Intranuclear glycogen deposits in human cardiac muscle cells: Ultrastructure and cytochemistry

Ultrastructural and cytochemical studies of myocardial biopsies disclosed the presence of glycogen deposits within nuclei of hypertrophied and normal-sized cardiac muscle cells in 6 (7%) of 90 patients with various cardiac diseases. Intranuclear glycogen appeared as β-particles, 160 to 360 Å in diameter, which either formed small aggregates or were dispersed in the nucleoplasm. Cells containing intranuclear glycogen did not show damage or degeneration. Glycogen particles in the cytoplasm of these cells were of the same size and appearance as those in the nuclei. Criteria for the ultrastructural identification of intranuclear glycogen are proposed, and it concluded that under certain conditions the nuclei of cardiac muscle cells can acquire the capacity to synthesize glycogen.