Effects of cytochalasin B on cell division and vacuole formation in Tetrahymena pyriformis GL

Cytochalasin-B (Cyt-B) was tested for its effect on cell division and vacuole formation in Tetrahymena. Little effect was found on cell division in the synchronous cell system in concentrations up to 37 μg/ml; however, slight delay was caused by 71 μg/ml. As measured by particle uptake, much lower concentrations, 7–8 μg/ml, caused significant inhibition of vacuole formation in exponentially multiplying and in starved cells, 16.6 or 37 μg/ml caused strong inhibition. This effect was immediate and completely reversible. The presence of Cyt-B caused starvation of Tetrahymena. The essential absence of inhibition of cell division by Cyt-B may reflect that the drug can enter the cell only by way of vacuoles.