Apoptosis: Cell's internal "suicide" mechanism causing death of the cell.
Apoptosis: In the diphthong pt, the p is properly silent only at the begining of a word. Many speakers in the U.S. nonetheless silence it in this word. Programmed cell death; deletion of individual cells by fragmentation into membrane-bound particles, which are phagocytized by other cells. SYN: programmed cell death. [G. a falling or dropping off, fr. apo, off, + ptosis, a falling]Whereas some cells (e.g., cardiac and skeletal muscle fibers, CNS neurons) last a lifetime, others (e.g., epithelial and glandular cells, erythrocytes) have limited life-spans, at the end of which they are genetically programmed for self-destruction by apoptosis, usually to be replaced by others formed by mitosis from surviving cells. Apoptosis also plays an essential role in morphogenesis and tissue homeostasis by eliminating transitory organs and tissues (e.g., pronephros and mesonephros) and cells formed in excess of bodily needs during embryogenesis, as well as cells that have been damaged or virally infected. Cells in tissue cultures spontaneously undergo apoptosis after about 50 cell divisions. In contrast to cell death caused by injury, infection, or circulatory impairment, apoptosis elicits no inflammatory response in adjacent cells and tissues. Features of apoptosis detectable by histologic and histochemical methods include cell shrinkage, due chiefly to dehydration; increased membrane permeability, with a rise in intracellular calcium and a fall in pH; nuclear and cytoplasmic condensation; endolytic cleavage of nuclear DNA into oligonucleosomal fragments; and ultimately formation of apoptotic bodies, which are absorbed and removed by macrophages. Besides being due to genetic programming, apoptosis can be induced by injury to cellular DNA, as by irradiation and some cytotoxic agents used to treat cancer. It can be suppressed by naturally occurring factors (e.g., cytokines) and by some drugs (e.g., protease inhibitors). Apoptosis typically does not occur in malignant cells. Such cells therefore escape the destiny of their nonmalignant precursor cells and are said to be immortal. Immortalization can occur in various ways. The BCL2 gene, present in many cancers, directs the production of an enzyme that blocks apoptosis and immortalizes affected cells. Injury to DNA normally triggers apoptosis by activating the p53 tumor suppressor gene, which is missing or mutated in about one half of all human cancers. Cells that lack this gene can survive chemotherapy and irradiation intended to destroy cancer cells. Failure of apoptosis to occur is also involved in some degenerative diseases, including lupus erythematosus, and may be responsible for cellular damage caused by certain viruses, including HIV. Apoptosis has thus far been observed only in animal cells.
Source: Stedman's Medical Spellchecker, © 2006 Lippincott Williams & Wilkins. All rights reserved.
Apoptosis: An active process of selective destruction of differentiated cells in multicellular organisms, apoptosis is one of two mechanisms by which cell death occurs (the other being necrosis, a pathological process). Important in ontogenesis, tumorigenesis, tissue turnover, lymphocyte selection and function, hormone-induced atrophy, etc., it serves as a balance to mitosis in regulating the size of animal tissues and in mediating pathologic processes associated with tumor growth. Apoptosis is responsible for physiological deletion of cells and appears to be intrinsically programmed. It is characterized by distinctive morphologic changes in the nucleus and cytoplasm, including chromatin cleavage at regularly spaced sites and endonucleolytic cleavage of genomic DNA (DNA fragmentation) at internucleosomal sites.
Source: Diseases Database
Apoptosis: active process of selective destruction of differentiated cells in multicellular organisms; important in ontogenesis, tumorigenesis, tissue turnover, lymphocyte selection and function, hormone-induced atrophy, etc.; apoptosis is a specific mechanism involving self- fragmentation of chromatin.
Source: CRISP
Apoptosis: One of the mechanisms by which CELL DEATH occurs (compare with NECROSIS and AUTOPHAGOCYTOSIS). 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.
Source: MeSH 2007
Apoptosis: An abbreviation for:
Source: CRISP
Source - MeSH 2007
Source - MeSH 2007
Source - MeSH 2007
Source - CRISP
Source: CRISP
Source: CRISP
Source: CRISP
The following list attempts to classify Apoptosis into categories where each line is subset of the next.
Search to find out more about Apoptosis:
|
What do you think about the features of this website? Take our user survey and have your say:
Tools & Services:
Medical Articles:
Search Specialists by State and City
By using this site you agree to our Terms of Use. Information provided on this site is for informational purposes only; it is not intended as a substitute for advice from your own medical team. The information on this site is not to be used for diagnosing or treating any health concerns you may have - please contact your physician or health care professional for all your medical needs. Please see our Terms of Use.
Copyright © 2009 Health Grades Inc. All rights reserved.
