Optical tweezers measurements. Quantification of elastic and viscous moduli at 10 Hz for oocytes maintained in prophase I and oocytes undergoing meiosis I. For oocytes undergoing meiosis I, the measurements were taken at NEBD + 6 h. P values were calculated with a Kolmogorov-Smirnov statistical test (P value = 0.07 for G’, the elastic modulus on the left panel, and P value = 0.02 for G’’, the viscous modulus on the right panel). n = 10 vesicles in seven oocytes in prophase I and n = 39 vesicles in 14 oocytes in meiosis I. Mean and SEM are superimposed on the raw data; three independent experiments. ns, not significant.