Browsing by Author "Samarawickrema, N.A."

Now showing 1 - 8 of 8

Antioxidant potential of two polyherbal preparations used in Ayurveda for the treatment of rheumatoid arthritis
(Elsevier, 2001) Thabrew, M.I.; Samarawickrema, N.A.; Munasinghe, C.
Reactive oxygen intermediates (ROI) are together with prostanoids, leukotrienes and proteases, believed to be the mediators of inflammation and responsible for the pathogenesis of tissue destruction in RA. Antioxidant (AO) activity is one of the mechanisms by which many conventional drugs used in day to day treatment of RA alleviate the painful symptoms associated with this disease. An investigation has been carried out to compare the antioxidant potentials of two polyherbal formulations, Maharasnadhi quathar (MRQ) and Weldehi choornaya (WC), used by Ayurvedic medical practitioners in Sri-Lanka for the treatment of RA patients. AO potentials of these preparations were assessed by their effects in RA patients on: (a) activities of the AO enzymes superoxide dismutase (SOD), glutathione peroxidase (GPX) and catalase; (b) lipid peroxidation (as estimated by thiobarbituric acid reacting substances (TBARS) generation); and (c) concentrations of serum iron and haemoglobin (Hb), and the total iron binding capacity (TIBC). The overall results of the study demonstrate that MRQ has much greater AO potential than WC. Thus, on treatment with MRQ for 3 months, the initial activities of plasma SOD, GPX and catalase, were enhanced by 44.6, 39.8 and 25.2%, respectively. There was no significant improvement in any of these enzyme activities in patients treated with WC for the same time period as MRQ. Although the extent of lipid peroxidation in plasma of RA patients could be decreased by both drug preparations, the reduction mediated in 3 months by MRQ (34%) was markedly greater than that due to WC (21.8%). The total serum iron and Hb concentrations and TIBC in the RA patients included in the study could be significantly improved by treatment with MRQ but not by WC. Thus, at the end of 3 months treatment with MRQ, concentrations of the total serum iron and Hb, and the TIBC of patients improved by 26.8, 24.8 and 16.1%, respectively. Possible reasons for differences in the AO potentials of MRQ and WC are discussed
Distribution of human papillomavirus genotypes in archival cervical tissue from women with cervical cancer in urban Sri Lanka
(Elsevier, 2011) Samarawickrema, N.A.; Tabrizi, S.N.; Hewavisenthi, J.; Leong, T.; Garland, S.M.
OBJECTIVE: To identify the contributions of various human papillomavirus (HPV) genotypes in tissue samples from women diagnosed with cervicalcancer in Sri Lanka. METHODS: In a retrospective study, archival cervical tissues samples (n=108) obtained from Sri Lankan women diagnosed with histologically proven invasive squamous cell carcinoma between 2006 and 2007 were tested for HPV. Genotyping of HPV DNA was performed using an INNO-LiPA assay. RESULTS: Overall, 93% of tumor samples tested positive for HPV DNA. HPV types 16 and 18 accounted collectively for 83.4% of the positive samples. CONCLUSION: The findings suggest that the HPV genotypes responsible for causing cervical cancer in Sri Lanka are similar to those reported elsewhere worldwide. Consequently, women in Sri Lanka could benefit from currently available prophylactic HPV vaccines should they be implemented.
Effect of oral supplementation with vitamin E on the oxido-reductive status of red blood cells in normal mice and mice subject to oxidative stress by chronic administration of adriamycin
(Sage Publishing, 1999) Thabrew, M.I.; Samarawickrema, N.A.; Chandrasena, L.G.; Jayasekara, S.
The effect of oral vitamin E supplementation on the oxido-reductive status of red blood cells in normal mice and those subject to oxidative stress by chronic administration of the anti-tumour drug Adriamycin was investigated. Mice were randomly separated into three groups of 20 animals each and maintained on diets identical in all respects except for vitamin E content. Group 1 received a low vitamin E diet that provided 10 mg vitamin E/kg body weight/day, group 2 received a normal mice chow diet (45 mg vitamin E/kg body weight/day) while group 3 received a high vitamin E diet (200 mg vitamin E/kg body weight/day). In comparison with the normal mice in group 1, their counterparts in groups 2 and 3 exhibited significantly higher (P 0.001) activities of superoxide dismutase (SOD) in red blood cells (79.4 percent higher in group 2 and 114.2 percent higher in group 3, respectively) and produced lower concentrations of malondialdehyde (MDA) (22.9 percent less in group 2 and 51.2 percent less in group 3, respectively), with little difference in the glutathione peroxidase (GPX) activity. In Adriamycin-treated animals on the low vitamin E diet (group 1) the red blood cell SOD activity and MDA production were 46.2 percent and 200.7percent higher (P 0.001), respectively, and the GPX activity was 39.1percent lower than in the red blood cells of untreated (normal) animals in the same group. The Adriamycin-induced changes were significantly less in animals receiving higher doses of vitamin E (groups 2 and 3). Thus, in the group maintained on the high vitamin E diet (group 3), Adriamycin administration resulted in only a 38.9 percent increase in the MDA production above that generated by red blood cells of normal mice in the same group, with no significant change in the SOD or GPX activities. Thus, in normal conditions as well as in conditions of oxidative stress, high doses of vitamin E appear to be able to protect the oxido-reductive status of red blood cells by modulating the extent of lipid peroxidation as well as the activities of antioxidant enzymes.
