Resistance of ten Thai isolates of Plasmodium falciparum to chloroquine and pyrimethamine by in vitro tests

Thaithong, Sodsri; Beale, G. H.

doi:10.1016/0035-9203(81)90333-3

Cited by 157 publications

(43 citation statements)

References 7 publications

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“…Continuous in vitro cultures of asexual erythrocytic stages of Plasmodium falciparum were maintained following the methods of Trager and Jensen (1976). Plant extracts and isolated compounds were tested on K1 strain (multidrug pyrimethamine/chloroquine-resistant strain) (Thaithong & Beale, 1981). Initial concentration of plant extracts and isolated compounds was 30 µg/mL diluted with two-fold dilutions to make seven concentrations, the lowest being at 0.47 µg/mL.…”

Section: Antimalarial Assaymentioning

confidence: 99%

In vitroantileishmanial, antiplasmodial and cytotoxic activities of a new ventiloquinone and five known triterpenes fromParinari excelsa

Attioua¹,

Yeo

Lagnika

et al. 2012

Pharmaceutical Biology

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Section: Antimalarial Assaymentioning

confidence: 99%

In vitroantileishmanial, antiplasmodial and cytotoxic activities of a new ventiloquinone and five known triterpenes fromParinari excelsa

Attioua¹,

Yeo

Lagnika

et al. 2012

Pharmaceutical Biology

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“…The drug was dissolved at 1-2 mg/ml directly into hypoxanthine-free complete medium, heated to 508C for 10 min to dissolve the drug, and then filter-sterilised using a 20-mm filter prior to use. The drug sensitivity assays were carried out as described previously with some modifications (Thaithong and Beale, 1981). Briefly, synchronised ringstage parasites were cultured at a starting parasitaemia of 1 and 2.5% haematocrit for 72 h. At 48 h fresh medium containing 0.2 mCi tritiated-hypoxanthine was added to each well.…”

Section: Drugs and Sensitivity Assaysmentioning

confidence: 99%

Negative selection of Plasmodium falciparum reveals targeted gene deletion by double crossover recombination

Duraisingh

Triglia

Cowman

2002

International Journal for Parasitology

160

192

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The genome sequence of Plasmodium falciparum, the causative agent of the most severe form of malaria in humans, rapidly approaches completion, but our ability to genetically manipulate this organism remains limited. Chromosomal integration has only been achieved following the prolonged maintenance of circularised episomal plasmids which selects for single crossover recombinants. It has not been possible to construct genetic deletions via double crossover recombination, presumably due to the low frequency of this event. We have used the Herpes simplex virus thymidine kinase gene and the Escherichia coli cytosine deaminase gene for negative selection of P. falciparum. Parasites were transformed with plasmids expressing the thymidine kinase and cytosine deaminase genes by positive selection for the human dihydrofolate reductase gene. Parasites expressing thymidine kinase are susceptible to the pro-drug ganciclovir while those expressing cytosine deaminase are sensitive to 5-fluorocytosine. Parental parasites were inherently resistant to these drugs. A significant 'bystander effect' was evident in cultures with either ganciclovir or 5-fluorocytosine. Positive and negative selection of the thymidine kinase transformants with both ganciclovir and WR99210 resulted in the selection of parasites containing a genetic deletion of the Pfrh3 gene, the first targeted double crossover deletions in P. falciparum. The use of negative selection for gene disruptions via double crossover recombination will dramatically improve our ability to analyse protein function and opens the possibility of using this strategy for a variety of gene deletion and modification experiments in the analysis of this important infectious agent. q

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“…The P: falcipururn lines used have all been described previously: K1 [18]; Vl/S, W2, SL/D6, 3D7, ItG2.F6, FCR3, It.Dl2 [15]; Tak9/96 [19]; M24, K39 [20]. They were maintained in erythrocytic culture [21,221 and RNA and DNA extracted [23], as previously described.…”

Section: Parasite Materialsmentioning

confidence: 99%

Sequence Variation of the Hydroxymethyldihydropterin Pyrophosphokinase: Dihydropteroate Synthase Gene in Lines of the Human Malaria Parasite, Plasmodium falciparum, with Differing Resistance to Sulfadoxine

Brooks

Wang

Read

et al. 1994

European Journal of Biochemistry

339

276

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Dihydropteroate synthase (H2Pte synthase) is the target of the sulfur‐based antimalarial drugs, which are frequently used in synergistic combination with inhibitors of dihydrofolate reductase (H2folate reductase) to combat chloroquine‐resistant malaria. We have isolated the H2Pte synthase coding sequence of the most pathogenic human parasite Plasmodium falciparum. It forms part of a longer coding sequence, located on chromosome 8, that also specifies 6‐hydroxymethyl‐7,8‐dihydropterin pyrophosphokinase (CH2OH‐H2pterinPP kinase) at its 5′ proximal end. This domain is unusually large, with two long insertions relative to other CH2OH‐H2pterinPP kinase molecules. To investigate a possible genetic basis for clinical resistance to sulfa drugs, we sequenced the complete H2Pte synthase domains from eleven isolates of P. falciparum with diverse geographical origins and levels of sulfadoxine resistance. Overall, point mutations in five positions were observed, affecting four codons. Parasite lines exhibiting high‐level resistance were found to carry either a double mutation, altering both Ser436 and Ala613, or a single mutation affecting Ala581. The mutations at positions 436 and 581 have the same location relative to each of two degenerate repeated amino acid motifs that are conserved across all other known H2Pte synthase molecules. The amino acid alteration at residue 613 is identically positioned relative to a different conserved motif. The fourth amino acid residue (437) affected by mutation, though adjacent to the apparently crucial residue 436, shows no obvious correlation with resistance. Although these mutations have no exact counterparts in any other organism, that at position 581 falls within a region of three amino acids where H2Pte synthase is modified in various ways in a number of sulfonamide‐resistant pathogenic bacteria. Copy‐number analysis indicated that there was no amplification of the H2Pte synthase domain in resistant parasite lines of P. falciparum, compared to sensitive lines.

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Resistance of ten Thai isolates of Plasmodium falciparum to chloroquine and pyrimethamine by in vitro tests

Cited by 157 publications

References 7 publications

In vitroantileishmanial, antiplasmodial and cytotoxic activities of a new ventiloquinone and five known triterpenes fromParinari excelsa

In vitroantileishmanial, antiplasmodial and cytotoxic activities of a new ventiloquinone and five known triterpenes fromParinari excelsa

Negative selection of Plasmodium falciparum reveals targeted gene deletion by double crossover recombination

Sequence Variation of the Hydroxymethyldihydropterin Pyrophosphokinase: Dihydropteroate Synthase Gene in Lines of the Human Malaria Parasite, Plasmodium falciparum, with Differing Resistance to Sulfadoxine

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