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At least 1,441 records · Page 80Linked to original sources
PubMed1988

Electrostatic interactions of 4-carboxy-2,6-dinitrophenyllysine-modified cytochromes c with physiological and non-physiological redox partners.

An analysis of the effect of electrostatic properties of 4-carboxy-2,6-dinitrophenyllysine (CDNP-lysine) cytochromes c on their reactions with strongly and weakly binding redox partners is given. For strongly binding systems (cytochrome-c oxidase, cytochrome-c reductase, sulphite oxidase and yeast cytochrome-c peroxidase) the magnitude of the dipole moments of the CDNP cytochromes c determines their relative reactivities. For weakly binding redox agents, such as hexacyanoferrate(III), cobalt(III)tris(1,10-phenanthroline), azurin and plastocyanin, the electrostatic potential at the haem edge accounts for the greater part of the relative activities. Relative rate data were obtained from the literature. It is concluded that the dipole moment of native cytochromes c may account for an approx. 50-fold increase in the efficiency of its physiological activity towards membrane-bound enzymes. A correction on a formula to describe the contribution of a molecular dipole moment to the ionic strength dependence of a bimolecular rate constant (Koppenol, W. H. (1980) Biophys. J. 29, 493-508) leads to an equation nearly identical to that obtained by Van Leeuwen et al. (Van Leeuwen, J.W., Mofers, F.J.M. and Verrman, E.C.I. (1981) Biochim. Biophys. Acta 635, 434-439).

Azurin↗
PubMed1977

Evaluation of automated glucose oxidase methods for serum glucose: comparison to hexokinase of a colorimetric and an electrometric method.

Two automated glucose oxidase methods have been evaluated with respect to accuracy, precision, recovery, linearity and various potential interferences. Trinder's method on an AutoAnalyzer II had a between-day coefficient of variation (C.V.) of 2.6% (mean 228 mg/dl), was linear to 500 mg/dl, and produced a mean recovery of 99.7%. Comparison of Trinder's method with a manual, blanked hexokinase method yielded the regression equation: TR=--1.95 + HEX (1.04); Spearman's rho correlation coefficient was: 0.974. The Beckman System I glucose method had a between-day C.V. of 1.6% (mean 198 mg/dl), was linear to 500 mg/dl, and recovered an average of 98.0% of added glucose. Comparison with the same hexokinase method yielded: SYI = 1.27 + HEX (1.02: Spearman's rho = 0.991. None of the possible interfering compounds tested caused significant deviation of results by either method within the range of concentrations encountered physiologically. Trinder's method on the AutoAnalyzer II and the System I method are accurate, precise methods and are highly recommended for routine use in the clinical laboratory.

Autoanalysis↗
PubMed1980

Determination of uric acid with uricase and peroxidase.

A reliable method for the determination of uric acid in plasma or serum is described. The hydrogen peroxidase developed in the uricase reaction is used, together with peroxidase, for the coupling of sulphonated dichlorophenol and 4-aminoantipyine to a red dye. The difference in absorbance at 515 nm before and after addition of uricase is measured. Of the components tested for interference some gave rise to falsely lowered values. Reagents are cheap and the high molecular absorption coefficient of the red dye permits the use of small sample volumes.

Humans↗
PubMed1988

Construction of dry reagent chemistries: use of reagent immobilization and compartmentalization techniques.

The development of dry reagent systems has provided convenience to the user as well as devices that are more versatile and suitable for a variety of analyses. Most dry reagent chemistries are usually less than 7 cm2 by 300 micron thick packaged as discrete test devices. This reduces spoilage of unused reagents. Sample volumes needed for analysis are usually in the range of 3-30 microliter, with 10 microliter most commonly used. The use of such small volumes makes these devices suitable for neonatal and geriatric patients where large sample volumes are not often available. Hence, 150 microliter of serum (approximately 300 microliter blood) is sufficient for at least 15 different analyses on a sample. Dry reagent chemistries are easy to store, readily available for use, and disposable. Only application of a sample is needed to start an analysis.

Blood Chemical Analysis↗
PubMed1989

Use of the glucose oxidase/peroxidase method for glucose assay leads to overestimation of the inhibition of gluconeogenesis by aminopyrine.

