title: High- and low-frequency mechanical properties of living starfish oocytes.
abstract: We studied the mechanical properties of living starfish oocytes belonging to two species, Astropecten Auranciacus and Asterina pectinifera, over a wide range of timescales. We monitored the Brownian motion of microspheres injected in the cytoplasm using laser particle-tracking (LPT) and video multiple-particle-tracking (MPT) techniques, to explore high- and low-frequency response ranges, respectively. The analysis of the mean-square-displacements (MSD) allowed us to characterize the samples on different timescales. The MSD behavior is explained by three power-law exponents: for short times (τ < 1 ms) it reflects the semiflexible behavior of the actin network; for intermediate timescales (1 ms < τ < 1 s) it is similar to that of a soft-glass material; finally for long times (τ > 1 s) it behaves mainly like a viscous medium. We computed and compared the viscoelastic moduli using a recently proposed model describing the frequency response of the cell material. The large fluctuations found in the MSD over hundreds of trajectories indicate and confirm the significant cytoplasm heterogeneity.
authors: Dipartimento Scienze Fisiche Universitá di Napoli Federico II, Complesso Universitario Monte S. Angelo, via Cintia 80126 Napoli, Italy. giuseppe.pesce@na.infn.it
authors: Giuseppe
authors: G
authors: Pesce
authors: Lara
authors: L
authors: Selvaggi
authors: Giulia
authors: G
authors: Rusciano
authors: Antonio
authors: A
authors: Sasso
mesh_terms: D000818:Animals; D047288:Asterina / Q000166:cytology* / Q000502:physiology; D001696:Biomechanical Phenomena; D055119:Elastic Modulus; D007834:Lasers; D055595:Mechanical Phenomena; D009865:Oocytes; D012212:Rheology; D013045:Species Specificity; D013997:Time Factors; D014783:Viscosity