Collection and viability identification of the PB1s.
A: PB1 with intact membrane was packed into an empty zona pellucida using a fine glass needle. B: An empty zona pellucida. C: The viability of the PB1s was evaluated by propidium iodide (red, dead) and Hoechst 33342 (blue, both living and dead) staining. D: Percentages of PB1 at various times after being packed into empty zona pellucida. G1 and G2 stand for Grade 1 and Grade 2 PB1s, respectively.