Medical Dictionary

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nitrochloroform (ni-tro-klor′o-form)
SYN: chloropicrin.

nitrofurans (ni-tro-fu′ranz)
Antimicrobials ( e.g., nitrofurazone) effective against Gram-positive and Gram-negative organisms.

nitrofurantoin (ni′tro-fu-ran′to-in)
A urinary antibacterial agent with a wide range of activity against both Gram-positive and Gram-negative organisms; also available as n. sodium for injection.

nitrofurazone (ni-tro-fu′ra-zon)
A topical bacteriostatic and bactericidal agent often used in burns.

nitrogen (N) (ni′tro-jen)
1. A gaseous element, atomic no. 7, atomic wt. 14.00674; N2 forms about 78.084% by volume of the dry atmosphere. 2. The molecular form of n., N2. 3. Pharmaceutical grade N2, containing not less than 99.0% by volume of N2; used as a diluent for medicinal gases, and for air replacement in pharmaceutical preparations. [L. nitrum, niter, + -gen, to produce] blood urea n. (BUN) n., in the form of urea, in the blood; the most prevalent of nonprotein nitrogenous compounds in blood; blood normally contains 10–15 mg of urea/100 mL. Measurements in the laboratory are commonly used as a measure of renal function. SEE ALSO: urea n.. filtrate n. nonprotein n. in various compounds that normally pass through the glomerular filtration or through a filter in the laboratory (after proteins are precipitated). heavy n. SYN: n.-15. n. monoxide SYN: nitrous oxide. nonprotein n. (NPN) the n. content of other than protein bodies; e.g., about one-half the nonprotein n. in the blood is contained in urea. SYN: rest n.. rest n. SYN: nonprotein n.. undetermined n. the n. of blood, urine, etc., other than urea, uric acid, amino acids, etc., that can be directly estimated; in blood it amounts to about 25 mg/100 mL. urea n. the portion of n. in a biologic sample, such as blood or urine, that derives from its content of urea. SEE ALSO: blood urea n.. urinary n. n. excreted as urea, amino acids, uric acid, etc., in the urine; 1 g of urinary n. indicates the breakdown in the body of 6.25 g of protein. SEE ALSO: n. equivalent.

nitrogen-13 (13N)
A cyclotron-produced, positron-emitting radioisotope of nitrogen with a half-life of 9.97 minutes; used in protein metabolism studies and in positron-emission tomography.

nitrogen-14 (14N)
The common nitrogen isotope, making up 99.63% of natural nitrogen.

nitrogen-15 (15N)
The less common stable nitrogen isotope, making up 0.37% of natural nitrogen. SYN: heavy nitrogen.

nitrogenase (ni′tro-je-nas)
Formerly a general term used to describe enzyme systems that catalyze the reduction of molecular nitrogen to ammonia in nitrogen-fixing bacteria; now specifically applied to enzymes that carry out this reaction with reduced ferredoxin and ATP; typically n. consists of two components, the first of which reduces N2 while the second transfers electrons.

nitrogen distribution
SYN: nitrogen partition.

nitrogen group
Five trivalent or quinquivalent elements whose hydrogen compounds are basic and whose oxyacids vary from monobasic to tetrabasic: nitrogen, phosphorus, arsenic, antimony, and bismuth.

nitrogen lag
The length of time after the ingestion of a given protein before the amount of nitrogen equal to that in the protein has been excreted in the urine.

nitrogenous (ni-troj′e-nus)
Relating to or containing nitrogen.

nitrogen partition
Determination of the distribution of nitrogen in the urine among the various constituents. SYN: nitrogen distribution.

nitroglycerin (ni-tro-glis′er-in)
An explosive yellowish oily fluid formed by the action of sulfuric and nitric acids on glycerin; used as a vasodilator, especially in angina pectoris; generates nitric oxide. SYN: glyceryl trinitrate, trinitroglycerin.

nitrohydrochloric acid (ni′tro-hi-dro-klor′ik)
An extremely caustic mixture that contains 18 parts nitric acid and 82 parts hydrochloric acid. SYN: aqua regia, aqua regalis, nitrimuriatic acid.

nitromannitol (ni-tro-man′i-tol)
SYN: mannitol hexanitrate.

