| folate antagonist | <pharmacology> One of a group of substances which blocks the formation of nucleotides that require the presence of folate (one of the B vitamins) before they can be made. The substance does this by blocking key steps in the reaction sequence. These substances are often used to treat cancer because fast-growing cancerous cells usually need to use the blocked reactions more than normal cells. (09 Oct 1997) |
|---|---|
| folic acid antagonist | <pharmacology> A chemical which inhibits a cells capacity to use folic acid and so prevent cell division, for example methotrexate. See: chemotherapy. (12 Nov 1997) |
| gene rearrangement, b-lymphocyte, heavy chain | Ordered rearrangement of b-lymphocyte variable gene regions thereby contributing to antibody diversity. It occurs during the first stage of differentiation of the immature b-lymphocyte. (12 Dec 1998) |
| metals, heavy | metals with high specific gravity, typically larger than 5. They have complex spectra, form coloured salts and double salts, have a low electrode potential, are mainly amphoteric, yield weak bases and weak acids, and are oxidizing or reducing agents (12 Dec 1998) |
| MyoD heavy chain kinase | <enzyme> Required for actin activation of the magnesium atpase activity of dictyostelium myosin id (myod); specific for myod Registry number: EC 2.7.1.- Synonym: 110-kD protein kinase, dictyostelium, dictyostelium 110-kD protein (26 Jun 1999) |
| myosin heavy chain | <protein> See myosin: do not confuse with heavy meromyosin which is a subfragment of the heavy chain of myosin II. (18 Nov 1997) |
| myosin heavy chains | The heavy chains of the muscle protein myosin. Each molecule of myosin is composed of two heavy chains and two pairs of light chains. The heavy chains have a molecular weight of about 230 kD and each heavy chain is associated with a dissimilar pair of light chains. (devlin, textbook of biochemistry: with clinical correlations, 3rd ed, p957) (12 Dec 1998) |
| heavy | 1. Heaved or lifted with labour; not light; weighty; ponderous; as, a heavy stone; hence, sometimes, large in extent, quantity, or effects; as, a heavy fall of rain or snow; a heavy failure; heavy business transactions, etc.; often implying strength; as, a heavy barrier; also, difficult to move; as, a heavy draught. 2. Not easy to bear; burdensome; oppressive; hard to endure or accomplish; hence, grievous, afflictive; as, heavy yokes, expenses, undertakings, trials, news, etc. "The hand of the Lord was heavy upon them of Ashdod." (1 Sam. V. 6) "The king himself hath a heavy reckoning to make." (Shak) "Sent hither to impart the heavy news." (Wordsworth) "Trust him not in matter of heavy consequence." (Shak) 3. Laden with that which is weighty; encumbered; burdened; bowed down, either with an actual burden, or with care, grief, pain, disappointment. "The heavy [sorrowing] nobles all in council were." (Chapman) "A light wife doth make a heavy husband." (Shak) 4. Slow; sluggish; inactive; or lifeless, dull, inanimate, stupid; as, a heavy gait, looks, manners, style, and the like; a heavy writer or book. "Whilst the heavy plowman snores." (Shak) "Of a heavy, dull, degenerate mind." (Dryden) "Neither [is] his ear heavy, that it can not hear." (Is. Lix. 1) 5. Strong; violent; forcible; as, a heavy sea, storm, cannonade, and the like. 6. Loud; deep; said of sound; as, heavy thunder. "But, hark! that heavy sound breaks in once more." (Byron) 7. Dark with clouds, or ready to rain; gloomy; said of the sky. 8. Impeding motion; cloggy; clayey; said of earth; as, a heavy road, soil, and the like. 9. Not raised or made light; as, heavy bread. 10. Not agreeable to, or suitable for, the stomach; not easily digested; said of food. 11. Having much body or strength; said of wines, or other liquors. 12. With child; pregnant. Heavy artillery. <chemistry> See Metal. Heavy weight, in wrestling, boxing, etc, a term applied to the heaviest of the classes into which contestants are divided. Cf. Feather weight, under Feather. Heavy is used in composition to form many words which need no special explanation; as, heavy-built, heavy-browed, heavy-gaited, etc. Origin: OE. Hevi, AS. Hefig, fr. Hebban to lift, heave; akin to OHG. Hebig, hevig, Icel. Hofigr, hofugr. See Heave. Source: Websters Dictionary (01 Mar 1998) |
| heavy chain | <protein> In general, the larger polypeptide in a multimeric protein. Thus the immunoglobulin heavy chain is of 50 kD, the light chain of 22 kD, whereas in myosin the heavy chain is very much larger (220 kD) than the light chains (~20 kD). (18 Nov 1997) |
| heavy chain disease | A disorder of immunoglobulin synthesis in which large quantities of abnormal heavy chains are excreted in the urine. The amino acid sequences of the n- (amino-) terminal regions of these chains are normal, but they have a deletion extending from part of the variable domain through the first domain of the constant region, so that they cannot form cross-links to the light chains. The defect arises through faulty coupling of the variable (v) and constant (c) region genes. (12 Dec 1998) |
| heavy hydrogen | <radiobiology> Somewhat informal alternative name for deuterium. See: deuterium. (10 Jan 1998) |
| Heavy Ion Beams | <radiobiology> Particle beams using heavy (as opposed to light) ions. These can be used for inertial confinement fusion research. (10 Jan 1998) |
| heavy liquid petrolatum | <chemical> A mixture of liquid hydrocarbons obtained from petroleum. It is used as laxative, lubricant, ointment base, and emollient. Pharmacological action: cathartic, emollients, ointment bases. Chemical name: Hydrocarbon oils (12 Dec 1998) |
| heavy nitrogen | The less common stable nitrogen isotope, making up 0.37% of natural nitrogen. Synonym: heavy nitrogen. (05 Mar 2000) |
| heavy oxygen | A stable oxygen isotope making up 0.20% of natural oxygen; used in mass spectrometry and in NMR studies of tissue. Synonym: heavy oxygen. (05 Mar 2000) |