David A Barrett

University of Nottingham, Nottigham, England, United Kingdom

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Publications (183)767.98 Total impact

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    ABSTRACT: There has been increased interest in the medical use of cannabinoids in recent years, particularly in the predominant natural cannabinoids, cannabidiol (CBD) and Δ(9)-tetrahydrocannabinol (THC). The aim of the current study was to develop a sensitive and reliable method for the quantification of CBD and THC in rat plasma. A combination of protein precipitation using cold acetonitrile and liquid-liquid extraction using n-hexane was utilised to extract CBD and THC from rat plasma. Samples were then evaporated and reconstituted in acetonitrile and 30μL was injected into an HPLC system. Separation was achieved using an ACE C18-PFP 150mm×4.6mm, 3μm column at 55°C with isocratic elution using a mobile phase consisting of acetonitrile-water (62:38, v/v) at 1mL/min for 20min. Both cannabinoids, as well as the internal standard (4,4-dichlorodiphenyltrichloroethane, DDT) were detected at 220nm. Our new method showed linearity in the range of 10-10,000ng/mL and a lower limit of quantification (LLOQ) of 10ng/mL for both cannabinoids, which is comparable to previously reported LC-MS/MS methods. Inter- and intra-day precision and accuracy were below 15% RSD and RE, respectively. To demonstrate the suitability of the method for in vivo studies in rats, the assay was applied to a preliminary pharmacokinetic study following IV bolus administration of 5mg/kg CBD or THC. In conclusion, a simple, sensitive, and cost-efficient HPLC-UV method for the simultaneous determination of CBD and THC has been successfully developed, validated and applied to a pharmacokinetic study in rats. Copyright © 2015 Elsevier B.V. All rights reserved.
    Journal of pharmaceutical and biomedical analysis 10/2015; 114. DOI:10.1016/j.jpba.2015.05.019 · 2.83 Impact Factor
  • MS Frontiers 2015, London, United Kingdom; 06/2015
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    ABSTRACT: A scalable and cost-effective synthetic polymer substrate that supports robust expansion and subsequent multilineage differentiation of human pluripotent stem cells (hPSCs) with defined commercial media is presented. This substrate can be applied to common cultureware and used off-the-shelf after long-term storage. Expansion and differentiation of hPSCs are performed entirely on the polymeric surface, enabling the clinical potential of hPSC-derived cells to be realized. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    Advanced Materials 06/2015; DOI:10.1002/adma.201501351 · 17.49 Impact Factor
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    ABSTRACT: Pseudomonas aeruginosa produces quorum sensing signal molecules that are potential biomarkers for infection. A prospective study of 60 cystic fibrosis patients with chronic P. aeruginosa, who required intravenous antibiotics for pulmonary exacerbations, was undertaken. Clinical measurements and biological samples were obtained at the start and end of the treatment period. Additional data were available for 29 of these patients when they were clinically stable. Cross-sectionally, quorum sensing signal molecules were detectable in the sputum, plasma and urine of 86%, 75% and 83% patients, respectively. They were positively correlated between the three biofluids. Positive correlations were observed for most quorum sensing signal molecules in sputum, plasma and urine, with quantitative measures of pulmonary P. aeruginosa load at the start of a pulmonary exacerbation. Plasma concentrations of 2-nonyl-4-hydroxy-quinoline (NHQ) were significantly higher at the start of a pulmonary exacerbation compared to clinical stability (p<0.01). Following the administration of systemic antibiotics, plasma 2-heptyl-4-hydroxyquinoline (p=0.02) and NHQ concentrations (p<0.01) decreased significantly. In conclusion, quorum sensing signal molecules are detectable in cystic fibrosis patients with pulmonary P. aeruginosa infection and are positively correlated with quantitative measures of P. aeruginosa. NHQ correlates with clinical status and has potential as a novel biomarker for P. aeruginosa infection. Copyright ©ERS 2015.
