Some nucleocytoplasmic exchanges during spermiogenesis of boar, ram, and stallion

The problem of how the successive nucleoproteins enter and leave the nucleus of mammalian spermatids is studied with electron microscopy in thick and thin sections of testis, stained en bloc with the procedure of Thiery and Rambourg [1976], which is able to immobilize small molecules. Staining at different pH values reveals that the stain could demonstrate some spermatidspecific nucleoproteins in elongating nuclei and the spermatozoa-specific protamines in elongated nuclei of the boar, the ram, and the stallion. The stained substances enter or leave the nuclei at precise steps in spermiogenesis. They follow several ways inside a special apparatus made rigid with the manchette. The apparatus is composed of the endoplasmic reticulum, continuous with the nuclear envelope, and of the nuclear pockets continuous with the nuclear pores. In the stallion and the boar, cytoplasmic granules, surrounded by a double wall of membranes, fuse with the nuclear envelope at the time the protamines enter the nucleus.