apoptosis
Physiology
(noun)
A type of "cell suicide" called programmed cell death
that occurs in multicellular organisms.
Biology
(noun)
a process of programmed cell death
Psychology
(noun)
The process of programmed cell death.
Microbiology
Examples of apoptosis in the following topics:
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Programmed Cell Death
- Apoptosis is the process of PCD that may occur in multicellular organisms.
- Apoptosis can also be initiated via external signaling.
- Apoptosis is also essential for normal embryological development.
- It is hypothesized that necroptosis can serve as a cell-death backup to apoptosis when the apoptosis signaling is blocked by endogenous or exogenous factors, such as viruses or mutations.
- This video describes the process of apoptosis, or programmed cell death.
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Cell Signaling and Cell Death
- When a cell is damaged, unnecessary, or dangerous to an organism, a cell can initiate the mechanism for cell death known as apoptosis.
- External signaling can also initiate apoptosis.
- Another example of external signaling that leads to apoptosis occurs in T-cell development.
- Apoptosis is also essential for normal embryological development.
- A cell signaling mechanism triggers apoptosis, which destroys the cells between the developing digits.
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Natural Killer Cells
- NK cells use wo cytolytic granule-mediated apoptosis to destroy abnormal and infected cells.
- Apoptosis is a form of "programmed cell death" in which the cell is stimulated by the cytotoxic mechanisms to destroy itself.
- Unlike with lysis, apoptosis does not degrade DNA, and cells are destroyed cleanly and completely on their own.
- In apoptosis, these virus particles are destroyed.
- However, cancer cells often develop genetic mechanisms to prevent apoptosis signals from occurring, so cell lysis is generally more effective.
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Tumor Suppressor Genes
- At this point, a functional p53 will deem the cell unsalvageable and trigger programmed cell death (apoptosis).
- The damaged version of p53 found in cancer cells, however, cannot trigger apoptosis.
- If repairs are unsuccessful, p53 signals apoptosis.
- A cell with an abnormal p53 protein cannot repair damaged DNA and cannot signal apoptosis.
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Natural Killer Cells
- Typically immune cells detect MHC that is present on infected cell surfaces, triggering cytokine release and causing lysis or apoptosis.
- The granzymes then break down the target cell, inducing death by either apoptosis or osmotic cell lysis.
- Natural cytotoxicity receptors directly induce apoptosis after binding to ligands that directly indicate infection of a cell.
- The MHC dependent receptors (described above) use an alternate pathway to induce apoptosis in infected cells.
- Functions of NK cells include: Cytolytic Granule Mediated Cell Apoptosis; Antibody-Dependent Cell-Mediated Cytotoxicity (ADCC); Cytokine induced NK and CTL activation; Missing 'self' hypothesis; Tumor cell surveillance; NK cell function in adaptive response; NK cell function in pregnancy; and NK cell evasion by tumor cells .
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Cartilaginous Joints: Synchodroses
- In puberty, increasing levels of estrogen, in both females and males, leads to increased apoptosis of chondrocytes in the epiphyseal plate.
- Depletion of chondrocytes due to apoptosis leads to less ossification, and growth slows down and later stops when the cartilage has been completely replaced by bone.
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WBC Function
- When pathogens are encountered, granule dependent apoptosis (a mechanism of cytotoxicity) may be induced in the pathogen by releasing perforins, granzymes, and proteaseases from their granules.
- Pathogens that bear the T cell's antigen are destroyed through cytotoxic induced apoptosis and protease activity.
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Type IV (Delayed Cell-Mediated) Reactions
- Cytotoxic T cells cause death by apoptosis without using cytokines.
- 1. activating antigen-specific cytotoxic T-lymphocytes that are able to induce apoptosis in body cells displaying epitopes of foreign antigen on their surface, such as virus-infected cells, cells with intracellular bacteria, and cancer cells displaying tumor antigens
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Cancer Viruses
- This can result from having control of their own growth signals, losing sensitivity to anti-growth signals, and losing the ability to undergo apoptosis, or programmed cell death.
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Damage to the Cell Wall
- Damage to the cell wall disturbs the state of cell electrolytes, which can activate death pathways (apoptosis or programmed cell death).