Changes in serum concentration of antioxidants following treadmill exercise testing in patients with suspected ischaemic heart disease

Twenty-four subjects with suspected ischaemic heart disease underwent a treadmill exercise stress test (TEST). Nine individuals developed ischaemia as defined by standard criteria. Total plasma antioxidant status (TPAS), and serum concentrations of vitamin E were measured pre-TEST, and 0, 1, 2, 4, 8 and 24 h following the treadmill test. Mean serum vitamin E concentrations fell by 33% in the group as a whole (from 9.53 +/- 0.92 mg/L pre-TEST to 6.39 +/- 1.06 mg/L immediately post stress test, P < 0.02) and rose to baseline over the subsequent 24 h. The levels of serum vitamin E fell by 34% in the group of patients who had a positive TEST, and 32% in those who did not develop ischaemia during the TEST. Serum cholesterol concentrations also fell significantly during the TEST. In the total group serum cholesterol fell by 6.5% (P = 0.0052), and in the subgroup who were positive for ischaemia the fall in serum cholesterol was 10.3% (P = 0.004). The reduction in serum cholesterol was 4.1% in the subgroup who did not develop ischaemia (P > 0.05). Mean total plasma antioxidant status showed no significant temporal change for the group as a whole, although there was a nonsignificant decrease immediately post-TEST in the ischaemic group and a slight rise at 8 h in the group negative for ischaemia.

Changes in serum concentrations of markers of myocardial injury following treadmill exercise testing in patients with suspected ischaemic heart disease

BACKGROUND

The treadmill exercise test (TEST) is frequently used in patients with suspected ischaemic heart disease to establish a diagnosis and estimate future risk. However, its predictive value is poor. We aimed to investigate whether measurement of biochemical markers of myocardial injury could improve the diagnostic value of the procedure.

MATERIAL AND METHODS

Twenty-four subjects with suspected acute coronary syndrome underwent a treadmill exercise stress test. Of these 13 had had a previous myocardial infarction and two had a past history of coronary artery bypass grafting. Nine subjects were found to be positive for coronary ischaemia during the treadmill test. Serum cardiac markers (total creatine kinase [CK], CK-MB, Troponin I and Troponin T) were measured pre-TEST, and 0, 1, 2, 4, 8 and 24 hours following the treadmill test.

RESULTS

Total CK remained within the reference range for all subjects and showed no significant rise. However, mean serum concentrations of CK-MB were significantly higher than pre-test values at 2 hours (p < 0.03) following treadmill exercise testing in subjects who had a positive exercise stress test, but not in those with a negative test. In the subjects with a positive stress test, CK-MB levels returned to pre-Test value by 24 hours. Levels of neither serum troponin I, nor troponin T altered significantly at any point.

CONCLUSION

The measurement of CK-MB, but not cardiac troponins may add to the diagnostic utility of the TEST.

Comparison of a commercial enzymic kit for urinary oxalate analysis with a high performance liquid chromatographic method

A new commercial enzymic kit for urinary oxalate determination has been adapted for use on a centrifugal analyser. It has been evaluated and compared with an established high performance liquid chromatographic (HPLC) procedure developed in our laboratory. Mean recovery of oxalate from urine samples augmented with oxalic acid exceeded 97% by both methods. The precision of the HPLC method was superior to that of the enzymic kit but both methods gave between batch precision values better than CV 12% at low (less than 100 mumol/L) oxalate concentrations and better than CV 7% at higher concentrations (greater than 270 mumol/L). Urinary oxalate values obtained with the new enzymic procedure correlated more closely with HPLC values (r = 0.84) than did values previously obtained using the forerunner of the kit (r = 0.62) which was known to be susceptible to ascorbate interference. No significant interference from ascorbic acid or from high urinary calcium concentrations could be demonstrated using either the improved kit or the HPLC procedure. Its easy adaptation to automated analysers available in most laboratories, coupled to its acceptable analytical performance render the enzymic kit a reasonable alternative to HPLC or other more complex procedures for urinary oxalate analysis.

The determination of oxalate in urine and plasma by high performance liquid chromatography

We describe a simple, sensitive assay for oxalate in urine or plasma. Acidified urine is pretreated by dilution with neutral phosphate buffer and passage through a C18 cartridge. Stabilized plasma is diluted with neutral acetate buffer and oxalate extracted using a strong anion exchange cartridge. Treated samples are applied to an ion-paired chromatographic system and oxalate detected electrochemically. Recovery of oxalate from augmented samples exceeded 97% from both urine and plasma. Within- and between-assay coefficients of variation assessed at three concentrations were, respectively, better than 4.1% and 8.4% for urine and 3.9% and 5.2% for plasma. The reference range for urinary oxalate excretion is 109-497 mumols/24 h. The range for plasma oxalate concentration is 0.6-2.8 mumols/L or 0.7-3.9 mumols/L after an overnight fast or without dietary restriction, respectively. Urine and plasma oxalate concentrations from this method, gave correlation coefficients (r) of 0.97 and 0.98, respectively, when compared with those from established oxalate oxidase based assays.

Diagnostic significance of octadeca-9,11-dienoic acid in cervical neoplasia

The percentage molar ratio (%MR) of the 9,11 and 9,12 isomers of octadecadienoic acid was determined in cervical exfoliated cells from 148 subjects, of whom 27 had cytologically proven intraepithelial neoplasia and in cervical biopsy specimens from 43 subjects, of whom 24 had histologically diagnosed cervical intraepithelial neoplasia. The %MR in both cervical biopsy specimens and exfoliated cells did not significantly differ in subjects with or without cervical intraepithelial neoplasia. The measurement of the %MR of 9,11:9,12 octadecadienoic acid has no role in the detection of cervical intraepithelial neoplasia.

