CRYOPRESERVATION OF MOUSE OOCYTES - MUTAGENIC EFFECTS IN THE EMBRYO

We have shown in previous studies that the complete cycle of cryoprese rvation and prefreezing manipulations increases the degeneration and d ecreases the fecundability of mouse oocytes. The present study confirm s these results. Moreover, we show that the increase of polyploidy pre viously observed in one-cell zygotes derived from frozen-thawed oocyte s persists during the early stages of embryonic development. Furthermo re, embryos obtained from frozen oocytes or oocytes exposed to prefree zing manipulations show an increase in the frequency of sister chromat id exchanges. Since the estimation of sister chromatid exchange is a s ensitive test of mutagenicity, this suggests that the complete cycle o f cryopreservation might alter the oocyte and, more particularly, indu ce DNA damage.