| oral lactose tolerance test | A test for lactose deficiency; the plasma glucose response to an oral lactose load is measured as in the (oral) glucose tolerance test. (05 Mar 2000) |
|---|---|
| lactose | The major sugar in human and bovine milk. Conversion of lactose to lactic acid by Lactobacilli etc. Is important in the production of yoghurt and cheese. (18 Nov 1997) |
| lactose carrier protein | <protein> The best known example is the product of the lacY gene, coded for in the lactose operon and responsible for the uptake of lactose by E. Coli. (18 Nov 1997) |
| lactose factors | Plasmids which determine the ability of a bacterium to ferment lactose. (12 Dec 1998) |
| lactose intolerance | A disorder characterised by abdominal cramps and diarrhoea after the consumption of food containing lactose (for example milk, ice cream), believed to occur due to a deficiency of intestinal lactase (enzyme that breaks down lactose), may appear first in young adults who have previously tolerated milk well as infants. (27 Sep 1997) |
| lactose-litmus agar | Agar made by adding 2% lactose and litmus to acid-free nutrient agar; formerly used in the identification of Salmonella typhi. (05 Mar 2000) |
| lactose operon | Group of adjacent and coordinately controlled genes concerned with the metabolism of lactose in E. Coli. The lac operon was the first example of a group of genes under the control of an operator region to which a lactose repressor binds. When the bacteria are transferred to lactose containing medium, allolactose (which forms by transglycosylation when lactose is present in the cell) binds to the repressor, inhibits the binding of the repressor to the operator and allows transcription of mRNA for enzymes involved in galactose metabolism and transport across the membrane (_ galactosidase, galactoside permease and thiogalactoside transacetylase). (18 Nov 1997) |
| lactose permease | <chemical> Chemical name: permease, lactose Synonym: lactose carrier protein, lactose permease m protein, lac permease, lactose transport protein, lactose transport system, lac carrier protein, lacs protein, lactose transport system, streptococcus thermophilus, lacy protein (26 Jun 1999) |
| lactose repressor | Protein (tetramer of 37 kD subunits) that normally binds with very high affinity to the operator region of the lactose operon and inhibits transcription of the downstream genes by blocking access of the polymerase to the promoter region. When the lactose repressor binds allolactose, its binding to the operator is reduced and the gene set is derepressed. (18 Nov 1997) |
| lactose synthase | <enzyme> An enzyme of the transferase class that catalyses the transfer of galactose from udpgalactose to glucose, forming lactose. The enzyme is a complex of the enzyme n-acetyllactosamine synthase and alpha-lactalbumin; the latter protein is present in lactating mammary gland cells where it alters the usual specificity of the former to make lactose synthesis the preferred reaction. Chemical name: UDPgalactose:D-glucose 4-beta-D-galactosyltransferase Registry number: EC 2.4.1.22 (12 Dec 1998) |
| bacteria-free stage of bacterial endocarditis | Endocarditis described prior to the antibiotic era and presumably due to spontaneous healing of the bacterial vegetations. (05 Mar 2000) |
| carbon dioxide-free water | Purified water that has been boiled vigorously for 5 minutes or more. (05 Mar 2000) |
| radical, free | In biochemistry, it is a group of atoms bonded together into an entity that is extremely reactive and shortlived. (a free radical is not a political extremist on parole.) (12 Dec 1998) |
| germ-free animal | An animal which has no microorganisms whatsoever living in or on it. An animal which was born and raised in an isolated environment with no microorganisms in it, such as within a germ-free isolator. (09 Oct 1997) |
| germ-free isolator | A chamber which has absolutely no microorganisms whatsoever living in it, where a germ-free animal can be born and raised. An artificial barrier surrounding a living facility for germ-free animals, which keeps out all microorganisms. (09 Oct 1997) |