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Biomedical subjects

J E Buttery

Publications and source records attributed to J E Buttery.

At least 55 records · Page 3Linked to original sources
PubMed1984

Evaluation of Ketostix for plasma acetoacetate.

Acetoacetate in plasma is measured conveniently by Ketostix (Ames, Miles Laboratories, Elkhart, IN), a reagent strip test. The color formed on the reactive tip by the acetoacetate after 15 seconds is compared with the color chart provided for quantitation. When the concentration is between 4 to 12 mmol/L, the authors recommend a reassay using a diluted sample and both results averaged. Results thus determined agreed well with those obtained by a GC method. Analyst bias in color matching is not a serious problem. Ketostix stability and user performance are discussed in relation to quality control.

Acetoacetates↗
PubMed1984

Blood ammonia measurement using a simple reflectometer.

We have assessed a compact Blood Ammonia Checker System (Ammonia Checker) consisting of a reflectometer which measures the intensity of colour formed by blood ammonia on a bromocresol green indicator reagent plate. The results show good correlation (r = 0.95) with our routine chemical method and a regression line y = 0.835X - 1.468. The Ammonia Checker has good precision (CV less than 10%) at the critical blood ammonia concentration and accurately measures predetermined ammonia concentrations. Blood sampling is improved with a precision pipette. The Ammonia Checker is simple, convenient and reliable and is ideally suited for a laboratory required to perform an urgent blood ammonia measurement.

Ammonia↗
PubMed1983

Erythrocyte ammonia in liver disease.

This study reports the relevance of plasma and erythrocyte ammonia concentrations in patients with liver disease. Three groups of subjects were studied: group 1, 47 normal subjects; group 2, 73 patients with liver disease; and group 3, 14 patients with portal-systemic encephalopathy (PSE). The difference in plasma ammonia concentrations between groups 1 and 2 was not significant, but for erythrocyte ammonia this was significant (p less than 0.05). Group 3 subjects had significantly elevated plasma (p less than 0.001) and erythrocyte ammonia (p less than 0.001) compared with the other two groups (Mann-Whitney U-test). In group 3, two patients had plasma ammonia values within the reference range, whereas six patients had values within the range of group 2 subjects. However, none of group 3 subjects had erythrocyte ammonia concentrations within the range of either group 1 or 2. A cut-off level of 65 mumol/l was assigned to differentiate group 3 from group 2 subjects. We conclude that erythrocyte ammonia measurement is a better biochemical index of PSE than plasma ammonia.

Adolescent↗
PubMed1983

Determination of urinary oxalate with commercially available oxalate oxidase.

For this direct colorimetry of urinary oxalate, commercially available oxalate oxidase (EC 1.2.3.4) is used. The urine is first diluted, to diminish the effect of interfering substances. Analytical recovery of oxalate from urines with five different oxalate concentrations (0.4 to 2.0 mmol/L) ranged from 92 to 109% (mean 99%). The within-day and between-day precision (CV) of the method for a wide range of oxalate concentrations averaged better than 10%. There is good correlation (r = 0.977) between this enzymatic method (y) and the chemical method of Hodgkinson and Williams (x) [Clin Chim Acta 36: 127-132, 1972], the regression equation being y = 1.014x + 0.061. Urines with added ascorbate give falsely increased results. The proposed method is inexpensive and simple to perform.

Charcoal↗
PubMed1982

A note of caution on the use of the LD ratio in myocardial infarction.

Different LD1/LD2 ratios for both normal and pathological samples were obtained with two different reagent kits. These ratio differences are due to the substrate formulation and not to the electrophoresis separation technique. In 45 patients with abnormal serum "cardiac" enzymes, results obtained by the two kit methods showed 17% and 50% "flipped ratio" abnormalities as against 78% and 67% abnormalities when the ratios were compared against appropriate reference ranges. The improper use of the LD ratio test is probably the main cause for its diminished diagnostic usefulness.

Colorimetry↗
PubMed1982

The measurement of erythrocyte ammonia using the Hyland Ammonia kit.

We modified the Hyland Ammonia kit for plasma to measure blood ammonia from which the erythrocyte ammonia is calculated. Our modified method gave good recoveries and its precision based on replicate assays was excellent (CV less than 3.0%). The within-day and day-to-day precision was determined from pooled blood and aqueous ammonia solution respectively. The precision calculated from duplicate results was not as good but agreed with other published values. A critical examination of Hyland's method showed the efficiency of resin adsorption to be 78%, and that the resin caused a 16% reduction in the Berthelot reaction, while 4 mol/l NaCl increased the reaction by about 11%. Blood specimens for ammonia can be frozen but specimen instability occurred during the thawing process. Measurement of ammonia directly on frozen specimens overcomes this problem. The reference range for erythrocyte ammonia was 14.5-46.1 (mean 30.1, SD 7.9) mumol/l.

