Fig. 1.

Muscle biopsy. Quadriceps muscle biopsy shows marked variability in fiber size with proliferation of perimysial and endomysial connective tissue without inflammation and necrosis (A). Hystochemistry for cytocorme c-oxidase does not show disorganization of the intermyofibrillar network (B). Immunochemistry for Myosin isoforms shows type I fibers predominance (monoclonal antibodies against slow type I fibers, Leica Microsystems) (C). In (D) are shown the rare and hypotrophic type II fibers (monoclonal antibody against fast type fast IIa and IIx fibers, mAb A4.74, Hybridoma Bank, The University of Iowa, Department of Biology, Iowa City).