189 results on '"Fletcher AM"'
Search Results
52. Diastereoselective Ireland-Claisen rearrangements of substituted allyl β-amino esters: applications in the asymmetric synthesis of C(5)-substituted transpentacins.
- Author
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Davies SG, Fletcher AM, Lee JA, Roberts PM, Souleymanou MY, Thomson JE, and Zammit CM
- Abstract
The diastereoselective Ireland-Claisen rearrangement of a range of substituted allyl β-amino esters gave the corresponding enantiopure α-substituted-β-amino esters with good diastereoselectivity. The application of this methodology in the asymmetric synthesis of a range of C(5)-substituted 1,2-anti-1,5-syn-transpentacins was demonstrated by the rearrangement of a range of β-amino esters derived from sorbic acid, followed by esterification, ring-closing metathesis, hydrogenolytic deprotection/reduction, and hydrolysis, which gave the C(5)-substituted transpentacins in only 9 steps from commercially available starting materials.
- Published
- 2014
- Full Text
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53. Occurrence of spontaneous pancreatic lesions in normal and diabetic rats: a potential confounding factor in the nonclinical assessment of GLP-1-based therapies.
- Author
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Chadwick KD, Fletcher AM, Parrula MC, Bonner-Weir S, Mangipudy RS, Janovitz E, Graziano MJ, Roy D, and Reilly TP
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- Animals, Diabetes Mellitus physiopathology, Diet, High-Fat, Dipeptidyl-Peptidase IV Inhibitors therapeutic use, Incretins adverse effects, Pancreas pathology, Pancreatitis etiology, Rats, Rats, Sprague-Dawley, Rats, Zucker, Weight Gain, Glucagon-Like Peptide 1 agonists, Glucagon-Like Peptide 1 therapeutic use, Pancreas drug effects, Pancreatic Diseases etiology
- Abstract
Glucagon-like peptide 1-based therapies, collectively described as incretins, produce glycemic benefits in the treatment of type 2 diabetes. Recent publications raised concern for a potential increased risk of pancreatitis and pancreatic cancer with incretins based in part on findings from a small number of rodents. However, extensive toxicology assessments in a substantial number of animals dosed up to 2 years at high multiples of human exposure do not support these concerns. We hypothesized that the lesions being attributed to incretins are commonly observed background findings and endeavored to characterize the incidence of spontaneous pancreatic lesions in three rat strains (Sprague-Dawley [S-D] rats, Zucker diabetic fatty [ZDF] rats, and rats expressing human islet amyloid polypeptide [HIP]; n = 36/group) on a normal or high-fat diet over 4 months. Pancreatic findings in all groups included focal exocrine degeneration, atrophy, inflammation, ductular cell proliferation, and/or observations in large pancreatic ducts similar to those described in the literature, with an incidence of exocrine atrophy/inflammation seen in S-D (42-72%), HIP (39%), and ZDF (6%) rats. These data indicate that the pancreatic findings attributed to incretins are common background findings, observed without drug treatment and independent of diet or glycemic status, suggesting a need to exercise caution when interpreting the relevance of some recent reports regarding human safety.
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- 2014
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54. (-)-(2S,3R,Z)-Nakinadine A: first asymmetric synthesis and absolute configuration assignment.
- Author
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Davies SG, Fletcher AM, Roberts PM, Shah RS, Thompson AL, and Thomson JE
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- Alkaloids chemistry, Animals, Molecular Structure, Nuclear Magnetic Resonance, Biomolecular, Porifera chemistry, Pyridines chemistry, Stereoisomerism, Alkaloids chemical synthesis, Pyridines chemical synthesis
- Abstract
Mannich-type reaction of methyl phenylacetate with the N-tert-butylsulfinyl imine derived from (R)-tert-butylsulfinamide and (Z)-14-(pyridin-3'-yl)tetradec-11-enal has been used as the key step in the first asymmetric synthesis of (-)-nakinadine A. Both the 2,3-syn- and 2,3-anti-diastereoisomers were prepared; comparison of spectroscopic and specific rotation data facilitated assignment of the absolute (2S,3R,Z)-configuration within the natural product. (-)-(2S,3R,Z)-Nakinadine A was prepared in 10 steps from 11-bromoundecan-1-ol, in 10% overall yield, 97:3 dr [(Z):(E) ratio], and >98% ee.
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- 2014
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55. 18F-fluoride positron emission tomography for identification of ruptured and high-risk coronary atherosclerotic plaques: a prospective clinical trial.
- Author
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Joshi NV, Vesey AT, Williams MC, Shah AS, Calvert PA, Craighead FH, Yeoh SE, Wallace W, Salter D, Fletcher AM, van Beek EJ, Flapan AD, Uren NG, Behan MW, Cruden NL, Mills NL, Fox KA, Rudd JH, Dweck MR, and Newby DE
- Subjects
- Aged, Angina Pectoris metabolism, Carotid Stenosis diagnosis, Carotid Stenosis metabolism, Confounding Factors, Epidemiologic, Coronary Artery Disease diagnosis, Female, Humans, Male, Middle Aged, Myocardial Infarction metabolism, Plaque, Atherosclerotic diagnosis, Prospective Studies, Risk Factors, Rupture, Spontaneous, Scotland, Sodium Fluoride metabolism, Coronary Angiography, Coronary Artery Disease metabolism, Fluorodeoxyglucose F18 metabolism, Plaque, Atherosclerotic metabolism, Positron-Emission Tomography methods, Radiopharmaceuticals metabolism, Tomography, X-Ray Computed
- Abstract
Background: The use of non-invasive imaging to identify ruptured or high-risk coronary atherosclerotic plaques would represent a major clinical advance for prevention and treatment of coronary artery disease. We used combined PET and CT to identify ruptured and high-risk atherosclerotic plaques using the radioactive tracers (18)F-sodium fluoride ((18)F-NaF) and (18)F-fluorodeoxyglucose ((18)F-FDG)., Methods: In this prospective clinical trial, patients with myocardial infarction (n=40) and stable angina (n=40) underwent (18)F-NaF and (18)F-FDG PET-CT, and invasive coronary angiography. (18)F-NaF uptake was compared with histology in carotid endarterectomy specimens from patients with symptomatic carotid disease, and with intravascular ultrasound in patients with stable angina. The primary endpoint was the comparison of (18)F-fluoride tissue-to-background ratios of culprit and non-culprit coronary plaques of patients with acute myocardial infarction., Findings: In 37 (93%) patients with myocardial infarction, the highest coronary (18)F-NaF uptake was seen in the culprit plaque (median maximum tissue-to-background ratio: culprit 1·66 [IQR 1·40-2·25] vs highest non-culprit 1·24 [1·06-1·38], p<0·0001). By contrast, coronary (18)F-FDG uptake was commonly obscured by myocardial uptake and where discernible, there were no differences between culprit and non-culprit plaques (1·71 [1·40-2·13] vs 1·58 [1·28-2·01], p=0·34). Marked (18)F-NaF uptake occurred at the site of all carotid plaque ruptures and was associated with histological evidence of active calcification, macrophage infiltration, apoptosis, and necrosis. 18 (45%) patients with stable angina had plaques with focal (18)F-NaF uptake (maximum tissue-to-background ratio 1·90 [IQR 1·61-2·17]) that were associated with more high-risk features on intravascular ultrasound than those without uptake: positive remodelling (remodelling index 1·12 [1·09-1·19] vs 1·01 [0·94-1·06]; p=0·0004), microcalcification (73% vs 21%, p=0·002), and necrotic core (25% [21-29] vs 18% [14-22], p=0·001)., Interpretation: (18)F-NaF PET-CT is the first non-invasive imaging method to identify and localise ruptured and high-risk coronary plaque. Future studies are needed to establish whether this method can improve the management and treatment of patients with coronary artery disease., Funding: Chief Scientist Office Scotland and British Heart Foundation., (Copyright © 2014 Joshi et al. Open Access article distributed under the terms of CC BY. Published by Elsevier Ltd. All rights reserved.)
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- 2014
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56. Reply: The alveolar macrophage and acute respiratory distress syndrome: a silent actor?
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Barr LC, Brittan M, Morris AC, McAuley DF, McCormack C, Fletcher AM, Richardson H, Connell M, Patel D, Wallace WA, Rossi AG, Davidson DJ, Manson L, Turner M, Hirani N, Walsh TS, Anderson NH, Dhaliwal K, and Simpson AJ
- Subjects
- Humans, Male, Inflammation Mediators physiology, Leukapheresis
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- 2014
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57. Long distance directional growth of dopaminergic axons along pathways of netrin-1 and GDNF.
- Author
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Zhang C, Jin Y, Ziemba KS, Fletcher AM, Ghosh B, Truit E, Yurek DM, and Smith GM
- Subjects
- Animals, Blotting, Western, Female, Humans, Immunohistochemistry, Mesencephalon transplantation, Mice, Netrin-1, Rats, Rats, Sprague-Dawley, Transfection, Axons physiology, Brain Tissue Transplantation methods, Dopaminergic Neurons transplantation, Glial Cell Line-Derived Neurotrophic Factor metabolism, Nerve Growth Factors metabolism, Tumor Suppressor Proteins metabolism
- Abstract
Different experimental and clinical strategies have been used to promote survival of transplanted embryonic ventral mesencephalic (VM) neurons. However, few studies have focused on the long-distance growth of dopaminergic axons from VM transplants. The aim of this study is to identify some of the growth and guidance factors that support directed long-distance growth of dopaminergic axons from VM transplants. Lentivirus encoding either glial cell line-derived neurotrophic factor (GDNF) or netrin-1, or a combination of lenti-GDNF with either lenti-GDNF family receptor α1 (GFRα-1) or lenti-netrin-1 was injected to form a gradient along the corpus callosum. Two weeks later, a piece of embryonic day 14 VM tissue was transplanted into the corpus callosum adjacent to the low end of the gradient. Results showed that tyrosine hydroxylase (TH(+)) axons grew a very short distance from the VM transplants in control groups, with few axons reaching the midline. In GDNF or netrin-1 expressing groups, more TH(+) axons grew out of transplants and reached the midline. Pathways co-expressing GDNF with either GFRα-1 or netrin-1 showed significantly increased axonal outgrowth. Interestingly, only the GDNF/netrin-1 combination resulted in the majority of axons reaching the distal target (80%), whereas along the GDNF/GFRα-1 pathway only 20% of the axons leaving the transplant reached the distal target. This technique of long-distance axon guidance may prove to be a useful strategy in reconstructing damaged neuronal circuits, such as the nigrostriatal pathway in Parkinson's disease., (© 2013.)
