| Summary: | 碩士 === 國防醫學院 === 生物及解剖學研究所 === 85 === Apoptosis and necrosis are two major modes of cell death. Apoptosis is characterized by chromatin condensation, apoptotic body, and DNA fragmentation. Apoptosis is one of the major mechanisms in embryonic development. In addition, it may be induced by a variety of factors, for example, free radicals, growth factors deprivation and irradiation. Several proto-oncogenes including p53, bcl-2 and bax are shown involved in regulating apoptosis induced by these factors. However, roles of these genes are not consistent in various types of cells. Therefore, it is interesting to verify if the pathway and mechanism are common in apoptosis induced by various factors. Recent studies reported germ cell death in prenatal, postnatal and adult testes. In order to elucidate the possible mechanism of apoptosis in development, this thesis investigated the mode and mechanism of germ cell death in postnatal mice. Electron microscopic observation revealed distinct ultrastructures of germ cells and Sertoli cells. Germ cells were larger cells with light electron dense, ovoid nucleus with euchromatin and larger mitochondria with membranous cristae. Sertoli cells were smaller cells with darker electron dense, irregular nucleus with heterochromatin, smaller mitochondria with tubular cristae. Desmosome-like junctions were found between Sertoli cells, and between Sertoli cells and germ cells 2 days after birth. Tight junctions were present between Sertoli cells 3 days after birth. Immunofluorescent staining exhibited E-cadherin on germ cells, and P-cadherin on Sertoli cells. Chromatin condensation of germ cells were found since 1 days after birth, and apoptotic bodies in Sertoli cells 2 and 4 days after birth. However, TUNEL staining revealed apoptosis in tess than 1% of germ cells. These results indicated that cell junctions of germ cells and Sertoli cells were established since the first of life, and germ cell death or apoptosis was not common in postnatal ICR male mice.
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