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 cattle, the largest number of acidophilic intracytoplasmic inclusions was found in the myocardium. These inclusions, which were oval and measured 12–15 μm in the transverse sections, were characterized by a dense, amorphous zone, and a relatively hyalinized sarcous substance in paraffin-embedded hematoxylin and eosin (H & E)-stained sections. Histochemically, each inclusion was stained intense red and dark green with H & E and Gomori’s trichrome, respectively. NADH-TR activity was absent. The region surrounding the inclusions was less acidophilic with H & E, and showed an increased activity with NADH-TR. The inclusions showed no immunoreactivity for desmin, vimentin, actin or α-actinin, while strong desmin immunoreactivity was observed in the region surrounding the inclusion. Some inclusions showed strong immunoreactivity 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 filaments, which corresponded to the desmin-positive area. This alteration was sometimes found to be continuous with the Z disk, which showed streaming or disintegration or with the desmosome of the intercalated disk. We discuss here the similarity between this specific inclusion and the other alternative organelles that have been reported previously in cardiomyopathy or in cardiac lesions accociated with various myopathies. Received: 27 April 1998 / Revised, accepted: 10 August 1998