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Find video protocols related to scientific articles indexed in Pubmed.
Genetic diversity and signatures of selection of drug resistance in Plasmodium populations from both human and mosquito hosts in continental Equatorial Guinea.
Malar. J.
PUBLISHED: 03-15-2013
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In Plasmodium, the high level of genetic diversity and the interactions established by co-infecting parasite populations within the same host may be a source of selection on pathogen virulence and drug resistance. As different patterns have already been described in humans and mosquitoes, parasite diversity and population structure should be studied in both hosts to properly assess their effects on infection and transmission dynamics. This study aimed to characterize the circulating populations of Plasmodium spp and Plasmodium falciparum from a combined set of human blood and mosquito samples gathered in mainland Equatorial Guinea. Further, the origin and evolution of anti-malarial resistance in this area, where malaria remains a major public health problem were traced.
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The origins of African Plasmodium vivax; insights from mitochondrial genome sequencing.
PLoS ONE
PUBLISHED: 06-01-2011
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Plasmodium vivax, the second most prevalent of the human malaria parasites, is estimated to affect 75 million people annually. It is very rare, however, in west and central Africa, due to the high prevalence of the Duffy negative phenotype in the human population. Due to its rarity in Africa, previous studies on the phylogeny of world-wide P. vivax have suffered from insufficient samples of African parasites. Here we compare the mitochondrial sequence diversity of parasites from Africa with those from other areas of the world, in order to investigate the origin of present-day African P. vivax. Mitochondrial genome sequencing revealed relatively little polymorphism within the African population compared to parasites from the rest of the world. This, combined with sequence similarity with parasites from India, suggests that the present day African P. vivax population in humans may have been introduced relatively recently from the Indian subcontinent. Haplotype network analysis also raises the possibility that parasites currently found in Africa and South America may be the closest extant relatives of the ancestors of the current world population. Lines of evidence are adduced that this ancestral population may be from an ancient stock of P. vivax in Africa.
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Duffy negative antigen is no longer a barrier to Plasmodium vivax--molecular evidences from the African West Coast (Angola and Equatorial Guinea).
PLoS Negl Trop Dis
PUBLISHED: 04-17-2011
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Plasmodium vivax shows a small prevalence in West and Central Africa due to the high prevalence of Duffy negative people. However, Duffy negative individuals infected with P. vivax have been reported in areas of high prevalence of Duffy positive people who may serve as supply of P. vivax strains able to invade Duffy negative erythrocytes. We investigated the presence of P. vivax in two West African countries, using blood samples and mosquitoes collected during two on-going studies.
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SLC40A1 Q248H allele frequencies and associated SLC40A1 haplotypes in three West African population samples.
Ann. Hum. Biol.
PUBLISHED: 01-14-2011
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Ferroportin is a transmembrane protein responsible for iron export from enterocytes and macrophages. Mutation c.744G ? T (Q248H), located in exon 6 of the ferroportin gene SLC40A1, is found as a polymorphism in populations of African origin. This mutation has been extensively analysed in African-Americans, but poorly studied in native African populations.
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Mosquito fauna on the Cape Verde Islands (West Africa): an update on species distribution and a new finding.
J. Vector Ecol.
PUBLISHED: 12-24-2010
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To evaluate the risk of transmission of vector-borne diseases, regular updates of the geographic distribution of insect vectors are required. In the archipelago of Cape Verde, nine mosquito species have been reported. Of these, four are major vectors of diseases that have been present in the archipelago: yellow fever, lymphatic filariasis, malaria and, currently, an outbreak of dengue. In order to assess variation in mosquito biodiversity, we have carried out an update on the distribution of the mosquito species in Cape Verde, based on an enquiry of 26 unpublished technical reports (1983-2006) and on the results of an entomological survey carried out in 2007. Overall, there seems to be a general trend for an expansion of biological diversity in the islands. Mosquito species richness was negatively correlated with the distance of the islands from the mainland but not with the size of the islands. Human- and/or sporadic climatic-mediated events of dispersal may have contributed to a homogenization of species richness regardless of island size but other ecological factors may also have affected the mosquito biogeography in the archipelago. An additional species, Culex perexiguus, was collected for the first time in the archipelago during the 2007 survey.
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Two nonrecombining sympatric forms of the human malaria parasite Plasmodium ovale occur globally.
J. Infect. Dis.
PUBLISHED: 04-13-2010
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Malaria in humans is caused by apicomplexan parasites belonging to 5 species of the genus Plasmodium. Infections with Plasmodium ovale are widely distributed but rarely investigated, and the resulting burden of disease is not known. Dimorphism in defined genes has led to P. ovale parasites being divided into classic and variant types. We hypothesized that these dimorphs represent distinct parasite species.
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Plasmodium vivax in the Democratic Republic of East Timor: Parasite prevalence and antifolate resistance-associated mutations.