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- 2013
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58. Direct asymmetric syntheses of chiral aldehydes and ketones via N-acyl chiral auxiliary derivatives including chiral Weinreb amide equivalents.
- Author
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Davies SG, Fletcher AM, and Thomson JE
- Abstract
This article covers N-acyl chiral auxiliary-based approaches to the asymmetric synthesis of enantiopure aldehydes and ketones. The use of diastereoisomerically pure N-acyl derivatives of chiral auxiliaries (including chiral Weinreb amide equivalents) and their conversion to the corresponding enantiopure aldehydes and ketones in a single synthetic operation by treatment with a hydride reducing agent or an organometallic reagent, respectively, are highlighted.
- Published
- 2013
- Full Text
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59. A randomized controlled trial of peripheral blood mononuclear cell depletion in experimental human lung inflammation.
- Author
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Barr LC, Brittan M, Morris AC, McAuley DF, McCormack C, Fletcher AM, Richardson H, Connell M, Patel D, Wallace WA, Rossi AG, Davidson DJ, Manson L, Turner M, Hirani N, Walsh TS, Anderson NH, Dhaliwal K, and Simpson AJ
- Subjects
- Adolescent, Adult, Bronchoalveolar Lavage, Cytokines blood, Double-Blind Method, Humans, Leukocytes, Mononuclear, Male, Up-Regulation physiology, Young Adult, Inflammation Mediators physiology, Leukapheresis
- Abstract
Rationale: Depletion of monocytes reduces LPS-induced lung inflammation in mice, suggesting monocytes as potential therapeutic targets in acute lung injury., Objectives: To investigate whether depletion of circulating blood monocytes has beneficial effects on markers of systemic and pulmonary inflammation in a human model of acute lung inflammation., Methods: A total of 30 healthy volunteers were enrolled in a randomized controlled trial. Volunteers inhaled LPS at baseline, and were randomized to receive active mononuclear cell depletion by leukapheresis, or sham leukapheresis, in a double-blind fashion (15 volunteers per group). Serial blood counts were measured, bronchoalveolar lavage (BAL) was performed at 9 hours, and [(18)F]fluorodeoxyglucose positron emission tomography at 24 hours. The primary endpoint was the increment in circulating neutrophils at 8 hours., Measurements and Main Results: As expected, inhalation of LPS induced neutrophilia and an up-regulation of inflammatory mediators in the blood and lungs of all volunteers. There was no significant difference between the depletion and sham groups in the mean increment in blood neutrophil count at 8 hours (6.16 × 10(9)/L and 6.15 × 10(9)/L, respectively; P = 1.00). Furthermore, there were no significant differences in BAL neutrophils or protein, positron emission tomography-derived measures of global lung inflammation, or cytokine levels in plasma or BAL supernatant between the study groups. No serious adverse events occurred, and no symptoms were significantly different between the groups., Conclusions: These findings do not support a role for circulating human monocytes in the early recruitment of neutrophils during LPS-mediated acute lung inflammation in humans.
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- 2013
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60. Asymmetric syntheses of enantiopure C(5)-substituted transpentacins via diastereoselective Ireland-Claisen rearrangements.
- Author
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Davies SG, Fletcher AM, Roberts PM, Thomson JE, and Zammit CM
- Subjects
- Carboxylic Acids chemistry, Crystallography, X-Ray, Cycloleucine chemical synthesis, Cycloleucine chemistry, Molecular Conformation, Oxidation-Reduction, Stereoisomerism, Carboxylic Acids chemical synthesis, Cycloleucine analogs & derivatives
- Abstract
Asymmetric syntheses of (S,S,S)-2-amino-5-methylcyclopentanecarboxylic acid and (S,S,S)-2-amino-5-phenylcyclopentanecarboxylic acid were achieved in 9 steps from commercially available starting materials via the Ireland-Claisen rearrangement of two enantiopure β-amino allyl esters, followed by ring-closing metathesis, reduction and deprotection.
- Published
- 2013
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61. An analysis of mercury exposures among the adult population in New York State.
- Author
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Fletcher AM and Gelberg KH
- Subjects
- Educational Status, Female, Humans, Interviews as Topic, Male, Mercury blood, Mercury Poisoning blood, Mercury Poisoning etiology, Middle Aged, New York epidemiology, Racial Groups statistics & numerical data, Registries, Seafood adverse effects, Sex Factors, Environmental Exposure statistics & numerical data, Mercury Poisoning epidemiology
- Abstract
The extent of methylmercury exposures among adults in New York State (NYS) has not been well characterized. Over the past few years, the NYS Heavy Metals Registry (HMR) has seen an increase in both blood mercury tests being reported, and nonoccupational exposures to mercury, which appear primarily due to fish consumption. This study will, (1) Characterize the adults who are tested for blood mercury in NYS; (2) Examine the circumstances for blood mercury testing; and (3) Characterize this population in terms of exposure history, specifically those individuals who are non-occupationally exposed through a diet of seafood consumption in reference to blood mercury levels. Data available from HMR laboratory results, including basic demographics and test results, were combined with data from telephone interviews. The interview contains information on the reasons for testing, possible sources of exposure, and the individual's work and home environment. Approximately 99 % of adults reported to the HMR, with identifiable exposures to mercury, had non-occupational exposures resulting from seafood consumption. Common types of fish consumed include salmon, tuna, and swordfish, with 90 % of adults eating seafood a few times or more per week. Information will be provided on the reasons for being tested and the range of blood mercury levels in relation to their seafood consumption. NYS residents who frequently eat fish should be aware of what types of fish contain mercury and avoid or reduce consumption of fish with high mercury levels.
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- 2013
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62. Asymmetric syntheses of (-)-1-deoxymannojirimycin and (+)-1-deoxyallonojirimycin via a ring-expansion approach.
- Author
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Davies SG, Figuccia AL, Fletcher AM, Roberts PM, and Thomson JE
- Subjects
- 1-Deoxynojirimycin analogs & derivatives, 1-Deoxynojirimycin chemistry, Carbonates, Catalysis, Crystallography, X-Ray, Molecular Conformation, Molecular Structure, Stereoisomerism, 1-Deoxynojirimycin chemical synthesis, Amines chemistry
- Abstract
The asymmetric syntheses of (-)-1-deoxymannojirimycin and (+)-1-deoxyallonojirimycin are described herein. The ring-closing iodoamination of two epimeric bishomoallylic amines to give the corresponding 5-iodomethylpyrrolidines was followed by in situ ring-expansion to give two diastereoisomerically pure (>99:1 dr) cyclic carbonates. Subsequent deprotection gave (-)-1-deoxymannojirimycin and (+)-1-deoxyallonojirimycin as single diastereoisomers in 7.4 and 3.3% overall yield, respectively, from commercially available starting materials.
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- 2013
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63. Asymmetric synthesis of (-)-martinellic acid.
- Author
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Davies SG, Fletcher AM, Lee JA, Lorkin TJ, Roberts PM, and Thomson JE
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- Alkylation, Amides chemistry, Crystallography, X-Ray, Esters, Lithium chemistry, Molecular Conformation, Molecular Structure, Pyrroles chemistry, Quinolines chemistry, Stereoisomerism, Trifluoroacetic Acid chemistry, Pyrroles chemical synthesis, Quinolines chemical synthesis
- Abstract
A high-yielding total asymmetric synthesis of (-)-martinellic acid is reported. The conjugate addition of lithium (R)-N-allyl-N-(α-methyl-4-methoxybenzyl)amide to tert-butyl (E)-3-[2'-(N,N-diallylamino)-5'-bromophenyl]propenoate and alkylation of the resultant β-amino ester have been used as the key steps to install the C(9b) and C(3a) stereogenic centers, respectively, and a highly diastereoselective Wittig reaction/intramolecular Michael addition was then used to create the C(4) stereogenic center within this tricyclic molecular architecture.
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- 2013
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64. Asymmetric syntheses of APTO and AETD: the β-amino acid fragments within microsclerodermins C, D, and E.
- Author
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Davies SG, Fletcher AM, Foster EM, Lee JA, Roberts PM, and Thomson JE
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- Molecular Structure, Oxidation-Reduction, Peptides, Cyclic chemistry, Stereoisomerism, Amino Acids, Neutral chemical synthesis, Amino Acids, Neutral chemistry, Lithium chemistry, Peptide Fragments chemical synthesis, Peptide Fragments chemistry, Peptides, Cyclic chemical synthesis
- Abstract
Efficient asymmetric syntheses of APTO and AETD, the highly functionalized β-amino acid fragments within microsclerodermins C, D, and E, are reported. The conjugate addition of lithium (R)-N-benzyl-N-(α-methylbenzyl)amide to tert-butyl (E,E)-7-(triisopropylsilyloxy)hepta-2,4-dienoate and in situ enolate oxidation with (-)-camphorsulfonyloxaziridine, diastereoselective dihydroxylation of a 2,3-syn-γ,δ-unsaturated-α-hydroxy-β-amino ester derivative under Donohoe conditions, and a Julia-Kocieński olefination were used as the key steps.
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- 2013
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65. A simultaneous voltammetric temperature and humidity sensor.
