Figure 3

PUC colonies express alkaline phosphatase. Colony-forming PUC cell isolates stained for the presence of alkaline phosphatase. Staining was most intense in the colonies (A, C and D). Addition of 3–5 μM levamisole to the solution inhibited the staining (B). Usually, a small number of positive individual cells was also stained (arrows in C and D). Results are typical of 11 separate experiments. Bars = 500 μM (A and B), 200 μM (C and D).