Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0024530 (malaria)
 44,886 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Differential screening of cDNA libraries constructed from knobby and predominantly knobless Plasmodium falciparum isolates, identified the sequence SD17. Chromosome blotting experiments have shown that this sequence, which is located on chromosome 2 of most isolates, was deleted in the cloned parasite line E12 of the FCQ27/PNG isolate. Here we show that erythrocytes infected with the SD17-containing cloned line D10 have typical knob structures on their surfaces, whereas those infected with the line E12 lack knobs. An expression clone was constructed from SD17 and used to affinity purify antibodies from the sera of individuals living in areas of Papua New Guinea where malaria is endemic. The antibodies reacted in immunoblotting experiments with a single polypeptide that varied in Mr from 85,000 to 105,000 among different isolates. The antigen was not expressed in the knobless clone E12. Postembedding immunoelectron microscopy showed localization of the antigen over the knobs of FC27 and two other isolates, largely on the cytoplasmic side. We conclude that the parasite antigen corresponding to clone SD17 is a knob protein.
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PMID:Plasmodium falciparum: identification and localization of a knob protein antigen expressed by a cDNA clone. 354 49

To assess the in vitro effect of retinol on Plasmodium falciparum, the standard isolates 3D7, D10, W2 and K1 in continuous culture were exposed to retinol added in concentrations ranging from 10(-7) to 0.1 mumol/l. Parasite growth inhibition was assessed from 3H-hypoxanthine incorporation. Triplicate experiments were performed at physiological pH and in the case of D10, additional experiments were performed at pH 7.2 and 7.6. Final media retinol concentrations were assayed using high performance liquid chromatography. Retinol inhibited growth of both asynchronous and synchronous cultures of 3D7 and D10 and asynchronous cultures of W2 and K1. IC50 values determined from assayed media concentrations ranged from 0.2 to 3.9 mumol/l and were comparable to concentrations in normal human serum (1.0-3.0 mumol/l). IC50 values for asynchronous D10 cultures at pH 7.2 were lower than at pH 7.4 or 7.6 (0.5, 3.9 and 5.0 mumol/l, respectively); results from synchronous cultures were similar. These data suggest that P. falciparum is a retinol-sensitive parasite, especially at pH levels equivalent to those in an acidotic patient. Adjunctive retinol therapy may have a role in clinical management of malaria.
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PMID:In vitro growth inhibition of Plasmodium falciparum by retinol at concentrations present in normal human serum. 958 31

Since the discovery of the chloroquine (CQ) resistance reversal properties of several different, structurally unrelated classes of compounds, including antidepressants, the way is again open to employ the aminoquinoline drugs to combat malaria effectively. In this study, CQ sensitivity was restored to varying extents in vitro in the CQ-resistant Plasmodium falciparum strain RSA11 by using the antidepressants amitriptyline, citalopram, oxaprotiline, and nomifensine. The 50% inhibitory concentrations (IC(50)) of CQ were reduced from 360 to as low as 11 nM when antidepressants were present. These particular antidepressants are highly specific for blocking the ATP-binding cassette transport protein-mediated reuptake of different neurotransmitters at the synaptic level. This study was aimed at determining the extent to which the neurotransmitter reuptake-blocking properties of these antidepressants play a role in the reversal process. None of the compounds or CQ-antidepressant combinations tested had innate antimalarial activity. No chemosensitizer or combination showed an increased CQ accumulation or significant shift in the IC(50) in the CQ-sensitive clone D10. Of the compounds tested, citalopram, a highly specific serotonin reuptake blocker, produced the largest shift observed in the IC(50) for the resistant isolate RSA11. No particular class of antidepressant was found to be better than any other at restoring CQ sensitivity. We conclude that the resistance-reversing properties of these compounds do not correlate with their activities as reuptake blockers.
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PMID:Role of the neurotransmitter reuptake-blocking activity of antidepressants in reversing chloroquine resistance in vitro in Plasmodium falciparum. 1099 45

