β /β/ (beta, the second letter of the Greek alphabet) β chain of hemoglobin.
beta /be·ta/ (ba´tah) β, the second letter of the Greek alphabet; see also β-.
beta
beta [ba´tah]
beta (bāˑ·t
),
beta
beta /be·ta/ (ba´tah) β, the second letter of the Greek alphabet; see also β-.
be·ta (b  t , b -)n. 1. Symbol  The second letter of the Greek alphabet.2. The second item in a series or system of classification. 3. A beta particle. 4. A beta ray. adj. 1. Of or relating to the second position from a designated carbon atom in an organic molecule at which an atom or a radical may be substituted. 2. Of or relating to an isomeric variation of a chemical compound, such as a stereoisomer. |
beta
[bē′tə, bā′tə]
B, β, the second letter of the Greek alphabet, used in scientific notation to denote position of a carbon atom in a molecule, a type of protein configuration, or identification of a type of activity, as beta blocker, beta particle, or beta rhythm. It is used in statistics to define an error in the interpretation of study results.
beta [ba´tah]
second letter of the Greek alphabet, β; used to denote the second position in a classification system. Often used in names of chemical compounds to distinguish one of two or more isomers or to indicate the position of substituent atoms or groups in certain compounds. Also used to distinguish types of radioactive decay; brain rhythms or waves; adrenergic receptors; secretory cells of the various organs of the body that stain with basic dyes, such as the beta cells of the pancreas; and the type of hemolytic streptococci that produce a zone of decolorization when grown on blood media.
beta-adrenergic blocking agent (beta-blocker) any of a group of drugs that block the action of epinephrine at beta-adrenergic receptors on cells of effector organs. There are two types of these receptors: β1-receptors in the myocardium and β2-receptors in the bronchial and vascular smooth muscles. The principal effects of beta-adrenergic stimulation are increased heart rate and contractility, vasodilation of the arterioles that supply the skeletal muscles, and relaxation of bronchial muscles.
Because of their effects on the heart, these agents are used to treat angina pectoris, hypertension, and cardiac arrhythmias. And, because they decrease the workload of the heart, they are effective in reducing the long-term risk of mortality and reinfarction after recovery from the acute phase of a myocardial infarction. They are an important adjunct in treatment of heart failure and are also used for prophylaxis of migraine.
Nonselective beta-adrenergic blocking agents affect both types of receptors and can produce bronchospasm in patients with asthma or chronic obstructive pulmonary disease. If such patients need one of these drugs, they should be given a cardioselective one that preferentially blocks the β1-receptors in the heart.
Nonselective agents include propranolol (Inderal), used for treatment of angina, hypertension, arrhythmias, and migraine and for prophylaxis after the acute phase of a myocardial infarction; nadolol (Corgard), used for treatment of angina and hypertension; and timolol, used as an ophthalmic preparation (Timoptic) for treatment of glaucoma and as an oral preparation (Blocadren) for treatment of hypertension and for prophylaxis after the acute phase of a myocardial infarction. Cardioselective beta-adrenergic blocking agents are used for treatment of hypertension and include atenolol (Tenormin) and metoprolol (Lopressor).
Because of their effects on the heart, these agents are used to treat angina pectoris, hypertension, and cardiac arrhythmias. And, because they decrease the workload of the heart, they are effective in reducing the long-term risk of mortality and reinfarction after recovery from the acute phase of a myocardial infarction. They are an important adjunct in treatment of heart failure and are also used for prophylaxis of migraine.
Nonselective beta-adrenergic blocking agents affect both types of receptors and can produce bronchospasm in patients with asthma or chronic obstructive pulmonary disease. If such patients need one of these drugs, they should be given a cardioselective one that preferentially blocks the β1-receptors in the heart.
Nonselective agents include propranolol (Inderal), used for treatment of angina, hypertension, arrhythmias, and migraine and for prophylaxis after the acute phase of a myocardial infarction; nadolol (Corgard), used for treatment of angina and hypertension; and timolol, used as an ophthalmic preparation (Timoptic) for treatment of glaucoma and as an oral preparation (Blocadren) for treatment of hypertension and for prophylaxis after the acute phase of a myocardial infarction. Cardioselective beta-adrenergic blocking agents are used for treatment of hypertension and include atenolol (Tenormin) and metoprolol (Lopressor).
beta particles negatively charged particles emitted by radioactive elements, the result of disintegration of neutrons; their source is the unstable atoms of radioactive metals such as radium and uranium. There are three general types of emissions from radioactive substances: alpha and beta particles and gamma rays. Beta particles are less penetrating than gamma rays and may be used to treat certain conditions on or near the surface of the body. See also radiation and radiation therapy.
beta (bāˑ·t
),n Greek letter represented as β. See Greek letters.
