ULTRASTRUCTURE OF THE MUSCLE SPINDLE IN DYSTROPHIA MYOTONICA. I. THE INTRAFUSAL MUSCLE FIBRES

Publisher Website
Google Scholar
Abstract
The abnormal intrafusal muscle fibers of 4 spindles located in extensor indicis biopsies from 2 patients with dystrophia myotonica were examined by EM. In all cases, the fibers had undergone severe longitudinal fragmentation in their equatorial, proximal-polar and mild-polar zones. It was not possible to differentiate the fibers into nuclear bag and nuclear chain types. Many of the fragments were arranged in clusters, each cluster being bounded by a single basement membrane. Numerous partially divided fibers were seen in mid-polar sections and a morphological picture of the fragmentation process was presented. The ultrastructural appearance of individual fiber fragments ranged from normality through to severe atrophy. Intrafusal satellite cells showed an increase in numbers, presumably in response to the pathological processes affecting the muscle fibers. The nature of this response is discussed.