    European Respiratory Journal 05/2015; DOI:10.1183/09031936.00225214 · 7.13 Impact Factor
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    ABSTRACT: There is a clinical need for reliable biomarkers for lung cancer that permit early diagnosis of the disease and provide prediction of histological phenotype. A prospective study design was used with a study population of patients with suspected lung cancer. Blood samples were collected from 17 patients with histologically confirmed squamous cell lung carcinoma, 17 individuals with adenocarcinoma, and 17 control individuals who did not subsequently have a diagnosis of lung cancer or any other cancer. Blood plasma samples were analysed for their lipid profiles using liquid chromatography coupled with high resolution mass spectrometry. Data were analysed using multivariate statistical methods. There was good separation between histological subtypes and control groups and also between individuals with a subsequent diagnosis of adenocarcinoma and squamous cell carcinoma (sensitivity 80 %, specificity 83 %, Q2 = 0.70). Alterations in the levels of different classes of lipids including triglycerides (TGs), phosphatidylinositols (PIs), phosphatidylcholines (PCs), phosphatidylethanolamines (PEs), free fatty acids, lysophospholipids and sphingolipids were observed in squamous carcinoma and adenocarcinoma lung cancer patients when compared with control patients. In conclusion, this study has identified candidate lipid biomarkers of non-small cell lung cancer patients which may be helpful to indicate the tumour subtype and to differentiate them from patients who do not have lung cancer. Measuring these biomarkers has the potential to improve diagnosis in patients with suspected lung cancer and risk stratification in screening.
    Metabolomics 05/2015; DOI:10.1007/s11306-015-0811-x · 3.97 Impact Factor
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    ABSTRACT: We present the application of a novel ambient LESA-MS method for the authentication of processed meat products. A set of 25 species and protein-specific heat stable peptide markers has been detected in processed samples manufactured from beef, pork, horse, chicken and turkey meat. We demonstrate that several peptides derived from myofibrillar and sarcoplasmic proteins are sufficiently resistant to processing to serve as specific markers of processed products. The LESA-MS technique required minimal sample preparation without fractionation and enabled the unambiguous and simultaneous identification of skeletal muscle proteins and peptides as well as other components of animal origin, including the milk protein such as casein alpha-S1, in whole meat product digests. We have identified, for the first time, six fast type II and five slow/cardiac type I MHC peptide markers in various processed meat products. The study demonstrates that complex mixtures of processed proteins/peptides can be examined effectively using this approach. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Food Chemistry 04/2015; 187:297-304. DOI:10.1016/j.foodchem.2015.04.078 · 3.39 Impact Factor
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    ABSTRACT: Materials discovery provides the opportunity to identify novel materials that are tailored to complex biological environments by using combinatorial mixing of monomers to form large libraries of polymers as micro arrays. The materials discovery approach is predicated on the use of the largest chemical diversity possible, yet previous studies into human pluripotent stem cell (hPSC) response to polymer microarrays have been limited to 20 or so different monomer identities in each study. Here we show that it is possible to print and assess cell adhesion of 141 different monomers in a microarray format. This provides access to the largest chemical space to date, allowing us to meet the regenerative medicine challenge to provide scalable synthetic culture ware. This study identifies new materials suitable for hPSC expansion that could not have been predicted from previous knowledge of cell-material interactions.
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    ABSTRACT: Aim. We examined endocannabinoids (ECs) in relation to bariatric surgery and the association between plasma ECs and markers of insulin resistance. Methods. A study of 20 participants undergoing bariatric surgery. Fasting and 2-hour plasma glucose, lipids, insulin, and C-peptide were recorded preoperatively and 6 months postoperatively with plasma ECs (AEA, 2-AG) and endocannabinoid-related lipids (PEA, OEA). Results. Gender-specific analysis showed differences in AEA, OEA, and PEA preoperatively with reductions in AEA and PEA in females postoperatively. Preoperatively, AEA was correlated with 2-hour glucose (, ), HOMA-IR (, ), and HOMA %S (, ). OEA was correlated with weight (, ), waist circumference (, ), fasting insulin (, ), and HOMA-IR (, ). PEA was correlated with fasting insulin (, ). 2-AG had a negative correlation with fasting glucose (, ). Conclusion. Gender differences exist in circulating ECs in obese subjects. Females show changes in AEA and PEA after bariatric surgery. Specific correlations exist between different ECs and markers of obesity and insulin and glucose homeostasis.
