[Influence of postovulatory ageing on balanced predivision of sister chromatid in mouse oocytes].

Objective: To study the impact of postovulatory ageing to balanced predivision of oocyte sister chromatid.

Methods: The mouse oocytes were cultured 0-72 h. Then chromosome 16 was detected by fluorescence in situ hybridization (FISH). The oocyte spindle and chromosome configuration were examined by immunocytochemistry.

Results: For freshly ovulated mouse oocyte, the balanced predivision of sister chromatid occurred only at 7%. However, for oocytes cultured for 24 h, 48 h and 72 h in vitro, the balanced predivision of sister chromatid occurred up to at 32%, 51% or 62% respectively (P< 0.01). The abnormal cell spindle and chromosome configuration occurred at 9% of freshly ovulated oocytes, but it increased to 63%, 83% and 98% when the oocytes were cultured in vitro for 24 h, 48 h or 72 h respectively (P< 0.01).

Conclusion: The occurrence of balanced predivision of oocyte sister chromatid may result during postovulatory ageing, and may be related to change of oocyte spindle and chromosome configuration.