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slow-·re·act·ing sub·stance (SRS),, slow-reacting substance of anaphylaxisSRS-A
a lipoprotein of low molecular weight composed of leukotrienes; it is released in anaphylactic shock and produces slower and more prolonged contraction of muscle than histamine does; it is active in the presence of antihistamines (but not epinephrine) and is newly generated after unpreformed mast cell generation; it induces the effect observed in anaphylactic reactions. Compare: peptidyl leukotrienes.
Synonym(s): slow-reacting factor of anaphylaxis
substance(sub'stans) [L. substantia]
1. Material; matter.
3. A chemical or drug.
4. When used in a medicolegal context, a chemical with potential for abuse. A great variety of entities are included: alcohol, nicotine, caffeine, sedatives, hypnotics, anxiolytics, and illicit drugs such as cannabis, heroin, or methamphetamines. Almost any substance may be abused even though its clinical use is approved when used as prescribed.
anterior perforated substance
The portion of the rhinencephalon lying immediately anterior to the optic chiasm. It is perforated by numerous small arteries.
black substanceSubstantia nigra.
A substance found in the cytoplasm of certain cells that stains similar to chromatin with basic dyes. It includes Nissl bodies of neurons and granules in serozymogenic cells.
Jelly-like substance in colloid degeneration.
An outdated term for the gray matter of the central nervous system.
The matrix or intercellular substance in which the cells of an organ or tissue are embedded.
high threshold substance
A substance such as glucose or sodium chloride present in the blood and excreted by the kidney only when its concentration exceeds a certain level.
A substance that, in its metabolism, gives rise to ketone bodies.
low threshold substance
A substance such as urea or uric acid that is excreted by the kidney from the blood almost in its entirety. It occurs in the urine in high concentrations.
An obsolete term for the inner part of an organ such as a bone.
Nissl substanceSee: Nissl, Franz
posterior perforated substance
A triangular area forming the floor of the interpeduncular fossa. It lies immediately behind the corpora mammillaria and contains numerous openings for blood vessels.
A substance that elevates arterial blood pressure.
The skein of threads present in some red blood cells. These are visible only when the cells are appropriately stained.
slow-reacting substanceSee: slow-reacting substance of anaphylaxis
a substance released in the anaphylactic reaction that induces slow, prolonged contraction of certain smooth muscles. So called because its effect is detected after the release and action of histamine; thought to be important in, for example, asthma. Symbol SRS or SRS-A. Called also leukotriene.