Adsorption↗
PubMed1982

Plasma acetaminophen results are method dependent.

The management of patients who have taken large amounts of acetaminophen is often determined by the plasma level of the drug in relation to the time after ingestion. Nomograms or tables defining the risk of the hepatic damage for a given level at a particular time usually refer to the plasma-free acetaminophen concentration. It is important therefore that the assay used measures only free acetaminophen and not its inactive conjugates of glucuronide and sulfate. Two simple colorimetric methods were compared to assess the interference of acetaminophen conjugates. The method of Frings and Saloom measured both conjugates. Furthermore, these conjugates are not completely hydrolyzed, averaging about 22 and 85% hydrolysis for the glucuronide and sulfate conjugates, respectively. The method of Glynn and Kendal is little affected by acetaminophen conjugates and gives a better measure of the free drug. Interference by salicylates, although slight, can be corrected using modifications in the method.

Acetaminophen↗
PubMed1981

An appraisal of CSF glutamine measurement by acid hydrolysis.

The hydrolysis of CSF glutamine as proposed by Harst et al. (2) was shown to be incomplete due to the low acid concentration in the reaction. Complete hydrolysis was achieved with a higher acid concentration. Because glutamine is stoichiometrically converted to ammonia and glutamic acid, both ammonia and glutamine can be used as standard solutions. It was further shown that glutamine standard solution, even though deaminated, can still be used. CSF urea, if very high, will give falsely elevated glutamine concentrations. Correction is possible by subtraction of its glutamine equivalent value. An optimum Berthelot reaction was developed for our modified assay.

Ammonia↗
PubMed1980

Correction for the suppressive effect of haemoglobin on NADH absorbance in the transketolase assay.

The kinetic transketolase assay measures the absorbance change of NADH in the presence of haemoglobin. Haemoglobin was shown to suppress NADH absorbance which resulted in an apparently lower enzyme activity. To minimise this suppression, the transketolase assay was performed on samples with haemoglobin concentration of 30 g/l. At this level the absorbance of NADH in the presence of haemoglobin averaged 90.5% of that in Tris buffer. It is proposed that the calculation of the enzyme activity should be corrected for this suppression.

False Negative Reactions↗
PubMed1980

Reappraisal of the uroporphyrinogen I synthase assay, and a proposed modified method.

Problems encountered in the uroporphyrinogen I synthase assay were found to be due to the Triton reagent, slit-width and excitation wavelength settings of the spectrophotofluorometer, and leg-phase in the enzyme reaction. Of Triton X-100 from four suppliers, only three were found suitable. Differences in enzyme activity owing to slit-width adjustments were resolved by measuring the fluorescence of the sample (uroporphyrin) at 405 nm and the standard (coproporphyrin) at 401 nm. The lag-phase in the activated-enzyme assay is incorporated in the 30-min preincubation of the blood specimen in our modified method, thus giving higher enzyme activity than found with the original assay. The range for our method is 7.3--15.8 nmol s-1 L-1 (mean = 10.9; SD = 2.07).

Ammonia-Lyases↗
PubMed1980

Detection of alkaline phosphatase/immunoglobulin complexes.

We report another patient with a circulating alkaline phosphatase/immunoglobulin complex in his blood, and describe a simple method of demonstrating such complexes. On electrophoresis on cellulose acetate, the complex was relatively slow moving and there was no activity in the normal bone/liver isoenzyme region. When the serum was treated with trypsin, the slow band disappeared and the normal pattern was restored.

Aged↗
PubMed1979

The effect of pre-incubation and direct procedure for the alanine transaminase assay in two kits compared.

The kinetic measurement of serum alanine transaminase was carried out on two enzyme kits (Roche and Calbiochem), done as a direct method and a pre-incubation method. Variable results from commercial control sera and patient sera by these four procedures were obtained. Pre-incubation enzyme values were generally lower than the direct values (mean difference 10%), but there were marked differences between the results from the two kits. This finding has important significance especially for laboratories participating in external QC Programmes. Frequent precision checks of the method and a local reference range are therefore necessary.

Alanine Transaminase↗