Fast cell membrane displacements in B lymphocytes Modulation by dihydrocytochalasin B and colchicine

A novel type of cell membrane movement was characterized in B lymphocytes. Local submicron cell membrane displacements, within the frequency range 0.3-15 Hz, were registered in a murine lymphoma B cell line by a novel optical method based on point dark field microscopy. The cell membrane displacements were measured by monitoring changes in light scattering from very small illuminated areas (0.25 μm²) at the edge of the cell surface. B lymphocytes manifest a relative change in light scattering of 7.7 ± 1.3% (mean ± SD) which corresponds to cell membrane transverse displacement of 131 ± 22 nm. The confinement of cell membrane displacements to microdomains (≤0.2 μm²) emerged from the observed dependence of the displacement amplitude on the area size from which it is monitored. Colchicine (1 μM) decreased membrane fluctuations down to a value of 88 ± 14 nm, whereas dihydrocytochalasin B (2 μM) increased the amplitude of membrane displacements up to 184 ± 31 nm. These findings demonstrate the existence of a dynamic mechanical interaction between the cytoskeleton and the cell membrane in the frequency range of 0.3-15 Hz. The modulation of these interactions by the disruption of microfilaments or microtubules is explained in terms of the induced strain changes imposed on the cell membrane.