Protrusion, contraction and segregation of membrane components associated with passive deformation and shape recovery of Walker carcinosarcoma cells.

We mimicked essential elements of the cortical-contraction model of cell locomotion by exposing Walker carcinosarcoma cells to passive deformation and to hydrostatic pressure changes within micropipettes followed by shape recovery after release. Protrusion, contraction and segregation of cell surface membrane components were observed. Regardless of the initial shape (spherical, polarized with lamellipodia or blebs) cells tended to produce blebs during uptake into the pipette and during and after release from the pipette, but usually not during the short time they were held within the pipette. Bleb formation depended on the deformation stress, extracellular hydrostatic pressure and cell structure (initial shape). In polarized cells, blebs were much more readily induced at the front as compared to the tail. Cells undergoing large deformations formed constriction rings and large hyaline caps. Deformation resulted in segregation of membrane components. Equatorial constriction rings divided the cell into two parts which differed with respect to Con A binding and their role in shape recovery. Spherical and polarized cells usually recover the respective initial shape. Polarized cells reacquired the same type of protrusions (blebs or lamellipodia) which they exhibited before deformation. Shape recovery of spherical cells was characterized by a rapid recoil by about 20% followed by a slow asymptotic recovery.