Demonstration of maturation-promoting and- inhibiting activities in mouse oocytes

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Abstract
The microinjection of cytoplasm from mature mouse oocytes into immature mouse oocytes induced the resumption of meiosis in the presence of 100 μg/ml dibutyryl cyclic AMP or 100 μM 3-isobutyl-1-methylxanthine. The volume of cytoplasm injected was critical to bringing about this maturation-promoting activity in mouse oocytes, and 20 pl of cytoplasm seems to be required to overcome the inhibitory effect of cyclic AMP on oocyte maturation. Furthermore, it was demonstrated that the microinjection of cytoplasm from immature mouse oocytes into immature mouse oocytes augmented the inhibitory effect of cyclic AMP on the resumption of meiosis. These results suggest that the appearance and disappearance of maturation-promoting and- inhibiting activities appear to be dependent on the meiotic stages in the mouse oocytes.