Immunofluorescent visualization of 100 A filaments in different cultured chick embryo cell types.

Antibody prepared against the 55,000 dalton subunit of reconstituted chick gizzard 100 A filaments (anti-G55K) bound to the 100 A filaments of chick smooth muscle, cardiac muscle, and skeletal muscle cells, and to the 100 A filaments of Schwann cells and satellite glial cells of the peripheral nervous system. Anti-G55K did not bind to replicating presumptive myoblasts, fibroblasts, chondroblasts, pigment cells, neurons, or to central nervous system glial cells. This contrasted with the wider range of binding of antibody to the 58,000 dalton subunit of chick fibroblast 100 A filaments (anti-F58K) which bound to the 100 A filaments of all cell types examined except hepatocytes and skin epithelial cells. Anti-G55K) staining revealed a morphologically distinct distribution of 100 A filaments in the three types of muscle cells. Spindle shaped smooth muscle cells exhibited dense fluorescent staining near the poles of the cells, and also exhibited unique patches of fluorescent material after cytochalasin B and Colcemid treatment. In myotubes, the fluorescence was limited to longitudinal bundles of filaments between the striated myofibrils. Cardiac cells contained uniformly distributed fine filaments. Lastly, smooth muscle cells in various phases of mitosis bound the anti-G55K, whereas replicating presumptive skeletal myoblasts failed to bind the anti-G55K.