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Query: UMLS:C0024530 (malaria)
 44,886 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The methemoglobin reductase system plays a vital role in maintaining the equilibrium between hemoglobin and methemoglobin in blood. Exposure of red blood cells to oxidative stress (pathological/physiological) may cause impairment to this equilibrium. We studied the status of erythrocytic methemoglobin and the related reductase system during Plasmodium yoelii nigeriensis infection in mice and P. berghei infection in mastomys. Malaria infection was induced by intraperitoneal inoculation with 10(6) infected erythrocytes. The present investigation revealed a significant decrease in the activity of methemoglobin reductase, with a concomitant rise in methemoglobin content during P. yoelii nigeriensis infection in mice erythrocytes. This was accompanied with a significant increase in reduced glutathione and ascorbate levels. The activity of lactate dehydrogenase, glucose 6-phosphate dehydrogenase and glutathione reductase increased with a progressive rise in parasitemia. However, no methemoglobin or associated reductase activity was detected in normal and P. berghei-infected mastomys. P. berghei infection in mastomys resulted in an increase in the level of reduced glutathione and ascorbate in erythrocytes, and also in the activity of lactate dehydrogenase, glucose 6-phosphate dehydrogenase and glutathione reductase. These results suggest that antioxidants/antioxidant enzymes may prevent or reduce the formation of methemoglobin in the host and thereby protect the host from methemoglobinemia.
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PMID:Changes in rodent-erythrocyte methemoglobin reductase system produced by two malaria parasites, viz. Plasmodium yoelii nigeriensis and Plasmodium berghei. 1143 27

The OptiMAL is a rapid immunodiagnostic test developed by Flow Inc., Portland, Oreg. for diagnosis and differentiation of P. falciparum and non P. falciparum malaria infection. It has been based on detection of circulating parasite lactate dehydrogenase enzyme (pLDH), produced by live Plasmodium parasites. The purpose of this study was to compare the efficacy of the OptiMAL test with routine microscopic examination of Giemsa-Stained Thick Blood Film (routine GS-TBF) for the diagnosis of malaria at a local malaria clinic in a hyperendemic area of Thailand by using a standard GS-TBF (standard GS-TBF) as reference. One hundred and seventy five patients attending the clinic were recruited; 50, 42 and 83 were falciparum malaria, vivax malaria and non-malaria patients, respectively. Compared with the reference, the OptiMAL test had sensitivities of 92 per cent and 97.6 per cent, whereas, the routine GS-TBF had sensitivities of 81.3 per cent and 81 per cent for the detection of P. falciparum and P. vivax, respectively. Both tests showed no false positive resulting in 100 per cent specificities. However, the OptiMAL test was able to detect only 20 per cent of infection with less than 200 parasitaemia/microlitre. It was also shown in our study that the OptiMAL test was advantageous in follow-up of the treatment outcome. No false positive occurred among 40 follow-up cases. The OptiMAL test detected malaria infection more accurately than the routine GS-TBF (p < 0.05) and was simple, easy to perform and rapid. It is an alternative tool for the diagnosis of malaria in a hyperendemic area where experienced microscopists are not available.
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PMID:Comparison of the OptiMAL rapid test with routine microscopic examination of Giemsa-Stained Thick Blood Film for diagnosis of malaria. 1146 Sep 36

We compared the diagnostic performance characteristics of newly developed method, the rapid dipstick test, which provides colorimetric determination by developing antibody to the lactate dehydrogenase enzyme of parasites, with conventional standard thick-blood film examination. For the rapid test, OptiMAL commercial kits were used. The results were also evaluated with clinical findings from patients. The parasites were determined by microscopic examination of thick-blood films from 81 patients with vivax malaria from southeastern Anatolia, Turkey. The OptiMAL test results were found to be negative in five patients who were diagnosed clinically and through thick-film testing as having vivax malaria. There was no false positivity observed with the OptiMAL test. We concluded that this rapid malaria test has a lower level of sensitivity than the classical thick-blood-film test for malaria, but that these methods have equal specificity.
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PMID:Diagnostic performance characteristics of rapid dipstick test for Plasmodium vivax malaria. 1150 Jul 71

