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Biomedical subjects

D C Turnell

Publications and source records attributed to D C Turnell.

At least 19 recordsLinked to original sources
PubMed1989

Automation of liquid chromatographic techniques for biomedical analysis.

The complete automation of liquid chromatographic (LC) techniques increases their work capacity and makes them more acceptable for biomedical applications. The ability to analyse priority specimens is also advantageous. The areas to be considered in a fully automated LC are reviewed in terms of the analytical operations, the types of processing and the various control systems that can be adopted. In particular, sample preparation and liquid handling are described in detail together with techniques and equipment that can be utilised for their automation. Strategies are given for the rational design of a fully automated LC that can analyse raw samples completely unattended.

Autoanalysis↗
PubMed1988

Automated sequential trace enrichment of dialysates and robotics. A technique for the preparation of biological samples prior to high-performance liquid chromatography.

The development of the sample preparation process, the automated sequential trace enrichment of dialysates, in association with a cartesian robotic sampler is described. The system has been applied to the total automation of the preparation of biological samples and high-performance liquid chromatographic analysis. Concepts of the technique are reported together with an examination of its application to free and total analyte estimation. Examples of chromatographic separations obtained from the preparation of a variety of different analytes and sample materials are given.

Amino Acids↗
PubMed1988

Why the assay of serum cystine by protein precipitation and chromatography should be abandoned.

The higher bias of serum cystine estimations by a HPLC method compared with those by ion exchange techniques is shown to be largely due to differences in the sample preparation procedures of the two techniques. The ion exchange methods utilised sulphosalicylic acid serum protein precipitation and post-column ninhydrin derivatisation of cystine, whilst the high pressure liquid chromatography technique employed automated dialysis for removal of proteins and pre-column ortho-phthalaldehyde derivatisation of cystine after its conversion to cysteine and then to S-carboxymethylcysteine. Examination of these procedures showed that whilst the high pressure liquid chromatographic method accurately estimates total serum cystine and cysteine, many factors affect the precision and accuracy of serum cystine estimations using the ion exchange techniques. In particular, serum protein precipitation techniques that are currently employed for the preparation of samples for cystine analysis by ion exchange chromatography should be abandoned.

Blood Proteins↗
PubMed1986

Automatic preparation of human serum samples for analysis of the drug enoximone and its sulphoxide metabolite using high-performance liquid chromatography.

A method for the estimation of the cardiotonic drug enoximone and its major sulphoxide metabolite, in serum, is described. The method uses a new technique for the preparation of biological material prior to the separation of analytes using high-performance liquid chromatography. This technique has been described as the automated sequential trace enrichment of dialysates (ASTED). The sample preparation process operates concurrently with the chromatographic separation. Aliquots of 500 microliters of serum are required for the analysis of serum from patients who have received a single 75-mg dose of enoximone. Within- and between-run coefficients of variation were found to be 2.8 and 3.9% for enoximone and 2.5 and 3.7% for enoximone sulphoxide. These values were obtained from estimating serum supplemented with enoximone and its metabolite, at concentrations of 0.5 and 1.0 mg/l, respectively.

Autoanalysis↗
PubMed1986

What is the role of histidine in studies of faecal mutagenicity?

Mutagenicity testing can be used to assay faeces for genotoxic substances and the results are reported to correlate with population risk for colorectal cancer (Ehrich et al., 1979). It has been suggested that histidine in faeces may cause false positive results (Venitt and Bosworth, 1983). To determine the relationship between histidine and false positive mutagenicity assays aliquots of non-mutagenic faecal extract and saline were supplemented with histidine and subjected to the Ames Salmonella/mammalian microsome mutagenicity assay (Ames et al., 1975). Using high-pressure liquid chromatography the analytical recovery of histidine from water and faecal extract supplemented with histidine was equivalent (r = 0.998, p less than 0.001). Histidine was measured in faecal extracts (1 in 10 dilutions) from 35 volunteers, 10 patients with inflammatory bowel disease and 4 with rectal cancer. These extracts were also assayed for mutagens using the Salmonella/mammalian microsome mutagenicity assay. None of the faecal extracts gave mutagenicity ratios above 2. Faecal extracts from volunteers were free of detectable histidine. Although 9 of those from inflammatory bowel disease patients contained histidine (mean +/- SEM 255 +/- 34 mumoles l-1) as did 1 extract from a rectal cancer patient (50 mumoles l-1), none contained sufficient histidine to give a false positive Salmonella/mammalian microsome mutagenicity assay result (800 mumoles l-1 in test solution). Our results do not implicate histidine as a cause of error in faecal mutagenicity testing by the Salmonella/mammalian microsome mutagenicity assay.

Chromatography, High Pressure Liquid↗
PubMed1985

Investigations of long-term treatment with perhexiline maleate using therapeutic monitoring and electromyography.

Experience is reported with 41 patients taking perhexiline maleate for angina pectoris for periods of up to 70 months, while serum concentrations of the drug were monitored, and liver function tests and electromyographic tests were made before and during treatment. Severe side effects did not occur unless serum perhexiline levels were greater than 1.5 mg/L. The drug seems effective for prolonged dosage, and the monitoring of weight, liver function test results, and serum concentrations should prevent or reduce toxicity. A starting dose of 100 mg daily is recommended. The drug is not recommended for routine use in angina pectoris.

