Demonstration of the significance of isometric contraction for the formation of stress fibres in chick embryo fibroblasts.

Observations of the cytoskeleton visualized with Coomassie brilliant blue R250 were carried out on chick embryo fibroblasts emigrating from cell aggregates onto clean or siliconized cover glasses. Conditions for persistent isometric contraction were created in cells attached strongly to glass and to the aggregate. These cells showed a presence of abundant stress fibres in their cytoplasm. Upon induction of lamellipodia retraction, the stress fibres transformed into typical retraction fibres. In cells spreading onto siliconized glass, the fibres were rare. Upon cell contraction their lamellipodia detached, folded and fibres, if originally present, disintegrated. These observations extend the conclusions of Wohlfarth-Bottermann to tissue culture cells, formulated on the basis of extensive study on the structure and behaviour of cytoplasmic fibrils in slime mold plasmodia, that bundles of parallely oriented actomyosin filaments arrange as a result of the persistent isometric contraction of cytoplasm. The present result point out the significance of cell surface adhesive properties for the organization of cell cytoskeleton.