HEREDITARY MYOPATHY OF THE DIAPHRAGMATIC MUSCLES IN HOLSTEIN-FRIESIANCATTLE

We describe a family line with an autosomal recessive disease of muscu lar dystrophy of the diaphragmatic muscles in Holstein-Friesian cattle . Histopathological examination in the present cases revealed various degenerative changes in the diaphragmatic and other thoracic muscles a s follows: variation in muscle fiber diameter, fiber splitting, sarcop lasmic masses, ring fiber, vacuolar and hyalinized degeneration of mus cle fibers. In addition, central core-like structures were the promine nt features in the diaphragmatic muscles, occupying the center of the fiber or scattered within the fiber. These pathological alterations ar e consistent with the diaphragmatic myopathy previously reported in Me use-Rhine-Yssel cattle in the Netherlands. The fibers containing core- like structures' consisted of three distinct zones which could be well distinguished by NADH-tetrazolium reductase activity. This activity w as absent in the innermost zone, decreased in the intermediate zone, a nd normal or increased in the periphery. Electron microscopically, thi s structure appeared to be composed of focal myofibrillar degeneration beginning with streaming or disintegration of the Z disk. We discuss here the similarity between this core-like structure and the other alt ernative organelles that have been reported previously, and a possible defect or storage in the cytoskeleton from the findings of the Z disk abnormalities.