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an instrument for weighing.
equilibrium (def. 1).
acid-base balance see acid-base balance.
analytical balance a balance used in the laboratory, sensitive to variations of the order of 0.05 to 0.1 mg.
fluid balance see fluid balance.
negative balance a state in which the amount of water or an electrolyte excreted from the body is greater than that ingested.
nitrogen balance see nitrogen balance.
positive balance a state in which the amount of water or an electrolyte excreted from the body is less than that ingested.
water balance fluid balance.
zero balance a state in which the amount of water or an electrolyte excreted from the body is exactly equal to that ingested; see equilibrium (def. 1).
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.
the difference between the total nitrogen intake by an organism and its total nitrogen loss. A zero nitrogen balance is seen in normal, healthy adults; Nin > Nout is a positive nitrogen balance and Nin < Nout is a negative nitrogen balance.
The difference between the amount of nitrogen ingested by an animal or taken in by the soil and the amount excreted or lost.
the relationship between the amount of nitrogen taken into the body, usually as food, and that excreted from the body in urine and feces. Most of the body's nitrogen is incorporated into protein. Positive nitrogen balance, which occurs when the intake of nitrogen is greater than its excretion, implies tissue formation and growth. Negative nitrogen balance, which occurs when more nitrogen is excreted than is taken in, indicates wasting or destruction of tissue.
nitrogen balanceA measure of the nitrogen released by an organism, minus the nitrogen absorbed or ingested. A crude indicator of nutritional adequacy is the amount of protein lost in the urine in a 24-hour period, which is calculated by urinary excretion of nitrogen products produced by the urea cycle. Usually, 0.5 g/kg of dietary protein is adequate to maintain an adequate nitrogen balance.
A positive balance is typical of growth periods (i.e., in the young), in pregnancy and in convalescence from burns; in a negative nitrogen balance, the loss of nitrogen exceeds intake, as occurs in ageing, burns, serious injuries and protein-losing enteropathy.
In the induction phase of chemotherapy, a “physiologic” negative balance occurs due to massive lysis of malignant cells.
ni·tro·gen bal·ance(nī'trŏ-jĕn bal'ăns)
The difference between the total nitrogen intake by an organism and its total nitrogen loss. A normal, healthy adult has a zero nitrogen balance.
nitrogen balanceThe difference between the amounts of nitrogen taken into and lost by the body. Nitrogen is taken in mainly in the form of protein and is mainly lost in urea in the urine.
nitrogen balanceexists when nitrogen intake (in protein) equals nitrogen excretion. In positive nitrogen balance intake exceeds excretion, with the additional protein used to synthesize new tissues. This is required in growing children, during pregnancy, in recovery from illness and during resistance exercise training when overloading of muscle cells promotes protein synthesis. In negative nitrogen balance output is greater than intake, indicating that protein (primarily from skeletal muscle) is being used for energy. This occurs on starvation diets and those with low protein and carbohydrate intake; it reduces the lean tissue mass and is detrimental to exercise performance.
ni·tro·gen bal·ance(nī'trŏ-jĕn bal'ăns)
The difference between the total nitrogen intake by an organism and its total nitrogen loss.
n a determination made about the body's ability to meet its protein needs which is reached by comparing the amount of nitrogen taken in with the amount discharged via urine, hair, skin, or perspiration.
nitrogen balance, negative,
n a condition in which nitrogen output exceeds nitrogen intake, resulting in the body's need to draw on its own stores of protein for energy; may be caused by dietary imbalances, illness, infection, anxiety, or stress.
nitrogen balance, positive,
n a body condition in which nitrogen intake exceeds nitrogen output; a normal state for children, pregnant women, or individuals recovering from illness or surgery, whose bodies require extra protein in order to build tissue.
1. an instrument for weighing.
2. harmonious adjustment of different elements or parts; harmonious performance of functions. Used to describe symmetry and proportion of conformation.
the proportion of acid and base required to keep the blood and body fluids neutral. See also acid-base balance.
a laboratory balance sensitive to very small variations of the order of 0.001 mg.
simultaneous palpation of muscles on both sides of the body of Greyhounds attempting to locate areas of soreness or spasm.
the state of the body in relation to ingestion and excretion of water and electrolytes (see also fluid balance).
the state of the body in regard to ingestion and excretion of nitrogen. In negative nitrogen balance the amount of nitrogen excreted is greater than the quantity ingested. In positive nitrogen balance the amount excreted is smaller than the amount ingested. See also nitrogen balance.
disturbances of balance, including falling to one side, rotation of the head, walking in circles. These are usually indications of disturbances of the organs of balance in the semicircular canals.
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.
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.
see nitric oxide.
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.
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.
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.