The first polar body does not predict accurately the location of the metaphase II meiotic spindle in mammalian oocytes

OBJECTIVE: To evaluate how well polar body location predicts spindle localization and to examine spindle morphology. DESIGN: Randomized, controlled animal study. SETTING: University-affiliated research laboratory. ANIMAL(S): Mature, female golden hamsters. INTERVENTION(S): After superovulation with pregnant mare serum gonadotropin and hCG, metaphase II oocytes were obtained and imaged under digital polarization microscopy. MAIN OUTCOME MEASURE(S): Identify the meiotic spindle in living, unfixed hamster oocytes and determine spindle location relative to the polar body. RESULT(S): Spindles were imaged in 30 oocytes and only in 5 of them could the polar body predict the spindle localization. In the remaining oocytes, the spindles presented a random distribution within the cytoplasm. CONCLUSION(S): These data show that the polar body location is not an accurate predictor for meiotic spindle location in mammalian oocytes.