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D Littlejohn

Publications and source records attributed to D Littlejohn.

At least 19 recordsLinked to original sources
PubMed2001

Quantitative analysis of low-field NMR signals in the time domain.

Two novel methods are described for direct quantitative analysis of NMR free induction decay (FID) signals. The methods use adaptations of the generalized rank annihilation method (GRAM) and the direct exponential curve resolution algorithm (DECRA). With FID-GRAM, the Hankel matrix of the sample signal is compared with that of a reference mixture to obtain quantitative data about the components. With FID-DECRA, a single-sample FID matrix is split into two matrices, allowing quantitative recovery of decay constants and the individual signals in the FID. Inaccurate results were obtained with FID-GRAM when there were differences between the frequency or transverse relaxation time of signals for the reference and test samples. This problem does not arise with FID-DECRA, because comparison with a reference signal is unnecessary. Application of FID-DECRA to 19F NMR data, which contained overlapping signals from three components, gave concentrations comparable to those derived from partial least squares (PLS) analysis of the Fourier transformed spectra. However, the main advantage of FID-DECRA was that accurate (<5% error) and precise (2.3% RSD) results were obtained using only one calibration sample, whereas with PLS, a training set of 10 standard mixtures was used to give comparable accuracy and precision.

Journal Article↗
PubMed2001

Application of an HPLC-FTIR modified thermospray interface for analysis of dye samples.

Previously, we developed a reversed-phase HPLC method compatible to high performance liquid chromatography diffuse reflectance Fourier-transform infrared (HPLC-FTIR) thermospray interface for the analysis of dyes. Dye separation achieved with a mixed-mode (SCX-ODS) column using a small gradient (90 to 80% water with acetic acid) and pH 3.25; 10 to 20% acetonitrile was considered to be suitable for HPLC-FTIR. A constant-voltage setting for the thermospray temperature (227 degrees C) was successfully used for this gradient condition. The HPLC-separated components deposited as a series of concentrated spots on a moving tape were scanned by specially developed HPLC-FTIR software. Excellent repeatability of the thermospray deposition FTIR chromatograms and IR spectra was obtained. The interface-derived spectra of the separated components of formulated and purified reactive dyes were compared and differences in spectral features were observed.

Journal Article↗
PubMed2000

Column leaching and sorption experiments to assess the mobility of potentially toxic elements in industrially contaminated land.

Made-up ground collected from layers of a trial pit excavated on a former industrial site was treated with artificial rainwater in a series of column leaching and sorption experiments. Metal mobility and the ability of various layers of material obtained from the pit to act as sources or sinks of potentially toxic elements were assessed. Samples from different layers varied in their abilities to raise the pH of rainwater applied at pH 3.5 and 4.3, and this was reflected in the amounts of metals mobilised by the rainwater as it percolated through the soil column. Material from the top two layers of the pit released cadmium, copper, manganese, lead, nickel and zinc to the aqueous phase, but the lower layers, with higher buffering capacity, were able to resist acidification even when the equivalent of 12 months' rainfall (western UK) was applied. Column sorption experiments confirmed the ability of material from layer 4 (48-50 cm) to take up copper, manganese and zinc. Metals were determined in the leachates by flame and electrothermal atomic absorption spectrometry and principle anions by ion chromatography.

Adsorption↗
PubMed1999

Australia's breast surgery workload is changing: comparison of a metropolitan and a rural hospital.

BACKGROUND: Breast cancer is a common disease in our community and its incidence is increasing. As a result of the improvements in community awareness and introduction of screening, patients are being diagnosed with earlier breast cancer and with a higher incidence of pre-invasive disease. Improvements in radiology, often coupled with minimally invasive diagnostic modalities, have lessened the requirement for open diagnostic biopsies and also reduced the number of operations for benign breast disease. METHODS: An audit of the surgical workload at Prince of Wales/Prince Henry Hospitals and Tamworth Base Hospital was conducted to document and compare the above changes in the metropolitan and rural settings. This study was conducted between 1987 and 1996 to assess the effect of screening and improved technology over a 10-year period. RESULTS: The study found that a high percentage of malignant lesions are being diagnosed by fine-needle aspiration biopsy (FNAB) with a corresponding reduction in open biopsy rate at the Prince of Wales Hospital. There is a smaller percentage of benign operations in both settings with a reduction of equal proportion. The reporting of the pathology specimens has markedly improved at both institutions. There has been a reduction in the number of patients having modified radical mastectomy and there has been a corresponding increase in breast conservation surgery especially at the Prince of Wales/Prince Henry Hospitals, although there was an unexpectedly high incidence of breast conservation surgery at Tamworth Base Hospital in 1987. In 1996 the rates of breast conservation surgery were the same in both hospitals. CONCLUSIONS: There are minimal differences in the quality of surgical care being offered to patients at the Tamworth Base Hospital compared with the Prince of Wales Hospital and both institutions are within reach of the accepted best management practices available.