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Xiong L, Fletcher AM, Davies SG, Norman SE, Hardacre C, and Compton RG
- Abstract
We report the simultaneous measurement of temperature and humidity by analysing square wave voltammetric responses of two ferrocene derivatives, decamethylferrocene (DmFc) and 1,2-diferrocenylethylene (bisferrocene, BisFc) in 1-(2-methoxyethyl)-1-methyl-pyrrolidinium tris(pentafluoroethyl)trifluorophosphate ([Moepyrr][FAP]). These two molecules produce three peaks in square wave voltammetry. Through study of the peak potentials of BisFc/BisFc(+) (vs. DmFc/DmFc(+)) and BisFc(+)/BisFc(2+) (vs. DmFc/DmFc(+)) over a temperature range of 298 K to 318 K and humidity range of 1% to 50% using square wave voltammetry, the temperature and humidity dependences of the relative peak potentials were investigated. A reliable method to calculate the humidity and temperature based on the voltammetric experiment is characterised and demonstrated.
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- 2012
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66. Individualizing hemodynamic optimization during the management of circulatory collapse.
- Author
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Fletcher AM, Andrews JCh, and Frampton AE
- Abstract
The best method of hemodynamic monitoring to guide the resuscitation and management of the critically ill patient is unclear. The evaluated article presents data from a prospective randomized controlled trial that recruited 120 shocked patients (n = 60 in each arm) to compare volume-limited versus pressure-limited hemodynamic management. Patients were randomized into two protocolized fluid therapy algorithms using either the upper limits of hemodynamic indices of arterial pulse contour cardiac output and transpulmonary thermodilution (TPTD) analysis (extra vascular lung water <10 ml/kg and global end-diastolic volume index 850 ml/m(2)) or pulmonary artery catheter pressures (<18-20 mmHg). Primary outcomes were ventilator-free days, duration of mechanical ventilation, intensive care unit and hospital stay. Secondary outcomes included sequential organ failure assessment scores and mortality. No benefit was found between pulmonary artery catheter and TPTD in the primary outcomes; interestingly, the nonseptic patients who were monitored with TPTD spent longer on mechanical ventilation and in the intensive care unit.
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- 2012
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67. Ammonium-directed olefinic epoxidation: kinetic and mechanistic insights.
- Author
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Brennan MB, Claridge TD, Compton RG, Davies SG, Fletcher AM, Henstridge MC, Hewings DS, Kurosawa W, Lee JA, Roberts PM, Schoonen AK, and Thomson JE
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- Epoxy Compounds chemistry, Kinetics, Molecular Structure, Stereoisomerism, Alkenes chemistry, Epoxy Compounds chemical synthesis, Quaternary Ammonium Compounds chemistry
- Abstract
The ammonium-directed olefinic epoxidations of a range of differentially N-substituted cyclic allylic and homoallylic amines (derived from cyclopentene, cyclohexene, and cycloheptene) have been investigated, and the reaction kinetics have been analyzed. The results of these studies suggest that both the ring size and the identity of the substituents on nitrogen are important in determining both the overall rate and the stereochemical outcome of the epoxidation reaction. In general, secondary amines or tertiary amines with nonsterically demanding substituents on nitrogen are superior to tertiary amines with sterically demanding substituents on nitrogen in their ability to promote the oxidation reaction. Furthermore, in all cases examined, the ability of the (in situ formed) ammonium substituent to direct the stereochemical course of the epoxidation reaction is either comparable or superior to that of the analogous hydroxyl substituent. Much slower rates of ring-opening of the intermediate epoxides are observed in cyclopentene-derived and cycloheptene-derived allylic amines as compared with their cyclohexene-derived allylic and homoallylic amine counterparts, allowing for isolation of these intermediates in both of the former cases.
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- 2012
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68. Endoscopic resection of calcifying pseudoneoplasm of the neuraxis (CAPNON) of the anterior skull base with sinonasal extension.
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Fletcher AM, Greenlee JJ, Chang KE, Smoker WR, Kirby PA, and O'Brien EK
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- Humans, Magnetic Resonance Imaging, Male, Tomography Scanners, X-Ray Computed, Young Adult, Calcinosis complications, Calcinosis pathology, Calcinosis surgery, Central Nervous System Diseases complications, Central Nervous System Diseases pathology, Central Nervous System Diseases surgery, Endoscopy methods, Skull Base surgery, Skull Neoplasms
- Abstract
We present a calcifying pseudoneoplasm of the neuraxis (CAPNON) of the anterior skull base that was resected endoscopically. The clinical details are reported with a review of the relevant literature. CAPNON, although rare, should be considered in the differential diagnosis of tumors presenting along the anterior skull base with radiographic characteristics consistent with a fibro-osseous lesion. Endoscopic resection of these lesions is feasible in select patients with sinonasal extension., (Copyright © 2012. Published by Elsevier Ltd.)
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- 2012
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69. Tuning solute redox potentials by varying the anion component of room temperature ionic liquids.
- Author
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Xiong L, Fletcher AM, Davies SG, Norman SE, Hardacre C, and Compton RG
- Abstract
The electrode potentials for the two one electron oxidations of 1,2-diferrocenylethylene (bisferrocene, BF) were studied relative to that of the one electrode oxidation of decamethylferrocene in a variety of RTILs. The difference in these potentials was found to be very sensitive to the anion component of the ionic liquid showing the scope of these solutes as 'designer media' to tune the thermodynamic properties of solutes dissolved in them.
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- 2012
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70. An electrochemical thermometer: voltammetric measurement of temperature and its application to amperometric gas sensing.
- Author
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Xiong L, Fletcher AM, Ernst S, Davies SG, and Compton RG
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- Air analysis, Ethylenes chemistry, Ferrous Compounds chemistry, Imidazoles chemistry, Metallocenes, Oxidation-Reduction, Oxygen analysis, Phenylenediamines chemistry, Temperature, Electrochemical Techniques, Gases analysis, Thermometers
- Abstract
We report a temperature sensing system incorporated into an amperometric oxygen sensor. In the first part of this work, we introduce temperature sensing systems based upon voltammetric responses of both single molecule (1,2-diferrocenylethylene in 1-propyl-3-methylimidazolium bistrifluoromethylsulfonylimide) and two independent molecules (decamethylferrocene and N,N,N',N'-tetramethyl-p-phenylenediamine in 1-ethyl-3-methylimidazolium tetracyanoborate) respectively. In both systems, the difference in the formal potentials of two redox centres was measured as a function of temperature. The former was recorded as the peak difference in square wave voltammetry with the peak potential difference increases linearly with the increasing temperature. In order to show proof-of-concept in relation to a gas sensor, the latter system was investigated in the presence of oxygen, where the concentration and diffusion coefficient of oxygen varied with temperature, as well as the peak difference discussed previously, were studied in the presence of pure oxygen and dried air using chronoamperometry. A negligible variation of concentration of oxygen from both sources with temperature over the range 298 K to 318 K is demonstrated. These results obtained from pure oxygen and dried air were compared and a ca. 79% drop of cathodic signal from pure oxygen to dried air was found which is consistent with the percentage of oxygen in air. The diffusion coefficient of oxygen was related to temperature using an Arrhenius plot (natural log of diffusion coefficient as a function of reciprocal temperature), yielding a linear graph with high correlation. All experiments gave a high reproducibility.
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- 2012
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71. Coronary arterial 18F-sodium fluoride uptake: a novel marker of plaque biology.
- Author
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Dweck MR, Chow MW, Joshi NV, Williams MC, Jones C, Fletcher AM, Richardson H, White A, McKillop G, van Beek EJ, Boon NA, Rudd JH, and Newby DE
- Subjects
- Aged, Aorta, Thoracic diagnostic imaging, Aorta, Thoracic pathology, Biomarkers analysis, Coronary Angiography methods, Coronary Vessels diagnostic imaging, Coronary Vessels pathology, Female, Humans, Male, Middle Aged, Observer Variation, Prospective Studies, Reproducibility of Results, Risk Assessment, Sensitivity and Specificity, Severity of Illness Index, Tomography, X-Ray Computed, Coronary Artery Disease diagnostic imaging, Fluorine Radioisotopes pharmacokinetics, Fluorodeoxyglucose F18 pharmacokinetics, Positron-Emission Tomography, Sodium Fluoride pharmacokinetics
- Abstract
Objectives: With combined positron emission tomography and computed tomography (CT), we investigated coronary arterial uptake of 18F-sodium fluoride (18F-NaF) and 18F-fluorodeoxyglucose (18F-FDG) as markers of active plaque calcification and inflammation, respectively., Background: The noninvasive assessment of coronary artery plaque biology would be a major advance particularly in the identification of vulnerable plaques, which are associated with specific pathological characteristics, including micro-calcification and inflammation., Methods: We prospectively recruited 119 volunteers (72 ± 8 years of age, 68% men) with and without aortic valve disease and measured their coronary calcium score and 18F-NaF and 18F-FDG uptake. Patients with a calcium score of 0 were used as control subjects and compared with those with calcific atherosclerosis (calcium score >0)., Results: Inter-observer repeatability of coronary 18F-NaF uptake measurements (maximum tissue/background ratio) was excellent (intra-class coefficient 0.99). Activity was higher in patients with coronary atherosclerosis (n = 106) versus control subjects (1.64 ± 0.49 vs. 1.23 ± 0.24; p = 0.003) and correlated with the calcium score (r = 0.652, p < 0.001), although 40% of those with scores >1,000 displayed normal uptake. Patients with increased coronary 18F-NaF activity (n = 40) had higher rates of prior cardiovascular events (p = 0.016) and angina (p = 0.023) and higher Framingham risk scores (p = 0.011). Quantification of coronary 18F-FDG uptake was hampered by myocardial activity and was not increased in patients with atherosclerosis versus control subjects (p = 0.498)., Conclusions: 18F-NaF is a promising new approach for the assessment of coronary artery plaque biology. Prospective studies with clinical outcomes are now needed to assess whether coronary 18F-NaF uptake represents a novel marker of plaque vulnerability, recent plaque rupture, and future cardiovascular risk. (An Observational PET/CT Study Examining the Role of Active Valvular Calcification and Inflammation in Patients With Aortic Stenosis; NCT01358513)., (Copyright © 2012 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)
- Published
- 2012
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72. Polysubstituted piperidines via iodolactonization: application to the asymmetric synthesis of (+)-pseudodistomin D.
