Structure of interlacing bundles of F-actin in Sf9 cells and of isolated hairlike projections. (a) Structure of cytoplasmic bundles in Sf9 cell after staining with 2% uranyl acetate. This representative micrograph shows the complexity of bundle interdigitation. Ends of bundles can be observed to splay out into their individual component filaments at many points (arrowheads). (b and c) Structure of hairlike projections. Hairs were separated from intact cells by mechanical agitation and centrifugation. Hairs are bound by membrane and are cored by organized filament bundles (arrowhead). Bundles abruptly end near the tips of projections (b). The bars are 100 nm.