Harparkash Kaur - Academia.edu (original) (raw)
Papers by Harparkash Kaur
Background. Parasite clearance time after artemisinin-based combination therapy (ACT) may be incr... more Background. Parasite clearance time after artemisinin-based combination therapy (ACT) may be increasing in Asian and African settings. The association between parasite clearance following ACT and transmissibility is currently unknown.
Methods in Enzymology, 1994
American Heart Journal, 1995
... Xian-Liang Tang MD a , Harparkash Kaur PhD b , Jian-Zhong Sun MD, PhD a , Yumin Qiu MD, PhD a... more ... Xian-Liang Tang MD a , Harparkash Kaur PhD b , Jian-Zhong Sun MD, PhD a , Yumin Qiu MD, PhD a , Seong-Wook Park MD a , Margo Schleman MD b , Barry Halliwell ... c, Pharmacology Group, University of London King's College, Chelsea Campus, London, United Kingdom. ...
Malaria Journal, 2014
Background: The quality of routine indoor residual spraying (IRS) operations is rarely assessed b... more Background: The quality of routine indoor residual spraying (IRS) operations is rarely assessed because of the limited choice of methods available for quantifying insecticide content in the field. This study, therefore, evaluated a user-friendly, rapid colorimetric assay for detecting insecticide content after routine IRS operations were conducted. Methods: This study was conducted in Tafea Province, Vanuatu. Routine IRS was conducted with lambda cyhalothrin. Two methods were used to quantify the IRS activities: 1) pre-spray application of small felt pads and 2) post-spray removal of insecticide with adhesive. The insecticide content was quantified using a colorimetric assay (Insecticide Quantification Kit [IQK]), which involved exposing each sample to the test reagents for 15 mins. The concentration of insecticide was indicated by the depth of red colour.
Malaria journal, 2016
This meeting report presents the key findings and discussion points of a 1-day meeting entitled &... more This meeting report presents the key findings and discussion points of a 1-day meeting entitled 'Fake anti-malarials: start with the facts' held on 28th May 2015, in Geneva, Switzerland, to disseminate the findings of the artemisinin combination therapy consortium's drug quality programme. The teams purchased over 10,000 samples, using representative sampling approaches, from six malaria endemic countries: Equatorial Guinea (Bioko Island), Cambodia, Ghana, Nigeria, Rwanda and Tanzania. Laboratory analyses of these samples showed that falsified anti-malarials (<8 %) were found in just two of the countries, whilst substandard artemisinin-based combinations were present in all six countries and, artemisinin-based monotherapy tablets are still available in some places despite the fact that the WHO has urged regulatory authorities in malaria-endemic countries to take measures to halt the production and marketing of these oral monotherapies since 2007. This report summarize...
Canadian Journal of Chemistry, 1982
The Biochemical Journal, Jan 15, 2008
Background: There is little existing knowledge about actual quality of drugs provided by differen... more Background: There is little existing knowledge about actual quality of drugs provided by different providers in Nigeria and in many sub-Saharan African countries. Such information is important for improving malaria treatment that will help in the development and implementation of actions designed to improve the quality of treatment. The objective of the study was to determine the quality of drugs used for the treatment of malaria in a broad spectrum of public and private healthcare providers.
Free Radical Biology and Medicine, Mar 31, 1999
Hydroxytyrosol is one of the o-diphenolic compounds in extra virgin olive oil and has been sugges... more Hydroxytyrosol is one of the o-diphenolic compounds in extra virgin olive oil and has been suggested to be a potent antioxidant. The superoxide radical (O 2 •Ϫ ) and nitric oxide (NO • ) can react very rapidly to form peroxynitrite (ONOO Ϫ ), a reactive tissue damaging species thought to be involved in the pathology of several chronic diseases. Hydroxytyrosol was highly protective against the peroxynitrite-dependent nitration of tyrosine and DNA damage by peroxynitrite in vitro. Given that extra virgin olive oil is consumed daily by many humans, hydroxytyrosol derived from this diet could conceivably provide a defense against damage by oxidants in vivo. The biological activity of hydroxytyrosol in vivo will depend on its intake, uptake and access to cellular compartments.
