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Marriott AE, Dagley JL, Hegde S, Steven A, Fricks C, DiCosty U, Mansour A, Campbell EJ, Wilson CM, Gusovsky F, Ward SA, Hong WD, O'Neill P, Moorhead A, McCall S, McCall JW, Taylor MJ, Turner JD. Dirofilariasis mouse models for heartworm preclinical research. Front Microbiol 2023; 14:1208301. [PMID: 37426014 PMCID: PMC10324412 DOI: 10.3389/fmicb.2023.1208301] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Accepted: 05/30/2023] [Indexed: 07/11/2023] Open
Abstract
Introduction Dirofilariasis, including heartworm disease, is a major emergent veterinary parasitic infection and a human zoonosis. Currently, experimental infections of cats and dogs are used in veterinary heartworm preclinical drug research. Methods As a refined alternative in vivo heartworm preventative drug screen, we assessed lymphopenic mouse strains with ablation of the interleukin-2/7 common gamma chain (γc) as susceptible to the larval development phase of Dirofilaria immitis. Results Non-obese diabetic (NOD) severe combined immunodeficiency (SCID)γc-/- (NSG and NXG) and recombination-activating gene (RAG)2-/-γc-/- mouse strains yielded viable D. immitis larvae at 2-4 weeks post-infection, including the use of different batches of D. immitis infectious larvae, different D. immitis isolates, and at different laboratories. Mice did not display any clinical signs associated with infection for up to 4 weeks. Developing larvae were found in subcutaneous and muscle fascia tissues, which is the natural site of this stage of heartworm in dogs. Compared with in vitro-propagated larvae at day 14, in vivo-derived larvae had completed the L4 molt, were significantly larger, and contained expanded Wolbachia endobacteria titres. We established an ex vivo L4 paralytic screening system whereby assays with moxidectin or levamisole highlighted discrepancies in relative drug sensitivities in comparison with in vitro-reared L4 D. immitis. We demonstrated effective depletion of Wolbachia by 70%-90% in D. immitis L4 following 2- to 7-day oral in vivo exposures of NSG- or NXG-infected mice with doxycycline or the rapid-acting investigational drug, AWZ1066S. We validated NSG and NXG D. immitis mouse models as a filaricide screen by in vivo treatments with single injections of moxidectin, which mediated a 60%-88% reduction in L4 larvae at 14-28 days. Discussion Future adoption of these mouse models will benefit end-user laboratories conducting research and development of novel heartworm preventatives via increased access, rapid turnaround, and reduced costs and may simultaneously decrease the need for experimental cat or dog use.
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Affiliation(s)
- A. E. Marriott
- Department of Tropical Disease Biology, Centre for Drugs and Diagnostics, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom
| | - J. L. Dagley
- Department of Tropical Disease Biology, Centre for Drugs and Diagnostics, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom
| | - S. Hegde
- Department of Tropical Disease Biology, Centre for Drugs and Diagnostics, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom
| | - A. Steven
- Department of Tropical Disease Biology, Centre for Drugs and Diagnostics, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom
| | - C. Fricks
- TRS Laboratories Inc, Athens, GA, United States
| | - U. DiCosty
- TRS Laboratories Inc, Athens, GA, United States
| | - A. Mansour
- TRS Laboratories Inc, Athens, GA, United States
| | - E. J. Campbell
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA, United States
| | - C. M. Wilson
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA, United States
| | - F. Gusovsky
- Eisai Global Health, Cambridge, MA, United States
| | - S. A. Ward
- Department of Tropical Disease Biology, Centre for Drugs and Diagnostics, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom
| | - W. D. Hong
- Department of Chemistry, University of Liverpool, Liverpool, United Kingdom
| | - P. O'Neill
- Department of Chemistry, University of Liverpool, Liverpool, United Kingdom
| | - A. Moorhead
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA, United States
| | - S. McCall
- TRS Laboratories Inc, Athens, GA, United States
| | - J. W. McCall
- TRS Laboratories Inc, Athens, GA, United States
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA, United States
| | - M. J. Taylor
- Department of Tropical Disease Biology, Centre for Drugs and Diagnostics, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom
| | - J. D. Turner
- Department of Tropical Disease Biology, Centre for Drugs and Diagnostics, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom
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Saifuddin Ekram ARM, Espinoza SE, Ernst ME, Ryan J, Beilin L, Stocks NP, Ward SA, McNeil JJ, Shah RC, Woods RL. The Association between Metabolic Syndrome, Frailty and Disability-Free Survival in Healthy Community-dwelling Older Adults. J Nutr Health Aging 2023; 27:1-9. [PMID: 36651481 PMCID: PMC10061371 DOI: 10.1007/s12603-022-1860-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Accepted: 09/16/2022] [Indexed: 11/16/2022]
Abstract
OBJECTIVES To examine the association between metabolic syndrome (MetS) and frailty, and determine whether co-existent MetS and frailty affect disability-free survival (DFS), assessed through a composite of death, dementia or physical disability. DESIGN Longitudinal study. SETTING AND PARTICIPANTS Community-dwelling older adults from Australia and the United States (n=18,264) from "ASPirin in Reducing Events in the Elderly" (ASPREE) study. MEASUREMENTS MetS was defined according to American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines (2018). A modified Fried phenotype and a deficit accumulation Frailty Index (FI) were used to assess frailty. Association between MetS and frailty was examined using multinomial logistic regression. Cox regression was used to analyze the association between MetS, frailty and DFS over a median follow-up of 4.7 years. RESULTS Among 18,264 participants, 49.9% met the criteria for MetS at baseline. Participants with Mets were more likely to be pre-frail [Relative Risk Ratio (RRR): 1.22; 95%Confidence Interval (CI): 1.14, 1.30)] or frail (RRR: 1.66; 95%CI: 1.32, 2.08) than those without MetS. MetS alone did not shorten DFS while pre-frailty or frailty alone did [Hazard Ratio (HR): 1.68; 95%CI: 1.45, 1.94; HR: 2.65; 95%CI:1.92, 3.66, respectively]. Co-existent MetS with pre-frailty/frailty did not change the risk of shortened DFS. CONCLUSIONS MetS was associated with pre-frailty or frailty in community-dwelling older individuals. Pre-frailty or frailty increased the risk of reduced DFS but presence of MetS did not change this risk. Assessment of frailty may be more important than MetS in predicting survival free of dementia or physical disability.
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Affiliation(s)
- A R M Saifuddin Ekram
- Dr. A R M Saifuddin Ekram, Senior Clinical Research Consultant (ASPREE), SPHPM, Monash University, 553 St Kilda Road, Melbourne, Victoria 3004, Australia. Mobile phone: +61449031659, E-mail:
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Török ME, Aljayyoussi G, Waterhouse D, Chau T, Mai N, Phu NH, Hien TT, Hope W, Farrar JJ, Ward SA. Suboptimal Exposure to Anti-TB Drugs in a TBM/HIV+ Population Is Not Related to Antiretroviral Therapy. Clin Pharmacol Ther 2017; 103:449-457. [PMID: 28160272 DOI: 10.1002/cpt.646] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Revised: 01/24/2017] [Accepted: 01/29/2017] [Indexed: 11/08/2022]
Abstract
A placebo-controlled trial that compares the outcomes of immediate vs. deferred initiation of antiretroviral therapy in HIV +ve tuberculous meningitis (TBM) patients was conducted in Vietnam in 2011. Here, the pharmacokinetics of rifampicin, isoniazid, pyrazinamide, and ethambutol were investigated in the presence and absence of anti-HIV treatment in 85 patients. Pharmacokinetic analyses show that HIV therapy has no significant impact on the pharmacokinetics of TB drugs in this cohort. The same population, however, displayed generally low cerebrospinal fluid (CSF) and systemic exposures to rifampicin compared to previously reported HIV -ve cohorts. Elevated CSF concentrations of pyrazinamide, on the other hand, were strongly and independently correlated with increased mortality and neurological toxicity. The findings suggest that the current standard dosing regimens may put the patient at risk of treatment failure from suboptimal rifampicin exposure, and potentially increasing the risk of adverse central nervous system events that are independently correlated with pyrazinamide CSF exposure.
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Affiliation(s)
- M E Török
- University of Cambridge, Department of Medicine, Addenbrooke's Hospital, Cambridge, UK
| | - G Aljayyoussi
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, UK
| | - D Waterhouse
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, UK
| | - Tth Chau
- Oxford University Clinical Research Unit, Hospital for Tropical Diseases, Hi Chi Minh City, Vietnam
| | - Nth Mai
- Oxford University Clinical Research Unit, Hospital for Tropical Diseases, Hi Chi Minh City, Vietnam
| | - N H Phu
- Oxford University Clinical Research Unit, Hospital for Tropical Diseases, Hi Chi Minh City, Vietnam
| | - T T Hien
- Oxford University Clinical Research Unit, Hospital for Tropical Diseases, Hi Chi Minh City, Vietnam
| | - W Hope
- University of Liverpool, Liverpool, UK
| | - J J Farrar
- Oxford University Clinical Research Unit, Hospital for Tropical Diseases, Hi Chi Minh City, Vietnam
| | - S A Ward
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, UK
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Ahmed KM, Allam TM, El-sayed HA, Soliman HM, Ward SA, Saied EM. Design, Construction and Characterization of AC Atmospheric Pressure Air Non-thermal Plasma Jet. J Fusion Energ 2014. [DOI: 10.1007/s10894-014-9720-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Allam TM, Ward SA, El-sayed HA, Saied EM, Soliman HM, Ahmed KM. Electrical Parameters Investigation and Zero Flow Rate Effect of Nitrogen Atmospheric Nonthermal Plasma Jet. ACTA ACUST UNITED AC 2014. [DOI: 10.4236/epe.2014.612036] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Palange P, Casaburi R, Ward SA. Prof. Brian James Whipp, 1937-2011: a master in respiratory and exercise physiology. Eur Respir J 2011. [DOI: 10.1183/09031936.00189711] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Whipp BJ, Ward SA. The physiological basis of the 'anaerobic threshold' and implications for clinical cardiopulmonary exercise testing. Anaesthesia 2011; 66:1048-9; author reply 1049-50. [PMID: 22004202 DOI: 10.1111/j.1365-2044.2011.06909_1.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Abstract
Abstract
The binding of the novel antimalarial drug, arteether, to human plasma, pure albumin and α1-acid glycoprotein has been investigated by ultrafiltration, using [14C]arteether. The protein binding in plasma obtained from 11 healthy male subjects ranged from 73·4 to 81·8% bound, with a mean of 78·7 ± 2·1%. The binding of drug in plasma was mainly accounted for by binding to albumin and α1-acid glycoprotein. Scatchard analysis of the binding data revealed that the binding affinity of arteether to α1-acid glycoprotein is much greater (20-fold) than that to albumin. This suggests that α1-acid glycoprotein is the more important binding protein in plasma. This may have clinical importance due to alterations in plasma protein binding in patients with malaria, as the concentration of α1-acid glycoprotein is markedly increased during malarial infection.
