Test composition and method for assaying dehydrogenase enzymes in test fluids which comprises contacting the fluid with a test reagent comprising a coenzyme, a substrate for the dehydrogenase enzyme, a terminal acceptor dye and Meldola's Blue as an intermediary hydrogen carrier. A preferable embodiment of the present invention comprises incorporating the test composition with a solid carrier therefor and using the same as a dip and read test device.
A method of determining lactate dehydrogenase activity in biological fluids comprising reacting a biological fluid sample with a coupled enzyme series in an oxygenated aqueous solution containing lactate, nicotinamide adenine dinucleotide and an electron transfer agent, and measuring the uptake of oxygen by the oxidation of the resulting NADH with an oxygen-sensing electrode.
A stable, colored reference standard suitable for use in diagnostic determinations involving enzymatic reactions in which colorless 2-(p-iodophenyl)-3-(p-nitrophenyl)-5-phenyltetrazolium chloride is reduced to the red-colored 1-(p-iodophenyl)-5-(p-nitrophenyl)-3-phenylformazan, is described. The reference standard of this invention is an aqueous solution containing, in specified amounts, 1-(p-iodophenyl)-5-(p-nitrophenyl)-3-phenylformazan; serum albumin; an N,N'-dimethylformamide or a dimethylsulfoxide solvent; and isopropyl alcohol. An inert bulking agent may be added to the aqueous colored standard and the solution obtained may then be lyophilized. The lyophilized form of the colored reference standard is stable for at least 3 months at 4.degree. C. and 24.degree. C. and can be easily reconstituted with water or with dilute aqueous hydrochloric acid solutions. The novel colored reference standard solution has an absorbence maximum of 500 nanometers. The colored reference standard of this invention may be used in the determination of serum lactate dehydrogenase, creatine phosphokinase, glucose-6-phosphate dehydrogenase, adenosine phosphate, glucose, glucose-6-phosphate, 6-phosphogluconate and the like.
A tetrazolium-based system for testing for the presence of organisms or cells in a specimen includes in one embodiment a mixture of a substrate and an indicator system, wherein the overall system is buffered to a pH above 8.0, and in a preferred embodiment at about a pH of 9.0 when mixed. The substrate solution and indicator solution are not mixed until shortly before use. The indicator solution is buffered at a pH of approximately 3.3, thereby enhancing the shelf life. The substrate may consist of glucose with at least one amino acid in a buffered solution formulated such that, by mixing equal parts with the indicator solution, a pH above 8, preferably 9.0 results.
Stabilized aqueous solution of a coenzyme for hydrogen-transferring enzymes characterized in that the solution contains NAD, NADP or a derivative thereof in an oxidized or reduced form and one or several organic compounds or salts thereof having a pKa value between 1.5 and 6.0 and/or a nitrogen compound of the general formula ##STR00001## in which the residues R.sub.1, R.sub.2 and R.sub.3 are the same or different and denote hydrogen, or a saturated or unsaturated alkyl or aryl group as well as the use of the solution to determine dehydrogenases in particular lactate dehydrogenase or substrates thereof.
An indicator for placement in an ethylene oxide sterilizer changes color if the sterilization has been effective. The indicator includes an amino substituted indicating compound which undergoes color change based on replacement of labile hydrogen in amino groups with hydroxyethyl, and a buffering agent selected to provide an ionic dissociation equilibrium such that color change occurs only when sterilization has been effective.
