Degeneration

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degeneration

1. Biology the loss of specialization, function, or structure by organisms and their parts, as in the development of vestigial organs
2. Biology
a. impairment or loss of the function and structure of cells or tissues, as by disease or injury, often leading to death (necrosis) of the involved part
b. the resulting condition
3. Electronics negative feedback of a signal

Degeneration

 

(biology). (1) In morphology, the process of cell or organ destruction; for example, the disappearance of the tail in the tadpole when it is transformed into a frog.

(2) In microbiology, the attenuation of the viability of a culture of unicellular organisms under unfavorable growth conditions.

(3) The concepts of general and specific degeneration were introduced into the theory of evolution by A. N. Severtsov. By general degeneration, or morphophysiological regression, Severtsov meant one of the trends of the evolutionary process, characterized by a reduction of the organs with active functions (organs of locomotion, sense organs, the central nervous system) and the progressive development of organs that are passive but important for the animal’s survival (the sexual system and the passive means of defense, such as integuments and protective coloration). The development of tunicates, cirripeds, and tapeworms proceeded according to the principle of general degeneration. In specific degeneration, organs present in the ancestors are reduced in the process of an organism’s historical development: for example, the extremities in legless lizards and the shell in cephalopods. The cause of the reduction of organs is the absence of the conditions necessary for their development and functioning.

(4) In pathology, the term “degeneration” was introduced by R. Virchow, who admitted the possibility of the “degeneration” of cells. Present-day medicine has established that changes in cells depend on local or general metabolic disturbance, or dystrophy.


Degeneration

 

a change in the structure and/or function of cells and tissues as a result of certain diseases. The term “degeneration” was introduced into the language of general pathology by R. Virchow to designate processes in which the normal components of the cytoplasm are displaced and in which unnecessary or harmful deposits form in the intercellular matter. The deposits include protein-like substances, fatlike substances (in which case the deposition process is called lipoidosis), and calcium salts. In Soviet medical literature these pathological processes, which Virchow called degenerations, are conventionally termed dystrophies.

In some medical disciplines, “degeneration” has a specific meaning. For example, in neuropathology it usually refers to decomposition of the nerve fiber as a result of injury or death of the corresponding neuron.

degeneration

[di‚jen·ə′rā·shən]
(electronics)
The loss or gain in an amplifier through unintentional negative feedback.
(medicine)
Deterioration of cellular integrity with no sign of response to injury or disease.
General deterioration of a physical, mental, or moral state.
(statistical mechanics)
A phenomenon which occurs in gases at very low temperatures when the molecular heat drops to less than ³⁄₂ the gas constant.
References in periodicals archive ?
KEY WORDS: Benign Uterine Tumor, Cystic Degeneration, Leiomyoma, Ovarian Tumor.
Neoplastic mimickers of characteristic features of TB spondylitis TB spondylitis characteristi Neoplastic mimicker Pre/paravertebral abscess Ewing's cystic degeneration (4) Rim enhancement of abscess Cystic neuroblastoma/Ewing's (5,4) Extension beyond level of Neuroblastoma (5) bone destruction Multifocal Neurofibromatosis, (8) neuroblastoma (5) Disc involvement Metastases (3)
In this report, a case of plexiform ameloblastoma undergoing cystic degeneration which was clinically and radiographically misdiagnosed as periapical lesion is presented.
1,14,21,22) Typically the degree of cystic degeneration is greater in larger tumours, while small SPENs may appear entirely solid.
It has been hypothesized that cervical thymic cysts occur as a result o f cystic degeneration of Hassall corpuscles or cystic changes in remnants of the thymopharyngeal ducts.
The leiomyosarcomas were more likely to have areas of hemorrhagic necrosis and cystic degeneration.
As was evident on cytology, the most common lesion on histopathology also proved to be a follicular adenoma with varying amount of haemorrhage, cystic degeneration, and calcification.
However, a large central part of the mass remained hypodense with no contrast uptake, which was attributed to huge cystic degeneration of the mass (Figure 2C).
Additionally, on CT a schwannoma that has undergone cystic degeneration will appear as a multilocular cystic structure with multiple, fine septations and solid areas, along with calcifications within the cyst walls.
8] In addition, lesions larger than 12 cm may have cystic degeneration and hemorrhagic areas in 17% and 27% of cases, respectively.
In contrast cystic degeneration, calcification and necrosis are more common in larger syndromic islet cell tumors such as Glucagonomas, Vipomas and nonfunctional islet cell tumors.