- Author
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Davies SG, Fletcher AM, Lee JA, Roberts PM, Russell AJ, Taylor RJ, Thomson AD, and Thomson JE
- Subjects
- Alkaloids chemistry, Animals, Crystallography, X-Ray, Esters, Molecular Conformation, Molecular Structure, Piperidines chemistry, Stereoisomerism, Urochordata chemistry, Alkaloids chemical synthesis, Piperidines chemical synthesis
- Abstract
Conjugate addition of lithium (S)-N-allyl-N-(α-methyl-p-methoxybenzyl)amide to methyl (E,E)-hepta-2,5-dienoate furnished the corresponding β-amino ester. N-Protecting group manipulation, ring-closing metathesis, and ester hydrolysis gave enantiopure [N(1')-tert-butoxycarbonyl-1,2,3,6-tetrahydropyridin-2'-yl]ethanoic acid. Subsequent iodolactonization gave a bicyclic iodolactone scaffold. This key intermediate was elaborated to (+)-pseudodistomin D [in >99% ee and 7% yield over 16 steps from methyl (E,E)-hepta-2,5-dienoate].
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- 2012
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73. Factors correlating with burnout in practicing otolaryngologists.
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Fletcher AM, Pagedar N, and Smith RJ
- Subjects
- Adult, Cross-Sectional Studies, Humans, Middle Aged, Risk Assessment, Risk Factors, Burnout, Professional epidemiology, Occupational Diseases epidemiology, Otolaryngology
- Abstract
Objective: This study sought to determine which demographic and practice characteristics were predictive of professional burnout in otolaryngologists., Study Design: Cross-sectional survey., Setting: Tertiary care hospital., Subjects and Methods: Postal mailings, including the Maslach Burnout Inventory (MBI), were sent to alumni of the University of Iowa Hospitals and Clinics otolaryngology program. Participants completed the MBI according to the enclosed instructions. In addition, they answered a brief questionnaire comprising 8 items designed to collect demographic information. The MBI was then scored and subjects were classified according to their degree of burnout. Statistical analysis was then performed, and correlations were used to summarize associations between continuous variables., Results: This study had a response rate of 49% to the survey. Of the respondents, 3.5% met criteria for burnout syndrome, and 16% were classified as having high levels of burnout according to the MBI. Young age, number of hours worked per week, and length of time in practice were found to be statistically significant predictors of burnout. In addition, the length of time married and the presence of children in the home were also significant predictors of burnout., Conclusion: The authors report an investigation of burnout in practicing otolaryngologists using a validated instrument with correlation to potentially modifiable risk factors. The experience of burnout was found to correlate significantly with both personal and professional factors, each of which can potentially be addressed to curb the incidence of burnout. Further understanding of the potential risk factors for burnout is necessary to minimize and prevent burnout among practicing otolaryngologists.
- Published
- 2012
- Full Text
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74. Assessment of valvular calcification and inflammation by positron emission tomography in patients with aortic stenosis.
- Author
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Dweck MR, Jones C, Joshi NV, Fletcher AM, Richardson H, White A, Marsden M, Pessotto R, Clark JC, Wallace WA, Salter DM, McKillop G, van Beek EJ, Boon NA, Rudd JH, and Newby DE
- Subjects
- Aged, Aged, 80 and over, Aortic Valve pathology, Aortic Valve Stenosis pathology, Calcinosis epidemiology, Calcinosis pathology, Cardiomyopathies epidemiology, Cardiomyopathies pathology, Cohort Studies, Female, Fluorodeoxyglucose F18, Humans, Inflammation diagnosis, Inflammation diagnostic imaging, Inflammation epidemiology, Male, Prospective Studies, Tomography, X-Ray Computed methods, Aortic Valve diagnostic imaging, Aortic Valve Stenosis diagnostic imaging, Aortic Valve Stenosis epidemiology, Calcinosis diagnostic imaging, Cardiomyopathies diagnostic imaging, Positron-Emission Tomography methods
- Abstract
Background: The pathophysiology of aortic stenosis is incompletely understood, and the relative contributions of valvular calcification and inflammation to disease progression are unknown., Methods and Results: Patients with aortic sclerosis and mild, moderate, and severe stenosis were compared prospectively with age- and sex-matched control subjects. Aortic valve severity was determined by echocardiography. Calcification and inflammation in the aortic valve were assessed by 18F-sodium fluoride (18F-NaF) and 18F-fluorodeoxyglucose (18F-FDG) uptake with the use of positron emission tomography. One hundred twenty-one subjects (20 controls; 20 aortic sclerosis; 25 mild, 33 moderate, and 23 severe aortic stenosis) were administered both 18F-NaF and 18F-FDG. Quantification of tracer uptake within the valve demonstrated excellent interobserver repeatability with no fixed or proportional biases and limits of agreement of ±0.21 (18F-NaF) and ±0.13 (18F-FDG) for maximum tissue-to-background ratios. Activity of both tracers was higher in patients with aortic stenosis than in control subjects (18F-NaF: 2.87±0.82 versus 1.55±0.17; 18F-FDG: 1.58±0.21 versus 1.30±0.13; both P<0.001). 18F-NaF uptake displayed a progressive rise with valve severity (r(2)=0.540, P<0.001), with a more modest increase observed for 18F-FDG (r(2)=0.218, P<0.001). Among patients with aortic stenosis, 91% had increased 18F-NaF uptake (>1.97), and 35% had increased 18F-FDG uptake (>1.63). A weak correlation between the activities of these tracers was observed (r(2)=0.174, P<0.001)., Conclusions: Positron emission tomography is a novel, feasible, and repeatable approach to the evaluation of valvular calcification and inflammation in patients with aortic stenosis. The frequency and magnitude of increased tracer activity correlate with disease severity and are strongest for 18F-NaF., Clinical Trial Registration: http://www.clinicaltrials.gov. Unique identifier: NCT01358513.
- Published
- 2012
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75. Evoked dopamine overflow is augmented in the striatum of calcitriol treated rats.
- Author
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Cass WA, Peters LE, Fletcher AM, and Yurek DM
- Subjects
- Animals, Calcitriol therapeutic use, Dopamine adverse effects, Male, Parkinsonian Disorders drug therapy, Parkinsonian Disorders metabolism, Parkinsonian Disorders physiopathology, Presynaptic Terminals drug effects, Presynaptic Terminals metabolism, Rats, Rats, Inbred F344, Up-Regulation physiology, Calcitriol pharmacology, Corpus Striatum drug effects, Corpus Striatum metabolism, Corpus Striatum physiopathology, Dopamine metabolism, Up-Regulation drug effects
- Abstract
Calcitriol, the active metabolite of vitamin D, has been shown to have significant effects on the brain. These actions include reducing the severity of some central nervous system lesions, possibly by upregulating trophic factors such as glial cell line-derived neurotrophic factor (GDNF). GDNF has substantial effects on the nigrostriatal dopamine (DA) system of young adult, aged and lesioned animals. Thus, the administration of calcitriol may lead to significant effects on nigrostriatal DA neuron functioning. The present experiments were designed to examine the ability of calcitriol to alter striatal DA release, and striatal and nigral tissue levels of DA. Male Fischer-344 rats were administered vehicle or calcitriol (0.3, 1.0, or 3.0 μg/kg, s.c.) once daily for eight consecutive days. Three weeks later in vivo microdialysis experiments were conducted to measure basal and stimulus evoked overflow of DA from the striatum. Basal levels of extracellular DA were not significantly affected by the calcitriol treatments. However, the 1.0 and 3.0 μg/kg doses of calcitriol led to increases in both potassium and amphetamine evoked overflow of striatal DA. Although post-mortem tissue levels of striatal DA were not altered by the calcitriol injections, nigral tissue levels of DA and its main metabolites were increased by both the 1.0 and 3.0 μg/kg doses of calcitriol. In a separate group of animals GDNF levels were augmented in the striatum and substantia nigra after eight consecutive daily injections of calcitriol. These results suggest that systemically administered calcitriol can upregulate dopaminergic release processes in the striatum and DA levels in the substantia nigra. Increases in the levels of endogenous GDNF following calcitriol treatment may in part be responsible for these changes. The ability of calcitriol to lead to augmented DA release in the striatum suggests that calcitriol may be beneficial in disease processes involving dopaminergic dysfunction., (Copyright © 2011 Elsevier Ltd. All rights reserved.)
- Published
- 2012
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76. Transgene expression in the striatum following intracerebral injections of DNA nanoparticles encoding for human glial cell line-derived neurotrophic factor.
