Nuclear basic protein changes during spermiogenesis in the longnose skate and the spiny dogfish.

Nuclear shape and the organization of nuclei within the seminiferous follicles have been used to divide spermiogenesis in the longnose skate, Raja rhina, into eight stages and in the spiny dogfish, Squalus acanthias, into seven stages. Cytochemical techniques for basic proteins reveal that as spermatid nuclei begin to elongate they have the somatic histone complement, and as they complete elongation they contain a very arginine-rich, TCA-extractable complement, or the salmon sperm histones type. After the nuclei have developed their ultimate corkscrew shape the final transition takes place to a very arginine-rich, TCA-stable complement, or the mammalian sperm histone type. These nuclei were not rich in sulfhydryl groups, but they were extractable with sodium thioglycolate. In addition, a number of variables affecting TCA extraction and subsequent alkaline fast green staining are described.