Free Radical Research, Jul 7, 2009
American Journal of Physiology Heart and Circulatory Physiology, Feb 1, 2000
Bilirubin is a potent antioxidant generated intracellularly during the degradation of heme by the... more Bilirubin is a potent antioxidant generated intracellularly during the degradation of heme by the enzyme heme oxygenase. The purpose of this study was to determine the role of increased cardiac bilirubin in protection against postischemic myocardial dysfunction. Rat hearts were isolated and perfused according to the Langendorff technique to evaluate the recovery of myocardial function after 30 min of global ischemia and 60 min of reperfusion. We found that upregulation of the inducible isoform of heme oxygenase (HO-1) by treatment of animals with hemin 24 h before ischemia ameliorated myocardial function and reduced infarct size (tetrazolium staining) on reperfusion of isolated hearts. Tin protoporphyrin IX, an inhibitor of heme oxygenase activity, completely abolished the improved postischemic myocardial performance observed after hemin-mediated HO-1 induction. Likewise, cardiac tissue injury was exacerbated by treatment with tin protoporphyrin IX. Increased cardiac HO-1 expression and heme oxygenase activity were associated with enhanced tissue bilirubin content and an increased rate of bilirubin release into the perfusion buffer. Furthermore, exogenously administered bilirubin at concentrations as low as 100 nanomolar significantly restored myocardial function and minimized both infarct size and mitochondrial damage on reperfusion. Our data provide strong evidence for a primary role of HO-1-derived bilirubin in cardioprotection against reperfusion injury.
Febs Lett, 1994
Peroxynitrite is a highly reactive species, generated from superoxide and mtrlc oxide. Some effec... more Peroxynitrite is a highly reactive species, generated from superoxide and mtrlc oxide. Some effects of peroxynitrite are ascribed to the molecule Itself, but decomposition products of the protonated form. peroxynitrous acid, may account for much of its reactivity in biological systems. Suggested products include highly-reactive hydroxyl radicals, but thermodynamic calculations have been used to claim that free hydroxyl radicals cannot be formed from peroxynitrite. We utilized aromatic hydroxylation of phenylalanine as a specific detector of hydroxyl radicals, and found that incubation of phenylalanine with peroxynitrite leads to a small amount ofp-. mand o-tyrosine. specific products of attack by this radical. Products of nitration of phenylalanine and tyrosine were also detected, as was dityrosine. Peroxynitrite decomposition generates several reactive species, including some that can nitrate aromatic rings. Formation of nitro-aromatic compounds may be a useful marker of peroxynitrite generation in biological systems.
There is considerable dispute about whether the hydroxylating ability of peroxynitrite (ONOO-)- d... more There is considerable dispute about whether the hydroxylating ability of peroxynitrite (ONOO-)- derived species involves hydroxyl radicals (OH.). This was investigated by using salicylate and phenylalanine, attack of OH. upon which leads to the formation of 2,3- and 2,5-dihydroxybenzoates, and o- m- and p- tyrosines respectively. On addition of ONOO- to salicylate, characteristic products of hydroxylation (and nitration) were observed in decreasing amounts with rise in pH, although added products of hydroxylation of salicylate were not recovered quantitatively at pH 8.5, suggesting further oxidation of these products and underestimating of hydroxylation at alkaline pH. Hydroxylation products decreased in the presence of several OH. scavengers, especially formate, to extents similar to those obtained when hydroxylation was achieved by a mixture of iron salts, H2O2 and ascorbate. However, OH. scavengers also inhibited formation of salicylate nitration products. Ortho, p- and m-tyrosines as well as nitration products were also observed when ONOO- was added to phenylalanine. The amount of these products again decreased at high pH and were decreased by addition of OH. scavengers. We conclude that although comparison with Fenton systems suggests OH. formation, simple homolytic fission of peroxynitrous acid (ONOOH) to OH. and NO2. would not explain why OH. scavengers inhibit formation of nitration products.
