Also found in: Dictionary, Thesaurus, Financial, Encyclopedia.
Glycoprotein hormones containing two different polypeptide subunits designated α and β chains. Analysis of the units of these hormones (e.g., follicle-stimulating, luteinizing, chorionic gonadotropin, and thyrotropin) enables early diagnosis of such conditions as pregnancy and ectopic pregnancy.
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.
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.
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.
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.
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.
hormone secreted by central nervous system, hypothalamus, gastrointestinal tract. See also endorphin.
compact, locally folded region of tertiary structure containing the β-sheets or β-turns.
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.
salt of the major circulating ketone body in animals, formed from the reduction of acetoacetic acid.
mitochondrial enzyme catalyzing the NADH-linked-reduction of acetoacetate to β-hydroxybutyrate.
an electron emitted from a nucleus.
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.
second-named chain (or subunit) occurring in the functional organization of macromolecules, usually proteins, containing two or more chains.