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Affiliation(s)
- S Wanwimolruk
- Department of Pharmacology and Therapeutics, University of Liverpool, UK
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Bell DJ, Nyirongo SK, Mukaka M, Molyneux ME, Winstanley PA, Ward SA. Population pharmacokinetics of sulfadoxine and pyrimethamine in Malawian children with malaria. Clin Pharmacol Ther 2010; 89:268-75. [PMID: 21191379 DOI: 10.1038/clpt.2010.297] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
In addition to parasite resistance, inadequate levels of exposure to antimalarial drugs may contribute to treatment failure. We developed population pharmacokinetic (PK) models to describe the distribution of sulfadoxine (SDX) and pyrimethamine (PYM) in children with uncomplicated malaria in Malawi. The concentration levels of antimalarial drugs in whole blood were determined using high-performance liquid chromatography. We found no evidence of underdosing in children as compared with adults; the children had drug exposure levels similar to those described in adults. Treatment failure was more likely in children with lower PYM concentrations on day 14 (P = 0.024), and there was a trend for lower SDX concentrations on day 14 (P = 0.061). SDX and PYM concentrations at levels predictive of treatment failure have been identified at day 14. Less than one-third of the children displayed drug concentration levels above these thresholds after receiving the recommended SDX-pyrimethamine (SP) dose. Our findings suggest that PK factors contributed to the observed high rate of treatment failure, and we therefore recommend a higher SP dose for children under the age of 5 years.
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Affiliation(s)
- D J Bell
- Tropical and Infectious Diseases Unit, Royal Liverpool University Hospital, Liverpool, UK
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Ferguson C, Rossiter HB, Whipp BJ, Cathcart AJ, Murgatroyd SR, Ward SA. Effect of recovery duration from prior exhaustive exercise on the parameters of the power-duration relationship. J Appl Physiol (1985) 2010; 108:866-74. [DOI: 10.1152/japplphysiol.91425.2008] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The physiological equivalents of the curvature constant (W′) of the high-intensity power-duration (P-tLIM) relationship are poorly understood, although they are presumed to reach maxima/minima at exhaustion. In an attempt to improve our understanding of the determinants of W′, we therefore aimed to determine its recovery kinetics following exhaustive exercise (which depletes W′) concomitantly with those of O2 uptake (V̇o2, a proxy for the kinetics of phosphocreatine replenishment) and blood lactate concentration ([L−]). Six men performed cycle-ergometer exercise to tLIM: a ramp and four constant-load tests, at different work rates, for estimation of lactate threshold, W′, critical power (CP), and maximum V̇o2. Three further exhausting tests were performed at different work rates, each preceded by an exhausting “conditioning” bout, with intervening recoveries of 2, 6, and 15 min. Neither prior exhaustion nor recovery duration altered V̇o2 or [L−] at tLIM. Postconditioning, the P-tLIM relationship remained well characterized by a hyperbola, with CP unchanged. However, W′ recovered to 37 ± 5, 65 ± 6, and 86 ± 4% of control following 2, 6, and 15 min of intervening recovery, respectively. The W′ recovery was curvilinear [interpolated half time ( t1/2) = 234 ± 32 s] and appreciably slower than V̇o2 recovery ( t1/2 = 74 ± 2 s) but faster than [L−] recovery ( t1/2 = 1,366 ± 799 s). This suggests that W′ determines supra-CP exercise tolerance, its restitution kinetics are not a unique function of phosphocreatine concentration or arterial [L−], and it is unlikely to simply reflect a finite energy store that becomes depleted at tLIM.
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Affiliation(s)
- C. Ferguson
- Institute of Membrane and Systems Biology, Faculty of Biological Sciences, University of Leeds, Leeds; and
- Department of Integrative and Systems Biology, Faculty of Biomedical and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - H. B. Rossiter
- Institute of Membrane and Systems Biology, Faculty of Biological Sciences, University of Leeds, Leeds; and
| | - B. J. Whipp
- Institute of Membrane and Systems Biology, Faculty of Biological Sciences, University of Leeds, Leeds; and
| | - A. J. Cathcart
- Department of Integrative and Systems Biology, Faculty of Biomedical and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - S. R. Murgatroyd
- Institute of Membrane and Systems Biology, Faculty of Biological Sciences, University of Leeds, Leeds; and
| | - S. A. Ward
- Institute of Membrane and Systems Biology, Faculty of Biological Sciences, University of Leeds, Leeds; and
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Janneh O, Hartkoorn RC, Jones E, Owen A, Ward SA, Davey R, Back DJ, Khoo SH. Cultured CD4T cells and primary human lymphocytes express hOATPs: intracellular accumulation of saquinavir and lopinavir. Br J Pharmacol 2008; 155:875-83. [PMID: 19002102 DOI: 10.1038/bjp.2008.320] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
BACKGROUND AND PURPOSE Drug efflux tranporters (P-glycoprotein (P-gp), multidrug resistance-associated protein (MRP)) limit the cellular uptake of human immunodeficiency virus protease inhibitors but the contribution of influx transporters in cells that (over)express P-gp or MRP is less clear. Here, we studied the expression of one influx transporter system, human organic anion-transporting polypeptide (hOATP), in some T-cell lines (CEM, CEM(VBL), CEM(E1000)) and in peripheral blood mononuclear cells (PBMCs) and examined the effects of manipulation of influx/efflux transporters on the uptake of saquinavir and lopinavir. EXPERIMENTAL APPROACH The expression of hOATPs was studied by PCR. We used hOATP substrate or inhibitor (estrone-3-sulphate (E-3-S) or montelukast, respectively) and inhibitors of P-gp (XR9576) and MRP (MK571 and frusemide) to study functional interactions between influx and efflux transporters in the uptake of saquinavir and lopinavir. Lipophilicity of the drugs was measured by octanol/saline partition coefficient. KEY RESULTS CEM cells, their variants and PBMCs express various hOATP isoforms, with OATP3A1 detected in all of the cells. MK571, XR9576 and frusemide increased the uptake of saquinavir and lopinavir. E-3-S and montelukast reduced the uptake of saquinavir and lopinavir in some, but not all, of the cells. Pretreatment of the cells with MK571, XR9576 or frusemide, followed by E-3-S co-incubation reduced the cellular accumulation of saquinavir and lopinavir. Lopinavir is much more lipophilic than saquinavir. CONCLUSIONS AND IMPLICATIONS Human OATPs, MRP, P-gp and lipophilicity determine the cellular uptake and retention of saquinavir and lopinavir. These data may have important implications for drug-drug interactions, drug safety and efficacy.
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Affiliation(s)
- O Janneh
- School of Biomedical Sciences, University of Ulster, Coleraine, County Londonderry, UK.
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Ferguson C, Whipp BJ, Cathcart AJ, Rossiter HB, Turner AP, Ward SA. Effects of prior very-heavy intensity exercise on indices of aerobic function and high-intensity exercise tolerance. J Appl Physiol (1985) 2007; 103:812-22. [PMID: 17540836 DOI: 10.1152/japplphysiol.01410.2006] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
A recent bout of high-intensity exercise can alter the balance of aerobic and anaerobic energy provision during subsequent exercise above the lactate threshold (theta(L)). However, it remains uncertain whether such "priming" influences the tolerable duration of subsequent exercise through changes in the parameters of aerobic function [e.g., theta(L), maximum oxygen uptake (Vo(2max))] and/or the hyperbolic power-duration (P-t) relationship [critical power (CP) and the curvature constant (W')]. We therefore studied six men performing cycle ergometry to the limit of tolerance; gas exchange was measured breath-by-breath and arterialized capillary blood [lactate] was measured at designated intervals. On different days, each subject completed 1) an incremental test (15 W/min) for estimation of theta(L) and measurement of the functional gain (DeltaVo(2)/DeltaWR) and Vo(2peak) and 2) four constant-load tests at different work rates (WR) for estimation of CP, W', and Vo(2max). All tests were subsequently repeated with a preceding 6-min supra-CP priming bout and an intervening 2-min 20-W recovery. The hyperbolicity of the P-t relationship was retained postpriming, with no significant difference in CP (241 +/- 39 vs. 242 +/- 36 W, post- vs. prepriming), Vo(2max) (3.97 +/- 0.34 vs. 3.93 +/- 0.38 l/min), DeltaVo(2)/DeltaWR (10.7 +/- 0.3 vs. 11.1 +/- 0.4 ml.min(-1).W(-1)), or the fundamental Vo(2) time constant (25.6 +/- 3.5 vs. 28.3 +/- 5.4 s). W' (10.61 +/- 2.07 vs. 16.13 +/- 2.33 kJ) and the tolerable duration of supra-CP exercise (-33 +/- 11%) were each significantly reduced, despite a less-prominent Vo(2) slow component. These results suggest that, following supra-CP priming, there is either a reduced depletable energy resource or a residual fatigue-metabolite level that leads to the tolerable limit before this resource is fully depleted.
