Displaying publications 41 - 60 of 105 in total

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  1. Intraspecific variation in Plasmodium falciparum
    Aikawa M, Ward RA
    Am J Trop Med Hyg, 1974 Jul;23(4):570-3.
    PMID: 4367833
    Matched MeSH terms: Plasmodium falciparum/drug effects
  2. The effects of diaphenylsulfone (DDS) against chloroquine-resistant Plasmodium falciparum
    Degowin RL, Eppes RB, Carson PE, Powell RD
    Bull World Health Organ, 1966;34(5):671-81.
    PMID: 5328901
    In view of the problems caused by the chloroquine-resistance of some strains of Plasmodium falciparum, the authors have investigated the effectiveness of diaphenylsulfone against two such resistant strains, from Malaya and Viet-Nam. They found that diaphenylsulfone given during acute attacks of malaria had a blood schizontocidal activity against the Malayan resistant strain but was not rapidly effective in terminating acute attacks in non-immune persons, and that, when the drug was given prophylactically in relatively small doses, it was substantially effective in preventing patency of mosquito-induced infection with the same strain. The protective effect of diaphenylsulfone is that of a clinical prophylactic or suppressive drug; it does not appear to be a true causal prophylactic. It was also found that the protective effect is vitiated by the concurrent administration of paraaminobenzoic acid.These studies indicate a need for further assessment of the antimalarial value of sulfones and sulfonamides, both alone and in combination with other drugs, for prevention and cure.
    Matched MeSH terms: Plasmodium falciparum/drug effects
  3. Leucophyllinines A and B, bisindole alkaloids from Leuconotis eugeniifolia
    Tang Y, Nugroho AE, Hirasawa Y, Tougan T, Horii T, Hadi AHA, et al.
    J Nat Med, 2019 Jun;73(3):533-540.
    PMID: 30911994 DOI: 10.1007/s11418-019-01297-5
    Two new bisindole alkaloids, leucophyllinines A (1) and B (2) consisting of eburnane and quebrachamine-type skeletons were isolated from the bark of Leuconotis eugeniifolia, and their structures were elucidated on the basis of spectroscopic data. Leucophyllinines A and B showed antiplasmodial activities against Plasmodium falciparum 3D7.
    Matched MeSH terms: Plasmodium falciparum/drug effects*
  4. Sub-lethal concentrations of artemisinin alter pH of the digestive vacuole of the malaria parasite, Plasmodium falciparum
    Ibrahim N, Roslee A, Azlan M, Abu-Bakar N
    Trop Biomed, 2020 Mar 01;37(1):1-14.
    PMID: 33612713
    An appropriate pH maintenance within a membrane-enclosed organelle is vital for the occurrence of biological processes. Artemisinin (ART), a potent antimalarial drug has been reported to target the digestive vacuole (DV) of Plasmodium falciparum, which might alter the pH of the organelle, thereby impairing the hemoglobin degradation and subsequent heme detoxification. Hence, a flow cytometry-based technique using fluorescein isothiocyanate-dextran (FITC-dextran) as a ratiometric pH probe was employed to measure the pH of the DV of the malaria parasite treated with ART. Based on the pH calibration curve generated, the steady-state pH of the acidic DV of the non-treated parasites was 5.42 ± 0.11, indicating that FITC-dextran is suitable for detection of physiological pH of the organelle. The alteration of the DV pH occurred when the parasites were treated with ART even at the sub-lethal concentrations (15 and 30 nM) used. The similar effect was shown by the parasites treated with a standard proton pump inhibitor, concanamycin A. This suggests that ART might have altered the DV pH at lower levels than the level needed to kill the parasite. This study has important implications in designing new ART treatment strategies and in generating new endoperoxide-based antimalarial drugs pertaining to the interruption of the pH regulation of the malaria parasite's DV.
    Matched MeSH terms: Plasmodium falciparum/drug effects*
  5. Effect of 7-day daily replacement of culture medium containing Eurycoma longifolia Jack constituents on the Malaysian Plasmodium falciparum isolates
    Ang HH, Chan KL, Mak JW
    J Ethnopharmacol, 1995 Dec 15;49(3):171-5.
