Fig. 11. (A-C) GFP expression in myotomes after PSM grafts performed at different stages and level. Transverse sections were immunostained with antibody against GFP (brown) and counterstained with Haematoxylin (blue). (A) Early medial PSM grafted muscles expressing GFP in the myofibre nuclei (black arrows), but not in the satellite cell nuclei (red arrows). (B) Late medial PSM grafted muscles showing GFP expression in both myofibre nuclei and in satellite cells. (C) Early lateral PSM grafted muscle showing GFP expressed in myofibre nuclei and in a few satellite cells. (D) Muscle transverse section immunostained with Pax7 antibody (brown) (not counterstained). Pax7 expression is detected in the flat nuclei (red arrows) and not in the large round myofibre nuclei (black arrows), suggesting that the flat nuclei are those of satellite cells. Scale bars: 10 µm.