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Affiliation(s)
- C Ferguson
- Centre for Sport and Exercise Sciences, Institute of Membrane and Systems Biology, Worsley Bldg., Univ. of Leeds, Leeds, LS2 9JT, United Kingdom
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Palange P, Ward SA. From the authors. Eur Respir J 2007. [DOI: 10.1183/09031936.00029207] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Bell DJ, Nyirongo SK, Molyneux ME, Winstanley PA, Ward SA. Practical HPLC methods for the quantitative determination of common antimalarials in Africa. J Chromatogr B Analyt Technol Biomed Life Sci 2007; 847:231-6. [PMID: 17098484 DOI: 10.1016/j.jchromb.2006.10.020] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2006] [Revised: 10/05/2006] [Accepted: 10/09/2006] [Indexed: 11/22/2022]
Abstract
This article describes high-performance liquid chromatographic assays for the quantification of sulfadoxine (SDX), pyrimethamine (PYM), chloroquine (CQ), amodiaquine (AQ) and desethylamodiaquine (AQM) from whole blood. All four assays were set up and validated in Malawi using a common high-performance liquid chromatography platform and column and involved the use of simple mobile phase and extraction reagents. Calibration curves were linear (r(2)>0.95) in the ranges 5-100microg/ml, 50-1000, 150-1500, 100-1000 and 100-1000ng/ml for SDX, PYM, CQ, AQ and AQM, respectively. Intra-assay and inter-assay coefficients of variation were <15% at 3 points spanning the concentration range and <20% at the lower limit of quantification. The assays were specific with no interference from the other antimalarials described in this report. All four assays use liquid-liquid extraction, reversed-phase chromatography and UV detection and require between 50 and 200microl of blood. Because the assays share common instruments and reagents, they are cost-efficient and could be used to optimise antimalarial drug therapies in other resource poor settings.
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Affiliation(s)
- D J Bell
- Malawi-Liverpool-Wellcome Trust Clinical Research Programme, Blantyre, Malawi.
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Palange P, Ward SA, Carlsen KH, Casaburi R, Gallagher CG, Gosselink R, O'Donnell DE, Puente-Maestu L, Schols AM, Singh S, Whipp BJ. Recommendations on the use of exercise testing in clinical practice. Eur Respir J 2006; 29:185-209. [PMID: 17197484 DOI: 10.1183/09031936.00046906] [Citation(s) in RCA: 370] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Evidence-based recommendations on the clinical use of cardiopulmonary exercise testing (CPET) in lung and heart disease are presented, with reference to the assessment of exercise intolerance, prognostic assessment and the evaluation of therapeutic interventions (e.g. drugs, supplemental oxygen, exercise training). A commonly used grading system for recommendations in evidence-based guidelines was applied, with the grade of recommendation ranging from A, the highest, to D, the lowest. For symptom-limited incremental exercise, CPET indices, such as peak O(2) uptake (V'O(2)), V'O(2) at lactate threshold, the slope of the ventilation-CO(2) output relationship and the presence of arterial O(2) desaturation, have all been shown to have power in prognostic evaluation. In addition, for assessment of interventions, the tolerable duration of symptom-limited high-intensity constant-load exercise often provides greater sensitivity to discriminate change than the classical incremental test. Field-testing paradigms (e.g. timed and shuttle walking tests) also prove valuable. In turn, these considerations allow the resolution of practical questions that often confront the clinician, such as: 1) "When should an evaluation of exercise intolerance be sought?"; 2) "Which particular form of test should be asked for?"; and 3) "What cluster of variables should be selected when evaluating prognosis for a particular disease or the effect of a particular intervention?"
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Ward SA. Exercise testing needs to be comprehensive. Chron Respir Dis 2006; 3:109. [PMID: 16729770 DOI: 10.1191/1479972306cd108xx] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Affiliation(s)
- S A Ward
- Institute of Membrane and Systems Biology, University of Leeds, Leeds LS2 9JT, UK.
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Graham SM, Bell DJ, Nyirongo S, Hartkoorn R, Ward SA, Molyneux EM. Low levels of pyrazinamide and ethambutol in children with tuberculosis and impact of age, nutritional status, and human immunodeficiency virus infection. Antimicrob Agents Chemother 2006; 50:407-13. [PMID: 16436690 PMCID: PMC1366879 DOI: 10.1128/aac.50.2.407-413.2006] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Recent pharmacokinetic studies that included children found that serum drug levels were low compared to those of adults for whom the same dosages were used. This study aimed to characterize the pharmacokinetics of pyrazinamide and ethambutol in Malawian children and to examine the impact of age, nutritional status, and human immunodeficiency virus (HIV) infection. We conducted a pharmacokinetic study of children treated for tuberculosis with thrice-weekly pyrazinamide (n = 27; mean age, 5.7 years) and of a separate group of children treated with thrice-weekly ethambutol (n = 18; mean age, 5.5 years) as portions of tablets according to national guidelines. Malnutrition and HIV infection were common in both groups. Blood samples were taken just prior to oral administration of the first dose, and subsequent samples were taken at intervals of 2, 3, 4, 7, 24, and 48 h after drug administration. Serum drug levels were low in all children for both drugs; in almost all cases, the maximum concentration of the drug in serum (Cmax) failed to reach the MIC for Mycobacterium tuberculosis. The Cmax of pyrazinamide was significantly lower in younger children (<5 years) than in older children. The Cmax of pyrazinamide was also lower for HIV-infected children and children with severe malnutrition, but these differences did not reach statistical significance. No differences were found for ethambutol in relation to age, HIV infection, or malnutrition, but the Cmax was <2 mg/liter in all cases. Studies of pharmacokinetic parameters and clinical outcomes obtained by using higher dosages of drugs for treatment of childhood tuberculosis are needed, and recommended dosages may need to be increased.
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Affiliation(s)
- S M Graham
- Malawi-Liverpool-Wellcome Trust Clinical Research Programme, P.O. Box 30096, Blantyre 3, Malawi.
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21
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McGready R, Stepniewska K, Ward SA, Cho T, Gilveray G, Looareesuwan S, White NJ, Nosten F. Pharmacokinetics of dihydroartemisinin following oral artesunate treatment of pregnant women with acute uncomplicated falciparum malaria. Eur J Clin Pharmacol 2006; 62:367-71. [PMID: 16552504 DOI: 10.1007/s00228-006-0118-y] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2004] [Accepted: 02/10/2006] [Indexed: 11/24/2022]
Abstract
OBJECTIVE To determine the pharmacokinetic properties of dihydroartemisinin (DHA) following oral artesunate treatment in women with recrudescent multi-drug resistant falciparum malaria, in the second and third trimesters of pregnancy. METHODS Serial plasma concentrations of artesunate and DHA were measured in 24 women after the final dose of a 3 day treatment with artesunate (4 mg kg(-1) day(-1)) and atovaquone (20 mg kg(-1) day(-1)) plus proguanil (8 mg kg(-1) day(-1)), daily. Conventional non-compartmental modelling and a population one-compartment pharmacokinetic model were applied to the data. RESULTS Artesunate was very rapidly eliminated. For DHA the median [90% range] estimate of oral clearance (CI/F) was 4.0 [0.8-20.7] l hour(-1) kg(-1), total apparent volume of distribution (Vd/f) was 3.4 [0.9-60.7] l/kg, and terminal elimination half-life was 1.0 [0.6-2.4] h. CONCLUSION The kinetics of DHA are modified by pregnancy. The plasma levels of the active antimalarial metabolite DHA are lower than reported previously in non-pregnant adults. Dose-optimisation studies in pregnant women are needed.
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MESH Headings
- Acute Disease
- Adolescent
- Adult
- Analysis of Variance
- Antimalarials/administration & dosage
- Antimalarials/pharmacokinetics
- Antimalarials/therapeutic use
- Artemisinins/administration & dosage
- Artemisinins/pharmacokinetics
- Artemisinins/therapeutic use
- Artesunate
- Atovaquone/administration & dosage
- Atovaquone/pharmacokinetics
- Atovaquone/therapeutic use
- Drug Combinations
- Drug Resistance, Multiple
- Drug Therapy, Combination
- Female
- Half-Life
- Humans
- Malaria, Falciparum/blood
- Malaria, Falciparum/drug therapy
- Malaria, Falciparum/metabolism
- Pregnancy
- Pregnancy Complications, Parasitic/blood
- Pregnancy Complications, Parasitic/drug therapy
- Pregnancy Complications, Parasitic/metabolism
- Pregnancy Outcome
- Pregnancy Trimester, Second
- Pregnancy Trimester, Third
- Proguanil/administration & dosage
- Proguanil/pharmacokinetics
- Proguanil/therapeutic use
- Sesquiterpenes/administration & dosage
- Sesquiterpenes/pharmacokinetics
- Sesquiterpenes/therapeutic use
- Thailand
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Affiliation(s)
- R McGready
- Shoklo Malaria Research Unit, P.O. Box 46, Mae Sot, Thailand
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22
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Abstract
Plasmodium falciparum is the most important parasitic pathogen in humans, causing hundreds of millions of malaria infections and millions of deaths each year. At present there is no effective malaria vaccine and malaria therapy is totally reliant on the use of drugs. New drugs are urgently needed because of the rapid evolution and spread of parasite resistance to the current therapies. Drug resistance is one of the major factors contributing to the resurgence of malaria, especially resistance to the most affordable drugs such as chloroquine. We need to fully understand the antimalarial mode of action of the existing drugs and the way that the parasite becomes resistant to them in order to design and develop the new therapies that are so urgently needed. In respect of the quinolines and artemisinins, great progress has been made recently in studying the mechanisms of drug action and drug resistance in malaria parasites. Here we summarize from a historical, biological and chemical, perspective the exciting new advances that have been made in the study of these important antimalarial drugs.
