| RAS | rapid atrial stimulation; recurrent aphthous stomatitis; reflex activating stimulus; reliability, av... |
|---|---|
| ras | retrovirus-associated DNA sequence |
| ANF | Atrial Natriuretic Factors |
| ECF | 1) Eosinophilic Chemotatic Factors 2) Extra-Cellular Fluid; 세포 외액 |
| NCF | Neutrophilic Chemotatic Factors |
| mRNA (guanine(N7))-methyltransferase | <enzyme> Catalyses s-adenosyl-l-methionine and g(5')pppr-RNA to yield s-adenosyl-l-homocysteine and m(7)g(5')pppr-RNA; mRNA containing an n(7)-methylguanine cap Registry number: EC 2.1.1.56 Synonym: mRNA (guanine-7-)methyltransferase, mRNA(guanine-7-)methyltransferase, RNA (guanine-7) methyltransferase, abd1 gene product (26 Jun 1999) |
|---|---|
| pyrimidine-guanine sequence-specific ribonuclease | <enzyme> From yolk granules of adult rana catesbeiana oocytes Registry number: EC 3.1.27.- Synonym: rc-rnase, rana catesbeiana rnase (26 Jun 1999) |
| hypoxanthine-guanine phosphoribosyl tranferase marker | The gene which codes for the enzyme hypoxanthine-guanine phosphoribosyl transferase. It is a selectable marker because cells which have a defective version of this gene are resistant to poisoning by toxic purine derivatives which result from the metabolic pathway that the HGPRT enzyme catalyses. (The purine derivatives are toxic because they incorporate into DNA as a result of the HGPRT enzyme's actions). Because the defective gene cannot produce the enzyme, no toxic purine derivatives are produced, the gene can therefore be selected for. (09 Oct 1997) |
| hypoxanthine guanine phosphoribosyltransferase | <enzyme> An enzyme that catalyses the conversion of 5-phosphoribosyl-1-pyrophosphate and hypoxanthine, guanine, or 6-mercaptopurine to the corresponding 5'-mononucleotides and pyrophosphate. The enzyme is important in purine biosynthesis as well as central nervous system functions. Complete lack of enzyme activity is associated with the lesch-nyhan syndrome, while partial deficiency results in overproduction of uric acid. Chemical name: IMP:pyrophosphate phospho-D-ribosyltransferase Registry number: EC 2.4.2.8 (12 Dec 1998) |
| hypoxanthine-guanine phosphoribosyl transferase | <enzyme> An enzyme which plays an important role in the making of ATP and GTP from guanine -- the only way guanine, adenine, or other purine molecules are able to become part of nucleic acids. Biologists study gene action via the incorporation of modified nitrogenous bases into DNA by manipulating the metabolic role which this enzyme plays. Similarly, the enzyme thymidine kinase is used for the same purpose by biologists because it fills the same important and unique role for the pyrimidines (thymine, cytosine, uracil, etc.). Acronym: HGPRT (09 Oct 1997) |
| hypoxanthine guanine phosphoribosyltransferase deficiency | A sex-linked inherited metabolic disorder; complete deficiency results in Lesch-Nyhan syndrome; incomplete deficiency is associated with acute gouty arthritis and renal stones. (05 Mar 2000) |
| hypoxanthine-guanine-xanthine phosphoribosyltransferase | <enzyme> From tritrichomonas foetus; in contrast to EC 2.4.2.8, this enzyme also uses xanthine as substrate; mw 24 kD Registry number: EC 2.4.2.- Synonym: hgxprtase (26 Jun 1999) |
| anion exchange | The process by which an anion in a mobile (liquid) phase exchanges with another anion previously bound to a solid, positively charged phase, the latter being an anion exchanger. It takes place when Cl- is exchanged for OH- in desalting. The reaction is Cl- (in solution) + (OH- on anion exchanger+) → (Cl- on anion exchanger) + OH- (in solution); combined with cation exchange, NaCl is removed from solution. Anion exchange may also be used chromatographically, to separate anions, and medicinally, to remove an anion (e.g., Cl-) from gastric contents or bile acids in the intestine. (05 Mar 2000) |
| anion exchange resin | <chemistry> A resin with fixed cationic groups which is used in chromatography to separate anionic molecules. A High molecular weight, insoluble polymers that contain functional anionic groups capable of undergoing exchange reactions. These resins are used for ion exchange chromatography, as gastric antacids, hypocholesteraemics, etc. (14 Aug 2000) |
| maternal-foetal exchange | Exchange of substances between the maternal blood and the foetal blood through the placental barrier. It excludes microbial or viral transmission. (12 Dec 1998) |
| cation exchange | The process by which a cation in a liquid phase exchanges with another cation present as the counter-ion of a negatively charged solid polymer (cation exchanger). A cation-exchange reaction in removal of the Na+ of a sodium chloride solution is RSO3-H+ + Na+ → RSO3-Na+ + H+ (R is the polymer, RSO3- is the cation exchanger); if this is combined with the anion-exchange reaction, NaCl is removed from the solution (desalting). Cation exchange may also be used chromatographically, to separate cations, and medicinally, to remove a cation; e.g., H+, from gastric contents, or Na+ and K+ in the intestine. See: anion exchange. (05 Mar 2000) |
| cation-exchange resin | See: cation exchange, cation exchanger. (05 Mar 2000) |
| cation exchange resins | High molecular weight insoluble polymers which contain functional cationic groups that are capable of undergoing exchange reactions; used in various types of chromatography; also to treat hyperkalaemia. (12 Dec 1998) |
| respiratory exchange ratio | The ratio of the net output of carbon dioxide to the simultaneous net uptake of oxygen at a given site, both expressed as moles or STPD volumes per unit time; in the steady state, respiratory exchange ratio is equal to the respiratory quotient of metabolic processes. (05 Mar 2000) |
| charge exchange | <radiobiology> Phenomenon in which an ion colliding with a molecule (or an atom) neutralises itself by capturing an electron from the molecule or atom, and transforming the molecule or atom into a positive radical or ion. (13 Nov 1997) |