James Barker

Effect of silicon on gastrointestinal absorption of aluminium.

The reported geographical association between Alzheimers disease and levels of aluminium (Al) in water supplies may reflect the inverse relation between Al and silicon (Si) concentrations in water, and the potential for Si to reduce the bioavailability of the metal. We tested this hypothesis using isotopic 26Al tracer administered orally to five healthy volunteers in the presence and absence of Si. Dissolved Si, at a concentration found in some water supplies (100 mumol/L), reduced the peak plasma 26Al concentration to 15% of the value obtained in the absence of Si. The results indicate that dissolved Si is an important factor in limiting the absorption of dietary Al.

Misleading measures in Vitamin D analysis: a novel LC-MS/MS assay to account for epimers and isobars

BackgroundRecently, the accuracies of many commercially available immunoassays for Vitamin D have been questioned. Liquid chromatography tandem mass spectrometry (LC- MS/MS) has been shown to facilitate accurate separation and quantification of the major circulating metabolite 25-hydroxyvitamin-D3 (25OHD3) and 25-hydroxyvitamin-D2 (25OHD2) collectively termed as 25OHD. However, among other interferents, this method may be compromised by overlapping peaks and identical masses of epimers and isobars, resulting in inaccuracies in circulating 25OHD measurements. The aim of this study was to develop a novel LC-MS/MS method that can accurately identify and quantitate 25OHD3 and 25OHD2 through chromatographic separation of 25OHD from its epimers and isobars.MethodsA positive ion electrospray ionisation (ESI) LC-MS/MS method was used in the Multiple Reaction Monitoring (MRM) mode for quantification. It involved i) liquid-liquid extraction, ii) tandem columns (a high resolution ZORBAX C18 coupled to an ULTRON chiral, with guard column and inlet filter), iii) Stanozolol-D3 as internal standard, and iv) identification via ESI and monitoring of three fragmentation transitions. To demonstrate the practical usefulness of our method, blood samples were collected from 5 healthy male Caucasian volunteers; age range 22 to 37 years and 25OHD2, 25OHD3 along with co-eluting epimers and analogues were quantified.ResultsThe new method allowed chromatographic separation and quantification of 25OHD2, 25OHD3, along with 25OHD3 epimer 3-epi-25OHD3 and isobars 1-α-hydroxyvitamin-D3 (1αOHD3), and 7-α-hydroxy-4-cholesten-3-one (7αC4). The new assay was capable of detecting 0.25 ng/mL of all analytes in serum.ConclusionsTo our knowledge, this is the first specific, reliable, reproducible and robust LC-MS/MS method developed for the accurate detection of 25OHD (Vitamin D). The method is capable of detecting low levels of 25OHD3 and 25OHD2 together with chromatographic separation from the co-eluting epimers and isobars and circumvents other instrumental/analytical interferences. This analytical method does not require time-consuming derivatisation and complex extraction techniques and could prove very useful in clinical studies.

Determination of metal ion content of beverages and estimation of target hazard quotients: a comparative study

This is a correction to the following paper: Hague T, Petroczi A, Andrews PR, Barker J, Naughton DP: Determination of metal ion content of beverages and estimation of target hazard quotients: a comparative study. Chem Central J 2008, 2:13.

Quantitative analysis of mephedrone using liquid chromatography tandem mass spectroscopy: Application to human hair

Recent abuse of designer drugs such as mephedrone has presented a requirement for sensitive, reliable and reproducible methods for the detection of these controlled drugs in different matrices. This study focuses on a fully developed validated method for the quantitative analysis of mephedrone and its two metabolites 4-methylephedrine and 4-methylnorephedrine in human hair. The calibration curve was found to be linear in the range 5-100 pg/mg for mephedrone and 10-150 pg/mg for 4-methylephedrine and 4-methylnorephedrine. The method was successfully validated for the intraday precision, interday precision, limit of detection, accuracy and extraction recovery. Five out of 154 hair samples were confirmed to be positive for mephedrone. Due to the structural similarities to other methcathinones and amphetamines, one can propose the metabolism for mephedrone based on a similar pathway that has been previously used for these psychoactive drugs. The outlined method can be valuable for the future detection of mephedrone and its two metabolites in hair.

