| formaldehyde fixative | A widely used fixing agent for pathologic histology; the commercial solution is 37-40% formaldehyde and is known as 100% formalin or formol; a common impurity is formic acid, which must be neutralised or the fixative made in buffer solution; tissues fixed may have a pigment artifact precipitated. (05 Mar 2000) |
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| active formaldehyde | A hydroxymethyl derivative of tetrahydrofolate or thiamin pyrophosphate, N5,N10-methylenetetrahydrofo late. (05 Mar 2000) |
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| melamine formaldehyde | A plastic material mixed with plaster of Paris for casts. Such a cast is lighter and stronger than one made with plaster of Paris alone. Synonym: melamine formaldehyde. (05 Mar 2000) |
| mycothiol-dependent formaldehyde dehydrogenase | <enzyme> Registry number: EC 1.2.1.- Synonym: mdf dehydrogenase (26 Jun 1999) |
| formaldehyde | <chemical> Commonly used fixative and antibacterial agent. As a fixative it is cheap and tends to cause less denaturation of proteins than does glutaraldehyde, particularly if used in a well buffered solution (buffered formalin, formal saline). Old formaldehyde solutions usually contain cross linking contaminants and it is therefore often preferable to used a formaldehyde generating agent such as paraformaldehyde. Formalin fumes, particularly in conjunction with hydrochloric acid vapour, are potently carcinogenic. (20 Jun 2000) |
| formaldehyde dismutase | <enzyme> Contains noncovalently bound nad(h); forms equimolar amounts of corresponding alcohols and acids from various aldehydes Registry number: EC 1.1.1.- (26 Jun 1999) |
| formaldehyde ferredoxin oxidoreductase | <enzyme> Contains molybdopterin as the organic component of tungsten cofactor Registry number: EC 1.2.7.- Synonym: hcho ferredoxin oxidoreductase (26 Jun 1999) |
| formaldehyde reductase | <enzyme> Catalyses reduction of formaldehyde to methanol using NADH Registry number: EC 1.1.1.- (26 Jun 1999) |
| formaldehyde transketolase | <enzyme> From yeast; formaldehyde plus xylulose-5-phosphate yields glyceraldehydephosphate and dihydroxyacetone Registry number: EC 2.2.1.3 Synonym: dihydroxyacetone synthase (26 Jun 1999) |
| acetone fixative | Acetone used at low temperatures to fix enzymes, particularly phosphatases; it removes fat and glycogen. (05 Mar 2000) |
| Altmann's fixative | A bichromate-osmic acid fixative. (05 Mar 2000) |
| Bouin's fixative | A solution of glacial acetic acid, formalin, and picric acid, useful for soft and delicate tissues (as those of embryos) and small pieces of tissues; it preserves glycogen and nuclei and permits brilliant staining, but penetrates slowly, distorts kidney tissue and mitochondria, and does not permit Feulgen stain for DNA. (05 Mar 2000) |
| Carnoy's fixative | Ethanol, chloroform, and acetic acid (6:3:1) or ethanol and acetic acid (3:1), an extremely rapid fixative used for glycogen preservation and as a nuclear fixative. (05 Mar 2000) |
| Marchi's fixative | A mixture of Muller's fixative with osmium tetroxide, with potassium chlorate substituted for the potassium dichromate of Muller's fixative for better results; used to demonstrate degenerating myelin. See: Marchi's stain. (05 Mar 2000) |
| Park-Williams fixative | A fixative for spirochetes, comprised of a 2% solution of osmic acid to the fumes of which the bacteria are exposed for a few seconds. (05 Mar 2000) |
| Regaud's fixative | A fixative containing formaldehyde and sodium dichromate, used to preserve mitochondria but not fat; requires afterchroming and extensive washing. (05 Mar 2000) |