Apoptosis

Morphologic pattern of cell death affecting single cells and marked by shrinkage of the cell, condensation of chromatin, formation of cytoplasmic blebs, and fragmentation of the cell into membrane‐bound apoptotic bodies that are eliminated by phagocytosis.

One of the two mechanisms by which cell death occurs (the other being the pathological process of necrosis). Apoptosis is the mechanism responsible for the physiological deletion of cells and appears to be intrinsically programmed. It is characterized by distinctive morphologic changes in the nucleus and cytoplasm, chromatin cleavage at regularly spaced sites, and the endonucleolytic cleavage of genomic DNA (DNA fragmentation) at internucleosomal sites. This mode of cell death serves as a balance to mitosis in regulating the size of animal tissues and in mediating pathologic processes associated with tumor growth.

Also called “Programmed cell death,” it is a series of programmed steps that cause a cell to die via “self digestion” without rupturing and releasing intracellular contents (e.g., nucleus, chromosomes, refractile bodies, etc.) into the local (i.e., surrounding tissue) environment. Manifestations of cell apoptosis include shrinking of the cell’s cytoplasm and chromatin condensation.

A pattern of cell death affecting single cells; refers to programmed cell death.

A form of cell death that is necessary both to make room for new cells and to remove cells whose DNA has been damaged and which may become cancerous.

Programmed cell death. The half-life of cells varies throughout the body. It depends on a variety of factors including age, nutritional status, health status, and genetics, as well as factors not yet identified. Age is important. Growing individuals are in a phase of life in which cell number is increasing exponentially. Once growth and development are complete this increase in cell number slows down. In contrast, senescence is characterized by a gradual loss in total cell number as well as losses in discrete cell types. Cell turnover has two parts; cell replacement and cell death. Cell death is either a concerted, all at once, event or a programmed, gradual process. If the former, cell death is called necrosis. This occurs if a tissue sustains an injury, whether it be small or large. Necrotic cell death is preceded by cell enlargement and a swelling of all the organelles within the cell. The DNA disintegrates and its nucleotides are degraded.

Programmed death of cells that is under genetic control; the cell’s own genes play an active role in its demise. Apoptosis is different from cell necrosis where healthy cells are destroyed by external processes, such as inflammation. This is a common process during development (e.g., formation of the central nervous system) as well as in adulthood (e.g., cyclic breakdown of the endometrial lining of the uterus that leads to menstruation). Certain cancer patients lack the tumor suppressor gene that helps prevent cancer by making a protein that triggers apoptosis in abnormal cells. Absence or abnormality of permits cancer cells to continue to grow.

This is a genetically controlled type of cell death. There is an orchestrated collapse of a cell, typified by destruction of the cell’s membrane; shrinkage of the cell with condensation of chromatin; and fragmentation of DNA. The dead cell is then engulfed by adjacent cells. This process occurs without evidence of the inflammation normally associated with a cell’s destruction by infection or disease. Apoptosis, first identified in 1972, is involved in biological activities including embryonic development, ageing and many diseases.

Programmed cell death; genetic limitation of the lifespan of cells. The process may be important in limiting growth of tumors.