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Affiliation(s)
- P G Bray
- Division of Molecular and Biochemical Parasitology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK.
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23
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Fuld JP, Kilduff LP, Neder JA, Pitsiladis Y, Lean MEJ, Ward SA, Cotton MM. Creatine supplementation during pulmonary rehabilitation in chronic obstructive pulmonary disease. Thorax 2005; 60:531-7. [PMID: 15994258 PMCID: PMC1747450 DOI: 10.1136/thx.2004.030452] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
BACKGROUND Skeletal muscle wasting and dysfunction are strong independent predictors of mortality in patients with chronic obstructive pulmonary disease (COPD). Creatine nutritional supplementation produces increased muscle mass and exercise performance in health. A controlled study was performed to look for similar effects in 38 patients with COPD. METHODS Thirty eight patients with COPD (mean (SD) forced expiratory volume in 1 second (FEV(1)) 46 (15)% predicted) were randomised to receive placebo (glucose polymer 40.7 g) or creatine (creatine monohydrate 5.7 g, glucose 35 g) supplements in a double blind trial. After 2 weeks loading (one dose three times daily), patients participated in an outpatient pulmonary rehabilitation programme combined with maintenance (once daily) supplementation. Pulmonary function, body composition, and exercise performance (peripheral muscle strength and endurance, shuttle walking, cycle ergometry) took place at baseline (n = 38), post loading (n = 36), and post rehabilitation (n = 25). RESULTS No difference was found in whole body exercise performance between the groups: for example, incremental shuttle walk distance mean -23.1 m (95% CI -71.7 to 25.5) post loading and -21.5 m (95% CI -90.6 to 47.7) post rehabilitation. Creatine increased fat-free mass by 1.09 kg (95% CI 0.43 to 1.74) post loading and 1.62 kg (95% CI 0.47 to 2.77) post rehabilitation. Peripheral muscle performance improved: knee extensor strength 4.2 N.m (95% CI 1.4 to 7.1) and endurance 411.1 J (95% CI 129.9 to 692.4) post loading, knee extensor strength 7.3 N.m (95% CI 0.69 to 13.92) and endurance 854.3 J (95% CI 131.3 to 1577.4) post rehabilitation. Creatine improved health status between baseline and post rehabilitation (St George's Respiratory Questionnaire total score -7.7 (95% CI -14.9 to -0.5)). CONCLUSIONS Creatine supplementation led to increases in fat-free mass, peripheral muscle strength and endurance, health status, but not exercise capacity. Creatine may constitute a new ergogenic treatment in COPD.
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Affiliation(s)
- J P Fuld
- Centre for Excercise Science and Medicine, Institute of Biological and Life Sciences, University of Glasgow, Glasgow, UK.
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24
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Abstract
The aryl-biguanides proguanil and chlorproguanil were developed as part of a collaborative programme between ICI and the Liverpool School of Tropical Medicine during the 1940s. The compounds were characterized by their absence of host toxicity. However, the rapid development of parasite resistance to the actions of these drugs and the development of the 4-aminoquinoline, chloroquine, severely limited their use. The subsequent widespread development of parasite resistance to chloroquine, together with the observations that the magnitude of dihydrofolate reductase inhibitor resistance (the site of action of the biguanides) developed to pyrimethamine is not directly correlated with biguanide resistance(1,2). has resulted in renewed interest in these drugs. In particular, proguanil is now the drug of choice for malaria prophylaxis, in combination with chloroquine; used in combination with a suitable sulphonamide, it may be of value in malaria therapy.
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Affiliation(s)
- N A Helsby
- Department of Pharmacology and Therapeutics, University of Liverpool, New Medical Building, Ashton Street, PO Box 147, Liverpool L69 3BX, UK
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25
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Cathcart AJ, Herrold N, Turner AP, Wilson J, Ward SA. Absence of long-term modulation of ventilation by dead-space loading during moderate exercise in humans. Eur J Appl Physiol 2004; 93:411-20. [PMID: 15490221 DOI: 10.1007/s00421-004-1218-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/23/2004] [Indexed: 10/26/2022]
Abstract
The stability of arterial PCO(2) (P(a)CO(2)) during moderate exercise in humans suggests a CO(2)-linked control that matches ventilation (V(E)) to pulmonary CO(2) clearance (VCO(2)). An alternative view is that V(E) is subject to long-term modulation (LTM) induced by "hyperpnoeic history". LTM has been reported with associative conditioning via dead-space (V(D)) loading in exercising goats (Martin and Mitchell 1993). Whether this prevails in humans is less clear, which may reflect differences in study design (e.g. subject familiarisation; V(D) load; whether or not V(E) is expressed relative to VCO(2); choice of P(a)CO(2) estimator). After familiarisation, nine healthy males performed moderate constant-load cycle-ergometry (20 W-80 W-20 W; <lactate threshold, theta;(L)): day 1, pre-conditioning, n=3; day 2, conditioning (V(D)=1.59 l, doubling V(E) at 20 W and 80 W), n=8 with 10 min rest between tests; and, after 1 h rest, post-conditioning, n=3. Gas exchange was determined breath-by-breath. Post-conditioning, neither the transient [phase 1, phase 2 (capital EF, Cyrillic1, capital EF, Cyrillic2)] nor steady-state V(E) exercise responses, nor their proportionality to VCO(2), differed from pre-conditioning. For post-conditioning trial 1, steady-state V(E) was 28.1 (4.7) l min(-1) versus 29.1 (3.8) l min(-1) pre-conditioning, and mean-alveolar PCO(2) (a validated P(a)CO(2) estimator) was 5.53 (0.48) kPa [41.5 (3.6) mmHg] versus 5.59 (0.49) kPa [41.9 (3.7) mmHg]; the capital EF, Cyrillic1 V(E) increment was 4.2 (2.9) l min(-1) versus 5.2 (1.9) l min(-1); the capital EF, Cyrillic2 V(E) time-constant (tau) was 64.4 (24.1) s versus 64.1 (25.3) s; tauV(E)/tauVCO(2) was 1.12 (0.04) versus 1.10 (0.04); and the V(E)-VCO(2) slope was 21.7 (3.4) versus 21.2 (3.2). In conclusion, we could find no evidence to support ventilatory control during moderate exercise being influenced by hyperpnoeic history associated with dead-space loading in humans.
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Affiliation(s)
- A J Cathcart
- School of Sport and Exercise Sciences, University of Leeds, Leeds, LS2 9JT, UK
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26
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Alloueche A, Bailey W, Barton S, Bwika J, Chimpeni P, Falade CO, Fehintola FA, Horton J, Jaffar S, Kanyok T, Kremsner PG, Kublin JG, Lang T, Missinou MA, Mkandala C, Oduola AMJ, Premji Z, Robertson L, Sowunmi A, Ward SA, Winstanley PA. Comparison of chlorproguanil-dapsone with sulfadoxine-pyrimethamine for the treatment of uncomplicated falciparum malaria in young African children: double-blind randomised controlled trial. Lancet 2004; 363:1843-8. [PMID: 15183620 DOI: 10.1016/s0140-6736(04)16350-2] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
BACKGROUND Increasing resistance to sulfadoxine-pyrimethamine is leading to a decline in its effectiveness. We aimed to assess the safety profile of chlorproguanil-dapsone (CD), and to compare the safety and efficacy of this drug with that of sulfadoxine-pyrimethamine (SP) as treatment for uncomplicated falciparum malaria. METHODS We undertook a double-blind, randomised trial in 1850 consecutively recruited children with uncomplicated falciparum malaria, pooling data from five African countries. Analyses were based on all randomised patients with available data. FINDINGS CD was significantly more efficacious than SP (odds ratio 3.1 [95% CI 2.0-4.8]); 1313 patients (96%) given CD and 306 (89%) given SP achieved acceptable clinical and parasitological response by day 14. Adverse events were reported in 46% and 50% of patients randomised to CD and SP, respectively (treatment difference -4.4%, [95% CI -10.1 to 1.3]). Haemoglobin in the CD group was significantly lower than in the SP group at day 7, a difference of -4 g/L (95% CI -6 to -2). Mean day 14 haemoglobin (measured only for the small number of patients whose day 7 data caused concern) was 94 g/L (92-96) and 97 g/L (92-102) after CD and SP, respectively. Glucose-6-phosphate dehydrogenase deficient patients on CD had greater odds than those on SP of having a fall of 20 g/dL or more in haemoglobin when baseline temperature was high. Methaemoglobinaemia was seen in the CD group (n=320, mean 0.4% [95% CI 0.4-0.4]) before treatment, 4.2% (95% CI 3.8-4.6) (n=301) at day 3, and 0.6% (0.6-0.7) (n=300) at day 7). INTERPRETATION CD had greater efficacy than SP in Africa and was well tolerated. Haematological adverse effects were more common with CD than with SP and were reversible. CD is a useful alternative where SP is failing due to resistance.