The parasite lactate dehydrogenase (pLDH) assay method, a recently developed in vitro enzymatic method for evaluating antimalarial compounds, was used to examine the antiplasmodial activities of the aqueous leaf, stem-bark and fruit extracts of some plants used for the treatment and/or prophylaxis of malaria in KwaZulu-Natal province of South Africa. The in vitro antiplasmodial assay was carried out using a chloroquine-sensitive strain of malarial parasite, Plasmodium falciparum D10. A preliminary phytochemical analysis of the plant extracts was carried out using UV spectral analysis and thin-layer chromatography (TLC) to separate the chemical constituents of the extracts. Their chemical components were subsequently identified by treating the TLC plates with various spray reagents. Of the 14 plant extracts investigated, only 10 were found to have IC50 values of 10-50 micrograms/ml. The two most active extracts were Psidium guajava stem-bark extract and Vangueria infausta leaf extract, both of which showed IC50 values of 10-20 micrograms/ml. Phytochemical analysis of these two active plant extracts revealed the presence of anthraquinones, flavonoids, seccoirridoids and terpenoids.
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PMID:Studies on the antiplasmodial properties of some South African medicinal plants used as antimalarial remedies in Zulu folk medicine. 1242 27

The development of drug resistance and resurgence of malaria has highlighted the need for new chemically diverse antimalarial drugs. This study investigates Harpagophytum procumbens DC. as a source of antiplasmodial hit compounds. The roots of wild harvested plants as well as the aerial sections, seeds and roots of cultivated H. procumbens were evaluated for in vitro antiplasmodial activity. Bioassay-guided fractionation of the petroleum ether root extract yielded two diterpenes, (+)-8,11,13-totaratriene-12,13-diol (1) and (+)-8,11,13-abietatrien-12-ol (2). Compounds 1 and 2 displayed significant (IC50 < 1 microg/mL) in vitro antiplasmodial activity against a chloroquine-resistant (K1) and -sensitive (D10) strain of Plasmodium falciparum, and low cytotoxicity (SI > 65) against two mammalian cell lines (CHO and HepG2). It was found that 1 and 2 did not modify the erythrocyte shape, which in conjunction with the cytotoxicity results, indicates selective antiplasmodial activity.
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PMID:In vitro antiplasmodial activity of abietane and totarane diterpenes isolated from Harpagophytum procumbens (devil's claw). 1453 Oct 22

The increasing prevalence and distribution of malaria has been attributed to a number of factors, one of them being the emergence and spread of drug resistant parasites. Efforts are now being directed towards the discovery and development of new chemically diverse antimalarial agents. The present study reports on the in vitro antiplasmodial activity of 134 plant taxa native to or naturalised in South Africa, representing 54 families, which were selected semi-quantitatively using weighted criteria. The plant extracts were tested for in vitro activity against a Plasmodium falciparum strain D10 using the parasite lactate dehydrogenase (pLDH) assay. Of the 134 species assayed, 49% showed promising antiplasmodial activity (IC(50)< or = 10 microg/ml), while 17% were found to be highly active (IC(50)< or = 5 microg/ml). Several plant species and genera were shown for the first time to possess in vitro antiplasmodial activity. These results support a rational rather than random approach to the selection of antiplasmodial screening candidates, and identify a number of promising taxa for further investigation as plant-based antimalarial agents.
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PMID:In vitro antiplasmodial activity of medicinal plants native to or naturalised in South Africa. 1513 99

The roots of Eurycoma longifolia Jack have been used as traditional medicine to treat malaria. A systematic bioactivity-guided fractionation of this plant was conducted involving the determination of the effect of its various extracts and their chemical constituents on the lactate dehydrogenase activity of in vitro chloroquine-resistant Gombak A isolate and chloroquine-sensitive D10 strain of Plasmodium falciparum parasites. Their antiplasmodial activity was also compared with their known in vitro cytotoxicity against KB cells. Four quassinoids, eurycomanone (1), 13,21-dihydroeurycomanone (3), 13 alpha(21)-epoxyeurycomanone (4), eurycomalactone (6) and an alkaloid, 9-methoxycanthin-6-one (7), displayed higher antiplasmodial activity against Gombak A isolate but were less active against the D10 strain when compared with chloroquine. Amongst the compounds tested, 1 and 3 showed higher selectivity indices obtained for the cytotoxicity to antiplasmodial activity ratio than 14,15 beta-dihydroxyklaineanone (2), eurycomanol (5), 6 and 7.
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PMID:Antiplasmodial studies of Eurycoma longifolia Jack using the lactate dehydrogenase assay of Plasmodium falciparum. 1513 4

