1. One; a single person or thing. 2. A standard of measure, weight, or any other quality, by multiplications or fractions of which a scale or system is formed. 3. A group of persons or things considered as a whole because of mutual activities or functions. SEE ALSO: international u.. [L. unus, one]
- absolute u. a u. whose value is constant regardless of place or time and not derived from or dependent on gravitation.
- alexin u. SYN: complement u..
- Allen-Doisy u. the quantity of estrogen capable of producing in a spayed mouse a characteristic change in the vaginal epithelium, namely, disappearance of leukocytes and appearance of cornified cells, as determined by a vaginal smear; equal approximately to one-half of an estrone u.. SYN: mouse u..
- alpha units cytoplasmic glycogen granules arranged in rosettes.
- amboceptor u. SYN: hemolysin u..
- androgen u. (international) the androgenic activity of 100 μg (0.1 mg) of crystalline androsterone as assayed by the comb growth response in capons.
- Ångström u. (Å) Ångström.
- antigen u. the smallest amount of antigen that, in the presence of specific antiserum, will fix 1 complement u..
- antitoxin u. a u. expressing the strength or activity of an antitoxin; in general, determined with reference to a preserved standard preparation of antitoxin. SEE ALSO: L doses, under dose.
- antivenene u. the amount of antivenum which, injected in the ear vein, will protect 1 g weight of rabbit against a fatal dose of snake venom.
- atomic mass u. (amu) a u. of mass by definition equal to 112 of the mass of an atom of carbon-12, which equals 1.6605402 × 10−27 kg; in terms of energy, 1 amu equals 931.49432 MeV. Cf.:dalton.
- base units the fundamental units of length, mass, time, electric current, thermodynamic temperature, amount of substance, and luminous intensity in the International System of Units (SI); the names and symbols of the units for these quantities are meter (m), kilogram (kg), second (s), ampere (A), kelvin (K), mole (mol), and candela (cd). SEE ALSO: International System of Units.
- Bethesda u. a measure of inhibitor activity : the amount of inhibitor that will inactivate 50% or 0.5 u. of a coagulation factor during the incubation period. [Bethesda, MD]
- biological standard u. a specific quantity of biologically active reference material (antibiotic, antitoxin, enzyme, hormone, vitamin, etc.).
- bird u. a u. of prolactin activity : the minimal quantity of the hormone which will cause a certain increase in weight of the crop gland of pigeons.
- Bodansky u. that amount of phosphatase that liberates 1 mg of phosphorus as inorganic phosphate during the first hour of incubation with a buffered substrate containing sodium β-glycerophosphate.
- British thermal u. (BTU) the quantity of heat required to raise 1 lb of water from 3.9°C to 4.4°C; equal to 251.996 calorie or 1055.056 J. SYN: u. of heat (2).
- capon u. amount of androgen needed to produce an increase in the capon comb surface of 20%. SYN: capon-comb u..
- capon-comb u. SYN: capon u..
- cat u. the dose of a drug (per kilogram of body weight of cat) which is just large enough to kill a cat when administered intravenously; was applied in the standardization of digitalis materials.
- centimeter-gram-second u., CGS u., cgs u. an absolute u. of the centimeter-gram-second system.
- chlorophyll u. the number of chlorophyll molecules required to reduce one molecule of carbon dioxide by photosynthesis.
- chorionic gonadotropin u. (international) the specific gonadotropic activity of 0.1 mg of the standard preparation of chorionic gonadotropin originating from the urine or placentas of pregnant women.
- Clauberg u. Clauberg test.
- colony-forming u. a u. of cells in bone marrow capable of generating or increasing the proliferation of new blood cells.
- complement u. the smallest amount (highest dilution) of complement that will cause hemolysis of a u. of red blood cells in the presence of a hemolysin u.. SYN: alexin u..
- Corner-Allen u. a u. of progestational activity, measured in rabbits; the minimum dose which, divided into five equal daily portions, produces on the sixth day the uterine changes characteristic of the eighth day of normal pregnancy; the u. has about the same potency as the international u..
- coronary care u. (CCU) a group of beds within a hospital set aside for the care of patients having or suspected of having myocardial infarction.
- corpus luteum hormone u. SYN: progesterone u..
- critical care u. (CCU) SYN: intensive care u..
