PJ-34 did not eradicate mouse embryonic fibroblasts. (a) The effect of PJ-34 on mouse embryonic fibroblasts (MEF) was measured after repeated applications of PJ-34 (10 μM) 24 hours and 72 hours after seeding, as indicated. MEF, untreated and incubated with PJ-34 (10 μM) for 48 hours, and MEF, untreated and incubated with 20 μM PJ-34 for 100 hours are shown. On the right are displayed cell counts (0.02 to 0.03 mm2 per field) of cells incubated with PJ-34 (10 μM, after the first application, and 20 μM, after the second application) for the indicated time periods. Each value is an average value of cells counted in five different experiments. (b) MEFs were analyzed with flow cytometry at the indicated periods after addition of PJ-34. A transient G2/M transition arrest is indicated in MEFs incubated for 6 hours with PJ-34 (10 μM). Control: Untreated MEFs 48 hours after seeding. Similar results were obtained in three different experiments.