| folacin | An obsolete and now unapproved term for folic acid or any derivative thereof that has the biological (vitamin) activity of folic acid. (05 Mar 2000) |
|---|---|
| folate | <biochemistry> Molecule that acts as a carrier of one carbon units in intermediary metabolism. It contains residues of p aminobenzoate, glutamate and a substituted pteridine. The latter cannot be synthesised by mammals, which must obtain tetrahydrofolate as a vitamin or from intestinal microorganisms. One carbon units are carried at three different levels of oxidation, as methyl, methylene or formimino groups. Important biosyntheses dependent on tetrahydrofolate include those of methionine, thymine and purines. Analogues of dihydrofolate, such as aminopterin and methotrexate block the action of tetrahydrofolate by inhibiting its regeneration from dihydrofolate. (18 Nov 1997) |
| 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) |
| fold | 1. A ridge or margin apparently formed by the doubling back of a lamina. See: plica. 2. In the embryo, a transient elevation or reduplication of tissue in the form of a lamina. (05 Mar 2000) |
| fold of chorda tympani | The fold of mucosa that surrounds the chorda tympani nerve in its course through the tympanic cavity. Synonym: plica chordae tympani. (05 Mar 2000) |
| fold of laryngeal nerve | <anatomy, nerve> The slight fold of mucosa in the piriform recess of the pharynx that encloses the superior laryngeal nerve. Synonym: plica nervi laryngei, fold of laryngeal nerve. (05 Mar 2000) |
| fold of left vena cava | A pericardial fold lying between the left oblique vein of the atrium and the left superior pulmonary vein containing the obliterated remains of the left superior vena cava. Synonym: plica venae cavae sinistrae, Marshall's vestigial fold, vestigial fold. (05 Mar 2000) |
| fold of superior laryngeal nerve | <anatomy, nerve> The slight fold of mucosa in the piriform recess of the pharynx that encloses the superior laryngeal nerve. Synonym: plica nervi laryngei, fold of laryngeal nerve. (05 Mar 2000) |
| fold-back elements | A type of transposable element that possesses long inverted repeats, such that when denatured, loops are formed. (05 Mar 2000) |
| foldback DNA | <molecular biology> Sections of single-stranded DNA which have sequences that are palindromes, or which read the same both backwards and forwards, that may base pair with each other instead of with the right sections of the other strand during renaturation into double-stranded DNA. (09 Oct 1997) |
| folded-lung syndrome | <syndrome> Collapse of part of the lung caught between shrinking fibrous pleura scars, sometimes resulting from pleural asbestosis. Synonym: round atelectasis. (05 Mar 2000) |
| folding | 1. The act of making a fold or folds; also, a fold; a doubling; a plication. "The lower foldings of the vest." (Addison) 2. <agriculture> The keepig of sheep in inclosures on arable land, etc. Folding boat, a portable boat made by stretching canvas, etc, over jointed framework, used in campaigning, and by tourists, etc. Folding chair, a chair which may be shut up compactly for carriage or stowage; a camp chair. Folding door, one of two or more doors filling a single and hung upon hinges. Source: Websters Dictionary (01 Mar 1998) |
| folding fracture | A deformity in children consisting of a local bulging caused by the longitudinal compression of the soft bone; it occurs commonly in the radius or ulna or both. Synonym: folding fracture. (05 Mar 2000) |
| folds of iris | Numerous very fine, almost microscopic, radial folds on the posterior surface of the iris that extend around the pupillary margin. Synonym: plicae iridis. (05 Mar 2000) |
| Foley catheter | <equipment> Flexible plastic tube inserted into the bladder to provide continuous urinary drainage. (12 Nov 1997) |