A rapid and sensitive assay for the detection of DNA fragmentation during early phases of apoptosis

Apoptosis, or physiologic cell death, is an endogenous cellular process whereby senescent, DNA-damaged or diseased cells are eliminated from the body. Classically, apoptotic cells are identified by distinct morphological criteria in histological preparations (1). Apoptosis has been characterized biochemically by the activation of a nuclear endonuclease that cleaves the DNA into multimers of 180—200 basepairs and can be visualized as an 'oligosomal ladder ' by standard agarose gel electrophoresis (2). Recently, however, it has become apparent that the 'ladder' formation in lymphocytes is a very late and probably terminal event in a highly regulated biochemical and molecular cascade of events leading to activation Of endonucleases, DNA degradation and cell death (3). Additional evidence suggests that apoptosis in cells of epithelial or mesenchymal origin may not involve DNA degradation into oligonucleosomal multimers an