Degeneration(redirected from wallerian degeneration)
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(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.
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.