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At least 1,207 records · Page 67Linked to original sources
PubMed1978

Enzymic serum cholesterol measurement with a basic autoanalyzer and Du Pont aca method.

I compared enzymic methods for total serum cholesterol as used with discrete (Du Pont aca and reagent packs) and continuous-flow (Boehringer Mannheim reagents and the Technicon AuotAnalyzer I) analysis of normal, icteric, and lipemic sera. The regression equation for 24 clear, non-icteric sera was: y (continuous flow) = 0.944x (aca) + 10.69; r = 0.971, Syx +/- 53.7 mg of cholesterol per liter. The continuous-flow system indicated no significant interference when as much as 350 mg of bilirubin was added per liter. Results with the aca method indicated a decrease in apparent cholesterol of about 5 mg/liter per milligram of added bilirubin. Serial diluting of lipemic sera resulted in falsely higher values with the aca method but no clinically significant effect on results with the AutoAnalyzer procedure. Apparent cholesterol as measured with the aca became proportionately greater than AutoAnalyzer values with increasing serum triglyceride concentration.

Autoanalysis↗
PubMed1978

New enzymatic method for serum uric acid at 500 nm.

We describe a manual method, well suited to mechanization, for quantitating serum uric acid at 500 nm. In the assay mixture (0.10 ml of sample and 3.00 ml of reagent) the hydrogen peroxide produced from uric acid by uricase is coupled with p-hydroxybenzoate and 4-aminoantipyrine in the presence of peroxidase to form a colored complex, which is measured. A separate sample blank is obviated by taking an initial absorbance measurement 20 s after the sample is added. The reaction is complete within 5 min; its sensitivity is 0.001 deltaA/mg per liter. Absorbances are linearly related to uric acid concentrations up to 120 mg/liter. Many substances that may be present in normal serum do not interfere, but bilirubin in moderately above-normal concentrations will interfere. The procedure can be modified to largely correct for this, when necessary. The proposed method (y) correlated well (r = 0.979) with the uric acid 293 nm reference method (x) and the relation is described by the equation y = 0.998x + 2.42.

Humans↗
PubMed1980

Use of 3,5-dichloro-2-hydroxybenzenesulfonic acid/4-aminophenazone chromogenic system in direct enzymic assay of uric acid in serum and urine.

A new direct colorimetric procedure for uric acid assay in serum or urine is described, utilizing a 3,5-dichloro-2-hydroxybenzene sulfonic acid/4-aminophenazone chromogenic system in the presence of horseradish peroxidase and uricase from Aspergillus flavus. This chromogen system has a high absorptivity, affording useful results with sample/reagent volume ratios as low as 0.025. The procedure is applicable to serum, plasma, or diluted urine. A single working reagent is used; the reaction is complete in less than 15 min at room temperature. The red dye formed is measured at 520 nm; a blank sample measurement is not needed. The standard curve for the method is linear for uric acid concentrations up to 1500 mumol/L. Average analytical recovery of uric acid in human sera and urine exceeded 99%; within-run and between-run precision studies showed CV's of less than or equal to 1.2 and less than or equal to 2.2%, respectively. The new procedure correlated well with the uricase/catalase and uricase/ultraviolet methods. The method is suitable for automation.

Aminopyrine↗
PubMed1994

[Perioperative alterations in polymorphonuclear leukocyte function mediated by protein kinase C].

To characterize the perioperative alterations in polymorphonuclear leukocytes (PMN) function mediated by protein kinase C, we studied twenty six patients undergoing gastrointestinal surgery. Seventeen patients with thoracic esophageal cancer were underwent total thoracic esophagectomy through a right thoracotomy (severe surgical stress group). Nine patients underwent cholecystectomy (slight surgical stress group). Measurement of O2- production capacity was used as a reflection of the activity of NADPH oxidase, and the activity of myeloperoxidase-H2O2-halide system was evaluated using luminol-dependent chemiluminescence. O2- production stimulated by phorbol 12-myristate 13-acetate (PMA) was suppressed, reaching a minimum on POD 3. On the other hand, luminol dependent chemiluminescence increased significantly after surgery, reached a maximum on POD 3. These alterations were more remarkable in the severely stressed patients. These results suggest that postoperative PMN signal transduction mechanisms, mediated by protein kinase C, may activate myeloperoxidase-H2-O2-halide system but suppress NADPH oxidase system dependently of the degree of surgical stress, revealing a differential effect of protein kinase C activation on PMN microbicidal activity.