During pregnancy, Plasmodium falciparum infection of the placenta frequently occurs in the absence of parasites in peripheral blood. We investigated the abilities of the OptiMAL rapid immunochromatographic strip test for P. falciparum lactate dehydrogenase and species-specific PCR performed on peripheral blood to detect placental infection or malaria-associated low birth weight. Of 509 Malawian women screened by microscopy, 76 had malaria infection. Among these 509 women, the frequency of peripheral blood parasitemia was low. The OptiMAL test gave positive results in 37 of 171 women tested (one of whom had placental but not peripheral blood parasitemia) and had sensitivities of 71% for peripheral parasitemia and 38% for placental parasitemia compared to the microscopy values. The specificity for peripheral parasitemia was 94%. In 135 women, PCR had sensitivities of 94% for peripheral blood malaria detected by microscopy and 72% for placental infection. In samples examined by PCR, the prevalence of malaria in peripheral blood increased from 26.7% by microscopy to 51.9%. Women with placental malaria and women with malaria in peripheral blood samples by microscopy or OptiMAL testing, but not women with malaria detected only by PCR, had lower-birth-weight babies than did women without malaria by these criteria. Positive results by PCR in the absence of microscopic parasitemia were not associated with low birth weight. Neither OptiMAL nor PCR testing of peripheral blood is adequately sensitive to detect all placental malaria infection, but a positive result by OptiMAL testing identifies women with a high proportion of low-birth-weight babies.
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PMID:Evaluation of the OptiMAL rapid antigen test and species-specific PCR to detect placental Plasmodium falciparum infection at delivery. 1177 10

Malaria presents a diagnostic challenge to laboratories in most countries. Endemic malaria, population movements, and travelers all contribute to presenting the laboratory with diagnostic problems for which it may have little expertise available. Drug resistance and genetic variation has altered many accepted morphological appearances of malaria species, and new technology has given an opportunity to review available procedures. Concurrently the World Health Organization has opened a dialogue with scientists, clinicians, and manufacturers on the realistic possibilities for developing accurate, sensitive, and cost-effective rapid diagnostic tests for malaria, capable of detecting 100 parasites/microl from all species and with a semiquantitative measurement for monitoring successful drug treatment. New technology has to be compared with an accepted "gold standard" that makes comparisons of sensitivity and specificity between different methods. The majority of malaria is found in countries where cost-effectiveness is an important factor and ease of performance and training is a major consideration. Most new technology for malaria diagnosis incorporates immunochromatographic capture procedures, with conjugated monoclonal antibodies providing the indicator of infection. Preferred targeted antigens are those which are abundant in all asexual and sexual stages of the parasite and are currently centered on detection of HRP-2 from Plasmodium falciparum and parasite-specific lactate dehydrogenase or Plasmodium aldolase from the parasite glycolytic pathway found in all species. Clinical studies allow effective comparisons between different formats, and the reality of nonmicroscopic diagnoses of malaria is considered.
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PMID:Rapid diagnostic tests for malaria parasites. 1236 79

In Myanmar, we tested two rapid malaria immunochromatographic kits: the OptiMAL assay for the detection of parasite lactate dehydrogenase (pLDH), and the ICT Malaria P.f./P.v. test for histidine-rich protein 2 (PfHRP2) and panmalarial antigens. A total of 229 patients were examined, of whom 133 were found to be malaria positive by Giemsa microscopy. Both OptiMAL and ICT gave lower sensitivities than previously reported. ICT sensitivity for Plasmodium falciparum and non-falciparum parasites were 86.2 and 2.9%, respectively; specificity was 76.9 and 100%, respectively. OptiMAL sensitivity for P. falciparum and non-falciparum parasites were 42.6 and 47.1%, respectively; specificity was 97.0 and 96.9%, respectively. The sensitivity of both tests for the detection of both P. falciparum and non-falciparum parasites increased with parasite density. Several explanations for these results are explored. Our results raise particular concern over batch quality variations of malaria rapid diagnostic devices (MRDDs).
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PMID:A comparison of two rapid field immunochromatographic tests to expert microscopy in the diagnosis of malaria. 1190 3

We have previously demonstrated, using polyclonal and monoclonal antibodies, that the lactate dehydrogenase (LDH) of malaria parasites is immunologically distinct from the host enzyme. The polyclonal antibodies, produced against the affinity purified plasmodial LDH (pLDH) in rabbits, showed specificity to LDH of malaria parasites. In the present study, these anti-pLDH polyclonal antibodies were used to develop an immunodiagnostic test (immunodot enzyme assay of plasmodial LDH) based on the detection of parasite LDH in patient blood. The immunodot enzyme assay of plasmodial LDH was evaluated using blood samples from patients with malaria or other infections. Out of 502 microscopically positive malaria blood samples, 497 blood samples showed positive immunodot assays of pLDH while all the 423 microscopically negative cases were found negative by our test. The blood samples from other infections and non-endemic controls were negative by the immunodot enzyme assay of pLDH. This LDH based test was also found negative in blood samples of cured patients 7 days after chloroquine treatment. The test is simple to perform, can be read visually, econimal, highly specific with a sensitivity of approximately 99% and is thus suitable for accurate diagnosis of malaria in field conditions.
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PMID:Diagnosis of malaria by detection of plasmodial lactate dehydrogenase with an immunodot enzyme assay. 1214 51