    Journal of Diabetes Research 03/2015; 2015. DOI:10.1155/2015/680867 · 3.54 Impact Factor
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    ABSTRACT: Activation of the PERK branch of the unfolded protein response (UPR) in response to protein misfolding within the endoplasmic reticulum (ER) results in the transient repression of protein synthesis, mediated by the phosphorylation of the alpha subunit of eukaryotic initiation factor 2 (eIF2α). This is part of a wider integrated physiological response to maintain proteostasis in the face of ER stress, the dysregulation of which is increasingly associated with a wide range of diseases, particularly neurodegenerative disorders. In prion-diseased mice, persistently high levels of eIF2α cause sustained translational repression leading to catastrophic reduction of critical proteins, resulting in synaptic failure and neuronal loss. We previously showed that restoration of global protein synthesis using the PERK inhibitor GSK2606414 was profoundly neuroprotective, preventing clinical disease in prion-infected mice. However, this occured at the cost of toxicity to secretory tissue, where UPR activation is essential to healthy functioning. Here we show that pharmacological modulation of eIF2α-P-mediated translational inhibition can be achieved to produce neuroprotection without pancreatic toxicity. We found that treatment with the small molecule ISRIB, which restores translation downstream of eIF2α, conferred neuroprotection in prion-diseased mice without adverse effects on the pancreas. Critically, ISRIB treatment resulted in only partial restoration of global translation rates, as compared with the complete restoration of protein synthesis seen with GSK2606414. ISRIB likely provides sufficient rates of protein synthesis for neuronal survival, while allowing some residual protective UPR function in secretory tissue. Thus, fine-tuning the extent of UPR inhibition and subsequent translational de-repression uncouples neuroprotective effects from pancreatic toxicity. The data support the pursuit of this approach to develop new treatments for a range of neurodegenerative disorders that are currently incurable.
    Cell Death & Disease 03/2015; 6(3):e1672. DOI:10.1038/cddis.2015.49 · 5.18 Impact Factor
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    ABSTRACT: This work illustrates reactive desorption electrospray ionization mass spectrometry (DESI-MS) with a stable dication on biological tissues. Rat brain and zebra fish tissues were investigated with reactive DESI-MS in which the dictation forms a stable bond with biological tissue fatty acids and lipids. Tandem mass spectrometry (MS/MS) was used to characterize the dication (DC9) and to identify linked lipid-dication compounds formed. The fragment m/z 85 common to both DC9 fragmentation and DC9-lipid fragmentation was used to confirm that DC9 is indeed bonded with the lipids. Lipid signals in the range of m/z 250-350 and phosphoethanolamines (PE) m/z 700-800 observed in negative ion mode were also detected in positive ion mode with reactive DESI-MS with enhanced signal intensity. Reactive DESI-MS imaging in positive ion mode of rat brain and zebra fish tissues allowed enhanced detection of compounds commonly observed in the negative ion mode.
