[Structural and ultrastructural features of the skeletal muscle in Werdnig-Hoffmann disease]. / Aspetti strutturali ed ultrastrutturali del muscolo striato nella malattia di Werdnig-Hoffmann.

In researches performed on striated muscles of individuals affected by various myopathies, fragments of gastrocnemius muscle in course of Werdnig-Hoffmann disease have been studied. The light microscopic observations demonstrate the presence of numerous, very thin, atrophic fibres with many irregularly lobated and packed nuclei alternating with apparently normal fibres with lighter and larger nuclei. The connective part of the muscle appears to be remarkably increased and replaces the atypical contractile tissue. The electron microscope shows, in the atrophic fibres, remarkable alterations of the sarcoplasmatic elements, and a complete disarrangement of myofibrils and myofilaments, some of which are anchored to fragments of the Z bands, irregularly arranged. Even the normal orientation of the sarcomeres often with indefinite bound, is upset. The numerous lobated nuclei totally occupy the irregular protrusions of the sarcoplasm, rich in peripheral microvesicles. In respect of other examined myopathies, in which the muscle fibres alterations affect limited parts of the contractile elements, in these cases the modifications seem to be of greater entity and to affect completely single muscle fibres.

[Further observations by electron microscope of striated muscle in progressive Duchenne muscular dystrophy]. / Ulteriori osservazioni al microscopio elettronico del muscolo striato nella distrofia muscolare progressiva di Duchenne.

Gastrocnemius muscle fragments of children affected by clinically diagnosed progressive muscular dystrophy of Duchenne have been studied. At the light microscope, in the semi-thin sections, the more evident changes are represented by a wide diameter range of the fibers and fatty infiltration. Some fibers show numerous nuclei in their central part, a sarcoplasmic degeneration of vacuolar type and an irregular and tortuous course of the myofibrils. Moreover, the ultrastructural findings have shown characteristic changes in myofilaments and Z bands represented by: streaming of the Z bands, collection of the triads and concentric laminated bodies. These observations have pointed out a certain gradualness of the alterations, starting from focal changes of Z band to the complete disarrangement of myofilaments.