Journal of the Chemical Society, Chemical Communications, 1981
... Paper. J. Chem. Soc., Chem. Commun., 1981, 142 - 143, DOI: 10.1039/ C39810000142. A water-sol... more ... Paper. J. Chem. Soc., Chem. Commun., 1981, 142 - 143, DOI: 10.1039/ C39810000142. A water-soluble, nitroso-aromatic spin-trap Harparkash Kaur, KHW Leung and M. John Perkins. The preparation and use in spin-trapping ...
![Research paper thumbnail of [16] Nitrotyrosine as biomarker for reactive nitrogen species](https://attachments.academia-assets.com/43851853/thumbnails/1.jpg)
](Meth Enzymology, 1996
This chapter discusses the modification of proteins by reactive nitrogen species (RNS) and of tyr... more This chapter discusses the modification of proteins by reactive nitrogen species (RNS) and of tyrosine residues. The mechanisms by which tyrosine is modified by nitrogen oxides (NO), and assay methods for 3-nitrotyrosine, a modified product of tyrosine specific for RNS is also described. The biological systems are commonly exposed to various oxides of nitrogen with the nitrogen atom present in various oxidation states, ranging from +1 to +5. Tyrosine modification by NO has received attention because one of the major products formed (3-nitrotyrosine) is a stable end product, and characteristic of nitrogen oxides. The analysis of modified tyrosine residues is also reviewed. RNS reacts with various amino acid residues in proteins, forming metabolites which may be specific for particular RNS. The analysis of specific products, such as 3-nitrotyrosine, is useful in determining formation of RNS in vivo. Reaction of NO2. with tyrosine is demonstrated to result in formation of phenoxyl radicals that can either dimerize or combine with NO2. to form 3-nitrotyrosine. The peroxynitrite (ONOO–) also oxidizes tyrosine to form both the dimer and 3-nitrotyrosine as the most important products.
Background. Parasite clearance time after artemisinin-based combination therapy (ACT) may be incr... more Background. Parasite clearance time after artemisinin-based combination therapy (ACT) may be increasing in Asian and African settings. The association between parasite clearance following ACT and transmissibility is currently unknown.
Methods in Enzymology, 1994
American Heart Journal, 1995
... Xian-Liang Tang MD a , Harparkash Kaur PhD b , Jian-Zhong Sun MD, PhD a , Yumin Qiu MD, PhD a... more ... Xian-Liang Tang MD a , Harparkash Kaur PhD b , Jian-Zhong Sun MD, PhD a , Yumin Qiu MD, PhD a , Seong-Wook Park MD a , Margo Schleman MD b , Barry Halliwell ... c, Pharmacology Group, University of London King's College, Chelsea Campus, London, United Kingdom. ...
Malaria Journal, 2014
Background: The quality of routine indoor residual spraying (IRS) operations is rarely assessed b... more Background: The quality of routine indoor residual spraying (IRS) operations is rarely assessed because of the limited choice of methods available for quantifying insecticide content in the field. This study, therefore, evaluated a user-friendly, rapid colorimetric assay for detecting insecticide content after routine IRS operations were conducted. Methods: This study was conducted in Tafea Province, Vanuatu. Routine IRS was conducted with lambda cyhalothrin. Two methods were used to quantify the IRS activities: 1) pre-spray application of small felt pads and 2) post-spray removal of insecticide with adhesive. The insecticide content was quantified using a colorimetric assay (Insecticide Quantification Kit [IQK]), which involved exposing each sample to the test reagents for 15 mins. The concentration of insecticide was indicated by the depth of red colour.
