Fig. 9. Effects of actinomycin D and okadaic acid on S1 fiber formation. (A) ARL cells grown to 65% confluency were incubated in the presence of actinomycin D (5 µg/ml) for up to 9 hours and immunostained with McAb 351. (B) ARL cells cultured for 2 weeks at full confluency were treated with 50 nM okadaic acid (+OA) for 3 hours, and immunostained with McAb 351. Arrowheads indicate S1 fibers. Bar, 25 µm.