    PMID: 8824743 DOI: 0.1016/0378-8741(95)01321-0
    Six Malaysian chloroquine-resistant Plasmodium falciparum isolates were cultured in vitro following the candle-jar method. Antimalarial evaluations of daily replacement of culture medium containing chloroquine and a semi-purified extract of Eurycoma longifolia Jack (containing 13 beta, 18-dihydroeurycomanol (1), eurycomanol-2-O-beta-D-glucopyranoside (2), eurycomanol (3) and eurycomanone (4)) were performed on 6-well plates at 37 degrees C for a week. Presence or absence of the parasites was determined microscopically on thin-film Giemsa-stained preparations. Results showed that the antimalarial activity of Eurycoma longifolia Jack was dose-dependent and reached a maximum of < 50% at 0.07-5.00 micrograms ml-1 after 1 day post-treatment. However, complete inhibitions were observed at 1.25-5.00 micrograms ml-1 extract after 3 days post-treatment and 0.62 and 0.31 micrograms ml-1 after 4 and 6 days post-treatment, respectively. Further results indicated that chloroquine exhibited total inhibition at concentrations > 2.50 and 0.62 micrograms ml-1 after 1 and 2 days post-treatment, respectively and at all concentrations after 3 days post-treatment.
    Matched MeSH terms: Plasmodium falciparum/drug effects*
  6. Antimalarial drug susceptibility of Plasmodium falciparum isolates from forest fringe dwelling aborigines (Orang Asli) of Peninsular Malaysia
    Lambros C, Davis DR, Lewis GE
    Am J Trop Med Hyg, 1989 Jul;41(1):3-8.
    PMID: 2669543 DOI: 10.4269/ajtmh.1989.41.1.TM0410010003
    The drug susceptibility of 70 isolates of Plasmodium falciparum to standard and experimental antimalarials was evaluated using a radioisotope microdilution method. All isolates were from forest fringe dwelling Orang Asli, the aborigines of Peninsular Malaysia. The geometric mean IC50 values were: chloroquine, 10 ng/ml; amodiaquine, 4.7 ng/ml; mefloquine, 2.8 ng/ml; quinine, 40.5 ng/ml; halofantrine, 1.5 ng/ml; enpiroline, 3 ng/ml; and pyrimethamine, 21 ng/ml. Four isolates exhibited decreased susceptibility to chloroquine (IC50 greater than 60 ng/ml), and one exhibited decreased susceptibility to quinine (IC50 = 161 ng/ml). Three isolates showed decreased susceptibility to mefloquine (IC50 = 10-11 ng/ml). The lack of drug pressure may account for the high prevalence of P. falciparum isolates susceptible to chloroquine.
    Matched MeSH terms: Plasmodium falciparum/drug effects*
  7. Fulltext A Basis for Rapid Clearance of Circulating Ring-Stage Malaria Parasites by the Spiroindolone KAE609
    Zhang R, Suwanarusk R, Malleret B, Cooke BM, Nosten F, Lau YL, et al.
    J Infect Dis, 2016 Jan 1;213(1):100-4.
    PMID: 26136472 DOI: 10.1093/infdis/jiv358
    Recent clinical trials revealed a surprisingly rapid clearance of red blood cells (RBCs) infected with malaria parasites by the spiroindolone KAE609. Here, we show that ring-stage parasite-infected RBCs exposed to KAE609 become spherical and rigid, probably through osmotic dysregulation consequent to the disruption of the parasite's sodium efflux pump (adenosine triphosphate 4). We also show that this peculiar drug effect is likely to cause accelerated splenic clearance of the rheologically impaired Plasmodium vivax- and Plasmodium falciparum-infected RBCs.
    Matched MeSH terms: Plasmodium falciparum/drug effects*
  8. Fulltext Falciparum malaria resistant to Fansidar (sulphadoxine-pyrimethamine) occurring in three children of the same family
    Ponnampalam JT
    Singapore Med J, 1982 Feb;23(1):37-8.