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Affiliation(s)
- A Alloueche
- London School of Hygiene and Tropical Medicine, London, UK
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27
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Abstract
BACKGROUND Venous thromboembolism (VTE) is postulated as a complex disease, but the heritability and mode of inheritance are uncertain. OBJECTIVE To determine if VTE (i) segregates in families; (ii) is attributable to inheritance, shared environment, or both; and (iii) the possible mode of inheritance. PATIENTS AND METHODS In a family-based study of relatives from 751 probands (60% female) with objectively diagnosed VTE (without cancer), we performed complex segregation analyses corrected for mode of ascertainment, considering age-specific, non-gender- and gender-specific liability classes under Mendelian and non-Mendelian assumptions. We tested 12 models categorized into four model sets: (i) sporadic (assumes no genetic effect); (ii) Mendelian inheritance of a major gene (including dominant, additive, recessive or codominant classes); (iii) mixed model (Mendelian inheritance including the same four classes plus the effect of polygenes); and (iv) non-Mendelian. RESULTS Among the 16 650 relatives, 753 (48% female) were affected with VTE, of whom 62% were first-degree relatives. The sporadic model was rejected in both non-gender- and gender-specific liability class analyses. Among the remaining gender-specific models, the unrestricted (non-Mendelian) inheritance model was favored with an estimated heritability of 0.52. Among the Mendelian models, the dominant mixed model was preferred, with an estimated heritability and major disease allele frequency of 0.62 and 0.25, respectively, suggesting an effect of several minor genes. CONCLUSION A multifactorial non-Mendelian inheritance model was favored as the cause for VTE, while a model postulating a purely environmental cause was rejected. VTE is probably a result of multigenic action as well as environmental exposures.
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Affiliation(s)
- J A Heit
- Division of Cardiovascular Diseases, Mayo Clinic and Mayo Foundation, Rochester, MN 55905, USA.
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28
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Hamilton AJ, Schellhorn NA, Endersby NM, Ridland PM, Ward SA. A dynamic binomial sequential sampling plan for Plutella xylostella (Lepidoptera: Plutellidae) on broccoli and cauliflower in Australia. J Econ Entomol 2004; 97:127-135. [PMID: 14998136 DOI: 10.1093/jee/97.1.127] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Binomial sequential sampling plans have been used widely for monitoring invertebrate pest populations. Such plans are typically based upon a single action threshold (AT), which represents the level of infestation that the grower is prepared to accept before using a control measure. For many cropping systems this acceptable infestation level is likely to vary, being dependent on factors such as the growth stage of the crop and the value or demands of the destination market (e.g., local or high-quality export). We developed and validated a computer-assisted plan that uses a dynamic AT. The plan has been developed for monitoring diamondback moth, Plutella xylostella (L.) on broccoli (Brassica oleracea variety botrytis L.) and cauliflower (Brassica oleracea variety botrytis L.), but the concepts and methodologies could be readily applied to other systems.
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Affiliation(s)
- A J Hamilton
- Department of Primary Industries (Knoxfield), Private Bag 15, Ferntree Gully Delivery Centre, Victoria 3156, Australia.
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29
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Rossiter HB, Ward SA, Howe FA, Wood DM, Kowalchuk JM, Griffiths JR, Whipp BJ. Effects of dichloroacetate on VO2 and intramuscular 31P metabolite kinetics during high-intensity exercise in humans. J Appl Physiol (1985) 2003; 95:1105-15. [PMID: 12754181 DOI: 10.1152/japplphysiol.00964.2002] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Traditional control theories of muscle O2 consumption are based on an "inertial" feedback system operating through features of the ATP splitting (e.g., [ADP] feedback, where brackets denote concentration). More recently, however, it has been suggested that feedforward mechanisms (with respect to ATP utilization) may play an important role by controlling the rate of substrate provision to the electron transport chain. This has been achieved by activation of the pyruvate dehydrogenase complex via dichloroacetate (DCA) infusion before exercise. To investigate these suggestions, six men performed repeated, high-intensity, constant-load quadriceps exercise in the bore of an magnetic resonance spectrometer with each of prior DCA or saline control intravenous infusions. O2 uptake (Vo2) was measured breath by breath (by use of a turbine and mass spectrometer) simultaneously with intramuscular phosphocreatine (PCr) concentration ([PCr]), [Pi], [ATP], and pH (by 31P-MRS) and arterialized-venous blood sampling. DCA had no effect on the time constant (tau) of either Vo2 increase or PCr breakdown [tauVo2 45.5 +/- 7.9 vs. 44.3 +/- 8.2 s (means +/- SD; control vs. DCA); tauPCr 44.8 +/- 6.6 vs. 46.4 +/- 7.5 s; with 95% confidence intervals averaging < +/-2 s]. DCA, however, resulted in significant (P < 0.05) reductions in 1). end-exercise [lactate] (-1.0 +/- 0.9 mM), intramuscular acidification (pH, +0.08 +/- 0.06 units), and [Pi] (-1.7 +/- 2.1 mM); 2). the amplitude of the fundamental components for [PCr] (-1.9 +/- 1.6 mM) and Vo2 (-0.1 +/- 0.07 l/min, or 8%); and 3). the amplitude of the Vo2 slow component. Thus, although the DCA infusion lessened the buildup of potential fatigue metabolites and reduced both the aerobic and anaerobic components of the energy transfer during exercise, it did not enhance either tauVo2 or tau[PCr], suggesting that feedback, rather than feedforward, control mechanisms dominate during high-intensity exercise.
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Affiliation(s)
- H B Rossiter
- St George;s Medical School, Department of Physiology, London SW17 ORE, United Kingdom
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30
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Eckstein-Ludwig U, Webb RJ, Van Goethem IDA, East JM, Lee AG, Kimura M, O'Neill PM, Bray PG, Ward SA, Krishna S. Artemisinins target the SERCA of Plasmodium falciparum. Nature 2003; 424:957-61. [PMID: 12931192 DOI: 10.1038/nature01813] [Citation(s) in RCA: 684] [Impact Index Per Article: 32.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2003] [Accepted: 05/12/2003] [Indexed: 11/08/2022]
Abstract
Artemisinins are extracted from sweet wormwood (Artemisia annua) and are the most potent antimalarials available, rapidly killing all asexual stages of Plasmodium falciparum. Artemisinins are sesquiterpene lactones widely used to treat multidrug-resistant malaria, a disease that annually claims 1 million lives. Despite extensive clinical and laboratory experience their molecular target is not yet identified. Activated artemisinins form adducts with a variety of biological macromolecules, including haem, translationally controlled tumour protein (TCTP) and other higher-molecular-weight proteins. Here we show that artemisinins, but not quinine or chloroquine, inhibit the SERCA orthologue (PfATP6) of Plasmodium falciparum in Xenopus oocytes with similar potency to thapsigargin (another sesquiterpene lactone and highly specific SERCA inhibitor). As predicted, thapsigargin also antagonizes the parasiticidal activity of artemisinin. Desoxyartemisinin lacks an endoperoxide bridge and is ineffective both as an inhibitor of PfATP6 and as an antimalarial. Chelation of iron by desferrioxamine abrogates the antiparasitic activity of artemisinins and correspondingly attenuates inhibition of PfATP6. Imaging of parasites with BODIPY-thapsigargin labels the cytosolic compartment and is competed by artemisinin. Fluorescent artemisinin labels parasites similarly and irreversibly in an Fe2+-dependent manner. These data provide compelling evidence that artemisinins act by inhibiting PfATP6 outside the food vacuole after activation by iron.
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Affiliation(s)
- U Eckstein-Ludwig
- Department of Cellular and Molecular Medicine, St George's Hospital Medical School, Cranmer Terrace, London SW17 0RE, UK
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31
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Ozyener F, Rossiter HB, Ward SA, Whipp BJ. Negative accumulated oxygen deficit during heavy and very heavy intensity cycle ergometry in humans. Eur J Appl Physiol 2003; 90:185-90. [PMID: 14504952 DOI: 10.1007/s00421-003-0870-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/23/2003] [Indexed: 10/26/2022]
Abstract
The concept of the accumulated O(2) deficit (AOD) assumes that the O(2) deficit increases monotonically with increasing work rate (WR), to plateau at the maximum AOD, and is based on linear extrapolation of the relationship between measured steady-state oxygen uptake ( VO(2)) and WR for moderate exercise. However, for high WRs, the measured VO(2) increases above that expected from such linear extrapolation, reflecting the superimposition of a "slow component" on the fundamental VO(2) mono-exponential kinetics. We were therefore interested in determining the effect of the VO(2) slow component on the computed AOD. Ten subjects [31 (12) years] performed square-wave cycle ergometry of moderate (40%, 60%, 80% and 90% ), heavy (40%Delta), very heavy (80%Delta) and severe (110% VO(2)(peak)) intensities for 10-15 min, theta(L)where is the estimated lactate threshold and Delta is the WR difference between and VO(2)(peak). VO(2) was determined breath-by-breath. Projected "steady-state" VO(2) values were determined from sub- tests. The measured VO(2) exceeded the projected value after approximately 3 min for both heavy and very heavy intensity exercise. This led to the AOD actually becoming negative. Thus, for heavy exercise, while the AOD was positive [0.63 (0.41) l] at 5 min, it was negative by 10 min [-0.61 (1.05) l], and more so by 15 min [-1.70 (1.64) l]. For the very heavy WRs, the AOD was [0.42 (0.67) l] by 5 min and reached -2.68 (2.09) l at exhaustion. For severe exercise, however, the AOD at exhaustion was positive in each case: +1.69 (0.39) l. We therefore conclude that the assumptions underlying the computation of the AOD are invalid for heavy and very heavy cycle ergometry (at least). Physiological inferences, such as the "anaerobic work capacity", are therefore prone to misinterpretation.
