[Cultivation of mouse oocytes in vitro: the ability to resume meiosis].
It is well established that fully grown oocytes from sexually mature mice are capable of resuming meiosis when cultured in vitro. However it has not been established at what stage during the growth the oocyte acquires the ability to mature. The present study was undertaken to determine the precise stage of growth at which the ability to resume meiosis is acquired in ICR strain mice. Oocytes of various sizes were isolated from the ovary by mechanical dissection. This method yielded about 30% growing and fully-grown oocytes from the ovary. Cumulus-free oocytes dissociated from the ovaries of 5-week-old mice were cultured in vitro in a chemically defined medium for 3 hr. None of the 61- to 65-microns-diameter oocytes resumed meiosis; however 81.8% of the 66- to 70-microns-diameter oocytes were able to resume meiosis. Fifty- to 60-microns-diameter oocytes recovered by enzymatic dispersal of the basement membrane of isolated growing follicles were unable to resume meiosis. Follicle-enclosed 50- to 60-microns-diameter oocytes did not resume meiosis even when cultured in a medium containing Ca-ionophore A 23187 or 8-bromoadenosine 3', 5'-cyclic monophosphate which are known to induce resumption of meiosis of oocytes in Graafian follicles. These results indicate that the ability to resume meiosis is acquired dramatically at a specific stage of oocyte growth.
Department of Animal Science, Faculty of Agriculture, Kyoto University, Japan.
E
E
Sato
Y
Y
Miyamoto
D000818:Animals; D003470:Culture Media; D005260:Female; D006107:Granulosa Cells / Q000648:ultrastructure; D066298:In Vitro Techniques; D008540:Meiosis; D051379:Mice; D008813:Mice, Inbred ICR; D009865:Oocytes / Q000166:cytology*
D003470:Culture Media