Germ-cell death during prespermatogenesis in the testis of the golden hamster

Summary Degenerating prespermatogonial germ cells in the testis of the immature golden hamster [aged 14 days post conceptionem (dpc) to 13 days post partum [dpp)] were studied with regard to their morphology and temporal incidence. Judged by their ultrastructural features, these cells clearly take the form of apoptosis and finally are subjected to phagocytosis by neighboring Sertoli cells; only a few germ cells of a presumably incipient, partly variant degenerative morphology cannot, at present, be assigned to the apoptotic mode of cellular death. Degenerating prespermatogonia occur between the 14th dpc and 3rd dpp and again, after an interval in which no such cells are found, from the 9th dpp onwards. This pattern reveals a striking parallelism to the phases of proliferation of these cells, viz., the appearance of M- and T₂-prespermatogonia. Both this obvious temporal association of proliferation and degeneration and the classification of prespermatogonial death as apoptosis suggest some developmental significance of the degenerative phenomena investigated.     

Intercellular bridges between germ cells in the immature golden hamster testis: evidence for clonal and non-clonal mode of proliferation

Summary Intercellular bridges of prespermatogonia and of the first A-spermatogonia in the maturing testes of newborn to 17-day-old golden hamsters have been studied by electron microscopy. Incomplete cytokinesis of dividing M- and T₂-prespermatogonia and A-spermatogonia produces these bridges, which undergo different developmental fates. Bridges of the first A-spermatogonia are stable beyond subsequent mitoses of these cells; this gradually leads to the formation of bridge-connected groups of synchronously developing germ cells. Thus, the clonal mode of male germ cell proliferation is already established in this period of testis maturation. During mitoses, pre-existing bridges reversibly develop structural modifications, i.e. considerable elongation and formation of a bridge-partitioning complex. In contrast, intercellular bridges of prespermatogonia are mostly severed and become lost during subsequent mitoses of the cells involved; this results in separation of the germ cells and represents a mainly non-clonal mode of M- and T₂-prespermatogonial proliferation. Here, too, pre-existing bridges elongate and develop the bridge-partitioning complex during subsequent mitoses of the joined cells, but this is superposed and interrupted by the simultaneous process of disconnection of the bridges.Parts of this study were presented at the 85th meeting of the Anatomische Gesellschaft in Munich, April 1990     

The structure of the germinal dense bodies (nuages) during differentiation of the male germ line of the teleost,Oryzias latipes

Summary The germinal dense body (GDB) in the teleost, Oryzias latipes, an organelle unique to the cells of germ line, is regarded as a counterpart of nuage material in amphibians and mammals. In the study described herein, GDBs in male germ line cells were examined by electron microscopy. GDBs existed continuously in the cytoplasm of primordial germ cells (PGCs), prespermatogonia, type-A spermatogonia and early type-B spermatogonia. But they became rudimentary in late type-B spermatogonia and early spermatocytes, and no longer occurred in spermatids. Differences in the morphology of GDBs of PGCs and male germ cells were also noted. In PGCs of indifferent gonads, about 50% of GDBs were amorphous bodies of fine electron-dense fibrils, whereas in spermatogonia amorphous bodies decreased in number and GDBs of strand-like structure were more frequent. The change in the morphology of GDBs began when the sex differentiation of gonads became evident, and proceeded gradually in prespermatogonia. No obvious differences in morphology of GDBs were noted between prespermatogonia in the fry at later stages of development and spermatogonia in adult fish.