4-Aminoantipyrine strongly inhibits glucose determination by the glucose oxidase/peroxidase/dianisidine assay but does not interfere in the assay using glucose-6-phosphate dehydrogenase, hexokinase and ATP. As a result, the inhibition of gluconeogenesis by aminopyrine reported to be 50-90% (Bánhegyi, G., Mandl, J., Antoni, F. and Garzó, T. (1987) Biochim. Biophys. Acta 927, 406-416) is strongly overestimated and amounts to only 10-30%.

Aminopyrine↗
PubMed1990

Metabolic activation of natural phenols into selective oxidative burst agonists by activated human neutrophils.

Phenols isolated from the traditional medicinal plant Picrorhiza kurroa inhibit the release of superoxide anion (O2-) by activated human neutrophils, but leave the phagocytotic capacity intact. Resting neutrophils and resting or activated human lymphocytes are insensitive to these agents. The underlying mechanism of this highly selective activity is investigated. A critical event is the reaction of the phenols with secretory products from the activated neutrophils. The reaction products interfere with the assembly of a functional NADPH-oxidase in the membrane. Analysis of the mode of activation of the phenols reveals two possible pathways. Catechols react directly with reactive oxygen species (ROS) from the oxidative burst. For the activation of the orthomethoxy-substituted catechols the combined activity of ROS and myeloperoxidase (MPO) is obligatory. Catechols with a dimethoxy substitution cannot be activated metabolically by neutrophil-derived ROS.

Biotransformation↗
PubMed2005

Bienzyme HRP-GOx-modified gold nanoelectrodes for the sensitive amperometric detection of glucose at low overpotentials.

Gold nanotubular electrode ensembles were prepared by using electroless deposition of the metal within the pores of polycarbonate track-etched membranes. Mono-enzyme (GOx) and monolayer/bilayer bienzyme (GOx/HRP) bioelectrodes were prepared by immobilizing the enzymes onto gold nanotubes surfaces modified with mercaptoethylamine. Batch amperometric responses to glucose for the different bioelectrodes were determined and compared. The response of the two geometries (monolayer and bilayer) of the bienzyme electrodes was shown to vary with regard to sensitivity at detection potentials above 0V. On the contrary, at detection potentials below 0V, no noticeable influence of the configuration of the bienzyme on the response intensity was observed. The mono-enzyme (650 microAmM-1 in benzoquinone (BQ) at -0.8 V versus Ag/AgCl) and the two bienzyme bioelectrodes (+/-400 microAmM-1 in hydroquinone (H2Q) at -0.2V versus Ag/AgCl) display remarkable sensitivities compared to a classical GOx-modified gold macroelectrode (13 microAmM-1 in BQ at -0.8 V versus Ag/AgCl). A remarkable feature of the bienzyme electrodes is the possibility to detect glucose at very low applied potentials where the noise level and interferences from other electro-oxidizable compounds are minimal. Another important characteristic of the monolayer bienzyme electrode is the possible existence of a direct electronic communication between HRP and the transducer surface.

Biosensing Techniques↗
PubMed2006

Proteins modified with DNAzymes or aptamers act as biosensors or biosensor labels.

Hybrid systems composed of a glucose oxidase (GOx)/peroxidase-mimicking DNAzyme, and of microperoxidase-11 (MP-11)/anti-thrombin aptamer were synthesized. The hybrid systems were employed as amplifying labels for the colorimetric or chemiluminescence detection of an enzyme functions, and thrombin analysis, respectively. In the GOx/DNAzyme system, the GOx-mediated oxidation of glucose led to the formation of H(2)O(2), and this activated the oxidation of ABTS to a colored product, or to the generation of chemiluminescence in the presence of luminol. The MP-11/anti-thrombin aptamer enabled the amplified analysis of thrombin by the MP-11-mediated generation of chemiluminescence in the presence of luminol/H(2)O(2).

Aptamers, Nucleotide↗
PubMed2005

Reduction of acute cisplatin ototoxicity and nephrotoxicity in rats by oral administration of allopurinol and ebselen.

