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 ?
Bonaldo, "Role of macrophages in Wallerian degeneration and axonal regeneration after peripheral nerve injury," Acta Neuropathologica, vol.
U-fos expression, bFGF production, phagocytosis and proliferation during wallerian degeneration," Journal of Neuropathology and Experimental Neurology, vol.
Absence of Wallerian Degeneration does not Hinder Regeneration in Peripheral Nerve.
Schwann cells are believed to be an important factor in the regeneration process because peripheral axons have no function as [H.sub.2]S producers during Wallerian degeneration [12].
The SFI values were accelerated, cold and mechanical allodynia were suppressed, the severities of Wallerian degeneration and muscular atrophy were improved, and the increased MDA level was reversed with 10 consecutive days intraperitoneal injections of 0.2 and 0.8mg/kg of safranal and 100mg/kg of vitamin E.
Immediately after the injury, prior to completion of Wallerian degeneration, a nerve conduction study will demonstrate a conduction block at the site of the injury but continued conduction distally, due to the still functioning remaining axon.
Expression of neuregulins and their putative receptors, ErbB2 and ErbB3, is induced during Wallerian degeneration. J Neurosci 1997; 17: 1642-1659.
Wallerian degeneration (WD) refers to an anterograde degeneration of nerve fiber (s) distal to the injured neuronal cell body or proximal axon.
Sommer, "Wallerian degeneration after crush or chronic constriction injury of rodent sciatic nerve is associated with a depletion of endoneurial interleukin-10 protein," Experimental Neurology, vol.
When a peripheral nerve is sectioned, Wallerian degeneration occurs in the distal stump, where the axon disintegrates by proteolytic action of enzymes present in the axoplasm.
It facts by destroying nerves and producing Wallerian degeneration without disruption of the schwann cell sheath.
On the edge of the tumor, swollen axons (spheroids) and Wallerian degeneration of the preexisting nerve could be seen.