Australia↗
PubMed1996

Determination of citrate in plasma protein solutions by UV-visible spectrophotometry and ion chromatography.

Two procedures were compared for the determination of citrate in plasma protein solution (PPS). Ion chromatography with gradient elution was preferred to an enzymatic-spectrophotometric method for citrate concentrations in the range 0.4-11 mg l-1. Better comparisons of results by both methods were obtained for citrate concentrations at the g l-1 level, as dilution of the PPS reduced interferences in the enzymatic procedure.

Blood Proteins↗
PubMed1996

Distribution of selenium in human blood plasma and serum.

A method has been developed which separates the three major selenium-containing proteins found in human blood serum and plasma: selenoprotein-P, glutathione peroxidase and albumin. They were separated from plasma or serum by affinity chromatography and the Se content determined directly by ETAAS. Selenoprotein-P is retained on a heparin-Sepharose column, and subsequently eluted with an excess of heparin, while glutathione peroxidase is separated by a blue-Sepharose column. The amount of Se associated with albumin was assumed to be the Se remaining in the rest of the sample. The detection limit of the ETAAS method, when applied to the separated fractions, was 0.8 microgram l-1 (2 ng absolute) and the accuracy of the determination was confirmed by comparison with spectrofluorimetry. The distribution of Se in the serum or plasma of 21 healthy people was determined, showing that 53 +/- 6% of the total present is associated with selenoprotein-P, 39 +/- 6% as glutathione peroxidase and 9 +/- 4% as albumin.

Adult↗
PubMed1996

Improved molecular fluorescence method for the determination of selenium in biological samples.

A procedure for the determination of selenium in whole blood and urine has been improved by optimization of the digestion and derivatization procedures. An overnight pre-digestion step with 4 + 1 concentrated nitric-perchloric acids reduced the time of mineralization at 170 degrees C from 4 h to 30-45 min. Conversion of all the selenium to selenite (SeIV) was optimized by addition of 1 ml of concentrated hydrochloric acid, with heating to 100 degrees C for 30 min. The rate of formation of the 2,3-diaminonaphthalene (DAN) complex of selenium was improved by heating to 70-100 degrees C for a minimum of 30 min. Co-addition of hexane during derivatization simplified the extraction procedure. The modified method was applied successfully to the analysis of Seronorm quality control whole blood and urine (83 and 24 micrograms l-1 Se, respectively). Samples from 12 healthy adults, gave results in expected ranges (mean concentrations of 75 +/- 8 micrograms l-1 in blood and 25 +/- 8 micrograms l-1 in urine). The structure of the Se-DAN complex was investigated using elemental analysis, FTIR spectrometry, 1H and 13C NMR spectroscopy, and FAB MS. The information obtained indicates that the selenodiazo group does not contain an Se-O bond or protonated nitrogens, as proposed in other studies.

Adult↗
PubMed1995

Direct determination of selenium in human blood serum and plasma by electrothermal atomic absorption spectrometry.

A method is described for the direct determination of selenium in serum or plasma by electrothermal atomic absorption spectrometry with deuterium-arc background correction. Samples are diluted (1 + 2) with a modifier containing palladium nitrate and Triton X-100. Samples are atomised from a L'vov platform in a pyrolytically-coated electrographite tube and peak area signals are measured. Direct determination is possible by using selenium standards matched to the physiological concentrations of sodium chloride, calcium and phosphate. The detection limit is 6 micrograms/L in the original sample. Precision at a selenium concentration of 97 micrograms/L was 2.2% RSD within batch and 3.0% RSD between batch. Accuracy is shown by (i) analysis of a Seronorm reference serum (value obtained 97 +/- 3 micrograms/L; recommended value 96 micrograms/L); (ii) recovery of added selenium (93.3 +/- 6.7% and 98.2 +/- 3.3% at additions of 30 and 60 micrograms/L, respectively) and (iii) comparison of results with mean of all laboratories in an external quality assessment scheme.

Calibration↗
PubMed1993

Determination of lead in urine by electrothermal atomic absorption spectrometry with probe atomization.

An automated graphite-probe atomizer was used for the direct analysis of diluted (2- to 12.5-fold) urine samples by electrothermal atomic absorption spectrometry (ETAAS). The method was applied successfully to the determination of Pb in reference materials, quality control urines and patient samples. The concentrations found were mainly in the range 7-93 micrograms dm-3 and agreed well with results obtained by an established ETAAS method, which involved chelation of Pb and solvent extraction into isobutyl methyl ketone. The detection limit, based on three times the standard deviation of the blank, was 4 micrograms dm-3 at 283.3 nm and 2 micrograms dm-3 at 217.0 nm. Although probe atomization removed chemical interferences for peak-area measurements, 10-20% suppression remained for some samples with peak-height measurements.

Chelating Agents↗
PubMed1993

Rapid partial digestion of biological tissues with nitric acid for the determination of trace elements by atomic spectrometry.

