The necessity of the germinal vesicle (GV) for the activation of MPF during porcine oocyte maturation was investigated. Porcine follicular oocytes were enucleated without damaging the oolemma, and the enucleated oocytes without culture or cultured for 30 h were examined for their protein synthesis and MPF activities. The protein synthesis pattern in enucleated oocytes changed between before and after 30 h of culture, and this change was exactly the same as that of intact oocytes between before and after GV breakdown. The MPF activity increased about 7 and 5 times after 30 h of culture in cumulus enclosed and denuded oocytes, respectively. The activation of MPF was also observed in the enucleated oocytes after 30 h of culture and the MPF activity was the same level as that of denuded oocytes. These results indicate that the presence of GV is not required for normal protein synthesis during porcine oocyte maturation and that the generally suggested nucleus-cytoplasmic interactions, cyclin B movement into GV and the mixing of karyoplasm with cytoplasm, are not required for the MPF activation.
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