Department of Anatomy, State University of New York at Buffalo, Buffalo, N. Y.
Right and left tibialis anterior muscles of 25 gm (male) albino, Swiss-Webster mice were transected. Left legs were X-irradiated locally with a single dose of 525 r at each of the following post-transection hours: 0, 24, 35, 42, 48, 50, 55, 60, 65, 72. Radiation factors were 90 KVP, 4.5 ma, 1 mm Al filter, 175 r/min. Unexposed right legs provided controls. Tissues were fixed for histological study six days after transection and serial sections of five cases were examined for each of the times indicated above.
All; sections of wounds irradiated at 0, 24, 35 and 42 hours showed severe inhibition of muscle regeneration. Wounds at 50, 55, 60, 65 and 72 hours exhibited the overall histological features of normal six day regeneration. The critical period of muscle regeneration with respect to radiation sensitivity appears to be between 42 and 50 hours post-transection. (Supported by the United States Atomic Energy Commission under contract AT (30-7)3027.