Determination of Cu, Fe, Mn and Zn in fresh bovine liver and BCR bovine liver and pig kidney reference materials, after digestion at 105 degrees C with nitric acid for various times, showed that the trace elements were completely released after heating for only 20 min. Centrifugation of the samples after digestion improved the separation from undigested fat. This partial-digestion method, based on heating about 0.2 g of sample with 2 ml of nitric acid for 20 min, was tested on a range of biological reference materials and on fresh bovine liver for the four elements. Comparison was made with results obtained after digestion by a recommended hydrogen peroxide--sulfuric acid digestion procedure. Results obtained by inductively coupled plasma atomic emission spectrometry or by flame and graphite-furnace atomic absorption spectrometry showed good agreement between the two digestion procedures, and results for the reference materials agreed well with the certified values. Between-batch precision was better than 4% for Cu, Fe and Zn at levels of 30 to 190, 210 to 320 and 100 to 140 micrograms g-1, respectively. For Mn, the precision varied between 7 and 14% for measured concentrations of 8 to 12 micrograms g-1. The partial-digestion procedure offers simplicity, speed, low cost and the ability to handle a large number of samples at the same time.

Animals↗
PubMed1992

Gold concentrations in blood fractions of patients with rheumatoid arthritis treated with Myocrisin.

Gold levels in the plasma and blood cells of patients treated with the gold drug Myocrisin (sodium aurothiomalate) were determined by atomic absorption spectrometry. There is a correlation between whole blood gold and plasma gold concentrations which is different for smokers and non-smokers. Most cellular gold is associated with the membrane and is present in concentrations approximately equivalent to the number of reactive sulphydryl groups on the exofacial surface of the cell. Since gold would be expected to react with SH groups and since these groups are vital for cellular function, a possible role for gold in modifying cellular metabolism is indicated.

Arthritis, Rheumatoid↗
PubMed1988

Contributions to biological analysis by atomic spectrometry--a summary of the achievements of Professor John Michael Ottaway.

John Ottaway was the Head of the Analytical Chemistry Research Group at the University of Strathclyde for almost 20 years and during that period much of the research performed by the Group was devoted to the development of improved analytical procedures for the determination of trace metals in clinical and biological samples. Although this was only one aspect of the Group's activities in analytical chemistry, a number of significant contributions were made in the clinical field and a summary of Professor Ottaway's achievements is given in this brief review. The techniques covered include electrothermal atomisation atomic absorption spectrometry (ETA-AAS), electrothermal atomisation atomic emission spectrometry (ETA-AES), furnace atomic non-thermal excitation spectrometry (FANES), continuum source atomic absorption spectrometry (CSAAS) and atomic fluorescence spectrometry (AFS).

Bibliographies as Topic↗
PubMed1986

Leukotriene D4 treatment of bovine aortic endothelial cells and murine smooth muscle cells in culture results in an increase in phospholipase A2 activity.

Leukotriene D4 stimulates prostanoid synthesis in smooth muscle and endothelial cells. Because phospholipases A2 and C have been proposed to regulate prostanoid synthesis, we examined the effect of leukotriene D4 on these activities. Leukotriene D4 treatment resulted in a dose-dependent, stereospecific increase in phospholipase A2 activity with phosphatidylcholine as a substrate. The induction of phospholipase A2 activity occurred just prior to the appearance of prostanoids in the media. Protein and RNA synthesis were required for the increase in phospholipase A2 activity, and the increase in activity resulted from an increase in the apparent Vmax of the phospholipase A2 enzyme. Phospholipase C activity using various substrates was unchanged. We conclude that the increase in prostanoid synthesis observed after leukotriene D4 treatment is a result of an increase in a phospholipase A2 activity.

Animals↗
PubMed1986

Effect of leukotrienes, bradykinin and calcium ionophore (A 23187) on bovine endothelial cells: release of prostacyclin.

Incubation of the bovine endothelial cell line, CPAE, with the calcium ionophore (A23187), bradykinin (BK), leukotriene D4 (LTD4) or leukotriene C4 (LTC4) resulted in concentration dependent increases in prostacyclin release measured as 6-keto-prostaglandin F1 alpha. The kinetics of induction of prostacyclin synthesis differed among the agents studied. Statistically significant increases in prostacyclin were observed one minute after treatment, with A23187, at slightly longer times with bradykinin and after approximately three minutes with the leukotrienes. Two other leukotrienes were tested. Both leukotriene B4 and leukotriene E4 (LTE4) were inactive at concentrations up to 10 microM. The induction of prostacyclin synthesis by LTC4 and LTD4 was inhibited by cycloheximide and actinomycin-D. The effect of BK was inhibited by cycloheximide but not by actinomycin-D. Induction by A23187 was not inhibited by either actinomycin-D or cycloheximide. The results suggest that these agents induced the increases in prostacyclin synthesis by different mechanisms.

6-Ketoprostaglandin F1 alpha↗