| high density lipoprotein | <biochemistry> These lipoproteins acts to carry cholesterol in the bloodstream. Raised high density lipoprotein levels have been correlated with a lower risk for heart disease. Less than 35 mg/dl is considered a positive risk factor for coronary artery disease, over 60 mg/dl is considered a negative risk factor (reduces your risk of heart disease). Recent studies show a low high density lipoprotein level is the strongest predictor of cardiovascular death in women. Acronym: HDL (18 Nov 1997) |
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| high dose tolerance | The induction of tolerance by exposure to high doses of antigen. (05 Mar 2000) |
| high-egg-passage vaccine | Living Flury strain rabies virus at the 180th to 190th level egg passage (embryonate eggs), used for vaccination of cattle and cats, low-egg-passage (LEP) vaccine: at the 40th to 50th passage level, containing 103 to 104 mouse LD50; nonpathogenic in dogs but retains some pathogenicity for cattle and cats. (05 Mar 2000) |
| high endothelial postcapillary venules | Venule's in the lymph nodes, tonsils, and Peyer's patches that have a high-walled endothelium through which blood lymphocytes migrate into the lymphatic parenchyma. (05 Mar 2000) |
| high enema | An enema instilled high up into the colon. Synonym: enteroclysis. (05 Mar 2000) |
| high energy bond | <chemistry> Chemical bonds that release more than 25kJ/mol on hydrolysis: their importance is that the energy can be used to transfer the hydrolysed residue to another compound. The risk in using the term is that students may think the bond itself is different in some way, whereas it is the compound that matters. Hydrolysis of creatine phosphate yields 42.7kJ/mol, of phosphoenolpyruvate, 53.2, ATP to ADP, 30.5: the latter is important because it shows that energetically the hydrolysis of creatine phosphate will suffice to reconstitute ATP, hence the use of creatine phosphate in muscle. (18 Nov 1997) |
| high energy compounds | Classically, a group of phosphoric esters whose hydrolysis takes place with a standard free energy change of -5 to -15 kcal/mol (or, -20 to -63 kJ/mol) (in contrast to -1 to -4 kcal/mol or, -4 to -17 kJ/mol) for simple phosphoric esters like glucose-6-phosphate or alpha-glycerophosphates), thus being capable of driving energy-consuming reactions in living cells or reconstituted cell-free systems; adenosine 5'-triphosphate, with respect to the beta-and gamma-phosphates, is the best known and is regarded as the immediate energy source for most metabolic syntheses. The general types are acid anhydrides, phosphoric esters of enols, phosphamic acid (R-NH-PO3H2) derivatives, acyl thioesters (e.g., of coenzyme A), sulfonium compound's (R3-S+), and aminoacyl esters of ribosyl moieties. See: high energy phosphates. (05 Mar 2000) |
| high energy particle generating unit | A machine capable of providing highly energised radiation for the purposes of radiotherapy treatment. (16 Dec 1997) |
| high energy phosphate bond | See: high energy phosphates. (05 Mar 2000) |
| high energy phosphates | Those phosphate's that, on hydrolysis, yield an unusually large amount of energy; e.g., nucleotide polyphosphates such as ATP, enol phosphate's such as phosphoenolpyruvate. See: high energy compounds. Synonym: energy-rich phosphates. (05 Mar 2000) |
| high-energy shock waves | Compression waves of large amplitude, across which density, pressure, and particle velocity change drastically. (12 Dec 1998) |
| high extinction microscopy | <technique> Polarized-light, interference, fluorescence, and other modes of microscopy using polarization rectifiers and other devices to achieve a high degree of back- ground extinction in order to bring out the signal originating from a very small degree of birefringence, optical path difference, fluorescence etc. (05 Aug 1998) |
| high-fat diet | A diet containing large amounts of fat. (05 Mar 2000) |
| high-fibre diet | A diet high in the nondigestible part of plants, which is fibre. Fibre is found in fruits, vegetables, whole grains, and legumes. Insoluble fibre increases stool bulk, decreases transit time of food in the bowel, and decreases constipation and the risk of colon cancer. Soluble fibre delays absorption of glucose, which helps to control blood sugar in diabetes mellitus, and delays absorption of lipids, which helps to control hyperlipidemia. Recommended in treatment of diverticular disease of the colon. (05 Mar 2000) |
| high forceps delivery | Delivery by forceps applied to the foetal head before engagement has taken place. (05 Mar 2000) |