    Analytical Chemistry 02/2015; 87(6). DOI:10.1021/ac5042445 · 5.83 Impact Factor
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    Charles J. P. Snart · Ian C. W. Hardy · David A. Barrett
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    ABSTRACT: Metabolomic analyses can reveal associations between an organism's metabolome and further aspects of its phenotypic state, an attractive prospect for many life-sciences researchers. The metabolomic approach has been employed in some, but not many, insect study systems, starting in 1990 with the evaluation of the metabolic effects of parasitism on moth larvae. Metabolomics has now been applied to a variety of aspects of insect biology, including behaviour, infection, temperature stress responses, CO2 sedation, and bacteria–insect symbiosis. From a technical and reporting standpoint, these studies have adopted a range of approaches utilising established experimental methodologies. Here, we review current literature and evaluate the metabolomic approaches typically utilised by entomologists. We suggest that improvements can be made in several areas, including sampling procedures, the reduction in sampling and equipment variation, the use of sample extracts, statistical analyses, confirmation, and metabolite identification. Overall, it is clear that metabolomics can identify correlations between phenotypic states and underlying cellular metabolism that previous, more targeted, approaches are incapable of measuring. The unique combination of untargeted global analyses with high-resolution quantitative analyses results in a tool with great potential for future entomological investigations.
    Entomologia Experimentalis et Applicata 02/2015; 155(1). DOI:10.1111/eea.12281 · 1.71 Impact Factor
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    ABSTRACT: Catheter - associated urinary tract infection (CAUTI) is the commonest hospital - acquired infection, accounting for over 100,000 hospital admissions within the USA annually. Biomaterials and processes intended to reduce the risk of bacterial colonization of the catheters for long-term users have not been successful, mainly because of the need for long duration of activity in flow conditions. Here we report the results of impregnation of urinary catheters with a combination of rifampicin, sparfloxacin and triclosan. In flow experiments, the antimicrobial catheters were able to prevent colonization by common uropathogens Proteus mirabilis, Staphylococcus aureus and Escherichia coli for 7 to 12weeks in vitro compared with 1-3 days for other, commercially available antimicrobial catheters currently used clinically. Resistance development was minimized by careful choice of antimicrobial combinations. Drug release profiles and distribution in the polymer, and surface analysis were also carried out and the process had no deleterious effect on the mechanical performance of the catheter or its balloon. The antimicrobial catheter therefore offers for the first time a means of reducing infection and its complications in long-term urinary catheter users. Copyright © 2015. Published by Elsevier B.V.
    Journal of Controlled Release 01/2015; DOI:10.1016/j.jconrel.2015.01.037 · 7.26 Impact Factor
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    ABSTRACT: Reductions in plasma endocannabinoids following bariatric surgery in morbidly obese females with impaired glucose homeostasis: A non-randomized prospective study • Endocannabinoids (ECs) are bioactive lipid mediators − N-arachidonyl ethanolamine (AEA) − N-palmitoyl ethanolamine (PEA) − N-oleoyl ethanolamine (OEA) − related N-acylethanolamine (NAE) derivatives − 2-arachidonyl glycerol (2-AG) • Endocannabinoid system (ECS) plays a critical role in regulation of body weight and may have a role in aetiopathogenesis of Type 2 Diabetes (T2DM) • Elevated circulating levels of AEA and 2-AG in obese people compared to non-obese controls of both genders • Little information available on the effects of extreme weight loss associated with bariatric surgery in relation to the ECS
    British Obesity and Metabolic Surgery Society; 01/2015
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    ABSTRACT: Materials discovery provides the opportunity to identify novel materials that are tailored to complex biological environments by using combinatorial mixing of monomers to form large libraries of polymers as micro arrays. The materials discovery approach is predicated on the use of the largest chemical diversity possible, yet previous studies into human pluripotent stem cell (hPSC) response to polymer microarrays have been limited to 20 or so different monomer identities in each study. Here we show that it is possible to print and assess cell adhesion of 141 different monomers in a microarray format. This provides access to the largest chemical space to date, allowing us to meet the regenerative medicine challenge to provide scalable synthetic culture ware. This study identifies new materials suitable for hPSC expansion that could not have been predicted from previous knowledge of cell-material interactions.
