Occurrence and Structure of Intercellular Bridges between the Human Spermatogonia

Abstract

The intercellular bridges between the spermatogonia in adult man were observed by electron microscopy with the following results.
The bridges were usually barrel-shaped with a slight convexity at the middle (1.0-1.5μ both in diameter and length). A layer of an electron dense material (40-50mμ thick) occurred directly beneath the plasma membrane of the bridges. Besides various cytoplasmic organelles, microtubules were frequently found in the bridges.
The bridges were demonstrated between type A as well as type B spermatogonia. It was proposed that the synchronizing differentiation, by means of the intercellular bridges, of the germ cells starts from the division of “dark type A” spermatogonia into “pale type A” spermatogonia (designation by CLERMONT), and that thereby it is possible to yield groups of, at the most, thirty-two interconnected spermatids. The concept of FAWCETT (1961) that the intercellular bridge first occurs between primary spermatocytes as result of the last spermatogonial division and that the groups of eight interconnected spermatids are subsequently formed was criticized.