Stereologic analysis of dystrophic chicken muscle.

Stereologic methods have been used to estimate the volume and surface densities of sarcoplasmic reticulum (SR) and T tubules of normal and dystrophic chicken pectoralis muscle fibers. The surface and volume densities of the T system in dystrophic muscle fibers showed large increases compared with normal muscle fibers; the surface and volume densities of the SR showed large decreases. In addition, the SR and T system in dystrophic fibers undergo changes in shape. The tubules of the free SR become much narrower; the T system becomes dilated and vesiculated. Dystrophic fibers, on the average, are much larger than normal but maintain the same sarcolemmal surface/fiber volume ratio as normal fibers. Alterations in the surface and volume densities of the dystrophic sarcotubular system may account for some of the altered contractile properties of these muscles.