    PMID: 7051329
    Three cases of multiple drug resistant falciparum malaria in the same family are described. It is interesting to note that faIciparum malaria resistant to Fansidar has not as yet been reported in adults from West Malaysia up to the present time, although resistance to the drug in children is being encountered not infrequently. This presents a serious paediatric problem because malaria causes the highest incidence of mortality and morbidity in this age group in a proportion of the rural population.
    Matched MeSH terms: Plasmodium falciparum/drug effects*
  9. Gametocytocidal and sporontocidal effects of primaquine upon two strains of Plasmodium falciparum
    Rieckmann KH, McNamara JV, Kass L, Powell RD
    Mil Med, 1969 Sep;134(10):802-19.
    PMID: 4987059
    Matched MeSH terms: Plasmodium falciparum/drug effects*
  10. Effects of quinine and of chloroquine in vitro against a strain of chloroquine-resistant Plasmodium falciparum that displays a relative resistance to quinine in vivo
    Rieckmann KH, McNamara JV, Powell RD
    Mil Med, 1969 Sep;134(10):795-801.
    PMID: 4987058
    Matched MeSH terms: Plasmodium falciparum/drug effects*
  11. Fulltext KASP: a genotyping method to rapid identification of resistance in Plasmodium falciparum
    Alvarez-Fernandez A, Bernal MJ, Fradejas I, Martin Ramírez A, Md Yusuf NA, Lanza M, et al.
    Malar J, 2021 Jan 06;20(1):16.
    PMID: 33407529 DOI: 10.1186/s12936-020-03544-7
    BACKGROUND: The emergence and spread of anti-malarial resistance continues to hinder malaria control. Plasmodium falciparum, the species that causes most human malaria cases and most deaths, has shown resistance to almost all known anti-malarials. This anti-malarial resistance arises from the development and subsequent expansion of Single Nucleotide Polymorphisms (SNPs) in specific parasite genes. A quick and cheap tool for the detection of drug resistance can be crucial and very useful for use in hospitals and in malaria control programmes. It has been demonstrated in different contexts that genotyping by Kompetitive Allele Specific PCR (KASP), is a simple, fast and economical method that allows a high-precision biallelic characterization of SNPs, hence its possible utility in the study of resistance in P. falciparum.

    METHODS: Three SNPs involved in most cases of resistance to the most widespread anti-malarial treatments have been analysed by PCR plus sequencing and by KASP (C580Y of the Kelch13 gene, Y86N of the Pfmdr1 gene and M133I of the Pfcytb gene). A total of 113 P. falciparum positive samples and 24 negative samples, previously analysed by PCR and sequencing, were selected for this assay. Likewise, the samples were genotyped for the MSP-1 and MSP-2 genes, and the Multiplicity of Infection (MOI) and parasitaemia were measured to observe their possible influence on the KASP method.

    RESULTS: The KASP results showed the same expected mutations and wild type genotypes as the reference method, with few exceptions that correlated with very low parasitaemia samples. In addition, two cases of heterozygotes that had not been detected by sequencing were found. No correlation was found between the MOI or parasitaemia and the KASP values of the sample. The reproducibility of the technique shows no oscillations between repetitions in any of the three SNPs analysed.

    CONCLUSIONS: The KASP assays developed in this study were efficient and versatile for the determination of the Plasmodium genotypes related to resistance. The method is simple, fast, reproducible with low cost in personnel, material and equipment and scalable, being able to core KASP arrays, including numerous SNPs, to complete the main pattern of mutations associated to P. falciparum resistance.

    Matched MeSH terms: Plasmodium falciparum/drug effects
  12. Chloroquine resistant Plasmodium falciparum infection from Lampung and South Sumatra, Indonesia
    Pribadi W, Dakung LS, Gandahusada S, Daldyono
    Southeast Asian J Trop Med Public Health, 1981 Mar;12(1):69-73.
