The blood-testis barrier in vertebrates having different testicular organization
The ultrastructure of Sertoli-Sertoli and Sertoli-germ cell surface specializations in the domestic fowl was studied in material fixed by vascular perfusion through the thoracic aorta. Three main types of surface specializations were found between adjacent Sertoli cells. These are focal tight junctions, desmosome-like devices, and a specialization characterized by the presence of long and dilated subsurface cisternae of rough endoplasmic reticulum. Typical inter-Sertoli cell junctions similar to those of mammals were absent. Germ cells were attached to Sertoli cells mainly by desmosome-like devices of varying appearance. The junctions between Sertoli cells and elongating or elongated spermatids, "the mantle", consisted of only slight condensations of filamentous material in the Sertoli cell. The tight junctions between adjacent Sertoli cells were efficient in preventing lanthanum from passing towards the lumen beyond the level of the spermatogonia.