Mechanical changes of living oocytes at maturation investigated by multiple particle tracking

We have studied the mechanical properties of the cytoplasm of starfish oocytes before and after maturation using the multiple particle tracking technique. Fluorescent microbeads are microinjected in oocytes of Astropecten aranciacus starfishes. Mechanical properties are obtained analyzing the mean-square displacement (MSD) of the beads trajectories. The ensemble-averaged MSD provides information about diffusion coefficient D, and the cytoplasm viscosity is estimated through the Stokes-Einstein equation. Results show that maturation ? is correlated with change of cytoplasm viscosity. The results can be ascribed to F-actin reorganization as also supported by fluorescence confocal microscopy. © 2009 American Institute of Physics.