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

Although anopheline mosquitoes are important vectors of malaria, their genetic makeup has not yet been extensively investigated. The present studies concentrate on the genetic basis of esterases in Anopheles albinomanus. Nine zones of esterase activity activity have been resolved by gel electrophoresis. Four of these esterases: EST-2, EST-4, EST-6, and EST-8 are present throughout all developmental stages and also posess allelic variation. Mass matings were carried out with homozygous males and females heterozygous for two or more loci. The analyses of the progeny from single egg batches revealed that the four esterase systems mentioned above are encoded in separate loci with codominant allels. Analyses of two-point and three-point crosses have indicated the following linkage relationships: Est-8--12%--Est-4--22%--Est-2--9%--Est-6. The assignment of this linkage group to chromosome 3 has been accomplished by the use of a Y-2 chromosome translocation.
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PMID:Linkage relationships and chromosome assignment of four esterase loci in the mosquito Anopheles albimanus. 126 5

Sialic acid on human erythrocytes is involved in invasion by the human malaria parasite, Plasmodium falciparum. Mouse erythrocytes were used as a reagent to explore the question of whether erythrocyte sialic acid functions as a nonspecific negative charge or whether the sialic acid is a necessary structural part of the receptor for merozoites. Human erythrocytes contain N-acetylneuraminic acid (Neu5Ac), whereas mouse erythrocytes, which are also invaded by P. falciparum merozoites, contain 9-O-acetyl-N-acetylneuraminic acid (Neu5,9Ac2) and N-glycoloylneuraminic acid (Neu5Gc), in addition to Neu5Ac. We compared the effects of sialidase and influenza C virus esterase treatments of mouse erythrocytes on invasion and the binding of a 175-kDa P. falciparum protein (EBA-175), a sialic acid-dependent malaria ligand implicated in the invasion process. Sialidase-treated mouse erythrocytes were refractory to invasion by P. falciparum merozoites and failed to bind EBA-175. Influenza C virus esterase, which converts Neu5,9Ac2 to Neu5Ac, increased both invasion efficiency and EBA-175 binding to mouse erythrocytes. Thus, the parasite and EBA-175 discriminate between Neu5Ac and Neu5,9Ac2, that is, the C-9 acetyl group interferes with EBA-175 binding and invasion by P. falciparum merozoites. This indicates that sialic acid is part of a receptor for invasion.
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PMID:Binding of Plasmodium falciparum 175-kilodalton erythrocyte binding antigen and invasion of murine erythrocytes requires N-acetylneuraminic acid but not its O-acetylated form. 156 37

Analysis of restriction fragment length polymorphism (RFLP) is a powerful tool for analyzing linkage relationships in species where few genetic markers have been described and where conduct of crosses is difficult. It also permits integration of genetic and physical (cytogenetic) data when the probes have been mapped by in situ hybridization. To illustrate the utility of the method, and because some mutations of a diphenol oxidase gene might conceivably produce the malaria refractoriness phenotype of ookinete-oocyst encapsulation, backcrosses between two inbred lines of Anopheles gambiae Giles were carried out to determine the linkage relationship between the diphenol oxidase A2 (Dox) gene and the esterase locus associated with refractoriness to Plasmodium cynomolgi NIH. The Dox alleles were a Sal I restriction fragment length polymorphism visualized by probing Southern blotted DNA from portions of individual mosquitoes with a cloned Dox gene probe. The two genes were shown to segregate independently.
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PMID:Use of a restriction fragment length polymorphism (RFLP) as a genetic marker in crosses of Anopheles gambiae (Diptera: Culicidae): independent assortment of a diphenol oxidase RFLP and an esterase locus. 167 45

In a genetically selected strain of the malaria vector Anopheles gambiae, most species of Plasmodium parasites are surrounded by melanized capsules and killed in the wall of the mosquito midgut. Genetic studies demonstrate a significant association between the refractory response to Plasmodium cynomolgi B strain and the Est A allele at an autosomal esterase locus. Increased susceptibility to parasites is associated with an alternate Est C allele. Lines selected to be homozygous for the Est A and Est C alleles show enhanced levels of refractoriness and susceptibility when compared to the unselected parental stock. Expression of the refractory phenotype is reduced much more than the susceptible phenotype at high parasite density, suggesting that refractoriness may be due to a positive effector.
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PMID:Association of a Plasmodium-refractory phenotype with an esterase locus in Anopheles gambiae. 274 37

The level of resistance to infection in inbred mice with the murine malaria species Plasmodium chabaudi AS is genetically determined. Resistant C57BL/6, which are able to eliminate the parasite by 4 weeks, develop marked splenomegaly and survive the infection. Susceptible A/J mice, which succumb to infection (mean survival time = 10 days), develop only minimal splenomegaly. In order to determine if gross differences in the organization, number, and type of spleen cells are related to the outcome of infection with P. chabaudi AS, the development of splenomegaly was examined by enzyme and immunohistochemical methods during the first week after infection. Cryostat sections of spleens removed from normal animals of both strains and at 4 and 7 days after intraperitoneal infection with 10(6) parasitized erythrocytes were stained for enzyme (acid phosphatase and nonspecific esterase) and immunohistochemistry with conventional monoclonal antibodies against T cells, B cells, and macrophages as well as with novel rat anti-mouse monoclonal antibodies which define discrete subpopulations of macrophages in the mouse spleen. The livers of normal and infected animals of each strain were also examined. The results of this study demonstrate (1) differences between normal, uninfected B6 and A/J mice in the organization and number of one subpopulation of macrophages in the spleen, the marginal metallophilic macrophages, and (2) marked histological changes in the spleen and liver during the course of infection in both resistant C57BL/6 and susceptible A/J mice. These changes include depletion of cells from the marginal zone of the spleen which, in the case of the marginal metallophilic macrophages, appears to be more severe in susceptible A/J mice.
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PMID:Histological changes in the spleen and liver of C57BL/6 and A/J mice during Plasmodium chabaudi AS infection. 278 81