Cytotoxicity and bioavailability studies on a decoction of Oldenlandia diffusa and its fractions separated by HPLC

AIM OF THE STUDY Oldenlandia diffusa is a traditional Chinese herbal remedy with known cytotoxic activity in vitro and in vivo. The aim of the study was to identify the most cytotoxic constituents of a water extract (a decoction is traditionally used as a treatment) by HPLC and activity-guided fractionation. The bioavailability of the decoction and certain fractions, and the mode of cell death induced by these mixtures, were also investigated. MATERIALS AND METHODS A decoction of O. diffusa was prepared and separated by HPLC into eleven fractions (F1-11) for testing on the growth of HL60 leukaemia cells; two of the most active fractions were also tested on Caco-2 colon cancer cells. Cell viability was measured by trypan blue exclusion, DNA content (Cyquant NF assay) and neutral red uptake. Evidence of apoptosis was gained from cells stained with the nuclear dye DAPI, and detection of cleaved poly (ADP-ribose) polymerase (PARP) by Western blot. RESULTS Fraction 9 was found to be the most active fraction, and, along with the decoction, induced apoptosis. Cells stained with DAPI showed a decrease in cell size and nuclear fragmentation characteristic of apoptosis. Detection of cleaved PARP further confirmed induction of apoptosis by O. diffusa decoction and fraction 9. The bioavailability of O. diffusa was investigated by production of post-absorption samples using Caco-2 intestinal epithelial monolayers. Addition of post-absorption samples (taken from the basolateral side after 3h incubation with the decoction on the apical side) inhibited the growth of HL60 cells, and suggested a degree of bioavailability. The constituents in fraction 9 were further separated by HPLC and eight major compounds were identified by LC-MS: two of these were ursolic acid (UA) and its enantiomer oleanolic acid (OA). Concentrations of UA and OA in the decoction were then calculated by reference to the area of the peaks of UA and OA found in F9. The post-absorption sample of F9 contained six of the eight constituents in the original pre-absorption fraction 9. CONCLUSIONS Taken together, the results suggest that certain constituents, possibly including ursolic/oleanolic acid, may be bioavailable and at sufficient concentration to induce apoptosis in cancer cells in vitro through a mechanism including the cleavage of PARP.

Ecotoxic pharmaceuticals, personal care products, and other emerging contaminants: A review of environmental, receptor-mediated, developmental, and epigenetic toxicity with discussion of proposed toxicity to humans

ABSTRACT Pharmaceuticals and personal care products (PPCPs), other emerging contaminants (ECs), and metabolites thereof are ubiquitous in the environment, both built and natural. While such compounds have been environmentally present for some time, new pharmaceuticals and replacements for other ECs phased out due to regulatory limitations are continually being introduced to market. Non-target lower organisms are exposed through affected water, atmospheric emissions, precipitation, sediments, among other routes. Biological disruption/dysfunction (such as endocrine, developmental, and epigenetic disruption) has been reported in lower organisms exposed to trace levels of PPCPs and other ECs. Such disruption/dysfunction may not be exclusively present as traditional toxic response (e.g., cancer or death) but may only slightly alter natural biological processes as a result of exposure to an exogenous chemical (e.g., an increased heart rate or altered size of dorsal fat pads in fish). The epigenome and endocrine system appear to be relatively sensitive to many PPCPs/ECs, particularly during early development. Humans are exposed to ECs such as plasticizers and perfluorinated compounds (PFCs) mainly through ingestion (food and contaminated liquid) as well as interaction with day-to-day products (detergents, musk compounds in fragrances, etc.). Few, if any, studies have investigated trace-level toxicity of such ECs to humans as direct-exposure trials are highly unethical. However, numerous epidemiological links exist between the presence of contaminants in humans (blood, urine, and tissues) and the occurrence of diseases or other phenotypic alterations. Despite mounting interest and research, such trace-level effects on humans are greatly debated and often criticized. This paper reviews the current understanding of PPCP/EC toxicity. Discussion of general biological disruption/dysfunction of the following seven classes of PPCP/ECs is included: analgesics, antibiotics, antineoplastic compounds, beta-blockers, endocrine disrupting compounds, PFCs, and plasticizers. A review of receptor-mediated toxicity, non-monotonic dose response relationships, developmental toxicity, and environmental epigenetics is also included. Lastly, an overview of the proposed toxicity to humans is provided including discussion of significant criticism and direction of future research.

Plants as biomarkers for monitoring heavy metal contaminants on landfill sites using sequential extraction and inductively coupled plasma atomic emission spectrophotometry (ICP-AES).

