Subsequently, gonocytes are located in the basement membrane of seminiferous tubule and differentiate into spermatogonial
stem cells (SSCs) (de Rooij and Grootegoed, 1998; Brinster, 2002).
As regards the males, the characterization of the reproductive phases takes into account the presence and predominance (in the gonad) of: spermatogonial
proliferation and entrance into meiosis; differentiation of the gametic cells from spermatids to spermatozoa; and the release and presence of sperm in the gonoduct.
At low doses of irradiation, sertoli and Leydig cells do not show any histological changes because they are fairly radioresistant.19 At dosages above 10Gy, no morphological changes are seen in these cells, but they start to shrink.19 The differentiating spermatogonial
cells are radiosensitive while spermatocytes, spermatids and spermatozoa are relatively radioresistant.20 Non-differentiating spermatogonial
cells, also referred to as stem cells, are the most radioresistant of all spermatogenic cells.21,23 It is the division and differentiation of these surviving cells that is responsible for the repopulation of the seminiferous epithelium following exposure to radiation.23
survival after grafting human testicular tissue to immunodeficient mice.
In group C at 133d of age lumen of the seminiferous tubules were lined only with spermatogonial
cells and spermatocytes.
The study at the Georgetown University Medical Center (GUMC) is a proof of principle that human spermatogonial
stem cells (SSCs) extracted from testicular tissue can morph into insulin-secreting beta islet cells normally found in the pancreas.
Spermatogenic arrest can occur at spermatogonial
level in case of gonadotropin insufficiency or after germ cell damage due to chemotherapy or radiotherapy.
In the same experiment he also determined the timing of meiotic and spermatogonial
events at 30[degrees]C, concluding that spermatocytes take approximately 12 d to progress from the premeiotic period of DOA synthesis (S-phase) to metaphase I.
Proteins unique to the testis include histone H1, H2B-1, and H2B-2, which are produced in mitotically active spermatogonial
cells (Poccia et al., 1989); and bindin, which is produced by late spermatocytes and early spermatids (Cameron et al., 1990).
elegans germline stem cell region, giving immunohistological techniques for study, describing how to use genetic tools to trace cell lineage and gene manipulation, determining the structured polarity of male germline stem cells, conducting high-resolution light microscopic characterization of spermatogonia, identifying and characterizing spermatogonial
subtypes, attaining epigenetic control in male germ cells and maintaining spermatogonial
germ cells in vivo and in vitro.
mitosis, after C-banding, sex chromosomes have shown two different patterns.