The occurrence of inclusions within membrane-limited structures that run longitudinally in the cells of mammalian heart muscle

Abstract

Serial section electron micrographs of cat right ventricular myocardial and Purkinje cells show the presence of membrane-limited structures, most often elliptical in longitudinal and cross section. These structures, referred to as elliptical bodies, contain characteristic inclusions which run longitudinally within the elliptical bodies. The inclusions, which are 270–670 in cross section, have a trilaminar structure. Cross sections of the elliptical bodies and inclusions can be observed between the myofibrils and in the subsarcolemmal and perinuclear cytoplasm. In serial sections of the intercalated disk, the inclusions are found both intra- and extracellularly. It is suggested that these structures may have a secretory function, possibly related to the production of catecholamines.