Three dimensional fine structure of cultured cells: possible implications for subcellular motility

To determine the three dimensional fine structure of whole motile cells, rat embryo cells, cultured on Formvar-coated cover-glasses, were glutaraldehyde/osmium-fixed, mounted on grids, dehydrated, critical point dried and examined by transmission electron microscopy using stereoscopic techniques. Three dimensional arrays of organelles occurred in a filament-rich cytoplasmic matrix. Here, besides microtubules and elongate filaments, inter-connected filaments formed a widespread fine-mesh space network which attached to the plasma membrane and closely surrounded all organelles. Negative staining revealed a similar newtork in unfixed cells. It is concluded that this network represents part of the force-generating mechanism for various subcellular movements.