Biomedical subjects

Gladys Massiera

Publications and source records attributed to Gladys Massiera.

4 recordsLinked to original sources

PubMed2006

The role of F-actin and myosin in epithelial cell rheology.

Although actin and myosin are important contributors to cell-force generation, shape change, and motility, their contributions to cell stiffness and frequency-dependent rheology have not been conclusively determined. We apply several pharmacological interventions to cultured epithelial cells to elucidate the roles of actin and myosin in the mechanical response of cells and intracellular fluctuations. A suite of different methods is used to separately examine the mechanics of the deep cell interior and cortex, in response to depletion of intracellular ATP, depolymerization of F-actin, and inhibition of myosin II. Comparison of these results shows that F-actin plays a significant role in the mechanics of the cortical region of epithelial cells, but its disruption has no discernable effect on the rheology of the deeper interior. Moreover, we find that myosins do not contribute significantly to the rheology or ATP-dependent, non-Brownian motion in the cell interior. Finally, we investigate the broad distribution of apparent stiffness values reported by some microrheology methods, which are not observed with two-point microrheology. Based on our findings and a simple model, we conclude that heterogeneity of the tracer-cytoskeleton contacts, rather than the network itself, can explain the broad distribution of apparent stiffnesses.

Actins↗

PubMed2006

The consensus mechanics of cultured mammalian cells.

Although understanding cells' responses to mechanical stimuli is seen as increasingly important for understanding cell biology, how to best measure, interpret, and model cells' mechanical properties remains unclear. We determine the frequency-dependent shear modulus of cultured mammalian cells by using four different methods, both unique and well established. This approach clarifies the effects of cytoskeletal heterogeneity, ATP-dependent processes, and cell regional variations on the interpretation of such measurements. Our results clearly indicate two qualitatively similar, but distinct, mechanical responses, corresponding to the cortical and intracellular networks, each having an unusual, weak power-law form at low frequency. The two frequency-dependent responses we observe are remarkably similar to those reported for a variety of cultured mammalian cells measured with different techniques, suggesting it is a useful consensus description. Finally, we discuss possible physical explanations for the observed mechanical response.

Adenosine Triphosphate↗

PubMed2005

Bounded step superdiffusion in an oriented hexagonal phase.

Fluorescence recovery after pattern photobleaching is used to measure the self-diffusion of surfactant molecules, along cylinders and perpendicular to their main axis in an oriented hexagonal lyotropic phase. Unexpectedly, while the motion along cylinders is diffusive, a superdiffusive behavior is observed in the direction perpendicular to the cylinder axis. Moreover, varying the lattice parameter, we found that the perpendicular diffusion time is governed only by the number of cylinders to cross, providing experimental evidence for superdiffusion with a bounded step length.

Journal Article↗

PubMed2003

Structure factor of polymers interacting via a short range repulsive potential: application to hairy wormlike micelles.

We use the random phase approximation to compute the structure factor S(q) of a solution of chains interacting through a soft and short range repulsive potential V. Above a threshold polymer concentration, whose magnitude is essentially controlled by the range of the potential, S(q) exhibits a peak whose position depends on the concentration. We take advantage of the close analogy between polymers and wormlike micelles and apply our model, using a Gaussian function for V, to quantitatively analyze experimental small angle neutron scattering profiles of solutions of hairy wormlike micelles. These samples, which consist in surfactant self-assembled flexible cylinders decorated by amphiphilic copolymer, provide indeed an appropriate experimental model system to study the structure of sterically interacting polymer solutions.

Journal Article↗