- Programmed cell death
- Also called apoptosis, a form of cell death in which a programmed sequence of events leads to the elimination of cells without releasing harmful substances into the surrounding area. Apoptosis plays a crucial role in developing and maintaining health by eliminating old cells, unnecessary cells, and unhealthy cells. In contrast to the more familiar messy death known as necrosis, which is caused by an injury or attack that results in the hemorrhaging of cells and inflammation, apoptosis is a neat way to eliminate cells without leaving evidence behind. The human body replaces perhaps a million cells a second. Over the course of a year, that is roughly equal to the number of cells in the human body. Without an orderly process for getting rid of cells, we would double in size within a year. Too little or too much apoptosis plays a role in a great many diseases. When programmed cell death does not work right, cells that should be eliminated may hang around and become immortal. For example, in cancer and leukemia. When apoptosis works overly well, it kills too many cells and inflicts grave tissue damage. This is the case in strokes and neurodegenerative disorders such as Alzheimer, Huntington and Parkinson diseases. A protein called bcl-2 prevents cell suicide in normal healthy cells. Many cancer cells produce bcl-2 in abundance so they are not eliminated, as they should be, by apoptosis. Strictly speaking, the term apoptosis refers only to the structural changes cells go through, and programmed cell death refers to the complete underlying process, but the terms are often used interchangeably. "Apoptosis" is derived from the Greek apo, off, + ptosis, a falling = a falling off or dropping off.
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* * *the theory that particular cells are programmed to die at specific sites and during specific stages of development, often by the process of apoptosis. Although the two terms are often used synonymously, not all programmed cell death occurs by apoptosis.
Medical dictionary. 2011.
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Programmed cell death — (or PCD) is death of a cell in any form, mediated by an intracellular program. PCD is carried out in a regulated process which generally confers advantage during an organism s life cycle. PCD serves fundamental functions during both plant… … Wikipedia
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programmed cell death — A type of cell death in which a series of molecular steps in a cell leads to its death. This is the body’s normal way of getting rid of unneeded or abnormal cells. The process of programmed cell death may be blocked in cancer cells. Also called… … English dictionary of cancer terms
programmed cell death — noun a type of cell death in which the cell uses specialized cellular machinery to kill itself; a cell suicide mechanism that enables metazoans to control cell number and eliminate cells that threaten the animal s survival • Syn: ↑apoptosis,… … Useful english dictionary
programmed cell death — A form of cell death, best documented in development, in which activation of the death mechanism requires protein synthesis. Morphologically, the cell appears to die by apoptosis though this is not necessarily the case. Presumably requires some… … Dictionary of molecular biology
programmed cell death — noun Date: 1982 apoptosis … New Collegiate Dictionary
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