Lymphocytes were incubated with various long chain fatty acids bound to albumin. Incubation for 20 h with unsaturated fatty acids resulted in uptake into the neutral lipids and phospholipids. The addition of concanavalin A enhanced the uptake. With the unsaturated fatty acids the rotational relaxation time of 1,6-diphenyl-1,3,5-hexatriene (DPH) was decreased, while with saturated fatty acids there was only a very small effect. The effect on the rotational relaxation times with unsaturated fatty acids was found to be due to the formation of lipid droplets in the cytoplasm. When plasma membrane free of lipid droplets was prepared, there was no effect on the rotational relaxation time despite incorporation of either linoleate or palmitate into the membrane phospholipids. Phospholipid liposomes prepared from plasma membranes obtained from cells which had been cultured with and without exogenous linoleate gave identical rotational relaxation times regardless of the history of the cells from which they were obtained. It is concluded that although the fatty acid composition of lymphocyte plasma membrane can be modified by exogenous fatty acids, there is little effect on the degree of order of the membrane phospholipid fatty acyl chains as monitored by the effects on the rotational relaxation time of DPH.

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Finance, staffing and equipment constraints may offer significant impediments to troponin testing with a 1-h turnaround time.

HCl production are discussed.

SUMMARY.A method is described based on a reaction that requires magnesium-ATP as a co-factor for the activity of hexokinase (HK), coupled with glucose 6-phosphate dehydrogenase (G6PDH). Glucose and NADP are converted to D-gluconolactone 6-phosphate and NADPH. respectively. The rate of increase in absorbance at 340 nm due to the formation of NADPH is proportional to the magnesium concentration in the sample. Magnesium levels in serum and urine measured by the enzymic method compared well with those obtained by atomic absorpton spectrometry.The within-batch precisions were 1·4% and 1·5% for the enzymic method and the atomic absorption method. respectively for a quality assurance sample with a magnesium concentration of 2 mmoVL. The enzymic method is accurate (recoveries of added magnesium to serum samples are 101-102%), reproducible (between batch CV 2·8%). and rapid (23 samples may be measured in to min). Data on accuracy, precision and correlation for the enzymic and atomic absorption methods are presented. concentration. This method is. however. also time-consuming and not well suited for use in a routine laboratory. The end point assay is a three-step manual procedure, measured at 30"C. involving a 5 min pre-incubation. a 15 min incubation in the presence of the enzyme mixture and the addition of EDTA to stop the reaction. We describe the automation of the enzymic method to give a single step kinetic assay at 37°C using a centrifugal analyser. The method simplifies batch analysis and gives savings on reagent costs. An annual supply of all the reagents would be less than £100 for 25 mL of reagent mixture per week which is sufficient for 46 samples plus the standards for calibration.The effect of different concentrations of reagent components on the linearity of the reaction rate at 3JOC has been examined; this is particularly important as the reaction is measured kinetically rather than as an endpoint assay. Good correlation of the enzymic method with the atomic absorption method has been demonstrated using serum and urine samples. Analytical recovery and interference 'studies are reported.

Additional key phrases: carbamylated haemoglobin; cation exchange chromatography; thiobarbituric acid; endosmosis Glycated haemoglobin has been widely accepted as a valuable indicator of diabetic control.' The proportion of glycated haemoglobin after removal of the labile glycated haemoglobin fraction correlates with the long-term control of blood glucose, but is also affected by red cell survival.In addition, in uraemia, an apparent elevation of glycated haemoglobin has been found. This has been attributed to the presence of carbamylated haemoglobin which is formed by the reaction of cyanate derived from urea with the N-terminal amino group of haemoglobin. Carbamylated haemoglobin is co-eluted with glycated haemoglobin in cation exchange chromatography.2-5 When glycated haemoglobin is measured by a chemical method using thiobarbituric acid, carbamylated haemoglobin interference is absent .2-5 The carbamylated haemoglobin effect had not been reported with the electroendosmosis method used in our laboratory to measure stable glycated haemoglobin. A study to measure glycated haemoglobin in patients with varying degrees of renal failure and diabetic control was carried out to validate its usefulness in patients with chronic renal failure. METHODSGlycated haemoglobin was measured by electroendosmosis (Ciba-Corning Diagnostic Ltd, Halstead, Essex, UK) with prior removal of labile glycated haemoglobin by incubation with saponin/ labile fraction removal buffer at 37°C for 15 min. Between batch imprecision was 6% (coefficient of

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