Paracetamol (acetaminophen) analysis by high performance liquid chromatography: interference studies and comparison with an enzymatic procedure

A simple, robust, high performance liquid chromatographic method for serum paracetamol determination in both the therapeutic and overdose concentration ranges is described. The within- and between-batch precision of the method was better than CV 5% at both micromolar and millimolar concentrations, and recovery of added paracetamol from drug-free serum exceeded 96%. No interference from any of the other drugs, drug metabolites, and dietary constituents tested was found. Performance data in the overdose concentration range has been compared with that from the enzymatic kit procedure, and results from the two assays showed good correlation (r = 0.97).

Determination of aluminium in serum: findings of an external quality assessment scheme

The analytical performance of laboratories participating in the serum aluminium programme of the Guildford Trace Element Quality Assessment Scheme has been evaluated. The considerable disparity between reported results was not attributable to the nature of the samples distributed, nor to the standard aluminium solutions used in different laboratories. All laboratories used electrothermal atomic absorption spectrometry but sample preparation procedures and temperature programmes varied enormously. While some laboratories performed better than others in the scheme, and the standard of analysis appears to be improving with time, no laboratory showed consistent acceptable performance.

Evaluation of a rapid high-performance liquid chromatographic method for plasma theophylline analysis and its use in therapeutic drug monitoring

A high-performance liquid chromatographic (HPLC) assay for theophylline has been developed and evaluated, and interferences eliminated. The method has been compared to an enzyme multiplied immunoassay technique (EMIT) with respect to cost and speed of analysis, recovery of added analyte, precision, accuracy, and performance in an external quality assessment scheme. The HPLC method, although less rapid than EMIT, was superior with respect to precision and less expensive to perform.

Determination of total bile acids in serum. A comparison of a radioimmunoassay with an enzymatic-fluorimetric method

A solid phase radioimmunoassay kit method for total conjugated bile acids has been compared to an enzymatic fluorimetric method for total serum bile acids. The methods were compared with respect to: precision, cross-reactivity (molar equivalence) of different bile salts, recovery of different bile salts from serum, the reference range for a healthy population, linearity, coefficient of correlation, diagnostic effectiveness, cost and ease of assay. Both assays seemed equally capable of predicting the presence or absence of liver disease. Radioimmunoassay had little advantage over the enzymatic-fluorimetric method. Its relative ease was far outweighed by its greater cost and poorer analytical performance.

Simpler flame photometric determination of erythrocyte sodium and potassium: the reference range for apparently healthy adults

Separated erythrocytes are washed repeatedly with iso-osmolar magnesium chloride solution, lysed by adding saponin, and sodium potassium measured in the diluted hemolysate by flame photometry. The coefficient of variation for the method was less than 4%. Reference intervals determined for a healthy population and hospitalized (elective surgery) patients without electrolyte disorders were 4.6-7.8 mmol/liter for erythrocyte sodium concentration and 94-110 mmol/liter for erythrocyte potassium concentration (2.5-97.5 percentiles).

Simpler flame photometric determination of erythrocyte sodium and potassium: the reference range for apparently healthy adults

Separated erythrocytes are washed repeatedly with iso-osmolar magnesium chloride solution, lysed by adding saponin, and sodium potassium measured in the diluted hemolysate by flame photometry. The coefficient of variation for the method was less than 4%. Reference intervals determined for a healthy population and hospitalized (elective surgery) patients without electrolyte disorders were 4.6-7.8 mmol/liter for erythrocyte sodium concentration and 94-110 mmol/liter for erythrocyte potassium concentration (2.5-97.5 percentiles).

Characterization of gastric mucoproteins isolated by equilibrium density-gradient centrifugation in caesium chloride

1. The mucoprotein from pig gastric mucus has been purified by equilibrium centrifugation in a CsCl gradient. 2. This procedure removes the non-covalently bound protein, which is closely associated with the mucoprotein and not easily removed from it by gel filtration. 3. The purified mucoprotein is separable by gel filtration into a high-molecular-weight mucoprotein A (mol.wt. 2.3x10(6)) and a low-molecular-weight mucoprotein B/C (mol.wt. 1.15x10(6)). 4. These two mucoproteins have the same chemical analysis namely fucose 11.3%, galactose 26%, glucosamine 19.5%, galactosamine 8.3% and protein 13.6%. 5. Mucoprotein A contains 3.1% ester sulphate. 6. These mucoproteins are isolated without enzymic digestion and have a higher protein content than the blood-group-substance mucoproteins from proteolytic digestion of gastric mucus. Detailed amino acid analysis shows that the extra protein in the non-enzymically digested material is composed of amino acids other than serine and threonine. 7. Mucoproteins A and B/C contain respectively 130 and 9 half-cystine residues per molecule of which about 78 and 6 residues are involved in disulphide linkages. 8. Cleavage of these disulphide linkages by mercaptoethanol splits both mucoproteins into four equally sized subunits of mol.wt. 5.2x10(5) for mucoprotein A and 2.8x10(4) for mucoprotein B/C. 9. The sole N-terminal amino acid of mucoprotein A is aspartic acid, whereas mucoprotein B/C has several different N-terminal amino acid residues.