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Biomedical subjects

G G Guilbault

Publications and source records attributed to G G Guilbault.

At least 19 recordsLinked to original sources
PubMed1977

An immobilized hexokinase enzyme stirrer for a simple and economical assay of plasma glucose.

We have adapted the hexokinase glucose procedure to an immobilized enzyme stirrer for the determination of glucose concentrations in human blood plasma. The procedure is a fluorometric rate method measuring the formation of NADPH catalyzed by immobilized glucose-6-phosphate dehydrogenase and hexokinase held within a tiny stirrer. The enzyme stirrer is stable for at least two months and can be used over eight-hundred assays without any loss of activity.

Blood Glucose↗
PubMed1977

Amperometric determination of total cholesterol in serum, with use of immobilized cholesterol ester hydrolase and cholesterol oxidase.

We describe an electrochemical method for simple, rapid, and economical assay of total serum cholesterol with use of immobilized cholesterol esterase (EC 3.1.1.13) and cholesterol oxidase (EC 1.1.3.6). A rotating porous cell was specially designed to hold the immobilized enzymes firmly and to allow the reaction mixture to pass through the enzyme layer easily, thus catalyzing the enzymatic transformation quickly. Hydrogen peroxide resulting from a catalytic reactions was measured amperometrically at +0.60 V cs. a standard calomel electrode. The calibration curve for total serum cholesterol was linear from 0 to 5.00 g/liter. The method is specific, precise, and inexpensive. Our results correlate well with those obtained by the method of Abell et al. [Stand. Methods Clin. Chem. 2, 26 (1958)], the correlation coefficient being 0.992. Ascorbic acid or bilirubin in concentrations up to 700 mg/liter do not interfere. The immobilized enzymes are stable, and the same immobilized-enzyme stirrer can be used for at least 200 accurate, reproducible assays.

Carboxylic Ester Hydrolases↗
PubMed1977

Fluorometric estimation of triglycerides in serum by a modification of the method of Bucolo and David.

An enzymic, flurometric method is described for determination of triglycerides (and glycerol) in blood serum, a modification of the method of Bucolo and David [Clin. Chem. 19, 476 (1973)]. Commercially available reagent kits are used. The rate of disappearance of NADH fluorescence at 460 nm (excitation wavelength, 365 nm) is monitored and related to serum triglyceride concentration, corrected for the content of free glycerol. We compared the results obtained fluorometrically to the ultraviolet spectrophotometric Boehringer Neutral Fat method used at Gentofte Hospital, Copenhagen. Instrument response and concentration were linearly related in the range 0.27 to 2.7 mmol of triglycerides per liter of serum with the fluorometric method. The CV was 0.9% for the fluorometric method, 3.7% for the spectrophotometric procedure. The fluorometric method requires less reagents, time, and calculations than does the spectrophotometric method.

Fluorometry↗
PubMed1977

Determination of plasma glucose with use of a stirrer containing immobilized glucose dehydrogenase.

A stirrer containing immobilized glucose dehydrogenase has been successfully used for determining glucose in plasma. The device is usable for at least two months and for about 500 assays. The reaction was measured kinetically and linearity was observed to 4 g of glucose per liter. Tested with aqueous glucose and with deproteinized plasma, within-day and day-to-day precision were good. Interference and method-comparison (hexokinase method) were examined. The performance of this system makes the technique useful and attractive for routine use in small-volume clinical laboratories.

Blood Glucose↗
PubMed1976

Measurement of glucose in plasma, with use of immobilized glucose oxidase and peroxidase.

We describe a novel fluorometric technique for simple, rapid, and economical assay of glucose by use of immobilized glucose oxidase and peroxidase. A cylindrical magnetic stirrer was specially designed to hold the immobilized enzymes firmly and to allow the reaction minzymic transformation quickly. Blood plasma can be assayed directly with no pretreatment. Ascrobic acid, uric acid, and creatinine in concenctrations of 0.25, 0.25, and 0.2 g/liter, respectively, did not interfere. The linearity of the assay was extended to 4.0 g of glucose concentrations. Results by our technique and by the otoluidine or hexokinase methods agreed well. The immobilized enzymes are stable for several months and can be used for several hundred highly accurate and reproducible assays.

Aspergillus niger↗
PubMed1976

Enzymatic, fluorometric assay of alpha-amylase in serum.

An enzymatic, fluorometric method for kinetic assay of serum alpha-amylase (1,4alpha-D-glucan 4-glucanohydrolase, EC 3.2.1.1) is described. A soluble starch is used as substrate, in tris(hydroxymethyl)methylamine buffer. All measurements are made in Pyrex cuvettes at 37 degrees C, with a reaction volume of 1.16 ml. The assay is based on the following reaction sequence: (see article) The rate of appearance of fluorescence of NADH (lambdaex = 365 nm, lambdaem = 460 nm), developed in the indicator reaction (4), is measured and equated to the activity of alpha-amylase in serum. A calibration plot of the change of fluorescence per min vs. enzyme concentration shows a good proportionality in the range of 0.50-5.0 kU/liter.

Amylases↗
PubMed1975

An alternative method for the determination of uric acid in serum.

A novel fluorometric method for the determination of uric acid based on the coupled reactions of uric acid with uricase and peroxidase to form highly fluorescent 2,2'dihydroxy-3,3'-dimethoxy-biphenyl-5,5'-diacetic acid is described. The calibration curve was constructed from a series of standard uric acid solutions vs. the corresponding relative fluorescence. It was linear up to 15 mg/dl (0.9 mmol/l). The serum or plasma samples must be deproteinated with (absolute) ethanol before assay and its uric acid content can be obtained from the calibration curve. This method is rather simple, having good precision and accuracy. High level ascorbic acid in the sample falsely elevates uric acid concentration. Comparison of the results obtained on the patient sera with a colorimetric phosphotungstate method and a standard enzymatic spectrophotometric method gave coefficients of correlation of 0.908 and 0.986, respectively.

Ascorbic Acid↗
PubMed1975

Ion-selective electrodes and enzyme electrodes in environmental and clinical studies.

Electrodes have been developed for the assay of glucose, urea, amino acids, uric acid, phosphate, nitrate and perchlorate. The electrodes for the organic compounds are enzyme electrodes which are prepared by chemically immobilizing an enzyme over the outside of a conventional ion-selective electrode. These electrodes will be discussed in depth. The progress and the development of the electrodes that show sensitivity and selectivity for phosphate, nitrate and perchlorate will be outlined. The basis of these sensors is a complex of a transition metal of either an analog of thiourea or an organic chelator, such as 1,10-phenanthraline. Such electrodes respond linearly to phosphate, nitrate or perchlorate, and show selectivity over sulphate, halides and acetate. The linear range of all these electrodes is approx. 10(-1)-10(-5) M with a near Nernstian slope and a reproducibility of 1%. The electrodes are stable and can be used continuously.

Amidohydrolases↗