Effect of marrow-cell dose on marrow-to-muscle conversion. C57BL/6 mice underwent transplantation with 3 different doses (5, 20, and 100 million) of bone marrow cells after 900 cGy whole-body radiation. Seven days later cardiotoxin was injected into the tibialis anterior muscle. Four weeks after injury animals were killed, and muscle samples were analyzed for the incidence of GFP-positive muscle fibers. There was a graded increase in the incidence of GFP-positive muscle fibers as the doses of infused GFP marrow cells increased, whereas the level of peripheral blood chimerism changed minimally. The results represent data from a total of 6 mice per cell level from 2 separate experiments. Error bars indicate mean ± standard error.