Figure 1

Effects of slow freezing and vitrification on chromatin integrity of mouse embryos at the morula and blastocyst stage. Panel A: percentages of embryos graded according to chromatin damage (for details and criteria see M&M) as grade A (no damage, white segments), grade B (slight damage, gray segments) or grade C (severe damage, black segments). Embryos were grouped according to their developmental stage, observed after slow freezing/thawing or vitrification/warming and compared with controls. Numbers of analyzed embryos per group are indicated on each histogram and segment. Chi square test with the Yates correction: comparisons slow freezing vs control and vitrification vs control: *P < 0.05; **P < 0.0001; comparisons slow freezing vs vitrification: # P < 0.001; ## P < 0.0001. Panel B: Representative photomicrographs of control grade A morula (A1) and control grade A blastocyst (A2), slow frozen grade C morula (B1) and slow frozen grade C blastocyst (B2), vitrified grade B morula (C1) and vitrified grade B blastocyst (C2) are shown. The nuclei of embryos were stained with Hoechst 33258. For each embryo, UV light images are shown. Arrows indicate signs of chromatin damage: white thin arrows indicate micronuclei and white thick arrows indicate lobulated nuclei. Scale bar represents 20 μm.