Beta
a genus of the Polygonaceae family.
Beta vulgaris
this species includes the large fodder roots. They provide a massive source of feed energy but they can cause poisoning if used unintelligently, e.g. (1) carbohydrate engorgement and lactic acidosis if too many are fed; (2) partly cooked mangels grown on high nitrate soils may cause primary nitrite poisoning; (3) the tops may contain toxic amounts of oxalate; (4) a sole diet of beet pulp is thought to cause a nutritional deficiency of vitamin A in cattle leading to blindness and encephalopathy. Called also fodder beet, sugar beet, mangels, mangolds, mangel-wurzel, beetroot.
beta
the second letter of the Greek alphabet, B or β; used to denote the second position in a chemical classification system. Often used in names of chemical compounds to distinguish one of two or more isomers or to indicate the position of substituent atoms or groups in certain compounds. Also used to distinguish types of radioactive decay; brain rhythms or waves; adrenergic receptors; secretory cells of the various organs of the body that stain with basic dyes, such as the beta cells of the pancreas; and the type of hemolysis induced by bacteria that results in a zone of complete hemolysis when grown on blood agar, except for staphylococci.
beta adrenergic
see adrenergic.
beta-adrenergic receptors,
β-adrenergic receptors specific sites on effector cells that respond to epinephrine. There are two types: β1-receptors, found in the heart and small intestine, and β2-receptors, found in the bronchi, blood vessels and uterus.
beta agonists
see adrenergic.
beta barrels
a form of secondary structure of a polypeptide in which β strands of amino acids are wound into a super secondary structure; usually interconnected by α helical regions of the polypeptide on the outside of the molecule.
beta-blocker
a drug that blocks the action of epinephrine at beta-adrenergic receptors on cells of effector organs. There are two types of these receptors: β1-receptors in the myocardium and β2-receptors in the bronchial and vascular smooth muscles. The principal effects of beta-adrenergic stimulation are increased heart rate and contractility, vasodilation of the arterioles that supply the skeletal muscles, and relaxation of bronchial muscles.
beta brain waves
those having a frequency of more than 10 hertz (pulsations per second); seen during wakefulness. See also electroencephalography.
beta-carboline indoleamine alkaloid
poisoning causes a nervous syndrome of hyper- or hypomotility, muscle tremor, flexed paresis of fore- or hindlimbs, hypermetria, walking backwards, convulsions. A plant poison found in Peganum, Tribulus, Kallstroemia spp.
beta carbon
carbon-3 of a molecule or the carbon atom two on from the function group of a molecule, the carbon(s) of which are not included in the lettering.
beta-endorphin
hormone secreted by central nervous system, hypothalamus, gastrointestinal tract. See also endorphin.
beta fibrillosis
see amyloidosis.
beta-folded domains
compact, locally folded region of tertiary structure containing the β-sheets or β-turns.
beta hemolysin
is a sphingomyelinase and is produced by staphylococci. It produces partial hemolysis of sheep and cattle erythrocytes. It appears to have little pathogenic effect. See also beta hemolysis.
beta-hydroxy-beta-methylglutaryl coenzyme A
1. intermediate in the formation of ketones.
2. key starting compound in the synthesis of cholesterol.
beta-hydroxybutyrate
salt of the major circulating ketone body in animals, formed from the reduction of acetoacetic acid.
beta-hydroxybutyrate dehydrogenase
mitochondrial enzyme catalyzing the NADH-linked-reduction of acetoacetate to β-hydroxybutyrate.
beta-ketobutyric acid
beta particle
an electron emitted from a nucleus.
beta radiation
see radiation injury, radiotherapy.
beta sheet (β-sheet)
a common structural feature of many proteins in which the single polypeptide chain is folded back and forth upon itself with each folded section running in an opposite direction to its nearest neighbors. The folded sections are held together by hydrogen bonds and the arrangement which occurs, particularly in the core of proteins, confers great stability on the molecule.
beta subunit
second-named chain (or subunit) occurring in the functional organization of macromolecules, usually proteins, containing two or more chains.
beta
β The second letter of the Greek alphabet; Statistics The probability of a Type II–false-negative error. See Type II error. Cf Alpha.
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