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.
Nitrogen
nitrogen (N)
nitrogen (N) [ni´tro-jen]
nitrogen (N),
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.
ni·tro·gen (n  tr -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. |
Nitrogen
A gaseous element that makes up the base pairs in DNA.
Mentioned in: Gene Therapy
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.
nitrogen (N) [ni´tro-jen]
a chemical element, atomic number 7, atomic weight 14.007. (See Appendix 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. It is soluble in the blood and body fluids, and can cause serious symptoms when released as bubbles of gas by rapid decompression (see bends). Nitrogen occurs in proteins and amino acids and is thus present in all living cells.
nitrogen 13 a radioactive isotope of nitrogen having a half-life of 9.97 minutes and decaying by positron emission; it is used as a tracer in positron emission tomography.
nitrogen balance the state of the body in regard to the rate of protein intake and protein utilization. When protein is metabolized, about 90 per cent of its nitrogen is excreted in the urine in the form of urea, uric acid, creatinine, and other nitrogen end-products. The remaining 10 per cent of the nitrogen is eliminated in the feces. A negative nitrogen balance occurs when more protein is used 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.
liquid nitrogen nitrogen in liquid form, i.e., below −195.79°C; used as a coolant, such as in thermographic equipment.
nitrogen mustards a group of toxic, blistering alkylating agents that are cell cycle phase nonspecific; it includes nitrogen mustard itself (mechlorethamine hydrochloride), chlorambucil, cyclophosphamide, ifosfamide, and melphalan. Some have been used as antineoplastic agents in certain forms of cancer; they do not cure these conditions, but ease their effects by destroying mitotic cells (those newly formed by division), thereby affecting malignant tissue in its early stage of development, and leaving normal tissue unaffected. They are especially useful in treatment of leukemia, in which they reduce the leukocyte count, and in cases in which the malignant disease is widespread throughout the body and therefore cannot be effectively treated locally by surgery or radiotherapy. In cases of lung cancer, mechlorethamine hydrochloride is usually injected directly into the lungs via the pulmonary circulation. Side effects, which tend to limit the usefulness of these drugs, include nausea, vomiting, and a decrease in bone marrow production.
nonprotein nitrogen (NPN) 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 this is used as a test of renal function, but has been largely replaced by measurement of specific substances, such as urea and creatinine.
nitrogen washout test a test for vital capacity of lungs; with the patient inhaling pure oxygen, the volume of exhaled nitrogen is obtained for each breath until it falls below 1 per cent of the gas being exhaled (usually about seven minutes' time); the total volume of nitrogen that has been exhaled at this point is assumed to be 0.8 of the vital capacity.
nitrogen washout test, single breath the patient inhales a vital capacity's volume of pure oxygen and then slowly exhales. The nitrogen content of the exhalation is measured over the entire breath and a curve is generated; different parts of the curve represent nitrogen concentrations of gas in different components of the total lung capacity, and can be analyzed for irregularities. Called also single breath test.
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.
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.
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.
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