Ultrastructural and cytochemical changes of the head components of human spermatids and spermatozoa

Abstract

The ultrastructural study of chromatin condensation simultaneously with the evolution of the perinuclear organelles was conducted in the spermatids and epididymal and ejaculated spermatozoa of man with the aid of the “en bloc” alcoholic PTA staining and the EDTA regressive method. The round nuclei of young spermatids (steps 1, 2) were characterized by the persistence of nucleoli that were PTA positive, and the presence of a subacrosomal layer of well‐stained peripheral chromatin. In the beginning of the phase of nuclear elongation (step 3), the central chromatin also became dense, like the peripheral chromatin, while the nuclear ring and the associated manchette and the two anlages of the postacrosomal dense lamina and the posterior ring appeared. During steps 4 and 5, the sliding of the nuclear ring and the manchette, the growth of the postacrosomal dense lamina, and the progression of the posterior ring towards the base of the nucleus were seen along with structural and cytochemical modifications of the chromatin. In the flattened nuclei of step 4 spermatids, coinciding with the loss of the nucleolar components, the chromatin achieved maximum compactness in the entire nucleus and was PTA positive. In the spermatids of step 5, the disappearance of peripheral dense chromatin and the specific staining of the chromatin granules marked the beginning of the second stage of transformation of the basic nucleo‐proteins. The condensed nuclei of the mature spermatids were partially stained by PTA in step 6 and totally unstained in step 7. The PTA staining revealed the persistence of PTA‐positive chromatin areas in the nuclei of certain spermatids otherwise mature. The morphological aspect of the chromatin then remained the same in the nuclei of epididymal and ejaculated spermatozoa. These observations suggest that in man, as in other mammals studied, new proteins accumulate in the elongating nuclei of spermatids and are replaced at the phase of maturation by sperm‐specific nucleoproteins. The defects in condensation of the chromatin that occur during spermiogenesis could be related to the modalities of accumulation of intermediate nucleoproteins.

An antiserum against protamines for immunohistochemical studies of histone to protamine transition during human spermiogenesis

“…The increase of nuclear labelling at the late steps of spermiogenesis indicates that chromatin in spermatids is enriched in protamines, as has been shown by previous biochemical (Geremia et al, 1976;Loir & Lanneau, 1978;Grimes, 1986) and autoradiographic (Monesi, 1964(Monesi, , 1967Mayer & Zirkin, 1979) studies in several mammals. These observations are in agreement with ultrastructural and cytochemical data suggesting that, in man, protamines first appear in condensed nuclei of spermatids at steps 5-6 (Dadoune & Alfonsi, 1986). The lack of cytoplasmic labelling reinforces the hypothesis that protamines are not accumulated inside cytoplasm before their migration to the cell nucleus (Loir & Lanneau, 1978).…”

Expression of mammalian spermatozoal nucleoproteins

“…In the rat, TP1 appears in the nuclei of step 12 spermatids (Heidaran et al, 1988) and disappears by step 17 (Oko et al, 1996a), while TP2 is seen in the nuclei of step 13 spermatids (Alfonso and Kistler, 1993) and disappears by step 16 (Oko et al, 1996a). The immunocytological detection of TP1 in human spermatids at steps 3 and 4 and of TP2 from step 1 to step 5 (Steger et al, 1998) is in accordance with earlier ultrastructural cytochemical findings on chromatin condensation (Dadoune and Alfonsi, 1986). The pattern of protamine deposition is roughly identical in all the mammals studied.…”

Immunoelectron microscopic visualization of intermediate basic proteins HPI1 and HPI 2 in human spermatids and spermatozoa

“…during the chromatin condensation process. The nuclear labelling density strongly increased in elongating spermatids (steps 5 and 6) and then sharply decreased from step 6 to step 8 [21]. In man, histone-to-protamine replacement occurs at the beginning of the spermatid maturation phase [22].…”