- CT u. a u. of x-ray attenuation in each picture element of the CT image. See Hounsfield u..
- Dam u. a u. of activity of vitamin K; the smallest amount of vitamin K, per gram of chick per day, capable of producing normal coagulability in the blood of K-avitaminotic chicks after 3 days of oral administration.
- digitalis u. (international) the activity of 0.1 g of the international standard powdered digitalis.
- dog u. the amount of adrenal cortical extract per kilogram of body weight which, given daily, will maintain an adrenalectomized dog in good condition for 7–10 days.
- electromagnetic u. (emu) the u. in an absolute system (CGS) of units utilizing the magnetic effects of current; e.g., abampere, abfarad, abhenry, abohm, abvolt.
- electrostatic u. (esu) the u. in an absolute system (CGS) of units utilizing static electricity; e.g., statampere, statcoulomb, statfarad, stathenry, statvolt.
- u. of energy 1. CGS system : erg, joule; 2. MKS system : newton-meter (joule); 3. FPS system : foot-poundal; 4. gravitational u.: gram-centimeter, gram-meter, kilogram-meter, foot-pound; 5. SI: joule.
- epidermal-melanin u. an association of one melanocyte with several surrounding epidermal keratinocytes, presumably one that favors the transfer of melanin granules from the melanocyte to the keratinocytes.
- equine gonadotropin u. (international) the specific gonadotropic activity of 0.25 mg of standard preparation of the gonadotropic principle of pregnant mares' serum.
- estradiol benzoate u. (international) the estrogenic activity of 0.1 μg of a standard preparation of estradiol benzoate.
- estrone u. (international) the estrogenic activity of 0.1 μg (0.0001 mg) of a standard preparation of crystalline estrone.
- Fishman-Lerner u. a u. of serum acid phosphatase activity based upon measurement of the amount of phenol released from a phenylphosphate substrate.
- Florey u. SYN: Oxford u..
- foot-pound-second u., FPS u., fps u. an absolute u. of the foot-pound-second system.
- u. of force 1. CGS system : dyne; 2. FPS system : poundal; 3. MKS system and SI: newton.
- gravitational units (G) of energy : gram-centimeter, gram-meter, kilogram-meter, and foot-pound.
- G u. of streptomycin streptomycin units.
- u. of heat 1. calorie (gram calorie; kilocalorie); 2. SYN: British thermal u.. 3. SYN: joule.
- hemolysin u., hemolytic u. the smallest quantity (highest dilution) of inactivated immune serum (hemolysin) that will sensitize the standard suspension of erythrocytes so that the standard complement will cause complete hemolysis. SYN: amboceptor u..
- heparin u. the quantity of heparin required to keep 1 ml of cat's blood fluid for 24 hours at 0°C; it is equivalent approximately to 0.002 mg of pure heparin. SYN: Howell u..
- Holzknecht u. (H) an obsolete u. of x-ray dosage equal to one-fifth of the erythema dose.
- Hounsfield u. a normalized index of x-ray attenuation based on a scale of -1000 (air) to +1000 (bone), with water being 0; used in CT imaging.
- Howell u. SYN: heparin u..
- insulin u. (international) the activity contained in 122 mg of the international standard of zinc-insulin crystals.
- intensive care u. (ICU) a hospital facility for provision of intensive nursing and medical care of critically ill patients, characterized by high quality and quantity of continuous nursing and medical supervision and by use of sophisticated monitoring and resuscitative equipment; may be organized for the care of specific patient groups, e.g., neonatal or newborn ICU, neurologic ICU, pulmonary ICU. SYN: critical care u..
- u. of intermedin a u. based upon the action of the hormone in causing the expansion of the melanophores in a hypophysectomized frog; equal to 1 μg of alkali-treated USP Posterior-pituitary Reference Standard.
- international u. (IU) the amount of a substance, such as a drug, hormone, vitamin, enzyme, etc., that produces a specific effect as defined by an international body and accepted internationally; e.g., for an enzyme it is micromoles of product formed (or substrate consumed) per minute.
- International System of Units International System of Units.
- Jenner-Kay u. that amount of phosphatase that liberates 1 mg of phosphorus; approximately 2 Bodansky units or 1 King u..
- Karmen u. a formerly used enzyme u. for aminotransferase activity; a change of 0.001 in the absorbance of NADH/min.
