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A common oxidation state of uranium (U +4 or U (IV)) with a quadruple positive charge.


(ū′ră-nĭl) The bivalent uranium radical UO2+ . It forms salts with many acids. An example is uranyl nitrate, UO2 (NO3)2.


(ū′rās) Urease.


(ū′rāt) [Gr. ouron, urine] The combination of uric acid with a base; a salt of uric acid.


(ŭr″bă-nis′ĭt-ē) The qualities that characterize a geographic area as a city. Characteristics include population density, industrialization, communication media, health care, educational infrastructure, social networks, and concentration of technology and services.

urban legend

(ŭr′băn) [L. urbanus] Myth (2). Urban legends about health care are widely disseminated by patients and practitioners. One favorite is the internet prank that states that dihydrogen monoxide is a deadly toxin widely consumed by human beings. Its chemical formula is H2O.

Most urban legends are not humorous or malicious pranks but are based on misunderstandings or unrecognized errors in reasoning, e.g., the common but false belief that emergency rooms are busiest during certain phases of the moon.


(ū-rē′ă) [Gr. ouron, urine] The diamide of carbonic acid, a crystalline solid having the formula CH4N2O; found in blood, lymph, and urine.

It is formed in the liver from ammonia derived from the deamination of amino acids.

Urea is the chief nitrogenous constituent of urine and, along with carbon dioxide, the final product of protein metabolism in the body. In normal conditions, urea represents 80% to 90% of the total urinary nitrogen. It is odorless and colorless, appears as white prismatic crystals, and forms salts with acids. The amount of urea excreted varies directly with the amount of protein in the diet. Its excretion is increased in fever, diabetes, or increased activity of the adrenal gland, and is decreased in kidney failure.

urea balance test

A test of kidney function performed by measuring intake and output of urea.

urea cycle disorder

ABBR: UCD. Any of six inherited disorders in which an enzyme in the urea cycle is missing or nonfunctional, resulting in the accumulation of excess ammonia in the bloodstream. Lethargy, failure to thrive, nausea and vomiting, encephalopathy, and coma are common symptoms, esp. in newborns.

urea frost

White flaky deposits of urea seen on the skin in patients with advanced uremia.


(ū-rē″ă-jĕn-ĕt′ĭk) [″ + genesis, generation, birth] Pert. to or producing urea.

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