Fig. 9. Effect of ryanodine treatment on differentiation of fetal myoblasts in culture. Fetal myoblasts were prepared from MLC3F-LacZ E16 embryos and cultured for 72 hours. Ryanodine was added in culture during the 24-48 hour time period and then removed (C,D) or during the 48-72 hours time period (E,F). All cells were fixed at 72 hours in culture and stained for ß-galactosidase activity. Untreated cells (A,B); cells treated with ryanodine during the 24-48 hour time period in culture (C,D); cells treated with ryanodine during the 48-72 hours time period in culture (E,F); ß-galactosidase staining (A,C,E); phase contrast micrographs (B,D,F). Bar, 10 µm. The experiments shown here were performed using 100 µM ryanodine; the same results were obtained using 300 µM ryanodine (data not shown).