Browsing by Author "Thammapalerd, N."

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    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.
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    A Rapid method for cryopreserving Entamoeba histolytica
    (Academic Press, 2001) Samarawickrema, N.A.; Upcroft, J. A.; Thammapalerd, N.; Uproft, P.
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    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.