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Animal cells can self-destruct via an intrinsic program of cell death (Steller, 1995). Apoptosis is a form of programmed cell death that is characterized by specific morphologic and biochemical properties (Wyllie et al., 1980). Morphologically, apoptosis is characterized by a series of structural changes in dying cells: blebbing of the plasma membrane, condensation of the cytoplasm and nucleus, and cellular fragmentation into membrane apoptotic bodies (Steller, 1995; Wyllie et al., 1980).
The most important meshanism in development and homeostasis in adult tissues is Programmed cell death (PCD). It is for the removal of either superfluous, infected, transformed or damaged cells by activation of an intrinsic suicide program. Apoptosis is from of PCD. It is an ancient Greek word used to describe the "falling off" of petals from flowers or leaves from trees and was proposed by Kerr, Wyllie and Currie in 1972 to refer to the peculiar morphology of physiologically occurring cell death which plays a complementary but opposite role to mitosis in the regulation of animal cell populations.
Biochemically, apoptosis is characterized by the degradation of chromatin, initially into large fragments of 50-300 kilobases and subsequently into smaller fragments that are monomers and multimers of 200 bases (Oberhammer et al., 1993; Wyllie, 1980). Other biochemical indicators of apoptosis are induced or increased levels of the protein clusterin (Pearse et al., 1992), also known as TRPM-2 or SGP-2, and activation of the enzyme typeII transglutaminase, which crosslinks proteins to the envelope of apoptotic bodies (Fesus et al., 1991). Apoptosis is a complex phenomenon of related morphological and biochemical processes that can vary with tissue and cell type (Zakeri et al., 1995).
Apoptosis (form of PCD) is characterized by maintenance of intact cell membranes during the suicide process so as to allow adjacent cells to engulf the dyin...