Fig. 6. Inhibition of the PI 3-kinase activity does not affect the formation of multivesicular endosomes. (A) Dictyostelium cells treated with LY for 30 minutes were incubated in HL5 medium containing LY and fluorescent dextran and the uptake of fluorescent dextran was measured by flow cytometry. The mean and standard deviation of three experiments are indicated. (B-D) Dictyostelium cells cultured in HL5 medium were pretreated with 30 µM/ml of LY for 30 minutes (B), then incubated in the presence of LY and U18 for 15 minutes (C) or 30 minutes (D). Each sample was then fixed and processed for electron microscopy. Bars, 0.5 µm.