ハムスター卵子の多精における雄性前核の形成

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Mature unfertilized eggs of the golden hamster (Mesocricetus auratus) were freed from zonae pellucidae and inseminated in vitro with capacitated and acrosomereacted spermatozoa. The media used were BWW medium and modified Tyrode's solution (Table 1). Between 3-4 hours after insemination, the eggs were examined with a phasecontrast microscope for developmental stages (cf. Figs. 1-8) of male pronuclei. Results showed that all the sperm heads transformed into well developed pronuclei (stages IV and beyond) when 1 or 2 spermatozoa penetrated one egg. When increasing numbers of spermatozoa penetrated an egg, the number of eggs in which all the sperm heads transformed into well-developed pronuclei decreased (Table 3). Five spermatozoa per egg appeared to be the limit for all the sperm heads to transform into well-developed pronuclei. The vast majority of sperm heads failed to transform into well-developed pronuclei when more than 8 spermatozoa penetrated an egg (Table 2). There appeared to be no limit to the number of sperm heads capable of decondensing after their entry into the egg cytoplasm (we observed one egg with 56 decondensing sperm heads). Extensive polyspermy, however, generally resulted in deterioration of the cytoyplasm as evidenced by the appearance of many vacuoles. We commonly observed well-developed female pronuclei in heavily polyspermic eggs in which all the sperm heads were arrested at very early stages (stages I and II) of pronuclear development. These results seem to indicate that (1) the egg cytoplasmic factor controlling the development of the female pronucleus is not identical to that regulating the development of the male pronucleus, (2) the factor inducing decondensation of the sperm head is different from the factor responsible for transforming the decondensed head into a male pronucleus, and (3) an apparent competition occurs among sperm nuclei for materials responsible for male pronuclear development ("formative materials") when many sperm heads are incorpoarted into the egg cytoplasm.
社団法人日本動物学会の論文
1979-03-25

ハムスター卵子の多精における雄性前核の形成

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