Relation between cell activity and the distribution of cytoplasmic actin and myosin.

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Abstract
The activity of cultured cells were documented on time-lapse videotapes and then these identified cells were stained with antibodies to actin and myosin. This experimental approach enabled the direct correlation of cellular activity with the distribution of cytoplasmic actin and myosin. When trypsinized HeLa [human cervical carcinoma] cells spread onto a glass surface, the cortical cytoplasm was the most actively motile and random, bleb-like extensions (0.5-4.0 .mu.m wide, 2-5 .mu.m long) occurred over the entire surface until the cells started to spread. During spreading, ruffling membranes were found at the cell perimeter. The actin staining was found alone in the surface blebs and ruffles, and together with myosin staining in the cortical cytoplasm at the bases of the blebs and ruffles. In well-spread, stationary HeLa cells most of the actin and myosin was found in stress fibers but there was also diffuse antiactin fluorescence in areas of motile cytoplasm, such as leading lamellae and ruffling membranes. All 22 of the rapidly translocating embryonic chick cells had only diffuse actin staining. Between these extremes were slow-moving HeLa cells, which had combinations of diffuse and fibrous antiactin and antimyosin staining. Apparently large actomyosin filament bundles are associated with nonmotile cytoplasm, and actively motile cytoplasm has a more diffuse distribution of these proteins.