Necrobiosis

NECROBIOSIS (from Greek nekros - dead and bios - life), a term introduced in 1847 by Virchow to denote that form of local death of tissue and individual cells in which their demise does not occur immediately, as in rapidly developing necrosis (see), but rather through a gradual transition from life to death. This characteristic gradual dying of tissue elements in N. is based on various atrophic and degenerative processes, which with progressive development can ultimately lead to the death of tissue elements. Most often, N. is associated with simple atrophies, various degenerations and pathological infiltrations of tissue elements, especially with various forms of protein and fatty degeneration of them; similarly, disturbances in salt metabolism, disorders in the distribution and formation of pigments, and all exogenous deposits are important (though to a lesser degree), if these disorders are associated with decreased cellular vital activity and progressive destruction. The aforementioned processes, often referred to as necrobiotic, do not necessarily lead to the death of tissue elements, but may undergo reverse development with the cessation of the action of the harmful cause that produced them, with the tissue elements gradually passing into an orthobiotic state (orthobiosis - normal life). The morphological and physico-chemical characteristics of N. - see Atrophy, Protein degeneration, Vacuolar degeneration, Hyaline degeneration, Degeneration, Fatty degeneration, Cloudy swelling, Pigmentation, Mucoid degeneration. In all these processes, the sign of cell death is the disappearance of its nucleus by karyolysis or karyorrhexis (see Necrosis). The corresponding term in meaning to N., the rarely used Latin term mortificatio, is mostly used in the sense of necrosis.