Hence, the other term for the process is programmed cell death. However, in several diseases the cell death program goes awry. Apoptosis was originally defined in terms of morphological changes, such as reduction in cell volume, condensation of the nucleus and membrane blebbing. Cells undergoing apoptosis fragment into membrane-bound apoptotic bodies that are readily phagocytosed and digested by macrophages or other neighboring cells without generating an inflammatory response. This is in contrast to necrosis, which results from gross insult to the cell, characterized by cell swelling, release of lysosomal enzymes, cellular disintegration and inflammation.
Apoptosis occurs in multiple cell types and can be triggered by multiple extracellular stimuli.
With the discovery of several cell death genes conserved across numerous species, the cell death pathways are currently under intensive study. This DNA fragmentation is one hallmark of apoptosis. Typically, the DNA of apoptotic cells is cleaved into a population of fragments, composed of multimers of 180-200bp in length. The DeadEnd TM Colorimetric Apoptosis Detection System end-labels the fragmented DNA of apoptotic cells. Figure 1 shows the steps of the assay.