Description
Cell death occurs by two major mechanisms, necrosis and apoptosis. Apoptsis is also known as programmed cell death or ankoikis (a form of apoptosis which is induced by anchorage-dependent cells detaching from the surrounding extracellular matrix). Apoptosis leads to the elimination of cells without releasing harmful substances into the surrounding area. Too little or too much apoptosis plays a role in a great many diseases. When apoptosis functions inappropriately, cells that should be eliminated survive and potentially become immortal, as in cancer or leukemia. When apoptosis works overly well, too many cells may ?die? and the result may be grave tissue damage. This is the case in stroke and neurodegenerative disorders such as Alzheimer, Huntington and Parkinson diseases. The term ?apoptosis? refers only to the structural changes a cell goes through during the process of programmed cell death and not to the process itself. Classical necrotic cell death occurs due to noxious injury or trauma to the cell while apoptosis is an energy dependant mechanism that takes place during normal cell development. While necrotic cell death results in cell lysis, cellular apoptosis is characterized morphologically by cell shrinkage, nuclear pyknosis, chromatin condensation, and blebbing of the plasma membrane. Apoptosis is the result of a cascade of molecular and biochemical events involving endogenous endonucleases that cleave DNA into the prototypical ?ladder of DNA fragments? that may be visualized in agarose gels. Observation of oligonucleosomal DNA fragments by DNA laddering has long been the most acceptable and only available assay for the detection of apoptosis