulum, located preferentially around the nucleus.
The head is composed largely of the cone-shaped nucleus, topped with a spherical acrosomal vesicle
situated at the tip.
As in higher vertebrates, the bell-shaped acrosomal vesicle
covers the apical portion of the nucleus, although it covers only a very limited region (Morisawa, 1995).
A small cone-shaped acrosomal vesicle
projects from the cell surface in close association with the flagellum and associated distal centriole (Fig.
Careful reexamination of their sections, however, revealed the presence of the minute acrosomal vesicle
, which is separated from the nuclear extension by a basal plate (Figs.
Classic studies on echinoderms have shown that contact with the egg jelly coat induces exocytosis of the acrosomal vesicle
, which releases lysins that dissolve the egg envelopes (see reviews by Colwin et al., 1975; Tilney, 1985; Epel and Vacquier, 1978).
The membranes outlining the acorn-shaped sperm head, acrosomal vesicle
, short acrosomal filament within the vesicle, and the sperm tail also showed very weak yellowish-orange fluorescence [ILLUSTRATION FOR FIGURE 1 OMITTED].