Cisplatin ototoxicity has been associated with the generation of toxic levels of reactive oxygen species (ROS) which can lead to injury or loss of outer hair cells in the organ of Corti, damage to the stria vascularis, and loss of spiral ganglion cells, resulting in permanent hearing loss. In an attempt to reduce the formation of ROS and to bolster the innate oxidative stress defenses of the cochlea, we tested individual and combined formulations of allopurinol, a xanthine oxidase inhibitor, and ebselen, a glutathione peroxidase mimic. We used an acute cisplatin toxicity rat model (16 mg/kg i.p.) to analyze allopurinol and ebselen alone and in combination for their ability to reduce cisplatin associated hearing loss and nephrotoxicity. The results from our studies indicate that a combined formulation of ebselen and allopurinol affords significant protection to the cochlea and kidney from cisplatin toxicity. In the cochlea, protection is dependent on the preservation of outer hair cell number, while in the kidney, protection is associated with the preservation of proximal tubular epithelia. Further evaluation of the chemoprotective effects of ebselen and allopurinol on cisplatin side effects in the presence of tumor appears warranted.

Administration, Oral↗
PubMed2006

L-carnitine attenuates oxidative stress in hypertensive rats.

The present study aimed to investigate whether l-carnitine (LC) protects the vascular endothelium and tissues against oxidative damage in hypertension. Antioxidant enzyme activities, glutathione and lipid peroxidation were measured in the liver and heart of spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats. Nitrite and nitrate levels and total antioxidant status (TAS) were evaluated in plasma, and the expression of endothelial nitric oxide synthase (eNOS) and p22phox subunit of NAD(P)H oxidase was determined in aorta. Glutathione peroxidase activity was lower in SHR than in WKY rats, and LC increased this activity in SHR up to values close to those observed in normotensive animals. Glutathione reductase and catalase activities, which were higher in SHR, tended to increase after LC treatment. No differences were found in the activity of superoxide dismutase among any animal group. The ratio between reduced and oxidized glutathione and the levels of lipid peroxidation were respectively decreased and increased in hypertensive rats, and both parameters were normalized after the treatment. Similarly, LC was able to reverse the reduced plasma nitrite and nitrate levels and TAS observed in SHR. We found no alterations in the expression of aortic eNOS among any group; however, p22phox mRNA levels showed an increase in SHR that was reversed by LC. In conclusion, chronic administration of LC leads to an increase in hepatic and cardiac antioxidant defense and a reduction in the systemic oxidative process in SHR. Therefore, LC might increase NO availability in SHR aorta by a reduction in superoxide anion production.

Animals↗
PubMed2002

Effects of short- and long-term (--)-deprenyl administration on mRNA for copper, zinc- and manganese-superoxide dismutase and glutathione peroxidase in rat brain.

The effect of short-term (3 weeks, 2 mg/kg day) and long-term (12 and 20 months, 0.5 mg/kg day) administration of (-)-deprenyl on the mRNA expression of three neuroprotective enzymes in subdivisions of rat basal ganglia was investigated. In situ hybridisation histochemistry with oligodeoxynucleotide probes was used to measure levels of copper, zinc superoxide dismutase (Cu,Zn-SOD), manganese superoxide dismutase (Mn-SOD), and glutathione peroxidase (GPX) mRNA. The 3-week administration of (-)-deprenyl caused a significant increase in Cu,Zn-SOD mRNA in the nucleus accumbens (NA) (P<0.05), striatum (CP) (P<0.01), and globus pallidus (GP) (P<0.05), but had no effect on Mn-SOD or GPX mRNA levels throughout basal ganglia. In rats which received (-)-deprenyl for 12 months, there was a significant increase in Mn-SOD mRNA in the NA, CP, GP, and substantia nigra (SN) (all P<0.05); there were no changes in either Cu,Zn-SOD or GPX mRNA. Except for the significant increase in Cu,Zn-SOD mRNA in SN pars compacta (SC) (P<0.05), by 20 months there were almost no differences between (-)-deprenyl-treated and age-matched control animals that had received equivalent injections of saline. We conclude that (-)-deprenyl administration can induce mRNA expression for both forms of SOD, but the effects are variable and not sustained over 20 months.

Animals↗