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Biomedical subjects

G G Guilbault

Publications and source records attributed to G G Guilbault.

At least 91 records · Page 5Linked to original sources
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↗
PubMed1975

Enzymatic determination of serum urea on the surface of silicone-rubber pads.

An enzymatic, fluorometric method is described for determination of serum urea on silicone-rubber pads. In this method, the reagents are lyophilized on the surface of the pads, NADH on one side and a mixture of urease, glutamate dehydrogenase, and alpha-ketoglutarate on the other. The rate of disappearance of NADH fluorescence at 460nm (excitation wavelength, 340 nm) is monitored and related to serum urea concentration. The calibration curve is linear to 250 mg of urea per liter. The method affords a rapid, simple, and inexpensive means for urea assay, the results of which correlate well with automatic diacetyl monoxime method (correlation coefficient, 0.998).

Drug Stability↗
PubMed1975

Fluorometric assay of serum acid or alkaline phosphatase, either in solution or on a semisolid surface.

We describe enzymatic fluorometric methods for determining activities of serum alkaline phosphatase and of serum acid phosphatase in solution and on silicone rubber pads. 4-Methylumbelliferone phosphate is used as substrate, in either tris(hydroxymethyl)aminomethane or citrate buffer. In solution, the reaction is measured at 37 degrees C in a 3-ml Pyrex cuvette. Measurements on the pads are also made at 37 degrees C, after establishing a stable substrate film by lyophilizing all reagents on the surface of the pads. Only 20 to 30 mul of substrate solution, 50 mul of buffer solution, and 1 to 10 mul of blood are necessary, making a total volume of 51 to 60 mul for each assay. The rate of appearance of the fluorescent 4-methylumbelliferone liberated from 4-methylumbelliferone phosphate by the enzymatic action is measured and equated to enzyme activity. Calibration plots of the change in fluorescence per minute vs. enzyme activity for measurements in solution and on pads show a good proportionality in the range of 30.8 to 633 U/liter for alkaline phosphatase and in the range of 0.265 to 5.3 King-Armstrong units for acid phosphatase, indicating the usefulness of these methods in the clinical laboratory.

Acid Phosphatase↗
PubMed1975

Semi-solid surface fluorometric analysis of glucose.

We describe an enzymatic fluorometric method for determining glucose concentrations in blood samples by analysis on a semi-solid surface (silicone-rubber pads). The method is an adaptation of existing spectrophotometric procedures based on the sequential coupling reactions with glucose-6-phosphate dehydrogenase and NADP+. The rate of appearance of NADPH fluorescence at 460 nm (excitation wavelength, 340 nm) is monitored and related to the glucose concentration in plasma or serum. The calibration curve is linear to 2.50 g/liter. The chief advantages of this method over the spectrophotometric procedure are low cost and rapid response. The results obtained correlate well with those of the o-toluidine method (correlation coefficient, 0.986).

Binding Sites↗
PubMed1975

Fluorometric assay of serum gamma-glutamyltransferase in solution and on a semi-solid surface.

We describe an enzymatic, fluorometric method for measuring the activity of serum gamma-glutamyltransferase (EC 2.3.2.2) in solution and on silicone rubber pads. N-gamma-L-Glutamyl-alpha-naphthylamide in tris(hydroxymethyl)aminomethane buffer is used as substrate. In solution, measurements are performed at 37 degrees C with use of a reaction volume of 3.0 ml, in Pyrex cuvets. Measurements on silicone rubber pads are also made at 37 degrees C, after establishing a stable substrate film by lyophilizing the reagent for the gamma-glutamyltransferase assay on the surface of the pads. Only 10-50 mul of buffered substrate and serum containing the enzyme to make a total volume of 60 mul are necessary for each assay. The rate of appearance of alpha-naphthylamine fluorescence (lambda ex equals 344 nm; lambda em equals 445 nm), liberated from N-gamma-L-glutamyl-alpha-naphthylamide by the enzymatic action of gamma-glutamyl-transferase, is measured and equated to its activity in serum. Calibration plots of the change in fluorescence per min vs. enzyme concentration for measurements in solution and on pads show a good proportionality in the range of 26.5-265 U/liter, and indicate the usefulness of these methods.

Amides↗
PubMed1975

Fluorometric enzymatic determination of total cholesterol in serum.

We describe a fluorometric enzymatic method for determining total serum cholesterol, based on hydrolysis of cholesterol esters to free cholesterol by cholesterol ester hydrolase (EC 3.1.1.13). The free cholesterol formed, as well as that initially present, is then oxidized by cholesterol oxidase (EC 1.1.3.6) to cholest-4-en-3-one with simultaneous production of hydrogen peroxide. The latter catalytically oxidizes homovanillic acid in the presence of peroxidase (EC 1.11.1.7) to form the highly fluorescent 2,2'-dihydroxy-3,3'-dimethoxy-biphenyl-5,5'-diacetic acid. A calibration curve is constructed from data on a series of standard cholesterol solutions vs. the corresponding fluorescence change (deltaf/5 min). This curve is linear up to 4.0 g of total serum cholesterol per liter of serum. The method is specific, precise, accurate, rapid, and simple, and results correlate well with those obtained by both the Liebermann-Burchard procedure and the colorimetric enzymatic method (correlation coefficients, 0.984 and 0.981, respectively).

Alcohol Oxidoreductases↗