Ultrastructural alterations in skeletal muscle of pigs with selenium-vitamin E deficiency

Light and electron microscopic studies were made of lesions which developed in skeletal muscles of 24 of 38 young growing pigs fed a semisynthetic diet deficient in selenium and vitamin E for 13 to 59 days. The major alterations in injured fibers progressed from hyaline degeneration, with subsequent macrophagic invasion and phagocytosis of disrupted sarcoplasm, to muscle fiber regeneration by myoblastic proliferation, fusion, and differentiation into fibers with mature myofibrils. The earliest electron microscopic alterations were myofibrillar lysis and disruption, with thick filaments persisting longest. Disruption of mitochondria, sarcoplasmic reticulum, and plasma membranes occurred in fibers with myofibrillar alterations. The basal lamina of the sarcolemma remained after destruction of the enclosed sarcoplasm and served as a scaffold for subsequent regeneration. Stages of regeneration included myoblastic proliferation, fusion into cords and myotubes, and, finally, fibrillogenesis to restore contractile material. The sequence of structural alterations in skeletal muscles of these affected pigs was discussed in terms of present theories of the biochemical role of these nutrients in maintaining cellular integrity.