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Biomedical subjects

R A Bacchus

Publications and source records attributed to R A Bacchus.

17 recordsLinked to original sources
PubMed1988

A simple improved method for the measurement of cyclosporin by liquid-liquid extraction of whole blood and isocratic HPLC.

The current HPLC methods of cyclosporin measurement have been reviewed and all aspects assessed. A simple isocratic C-18 reverse phase HPLC method with improved efficiency is described for the routine measurement of cyclosporin in whole blood. An alkaline ether extraction is followed by an acid wash, solvent evaporation and two hexane washes of the reconstituted extract. The turn-round time for a single sample is 1 h. Daily batches of up to 40 patient samples can be easily measured with this method. The results are compared with those from the Sandoz radioimmunoassay (RIA) method.

Chromatography, High Pressure Liquid↗
PubMed1988

The Middle East external quality assessment scheme for clinical chemistry.

The establishment and first 7 years' operation of an external quality assessment scheme for clinical chemistry in the Middle East region are described. The scheme utilises specimens distributed previously in the UK, and the performance of participating laboratories is assessed relative to the UK consensus values, taking account of method. Variance Index scoring has been used to quantitate performance, and there has been an improvement in average scores during the operation of the scheme. There are currently 88 participants, though some laboratories which failed to return results regularly were removed from the scheme. The consensus values from the scheme itself have now been validated, and in future the scheme should operate independently.

Blood Chemical Analysis↗
PubMed1988

Influence of timing in the fructosamine assay.

The fructosamine assay, based on the measurement of the reducing activity in serum at alkaline pH, provides an index of protein glycation. The reducing activity is expressed in equivalents of 1-deoxy-1-morpholinofructose (DMF) by direct comparison with the activity either of this synthetic compound or with a secondary protein standard calibrated against DMF. This study reports the influence of assay timing on the apparent serum fructosamine concentration. The kinetics of alkaline reducing activity in serum differed from that in both DMF and a secondary protein standard. When compared with DMF, activity in serum increased but decreased relative to the protein standard as the pre-incubation interval of the assay was shortened. The use of secondary protein standards results in underestimation of serum fructosamine concentrations when the pre-incubation phase of the assay is shorter than that used for the calibration of the secondary standard. Ascorbate exerted an inhibitory effect in fructosamine assays with pre-incubation times exceeding 5 min. The inhibition increased with both the concentration of ascorbate and the duration of the pre-incubation.

Ascorbic Acid↗
PubMed1988

Serum fructosamine in diabetic pregnancy.

Serum fructosamine was measured in 275 blood donors, in 559 subjects with a normal pregnancy, in 32 gestational diabetics being treated with insulin and 69 being treated by diet only, and in 53 pregnant subjects with established diabetes. In none of the pregnant subgroups did the mean fructosamine concentration exceed that of the donor group. The concentration in normal pregnant subjects showed a modest but significant decrease with gestational age and an increase with maternal age. Hyperglycemic non-pregnant subjects (n = 24) had significantly increased serum fructosamine concentrations, and 96% of these subjects exceeded the upper 95% confidence limit for fructosamine in the donor group. A highly significant correlation was demonstrated between serum fructosamine and preprandial plasma glucose in the hyperglycemic subjects. A weak, but significant, correlation was shown for the entire population sample of antenatal patients, while this was non-significant within each of the sub-groups comprising established diabetics and gestational diabetics, respectively.

Adult↗
PubMed1987

Glucagon receptor binding, dissociation and degradation in rat liver plasma membranes studied by a microperifusion method.

The association process of glucagon receptor binding in purified rat liver plasma membranes and prolonged incubation of the hormone-receptor complex at 30 degrees C did not result in degradation of bound labelled glucagon. In contrast, up to 95% of the non-membrane-bound labelled glucagon was degraded. The rate of spontaneous dissociation of the glucagon-receptor complex was slow, and amounted to about 0.1% per min of that bound. GTP greatly enhanced the rate of dissociation. Half the maximal dissociation of the complex was effected by 10(-5) mol/l of GTP under equilibrium binding conditions. At maximally effective concentrations of GTP, 80% of the glucagon-receptor complex was dissociated within 2 min. A microperifusion system for the perifusion of isolated plasma membranes was devised and used for the separation of labelled glucagon from the plasma membranes subsequent to a GTP-induced dissociation of the hormone-receptor complex. Rebinding of the dissociated peptide to fresh membranes showed that maximum binding ability was retained. The glucagon molecule was protected against degradation while bound to the receptor, indicating that the glucagon effector system is completely separate from the inactivating system(s) in isolated plasma membranes. Thus, the hormonal effect of glucagon could be exerted through the sequential interaction of each glucagon molecule with several receptors.

Animals↗
PubMed1987

New, simple insulin-receptor assay with universal application to solubilized insulin receptors and receptors in broken and intact cells.

A new, simple insulin-receptor-binding assay has been devised. The assay is based on the separation of free and receptor-bound 125I-labeled insulin in 80% ethanol. It was found that the insulin-receptor complex was fully stable at this ethanol concentration, regardless of the source of the receptor employed. The assay has been evaluated with solubilized insulin receptors and membrane-bound receptors from human placenta and porcine liver as well as intact cells with the IM-9 cell line. The assay is simple, rapid, and has large capacity. Comparisons of the ethanol-based assay to the conventionally employed assays with polyethylene glycol or microfuge centrifugation for the separation of free and bound 125I-insulin revealed large discrepancies between the assays. The ethanol-based assay always appeared to provide a better separation. Microfuge centrifugation of placental membranes precipitated approximately 3% of the ethanol-precipitable insulin-receptor complex, while polyethylene glycol precipitation of solubilized insulin receptors varied between 40 and 80% of the ethanol precipitability, depending on the receptor concentration employed.

Cell Membrane↗
PubMed1983

Environmental effects on urinary volumes, biochemical constituents and their inter-relation.

This study has found low 24-h urine volumes in British expatriates in Saudi Arabia and suggests the possibility of urate stone formation in spite of the air-conditioned environment in which they were living. Urine volume was shown to be significantly correlated with calcium excretion in both sexes and to urate and sodium in males. Differences in 24-h urine concentrations of some but not all constituents between British-born subjects living in Britain and Saudi Arabia have been demonstrated.

Adult↗
PubMed1982

The prevalence of diabetes mellitus in male Saudi Arabs.

The prevalence of diabetes mellitus in 1385 males in the Al-Kharj area of Saudi Arabia was studied using the WHO criteria for screening and interpretation of glucose tolerance tests[1]. The prevalence was found to increase with age. No diabetic patients were found in the less than or equal to 24 year age group and only one (0.3%) in the age range: 25-34 years. There were seven (2.6%) in the age range: 35-44 years, 17 (9.6%) in the age range: 45-54 years, six (11%) in the age range: 55-64 years and three (23%) in the age range: greater than or equal to 65 years. The cases detected were relatively symptom free, but 65% of the diabetic patients were overweight.

Adolescent↗