Protection by garlic against adriamycin induced alterations in the oxido-reductive status of mouse red blood cells
(Wiley, 2000) Thabrew, M.I.; Samarawickrema, N.A.; Chandrasena, L.G.; Jayasekara, S.
The effects of oral garlic supplementation on the activities of (a) the antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPX) and (b) lipid peroxidation, as assessed by malondialdehyde (MDA) production in red blood cells of normal mice and those subject to oxidative stress by chronic administration of the anti-tumour drug adriamycin has been investigated. As expected, adria-mycin administration resulted in a significant increase in MDA generation (by 105.4%) and a decrease in GPX activity (by 23.8%) in the red blood cells. Although garlic had no significant effects on the basal levels of the antioxidant enzymes or MDA generation in red blood cells of normal mice (untreated with adriamycin), at doses of 20 mg/kg or 100 mg/kg, garlic was able to decrease significantly the adriamycin induced changes in the oxido-reductive status of the redblood cells. Thus, on administration of adriamycin to mice fed diets containing 20 mg/kg or 100 mg/kg garlic, the drug-induced increase in MDA generation was 38.2% and 22.5% respectively, less than that produced by adriamycin in mice fed normal diets, containing no garlic (105.4%). Similarly, in mice fed diets providing 20 mg/kg and 100 mg/kg garlic, adriamycin was able to decrease GPX activity by only 15.1% and 7.6% respectively, less than that produced by adriamycin in rats fed normal diets, containing no garlic (23.9%).
Pyruvate ferrodoxin oxidoreductase from Entamoeba histolytica recognized by a monoclonal antibody
(SEAMEO Regional Tropical Medicine and Public Health Project, 1996) Thammapalerd, N.; Kotimanusvanij, D.; Duchene, M.; Upcroft, J. A.; Mitchell, R.; Healey, A.; Samarawickrema, N.A.; Tharavanij, S.; Wiedermann, G.; Uproft, P.
A mouse monoclonal antibody, Eh208C2-2 MAb, raised against whole cell antigens of Entamoeba histolytica trophozoites of the pathogenic strain HM-1: IMSS and polyclonal antisera (PAb) against membrane antigens of E. histolytica trophozoites of strain HTH-56: MUTM were screened against a cDNA library of the pathogenic strain, SFL3. The monoconal antibody detected many phage plaques expressing an E. histolytica protein. The DNA sequence encoding the protein was approximately 55% identical, over 1,100bp, to Trichomonas vaginalis pyruvate: ferredoxin oxidoreductase (PFOR) and pyruvate: flavodoxin oxidoreductase from Klebsiella pneumoniae, Anabaena variabilis and Enterobacter agglomerans. Two of seven clones detected by mouse polyclonal antisera also encoded this protein. Two others encoded Entamoeba Hsp70, another encoded Entamoeba alkyl-hydroperoxide reductase and the remaining two were unidentified sequences. Entamoeba PFOR is an abundant, antigenic protein which may be a useful target for the development of protective host immune responses against invasive amebiasis.
A Rapid method for cryopreserving Entamoeba histolytica
(Academic Press, 2001) Samarawickrema, N.A.; Upcroft, J. A.; Thammapalerd, N.; Uproft, P.
No Abstract Availabe
Superoxide dismutase and pyruvate ferrodoxin oxidoreductase involvement in mechanisms of metronidazole resistance in Entamoeba histolytica
(Oxford University Press, 1997) Samarawickrema, N.A.; Brown, D.M.; Upcroft, J.A.; Thammapalerd, N.; Uproft, P.
Metronidazole resistance has been induced in an axenic strain of Entamoeba histolytica (HTH-56:MUTM) following continuous exposure to steadily increasing drug concentrations. The drug-resistant line is routinely maintained in normally lethal levels of metronidazole (10 microM).Resistance to this concentration of drug was developed over 177 days. Decreased pyruvate:ferredoxin oxidoreductase (PFOR) activity in anaerobic organisms is one mechanism of metronidazole resistance but in entamoeba, PFOR activity was not decreased in metronidazole-resistant parasites as determined by immunofluorescent assays and immunoblotting studies. 2-Oxoacid oxidoreductase activity, which appeared to be due to a single enzyme, PFOR, was evident with pyruvate as well as the alternative substrates, alpha-ketobutyrate, alpha-ketoglutarate and oxaloacetate. A marked increase in superoxide dismutase (SOD) activity was detected in metronidazole-resistant E.histolytica. Increased SOD activity has not previously been documented as a mechanism of drug resistance although SOD has been associated with a range of stress situations in other organisms.
Toxicity due to organophosphorus compounds: what about chronic exposure?
(Oxford University Press, 2006) de Silva, H.J.; Samarawickrema, N.A.; Wickremasinghe, A.R.
The inappropriate use of toxic chemicals is common in developing countries, where it leads to excessive exposure and high risks of unintentional poisoning. The risks are particularly high with the pesticides used in agriculture, where poor rural populations live and work in close proximity to these compounds, which are often stored in and around the home. It is estimated that 99% of all deaths from pesticide poisoning occur in developing countries. Whilst the acute toxicity of pesticides has been well documented, there is still relatively little known of the effects on health of chronic pesticide exposure. Organophosphate insecticides have been extensively used in agriculture in developing countries, with little protection for the communities and individuals thus exposed. Given the indisputable chronic exposure of vulnerable groups to organophosphate compounds, including pregnant women, the fetus and young children, the potential for widespread adverse effects is considerable. Thus, whilst there is some evidence that chronic exposure may have adverse effects on health, there is an urgent need for high-quality observational and interventional studies of both occupational and environmental exposure to these compounds.