Different cytoskeletal domains in murine fibroblasts.

The morphology of the cytoskeleton of normal 3T3 fibroblasts was studied in the electron microscope on embedded and sectioned cells as well as on critical-point-dried whole mounts. Four ultrastructurally different cytoplasmic domains could be distinguished within every 3T3 cell, namely: Cytocortex, ruffle area, endoplasm, and stress fibre. However, many transitions between the different domains were also found. In addition, 2 other domains were occasionally encountered in the same cells. Based on the knowledge that actin is present in relatively high concentration throughout non-muscle cells and that it can, under different physiological conditions, assume different morphological appearances, an attempt has been made to formulate a hypothesis that links the ultrastructural domains to different cellular functions. Many experimental approaches are available to test the hypothesis and at the same time increase our knowledge of the cytoskeleton of 3T3 cells.