Fig. 2. Quail muscle fibers formed within chicken pectoral stroma show the quail pattern of fiber-type. Quail somites were transplanted into chicken embryos at ED2 and the pectoral muscles were isolated and sectioned at ED10. (A) The transplanted half of the pectoral muscle contains a substantial number of quail-derived muscle fibers, as evidenced by quail-specific antigen staining (red) in fast MyHC-expressing fibers (blue). (B) Approximately half of the quail-derived muscle fibers express slow MyHC (green). (C and D) At the same position within the contralateral control side of the chicken pectoral muscle, there is no quail contribution to either muscle or stromal cells, and as expected, no slow fibers are found within this region. Scale bar is 100 µm.