Dystrophin and fetal myosin staining in muscle fiber transplants in xmd hematopoietic chimeras at 3 weeks and 5 months after transplantation of muscle. Myofiber transplant from original HC donors to the xmd HC transplant recipients was performed on 3 pairs of dogs. Muscle biopsies were taken at 3 weeks (G123) and 5 months (G141 and G142) after transplantation and costained with dystrophin (red), fetal myosin (green, indicating regeneration), and DAPI (blue, showing nuclear staining). Immunofluorescence staining was performed as described in Figure 5, with the following primary antibodies: rabbit anti–mouse dystrophin (1:400, a kind gift from Jeff Chamberlain, University of Washington, Seattle) and mouse anti–rat fetal myosin (1:20, NCL-MHCd; Novocastra Laboratories). Donkey anti–rabbit Rhodamine-conjugated secondary antibody and rabbit anti–mouse FITC-conjugated secondary antibody (1:100 dilution; Invitrogen) were used for detection. Normal mouse and rabbit isotype (Invitrogen) antibodies were used as negative controls. Focal areas of brightly stained dystrophin-positive fibers were noted in panel A and were also positive for fetal myosin staining. Scattered staining for dystrophin and fetal myosin was observed in panel B after 5 months. However, dystrophin-positive fibers were now negative for fetal myosin. Wild-type muscle from G292 was used as control.