Figure 1.

Hypotheses regarding cryoinjuries in mammalian oocytes. (a) Premature cortical granule exocytosis causes the hardening of zona pellucida, leading to block of sperm penetration. (b) Disorganization of microtubules means depolymerization of tubulin proteins, leading to misassembly of meiotic spindles, and subsequently resulting in misalignment of chromosomes and inhibition of the second polar body extrusion. (c) Multiple aster formation, resulting from ooplasmic dysfunction to support MTOC, is a possible cause of low blastocyst yield.