Ovum morphology after hyperthermic stress during meiotic maturation and ovulation in the mouse

Eggs were collected from 60 virgin ICR mice 15 1/2 h after synchronization of ovulation with PMSG and hCG from control females and those exposed for 15 1/2 h to hyperthermic conditions (35 +/- 1 degrees C, 65 +/- 3% relative humidity) immediately after the hCG injection. Eggs were classified for analysis as monocellular, bicellular, tricellular equal, tricellular, unequal, multicellular and degenerate. Egg class frequencies were affected by increasing atypical forms (P < 0.01). Stressed animals had significantly larger cells when an analysis of variance was performed on the bicellular classification, but there was no effect on ovum diameter.