Aged↗
PubMed1976

III. Histochemical characteristics of suspensor during embryo development in Brassica campestris Linn. var., Sarson.

The development of suspensor in Brassica campestris is of the "Onagrad type"; The suspensor growth was maximum between the globular and heart stage of embryo development. There after, the suspensor diminished and immediately after the torpedo stage, it degenerated several enzymes (e.g. acid-, alkaline-, adenosine triphosphatase, peroxidase, succinate dehydrogenase, cyotchrome oxidase) and general substances (ascorbic acid, polysaccharides, lipids) were localized in the suspensor during different phases of embryo growth. Between the globular and heartshaped stage, suspensor cells had strong reaction. An attempt is made to elucidate possible physiological functions in relation to specific enzyme localization. The possibility of suspensor having secretory function is also brought out. Present histochemical data indicated that suspensor was chiefly concerned with absorption and transport of metabolites from the surrounding tissue to the developing embryo.

Histocytochemistry↗
PubMed1977

Enzymic measurement of cholesterol in serum with the CentrifiChem centrifugal analyzer.

Cholesterol is measured by mixing 5 mul of sample with 350 mul of a reagent consisting of phenol, 4-aminoantipyrine, and the enzymes cholesterol oxidase, cholesterol esterase, and peroxidase. After 12 min, the resulting quinoneimine is measured at 520 nm. Readings and cholesterol concentrations are linearly related up to 4.0 g/liter. Lipemic sera and samples containing uric acid (up to 200 mg/liter), hemoglobin (up to 1 g/liter), and certain drugs (clofibrate, phenobarbital, nicotinic acid, Ketochol, Ovral-28), gave no interference. Abnormally high concentrations of bilirubin and ascorbic acid in serum lowered the cholesterol values. This enzymic assay, compared with the method of Abell and with a rate method that uses the Hantzsch reaction, gave correlation coefficients of 0.987 and 989, respectively.

Ascorbic Acid↗
PubMed1996

Protein stabilisation using additives based on multiple electrostatic interactions.

A method of elevating the storage lifetime of purified proteins has been discovered which appears to confer stability to all proteins investigated and may therefore be classed as generic in action. The basic methodology involves the formation of multiple electrostatic complexes between the protein and selected soluble polyelectrolytes to give protein-polyelectrolyte (PP) complexes and then to add solutions of polyalcohols or other compounds containing multiple hydroxyl groups. Dehydration of the resulting solution by vacuum evaporation, freeze drying or forced air convection produces a dry film or powder of stabilised protein. The method has been used mainly in the preparation of active enzymes for analytical tests. It has also been found that the formation of PP complexes also enhances the stability of enzymes in solution and the technique may be applicable to the stabilisation of virus suspensions by polycations. Examples of stabilised enzymes prepared by these methods are given and the proposed mechanism of stabilisation and applicability of the method to shelf-stable vaccine products are discussed.

Acrylates↗
PubMed1997

Whole-blood test for total cholesterol by a self-metering, self-timing disposable device with built-in quality control.

A whole-blood test for total cholesterol has been developed that is performed in a low-cost disposable flow device without user intervention (after sample addition). The device meters the sample, separates plasma from erythrocytes, and precisely times plasma flow into various reagent compartments, including a quality-assurance chamber. Test results are displayed as a well-defined and easily readable color bar. A quality-control window attests to the integrity of the test components. Here, we describe the assembly and individual functions of the device and report its performance characteristics. Precision and accuracy studies in four clinical studies at independent locations yielded total imprecision of <5% and an average bias of 1.35% vs the Abell-Kendall method.

Cholesterol↗
PubMedDate not supplied

Analysis of tear fluid by CE/LIF: a noninvasive approach for glucose monitoring.

Nanoliter volumes of human tear fluid were collected by means of a capillary tube without inducing tearing and were analyzed for glucose content. The tear fluid was subjected to two enzymatic reactions to generate a fluorescent compound that is proportional to the concentration of glucose in the sample. CE with laser-induced fluorescence (LIF) detection was used to monitor the fluorescent species generated, hence glucose in the tear samples. The reproducibility of the method for six different preparations was < 9% relative standard deviation (RSD). The procedure was compared with the glucose dehydrogenase method for the determination of glucose in blood before using it to determine glucose in tear fluid. Blood and tear samples were collected from six healthy human subjects. The results showed that the higher glucose content in tear samples is consistent with the higher glucose content in blood samples. The glucose concentration of the tear samples analyzed ranged from 128 to 166 microM, and that of blood ranged from 3.3 to 4.3 mM.

