nitrogen (redirected from nitrogen washout test)

nitrogen /ni·tro·gen/ (N) (ni´tro-jen) a chemical element, at. no. 7. It forms about 78 per cent of the atmosphere and is a constituent of all proteins and nucleic acids.

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nitrogen 13  a radioactive isotope of nitrogen having a half-life of 9.97 minutes and decaying by positron emission (1.190 MeV); used as a tracer in positron emission tomography.

nitrogen mustard  see under mustard.

nonprotein nitrogen  the nitrogenous constituents of the blood exclusive of the protein bodies, consisting of the nitrogen of urea, uric acid, creatine, creatinine, amino acids, polypeptides, and an undetermined part known as rest nitrogen.

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ni·tro·gen (ntr-jn)

n. Symbol N

A nonmetallic element that constitutes nearly four fifths of the air by volume, occurring as a colorless, odorless, almost inert diatomic gas, N₂, in various minerals and in all proteins. Atomic number 7.

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Nitrogen

A gaseous element that makes up the base pairs in DNA.

Mentioned in: Gene Therapy

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nitrogen (N)

[nī′trəjən]

Etymology: Gk, nitron, soda, genein, to produce

a gaseous nonmetallic element. Its atomic number is 7; its atomic mass is 14.008. It exists as a diatomic molecule, N₂. Nitrogen constitutes approximately 78% of the atmosphere and is a component of all proteins and a major component of most organic substances in living cells. Nitrogen is essential to the synthesis of necessary proteins, particularly nitrogen-containing compounds or amino acids derived directly or indirectly from plant food. Nitrogen follows a cycle from atmospheric gas into nitrogen-fixing bacteria, into green vascular plants, into humans and animals, and, by decay or in excreted nitrogenous wastes, as urea, back into the soil. Denitrifying bacteria in the soil break down nitrogenous compounds and release gaseous nitrogen. During a 24-hour period in a healthy individual the nitrogen excreted in the urine, feces, and perspiration, together with the nitrogen retained in dermal structures, such as the skin and hair, equals the nitrogen consumed in food and drink. The process of protein metabolism accounts for this nitrogen balance. When protein catabolism exceeds protein anabolism, the amount of nitrogen in the urine exceeds the amount of nitrogen consumed in foods, producing a negative nitrogen balance or a state of tissue wasting. A positive nitrogen balance exists in the body when the nitrogen intake in foods is greater than that excreted in urine. Conditions usually associated with positive nitrogen balance include those related to growth, pregnancy, and convalescence from a tissue-wasting illness. nitrogenous, adj.

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nitrogen (N),

n a gaseous, nonmetallic element. Its atomic number is 7 and its atomic weight is 14.0067. It constitutes approximately 78% of the atmosphere and is a component of all proteins and a major component of most organic substances.

nitrogen monoxide,

n See nitrous oxide.

nitrogen monoxidum,

n See nitrous oxide.

nitrogen, nonprotein,

n See nonprotein nitrogen.

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nitrogen

a chemical element, atomic number 7, atomic weight 14.007, symbol N. See Table 6. It is a gas constituting about four-fifths of common air; chemically it is almost inert. It is not poisonous but is fatal if breathed alone because of oxygen deprivation. Nitrogen occurs in proteins and amino acids and is thus present in all living cells.

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nitrogen balance

the state of the body in regard to the rate of protein intake and protein utilization. When protein is metabolized, about 90% of the protein nitrogen is excreted in the urine in the form of urea, uric acid, creatinine and other nitrogen end products. The remaining 10% of the nitrogen is eliminated in the feces.

A negative nitrogen balance occurs when more protein is utilized by the body than is taken in. A positive nitrogen balance implies a net gain of protein in the body. Negative nitrogen balance can be caused by such factors as malnutrition, debilitating diseases, blood loss and glucocorticoids. A positive balance can be caused by exercise, growth hormone and testosterone.

blood urea nitrogen (BUN)

see urea nitrogen.

nitrogen dioxide

see nitric oxide.

nitrogen fixation

conversion of atmospheric nitrogen into organic nitrogenous compounds by bacteria which may be symbiotic, e.g. Rhizopus spp., which grow on the roots of legumes and put those plants in an advantageous position with respect to nonlegumes.

nitrogen-free extract (NFE)

consists of carbohydrates, sugars, starches, and a major portion of the hemicellulose in feeds. Calculated when crude protein, fat, water, ash, and the fiber are added and the sum is subtracted from 100.

nitrogen mustards

a group of toxic, blistering alkylating agents homologous to dichlorodiethyl sulfide (mustard gas), some of which have been used as antineoplastics. The group includes mustine hydrochloride, cyclophosphamide, thiotepa, chlorambucil and melphalan.

nonprotein nitrogen (NPN)

1. the nitrogenous constituents of the blood exclusive of the protein bodies, consisting of the nitrogen of urea, uric acid, creatine, creatinine, amino acids, polypeptides, and an undetermined part known as rest nitrogen.

Measurement of nonprotein nitrogen is used as a test of renal function, but has been largely replaced by measurement of specific substances, e.g. urea and creatinine.

2. also used in relation to feeds and refers to those nitrogen-containing constituents which are not proteins, e.g. nucleic acids, amino sugars, urea, etc.

nitrogen trichloride

see agene process.

nitrogen washout test

measures the rate at which the nitrogen concentration in the expired air is reduced when the horse is made to breathe pure oxygen. The rate is less in incompetent lungs, e.g. those affected by emphysema.