Hypostasis

hypostasis [hī′päs·tə·səs]

(medicine)

A condition involving settling of blood in dependent parts of an organ.

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Hypostasis 

suppression in the phenotype (that is, the structural and functional properties of an organism) of the expression of a given gene (hypostatic) by another gene or genes located in other sections of the chromosome or in other chromosomes (nonallelic genes). Genes that suppress the activity of hypostatic genes are called epistatic. In the crossing of genetically different organisms, hypostasis can cause a change in the correlation of characters in the second generation; in this, the nature of the change depends on whether the epistatic gene is dominant or recessive in relation to the hypostatic gene. If both genes are dominant, there is a separation in the ratio 12:3:1 in the second generation, instead of the usual separation of characters in the phenotype ratio 9:3:3:1 (Mendel’s law). For example, in oats, during the crossing of organisms that lack the dominant genes of the black (A) and gray (B) grain color, there will be only one gene A expressed in their offspring, which lack gene A and gene B. In such a case, the separation will have the formula 12 black: 3 gray: 1 white. In the case of recessiveness of epistatic and hypostatic genes, the separation will have the formula 9:3:4.

V. N. SOIFER

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Hypostasis 

an accumulation of blood in the capillary network of the lower parts of the body and individual organs.

Hypostasis during life is caused by cardiac insufficiency and develops because of venous congestion. Hypostasis arises in the lungs when a weakened patient is forced to remain supine for an extended period. Blood circulation deteriorates in the pulmonary system, there is an increased lack of oxygen, and hypostatic pneumonia often develops. Agonal hypostasis is observed during protracted dying as a result of the weakening of the heart’s activity. Cadaveric hypostasis appears three to six hours after death as violet or dark purple spots on the skin of the lower parts of the corpse because of the settling of the blood. The time of appearance and the intensity of these spots are of importance to forensic medicine in helping to ascertain the time and manner of death.

L. E. MANEVICH

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Hypostasis 

Originally a philosophical term introduced by the followers of Aristotle to signify the individual and the truly existing, the concept “hypostasis” was adopted by Christian theologians who were developing Christian dogmatics (it is not found in the New Testament). Until the fourth century it was synonymous with “essence.” After this, it acquired a new mean- ing in Christian dogma about the Trinity, signifying each person of the Trinity (according to Christian dogma, the Trinity consists of three hypostases).