There have been a number of studies investigating metal uptake in plants on contaminated landfill sites, but little on their role as biomarkers to identify metal mobility for continuous monitoring purposes. Vegetation can be used as a biomonitor of site pollution, by identifying the mobilisation of heavy metals and by providing an understanding of their bioavailability. Plants selected were the common nettle (Uritica Dioica), bramble (Rubus Fruticosa) and sycamore (Acer Pseudoplatanus). A study of the soil fractionation was made to investigate the soil properties that are likely to influence metal mobility and a correlation exercise was undertaken to investigate if variations in concentration of metals in vegetation can reflect variations in concentration of the metals in soil. The soil was digested using aqua regia in a microwave closed vessel. The vegetation was digested using both microwave and a hydrogen peroxide-nitric acid mixture, refluxed on a heating block and a comparison made. The certified reference materials (CRMs) used were Standard Reference Material (SRM) 1547, peach leaves for vegetation (NIST) and for soil CRM 143R, sewage sludge-amended soil (BCR). The relative standard deviations (RSDs) were 2-6% for the analyses. Our findings show evidence of phytoextraction by some plants, (especially bramble and nettle), with certain plants, (sycamore) exhibiting signs of phytostabilisation. The evidence suggests that there is a degree of selectivity in metal uptake and partitioning within the plant compartments. It was also possible to correlate mobility phases of certain metals (Pb, Cu and Zn) using the soil and plant record. Zn and Cu exhibited the greatest potential to migrate from the roots to the leaves, with Pb found principally in the roots of ground vegetation. Our results suggest that analysis of bramble leaves, nettle leaves and roots can be used to monitor the mobility of Pb in the soil with nettle, bramble and sycamore leaves to monitor Cu and Zn.

Incongruence in Doping Related Attitudes, Beliefs and Opinions in the Context of Discordant Behavioural Data: In Which Measure Do We Trust?

Background Social psychology research on doping and outcome based evaluation of primary anti-doping prevention and intervention programmes have been dominated by self-reports. Having confidence in the validity and reliability of such data is vital. Methodology/Principal Findings The sample of 82 athletes from 30 sports (52.4% female, mean age: 21.48±2.86 years) was split into quasi-experimental groups based on i) self-admitted previous experience with prohibited performance enhancing drugs (PED) and ii) the presence of at least one prohibited PED in hair covering up to 6 months prior to data collection. Participants responded to questionnaires assessing a range of social cognitive determinants of doping via self-reports; and completed a modified version of the Brief Implicit Association Test (BIAT) assessing implicit attitudes to doping relative to the acceptable nutritional supplements (NS). Social projection regarding NS was used as control. PEDs were detected in hair samples from 10 athletes (12% prevalence), none of whom admitted doping use. This group of ‘deniers’ was characterised by a dissociation between explicit (verbal declarations) and implicit (BIAT) responding, while convergence was observed in the ‘clean’ athlete group. This dissociation, if replicated, may act as a cognitive marker of the denier group, with promising applications of the combined explicit-implicit cognitive protocol as a proxy in lieu of biochemical detection methods in social science research. Overall, discrepancies in the relationship between declared doping-related opinion and implicit doping attitudes were observed between the groups, with control measures remaining unaffected. Questionnaire responses showed a pattern consistent with self-reported doping use. Conclusions/Significance Following our preliminary work, this study provides further evidence that both self-reports on behaviour and social cognitive measures could be affected by some form of response bias. This can question the validity of self-reports, with reliability remaining unaffected. Triangulation of various assessment methods is recommended.

Detection of testosterone and epitestosterone in human hair using liquid chromatography–tandem mass spectrometry

The feasibility of using hair analysis as a complimentary test in doping control has received increased attention in the scientific community. The aim of the study was to take a step forward to this goal and develop a method that, for the first time, is able to detect testosterone (T) and epitestosterone (E) in human hair, using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and alkali digestion followed by extraction using pentane. The method was linear within the quantification range of 0.25-100 pg/mg for T and 0.5-100 pg/mg for E, with determination coefficient (r²) values >0.9987. The limits of detection for T and E were 0.1 pg/mg and 0.25 pg/mg respectively. The accuracy, precision and extraction recovery of the assay were satisfactory for the detection of T and E when ca. 50 mg hair was processed. The validated method was successfully applied for the analysis of 75 hair samples collected from healthy volunteers (65.3% males), with the concentration of T between 0.7-11.81 pg/mg and 0.33-6.05 pg/mg and the concentration of E between 0.63-8.27 pg/mg and 0.52-3.88 pg/mg in males and in females respectively. In males, the T levels were significantly higher (p=0.020) but there was no difference in the E levels (p=0.359). However, E was not detectable in 34 samples (of which 19 were females). The T and E levels showed linear correlation (r=0.698, p<0.001) with average T/E ratio of 1.32±0.7. The newly developed analytical method was rapid, facile, sensitive, selective, reproducible and reliable for determining the levels of T and E in hair and thus for calculating the T/E ratio in hair.

Development of26Al accelerator mass spectrometry for biological and toxicological applications

Abstract We report the use of a 20 MV tandem Van de Graaff accelerator to conduct 26Al mass spectrometry with fully stripped aluminium ions, and the development of an ion source preparation for the measurement of 26Al:27Al ratios in biological materials. Discrimination of 26Al from 26Mg is better than 1:109. 26Al calibration is linear with an estimated detection limit ∼10−18 g and limiting 26Al:27Al ratio ∼10−13. Preliminary biological applications include identification of Al carrier proteins in blood, and investigations of Al uptake by cells in culture and Al speciation in natural waters.