Malaria journal, 2016
This meeting report presents the key findings and discussion points of a 1-day meeting entitled &... more This meeting report presents the key findings and discussion points of a 1-day meeting entitled 'Fake anti-malarials: start with the facts' held on 28th May 2015, in Geneva, Switzerland, to disseminate the findings of the artemisinin combination therapy consortium's drug quality programme. The teams purchased over 10,000 samples, using representative sampling approaches, from six malaria endemic countries: Equatorial Guinea (Bioko Island), Cambodia, Ghana, Nigeria, Rwanda and Tanzania. Laboratory analyses of these samples showed that falsified anti-malarials (<8 %) were found in just two of the countries, whilst substandard artemisinin-based combinations were present in all six countries and, artemisinin-based monotherapy tablets are still available in some places despite the fact that the WHO has urged regulatory authorities in malaria-endemic countries to take measures to halt the production and marketing of these oral monotherapies since 2007. This report summarize...
Canadian Journal of Chemistry, 1982
The Biochemical Journal, Jan 15, 2008
Background: There is little existing knowledge about actual quality of drugs provided by differen... more Background: There is little existing knowledge about actual quality of drugs provided by different providers in Nigeria and in many sub-Saharan African countries. Such information is important for improving malaria treatment that will help in the development and implementation of actions designed to improve the quality of treatment. The objective of the study was to determine the quality of drugs used for the treatment of malaria in a broad spectrum of public and private healthcare providers.
Free Radical Biology and Medicine, Mar 31, 1999
Hydroxytyrosol is one of the o-diphenolic compounds in extra virgin olive oil and has been sugges... more Hydroxytyrosol is one of the o-diphenolic compounds in extra virgin olive oil and has been suggested to be a potent antioxidant. The superoxide radical (O 2 •Ϫ ) and nitric oxide (NO • ) can react very rapidly to form peroxynitrite (ONOO Ϫ ), a reactive tissue damaging species thought to be involved in the pathology of several chronic diseases. Hydroxytyrosol was highly protective against the peroxynitrite-dependent nitration of tyrosine and DNA damage by peroxynitrite in vitro. Given that extra virgin olive oil is consumed daily by many humans, hydroxytyrosol derived from this diet could conceivably provide a defense against damage by oxidants in vivo. The biological activity of hydroxytyrosol in vivo will depend on its intake, uptake and access to cellular compartments.
Free Radical Research, Jul 7, 2009
American Journal of Physiology Heart and Circulatory Physiology, Feb 1, 2000
Bilirubin is a potent antioxidant generated intracellularly during the degradation of heme by the... more Bilirubin is a potent antioxidant generated intracellularly during the degradation of heme by the enzyme heme oxygenase. The purpose of this study was to determine the role of increased cardiac bilirubin in protection against postischemic myocardial dysfunction. Rat hearts were isolated and perfused according to the Langendorff technique to evaluate the recovery of myocardial function after 30 min of global ischemia and 60 min of reperfusion. We found that upregulation of the inducible isoform of heme oxygenase (HO-1) by treatment of animals with hemin 24 h before ischemia ameliorated myocardial function and reduced infarct size (tetrazolium staining) on reperfusion of isolated hearts. Tin protoporphyrin IX, an inhibitor of heme oxygenase activity, completely abolished the improved postischemic myocardial performance observed after hemin-mediated HO-1 induction. Likewise, cardiac tissue injury was exacerbated by treatment with tin protoporphyrin IX. Increased cardiac HO-1 expression and heme oxygenase activity were associated with enhanced tissue bilirubin content and an increased rate of bilirubin release into the perfusion buffer. Furthermore, exogenously administered bilirubin at concentrations as low as 100 nanomolar significantly restored myocardial function and minimized both infarct size and mitochondrial damage on reperfusion. Our data provide strong evidence for a primary role of HO-1-derived bilirubin in cardioprotection against reperfusion injury.
