Involvement of microfilaments in filopodial function of phagocytic granular cells of the silkworm, Bombyx mori.

The effects of colchicine, vinblastine, and cytochalasin B (CB) on both attachment and filopodial function of phagocytic granular cells of Bombyx mori were studied using the scanning electron microscopy (SEM). Incubation of cells with colchicine or vinblastine had only a little effect on attachment and filopodial function. CB, on the other hand, caused a marked inhibition of filopodia elongation and thus inhibited attachment. The effects of all drugs were dose-dependent. Colchicine and vinblastine did not affect filopodia contractility. Treatment of cells with CB, however, caused retraction of once-elongated filopodia. The inhibitory effect of CB on elongation was reversible with treatment of hemolymph. The results strongly suggest that cytochalasin-sensitive structures, most likely microfilaments, are involved in filopodial function and that hemolymph will be of great importance in the activation of microfilament system.