Rearrangement of Tonofilament-like Intermediate Filaments in the Spreading Proc ss of JTC-12 Cells as Studied by Microscopy, Electron

Tonofilament-like intermediate filaments measuring 60-90 Å in diameter were observed in the cytoplasm of the epithelial cell JTC-12, a cell line derived from the kidney of a healthy monkey. In flattened cells, the filaments were in compact bundles which traversed the cytoplasm in parallel to the substratum, and the bundles branched and interconnected at places. In suspended spherical cells after trypsinization, free filaments or short strands of bundles were scattered throughout the cytoplasm in random orientation. In the spreading process, the arrangement of the filaments was restored to order. The growth of bundles occurred by addition of free filaments and by fusion of thinner and shorter bundles. In view of its reorganization and developmental pattern, the 60-90 Å filament system was suggested as playing a role in maintaining the flattened cell Shape.