    PMID: 7020096
    A report was made of 4 cases of chloroquine resistant Plasmodium falciparum infections. The infections, detected in Jakarta, were imported from Kotabumi, Tanjung Karang, the Island of Pidada in the Lampung Province and from Pangkalpinang on the Island Bangka in the Province of South Sumatra. Treatment with courses of 1500 mg chloroquine base and with increased dosages up to 2250 mg base failed to cure the patients. The chloroquine sensitivity test in vitro was carried out in 3 patients, which showed that the Plasmodium falciparum strains were resistant to chloroquine at the R I level. The strains appeared to be similar to the Malaya Camp strain. In vivo observations revealed that the parasites were resistant at the R I level with a delayed recrudescence. The chloroquine resistant falciparum malaria cases, acquired in South Sumatra, may therefore be regarded as the first reported cases from a focus outside the already known two foci in Indonesia, namely East Kalimantan and Irian Jaya. It may be expected that chloroquine resistant Plasmodium falciparum will be encountered in other parts of Indonesia in the near future. The use of a combination of sulfadoxine and pyrimethamine should not be recommended in Indonesia because chloroquine is still considered the drug of choice against all malaria infections in Indonesia.
    Matched MeSH terms: Plasmodium falciparum/drug effects*
  13. Increased frequency of chloroquine resistant P. falciparum on a rubber estate in Peninsular Malaysia during two years of systematic chloroquine treatment
    Dondero TJ, Parsons RE, O'Holohan DR
    Southeast Asian J Trop Med Public Health, 1975 Dec;6(4):488-94.
    PMID: 775652
    Chloroquine pressure was applied over a 22 month period on a somewhat isolated, malarious rubber estate by examination of residents at 4-week intervals and treatment of parasitaemias with chloroquine. During this time the monthly attack rate for P. falciparum rose four-fold to an average of nearly 18% per month, while that of P. vivax remained relatively constant at about 8%. Eight in vivo chloroquine resistance studies, which allowed both detection of late recrudescing R-I resistance and estimation of the risk of reinfection, showed an apparent rise in the drug resistance rate, from 12% to 20% prior to the study to the range of 40-50%. Virtually all resistance encountered was R-I in nature. There was no convincing evidence of chloroquine resistance among 148 tested P. vivax infections.
    Matched MeSH terms: Plasmodium falciparum/drug effects
  14. Fulltext Effect of selected local medicinal plants on the asexual blood stage of chloroquine resistant Plasmodium falciparum
    Mohd Abd Razak MR, Afzan A, Ali R, Amir Jalaluddin NF, Wasiman MI, Shiekh Zahari SH, et al.
    BMC Complement Altern Med, 2014;14:492.
    PMID: 25510573 DOI: 10.1186/1472-6882-14-492
    The development of resistant to current antimalarial drugs is a major challenge in achieving malaria elimination status in many countries. Therefore there is a need for new antimalarial drugs. Medicinal plants have always been the major source for the search of new antimalarial drugs. The aim of this study was to screen selected Malaysian medicinal plants for their antiplasmodial properties.
    Matched MeSH terms: Plasmodium falciparum/drug effects*
  15. Fulltext Susceptibility of human Plasmodium knowlesi infections to anti-malarials
    Fatih FA, Staines HM, Siner A, Ahmed MA, Woon LC, Pasini EM, et al.
    Malar J, 2013;12:425.
    PMID: 24245918 DOI: 10.1186/1475-2875-12-425
    Evidence suggests that Plasmodium knowlesi malaria in Sarawak, Malaysian Borneo remains zoonotic, meaning anti-malarial drug resistance is unlikely to have developed in the absence of drug selection pressure. Therefore, adequate response to available anti-malarial treatments is assumed.
    Matched MeSH terms: Plasmodium falciparum/drug effects
  16. Melatonin effects on Plasmodium life cycle: new avenues for therapeutic approach
    Srinivasan V, Ahmad AH, Mohamed M, Zakaria R
    Recent Pat Endocr Metab Immune Drug Discov, 2012 May;6(2):139-47.
