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Biomedical subjects

G G Guilbault

Publications and source records attributed to G G Guilbault.

At least 55 records · Page 3Linked to original sources
PubMed1986

A study of interferences in glucose measurements in blood by hydrogen peroxide based glucose probes.

The main blood constituents which could interfere in clinical glucose measurements using a hydrogen peroxide based glucose electrode have been investigated using several different membranes and constant and sweeping potentials. Both diluted and whole undiluted sera were investigated. With a 3500 molecular weight cut-off (MWCO) membrane, acetaminophen, cysteine, and ascorbic acid can interfere. With a 100 MWCO membrane, only acetaminophen interfered.

Blood Glucose↗
PubMed1986

Clinical uses of enzyme electrode probes.

Clinical applications of enzyme electrochemical sensors are reported; they are based on the coupling of enzymes with potentiometric membrane electrodes (pH, iodide), or potentiometric probes (ammonia, carbon dioxide) or amperometric devices (oxygen, hydrogen peroxide). The most popular and successful immobilization procedures for enzymes are reviewed, namely physical entrapments and chemical methods for binding enzymes to solid support like collagen and nylon net; procedures specifically developed for clinical uses of enzyme probes. The simplicity of the apparatus is evidenced, and it is explained how a single instrument can be useful for all kind of measurements. Practical suggestions for constructing a typical probe are given. Single paragraphs are devoted to the determination of urea, cholesterol, creatinine, amino acids, glucose, lactate, protein, choline and acetylcholine to clarify the sequence of enzymatic and electrochemical reactions in order to elucidate the application range, the sensitivity and the selectivity as well as the relevant interferences for each metabolite either in the enzymatic or in the electrochemical step. The applications performed in vitro, in vivo and ex vivo and the commercial availability of some instruments are reported.

Acetylcholine↗
PubMed1986

The cardiolipin antigen: chemistry and composition.

Cardiolipin, the primary lipid hapten in the antigen suspension used for the detection of antitreponemal antibodies in the sera of syphilitic patients, was successfully coupled to glucose oxidase, peroxidase, and some other enzymes using different crosslinking agents. These complexes were used to replace the pure uncomplexed cardiolipin for the preparation of the antigen suspension. When these suspensions were allowed to react with serum that contained anticardiolipin antibodies the activity of the enzyme was inhibited. In the absence of antibody, no enzyme inhibition was observed.

Antibodies, Bacterial↗
PubMed1980

Fluorometric enzymatic determination of serum creatinine on the surface of silicone-rubber pads.

An enzymatic semi-solid surface fluorometric method is described for the determination of serum creatinine on silicone-rubber pads. In this method, the glutamate dehydrogenase, alpha-ketoglutarate, ADP and NADH are mixed, then 30 microliters of diluted serum is added. After the free ammonium ion in serum is consumed, creatininase is added to initiate the assay. The rate of disappearance of NADH fluorescence at 460 nm (excitation wavelength 340 nm) is monitored and is proportional to the serum creatinine concentration. The whole assay uses only 0.41 I.U. creatininase, and takes less than 5 min. The calibration curve is linear up to 82 mg creatinine per liter. The proposed method offers a rapid, simple and inexpensive means for creatinine assay. The results obtained correlate well with the modified Jaffe method applied on Technicon SMA 12/60, with a correlation coefficient of 0.998. The recovery averages 99.3%.

Adenosine Diphosphate↗
PubMed1980

Fluorometric and colorimetric enzymic determination of triglycerides (triacylglycerols) in serum.

We describe two fully enzymic methods, fluorometric and colorimetric, for determination of triglycerides (triacylglycerols) in serum. Samples are incubated with microbial lipase for 10 min, and the glycerol released from the triglycerides is oxidized by NAD+ in the presence of glycerol dehydrogenase. In the fluorometric method, the resulting NADH is in turn oxidized by resazurin as catalyzed by diaphorase to form resorufin, a highly fluorescent compound. In the colorimetric method, the NADH is oxidized by coupling with a tetrazolium salt/diaphorase system to form formazan, a highly colored compound. Calibration curves, constructed by plotting change in fluorescence or absorbance vs concentration of triglycerides, were linear up to 6 and 5 g of triglycerides per liter of serum for the fluorometric and colorimetric methods, respectively. The assays require only 5 and 15 microL of serum for fluorometry and colorimetry, respectively. The CV was 0.59% for the fluorometric method, 0.91% for the colorimetric procedure. The time for analysis for either method is less than 15 min. The results correlate well with those obtained by the Dow Diagnostic Kit method, a colorimetric method in which glycerol kinase and glycerol-1-phosphate dehydrogenase form NADH from ATP and NAD+ in the presence of glycerol and glycerol 1-phosphate.

Colorimetry↗
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↗