Local radiation is not a critical factor in marrow-to-muscle chimerism. C57BL/6 animals underwent transplantation with GFP-positive marrow cells from transgenic mice after 500 or 1000 cGy local, systemic, or systemic radiation with shielding of the right leg followed by injection of cardiotoxin intramuscularly. (A-B) The percentage of GFP-positive fibers in the right tibialis anterior muscle is shown. Each bar shows average ± standard error from 5 to 6 animals from 2 separate experiments. ^*P < .05 between the groups. (C) The results of panels A and B are corrected for the average weight of muscles. (D-F) Photomicrographs of frozen sections of the tibialis anterior muscle in animals that received 1000 cGy local radiation (D), 1000 cGy TBI (E), or 1000 cGy TBI with shielding of the lower extremity (F). Arrows point to the GFP-positive muscle fibers.