Fig. 6. CHO cells progress through the continuous cell cycle in the absence of actin stress fibers and cell spreading. (A) Phosphorylation of p42/p44 MAPK and (Y397) FAK, as well as expression levels of cyclins D1/D2 and cyclin E were determined by western blotting in mitotic and post-mitotic CHO cells treated with or without CCD (FAK=loading control). (B) DNA synthesis was examined in synchronized CHO cells incubated over night with actin inhibitors and 10 µM BrdU. Values shown represent the average percentages ± s.e.m. obtained from three independent experiments. (C) [³H]thymidine incorporation was assessed in CHO cells progressing from mitosis into S phase in the presence or absence of CCD or LB (untreated=closed squares, LB=open squares, CCD=triangles). A representative experiment is shown; data are expressed as means ± s.e.m. (n=3). (D) CHO cells were incubated with the actin inhibitors through one continuous cell cycle (25 hours), washed and allowed to recover for 3 hours in fresh medium prior to staining with phalloidin and DAPI. Bar, 20 µm. (E) Mono- and bi-nucleated cells were scored in random fields counting 300 cells in each individual experiment. Depicted are the average percentages ± s.e.m. (n=3).