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1. the death of one or more cells in the body, usually within a localized area, as from an interruption of the blood supply to that part
2. death of plant tissue due to disease, frost, etc.



the death within the living organism of individual organs or their component tissues or cells.

A necrosis is classified according to the pathological condition that causes it. Thus, frostbite and burns can cause traumatic necrosis; neurotropic necrosis arises with syringomyelia and the nervous form of leprosy; infarcts and gangrene are associated with circulatory, or ischemic, necrosis; caseous necroses occurring in tuberculosis and syphilis are forms of septic necrosis; and fibrinoid necrosis associated with allergic diseases is a type of allergic necrosis.

Necrosis is accompanied by characteristic changes in the cell and in the intercellular substances. The nucleus shrinks and coagulates, a process known as pycnosis, and the cytoplasm breaks up into clumps. The cell eventually lyses, that is, it degenerates and dissolves. The lysis is due to the activation of the lysosomal hydrolytic enzymes, such as ribonuclease, deoxyribonuclease, and acid phosphatase. The activation of the lysosomes occurs as a result of an increase in the permeability of the cell membranes, changes in the osmotic equilibrium, and acidosis—an abnormal increase in the intracellular hydrogen-ion concentration. Fibrinoid changes appear in the connective tissue, and nerve fibers become fragmented and disintegrate into clumps.

The clinical and morphological manifestations and further consequences of necrosis depend on the localization and distribution of the necrosis and on the mechanisms and conditions of origin. The following types of advanced necrotic conditions can develop: dry necrosis, such as Zenker’s degeneration of infected muscles; colliquative, or liquefactive, necrosis, which occurs for example, when a focus of softening arises in the brain in response to cerebral hemorrhage; gangrene; and bed sores. Necrotic tissue tears away; then, either connective tissue grows through it or the necrotic tissue undergoes autolytic or purulent liquefaction. Finally, the necrotic tissue becomes encapsulated and petrified.

The two most serious consequences of necrosis are a loss of function owing to the death of the structural elements of the necrotic tissues or organs and poisoning caused by the actual presence of a necrotic focus and by the inflammation that arises in response to this presence.



Death of a cell or group of cells as a result of injury, disease, or other pathologic state.
References in periodicals archive ?
[sup.99m]Tc-methionine andiodine-123-a-methyl tyrosine ([sup.123]I-IMT) has been also evaluated for the detection of radiation necrosis [56].
Contrary to radiation necrosis, the pathophysiology of pseudoprogression remains elusive and further studies are needed.
Fotopoulos, "Glioma recurrence versus radiation necrosis: accuracy of current imaging modalities," Journal of Neuro-Oncology, vol.
Iwai et al., "Diagnostic accuracy of 11C-methionine PET for differentiation of recurrent brain tumors from radiation necrosis after radiotherapy," Journal of Nuclear Medicine, vol.
Heiserman et al., "Differentiating recurrent tumor from radiation necrosis: time for reevaluation of positron emission tomography?," American Journal of Neuroradiology, vol.
Shinoda et al., "Comparison of (11) C-methionine, (11)C-choline, and (18)F-fluorodeoxyglucose-PET for distinguishing glioma recurrence from radiation necrosis," Neurologia Medico-Chirurgica, vol.
Xu, "Role of magnetic resonance spectroscopy for the differentiation of recurrent glioma from radiation necrosis: a systematic review and meta-analysis," European Journal of Radiology, vol.
Weber et al., "Uptake of [sup.18]F-fluorocholine, [sup.18]F-fluoroethyl-L- tyrosine, and [sup.18]F-FDG in acute cerebral radiation injury in the rat: implications for separation of radiation necrosis from tumor recurrence," Journal of Nuclear Medicine, vol.
Kuroiwa, "Delayed brain radiation necrosis: pathological review and new molecular targets for treatment," Medical Molecular Morphology, vol.
Filss et al., "Role of O-(2[sup.18]F- Fluoroethyl)-L-tyrosine PET for differentiation of local recurrent brain metastasis from radiation necrosis," Journal of Nuclear Medicine, vol.
This limits the utility of MRS in differentiating residual/ recurrent tumor from radiation necrosis, as is the case with MR perfusion.
Alternatively, infiltrating microglia near a focus of radiation necrosis may be mistaken for a malignancy in a treated glioma.

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