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Central nuclei in muscle fiber (photomicrographs)

Longitudinal sections of quadriceps femoris muscle of a 14-week human fetus (left) and a term neonate with X-linked myotubular myopathy (right). In both true fetal myotubes and the centronuclear fibers of myotubular myopathy, the nuclei occupy a central portion of the fiber with mitochondria and other organelles in the internuclear spaces. Nuclear chromatin of myotubes is less clumped and more finely dispersed. In fetal myotubes, the distance between nuclei within the same fiber is highly variable; in myotubular myopathy the spacing of nuclei is much more regular. (Used with permission. Sarnat HB. Myotubular myopathy: arrest of morphogenesis of myofibers associated with persistence of fetal vimentin and desmin. Four cases compared with fetal and neonatal muscle. Can J Neurol Sci 1990;17:109-23.)