- Author
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Fletcher AM, Kowalczyk TH, Padegimas L, Cooper MJ, and Yurek DM
- Subjects
- Animals, Disease Models, Animal, Drug Delivery Systems methods, Gene Expression Regulation genetics, Glial Cell Line-Derived Neurotrophic Factor administration & dosage, Humans, Male, Microinjections methods, Nanoparticles therapeutic use, Parkinsonian Disorders genetics, Parkinsonian Disorders metabolism, Parkinsonian Disorders therapy, Primary Cell Culture, Rats, Rats, Sprague-Dawley, Brain Chemistry genetics, Corpus Striatum metabolism, DNA administration & dosage, Genetic Therapy methods, Glial Cell Line-Derived Neurotrophic Factor genetics, Nanoparticles administration & dosage
- Abstract
A goal of our studies is to develop a potential therapeutic for Parkinson's disease (PD) by a human glial cell line-derived neurotrophic factor (hGDNF) expression plasmid administered to the rat striatum as a compacted DNA nanoparticle (DNP) and which will generate long-term hGDNF expression at biologically active levels. In the present study, we used a DNA plasmid encoding for hGDNF and a polyubiquitin C (UbC) promoter that was previously shown to have activity in both neurons and glia, but primarily in glia. A two-fold improvement was observed at the highest plasmid dose when using hGDNF DNA incorporating sequences found in RNA splice variant 1 compared with splice variant 2; of note, the splice variant 2 sequence is used in most preclinical studies. This optimized expression cassette design includes flanking scaffold matrix attachment elements (S/MARs) as well as a CpG-depleted prokaryotic domain and, where possible, eukaryotic elements. Stable long-term GDNF activity at levels 300-400% higher than baseline was observed following a single intracerebral injection. In a previous study, DNP plasmids encoding for reporter genes had been successful in generating long-term reporter transgene activity in the striatum (>365 days) and in this study produced sustained GDNF activity at the longest assessed time point (6 months)., (Copyright © 2011 IBRO. Published by Elsevier Ltd. All rights reserved.)
- Published
- 2011
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77. DNA nanoparticles: detection of long-term transgene activity in brain using bioluminescence imaging.
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Yurek DM, Fletcher AM, McShane M, Kowalczyk TH, Padegimas L, Weatherspoon MR, Kaytor MD, Cooper MJ, and Ziady AG
- Subjects
- Analysis of Variance, Animals, Brain metabolism, Brain Chemistry, Genetic Vectors, Histocytochemistry methods, Luciferases genetics, Luciferases metabolism, Male, Microinjections, Rats, Rats, Sprague-Dawley, Transgenes, Brain physiology, DNA administration & dosage, Gene Transfer Techniques, Luminescent Measurements methods, Nanoparticles administration & dosage
- Abstract
In this study, we used bioluminescence imaging (BLI) to track long-term transgene activity following the transfection of brain cells using a nonviral gene therapy technique. Formulations of deoxyribonucleic acid (DNA) combined with 30-mer lysine polymers (substituted with 10 kDa polyethylene glycol) form nanoparticles that transfect brain cells in vivo and produce transgene activity. Here we show that a single intracerebral injection of these DNA nanoparticles (DNPs) into the rat cortex, striatum, or substantia nigra results in long-term and persistent luciferase transgene activity over an 8- to 11-week period as evaluated by in vivo BLI analysis, and single injections of DNPs into the mouse striatum showed stable luciferase transgene activity for 1 year. Compacted DNPs produced in vivo signals 7- to 34-fold higher than DNA alone. In contrast, ex vivo BLI analysis, which is subject to less signal quenching from surrounding tissues, demonstrated a DNP to DNA alone ratio of 76- to 280-fold. Moreover, the ex vivo BLI analysis confirmed that signals originated from the targeted brain structures. In summary, BLI permits serial analysis of luciferase transgene activity at multiple brain locations following gene transfer with DNPs. Ex vivo analysis may permit more accurate determination of relative activities of gene transfer vectors.
- Published
- 2011
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78. Local repair of persistent tracheocutaneous fistulas.
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Khaja SF, Fletcher AM, and Hoffman HT
- Subjects
- Adult, Aged, Female, Humans, Male, Middle Aged, Postoperative Complications, Reoperation, Retrospective Studies, Risk Factors, Surgical Procedures, Operative methods, Tracheoesophageal Fistula etiology, Tracheostomy, Tracheoesophageal Fistula surgery
- Abstract
Tracheocutaneous fistulas may persist after tracheostomy. Suture closure of the fistula may result in complications, including infection, wound dehiscence, and pneumomediastinum. We present a simplified and relatively safe technique to close persistent fistulas that may be performed under local anesthesia. A retrospective chart review was performed on 13 patients who were successfully treated, including 1 with incomplete closure that was successfully addressed by additional procedures. Our review included analysis of reported risk factors for persistence of tracheocutaneous fistulas: previous irradiation of the neck, an extended duration of cannulation, previous tracheostomies, obesity, and use of a Bjork flap or 4-flap epithelial-lined tracheostomy. All 13 patients in the study were found to have at least 1 of these risk factors.
- Published
- 2011
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79. One-pot conversions of olefins to cyclic carbonates and secondary allylic and homoallylic amines to cyclic carbamates.
- Author
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Davies SG, Fletcher AM, Kurosawa W, Lee JA, Poce G, Roberts PM, Thomson JE, and Williamson DM
- Abstract
Sequential treatment of a 1,2-disubstituted olefin with m-CPBA, Br3CCO2H, and DBU results in the one-pot, stereospecific conversion of the olefin to the corresponding disubstituted cyclic carbonate (1,3-dioxolan-2-one). The reaction proceeds via an initial epoxidation followed by S(N)2-type epoxide ring opening by Br3CCO2H and subsequent base-promoted carbonate formation upon elimination of bromoform. When a solution of a secondary allylic or homoallylic amine and Br3CCO2H is sequentially treated with m-CPBA then DBU, the product of the reaction is a cyclic carbamate (1,3-oxazolidin-2-one or 1,3-oxazinan-2-one).
- Published
- 2010
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80. I-123 MIBG cardiac uptake measurements: limitations of collimator choice and scatter correction in the clinical context.
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Fletcher AM, Motherwell DW, Small AD, McCurrach GM, Goodfield NE, Petrie MC, Martin W, and Cobbe SM
- Subjects
- 3-Iodobenzylguanidine administration & dosage, Artifacts, Biological Transport, Female, Heart Failure diagnostic imaging, Heart Failure metabolism, Humans, Injections, Male, Mediastinum, Middle Aged, Radiation Dosage, Radionuclide Imaging, 3-Iodobenzylguanidine pharmacokinetics, Myocardium metabolism, Scattering, Radiation
- Abstract
Objective: Low uptake of metaiodobenzylguanidine (MIBG) in patients with heart failure generally indicates poor prognosis. Our objective was to determine the best method for calculating I-123 MIBG uptake. MIBG uptake as a percentage of the injected dose is presented as an alternative method for serial assessment., Methods: Patients with chronic heart failure were imaged with I-123 MIBG with both a medium-energy (ME) collimator and a low-energy high-sensitivity (LEHS) collimator. Scatter correction was used to correct the LEHS images. Heart-to-mediastinal (H/M) ratio and the percentage of myocardial uptake of MIBG were obtained., Results: Mean H/M ratios for the ME images, LEHS images and scatter-corrected LEHS images were 2.45+/-0.61, 2.22+/-0.47 and 2.51+/-0.62, respectively. Mean H/M ratio was significantly different among all the three sets (P<0.001) of images. The average difference in H/M ratios between the ME images and LEHS images was lower when scatter correction was applied (4.95% vs. 9.79%). The error in calculating the myocardial uptake as a percentage of the injected dose was significantly lower than the error in calculating H/M ratio (0.2 vs.10.2% LEHS; 0.3 vs.16.0% ME; 0.2 vs.11.8% LEHS scatter corrected)., Conclusion: For quantitative assessment of H/M ratio in I-123 MIBG imaging a LEHS collimator can be used in place of a ME collimator to achieve better counting statistics, but scatter correction must be used. The calculation of the myocardial uptake as a percentage of the injected dose has potential as an alternative method of measurement, particularly for serial assessment., (2010 Wolters Kluwer Health / Lippincott Williams & Wilkins.)
- Published
- 2010
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81. Strain difference in the up-regulation of FGF-2 protein following a neurotoxic lesion of the nigrostriatal pathway.
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Yurek DM, Fletcher AM, Peters LE, and Cass WA
- Subjects
- Animals, Chromatography, High Pressure Liquid, Enzyme-Linked Immunosorbent Assay, Immunohistochemistry, Male, Rats, Rats, Inbred F344, Rats, Sprague-Dawley, Species Specificity, Corpus Striatum metabolism, Fibroblast Growth Factor 2 metabolism, Substantia Nigra metabolism, Up-Regulation
- Abstract
Lesions of the nigrostriatal pathway are known to induce a compensatory up-regulation of various neurotrophic factors. In this study we examined protein content of basic fibroblast growth factor (FGF-2) in tissue samples taken from the ventral midbrain and striatum at two different time points following a neurotoxic lesion of the nigrostriatal pathway in two different rat strains, the outbred Sprague-Dawley (SD) and inbred F344 9 Brown Norway F1 hybrid (F344BNF1). Despite both rat strains having comparable lesions of the nigrostriatal pathway, we observed a difference in the temporal up-regulation of FGF-2 in ventral midbrain samples taken from the side ipsilateral to the lesion. Basic FGF was significantly upregulated in ventral midbrain in SD rats 1 week post-lesion while we did not observe an up-regulation of FGF-2 in the lesioned ventral midbrain of F344BNF1 at this same time point. However, both strains showed a significant up-regulation of FGF-2 in the lesioned ventral midbrain 3 weeks post-lesion. Sprague-Dawley rats also appeared to be more sensitive to the lesion in terms of up-regulating FGF-2 expression. The differences reported here suggest currently unknown genetic differences between these two strains may be important factors for regulating the compensatory release of neurotrophic factors, such as FGF-2, in response to a neurotoxic lesion of the nigrostriatal pathway.
- Published
- 2010
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82. Small molecule colorimetric probes for specific detection of human arylamine N-acetyltransferase 1, a potential breast cancer biomarker.