We have synthesized a series of novel 2,2'-bipyridyl and 1,10-phenanthroline benzoylthiourea complexes of platinum(II) with various substituents on the bipyridyl and phenanthroline ligands. All of these square-planar mixed-ligand cationic complexes were found to form moderately strong complexes with ferriprotoporphyrin IX in 40% aqueous DMSO (log K ranging from 4.81 to 6.24). The complexes also all inhibit beta-hematin (synthetic hemozoin or malaria pigment) formation in acetate solution. Four of the compounds were found to exhibit in vitro antimalarial activity, with (N-benzoyl-N',N'-di(2-hydroxyethyl)thioureato)(4,4'-di-tert-butyl-2,2'-bipyridyl)platinum(II) chloride being particularly active. These active complexes exhibited equally strong activity against both the D10 chloroquine sensitive and K1 chloroquine resistant strains of malaria parasite. Cytotoxicity testing of the four most active compounds shows that they exhibit selective activity against malaria parasites with selectivity indices greater than 85. These compounds represent a new family of potential antimalarials.
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PMID:In vitro antimalarial activity of a series of cationic 2,2'-bipyridyl- and 1,10-phenanthrolineplatinum(II) benzoylthiourea complexes. 1513 71

Antibody responses against proteins located on the surface or in the apical organelles of merozoites are presumed to be important components of naturally acquired protective immune responses against the malaria parasite Plasmodium falciparum. However, many merozoite antigens are highly polymorphic, and antibodies induced against one particular allelic form might not be effective in controlling growth of parasites expressing alternative forms. The apical membrane antigen 1 (AMA1) is a polymorphic merozoite protein that is a target of naturally acquired invasion-inhibitory antibodies and is a leading asexual-stage vaccine candidate. We characterized the antibody responses against AMA1 in 262 individuals from Papua New Guinea exposed to malaria by using different allelic forms of the full AMA1 ectodomain and some individual subdomains. The majority of individuals had very high levels of antibodies against AMA1. The prevalence and titer of these antibodies increased with age. Although antibodies against conserved regions of the molecule were predominant in the majority of individuals, most plasma samples also contained antibodies directed against polymorphic regions of the antigen. In a few individuals, predominantly from younger age groups, the majority of antibodies against AMA1 were directed against polymorphic epitopes. The D10 allelic form of AMA1 apparently contains most if not all of the epitopes present in the other allelic forms tested, which might argue for its inclusion in future AMA1-based vaccines to be tested. Some important epitopes in AMA1 involved residues located in domain II or III but depended on more than one domain.
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PMID:Allele specificity of naturally acquired antibody responses against Plasmodium falciparum apical membrane antigen 1. 1561 80

A series of thioacridone compounds that were previously shown to have DNA binding interaction, were screened for antimalarial activity. The new compounds were assessed for in vitro antimalarial activity against a chloroquine sensitive (D10) strain of the malaria parasite Plasmodium falciparum, using a lactate dehydrogenase (PfLDH) assay. In the series, the IC(50) values ranged from 0.4 to 27 microg/ml. 1-(2-Dimethylaminoethylamino)-9(10H)-thioacridone was found to be the most potent against P. falciparum (D10) with an IC(50) value of 0.4 microg/ml. This compound was also evaluated against a South African chloroquine resistant (RSA 11) P. falciparum strain and was found to have an IC(50) value of 1 microg/ml, compared with 0.16 microg/ml for chloroquine. Quantitative structure-activity relationships of this series were also investigated and a multiple linear regression r(2) of 0.58 was found for the best fit equation. The most potent compound, 1-(2-dimethylaminoethylamino)-9(10H)-thioacridone, was docked into the chloroquine binding site of PfLDH and it was found that the slightly lower activity of this compound, compared with chloroquine, is likely due to steric interference within a restricted binding pocket.
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PMID:Antimalarial activity of thioacridone compounds related to the acronycine alkaloid. 1569 83


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