Fig. 8. ROCK inhibitor Y27632 blocks proliferation but not MRF expression. (A) Asynchronous myoblasts were treated with control medium (a-c, g-i) or 10 µM Y27632 (d-f, j-l) for 24 hours. Oregon Green-phalloidin staining reveals a distinct morphology in Y27632-treated cells (d) marked by elongated processes (compare to control in a). Pulse labeling with BrdU is inhibited by ROCK inhibitor (compare e with b); (c,f) phase contrast + DNA stain of the same fields as in b and e, respectively. MyoD (j) and myogenin (k) staining are undiminished in Y27632-treated cells compared to control cells (g) and (h) respectively, (i,l) phase contrast + DNA stain of the same fields as in g,h and j,k, respectively. Scale bar: 25 µm.