Adult↗
PubMed1985

The calibration of total serum bilirubin assays.

Bilirubin assays yield variable results due to the lack of a universal calibrant. The preparation of a bilirubin calibrant is associated with the following problems: (a) only unconjugated bilirubin is available in a 'pure' form and this is of doubtful stability, (b) the test for its purity is arbitrary, (c) the true molar absorptivity of bilirubin is unknown, (d) due to the various specificities of methods, the calibrant has to be in a protein matrix, (e) the matrix alters the properties of bilirubin and (f) there is no definitive bilirubin assay. The use of a lyophilised human-based bilirubin calibrant should permit accurate standardisation of the method of Jendrassik and Grof and that of Hertz.

Azo Compounds↗
PubMed1985

Therapeutic monitoring of the anti-anginal drug perhexiline maleate.

Patients taking oral doses of perhexiline maleate have been examined. Measurement of serum perhexiline concentrations established that different dose requirements between patients were necessary due to the different doses at which drug saturation was achieved. Measurement of serum perhexiline concentrations are essential if side-effects from the drug are to be avoided.

Angina Pectoris↗
PubMed1984

The stability of the o-phthalaldehyde/2-mercaptoethanol derivatives of amino acids: an investigation using high-pressure liquid chromatography with a precolumn derivatization technique.

The investigation of the stabilities of o-phthalaldehyde/2-mercaptoethanol derivatives of amino acids using a precolumn reaction technique and a high-pressure liquid chromatographic procedure is reported. The amino acid derivatives are shown to be stable on the high-pressure liquid chromatography column. Optimal conditions for the development of these derivatives for their separation using this technique are recommended.

Aldehydes↗
PubMed1983

A rapid procedure for the simultaneous estimation of the anticonvulsant drugs, ethosuximide, phenobarbitone, phenytoin, and carbamazepine in serum using high-pressure liquid chromatography.

A rapid isocratic high-pressure liquid chromatography procedure for the analysis of ethosuximide, phenobarbitone, phenytoin, and carbamazepine in serum is described. The method employs a single extraction from serum; alumina treatment of this extract eliminates interference from fast-eluting compounds, allowing rapid chromatography. A linear response is obtained for drug concentrations up to three times the upper limit of the therapeutic ranges. Within-batch and between-batch precisions for the means of these ranges varied from 2.2 to 5.5% and from 3.1 to 7.5%, respectively.

Anticonvulsants↗
PubMed1982

The estimation of serum acid phosphatase using alpha-naphthyl phosphate as substrate: observations on the use of Fast Red TR salt in the assay.

The estimation of acid phosphatase (EC 3.1.3.2) in serum by reaction rate analysis, utilising alpha-naphthyl phosphate as substrate and a diazonium salt (Fast Red TR) for colour development is examined. In the absence of substrate the occurrence of a pseudo catalytic activity is shown to be due to the hydrolysis of the Fast Red TR with the subsequent production of 4-chloro-2-methylphenol. The 4-chloro-2-methylphenol reacts with the Fast Red TR to form an azo compound which absorbs at a wavelength of 340 nm. The production of 4-chloro-2-methylphenol during the reaction is first order with respect to the Fast Red TR concentration, is temperature dependent and is accelerated in the presence of human albumin or Triton X-100. Monitoring the reaction at a wavelength of 585 nm eliminates the need for substrate independent blank correction. The final reaction conditions are summarised, together with a comparison of the method with that of the Kind and King [9] procedure.

Acid Phosphatase↗
PubMed1982

The metabolic effects of moderately severe upper gastrointestinal haemorrhage in man.

The metabolic effects of moderately severe gastrointestinal haemorrhage were investigated in man. Before resuscitation, patients had raised circulating concentrations of glucose, lactate, alanine, glycerol and cortisol. After urgent operation for haemorrhage, metabolite concentrations were similar to those of control patients having elective abdominal surgery, but insulin concentrations were higher and cortisol lower in haemorrhage patients. There were no significant differences in nitrogen excretion between haemorrhage patients and their controls, but urinary 3-methyl-histidine excretion by haemorrhage patients was lower indicating decreased muscle protein breakdown. Decreased amino acid release from muscle might account for previously reported imparied wound healing after haemorrhage.

Alanine↗
PubMed1982

Rapid assay for amino acids in serum or urine by pre-column derivatization and reversed-phase liquid chromatography.

This method for estimating clinically important amino acids in serum or urine within 40 min involves o-phthalaldehyde/2-mercaptoethanol derivatization and reversed-phase "high-pressure" liquid chromatography. Homocysteic acid is an internal standard, and homoserine and norvaline are reference peaks. For all the amino acids estimated, the between-run coefficients of variation ranged from 2.0 to 13.5%, and the mean analytical recoveries from both serum and urine samples was 101%. Peak areas vary linearly with concentration up to 1500 mumol/L for all the amino acids assayed. The limit of detection for each amino acid was estimated to be 38 fmol.

Amino Acids↗