- Kienböck u. (X) an obsolete u. of x-ray dosage equivalent to 110 the erythema dose.
- King u. the quantity of phosphatase that, acting upon disodium phenylphosphate in excess, at pH 9 for 30 min, liberates 1 mg of phenol. SYN: King-Armstrong u..
- King-Armstrong u. SYN: King u..
- u. of length 1. metric system and SI: meter; 2. CGS system : centimeter; 3. variable in the English system : inch for short distances, foot for moderate distances and for elevation, mile for long distances.
- u. of light See candela, lux.
- L u. of streptomycin streptomycin units.
- lung u. 1. a respiratory bronchiole together with the alveolar ducts and sacs and pulmonary alveoli into which the respiratory bronchiole leads; 2. considered by some to include the terminal bronchiole and its subdivisions, and called a pulmonary acinus.
- u. of luteinizing activity (international) SYN: progesterone u..
- u. of mass 1. metric system : gram; 2. SI: kilogram; 3. English system : pound.
- meter-kilogram-second u., MKS u., mks u. an absolute u. of the meter-kilogram-second system.
- Montevideo units a measure of uterine contraction intensity in labor expressed as the sum of the intensity of each contraction within a 10-min period, with intensity defined as the peak pressure achieved by the contraction minus the baseline tone. [from Montevideo, Argentina, where developed]
- motor u. a single somatic motor neuron and the group of muscle fibers innervated by it.
- mouse u. (m.u.) SYN: Allen-Doisy u..
- u. of ocular convergence SYN: meter angle.
- ostiomeatal u. SYN: ostiomeatal complex.
- Oxford u. the minimum amount of penicillin which will prevent the growth of Staphylococcus aureus over an area 26 mm in diameter in a standard culture medium; 1 u. equals 0.6 μg of crystalline sodium salt of penicillin. SYN: Florey u..
- u. of oxytocin the oxytocic activity of 0.5 mg of the USP Posterior-pituitary Reference Standard; 1 mg of synthetic oxytocin corresponds to 500 IU.
- u. of penicillin (international) the penicillin activity of 0.6 μg of penicillin G.
- physiologic u. 1. the ultimate (hypothetical) vital u. of protoplasm, as conceived by Spencer; 2. the smallest division of an organ that will perform its function; e.g., the uriniferous tubule.
- practical units units of magnitudes convenient for use in the practical applications of electricity; as originally defined they were absolute units (multiples of CGS electromagnetic units); they include the ampere, coulomb, farad, henry, joule, ohm, volt, and watt.
- u. of progestational activity (international) progesterone u..
- progesterone u. (international) the progestational activity of 1 mg of u. of progestational activity (international); standard preparation of pure progesterone. SEE ALSO: Clauberg test, Corner-Allen u.. SYN: corpus luteum hormone u., u. of luteinizing activity.
- prolactin u. (international) the specific lactogenic activity contained in 0.1 mg of the standard preparation of the lactogenic substance of the anterior pituitary gland.
- riboflavin u. potency usually expressed in terms of weight of pure riboflavin. SEE ALSO: Sherman-Bourquin u. of vitamin B2. SYN: vitamin B2 u..
- Schwann cell u. a single Schwann cell and all of the axons lying in troughs indenting its surface; this u. is regarded as an unmyelinated fiber in the peripheral nervous system.
- Sherman u. u. of vitamin C, minimum protective dose; the minimum amount of vitamin C which, fed daily, will protect a 300-g guinea pig from scurvy for 90 days; equivalent to 0.5–0.6 mg of ascorbic acid.
- Sherman-Bourquin u. of vitamin B2 the amount of vitamin B2 required in the diet daily to sustain an average weekly gain of 3 g for 8 weeks in standard test rats; one u. is equivalent to 1–7 μg (0.001–0.007 mg) of riboflavin, depending on the deficiency diet used in the above assay.
- Sherman-Munsell u. a rat growth u.; the daily amount of vitamin A which sustains a rate of gain amounting to 3 g a week in standard test rats.
- Somogyi u. a measure of the level of activity of amylase in blood serum, as analyzed by means of the Somogyi method (the most frequently used procedure); one u. is equivalent to 1 mg of reducing sugar liberated as glucose per 100 ml of serum, when an aliquot of the latter is mixed with a standard starch substrate (plus sodium chloride for maximal activation) and incubated for a standard time; normal range is 80–150 units, but values are usually not regarded as clinically significant unless they are greater than 200.