In this study, we investigated the production of endothelin 1 (ET-1) by a human microvascular endothelial cell line, HMEC-1, co-cultured with Plasmodium falciparum-parasitized red blood cells (pRBCs). The results indicate that hypoxia increased the basal level of ET-1 production by HMEC-1 cells after 24 or 48 h of treatment. However, the co-incubation of HMEC-1 cells with pRBCs, but not with uninfected RBCs, induced a dose-dependent decrease of both constitutive and hypoxia-induced ET-1 production. The inhibition was not due to a decrease in cell viability, as lactate dehydrogenase release remained constant. These results indicate that pRBCs are able to interfere with both the constitutive and stimulated ET-1 release from the microvascular endothelium, thus inducing local modifications of the vascular tone and of the inflammatory response. This could be of relevance in the pathogenesis of the most severe forms of P. falciparum infections, such as cerebral malaria or malaria during pregnancy.
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PMID:Endothelin-1 production by a microvascular endothelial cell line treated with Plasmodium falciparum parasitized red blood cells. 1219 46

Aotus lemurinus griseimembra is considered one of the best nonhuman primate species for malarial studies because of its susceptibility to infection by Plasmodium falciparum asexual blood stages. However, reproducible transmission of infective P. falciparum sporozoites by mosquito inoculation has been difficult to achieve even in splenectomized monkeys. Characterization of an Aotus-P. falciparum cyclical transmission model has become a top priority as a result of the significant progress toward the development of preerythrocytic malaria vaccines. Herein, we describe a reproducible model developed using intact A. lemurinus griseimembra monkeys intravenously inoculated with sporozoites from a monkey-adapted P. falciparum (Santa Lucia) strain and a wild Falciparum-Cali-Colombia-4 (FCC-4) strain. Sporozoites were obtained by salivary gland dissection of laboratory-reared Anopheles albimanus mosquitoes. Parasitemia was monitored by thick-smear microscopy, parasite lactate dehydrogenase (pLDH) determination, and mosquito xenodiagnosis. The last method proved to be the most sensitive method for monitoring parasitemias. Infection with the Santa Lucia strain showed a mean prepatent period of 16 days (range 6-21 days), whereas infection with the wild FCC-4 strain resulted in a 24-day prepatent period. Mean peak parasite density was approximately 900 parasites/microliter for both parasite strains. The prepatent period, the peak of parasitemia, and the duration of patency were independent of the size of the sporozoite inoculum and the presence of spleen in the host. This model is being successfully used to test the protective efficacy of P. falciparum preerythrocytic vaccine candidates.
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PMID:Reproducible infection of intact Aotus lemurinus griseimembra monkeys by Plasmodium falciparum sporozoite inoculation. 1219 21

Alternative, non-microscopic methods for the diagnosis of malaria have recently become available. Among these, rapid dipstick methods stand out. One such test, OptiMAL(R), is based on the immunochromatographic detection of Plasmodium lactate dehydrogenase (pLDH) and has the capacity to detect and distinguish infections caused by P. falciparum and Plasmodium sp. This capacity is particularly important in countries where different species of Plasmodium co-exist. In this study we evaluated the performance of OptiMAL(R) in an urban referral center for malaria diagnosis. Two sets of patients were included: one (n = 112) having predetermined infections with P. falciparum or P. vivax and individuals with negative blood smears; and another consisting of all eligible consecutive patients (n = 80) consulting for diagnosis at the referral center during one month. The overall diagnostic efficiency of OptiMAL(R) for both sets of patients was 96.9%. Efficiency was higher for P. vivax (98.1%) than for P. falciparum (94.9%). These results corroborate the diagnostic utility of OptiMAL(R) in settings where P. vivax and P. falciparum co-exist and support its implementation where microscopic diagnosis is unavailable and in circumstances that exceed the capacity of the local microscopic diagnosis facility.
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PMID:Performance of OptiMAL(R) in the diagnosis of Plasmodium vivax and Plasmodium falciparum infections in a malaria referral center in Colombia. 1221 43


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