The most exhastive description of oncosis ("accidental cell death",
necrosis) was provided by Majno and Joris in Am. J. Pathol., 146: 3-16,
1995. The lack of DNA fragmentation alone cannot does not exclude
apoptosis. Ther are numerous publications which provide examples when
apoptosis occurs, revealed by typical changes in cell morphology, yet
without DNA fragmentation which could be detected by gel electrophoresis
("DNA laddering") of the presence of DNA strand breaks. I have been
recently told by Dr. Peter Krammer (Heidelberg) that he observed
apoptosis even in the absence of 300-50 kb DNA fragmentation.
In doubtful situations the distinction between apoptosis and oncosis can
be made only by electron or/and light microscopy. Swelling of the cell
and in particular of mitochondria, distortion of the mitochondrial
membranes, chromatin condensation at the nuclear periphery (but without
a loss the nuclear structure features) and subsequently rupture of
plasma membrane are typical of oncosis. Oncotic/ necrotic cells at later
stages have exposed phosphatidylserine and thus are reactive with
annexin V- FITC. On the other hand during apoptosis both cytoplasm and
nucleus undergo condensation, the condensed chromatin is amorphous, DNA
in such chromatin shows hyperchromasia and nucleus frequently (but not
always) undergoes fragmentation.
Zbigniew Darzynkiewicz
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