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Affiliation(s)
- F Ozyener
- Department of Physiology, St George's Hospital Medical School, London, UK
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32
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Rossiter HB, Ward SA, Howe FA, Kowalchuk JM, Griffiths JR, Whipp BJ. Dynamics of intramuscular 31P-MRS P(i) peak splitting and the slow components of PCr and O2 uptake during exercise. J Appl Physiol (1985) 2002; 93:2059-69. [PMID: 12391122 DOI: 10.1152/japplphysiol.00446.2002] [Citation(s) in RCA: 106] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The dynamics of pulmonary O(2) uptake (Vo(2)) during the on-transient of high-intensity exercise depart from monoexponentiality as a result of a "slow component" whose mechanisms remain conjectural. Progressive recruitment of glycolytic muscle fibers, with slow O(2) utilization kinetics and low efficiency, has, however, been suggested as a mechanism. The demonstration of high- and low-pH components of the exercising skeletal muscle (31)P magnetic resonance (MR) spectrum [inorganic phosphate (P(i)) peak] at high work rates (thought to be reflective of differences between oxidative and glycolytic muscle fibers) is also consistent with this conjecture. We therefore investigated the dynamics of Vo(2) (using a turbine and mass spectrometry) and intramuscular ATP, phosphocreatine (PCr), and P(i) concentrations and pH, estimated from the (31)P MR spectrum. Eleven healthy men performed prone square-wave high-intensity knee extensor exercise in the bore of a whole body MR spectrometer. A Vo(2) slow component of magnitude 15.9 +/- 6.9% of the phase II amplitude was accompanied by a similar response (11.9 +/- 7.1%) in PCr concentration. Only five subjects demonstrated a discernable splitting of the P(i) peak, however, which began from between 35 and 235 s after exercise onset and continued until cessation. As such, the dynamics of the pH distribution in intramuscular compartments did not consistently reflect the temporal features of the Vo(2) slow component, suggesting that P(i) splitting does not uniquely reflect the activity of oxidative or glycolytic muscle fibers per se.
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Affiliation(s)
- H B Rossiter
- Department of Physiology, St. George's Hospital Medical School, Tooting, London SW17 0RE, United Kingdom
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33
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Affiliation(s)
- I M Hastings
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK.
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34
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Abstract
The synergistic potential of a range of biguanides, their triazine metabolites, tetracyclines, and pyrimethamine in combination with atovaquone has been assessed. All five biguanides tested interacted synergistically with atovaquone against Plasmodium falciparum in vitro. All of the other compounds tested were either additive or antagonistic.
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Affiliation(s)
- K Jones
- Department of Pharmacology and Therapeutics, University of Liverpool, Liverpool L35QA, United Kingdom
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Rossiter HB, Marshall NP, Ward SA, Whipp BJ. Intra-breath profiles of alveolar gas exchange and the initial limb-to-lung transit delay during exercise in humans: relevance for modeling the exercise hyperpnea. Adv Exp Med Biol 2002; 499:337-42. [PMID: 11729904 DOI: 10.1007/978-1-4615-1375-9_54] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
- H B Rossiter
- Department of Physiology, St. George's Hospital Medical School, London, UK
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Ward SA, Poon CS. Beyond chemoreflex: plasticity, redundancy and self-organization in respiratory control: a workshop summary. Adv Exp Med Biol 2002; 499:267-72. [PMID: 11729889 DOI: 10.1007/978-1-4615-1375-9_42] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/22/2023]
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Rossiter HB, Ward SA, Kowalchuk JM, Howe FA, Griffiths JR, Whipp BJ. Dynamic asymmetry of phosphocreatine concentration and O(2) uptake between the on- and off-transients of moderate- and high-intensity exercise in humans. J Physiol 2002; 541:991-1002. [PMID: 12068057 PMCID: PMC2290368 DOI: 10.1113/jphysiol.2001.012910] [Citation(s) in RCA: 268] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The on- and off-transient (i.e. phase II) responses of pulmonary oxygen uptake (V(O(2))) to moderate-intensity exercise (i.e. below the lactate threshold, theta;(L)) in humans has been shown to conform to both mono-exponentiality and 'on-off' symmetry, consistent with a system manifesting linear control dynamics. However above theta;(L) the V(O(2)) kinetics have been shown to be more complex: during high-intensity exercise neither mono-exponentiality nor 'on-off' symmetry have been shown to appropriately characterise the V(O(2)) response. Muscle [phosphocreatine] ([PCr]) responses to exercise, however, have been proposed to be dynamically linear with respect to work rate, and to demonstrate 'on-off' symmetry at all work intenisties. We were therefore interested in examining the kinetic characteristics of the V(O(2)) and [PCr] responses to moderate- and high-intensity knee-extensor exercise in order to improve our understanding of the factors involved in the putative phosphate-linked control of muscle oxygen consumption. We estimated the dynamics of intramuscular [PCr] simultaneously with those of V(O(2)) in nine healthy males who performed repeated bouts of both moderate- and high-intensity square-wave, knee-extension exercise for 6 min, inside a whole-body magnetic resonance spectroscopy (MRS) system. A transmit-receive surface coil placed under the right quadriceps muscle allowed estimation of intramuscular [PCr]; V(O(2)) was measured breath-by-breath using a custom-designed turbine and a mass spectrometer system. For moderate exercise, the kinetics were well described by a simple mono-exponential function (following a short cardiodynamic phase for V(O(2))), with time constants (tau) averaging: tauV(O(2))(,on) 35 +/- 14 s (+/- S.D.), tau[PCr](on) 33 +/- 12 s, tauV(O(2))(,off) 50 +/- 13 s and tau[PCr](off) 51 +/- 13 s. The kinetics for both V(O(2)) and [PCr] were more complex for high-intensity exercise. The fundamental phase expressing average tau values of tauV(O(2))(,on) 39 +/- 4 s, tau[PCr](on) 38 +/- 11 s, tauV(O(2))(,off) 51 +/- 6 s and tau[PCr](off) 47 +/- 11 s. An associated slow component was expressed in the on-transient only for both V(O(2)) and [PCr], and averaged 15.3 +/- 5.4 and 13.9 +/- 9.1 % of the fundamental amplitudes for V(O(2)) and [PCr], respectively. In conclusion, the tau values of the fundamental component of [PCr] and V(O(2)) dynamics cohere to within 10 %, during both the on- and off-transients to a constant-load work rate of both moderate- and high-intensity exercise. On average, approximately 90 % of the magnitude of the V(O(2)) slow component during high-intensity exercise is reflected within the exercising muscle by its [PCr] response.
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Affiliation(s)
- H B Rossiter
- Department of Physiology, St George's Hospital Medical School, Cranmer Terrace, Tooting, London, UK
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Neder JA, Sword D, Ward SA, Mackay E, Cochrane LM, Clark CJ. Home based neuromuscular electrical stimulation as a new rehabilitative strategy for severely disabled patients with chronic obstructive pulmonary disease (COPD). Thorax 2002; 57:333-7. [PMID: 11923552 PMCID: PMC1746295 DOI: 10.1136/thorax.57.4.333] [Citation(s) in RCA: 215] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
BACKGROUND Passive training of specific locomotor muscle groups by means of neuromuscular electrical stimulation (NMES) might be better tolerated than whole body exercise in patients with severe chronic obstructive pulmonary disease (COPD). It was hypothesised that this novel strategy would be particularly effective in improving functional impairment and the consequent disability which characterises patients with end stage COPD. METHODS Fifteen patients with advanced COPD (nine men) were randomly assigned to either a home based 6 week quadriceps femoris NMES training programme (group 1, n=9, FEV(1)=38.0 (9.6)% of predicted) or a 6 week control period before receiving NMES (group 2, n=6, FEV(1)=39.5 (13.3)% of predicted). Knee extensor strength and endurance, whole body exercise capacity, and health related quality of life (Chronic Respiratory Disease Questionnaire, CRDQ) were assessed. RESULTS All patients were able to complete the NMES training programme successfully, even in the presence of exacerbations (n=4). Training was associated with significant improvements in muscle function, maximal and endurance exercise tolerance, and the dyspnoea domain of the CRDQ (p<0.05). Improvements in muscle performance and exercise capacity after NMES correlated well with a reduction in perception of leg effort corrected for exercise intensity (p<0.01). CONCLUSIONS For severely disabled COPD patients with incapacitating dyspnoea, short term electrical stimulation of selected lower limb muscles involved in ambulation can improve muscle strength and endurance, whole body exercise tolerance, and breathlessness during activities of daily living.
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Affiliation(s)
- J A Neder
- Department of Respiratory Medicine, Hairmyres Hospital, East Kilbride and Centre for Exercise Science and Medicine, Institute of Biomedical and Life Sciences (IBLS), University of Glasgow, Glasgow, UK
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Whipp BJ, Rossiter HB, Ward SA. Exertional oxygen uptake kinetics: a stamen of stamina? Biochem Soc Trans 2002; 30:237-247. [PMID: 12023858] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The fundamental pulmonary O(2) uptake (.VO(2)) response to moderate, constant-load exercise can be characterized as (d.VO(2)/dt)(tau)+Delta.VO(2) (t)=Delta.VO(2SS) where Delta.VO(2SS) is the steady-state response, and tau is the time constant, with the .VO(2) kinetics reflecting intramuscular O(2) uptake (.QO(2)) kinetics, to within 10%. The role of phosphocreatine (PCr) turnover in .QO(2) control can be explored using (31)P-MR spectroscopy, simultaneously with .VO(2). Although tau.VO(2) and tauPCr vary widely among subjects (approx. 20-65 s), they are not significantly different from each other, either at the on- or off-transient. A caveat to interpreting the "well-fit" exponential is that numerous units of similar Delta.VO(2SS) but with a wide tau distribution can also yield a .VO(2) response with an apparent single tau. This tau is, significantly, inversely correlated with lactate threshold and .VO(2max)(but is poorly predictive; a frail stamen, therefore), consistent with tau not characterizing a compartment with uniform kinetics. At higher intensities, the fundamental kinetics become supplemented with a slowly-developing phase, setting .VO(2)on a trajectory towards maximum .VO(2). This slow component is also demonstrable in Delta[PCr]: the decreased efficiency thereby reflecting a predominantly high phosphate-cost of force production rather than a high O(2)-cost of phosphate production. We also propose that the O(2)-deficit for the slow-component is more likely to reflect shifting Delta.VO(2SS) rather than a single one with a single tau.
