Influence of postovulatory aging on chromosome segregation during the second meiotic division in mouse oocytes: a...

A high incidence of parthenogenetic activation was observed when postovulatory aged mouse oocytes were exposed briefly to hyaluronidase in culture medium at 18-26 h after the human chorionic gonadotropin injection for inducing superovulation. The majority of the activated oocytes extruded a second polar body and developed a single haploid pronucleus. Cytogenetic analysis of this class of parthenogenone at metaphase of the first-cleavage mitosis has clearly demonstrated that the completion of the second meiotic division in activated aged oocytes is not associated with a significant increase in the incidence of chromosome segregation errors. The increasing postovulatory age of oocytes prior to activation was observed to significantly decrease the capacity of activated oocytes to extrude the second polar body.