BACKGROUND: Modes of cell death have been defined morphologically as apoptosis and oncosis. @entity1188 have been reported to show apoptosis, as revealed by DNA fragmentation by DNA ladder and by in situ terminal deoxynucleotidyl transferase-mediated @entity1977 nick end-labeling (TUNEL) at the light microscopic level. We investigated whether TUNEL-positive infarcted myocytes have apoptotic or oncotic ultrastructures by using electron microscopic TUNEL, which can simultaneously observe the ultrastructure and DNA fragmentation of the same myocytes. METHODS AND RESULTS: Thirty @entity95 were divided into 5 groups (n=6 each) that were subjected to a sham operation or to 30-minute @entity63 followed by 0-minute, 30-minute, 2-hour, or 4-hour reperfusion of a coronary artery. In the 2- and 4-hour reperfusion groups only, DNA electrophoresis showed a ladder pattern, and the light microscopic TUNEL finding was positive in the nuclei of myocytes localized in the infarcted area (6+/-2% and 11+/-3%, respectively). Electron microscopic TUNEL showed that nuclei with a significant accumulation of immunogold particles (indicating an electronic microscopic TUNEL-positive result) were observed only in the infarcted myocytes with irreversibly oncotic ultrastructures that were found in the hearts of the 2- and 4-hour reperfusion groups (41+/-3% and 83+/-4%, respectively). Irreversibly oncotic myocytes (indicated by swelling, inhomogeneously clumped chromatin in nuclei, dense bodies in mitochondria, and/or ruptured plasma membranes) were also seen in the 0- and 30-minute reperfusion groups, which did not exhibit TUNEL-positive myocytes. There was no evidence of apoptotic ultrastructures in the myocytes. CONCLUSIONS: DNA fragmentation occurs in the myocytes that had already shown irreversibly oncotic, but not apoptotic, ultrastructures with @entity63 and/or reperfusion. Therefore, DNA fragmentation itself does not always mean apoptosis, and so-called apoptotic infarcted myocytes may belong to a category of cell death other than apoptosis.

"Apoptotic" myocytes in @entity1188 area in XXXX hearts may be oncotic myocytes with DNA fragmentation: analysis by immunogold electron microscopy combined with In situ nick end-labeling.

@entity1188 :: ('MESH:D007238', 'Disease') :: ['Infarcted myocytes'] @entity95 :: ('9986', 'Species') :: ['rabbits'] @entity1977 :: ('CHEBI:17625', 'Chemical') :: ['dUTP'] @entity63 :: ('MESH:D007511', 'Disease') :: ['ischemia']
@entity95 :: (9986,Species) :: ['rabbit']