    11/2014; 2(11):1604-1611. DOI:10.1039/c4bm00054d
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    ABSTRACT: Triterpene saponins are important bioactive constituents widely distributed in many plants. Saponins present in Caulophyllum (Berberidaceae) have not been fully characterized. In this study, we studied triterpene saponins from Caulophyllum robustum using liquid chromatography combined with electrospray ionization quadrupole time-of-flight mass spectrometry (LC-qTOF-MS). Rapid identification of Caulophyllum saponins was facilitated using low and high MS cone voltages to induce controlled fragmentation in positive mode. The full scan spectra at low cone voltage of 40V provided considerable structural information relating to aglycone skeletons, sugar types, and linked sequences for Caulophyllum saponins. Seven Caulophyllum aglycones were differentiated and identified by their diagnostic fragment ions combined with accurate mass measurements and characteristic fragmentation pathways. Peak intensity ratio of [aglycone+H-2H2O](+) to [aglycone+H-H2O](+) in full scan spectra acquired with low cone voltage is correlated with structural features of hederagenin and echinocystic acid and is useful for the discrimination of these positional isomers. However, at a high voltage of 200V, the saponin [M+H](+) ion and its fragmentation ions were not present; and the single saponin [M+Na](+) generated [Bα+Na](+) and [Y0α+Na](+) by in-source fragmentation, which provided structural information on the α- and β-sugar chains in the saponins. This approach enabled simultaneous acquisition of structural information on both aglycones and sugar chains from full scan spectra in one injection. Based on the developed strategy, 51 triterpene saponins of seven different classes were fully characterized or tentatively identified, of which 32 constituents were the first to be reported in genus Caulophyllum and 18 compounds were characterized as potentially new compounds.
    Journal of Pharmaceutical and Biomedical Analysis 11/2014; 100:109–122. DOI:10.1016/j.jpba.2014.07.024 · 2.83 Impact Factor
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    ABSTRACT: Cells respond to external stress conditions by controlling gene expression, a process which occurs rapidly via post-transcriptional regulation at the level of protein synthesis. Global control of translation is mediated by modification of translation factors to allow reprogramming of the translatome and synthesis of specific proteins that are required for stress protection or initiation of apoptosis. Herein we have investigated how global protein synthesis rates are regulated upon mild cooling. We demonstrate that although there are changes to the factors that control initiation, including phosphorylation of eIF2 on the alpha subunit, the reduction in the global translation rate is mediated by regulation of elongation via phosphorylation of eEF2 by its specific kinase, eEF2K. The AMP:ATP ratio increases following cooling, consistent with a reduction in metabolic rates, giving rise to activation of AMPK, which is upstream of eEF2K. However, our data show that the major trigger for activation of eEF2K upon mild cooling is the release of calcium ions from the endoplasmic reticulum and, importantly, that it is possible to restore protein synthesis rates in cooled cells by inhibition of this pathway at multiple points. As cooling has both therapeutic and industrial applications, our data provide important new insights into how the cellular responses to this stress are regulated, opening up new possibilities to modulate these responses for medical or industrial use at physiological or cooler temperatures.
    Biochemical Journal 10/2014; DOI:10.1042/BJ20141014 · 4.78 Impact Factor
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    ABSTRACT: In this paper, our previously developed ambient LESA-MS methodology is implemented to analyze five types of thermally treated meat species, namely beef, pork, horse, chicken, and turkey meat, in order to select and identify heat-stable and species-specific peptide markers. In-solution tryptic digests of cooked meats were deposited onto a polymer surface, followed by LESA-MS analysis and evaluation using multivariate data analysis and tandem electrospray MS. The five types of cooked meat were clearly discriminated using principal component analysis and orthogonal partial least squares discriminant analysis. A number of 23 heat stable peptide markers unique to species and muscle protein were identified following data-dependent tandem LESA-MS analysis. Surface extraction and direct ambient MS analysis of mixtures of cooked meat species was performed for the first time and enabled detection of 10% (w/w) of pork, horse, and turkey meat, and 5% (w/w) of chicken meat in beef, using the developed LESA-MS/MS analysis. The study shows, for the first time, that ambient LESA-MS methodology displays specificity sufficient to be implemented effectively for the analysis of processed and complex peptide digests. The proposed approach is much faster and simpler than other measurement tools for meat speciation; it has potential for application in other areas of meat science or food production.
