The cells in meiosis are called spermatocytes which are formed from the last spermatogonial division and represent the meiotic stage of the male germ-cells. The process of meiosis comprises two divisions, the cells before the first division are called primary spermatocytes (spermatocytes I), after the first division secondary spermatocytes (spermatocytes II). The cells about to enter meiosis usually are designated as resting spermatocytes (Leblond and Clermont 1952b). Since their nuclei synthesize DNA prior to the first meiotic division (Monesi 1962, Hilscher 1964), and thus are active metabolically, they are termed preleptotene spermatocytes. The nuclei of these cells are smaller and darker than those of B2 spermatogonia (Guraya and Bilaspuri 1976a, c, Bilaspuri and Guraya 1980a, 1984b, 1986a) or B1 spermatogonia in most species (Clermont 1972, Roosen-Runge 1977). These contain fine chromatin filaments besides the dark chromatin granules lying adjacent to the nuclear envelope and in the central nucleoplasm. The advanced pachytene spermatocytes are the largest spermatogenic cells of the seminiferous epithelium (Table 1). The nucleus and cytoplasm of primary spermatocytes increase markedly in volume during the meiotic prophase. Sertoli cells are just as large in total volume as pachytene spermatocytes (Bellvé et al. 1977a).
KeywordsSertoli Cell Synaptonemal Complex Meiotic Division Meiotic Prophase Spermatogenic Cell
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