Ultrastructural Fiber Typing in Normal and Diseased Human Muscle

Abstract

Histochemical analysis of muscle biopsies is well established as being essential for the definitive evaluation of neuromuscular disorders. The usefulness of electron microscopy as both a diagnostic and research tool in the study of diseased skeletal muscle has also been demonstrated. Reliable cross-correlation between histochemical and electron microscopic findings would appear to be useful. Based on the variations of the histochemical reaction for myofibrillar ATPase, there appear to be three constant categories in normal human skeletal muscle (types I, IIA and IIB). An attempt has therefore been made to define the ultrastructural correlates of each of these three major fiber types based on the measurements of Z-line and M-line widths. We have recently had the opportunity to study biopsied muscle from patients with 3 muscle disease states in which there was a relative deficiency of at least one of the 3 fiber types.