Blood Glucose↗
PubMed1971

Complex-formation between cytochrome c and cytochrome c peroxidase. Kinetic studies.

1. The kinetics of ferrocytochrome c peroxidation by yeast peroxidase are described. Kinetic differences between the older and more recent preparations of the enzyme most probably arise from differences in intrinsic turnover rates. 2. The time-courses of cytochrome c peroxidation by the enzyme follow essentially first-order kinetics in phosphate buffer. Deviations from first-order kinetics occur in acetate buffer, and are due to a higher enzymic turnover rate in this medium accompanied by a greater tendency to autocatalytic peroxidation of cytochrome c. 3. The kinetics of ferrocytochrome c peroxidation by yeast peroxidase are interpreted in terms of a mechanism postulating formation of reversible complexes between the peroxidase and both reduced and oxidized cytochrome c. Formation of these complexes is inhibited at high ionic strengths and by polycations. 4. Oxidized cytochrome c can act as a competitive inhibitor of ferrocytochrome c peroxidation by peroxidase. The K(i) for ferricytochrome c is approximately equal to the K(m) for ferrocytochrome c and thus probably accounts for the observed apparent first-order kinetics even at saturating concentrations of ferrocytochrome c. 5. The results are discussed in terms of a possible analogy between the oxidations of cytochrome c catalysed by yeast peroxidase and by mammalian cytochrome oxidase.

Acetates↗
PubMed1982

New procedure for detecting antinuclear antibodies using glucose oxidase immunoenzyme technic.

Enzyme glucose oxidase was used as the label on the secondary antibody in an indirect ANA-test procedure using rat kidney tissue as the antigen-source. Glucose oxidase is not endogenously present in mammalian tissues and, therefore, produces no background staining as obtained with flurochrome and peroxidase labels, which are commonly used to detect tissue antigens. Pseudoperoxidase-like activity of the haptoglobin-hemoglobin complexes in mammalian tissues is responsible for the interfering background stain when peroxidase label is used. Unlike Diaminobenzidine, the staining reagent commonly used with peroxidase, chromogenic reagents used with glucose oxidase are not carcinogenic. Glucose oxidase as a label for antibodies has advantages over flurochrome labels in being permanently stable, producing no background stain, and increasing the sensitivity of the method. Comparative evaluation of the glucose oxidase procedure and the commonly used flurochrome-ANA and peroxidase-ANA methods is reported. Results with 150 serum samples show the potential of this new method as a routine ANA-testing procedure in clinical laboratories.

Animals↗
PubMed1997

A proposed mechanism for p-aminoclonidine allergenicity based on its relative oxidative lability.

p-Aminoclonidine (apraclonidine) is a selective alpha 2 adrenergic agonist used to reduce intraocular pressure in the treatment of glaucoma. Use of apraclonidine is frequently associated with severe local allergic effects which warrant discontinuation of the drug in affected patients. We have assessed the oxidative lability of apraclonidine relative to a panel of adrenergic agonists and/or known allergens; amodiaquine, epinephrine, clonidine, and brimonidine. These compounds were compared by their electrochemical potentials as well as their oxidative lability in the presence of several oxidative enzyme systems (i.e., horseradish peroxidase, lactoperoxidase, myeloperoxidase, and diamine oxidase). The half-lives for enzymatic oxidation of these compounds were found to parallel the electrochemical oxidation potentials in the order: amodiaquine approximately epinephrine < apraclonidine << clonidine approximately brimonidine. The production of a reactive electrophilic intermediate of apraclonidine was demonstrated through the formation of two glutathione apraclonidine adducts from the horseradish peroxidase/H2O2-mediated oxidation of apraclonidine in the presence of glutathione. A mechanism for apraclonidine allergenicity in vivo is proposed wherein apraclonidine is bioactivated through oxidation to the bis-iminoquinone followed by protein conjugation to form an apraclonidine-protein hapten that elicits the immune response.