- Author
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Laurieri N, Crawford MH, Kawamura A, Westwood IM, Robinson J, Fletcher AM, Davies SG, Sim E, and Russell AJ
- Subjects
- Animals, Arylamine N-Acetyltransferase antagonists & inhibitors, Female, Humans, Isoenzymes antagonists & inhibitors, Mice, Models, Molecular, Arylamine N-Acetyltransferase analysis, Biomarkers, Tumor analysis, Breast Neoplasms enzymology, Colorimetry methods, Isoenzymes analysis
- Abstract
The identification, synthesis, and evaluation of a series of naphthoquinone derivatives as selective inhibitors of human arylamine N-acetyltransferase 1 and mouse arylamine N-acetyltransferase 2 are described. The compounds undergo a distinctive color change (red --> blue) upon binding to these human and mouse NAT isoenzymes driven by a proton transfer event. No color change is observed in the presence of functionally distinct but highly similar isoenzymes which are >70% identical. These molecules may be used as sensors to detect the presence of human NAT1 in cell lysates.
- Published
- 2010
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83. Enantiospecific stereodivergent synthesis of trans- and cis-N(2),3-dimethyl-4-phenyl-1,2,3,4-tetrahydroisoquinolines.
- Author
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Coote SJ, Davies SG, Fletcher AM, Roberts PM, and Thomson JE
- Subjects
- Cyclization, Ephedrine chemistry, Ethanolamines chemistry, Stereoisomerism, Isoquinolines chemical synthesis
- Abstract
The acid-promoted cyclizations of a range of N-benzylethanolamines (derived from pseudoephedrine or ephedrine) give the corresponding trans-N(2),3-dimethyl-4-phenyl-1,2,3,4-tetrahydroisoquinolines with high levels of diastereoselectivity and in good yields of isolated product. The cyclizations of the corresponding chromium tricarbonyl complexes are rendered completely stereoselective. Acid-promoted cyclization of N-(3',4'-dimethoxybenzyl)ephedrine and its chromium tricarbonyl complex occur with complementary diastereoselectivities to give trans- and cis-N(2),3-dimethyl-4-phenyl-6,7-dimethoxy-1,2,3,4-tetrahydro-isoquinoline, respectively, in >99:1 d.r. The latter is consistent with a "double inversion" mechanism, which involves neighboring group participation by the chromium tricarbonyl moiety followed by rearomatization to give the corresponding cis-tetrahydroisoquinoline with overall retention of configuration.
- Published
- 2010
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84. Incisor degeneration in rats induced by vascular endothelial growth factor/fibroblast growth factor receptor tyrosine kinase inhibition.
- Author
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Fletcher AM, Bregman CL, Woicke J, Salcedo TW, Zidell RH, Janke HE, Fang H, Janusz WJ, Schulze GE, and Mense MG
- Subjects
- Animals, Dentin metabolism, Dose-Response Relationship, Drug, Female, Incisor pathology, Male, Necrosis, Odontoblasts drug effects, Odontoblasts metabolism, Rats, Rats, Sprague-Dawley, Toxicity Tests, Angiogenesis Inhibitors toxicity, Incisor drug effects, Protein Kinase Inhibitors toxicity, Pyrroles toxicity, Receptor, Fibroblast Growth Factor, Type 1 antagonists & inhibitors, Triazines toxicity, Vascular Endothelial Growth Factor Receptor-2 antagonists & inhibitors
- Abstract
BMS-645737, an inhibitor of vascular endothelial growth factor (VEGF) receptor-2 and fibroblast growth factor (FGF) receptor-1, has anti-angiogenic activity and was evaluated in nonclinical studies as a treatment for cancer. This article characterizes the BMS-645737-induced clinical, gross, and histologic lesions of incisor teeth in Sprague-Dawley (SD) rats. Rats received 0 800 mg/kg BMS-645737 in a single-dose study or consecutive daily doses of 0 20 mg/kg/day in a 1-month study. The reversibility of these effects was assessed in the 1-month study. White discoloration and fracture of incisors were observed clinically and grossly in the 1-month study. In both studies, dose-dependent histopathologic lesions of incisors were degeneration and/or necrosis of odontoblasts and ameloblasts; decreased mineralization of dentin; inflammation and necrosis of the dental pulp; and edema, congestion, and hemorrhage in the pulp and periodontal tissue adjacent to the enamel organ. Partial recovery was observed at lower doses after a two-week dose-free period in the one-month study. Drug-induced incisor lesions were considered to be related to the pharmacologic inhibitory effects on VEGF and FGF signaling, that is, inhibition of growth and maintenance of small-diameter vessels that support the formation of dentin and enamel in growing teeth and/or to perturbances of function of odontoblasts and ameloblasts or their precursors.
- Published
- 2010
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85. Ammonium-directed oxidation of cyclic allylic and homoallylic amines.
- Author
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Bond CW, Cresswell AJ, Davies SG, Fletcher AM, Kurosawa W, Lee JA, Roberts PM, Russell AJ, Smith AD, and Thomson JE
- Abstract
The ammonium-directed olefinic oxidation of a range of cyclic allylic and homoallylic amines has been investigated. Functionalization of a range of allylic 3-(N,N-dibenzylamino)cycloalk-1-enes with m-CPBA in the presence of Cl(3)CCO(2)H gives exclusively the corresponding syn-epoxide for the 5-membered ring (>99:1 dr), the anti-epoxide for the 8-membered ring (>99:1 dr), and predominantly the anti-epoxide for the 7-membered ring (94:6 dr). Oxidation of the homoallylic amines 3-(N-benzylamino)methylcyclohex-1-ene and 3-(N,N-dibenzylamino)methylcyclohex-1-ene gave, in both cases, the corresponding N-protected 1,2-anti-2,3-syn-3-aminomethylcyclohexane-1,2-diol with high levels of diastereoselectivity (>or=90:10 dr). The versatile synthetic intermediates resulting from these oxidation reactions are readily transformed into a range of amino diols.
- Published
- 2009
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86. Ultrasound-guided needle localization of recurrent paratracheal thyroid cancer.
- Author
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Fletcher AM, Preston TW, Kuehn DM, Clark ED, Van Daele D, and Hoffman H
- Subjects
- Carcinoma, Papillary diagnostic imaging, Carcinoma, Papillary secondary, Female, Humans, Middle Aged, Neoplasm Recurrence, Local pathology, Thyroid Neoplasms diagnostic imaging, Thyroid Neoplasms pathology, Ultrasonography, Carcinoma, Papillary surgery, Neck Dissection methods, Neoplasm Recurrence, Local diagnostic imaging, Neoplasm Recurrence, Local surgery, Surgery, Computer-Assisted, Thyroid Neoplasms surgery
- Abstract
Objectives: Ultrasound-guided needle localization techniques have been used to direct the resection of targeted axillary lymph nodes in the management of breast cancer. To date, there has been only one other description of this technique as a localization method to direct cancer resection in the neck. We offer further support for the broader application of this technique by reporting its use in the successful identification and resection of recurrent papillary thyroid cancer after a paratracheal node dissection failed to localize the cancer., Methods: We report a case and discuss the relevant literature regarding ultrasound-guided localization and resection of recurrent well-differentiated thyroid cancer., Results: We were able to achieve successful identification and resection of recurrent papillary thyroid cancer using this technique., Conclusions: This technique may be useful in the treatment of selected cases of recurrent thyroid cancer to increase the efficacy and safety of surgical resection.
- Published
- 2009
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87. Free-range RSS feeds and farm-raised journals: what to expect when using RSS as a TOC service.
- Author
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Fletcher AM
- Subjects
- Abstracting and Indexing methods, Periodicals as Topic, Databases, Factual, Information Dissemination methods, Information Storage and Retrieval methods, Libraries, Medical organization & administration, User-Computer Interface
- Abstract
Anyone who has tried to set up RSS feeds with or for a patron knows that the RSS feeds for e-journals can behave wildly, like free-range cattle, while the e-journals that libraries subscribe to tend to be more like farm-raised cattle, because they are packaged for institutions rather than individuals. Because of this disconnect, the experience of teaching RSS feeds to one's patrons can be fraught with "oops" moments. Knowing what to expect can help librarians prepare to teach patrons to use RSS feeds without scaring them away from a powerful tool. This article will discuss some problems to expect and ways to work around them.
- Published
- 2009
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88. Long-term transgene expression in the central nervous system using DNA nanoparticles.
- Author
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Yurek DM, Fletcher AM, Smith GM, Seroogy KB, Ziady AG, Molter J, Kowalczyk TH, Padegimas L, and Cooper MJ
- Subjects
- Animals, Base Sequence, DNA genetics, DNA Primers, Immunohistochemistry, In Situ Hybridization, Luciferases genetics, Plasmids, Rats, Transduction, Genetic, Brain metabolism, DNA administration & dosage, Nanoparticles, Transgenes
- Abstract
This study demonstrates proof of concept for delivery and expression of compacted plasmid DNA in the central nervous system. Plasmid DNA was compacted with polyethylene glycol substituted lysine 30-mer peptides, forming rod-like nanoparticles with diameters between 8 and 11 nm. Here we show that an intracerebral injection of compacted DNA can transfect both neurons and glia, and can produce transgene expression in the striatum for up to 8 weeks, which was at least 100-fold greater than intracerebral injections of naked DNA plasmids. Bioluminescent imaging (BLI) of injected animals at the 11th postinjection week revealed significantly higher transgene activity in animals receiving compacted DNA plasmids when compared to animals receiving naked DNA. There was minimal evidence of brain inflammation. Intrastriatal injections of a compacted plasmid encoding for glial cell line-derived neurotrophic factor (pGDNF) resulted in a significant overexpression of GDNF protein in the striatum 1-3 weeks after injection.
- Published
- 2009
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89. Detection of metastatic head and neck squamous cell carcinoma using the relative expression of tissue-specific mir-205.