    PMID: 22537380
    Malaria remains a global health problem affecting more than 515 million people all over the world including Malaysia. It is on the rise, even within unknown regions that previous to this were free of malaria. Although malaria eradication programs carried out by vector control programs are still effective, anti-malarial drugs are also used extensively for curtailing this disease. But resistance to the use of anti-malarial drugs is also increasing on a daily basis. With an increased understanding of mechanisms that cause growth, differentiation and development of malarial parasites in rodents and humans, new avenues of therapeutic approaches for controlling the growth, synchronization and development of malarial parasites are essential. Within this context, the recent discoveries related to IP3 interconnected signalling pathways, the release of Ca2+ from intracellular stores of Plasmodium, ubiquitin protease systems as a signalling pathway, and melatonin influencing the growth and differentiation of malarial parasites by its effects on these signalling pathways have opened new therapeutic avenues for arresting the growth and differentiation of malarial parasites. Indeed, the use of melatonin antagonist, luzindole, has inhibited the melatonin's effect on these signalling pathways and thereby has effectively reduced the growth and differentiation of malarial parasites. As Plasmodium has effective sensors which detect the nocturnal plasma melatonin concentrations, suppression of plasma melatonin levels with the use of bright light during the night or by anti-melatonergic drugs and by using anti-kinase drugs will help in eradicating malaria on a global level. A number of patients have been admitted with regards to the control and management of malarial growth. Patents related to the discovery of serpentine receptors on Plasmodium, essential for modulating intra parasitic melatonin levels, procedures for effective delivery of bright light to suppress plasma melatonin levels and thereby arresting the growth and elimination of malarial parasites from the blood of the host are all cited in the paper. The purpose of the paper is to highlight the importance of melatonin acting as a cue for Plasmodium faciparum growth and to discuss the ways of curbing the effects of melatonin on Plasmodium growth and for arresting its life cycle, as a method of eliminating the parasite from the host.
    Matched MeSH terms: Plasmodium falciparum/drug effects
  17. Clinical efficacy of sulfadoxine-pyrimethamine in the treatment of falciparum malaria in Sabah, Malaysia
    Tan HS, Tan PE
    Ann Acad Med Singap, 1984 Apr;13(2):170-4.
    PMID: 6388486
    One hundred and ten consecutive patients with falciparum malaria were treated with Fansidar and primaquine. Of the 61 patients who were followed up at one week, 4 (6.6%) failed to clear their parasitaemia (1 R III and 3 R II treatment failures). Of the subsequent 40 patients who were seen again at one month, another 3 (7.5%) had recrudesced (R I treatment failure). A total of 7 patients thus experienced some form of treatment failure in the cohort of 40 who completed the one month follow up. Only 1 of these 7 patients (with R III treatment failure) failed to respond to repeat Fansidar treatment, and may be the only one with true Fansidar resistance. The overall treatment failure rate of 17.5% (95% confidence interval: 6-29%) in the cohort who completed the study is consistent with the known clinical efficacy of Fansidar. These results suggest no significant Fansidar resistance in falciparum malaria found in Sabah.
    Matched MeSH terms: Plasmodium falciparum/drug effects
  18. Chemosuppression of malaria by the triple combination mefloquine/sulfadoxine/pyrimethamine: a field trial in an endemic area in Malaysia
    Navaratnam V, Mohamad M, Hussain S, Kumar A, Jamaludin A, Sulaiman I, et al.
    Trans R Soc Trop Med Hyg, 1989 11 1;83(6):755-9.
