Fig. 3. Depolymerization of actin does not inhibit BFA-induced changes in vimentin networks. SW13 v+ cells were treated in either the absence or presence of 10 µg/ml BFA for 30 minutes, 1 µg/ml cytochalasin D for 45 minutes, or pretreated with 1 µg/ml cytochalasin D for 15 minutes followed by the addition of 10 µg/ml BFA for 30 minutes in the continued presence of cytochalasin D at 37°C. Cells were processed and stained with monoclonal antibodies directed against either vimentin, -tubulin, or ß-actin and visualized by epifluorescence microscopy. Cytochalasin D treatment induced actin depolymerization as shown by ß-actin staining. In addition, it also generated retraction of both microtubule and vimentin networks. However, cells treated with both BFA and cytochalasin D exhibited process-like formations of both vimentin and microtubules, indicating that actin was not required for the effects of BFA on vimentin and microtubule networks. Bar, 20 µm.