nitromersol (ni-tro-mer′sol)
The anhydride of 4-nitro-3-hydroxymercuriorthocresol; a synthetic organic mercurial compound, used as an antiseptic for skin and mucous membranes.

nitrometer (ni-trom′e-ter)
A device for collecting and measuring the nitrogen set free in a chemical reaction. [nitrogen + G. metron, measure]

nitron (ni′tron)
A reagent for the determination of nitric acid, perchlorate, and rhenium, as it is one of the few substances to form an insoluble nitrate.

nitrophenylsulfenyl (Nps) (ni′tro-fen′il-sul-fen′il)
O2N–C6H4–S–; nitrophenylthio;a radical easily attached to amino groups; used in peptide synthesis and protein chemistry.

nitroprusside (ni-tro-prus′id)
The anion [Fe(CN)5NO]&dbond;; as in sodium n.; used as a vasodilator by the intravenous route.

nitrosamines (ni-tros′am-enz)
Amines substituted by a nitroso (NO) group, usually on a nitrogen atom, to yield N-n. (R–NH–NO or R2N–NO); can be formed by direct combination of an amine and nitrous acid (can be formed from nitrites in the acidic gastric juice); some are mutagenic and/or carcinogenic.

nitroso-
Prefix denoting a compound containing nitrosyl. [L. nitrosus]

nitrosourea (ni-tro′so-oor′e-a)
Alkylating agent used in the treatment of many neoplasms; an example is BCNU [N,N′-bis(2-chloroethyl)-N-n.; carmustine].

nitrosyl (ni′tro-sil)
A univalent radical or atom group, –N&dbond;O, forming the nitroso compounds.

nitrous (ni′trus)
Denoting a nitrogen compound containing one less atom of oxygen than the nitric compounds; one in which the nitrogen is present in its trivalent state.

nitrous acid
HNO2;a standard biologic and clinical laboratory reagent.

nitrous oxide
N2O;a nonflammable, nonexplosive gas that will support combustion; widely used as a rapidly acting, rapidly reversible, nondepressant, and nontoxic inhalation analgesic to supplement other anesthetics and analgesics; its anesthetic potency alone is inadequate to provide surgical anesthesia. SYN: dinitrogen monoxide, nitrogen monoxide.

nitroxanthic acid (ni-tro-zan′thik)
SYN: picric acid.

nitroxoline (ni-trok′so-len)
An antibacterial agent.

nitroxy (ni-trok′se)
The –O–NO2 radical. [contraction of nitryloxy]

nitroxyl (ni-trok′sil)
The nitrosyl hydride, HNO.

nitryl (ni′tril)
The radical –NO2 of the nitro compounds.

nizatidine (ni-zat′i-den)
A histamine H2 antagonist used to treat active duodenal ulcers.

njovera (nyo-ver′a)
A nonvenereal disease of children in Zimbabwe, indistinguishable from syphilis, due to an organism apparently identical with Treponema pallidum; probably the same as bejel. [Zimbabwean]

N.K.
Abbreviation for Nomenklatur Kommission.

nkat
Abbreviation for nanokatal.

Nle
Abbreviation for norleucine.

NLN
Abbreviation for National League for Nursing.

nM
Abbreviation for nanomolar.

nm
Abbreviation for nanometer.

NMDA
Abbreviation for N-methyl d-aspartate; excitotoxic amino acid used to identify a specific subset of glutamate (an excitatory amino acid) receptors. SYN: N-methyl d-aspartic acid.

NMN
Abbreviation for nicotinamide mononucleotide.

NMP
Abbreviation for nucleoside 5′-monophosphate.

NMR
Abbreviation for nuclear magnetic resonance.

NO&chmpnt;
Symbol for nitric oxide.

No
Symbol for nobelium.

Noack
M., 20th century German physician. See N. syndrome.

nobelium (No) (no-bel′e-um)
An unstable transuranium element, atomic no. 102, prepared by bombardment of curium with carbon-12 nuclei and similar heavy ions on other elements of the transuranium series. [Nobel Institute for Physics and A.B. Nobel, Swedish inventor, 1833–1896]

Noble
Charles P., U.S. gynecologist, 1863–1935. See N. position.

Noble
Robert L., Canadian physiologist, *1910. See N.-Collip procedure.

Noble stain
See under stain.