Febs Lett, 1994
Peroxynitrite is a highly reactive species, generated from superoxide and mtrlc oxide. Some effec... more Peroxynitrite is a highly reactive species, generated from superoxide and mtrlc oxide. Some effects of peroxynitrite are ascribed to the molecule Itself, but decomposition products of the protonated form. peroxynitrous acid, may account for much of its reactivity in biological systems. Suggested products include highly-reactive hydroxyl radicals, but thermodynamic calculations have been used to claim that free hydroxyl radicals cannot be formed from peroxynitrite. We utilized aromatic hydroxylation of phenylalanine as a specific detector of hydroxyl radicals, and found that incubation of phenylalanine with peroxynitrite leads to a small amount ofp-. mand o-tyrosine. specific products of attack by this radical. Products of nitration of phenylalanine and tyrosine were also detected, as was dityrosine. Peroxynitrite decomposition generates several reactive species, including some that can nitrate aromatic rings. Formation of nitro-aromatic compounds may be a useful marker of peroxynitrite generation in biological systems.
There is considerable dispute about whether the hydroxylating ability of peroxynitrite (ONOO-)- d... more There is considerable dispute about whether the hydroxylating ability of peroxynitrite (ONOO-)- derived species involves hydroxyl radicals (OH.). This was investigated by using salicylate and phenylalanine, attack of OH. upon which leads to the formation of 2,3- and 2,5-dihydroxybenzoates, and o- m- and p- tyrosines respectively. On addition of ONOO- to salicylate, characteristic products of hydroxylation (and nitration) were observed in decreasing amounts with rise in pH, although added products of hydroxylation of salicylate were not recovered quantitatively at pH 8.5, suggesting further oxidation of these products and underestimating of hydroxylation at alkaline pH. Hydroxylation products decreased in the presence of several OH. scavengers, especially formate, to extents similar to those obtained when hydroxylation was achieved by a mixture of iron salts, H2O2 and ascorbate. However, OH. scavengers also inhibited formation of salicylate nitration products. Ortho, p- and m-tyrosines as well as nitration products were also observed when ONOO- was added to phenylalanine. The amount of these products again decreased at high pH and were decreased by addition of OH. scavengers. We conclude that although comparison with Fenton systems suggests OH. formation, simple homolytic fission of peroxynitrous acid (ONOOH) to OH. and NO2. would not explain why OH. scavengers inhibit formation of nitration products.
Journal of the Chemical Society, Chemical Communications, 1981
... Paper. J. Chem. Soc., Chem. Commun., 1981, 142 - 143, DOI: 10.1039/ C39810000142. A water-sol... more ... Paper. J. Chem. Soc., Chem. Commun., 1981, 142 - 143, DOI: 10.1039/ C39810000142. A water-soluble, nitroso-aromatic spin-trap Harparkash Kaur, KHW Leung and M. John Perkins. The preparation and use in spin-trapping ...
Meth Enzymology, 1996
This chapter discusses the modification of proteins by reactive nitrogen species (RNS) and of tyr... more This chapter discusses the modification of proteins by reactive nitrogen species (RNS) and of tyrosine residues. The mechanisms by which tyrosine is modified by nitrogen oxides (NO), and assay methods for 3-nitrotyrosine, a modified product of tyrosine specific for RNS is also described. The biological systems are commonly exposed to various oxides of nitrogen with the nitrogen atom present in various oxidation states, ranging from +1 to +5. Tyrosine modification by NO has received attention because one of the major products formed (3-nitrotyrosine) is a stable end product, and characteristic of nitrogen oxides. The analysis of modified tyrosine residues is also reviewed. RNS reacts with various amino acid residues in proteins, forming metabolites which may be specific for particular RNS. The analysis of specific products, such as 3-nitrotyrosine, is useful in determining formation of RNS in vivo. Reaction of NO2. with tyrosine is demonstrated to result in formation of phenoxyl radicals that can either dimerize or combine with NO2. to form 3-nitrotyrosine. The peroxynitrite (ONOO–) also oxidizes tyrosine to form both the dimer and 3-nitrotyrosine as the most important products.