- Author
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Fletcher AM, Heaford AC, and Trask DK
- Abstract
The presence of cervical lymph node metastases in head and neck squamous cell carcinoma (HNSCC) is the strongest determinant of patient prognosis. Owing to the impact of nodal metastases on patient survival, a system for sensitive and accurate detection is required. Clinical staging of lymph nodes is far less accurate than pathological staging. Pathological staging also suffers limitations because it fails to detect micrometastasis in a subset of nodal specimens. To improve the sensitivity of existing means of diagnosing metastatic disease, many advocate the use of molecular markers specific for HNSCC cells. MicroRNA (miRNA) are short noncoding segments of RNA that posttranscriptionally regulate gene expression. Approximately one third of all miRNA will exhibit substantial tissue specificity. Using a quantitative reverse transcription-polymerase chain reaction-based assay, we examined the expression of microRNA-205 (mir-205) across tissues and demonstrated that its expression is highly specific for squamous epithelium. We applied this assay to tissue samples, and we could detect metastatic HNSCC in each positive lymph node specimen, whereas benign specimens did not express this marker. When compared to metastases from other primary tumors, HNSCC-positive lymph nodes were distinguishable by the high expression of this marker. Using an in vitro lymphoid tissue model, we were able to detect as little as one squamous cell in a background of 1 million lymphocytes. By combining the sensitivity of quantitative reverse transcription-polymerase chain reaction with the specificity of mir-205 for squamous epithelium, we demonstrate a novel molecular marker for the detection of metastatic HNSCC.
- Published
- 2008
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90. Biotransformation of [14C]dasatinib: in vitro studies in rat, monkey, and human and disposition after administration to rats and monkeys.
- Author
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Christopher LJ, Cui D, Li W, Barros A Jr, Arora VK, Zhang H, Wang L, Zhang D, Manning JA, He K, Fletcher AM, Ogan M, Lago M, Bonacorsi SJ, Humphreys WG, and Iyer RA
- Subjects
- Animals, Area Under Curve, Biotransformation, Dasatinib, Hepatocytes metabolism, Humans, Macaca fascicularis, Magnetic Resonance Spectroscopy, Male, Microsomes, Liver metabolism, Protein Kinase Inhibitors administration & dosage, Protein Kinase Inhibitors blood, Pyrimidines administration & dosage, Pyrimidines blood, Rats, Rats, Sprague-Dawley, Thiazoles administration & dosage, Thiazoles blood, Carbon Radioisotopes metabolism, Protein Kinase Inhibitors pharmacokinetics, Pyrimidines pharmacokinetics, Thiazoles pharmacokinetics
- Abstract
This study describes the in vitro metabolism of [(14)C]dasatinib in liver tissue incubations from rat, monkey, and human and the in vivo metabolism in rat and monkey. Across species, dasatinib underwent in vitro oxidative metabolism to form five primary oxidative metabolites. In addition to the primary metabolites, secondary metabolites formed from combinations of the oxidative pathways and conjugated metabolites of dasatinib and its oxidative metabolites were also observed in hepatocytes incubations. In in vivo studies in rats and monkeys, the majority of the radioactive dose was excreted in the bile and feces. In bile duct-cannulated monkeys after an i.v. dose, 13.7% of the radioactive dose was excreted in the feces through direct secretion. Dasatinib comprised 56 and 26% of the area under the curve (AUC) (0-8 h) of total radioactivity (TRA) in plasma, whereas multiple metabolites accounted for the remaining 44 and 74% of the AUC (0-8 h) of TRA for rats and monkeys, respectively. In rat and monkey bile, dasatinib accounted for < 12% of the excreted dose, suggesting that dasatinib was extensively metabolized before elimination. The metabolic profiles in bile were similar to the hepatocyte profiles. In both species, a large portion of the radioactivity excreted in bile (> or = 29% of the dose) was attributed to N-oxides and conjugated metabolites. In rat and monkey feces, only the oxidative metabolites and their further oxidation products were identified. The absence of conjugative or N-oxide metabolites in the feces suggests hydrolysis or reduction, respectively, in the gastrointestinal tract before elimination.
- Published
- 2008
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91. Atrioventricular valvular angiectasis in Sprague-Dawley rats.
- Author
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Fang H, Howroyd PC, Fletcher AM, Diters RW, Woicke J, Sasseville VG, Bregman CL, Freebern WJ, Durham SK, and Mense MG
- Subjects
- Animals, Female, Heart Valve Diseases pathology, Male, Rats, Rats, Sprague-Dawley, Vascular Diseases pathology, Heart Valve Diseases veterinary, Rodent Diseases pathology, Vascular Diseases veterinary
- Abstract
Subendothelial heart valve angiectasis has been reported in cows, dogs, pigs, rats, mice, and in human fetuses and newborns. We observed a high incidence (62 in 208 animals examined) of spontaneous angiectasis on the atrioventricular (AV) valves in 10- to 40-week-old Sprague-Dawley rats. The angiectasis was observed predominately on the septal cusp of the right AV valve and located near the AV ostium in 57 of 62 animals. Of the remaining 5 valvular angiectases, 2 were present on the parietal cusp of the right AV valve and 3 were on the left AV valve. The angiectases were single or multiple, ranging from 40 to 300 microm in diameter and were characterized by light microscopy as blood-filled dilatations lined by endothelium. Spontaneously occurring abnormalities in normal laboratory animals, such as the spontaneous valvular angiectasis reported here, need to be differentiated from drug-related lesions.
- Published
- 2007
- Full Text
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92. Downscatter correction and choice of collimator in 123I imaging.
- Author
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Small AD, Prosser J, Motherwell DW, McCurrach GM, Fletcher AM, and Martin W
- Subjects
- Humans, Photons, Radiometry instrumentation, Radiotherapy Dosage, Radiotherapy Planning, Computer-Assisted instrumentation, Scattering, Radiation, Sensitivity and Specificity, Iodine Radioisotopes, Phantoms, Imaging, Radiometry methods, Radiotherapy Planning, Computer-Assisted methods
- Abstract
(123)I imaging is increasingly used in nuclear medicine but downscatter from high (>300 keV) energy emissions degrades the image and introduces variation in sensitivity with depth when imaging with a low energy collimator. A dual windowing technique using a matched window immediately above the principle window to correct for the effects of downscatter is described. The technique is shown to correct for the variation in sensitivity with depth and to reduce outlying scatter. Quantitative imaging of (123)I using a low energy collimator should always employ downscatter correction.
- Published
- 2006
- Full Text
- View/download PDF
93. Predictors of early leaving from the cotton spinning mill environment in newly hired workers.
- Author
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Bakirci N, Kalaca S, Fletcher AM, Pickering CA, Tumerdem N, Cali S, Oldham L, Francis H, and McL Niven R
- Subjects
- Adolescent, Adult, Cotton Fiber, Dust analysis, Environmental Monitoring methods, Epidemiologic Methods, Epidemiological Monitoring, Female, Healthy Worker Effect, Humans, Male, Occupational Exposure analysis, Occupational Health, Respiratory Function Tests, Skin Tests, Turkey, Occupational Diseases etiology, Personnel Turnover statistics & numerical data, Respiration Disorders etiology, Textile Industry statistics & numerical data
- Abstract
Objective: This longitudinal study aimed to identify the predictors of leaving during the first year of employment from the cotton spinning mill environment in newly hired workers., Methods: One hundred and ninety eight consecutively appointed new employees were investigated by questionnaire, lung function test, and skin test. They were examined before employment and at the end of the 1st week, and the 1st, 3rd, 6th, and 12th month after starting work and when possible before leaving their job. 572 personal dust sampling and 191 endotoxin measurements were performed to assess the environmental exposure. For the univariate analysis chi2, Student t tests, ANOVA, and Kruskall Wallis tests were used. Cox proportional hazards analysis was used to identify factors associated with leaving the job., Results: Fifty three per cent of workers left the mill environment during their first working year. Work related lower respiratory tract symptoms reported at the third month were associated with an increase rate of leaving the industry compared to those remaining in the industry (25% v 4.8%; p<0.005). Having respiratory symptoms at the first month of work predicted those leaving the industry at some point in the next 11 months. According to the Cox model, increasing age and having work related lower respiratory tract symptoms were found to be predictors for leaving job at the first working year. Atopic status, dust and endotoxin levels, and lung function changes were not consistently predictive of workers who left the industry in the follow up period., Conclusion: This study demonstrated that work related respiratory symptoms can predict workers likely to leave the cotton mill environment during the first year of employment, but atopy or acute lung function changes do not.
- Published
- 2006
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94. Endotoxin exposure in asthmatic children and matched healthy controls: results of IPEADAM study.
- Author
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Tavernier GO, Fletcher GD, Francis HC, Oldham LA, Fletcher AM, Blacklock G, Stewart L, Gee I, Watson A, Frank TL, Frank P, Pickering CA, and Niven RM
- Subjects
- Adolescent, Asthma epidemiology, Case-Control Studies, Child, Child, Preschool, England epidemiology, Female, Humans, Male, Primary Health Care statistics & numerical data, Risk Factors, Urban Population, Air Pollution, Indoor adverse effects, Asthma etiology, Endotoxins adverse effects, Environmental Exposure
- Abstract
Unlabelled: Children spend increasing time indoors. Exposure to environmental factors may contribute to the development or exacerbation of the asthmatic phenotype. Inter-relationships between these factors might influence the manifestation of asthma. Endotoxin exposure has been shown to have pro-inflammatory and protective effects in different situations. We investigated the exposure to several indoor pollutants (endotoxin, Der p 1, damp, ETS, PM2.5) in asthmatic and healthy children. The children were recruited from two primary care centers according to their response to a validated questionnaire. Asthmatic children were matched for sex, age and sib-ship size with children living in asthma free households. Of 90 matched pairs, higher levels of endotoxin were found in the living room carpets, but not the bedroom carpet or mattresses of the asthma compared with the control homes (STATA analysis OR: 1.88 (1.11-3.18); P=0.018). Asthmatic children were also more likely to live as part of a single parent family, in a house where the parents self-reported the presence of damp, and where the living room had been redecorated in the 12 months prior to the sampling visits. This study suggests that endotoxin in urban homes is a risk factor for the development of asthma. Moreover, this study found that there were no statistically significant interactions between environmental factors., Practical Implications: This study has demonstrated that the home environments of English children (4-17) with asthma and without the disease do not differ greatly. With the exception of endotoxin, the parameters examined in this study, including house dust mite allergens, nitrogen dioxide, ETS and damp are unlikely to be related to the development of asthma. Avoidance of these pollutants may not be beneficial in preventing asthma in this age group.