Nocard
Edmund I.E., French veterinarian, 1850–1903. See Nocardia, Nocardiaceae.

Nocardia (no-kar′de-a)
A genus of aerobic actinomycetes (family Nocardiaceae, order Actinomycetales), higher bacteria, containing weakly acid-fast, slender rods or filaments, frequently swollen and occasionally branched, forming a mycelium. Coccus or bacillary forms are produced by these organisms, which are mainly saprophytic but may be a cause of mycetoma or nocardiosis. [E. Nocard] Nocardia asteroides a species of aerobic, Gram-positive, partially acid-fast, branching organisms causing nocardiosis and possibly mycetoma in humans. Nocardia brasiliensis a bacterial species that closely resembles Nocardia asteroides and is a cause of mycetoma and nocardiosis in humans. Nocardia caviae former name for Nocardia otitidiscaviarum. Nocardia farcinica a species causing bovine farcy; it is the type species of the genus Nocardia. Nocardia gibsonii SYN: Streptomyces gibsonii. Nocardia lurida former name for Amycolatopsis orientalis lurida. Nocardia madurae former name for Actinomadura madurae. Nocardia mediterranei a bacterial species that produces rifamycin. Nocardia nova a bacterial species commonly recovered from human infections. Nocardia orientalis a bacterial species that produces vancomycin. Nocardia otitidiscaviarum a higher bacteria (formerly Nocardia caviae) living in soil and one of the causes of nocardiosis and actinomycetoma. Nocardia transvalensis an aerobic actinomycete; a cause of nocardiosis.

nocardia, pl .nocardiae (no-kar′de-a, no-kar′de-e)
A vernacular term used to refer to any member of the genus N..

Nocardiaceae (no-kar-de-a′se-e)
A family of acid-fast, Gram-positive, aerobic bacteria (order Actinomycetales) that includes the genus Nocardia. [E. Nocard]

nocardiasis (no-kar-di′a-sis)
SYN: nocardiosis.

nocardioform (no-kar′de-o-form)
Denoting an organism that morphologically and culturally resembles members of the genus Nocardia.

Nocardiopsis (no-kar-de-op′sis)
A genus of higher bacteria living in soil that cause subacute or chronic pneumonia, subcutaneous infection, or disseminated disease, usually in immunosuppressed patients. N. dassonvillei an aerobic actinomycete, formerly Nocardia dassonvillei; a cause of actinomycetoma.

nocardiosis (no-kar-de-o′sis)
A generalized disease in humans and other animals caused by Nocardia asteroides, N. otitidiscaviarum, N. transvalensis, and N. brasiliensis and characterized by primary pulmonary lesions that may be subclinical or chronic with hematogenous spread, to deep viscera, including the central nervous system; most commonly occurs in immunosuppressed patients. SYN: nocardiasis. granulomatous n. a form of n. characterized by emaciation, abdominal distention, and replacement of lymphoid tissue in lymph nodes and spleen by granulomatous tissue.

nocebo (no-se′bo)
An unpleasant effect attributable to administration of a placebo; jargon. [L. I shall harm, fr. noceo, to harm, by analogy with placebo, I shall please]

noci-
Hurt, pain, injury. [L. noceo]

nociceptive (no-si-sep′tiv)
Capable of appreciation or transmission of pain. [see nociceptor]

nociceptor (no-si-sep′ter, -tor)
A peripheral nerve organ or mechanism for the reception and transmission of painful or injurious stimuli. [noci- + L. capio, to take]

nocifensor (no-si-fen′ser)
Denoting processes or mechanisms that act to protect the body from injury; specifically, a system of nerves in the skin and mucous membranes that react to adjacent injury by causing vasodilation. [noci- + L. fendo (only in compounds), to strike, ward off]

noct-
Nocturnal. SEE ALSO: nycto-. [L. nox, night]

noctalbuminuria (nok′tal-boo′mi-nu′re-a)
A pathologic increase of albumin in urine excreted during the evening, a rarely observed event. [L. nox, night, + albuminuria]

noctiphobia (nok′te-fo′be-a)
Morbid dread of night and its darkness and silence. [noct- + phobia]

noct. maneq.
Abbreviation for L. nocte maneque, at night and in the morning.

noctograph (nok′to-graf)
SYN: scotograph. [noct- + G. grapho, to write]

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