Muscle tissue of the gastrocnemius (A) and soleus (inset, A) muscles. The animals had been subjected to muscle overuse coupled with local injections with NaCl. The muscle tissue shows a normal organization, and very occasional presence of necrotic muscle fibers (middle in inset). Bar = 50 μm. Muscle tissue of gastrocnemius muscles from two animals subjected to muscle overuse coupled with local injections with SP + C + Th; non-exercised side (B), exercised side (C). There is a variability in muscle fiber appearance, a very marked inflammatory infiltrate (to the right, B) and necrotic muscle fibers (arrowheads, C). There is a presence of very small muscle fibers in the inflammatory infiltrate (arrows, B). Bars = 50 μm.