The structure of the T-system in human muscular dystrophy. A high-voltage electron-microscopic study

Biopsied muscle from 7 patients with Duchenne muscular dystrophy and from 5 normal controls was studied. Sections of 1-1.5 microns thickness treated with lanthanum were studied under a Hitachi H700 electron microscope at an accelerating voltage of 200 kV. The T-system in control muscle showed the network formation running transversely against muscle fiber at the level of the A-I junction, and occasional longitudinal connection between adjacent transverse tubules whereas that in Duchenne muscular dystrophy showed irregularity in course and position, an increase in the number of longitudinal tubules, dilatation of diameter, tangle formation and stratification. Degeneration, developmental defects, and abnormal regeneration may be considered as possible causes of these changes. Larger and relatively electron-dense areas connected with neighboring tubules which were found in this study are probably sarcoplasmic reticulum invaded by lanthanum. The changes in the T-system and anastomoses between the T-system and sarcoplasmic reticulum were more clearly detected by observation of 1-1.5 microns thick sections with the high-voltage electron microscope than with the conventional electron microscope.