apoptosis (redirected from Apoptosis regulatory proteins)

apoptosis /ap·op·to·sis/ (ap″op-to´sis) a pattern of cell death affecting single cells, marked by shrinkage of the cell, condensation of chromatin, and fragmentation of the cell into membrane-bound bodies that are eliminated by phagocytosis. Often used synonymously with programmed cell death. apoptot´ic

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ap·op·to·sis (pp-tss, p-t-)

n.

A natural process of self-destruction in certain cells that is determined by the genes and can be initiated by a stimulus or by removal of a repressor agent. Also called programmed cell death.

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apoptosis

[ā′pōtō′sis, ā′poptō′sis]

Etymology: Gk, apo, away, ptosis, falling

necrosis of keratinocytes in which the nuclei of the necrotic cells dissolve and the cytoplasm shrinks, rounds up, and is subsequently phagocytized. The term generally refers to "programmed" cell death.

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death [deth]

the cessation of all physical and chemical processes that invariably occurs in all living organisms. (See also dying.) There is at present no standardized diagnosis of clinical death or precise definition of human death. The most widely known and commonly accepted means of determining death evolved from several medical conferences held in the late 1960s for the purpose of defining irreversible coma or nonfunctioning brain as a new criterion for death. The indications of deep irreversible coma (or brain death) are (1) absolute unresponsiveness to externally applied stimuli; (2) cessation of movement and breathing, including no spontaneous breathing for three minutes after an artificial respirator has been turned off; and (3) complete absence of cephalic reflexes. The pupils of the eyes must be dilated and unresponsive to direct light.

Use of the electroencephalogram is also recommended as being of value in confirmation of irreversible coma or death. If there is a flat electroencephalographic reading at the time of apparent death and a second flat reading 24 hours later, then the patient may be declared dead.

There are two exceptions to the above criteria. These are in regard to patients exhibiting marked hypothermia (body temperature below 32.2°C), and those suffering from severe central nervous system depression as a result of drug overdose.

It is recognized that the above criteria are limited in that the notion of irreversibility is not readily agreed upon and may take on new meaning as medical technology advances. The criteria are especially helpful as complements to the traditional criteria of absence of heart beat and lack of spontaneous respiration as indications of death.

In 1981, a Presidential Commission for the Study of Ethical Problems in Medicine and Biomedical and Behavioral Research strongly recommended that all of the United States recognize the cessation of brain function as a definition of death, even in cases in which life-support systems could maintain respiratory and circulatory functions by artificial means.

activation-induced cell death (AICD) recognition and deletion of T lymphocytes that have been activated and so induced to proliferate. T lymphocytes are activated when a foreign agent is perceived, and AICD thereby prevents them from overgrowth. It is particularly important for regulation of lymphocytes that recognize self antigens.

black death bubonic plague; see plague.

brain death (cerebral death) see brain death.

clinical death the absence of heart beat (no pulse can be felt) and cessation of breathing.

cot death (crib death) sudden infant death syndrome (SIDS).

programmed cell death the theory that particular cells are programmed to die at specific sites and at specific stages of development.

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apoptosis (a·pp·tōˑ·sis),

n programmed destruction of cells; mechanism that keeps cell numbers in check by eliminating senescent cells or those without useful cell function.

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apoptosis (ap´tō´sis),

n cell reduction by fragmentation into membrane-bound particles that are phagocytosed by other cells.

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apoptosis

programmed cell death, a process including coagulative necrosis and shrinkage.

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apoptosis 

A process of single cell death, which consists of a series of biochemical events including cell shrinkage, condensation of chromatin, formation of cytoplasmic blebs and fragmentation of nuclear DNA into membrane-bound particles that are phagocytosed by other cells. It is an important physiological process that helps keep the number of cells relatively constant by compensating for mitosis. It is necessary to prevent either uncontrolled growth and tumour formation (as may be caused by genetic mutation), or hypotrophy (as in ischaemia) due to excessive apoptosis induced by a stimulus, such as irradiation, toxic drugs, etc. Apoptosis represents a form of programmed cell death. Example: almost all corneal epithelial cells die within 10 days, and are replaced by mitosis. See mitosis; neuroprotection.