Proton (1H) magnetic resonance spectroscopy: absolute metabolite concentrations in normal aging human brain at 3Tesla

Session - Normal Aging Brain: Computer 90 (Tuesday)OBJECTIVES: Absolute quantitation of metabolite levels of normal aging human brain has rarely been done. But using a 3T scanner, which provides better signal-to-noise ratio, spectrum with higher resolution can be obtained. MRS can explore aging at a molecular level but controversial findings had been reported in previous frontal lobe studies [1,2] In this study, we investigate in the relationship between regional concentrations of …published_or_final_versionThe 19th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2011), Montreal, QC., 7-13 May 2011. In Proceedings of the 19th ISMRM, 2011, v. 19, p. 404

Prevalence-adjusted bias-adjusted κ values as additional indicators to measure observer agreement

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Novel optical biotest for determination of cyanide traces in marine fish using microbial cyanide hydratase and formate dehydrogenase

A novel and simple enzymatic method for the determination of trace cyanide in marine fish is presented. This method is based on the conversion of metal-cyanide complexes by a fungal enzyme extract containing cyanide hydratase ( E. C. 4.2.1.66; CyHT) and formamidase ( E. C. 3.5.1.49) into formate and ammonia. The formate produced in the sample pre-treated with the fungal enzymes was measured by adding formate dehydrogenase ( E. C. 1.2.1.2; FDH) and excess NAD(+). The NADH formed accordingly was monitored at 340 nm. The cyanide calibration curve was found to be linear in the range of 10 - 100 muM, and the detection limit was 1.1 muM (0.0286 ppm). The proposed biotest was successfully applied to the determination of trace cyanide in a tropical marine food fish species ( Russell's Snapper (Lutjamus russellii)) which had been exposed to cyanide

Combination of quantitative MR hippocampal volumetry and arterial spin labeling MR perfusion in differentiating patients with alzheimer disease from cognitively normal older adults

Session SS10. Neuroradiology - Brain: no. 06

Amperometric determination of lactate with novel trienzyme/poly(carbamoyl) sulfonate hydrogel-based sensor

A novel trienzyme sensor for the amperometric determination of lactate was constructed by immobilizing salicylate hydroxylase (SHL, E.C. 1.14.13.1), L-lactate dehydrogenase (LDH, E.C. 1.1.1.27), and pyruvate oxidase (PyOD, E.C. 1.2.3.3) on a Clark-type oxygen electrode. The enzymes were entrapped by a poly(carbamoyl) sulfonate (PCS) hydrogel on a Teflon membrane. LDH catalyzes the specific dehydrogenation of lactate consuming NAD+. SHL catalyzes the irreversible decarboxylation and the hydroxylation of salicylate in the presence of oxygen and NADH produced by LDH. PyOD decarboxylates pyruvate using oxygen and phosphate. SHL and PyOD force the equilibrium of dehydrogenation of lactate by LDH to the product side by consuming NADH and pyruvate, respectively. Dissolved oxygen acts as an essential material for both PyOD and SHL during their respective enzymatic reactions. Therefore, an amplified signal, caused by the consumptions of dissolved oxygen by the two enzymes, was observed in the measurement of lactate. Regeneration of cofactor was found in the trienzyme system. A Teflon membrane was used to fabricate the sensor in order to avoid interferences. The sensor has a fast response (2 s) and short recovery times (2 min). The total test time for a measurement by using this lactate sensor (4 min) was faster than using a commercial lactate testing kit (up to 10 min). The sensor has a linear range between 10 and 400 muM lactate, with a detection limit of 4.3 muM. A good agreement (R-2 = 0.9984) with a commercial lactate testing kit was obtained in beverage sample measurements. (C) 2004 Elsevier B.V. All rights reserved

An amperometric bi-enzyme sensor for determination of formate using cofactor regeneration

A biosensor for detection of formate at submicromolar concentrations has been developed by co-immobilizing formate dehydrogenase (FDH, E.C. 1.2.1.2), salicylate hydroxylase (SHL, E.C. 1.14.13.1) and NAD(+) linked to polyethylene glycol (PEG-NAD(+)) in a poly(vinyl alcohol) (PVA) matrix in front of a Clark-electrode. The principle of the bi-enzyme scheme is as follows: formate dehydrogenase converts formate into carbon dioxide using PEG-NAD+. Corresponding PEG-NADH produced is then oxidized to PEG-NAD(+) by salicylate hydroxylase using sodium salicylate and oxygen. The oxygen consumption is monitored with the Clark-electrode. The advantages of this biosensor approach are the effective re-oxidation of PEG-NADH, and the entrapment of PEG-NAD(+) resulting in avoiding the addition of expensive cofactor to the working medium for each measurement. This bienzyme sensor has achieved a linear range of 1-300 muM and a detection limit of 1.98 x 10(-7) M for formate (S/N = 3), with the response time of 4 min. The working stability is limited to 7 days due to the inactivation of the enzymes. Only sodium salicylate was needed in milli-molar amounts. (C) 2002 Elsevier Science B.V. All rights reserved

Application of cyanide hydrolase from Klebsiella sp in a biosensor system for the detection of low-level cyanide

A partially purified preparation of cyanide hydrolase ( cyanidase) from a bacterium, Klebsiella sp., was applied as a biocatalyst in a biosensor system for low-level cyanide detection. In the biosensor system cyanide hydrolase converts cyanide into formate and ammonia. The formate produced in the cyanide degradation was detected with a formate biosensor, in which formate dehydrogenase (FDH; E. C. 1.2.1.2) was co-immobilized with salicylate hydroxylase (SHL; E. C. 1.14.13.1) on a Clark electrode. The principle of the formate sensor is that FDH converts formate into carbon dioxide using - nicotinamide adenine dinucleotide hydrate (NAD(+)). The corresponding NADH produced is then oxidized to NAD(+) by SHL using salicylate and oxygen. The oxygen consumption is monitored with the Clark electrode. The optimum buffer pH and temperature for the enzymatic hydrolysis of potassium cyanide were studied. The preliminary experiments including the pretreatment of cyanide with cyanide hydrolase and then detection by the formate sensor gave a detection limit at 7.3 mu mol l(-1) cyanide. The linear range of the calibration curve was between 30 mu mol l(-1) and 300 mu mol l(-1) cyanide