Adrenergic alpha-Agonists↗
PubMed1997

Heme peroxidase activity measured in single mosquitoes identifies individuals expressing an elevated oxidase for insecticide resistance.

Optimum conditions are described for a simple, rapid, microplate-based assay that indirectly measures the differences in oxidase levels between individual susceptible, resistant, or induced mosquitoes. A small proportion (0.01-0.1) of a single mosquito is used, allowing multiple replicates of the oxidase assay. Cytochrome C is used as a positive control. The levels of oxidase found in sample populations of pyrethroid-susceptible, pyrethroid-resistant, and phenobarbital-induced Anopheles albimanus mosquitoes are characterized with the assay.

Animals↗
PubMed1983

"Peroxidatic" form of cytochrome oxidase as studied by X-ray absorption spectroscopy.

X-ray absorption spectroscopy shows pulsed oxidase to be similar to resting oxidase but to lack the sulfur bridge between iron and copper of active sites (Powers, L., Y. Ching, B. Chance, and B. Muhoberac, 1982, Biophys. J., 37[2, Pt. 2]: 403a. [Abstr.] ) The first shell ligands and bond lengths of the pulsed oxidase active site heme most clearly fit the ferric peroxidases from horseradish and yeast, and the pulsed oxidase cyanide compound resembles the low spin hemoprotein cyanide compounds. The structural results are consistent with an aquo or a peroxo form for pulsed oxidase as is also observed by optical studies. These structural and chemical data are consistent with a role for the pulsed forms in a cyclic peroxidatic side reaction in which the pulsed and pulsed peroxide compounds act as peroxide scavengers. The peroxidatic role of cytochrome oxidase in the nonsulfur bridged form suggests the renaming of the "oxygenated" or "pulsed" forms on a functional basis as "peroxidatic" forms of cytochrome oxidase.

Chemical Phenomena↗
PubMed1984

Histochemical investigation of criteria for the distinction between monoamine oxidase A and B in various species.

The superior cervical ganglion (SCG), pineal body (PB), and liver (L) of the rat, rabbit and cat were stained for monoamine oxidase (MAO) A and B by the tetranitro blue tetrazolium (TNBT) and coupled peroxidase ( PerOx ) methods, using 5-hydroxytryptamine (5HT), tryptamine ( Tryp ), tyramine (Tyr), and benzylamine (Bz) as substrates, and clorgyline (Cl) and deprenyl (Dep), both at 10(-7) M, as selective inhibitors. The nodose ganglion (NG) and dorsal root ganglion (DRG) of the rabbit and cat were also studied. The results with rat tissues were consistent with published quantitative findings (SCG, MAO-A much greater than B; PB, MAO-A less than or equal to B; L, MAO-A = B). In the rabbit, the findings with the SCG were similar; the MAO activities of the PB were relatively resistant to both inhibitors; the MAO of the liver required 10(-4) M concentrations of both inhibitors to produce near total inhibition, suggesting that the liver contains an MAO distinct from MAO A and B. All cat tissues examined appeared to contain almost exclusively MAO-B. In this species 5HT, which is generally considered a selective substrate for MAO-A, was oxidized by MAO-B. The findings indicate that criteria for MAO-A, -B, and other subgroups must be defined for each species and tissue.

Animals↗
PubMed1993

Cytostatic effects of horseradish and thyroid peroxidase derived free radicals.

An otherwise noncytostatic flux of H2O2 from glucose and glucose oxidase became cytostatic to cultured Chinese Hamster Ovary (CHO) cells when horseradish or thyroid peroxidase was added to the culture medium. Electron spin resonance (ESR) measurements showed that one or more factors present in the culture medium promote the one-electron oxidation of a reduced nitroxide or glutathione in an H2O2/peroxidase-dependent process. Moreover, a reduced nitroxide conferred significant protection against the cytostatic effect of H2O2/peroxidase. Cytostatic effects were not only seen in the presence of the active H2O2/peroxidase system, but also in media which had been preexposed to H2O2/peroxidase but no longer contained an active H2O2 generating system. It is suggested that peroxidases oxidize one or more factors in tissue culture media to free radicals, which react with nearby components of cells or form toxic products, causing growth inhibition. If similar free radical precursors are present in tissue fluids, some of the toxicity of H2O2 in vivo may be due to peroxidase-mediated endogenous free radical generation.

Animals↗