[Active region of the lamellar cytoplasm and focal contacts--the most cytochalasin-sensitive structures of fibroblasts].

Effects of low doses of cytochalasin B (CB, 2 micrograms/ml) and cytochalasin D (CD, 0.2 microgram/ml) on the spreading of normal mouse fibroblasts in culture were investigated. CB desorganized the cortical layer of actin microfilaments to cause partial or complete disappearance of microfilament bundles; focal contacts with the substrate seen by interference-reflection microscopy also disappeared.

Active cell edge and movements of concanavalin A receptors of the surface of epithelial and fibroblastic cells.

Movements of the receptors of concanavalin A on various parts of the surfaces of substrate-attached cells were compared. Cultured mouse embryo cells of several types were used: epithelial kidney cells and normal and transformed fibroblasts. Initial distribution of receptors was random on the cells of all types.