Fig. 6. Inhibition of p38 signaling rapidly alters morphology of myoblasts. SB202190-treated and untreated PLM cultures were fixed and analyzed for MyHc expression at various times over 24 hours. In control cultures, at all times examined, MyHc-positive cells are only slightly bipolar, with small cellular extensions, are randomly oriented and are distributed throughout the culture. Within only a few hours of SB202190 addition, these cells acquire an enhanced bipolarity, with the bipolar cellular extensions oriented in the same direction. These bipolar cells are also in very close proximity to each other. As early as 6 hours after treatment, this polarization and aggregation is pronounced, as indicated by the presence of foci of myoblasts that become much more discernible by 24 hours. Bar, top eight panels, 125 µm; bottom panel, 500 µm.