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Affiliation(s)
- Brian J Whipp
- Centre for Exercise Science and Medicine, University of Glasgow, Glasgow, G12 8QQ, Scotland, U.K.
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Abstract
The prediction that chronic obstructive pulmonary disease (COPD) will be the third leading cause of death worldwide by 2020 has enormous economic repercussions. Yet many issues and questions remain unresolved. For example, how can population studies of morbidity and mortality be viewed as comparable, without a worldwide consensus on the definition of COPD? How can the early diagnosis of COPD be improved? Why is it that only a minority of smokers develop COPD, despite tobacco smoking being the primary risk factor for chronic bronchitis and emphysema? How can the efficacy of smoking cessation interventions be improved? To what extent are the pathologic changes in the lungs reversible - and, if so, at what stage? And to what degree is it appropriate to emphasize the similar features of COPD and asthma? It is to be hoped that the emerging post-genomic and proteomic climate will facilitate the unlocking of the genetic substrate for COPD, and thus promote greater therapeutic specificity and efficacy.
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Affiliation(s)
- S A Ward
- Centre for Exercise Science and Medicine, University of Glasgow, UK.
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Affiliation(s)
- S. A. Ward
- Department of Zoology, LaTrobe University, Bundoora, Victoria 3083, Australia
| | - S. R. Leather
- Department of Biology, Imperial College, Silwood Park, Ascot SL5 7PY, UK
| | - J. Pickup
- Department of Agriculture and Fisheries for Scotland, East Craigs, Edinburgh EH12 8NJ, UK; and
| | - R. Harrington
- Entomology and Nematology Department, Rothamsted Experimental Station, Harpenden, Hertfordshire, AL5 2JQ, UK
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Rossiter HB, Ward SA, Kowalchuk JM, Howe FA, Griffiths JR, Whipp BJ. Effects of prior exercise on oxygen uptake and phosphocreatine kinetics during high-intensity knee-extension exercise in humans. J Physiol 2001; 537:291-303. [PMID: 11711581 PMCID: PMC2278929 DOI: 10.1111/j.1469-7793.2001.0291k.x] [Citation(s) in RCA: 149] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
1. A prior bout of high-intensity square-wave exercise can increase the temporal adaptation of pulmonary oxygen uptake (.V(O2)) to a subsequent bout of high-intensity exercise. The mechanisms controlling this adaptation, however, are poorly understood. 2. We therefore determined the dynamics of intramuscular [phosphocreatine] ([PCr]) simultaneously with those of .V(O2) in seven males who performed two consecutive bouts of high-intensity square-wave, knee-extensor exercise in the prone position for 6 min with a 6 min rest interval. A magnetic resonance spectroscopy (MRS) transmit-receive surface coil under the quadriceps muscle allowed estimation of [PCr]; .V(O2) was measured breath-by-breath using a custom-designed turbine and a mass spectrometer system. 3. The .V(O2) kinetics of the second exercise bout were altered compared with the first such that (a) not only was the instantaneous rate of .V(O2) change (at a given level of .V(O2)) greater but the phase II tau was also reduced - averaging 46.6 +/- 6.0 s (bout 1) and 40.7 +/- 8.4 s (bout 2) (mean +/- S.D.) and (b) the magnitude of the later slow component was reduced. 4. This was associated with a reduction of, on average, 16.1% in the total exercise-induced [PCr] decrement over the 6 min of the exercise, of which 4.0% was due to a reduction in the slow component of [PCr]. There was no discernable alteration in the initial rate of [PCr] change. The prior exercise, therefore, changed the multi-compartment behaviour towards that of functionally first-order dynamics. 5. These observations demonstrate that the .V(O2) responses relative to the work rate input for high-intensity exercise are non-linear, as are, it appears, the putative phosphate-linked controllers for which [PCr] serves as a surrogate.
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Affiliation(s)
- H B Rossiter
- Department of Physiology, St George's Hospital Medical School, Cranmer Terrace, Tooting, London SW17 0RE, UK
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Abstract
Since dyspnoeic sensation (delta) increases progressively with work rate (WR) and the duration of a volitional breath-hold (tBH) shortens, we wished to explore whether tBH might correlate sufficiently closely with delta to provide a quantitative and descriptor-free index of respiratory sensation during dynamic exercise. Nine healthy males exercised on a cycle ergometer at a series of constant WRs, above and below the lactate threshold. Ventilatory and gas exchange variables were measured breath-by-breath. At each WR, breath-holds to the limit of tolerance were taken; delta was recorded (visual-analog scale) immediately prior to and throughout each breath-hold. During breath-holds, delta increased with time as a "break-away" monoexponential characteristic, reaching the maximum (100%) at the break-point. Despite end-tidal partial pressure of carbon dioxide at the break-point being higher and end-tidal partial pressure of oxygen being lower with increasing WR, the relationship between WR and tBH declined curvilinearly (i.e. with large falls in tBH occurring in the low WR range, but far smaller reductions at higher WRs). The tBH/minute ventilation relationship had a similar form. The relationship between pre-breath-hold delta and tBH was also complex: the large reductions in tBH in the low WR range were associated with only modest increases in pre-BH delta while, at higher WRs, the progressively smaller decrements in tBH were associated with progressively larger increases in delta. We therefore conclude that breath-hold duration is unlikely to provide a useful correlate of exertional dyspnoea during dynamic exercise. Furthermore, the relative prolongation of tBH at high WRs (accounting for the more-extreme levels of end-tidal gas tensions) may reflect the attention-diverting influence of the exercise per se.
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Affiliation(s)
- S A Ward
- Centre for Exercise Science and Medicine, Institute of Biomedical and Life Sciences, Glasgow University, Glasgow G12 8QQ, UK.
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Jones K, Bray PG, Khoo SH, Davey RA, Meaden ER, Ward SA, Back DJ. P-Glycoprotein and transporter MRP1 reduce HIV protease inhibitor uptake in CD4 cells: potential for accelerated viral drug resistance? AIDS 2001; 15:1353-8. [PMID: 11504956 DOI: 10.1097/00002030-200107270-00004] [Citation(s) in RCA: 120] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND The multidrug transporters P-glycoprotein (P-gp) and MRP1 are functionally expressed in several subclasses of lymphocytes. HIV-1 protease inhibitors interact with both; consequently the transporters could reduce the local concentration of HIV-1 protease inhibitors and, thus, influence the selection of viral mutants. OBJECTIVES To study the effect of the expression of P-gp and MRP1 on the transport and accumulation of HIV-1 protease inhibitors in human lymphocytes and to study the effects of specific P-gp and MRP1 inhibitors. METHODS The initial rate and the steady-state intracellular accumulation of radiolabelled ritonavir, indinavir, saquinavir and nelfinavir was measured in three human lymphocyte cell lines: control CEM cells, CEM-MDR cells, which express 30-fold more P-gp than CEM cells, and CEM-MRP cells, which express fivefold more MRP1 protein than CEM cells. The effect of specific inhibitors of P-gp (GF 120918) and MRP1 (MK 571) was also examined. RESULTS Compared with CEM cells, the initial rates of uptake and the steady-state intracellular concentrations of all protease inhibitors are significantly reduced in CEM-MDR cells. The intracellular concentrations of the protease inhibitors are increased upon co-administration with GF 120918, in some cases to levels approaching those in CEM cells. The intracellular concentrations of the protease inhibitors are also significantly reduced in CEM-MRP cells. Co-administration with MK -571 can partially overcome these effects. CONCLUSIONS The overexpression of multidrug transporters significantly reduces the accumulation of protease inhibitors at this major site of virus replication, which, potentially, could accelerate the acquisition of viral resistance. Targeted inhibition of P-gp may represent an important strategy by which this problem can be overcome.
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Affiliation(s)
- K Jones
- Department of Pharmacology and Therapeutics, University of Liverpool, Liverpool, UK
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Abstract
1. The maximal oxygen uptake (V(O(2),peak)) during dynamic muscular exercise is commonly taken as a crucial determinant of the ability to sustain high-intensity exercise. Considerably less attention, however, has been given to the rate at which V(O(2)) increases to attain this maximum (or to its submaximal requirement), and even less to the kinetic features of the response following exercise. 2. Six, healthy, male volunteers (aged 22 to 58 years), each performed 13 exercise tests: initial ramp-incremental cycle ergometry to the limit of tolerance and subsequently, on different days, three bouts of square-wave exercise each at moderate, heavy, very heavy and severe intensities. Pulmonary gas exchange variables were determined breath by breath throughout exercise and recovery from the continuous monitoring of respired volumes (turbine) and gas concentrations (mass spectrometer). 3. For moderate exercise, the V(O(2)) kinetics were well described by a simple mono-exponential function, following a short cardiodynamic phase, with the on- and off-transients having similar time constants (tau(1)); i.e. tau(1,on) averaged 33 +/- 16 s (+/- S.D.) and tau(1,off) 29 +/- 6 s. 4. The on-transient V(O(2)) kinetics were more complex for heavy exercise. The inclusion of a second slow and delayed exponential component provided an adequate description of the response; i.e. tau(1,on) = 32 +/- 17 s and tau(2,on) = 170 +/- 49 s. The off-transient V(O(2)) kinetics, however, remained mono-exponential (tau(1,off) = 42 +/- 11 s). 5. For very heavy exercise, the on-transient V(O(2)) kinetics were also well described by a double exponential function (tau(1,on) = 34 +/- 11 s and tau(2,on) = 163 +/- 46 s). However, a double exponential, with no delay, was required to characterise the off-transient kinetics (i.e. tau(1,off) = 33 +/- 5 s and tau(2,off) = 460 +/- 123 s). 6. At the highest intensity (severe), the on-transient V(O(2)) kinetics reverted to a mono-exponential profile (tau(1,on) = 34 +/- 7 s), while the off-transient kinetics retained a two-component form (tau(1,off) = 35 +/- 11 s and tau(2,off) = 539 +/- 379 s). 7. We therefore conclude that the kinetics of V(O(2)) during dynamic muscular exercise are strikingly influenced by the exercise intensity, both with respect to model order and to dynamic asymmetries between the on- and off-transient responses.
