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subsidence

(sŭb-sīd′ĕns) [L. subsidere, to sink down] The gradual disappearance of symptoms or manifestations of a disease.

subsistence

1. The minimum amount of something essential for life, e.g., a subsistence diet. 2. Any means of barely supporting life.

subspecies

(sŭb″spē′sēz, sŭb″spē′shēz) In taxonomy, a category below a species.

substage

(sŭb′stāj) [″ + O.Fr. estage, position] The part of the microscope below the stage by which attachments are held in place.

substance

(sŭb′stăns) [L. substantia, being, essence, contents] 1. Material; matter. 2. Substantia. 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 s. The portion of the rhinencephalon lying immediately anterior to the optic chiasm. It is perforated by numerous small arteries.

chromophilic s. 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.

colloid s. A jelly-like substance in colloid degeneration.

ground s. The matrix or intercellular substance in which the cells of an organ or tissue are embedded.

high threshold s. 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.

ketogenic s. A substance that, in its metabolism, gives rise to ketone bodies.

low threshold s. 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.

Nissl s. SEE: under Nissl, Franz.

posterior perforated s. A triangular area forming the floor of the interpeduncular fossa. It lies immediately posterior to the mammillary bodies and contains numerous openings for blood vessels.

pressor s. A substance that elevates arterial blood pressure.

reticular s. The skein of threads present in some red blood cells. These are visible only when the cells are appropriately stained.

substance dependence disorder

An addictive disorder of compulsive drug use. It is marked by a cluster of behavioral and physiological symptoms that indicate continual use of the substance despite significant related problems. Patients develop a tolerance for the substance and require progressively greater amounts to elicit the effects desired. In addition, patients experience physical and psychological signs and ...

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