کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
5586547 1568636 2017 24 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Prespermatogenesis and early spermatogenesis in frogs
موضوعات مرتبط
علوم زیستی و بیوفناوری علوم کشاورزی و بیولوژیک علوم دامی و جانورشناسی
پیش نمایش صفحه اول مقاله
Prespermatogenesis and early spermatogenesis in frogs
چکیده انگلیسی
Spermatogenesis in frogs was for the first time divided into two phases: prespermatogenesis, when gonocytes proliferate in developing tadpole testes, and active spermatogenesis when spermatogonial stem cells (i.e. descendants of gonocytes), either self-renew or enter into meiotic cycles within cysts formed by Sertoli cells. We argue that amphibian larval gonocytes are homologues to mammalian gonocytes, whereas spermatogonial stem cells (SSCs) in adult frogs are homologous to mammalian single spermatogonia (As). Gonocytes constitute sex cords, i.e. the precursors of seminiferous tubules; they are bigger than SSCs and differ in morphology and ultrastructure. The nuclear envelope in gonocytes formed deep finger-like invaginations absent in SSCs. All stages of male germ cells contained lipid droplets, which were surrounded by glycogen in SSCs, but not in gonocytes. Mitochondria in gonocytes had enlarged edges of cristae, and in SSCs also lamellar mitochondria appeared. Minimal duration of prespermatogenesis was 46 days after gonadal sex differentiation, but usually it lasted longer. SSCs give rise to secondary spermatogonia (equal to mammalian A, In, and B). Their lowest number inside a cyst was eight and this indicated the minimal number of cell cycles (three) of secondary spermatogonia necessary to enter meiosis. We sorted them according to the number of cell cycles (from 8 to 256 cells). This number is similar to that recorded for mammals as the result of a single As proliferation. The number of secondary spermatogonia correlates with the volume of a cyst. The general conclusion is that spermatogenesis in amphibians and mammals follows basically the same scheme.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Zoology - Volume 122, June 2017, Pages 63-79
نویسندگان
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