Abstract
Using immunohistochemical techniques, the localization of maturation promoting factor (MPF) and MAP kinase around chromosomes of cumulus nuclei transferred into the porcine mature oocytes was investigated. Nuclear condensation was observed in most of the transferred nuclei within 2 h and was maintained until 6 h after nuclear injection. Cyclin B, a subunit of MPF, and MAP kinase accumulated around the exogenous chromosomes in 47% of the injected oocytes at 6 h after injection. Tubulin assembly around the exogenous chromosomes was detected only in those accumulated by cyclin B and MAP kinase. The pronuclear formation rate after oocyte activation agreed well with the tubulin assembly rate. The present results indicate for the first time that MPF and MAP kinase accumulated around exogenous chromosomes in porcine mature oocytes and suggest that their accumulation correlates with tubulin assembly and pronuclear formation.