    Analytical Chemistry 09/2014; 86(20):10257-10265. DOI:10.1021/ac502449w · 5.83 Impact Factor
  • APS UK PharmSci 2014; 09/2014
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    ABSTRACT: Polycystic ovary syndrome (PCOS) is a common disorder affecting between 5 and 18 % of females of reproductive age and can be diagnosed based on a combination of clinical, ultrasound and biochemical features, none of which on its own is diagnostic. A lipidomic approach using liquid chromatography coupled with accurate mass high-resolution mass-spectrometry (LC-HRMS) was used to investigate if there were any differences in plasma lipidomic profiles in women with PCOS compared with control women at different stages of menstrual cycle. Plasma samples from 40 women with PCOS and 40 controls aged between 18 and 40 years were analysed in combination with multivariate statistical analyses. Multivariate data analysis (LASSO regression and OPLS-DA) of the sample lipidomics datasets showed a weak prediction model for PCOS versus control samples from the follicular and mid-cycle phases of the menstrual cycle, but a stronger model (specificity 85 % and sensitivity 95 %) for PCOS versus the luteal phase menstrual cycle controls. The PCOS vs luteal phase model showed increased levels of plasma triglycerides and sphingomyelins and decreased levels of lysophosphatidylcholines and phosphatidylethanolamines in PCOS women compared with controls. Lipid biomarkers of PCOS were tentatively identified which may be useful in distinguishing PCOS from controls especially when performed during the menstrual cycle luteal phase.
    Metabolomics 08/2014; 11(3). DOI:10.1007/s11306-014-0726-y · 3.97 Impact Factor
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    ABSTRACT: Statins are lipid-lowering drugs widely used for prevention and treatment of cardiovascular and coronary heart diseases. These drugs are among the most commonly prescribed medicines intended for long term use. Statins are generally well tolerated. However, muscular adverse effects appear to be the most common obstacle that limits their use, resulting in poor patient compliance or even drug discontinuation. In addition, rare but potentially fatal cases of rhabdomyolysis have been reported with the use of these drugs, especially in the presence of certain risk factors. Previous reports have investigated statin-induced myotoxicity in vivo and in vitro using a number of cell lines, muscle tissues and laboratory animals, in addition to randomized clinical trials, observational studies and case reports. None of them have directly compared results from laboratory investigations with clinical observations of statin related muscular adverse effects. To the best of our knowledge this is the first review article that combines laboratory investigation with clinical aspects of statin-induced myotoxicity. By reviewing published literature of in vivo, in vitro and clinically relevant studies of statin myotoxicity, we aim at translating this important drug related problem in order to establish a clear picture of proposed mechanisms, to explain the risk factors and describe the diagnostic approaches currently employed for evaluating the degree of muscle damage induced by these agents. This review provides a baseline novel translational insight that can be used to enhance safety profile, minimize the chance of progression of these adverse effects to more severe and potentially fatal rhabdomyolysis and improve the overall patient compliance and adherence to long-term statin therapy.
    08/2014; 164(2). DOI:10.1016/j.trsl.2014.01.013

Publication Stats

3k Citations
767.98 Total Impact Points

Institutions

  • 1991–2015
    • University of Nottingham
      • • School of Pharmacy
      • • School of Medicine
      Nottigham, England, United Kingdom
  • 2009
    • Queen Mary, University of London
      • School of Biological and Chemical Sciences
      Londinium, England, United Kingdom
  • 2008
    • University of Birmingham
      • School of Biosciences
      Birmingham, England, United Kingdom