Reduced fenitrothion susceptibility in Haitian Anopheles albimanus is documented using time/mortality measurements from otherwise standard World Health Organization (WHO) bioassays. Survival beyond a time threshold in bioassays is shown to be highly correlated with elevated non-specific esterase levels. A shift in resistance incidence from less than 20 to over 60% in a six-month period is documented using both the bioassay and microassay procedures, showing the potential of microplate assay methods in early detection of resistance. Conventional 24-hour reading of WHO bioassay data failed to detect resistance until the level reached 60%. Resistance appeared to be focal, with an increase in intensity coinciding with a fenitrothion spray cycle for malaria control.
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PMID:Microplate assay analysis of reduced fenitrothion susceptibility in Haitian Anopheles albimanus. 319 11

To facilitate investigations of the consequences of malarial infection during human pregnancy, several methods for the recognition of pigment and parasites in the placenta were evaluated. Pigment was visualized in infected blood smears and placental tissue using both white light and modified fluorescence microscopy. However, the characteristic pigment dots observed with fluorescent light were also apparent in unstained cryostat and deparaffinized placental sections, and following reaction with immunohistological reagents. Intact parasites were recognized immunohistologically in placental sections and blood smears using rabbit antisera to Plasmodium falciparum and P. berghei. Using these procedures, numerous erythrocytes containing parasites associated with small pigment dots were seen in intervillous spaces in heavily infected placentae. In these organs, larger irregular pigment aggregates were present within maternal cells which were shown to be monocytes by esterase staining. Pigment was also observed in the cytoplasm of the trophoblast and not infrequently in the mesenchymal stroma, but no intact parasites were observed within chorionic villi. These simple and sensitive methods thus confirm placental localization of parasites and pigment. Furthermore, the finding of pigment in all Gambian placentae examined, of which seven were thought initially to be uninfected, indicates that malaria may complicate pregnancy more frequently than hiterto anticipated.
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PMID:The human materno-foetal relationship in malaria: I. Identification of pigment and parasites in the placenta. 615 2

The change from larval to adult mosquito control in the Gezira area of Sudan resulted in a decrease in the prevalence of malaria in this region. House spraying with malathion began in 1975 and resistance to this compound was first detected in 1978. Laboratory tests showed that adult Anopheles arabiensis Patton were resistant to malathion and phenthoate but susceptible to all other organophosphates tested. The larvae of this strain were susceptible to malathion. The malathion resistance in the adults was synergized by triphenyl phosphate, but not by piperonyl butoxide. This suggests that a carboxylesterase enzyme may be the basis of malathion resistance in this strain. Analysis of general esterase levels to alpha- and beta-naphthyl acetate showed that there was no quantitative change in the amount of carboxylesterase enzyme present in the resistant strain as compared to the susceptible. The absence of larval resistance suggests that house spraying rather than agricultural spraying is the major source of selection pressure. The presence of a high level of adult malathion resistance in A. arabiensis may decrease the efficacy of malathion for malaria control in Sudan. The lack of cross-resistance to organophosphates which do not contain a carboxylester bond means that insecticides such as fenitrothion are still practical alternatives.
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PMID:Biochemical studies on malathion resistance in Anopheles arabiensis from Sudan. 663 75

Three taxa of the malaria mosquito Anopheles balabacensis complex representing three geographical regions (Thailand, Peninsular Malaysia and Sabah) in Southeast Asia, were analysed for genetic variation at 15 gene-enzyme systems. The Sabah taxon was monomorphic for all the 15 gene-enzyme systems. Only two gene-enzyme systems (esterase and glucose phosphate isomerase) were variable in the Thailand and Peninsular Malaysia taxa. The average heterozygosity or gene diversity was 0.007 for the Thailand taxon and 0.028 for the Peninsular Malaysia (Perlis) taxon. There were no unique gene-enzyme markers in the three taxa studied. The average values of genetic identities (0.933-0.997) and genetic distances (0.003-0.069) indicate that these three taxa are of subspecific status.
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PMID:Biochemical genetic relationship in three taxa of the malaria mosquito Anopheles balabacensis complex. 664 Nov 78

The effect of concomitant toxoplasma and malaria infection on the reticuloendothelial system was investigated in rats. This was evaluated by the level of plasmodial parasitaemia; humoral antibody response; effect on splenic weight; histopathological changes in thymus and spleen; histopathological and histochemical changes in liver. The parasitaemia appeared after 2 days in single malaria and concomitant infections. The peak was reached after 6 days with single and precedent malaria, and after 10 days with precedent toxoplasma. The clearance of parasitaemia was delayed to 30 days with concomitant infections instead of 14 days with single malaria. Higher than normal malarial antibody levels were reached with precedent toxoplasma, while the toxoplasma antibodies were lower than normal in both concomitant infections. There was a significant increase in splenic weight in both precedent malaria and toxoplasma, followed by a decrease which did not return to normal in case of precedent malaria. The thymus was packed with thymocytes in precedent malaria, while depletion in the cortex occurred in precedent toxoplasma. In the liver, there was glycogen depletion and decrease in succinic dehydrogenase activity in both concomitant infections. Choline esterase activity in precedent malaria was decreased and returned to normal on day 40 while in precedent toxoplasma the activity was normal all through the period. The alkaline phosphatase activity was decreased and returned to normal on day 40 in both concomitant infections.
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PMID:Experimental concomitant toxoplasma and malaria infection in rats. 674 2


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