- Published
- 2005
- Full Text
- View/download PDF
95. Multiphonon vibrations at high angular momentum in 182 Os.
- Author
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Pattison LK, Cullen DM, Smith JF, Fletcher AM, Walker PM, El-Masri HM, Podolyák Z, Wood RJ, Scholey C, Wheldon C, Mukherjee G, Balabanski D, Djongolov M, Dalsgaard T, Thisgaard H, Sletten G, Kondev F, Jenkins D, Lane GJ, Lee IY, Macchiavelli AO, Frauendorf S, and Almehed D
- Abstract
Evidence is presented for multiphonon excitations based on a high-spin (25 Planck) intrinsic state in the deformed nucleus 182 Os. Angular momentum generation by this mode competes with collective rotation. The experimental data are compared with tilted-axis cranking calculations, supporting the vibrational interpretation. However, the lower experimental energies provide evidence that more complex interactions of states are playing a role.
- Published
- 2003
- Full Text
- View/download PDF
96. Renewed hope for self-change.
- Author
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Fletcher AM
- Subjects
- Body Weight, Defense Mechanisms, Humans, Social Behavior, Attitude, Diet psychology, Self Concept
- Published
- 2003
- Full Text
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97. Monocyte CD14 response following endotoxin exposure in cotton spinners and office workers.
- Author
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Fishwick D, Raza SN, Beckett P, Swan JR, Pickering CA, Fletcher AM, Niven RM, Francis H, Rawbone R, and Curran AD
- Subjects
- Adult, Biomarkers, CD4-Positive T-Lymphocytes metabolism, Cell Separation, Endotoxins adverse effects, Female, Flow Cytometry, Gossypium adverse effects, Humans, Male, Occupational Exposure, Receptors, Interleukin-2 metabolism, Time Factors, Up-Regulation physiology, Dust, Endotoxins metabolism, Gossypium metabolism, Lipopolysaccharide Receptors metabolism, Lipopolysaccharides metabolism, Monocytes metabolism, Textile Industry
- Abstract
Background: Monocyte cell surface CD14 acts as the major lipopolysaccharide (LPS) binding structure, and as such is of interest in the etiology of LPS induced disease., Methods: The objective was to assess change in monocyte cell surface CD14 and CD4+ CD25+ lymphocytes in a group of cotton workers exposed to LPS over a working week, and to compare this to changes in office workers. Twenty-five cotton workers and nine office workers were studied. Monocyte CD14 fluorescence was measured by flow cytometry, on samples taken pre-shift on a Monday morning (baseline/pre-exposure), and subsequently after 6 and 72 hr. The majority of cotton workers were exposed to at least 1 EU/m(3) of endotoxin over a working shift, and some highly exposed (between 100 and 400 EU/m(3))., Results: After 6 hr of work in the mill, cotton workers developed a significant upregulation in CD14 in comparison to office workers (P = 0.016), whereas CD14 expression had returned to levels not significantly differing from the office workers at 72 hr after first work exposure (P = 0.426)., Conclusions: We propose that CD14 expression on monocytes may help to determine the mechanism of action of lipopolysaccharide in producing respiratory ill health, and may ultimately play a role in monitoring the health effect associated with LPS exposure in the workplace.
- Published
- 2002
- Full Text
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98. MR imaging assessment of myelination in the very preterm brain.
- Author
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Counsell SJ, Maalouf EF, Fletcher AM, Duggan P, Battin M, Lewis HJ, Herlihy AH, Edwards AD, Bydder GM, and Rutherford MA
- Subjects
- Female, Gestational Age, Humans, Infant, Newborn, Male, Periaqueductal Gray ultrastructure, Retrospective Studies, Brain ultrastructure, Infant, Premature, Magnetic Resonance Imaging methods, Myelin Sheath ultrastructure
- Abstract
Background and Purpose: MR imaging was performed in very preterm infants by using an MR imager in the neonatal intensive care unit. The aims of this study were to assess the development of myelination in the preterm brain based on MR imaging findings and to compare the ability of T1-weighted conventional spin-echo, inversion recovery fast spin-echo, and T2-weighted fast spin-echo MR imaging to show myelination in these infants., Methods: MR imaging was performed for 26 preterm infants with a median gestational age of 28 weeks who had normal neurodevelopmental outcomes at 2 years corrected age., Results: Myelin was evident in the gracile and cuneate nuclei and fasciculi, vestibular nuclei, cerebellar vermis, inferior and superior cerebellar peduncles, dentate nucleus, medial longitudinal fasciculus, medial geniculate bodies, subthalamic nuclei, inferior olivary nuclei, ventrolateral nuclei of the thalamus, decussation of the superior cerebellar peduncles, medial lemnisci, lateral lemnisci, and inferior colliculi at < or = 28 weeks gestational age. From this gestational age, myelination was not visualized at any new site until 36 weeks gestational age, when myelin was visualized in the corona radiata, posterior limb of the internal capsule, corticospinal tracts of the precentral and postcentral gyri, and lateral geniculate bodies. T2-weighted fast spin-echo MR imaging showed myelin in gray matter nuclei at an earlier gestational age than did T1-weighted conventional spin-echo or inversion recovery fast spin-echo MR imaging. T1-weighted conventional spin-echo MR imaging showed myelin earlier in some white matter tracts in the preterm brain., Conclusion: Myelination was evident in numerous gray and white matter structures in the very preterm brain. A knowledge of myelination milestones will allow delays to be detected at an early stage.
- Published
- 2002
99. Loss of presenilin 1 is associated with enhanced beta-catenin signaling and skin tumorigenesis.
- Author
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Xia X, Qian S, Soriano S, Wu Y, Fletcher AM, Wang XJ, Koo EH, Wu X, and Zheng H
- Subjects
- Animals, Cells, Cultured, Cyclin D1 metabolism, Cytosol metabolism, G1 Phase, Humans, Keratinocytes cytology, Keratinocytes metabolism, Lymphoid Enhancer-Binding Factor 1, Membrane Proteins genetics, Mice, Mice, Knockout, Presenilin-1, S Phase, Skin Neoplasms pathology, beta Catenin, Cytoskeletal Proteins metabolism, DNA-Binding Proteins metabolism, Membrane Proteins physiology, Signal Transduction, Skin Neoplasms metabolism, Trans-Activators, Transcription Factors metabolism
- Abstract
Presenilin 1 (PS1) is required for the proteolytic processing of Notch and the beta-amyloid precursor protein (APP), molecules that play pivotal roles in cell-fate determination during development and Alzheimer's disease pathogenesis, respectively. In addition, PS1 interacts with beta-catenin and promotes its turnover through independent mechanisms. Consistent with this activity, we report here that PS1 is important in controlling epidermal cell proliferation in vivo. PS1 knockout mice that are rescued through neuronal expression of human PS1 transgene develop spontaneous skin cancers. PS1-null keratinocytes exhibit higher cytosolic beta-catenin and beta-catenin/lymphoid enhancer factor-1/T cell factor (beta-catenin/LEF)-mediated signaling. This effect can be reversed by reintroducing wild-type PS1, but not a PS1 mutant active in Notch processing but defective in beta-catenin binding. Nuclear beta-catenin protein can be detected in tumors. Elevated beta-catenin/LEF signaling is correlated with activation of its downstream target cyclin D1 and accelerated entry from G(1) into S phase of the cell cycle. This report demonstrates a function of PS1 in adult tissues, and our analysis suggests that deregulation of beta-catenin pathway contributes to the skin tumor phenotype.
- Published
- 2001
- Full Text
- View/download PDF
100. Alteration of Cx43:Cx40 expression ratio in A7r5 cells.
- Author
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Burt JM, Fletcher AM, Steele TD, Wu Y, Cottrell GT, and Kurjiaka DT
- Subjects
- Antisense Elements (Genetics) pharmacology, Cell Communication physiology, Cell Line, Connexin 43 genetics, Connexins genetics, Electrophysiology, Gap Junctions metabolism, Gap Junctions physiology, Ion Channels metabolism, Muscle, Smooth, Vascular cytology, Muscle, Smooth, Vascular physiology, RNA, Messenger genetics, Gap Junction alpha-5 Protein, Connexin 43 metabolism, Connexins metabolism, Muscle, Smooth, Vascular metabolism
- Abstract
Connexins (Cx) 40 and 43 are coexpressed by several cell types at ratios that vary as a function of development, aging, and disease. Because these connexins form heteromeric channels, changes in expression ratio might be expected to significantly alter the connexin composition of the gap junction channel population and, therefore, gap junction function. To examine this possibility, we stably transfected A7r5 cells, which naturally coexpress Cx43 and Cx40, with a vector encoding antisense Cx43. Cx43 mRNA continued to be expressed in the antisense transfected clones, although levels were inversely related to the number of copies of antisense DNA incorporated into the genome. Protein levels, quantified in the clones with the highest and lowest Cx43:Cx40 mRNA ratios, were not well predicted by the mRNA levels, although the trends predicted by the Cx43:Cx40 mRNA ratio were preserved. Electrical coupling did not differ significantly between clones, but the clone with elevated Cx43:Cx40 protein expression ratio and unchanged Cx43 banding pattern was significantly better dye coupled than the parental A7r5 cells. These results suggest that as the Cx43:Cx40 ratio increases, provided alterations of Cx43 banding pattern (phosphorylation) have not occurred, permeability to large molecules increases even though electrical coupling remains nearly constant.
- Published
- 2001
- Full Text
- View/download PDF
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