    PMID: 2694509
    Malaria, particularly that due to chloroquine-resistant Plasmodium falciparum, which requires management with antimalarial drugs capable of protecting against multiresistant strains, has emerged in Malaysia. A study was carried out to assess the efficacy and tolerability of 2 dosages of mefloquine/sulfadoxine/pyrimethamine (MSP; RO 13-5112) compared to Fansidar in a malaria endemic area. 914 subjects in 3 random groups were studied. Occurrence of malaria was assessed both clinically as well as by blood films. Plasma drug levels were also measured. The results showed that the low dose of MSP was completely effective in suppressing parasitaemia. 2.7% of the study population reported adverse drug reactions, the lowest incidence being in subjects on the low dose; their blood chemical profiles were also the least affected. The plasma levels of pyrimethamine and sulfadoxine achieved in the low dose group were slightly higher than expected, but there was no significant difference in bioavailability. The study showed that, for chemoprophylaxis, a low dose of MSP provided effective protection with minimal side effects.
    Matched MeSH terms: Plasmodium falciparum/drug effects
  19. Fulltext Molecular detection of drug resistant malaria in Southern Thailand
    Noisang C, Prosser C, Meyer W, Chemoh W, Ellis J, Sawangjaroen N, et al.
    Malar J, 2019 Aug 15;18(1):275.
    PMID: 31416468 DOI: 10.1186/s12936-019-2903-y
    BACKGROUND: Drug resistance within the major malaria parasites Plasmodium vivax and Plasmodium falciparum threatens malaria control and elimination in Southeast Asia. Plasmodium vivax first-line treatment drug is chloroquine together with primaquine, and the first-line treatment for P. falciparum malaria is artemisinin in combination with a partner drug. Plasmodium vivax and P. falciparum parasites resistant to their respective first-line therapies are now found within Southeast Asia. The resistance perimeters may include high transmission regions of Southern Thailand which are underrepresented in surveillance efforts.

    METHODS: This study investigated blood samples from malaria centres in Southern Thailand. Genetic loci associated with drug resistance were amplified and sequenced. Drug resistance associated genes Pvmdr1, Pvcrt-o, Pvdhfr, and Pvdhps were characterized for 145 cases of P. vivax malaria, as well as the artemisinin resistance-associated Pfkelch13 gene from 91 cases of P. falciparum malaria.

    RESULTS: Plasmodium vivax samples from Southern Thai provinces showed numerous chloroquine and antifolate resistance-associated mutations, including SNP and Pvcrt-o K10-insertion combinations suggestive of chloroquine resistant P. vivax phenotypes. A high proportion of the C580Y coding mutation (conferring artemisinin resistance) was detected in P. falciparum samples originating from Ranong and Yala (where the mutation was previously unreported).

    CONCLUSIONS: The results demonstrate a risk of chloroquine and antifolate resistant P. vivax phenotypes in Southern Thailand, and artemisinin resistant P. falciparum observed as far south as the Thai-Malaysian border region. Ongoing surveillance of antimalarial drug resistance markers is called for in Southern Thailand to inform case management.

    Matched MeSH terms: Plasmodium falciparum/drug effects*
  20. Fluoxetine potentiates chloroquine and mefloquine effect on multidrug-resistant Plasmodium falciparum in vitro
    Khairul MF, Min TH, Low JH, Nasriyyah CH, A'shikin AN, Norazmi MN, et al.
    Jpn J Infect Dis, 2006 Oct;59(5):329-31.
    PMID: 17060702
    Fluoxetine (FLX), a P-glycoprotein inhibitor with antimalarial activity, is promising candidate for reversing chloroquine/mefloquine (CQ/MQ) resistance. The Dd2 strain of CQ- and MQ-resistant Plasmodium falciparum was synchronized and assayed with various concentrations of CQ/MQ individually and in combination with FLX or verapamil (VPL). Our results indicated the 50% inhibitory concentration values of CQ and MQ were greatly lowered when FLX was used simultaneously. Isobolograms indicated that CQ-FLX combinations are more synergistic (mean fractional inhibitory concentration [FIC] index 0.55) than MQ-FLX (mean FIC index 0.64), and their synergistic effect was better than or at par with CQ-VPL (mean FIC index 0.88) and MQ-VPL (mean FIC index 0.60) combinations. We conclude that the FLX potentiates the CQ and MQ response on multidrug-resistant P. falciparum at clinically achievable concentrations.
    Matched MeSH terms: Plasmodium falciparum/drug effects*
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