Selective uptake by the Sertoli cells of cytoplasm from normal spermatogonia in the rat testis.

Electron microscopical examination of germ cells during their development from early type A spermatogonia to late pachytene spermatocytes showed that small, spherical pseudopodia emerged from type B spermatogonia and, to a lesser degree, from intermediate spermatogonia and early spermatocytes. Serial sections showed that the pseudopodia pinched off from the type B spermatogonia and were engulfed by the adjacent Sertoli cells. Groups of dense bodies were found in the Sertoli cells adjacent to the engulfed islands of germ cell cytoplasm. At a few instances islands of germ cell cytoplasm were seen to fuse with dense bodies in the Sertoli cells. The fate of the cytoplasmic islands is unknown, but phagocytosis by the Sertoli cells may be suggested. The findings indicate a new type of interaction between Sertoli cells and certain classes of spermatogonia.