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Affiliation(s)
- F Ozyener
- Department of Physiology, St George's Hospital Medical School, Cranmer Terrace, Tooting, London, UK
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Stead AM, Bray PG, Edwards IG, DeKoning HP, Elford BC, Stocks PA, Ward SA. Diamidine compounds: selective uptake and targeting in Plasmodium falciparum. Mol Pharmacol 2001; 59:1298-306. [PMID: 11306715 DOI: 10.1124/mol.59.5.1298] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Extensive drug resistance in Plasmodium falciparum emphasizes the urgent requirement for novel antimalarial agents. Here we report potent antimalarial activity of a number of diamidine compounds. The lead compound pentamidine is concentrated 500-fold by erythrocytes infected with P. falciparum. Pentamidine accumulation can be blocked by inhibitors of hemoglobin digestion, suggesting that the drug binds to ferriprotoporphyrin IX (FPIX). All of the compounds bound to FPIX in vitro and inhibited the formation of hemozoin. Furthermore, inhibitors of hemoglobin digestion markedly antagonized the antimalarial activity of the diamidines, indicating that binding to FPIX is crucial for the activity of diamidine drugs. Pentamidine was not accumulated into uninfected erythrocytes. Pentamidine transport into infected cells exhibits an initial rapid phase, nonsaturable in the micromolar range and sensitive to inhibition by furosemide and glibenclamide. Changing the counter-ion in the order Cl(-) < Br(-) < NO(2)(-) < I(-) <SCN(-) markedly stimulated pentamidine transport. These data suggest that pentamidine is transported although a pore or ion channel with properties similar to those of the recently characterized 'induced permeability pathway' on the infected red cell membrane. In summary, the diamidines exhibit two levels of selectivity against P. falciparum. The route of entry and molecular target are both specific to malaria-infected cells and are distinct from targets in other protozoa. Drugs that target the hemoglobin degradation pathway of malaria parasites have a proven record of accomplishment. The employment of induced permeability pathways to access this target represents a novel approach to antiparasite chemotherapy and offers an additional level of selectivity.
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Affiliation(s)
- A M Stead
- Department of Pharmacology and Therapeutics, The University of Liverpool, Liverpool, United Kingdom
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Affiliation(s)
- S A Ward
- Department of Pharmacology and Therapeutics, Liverpool School of Tropical Medicine, UK.
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Smith SL, Sadler CJ, Dodd CC, Edwards G, Ward SA, Park BK, McLean WG. The role of glutathione in the neurotoxicity of artemisinin derivatives in vitro. Biochem Pharmacol 2001; 61:409-16. [PMID: 11226374 DOI: 10.1016/s0006-2952(00)00556-6] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The role of antioxidants in the neurotoxicity of the antimalarial endoperoxides artemether and dihydroartemisinin was studied in vitro by quantitative image analysis of neurite outgrowth in the neuroblastoma cell line NB2a. Intracellular glutathione concentrations were measured by high performance liquid chromatography with fluorescence detection. Both dihydroartemisinin (1 microM) and a combination of artemether (0.3 microM) plus haemin (2 microM) significantly inhibited neurite outgrowth from differentiating NB2a cells to 11.5 +/- 11.0% (SD) and 19.6 +/- 15.2% of controls, respectively. The inhibition by artemether/haemin was prevented by the antioxidants superoxide dismutase (109.7 +/- 47.8% of control), catalase (107.0 +/- 29.3%) glutathione (123.8 +/- 12.4%), L-cysteine (88.0 +/- 6.3%), N-acetyl-L-cysteine (107.8 +/- 14.9%), and ascorbic acid (104.3 +/- 12.7%). Dihydroartemisinin-induced neurotoxicity was completely or partially prevented by L-cysteine (99.5 +/- 17.7% of control), glutathione (57.9 +/- 23.4% of control), and N-acetyl-L-cysteine (57.3 +/- 9.5%), but was not prevented by superoxide dismutase, catalase, or ascorbic acid. Buthionine sulphoximine, an inhibitor of gamma-glutamylcysteine synthetase, significantly increased the neurotoxic effect of non-toxic concentrations of artemether/haemin (0.1 microM/2 microM) and dihydroartemisinin (0.2 microM), suggesting that endogenous glutathione participates in the prevention of the neurotoxicity of artemether/haemin and dihydroartemisinin. Artemether/haemin completely depleted intracellular glutathione levels, whereas dihydroartemisinin had no effect. We conclude that although glutathione status is an important determinant in the neurotoxicity of endoperoxides, depletion of glutathione is not a prerequisite for their toxicity. This is consistent with their mechanisms of toxicity being free radical-mediated damage to redox-sensitive proteins essential for neurite outgrowth, or alteration of a redox-sensitive signalling system which regulates neurite outgrowth.
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Affiliation(s)
- S L Smith
- Department of Pharmacology and Therapeutics, University of Liverpool, L69 3GE, Liverpool, UK
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O'Neill PM, Miller A, Bishop LP, Hindley S, Maggs JL, Ward SA, Roberts SM, Scheinmann F, Stachulski AV, Posner GH, Park BK. Synthesis, antimalarial activity, biomimetic iron(II) chemistry, and in vivo metabolism of novel, potent C-10-phenoxy derivatives of dihydroartemisinin. J Med Chem 2001; 44:58-68. [PMID: 11141088 DOI: 10.1021/jm000987f] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The combination of TMSOTf and AgClO(4) promotes the efficient C-10-phenoxylation of dihydroartemisinin (3) in good chemical yield and excellent stereoselectivity. All of the new phenoxy derivatives have potent in vitro antimalarial activity. On the basis of the excellent yield and stereoselectivity obtained for the p-trifluoromethyl derivative 7b, this compound and the parent phenyl-substituted derivative 5b were selected for in vivo biological evaluation against Plasmodium berghei in the mouse model and for metabolism studies in rats. Compound 7b demonstrated excellent in vivo antimalarial potency with an ED(50) of 2.12 mg/kg (cf. artemether = 6 mg/kg) versus P. berghei. Furthermore, from preliminary metabolism studies, this compound was not metabolized to dihydroartemisinin; suggesting it should have a longer half-life and potentially lower toxicity than the first-generation derivatives artemether and arteether. From biomimetic Fe(II)-catalyzed decomposition studies and ESR spectroscopy, the mechanism of action of these new lead antimalarials is proposed to involve the formation of both primary and secondary C-centered cytotoxic radicals which presumably react with vital parasite thiol-containing cellular macromolecules.
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Affiliation(s)
- P M O'Neill
- Robert Robinson Laboratories, University of Liverpool, Liverpool L69 7ZD, England.
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Rossiter HB, Howe FA, Ward SA, Kowalchuk JM, Griffiths JR, Whipp BJ. Intersample fluctuations in phosphocreatine concentration determined by 31P-magnetic resonance spectroscopy and parameter estimation of metabolic responses to exercise in humans. J Physiol 2000; 528 Pt 2:359-69. [PMID: 11034625 PMCID: PMC2270138 DOI: 10.1111/j.1469-7793.2000.t01-1-00359.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The ATP turnover rate during constant-load exercise is often estimated from the initial rate of change of phosphocreatine concentration ([PCr]) using 31P-magnetic resonance spectroscopy (MRS). However, the phase and amplitude characteristics of the sample-to-sample fluctuations can markedly influence this estimation (as well as that for the time constant (tau) of the [PCr] change) and confound its physiological interpretation especially for small amplitude responses. This influence was investigated in six healthy males who performed repeated constant-load quadriceps exercise of a moderate intensity in a whole-body MRS system. A transmit- receive surface coil was placed under the right quadriceps, allowing determination of intramuscular [PCr]; pulmonary oxygen uptake (VO2) was simultaneously determined, breath-by-breath, using a mass spectrometer and a turbine volume measuring module. The probability density functions (PDF) of [PCr] and VO2 fluctuations were determined for each test during the steady states of rest and exercise and the PDF was then fitted to a Gaussian function. The standard deviation of the [PCr] and VO2 fluctuations at rest and during exercise (sr and sw, respectively) and the peak centres of the distributions (xc(r) and xc(w)) were determined, as were the skewness (gamma1) and kurtosis (gamma2) coefficients. There was no difference between sr and sw for [PCr] relative to the resting control baseline (s(r) = 1.554 %delta (s.d. = 0.44), s(w) = 1.514 %delta (s.d. = 0.35)) or the PDF peak centres (xc(r) = -0.013 %delta (s.d. = 0.09), xc(w) -0.197 %delta (s.d. = 0.18)). The standard deviation and peak centre of the 'noise' in VO2 also did not vary between rest and exercise (sr = 0.0427 l min(-1) (s.d. = 0.0104), s(w) = 0.0640 l min(-1) (s.d. = 0.0292); xc(r) = -0.0051 l min(-1) (s.d. = 0.0069), xc(w) 0.0022 l min(-1) (s.d. = 0.0034)). Our results demonstrate that the intersample 'noise' associated with [PCr] determination by 31P-MRS may be characterised as a stochastic Gaussian process that is uncorrelated with work rate, as previously described for VO2. This 'noise' can significantly affect the estimation of tau[PCr] and especially the initial rate of change of [PCr], i.e. the fluctuations can lead to variations in estimation of the initial rate of change of [PCr] of more than twofold, if the inherent 'noise' is not accounted for. This 'error' may be significantly reduced in such cases if the initial rate of change is estimated from the time constant and amplitude of the response.
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Affiliation(s)
- H B Rossiter
- Department of Physiology, St George's Hospital Medical School, Cranmer Terrace, Tooting, London SW17 0RE, UK
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