Ultrastructural changes of oocytes of mice with the advancement of age.

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Ultrastructural changes of mouse oocytes obtained from the different ages were compared. (1) In oocytes stocked in primordial follicles, microvilli and desmosomes decreased with the advancement of age of animals; materials collected were 2-day-, 20-day-, 60 to 90-day-and 360 to 390-day-old. In the oocytes of 360 to 390-day-old animals, there appeared shallow depressions of the nuclear membrane. Mitochondria were of an even size, but some of them were markedly large in the oocytes of 20-day-and 60 to 90-day-old animals. Mitochondrial cristae were lamellar or vesicular; the lamellar cristae decreased and the vesicular ones increased with the advancement of age. Golgi apparatuses, smooth-surfaced endoplasmic reticula and ribosomes tended to decrease with aging. (2) In oocytes immediately after ovulation, zonae pellucidae were homogeneous in those of 30-day-old animals, but they partly showed a feature of rough fiber-network in some oocytes of 60 to 90-day-and 180 to 210-day-old animals. Irregularly shaped mitochondria became smaller with the advancement of age, and the number of their cristae also gradually decreased. Cortical granules were few in the oocytes of 30-day-old animals, but were numerous in those after 60-day-old animals. Fibrous strands were more abundant in the oocytes of 180 to 210-day-old animals than in those of the younger ones.
日本繁殖生物学会の論文