- S u. of streptomycin streptomycin units.
- Steenbock u. a u. of vitamin D; the total amount of vitamin D which will produce within 10 days a narrow line of calcium deposit in the rachitic metaphyses of the distal ends of the radii and ulnae of standard rachitic rats.
- streptomycin units 1. G u.: equals 1 g of the crystalline material or about 1,000,000 S units; 2. L u.: equal to 1000 S units; 3. S u.: the amount of streptomycin which will inhibit the growth of a standard strain of Escherichia coli in 1 mL of nutrient broth or other suitable medium.
- Svedberg u. (S) a sedimentation constant of 1 × 1013 s.
- terminal respiratory u. all alveoli and alveolar ducts beyond the most proximal respiratory bronchiole; contains about 100 alveolar ducts and 2000 alveoli.
- thiamin chloride u. thiamin hydrochloride u. (international).
- thiamin hydrochloride u. (international) the antineuritic activity of 0.003 mg of the standard crystalline vitamin B1 hydrochloride. SYN: vitamin B1 hydrochloride u..
- u. of thyrotrophic activity the activity of an amount of an extract of the anterior lobe of the hypophysis which, given daily for 5 days, will cause the thyroid of a guinea pig (weighing 200 g) to reach a weight of 600 mg.
- Todd u. the u. in which the results of testing for antistreptolysin O (ASO) are expressed. It denotes the reciprocal of the highest dilution of test serum at which there continues to be neutralization of a standard preparation of the streptococcal enzyme streptolysin O.
- toxic u. (T.U.) a u. formerly synonymous with minimal lethal dose in guinea pig but which, because of the instability of toxins, is now measured in terms of the quantity of standard antitoxin with which the toxin combines. SEE ALSO: L doses, under dose, minimal lethal dose. SYN: toxin u..
- toxin u. (T.U.) SYN: toxic u..
- USP u. a u. as defined and adopted by the United States Pharmacopeia.
- u. of vasopressin the pressor activity of 0.5 mg of the USP Posterior-pituitary Reference Standard; 1 mg of synthetic vasopressin corresponds to 600 IU.
- vitamin A u. (international) the specific biologic activity of 0.3 μg of vitamin A (alcohol form). SEE ALSO: Sherman-Munsell u..
- vitamin B2 u. SYN: riboflavin u..
- vitamin B6 u. potency expressed in terms of weight of pure crystalline pyridoxine.
- vitamin C u. (international) the vitamin C activity of 0.05 mg of the standard crystalline levoascorbic acid; 1 mg of crystalline vitamin C provides 20 USP units. SEE ALSO: Sherman u..
- vitamin D u. (international) the antirachitic activity contained in 0.025 μg of a preparation of crystalline vitamin D3 (activated 7-dehydrocholesterol). SEE ALSO: Steenbock u..
- vitamin E u. potency usually expressed in terms of weight of pure α-tocopherol.
- vitamin K u. Dam u..
- volume u. (VU) a u. of a logarithmic scale for expressing the power level of a complex audio frequency electrical signal, such as that transmitting music or speech; the power in volume units equals the decibels of power above a reference level of one milliwatt, as measured with an appropriate meter.
- u. of wavelength See Ångström, nanometer.
- u. of weight u. of mass.
- Wood units a simplified measurement of pulmonary vascular resistance that uses pressures instead of more complicated units measured by subtracting pulmonary capillary wedge pressure from the mean pulmonary arterial pressure and dividing by cardiac output in liters per minute.
- u. of work u. of energy.

* * *

unit 'yü-nət n
1) an amount of a biologically active agent (as a drug or antigen) required to produce a specific result under strictly controlled conditions <a \unit of penicillin> see international unit
2) a small molecule esp. when combined in a larger molecule <repeating \units of a polymer>
3) an area in a medical facility and esp. a hospital that is specially staffed and equipped to provide a particular type of care <an intensive care \unit>

* * *

(uґnit) [L. unus one] 1. a single thing. 2. a quantity assumed as a standard of measurement. Symbol U.

Medical dictionary. 2011.

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