Fig. 1.

Intracellular free calcium ([Ca²⁺]i) oscillation patterns after parthenogenetic activation in oocytes collected at different times post-human chorionic gonadotropin (hCG) injection. a, b [Ca²⁺]i oscillation patterns at 13-21-h post-hCG. c Relative [Ca²⁺]i oscillation parameters including “frequency,” “cycle,” “maintain,” “move,” “peak,” and “Δpeak” for statistical analyses; each ratio of different groups was compared with the 17-h group. d Rates of pronucleus (PN) formation of oocytes collected at different post-hCG time points after parthenogenetic activation. N = 25 to 30 for each group. Data represent mean ± SD, and chi-square test and one-way ANOVA are used for statistical analysis. *P < 0.05 versus the 17-h group