Immunohistochemical and electron microscopical studies of myocardial inclusions in hereditary myopathy of the diaphragmatic muscles in Holstein-Friesian cattle

In hereditary myopathy of the diaphragmatic muscles in Holstein-Friesian ca ttle, the largest number of acidophilic intracytoplasmic inclusions was fou nd in the myocardium. These inclusions, which were oval and measured 12-15 mu m in the transverse sections, were characterized by a dense, amorphous z one, and a relatively hyalinized sarcous substance in paraffin-embedded hem atoxylin and eosin (H & E)-stained sections. Histochemically, each inclusio n was stained intense red and dark green with H & E and Gomori's trichrome, respectively. NADH-TR activity was absent. The region surrounding the incl usions was less acidophilic with H & E, and showed an increased activity wi th NADH-TR. The inclusions showed no immunoreactivity for desmin, vimentin, actin or a-actinin, while strong desmin immunoreactivity was observed in t he region surrounding the inclusion. Some inclusions showed strong immunore activity for ubiquitin, but others reacted only faintly. Ultrastructurally, the inclusion had a dense core composed of myofibrillar aggregations. The periphery of this dense core was surrounded by thin or intermediate-sized f ilaments, which corresponded to the desmin-positive area. This alteration w as sometimes found to be continuous with the Z disk. which showed streaming or disintegration or with the desmosome of the intercalated disk. We discu ss here the similarity between this specific inclusion and the other altern ative organelles that have been reported previously in cardiomyopathy or in cardiac lesions associated with various myopathies.