ULTRASTRUCTURAL IMMUNOLOCALIZATION OF HISTONES (H2B, H3, H4), TRANSITION PROTEIN (TP1) AND PROTAMINE IN RABBIT SPERMATIDS AND SPERMATOZOA NUCLEI - RELATION TO CONDENSATION OF THE CHROMATIN

The histones H2B, H3 and H4, the transition protein TP1 and protamine were localised using ultrastructural immunocytochemistry in nuclei of rabbit spermatids and spermatozoa. Histones are present in round sperm atid nuclei and are lost during the elongation of nuclei. TP1 and prot amine appear simultaneously in all nuclei during this period. TP1 is l ocated at the periphery of chromatin cords, while protamine seems to b e located at random in the same cords. TP1 is lost in most elongated s permatids during step 13 of spermiogenesis, and the protamine stays in all sperm nuclei. TP1 remains present in some old spermatids and ejac ulated spermatozoa. In the rabbit, 3-6% of sperm nuclei decondense spo ntaneously. Most are characterised by a retention of TP1. Respective r oles of TP1 and the protamine in spermatid nuclear condensation are di scussed.