Acta Trop.
PUBLISHED: 04-08-2010
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In the Democratic Republic of East Timor, Plasmodium falciparum and Plasmodium vivax malaria coexist, but limited information is available about the latter species. Consequently, the prevalence of P. vivax and of its corresponding antifolate resistance-associated mutations in the pvdhfr and pvdhps genes was assessed here. Blood samples were collected from 650 individuals distributed among six districts, over two different periods, by either passive case detection (PCD) or active case detection (ACD). As expected, malaria was over-represented in the PCD sample (26% PCD vs 5% ACD), because the infection increases medical care seeking. Additionally, the relative frequency of P. vivax infections in symptomatic individuals (37%) was twice as high as the one in the asymptomatic sampling group (18%), suggesting that that this parasite is accounting for a significant proportion malaria-attributed morbidity. The frequency of specific sulfadoxine-pyrimethamine resistance-associated mutations genes was ascertained in P. vivax positive samples by PCR-RFLP. Although no mutants were detected in codons 383 and 553 of pvdhps, 48%, 76% and 82% of P. vivax-infected samples harbored the dhfr 33L, 58R and 117N mutations, respectively. Additionally, the frequency of parasites carrying both pvdhfr 58R and 117N mutant alleles accounted for a third of all genotypes analyzed, most likely due to inadvertent SP use in the past. In conclusion, evidence-based information is provided to promote optimized drug deployment and limit the evolution of resistance to antifolate resistance in P. vivax from East Timor.
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Malaria: looking for selection signatures in the human PKLR gene region.
Br. J. Haematol.
PUBLISHED: 04-04-2010
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The genetic component of susceptibility to malaria is both complex and multigenic and the better-known protective polymorphisms are those involving erythrocyte-specific structural proteins and enzymes. In vivo and in vitro data have suggested that pyruvate kinase deficiency, which causes a nonspherocytic haemolytic anaemia, could be protective against malaria severity in humans, but this hypothesis remains to be tested. In the present study, we conducted a combined analysis of Short Tandem Repeats (STRs) and Single Nucleotide Polymorphisms (SNPs) in the pyruvate kinase-encoding gene (PKLR) and adjacent regions (chromosome 1q21) to look for malaria selective signatures in two sub-Saharan African populations from Angola and Mozambique, in several groups with different malaria infection outcome. A European population from Portugal, including a control and a pyruvate kinase-deficient group, was used for comparison. Data from STR and SNP loci spread along the PKLR gene region showed a considerably higher differentiation between African and Portuguese populations than that usually found for neutral markers. In addition, a wider region showing strong linkage disequilibrium was found in an uncomplicated malaria group, and a haplotype was found to be associated with this clinical group. Altogether, this data suggests that malaria selective pressure is acting in this genomic region.
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Analysis of malaria associated genetic traits in Cabo Verde, a melting pot of European and sub Saharan settlers.
Blood Cells Mol. Dis.
PUBLISHED: 07-31-2009
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Malaria has occurred in the Cabo Verde archipelago with epidemic characteristics since its colonization. Nowadays, it occurs in Santiago Island alone and though prophylaxis is not recommended by the World Health Organization, studies have highlight the prospect of malaria becoming a serious public health problem as a result of the presence of antimalarial drug resistance associated with mutations in the parasite populations and underscore the need for tighter surveillance. Despite the presumptive weak immune status of the population, severe symptoms of malaria are not observed and many people present a subclinical course of the disease. No data on the prevalence of sickle-cell trait and red cell glucose-6-phosphate dehydrogenase deficiency (two classical genetic factors associated with resistance to severe malaria) were available for the Cabo Verde archipelago and, therefore, we studied the low morbidity from malaria in relation to the particular genetic characteristics of the human host population. We also included the analysis of the pyruvate kinase deficiency associated gene, reported as putatively associated with resistance to the disease. Allelic frequencies of the polymorphisms examined are closer to European than to African populations and no malaria selection signatures were found. No association was found between the analyzed human factors and infection but one result is of high interest: a linkage disequilibrium test revealed an association of distant loci in the PKLR gene and adjacent regions, only in non-infected individuals. This could mean a more conserved gene region selected in association to protection against the infection and/or the disease.
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Analysis of genetic mutations associated with anti-malarial drug resistance in Plasmodium falciparum from the Democratic Republic of East Timor.
Malar. J.
PUBLISHED: 04-09-2009
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In response to chloroquine (CQ) resistance, the policy for the first-line treatment of uncomplicated malaria in the Democratic Republic of East Timor (DRET) was changed in early 2000. The combination of sulphadoxine-pyrimethamine (SP) was then introduced for the treatment of uncomplicated falciparum malaria.
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Analysis of TPI gene promoter variation in three sub-Saharan Africa population samples.
Am. J. Hum. Biol.
PUBLISHED: 03-04-2009
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Population samples from Angola, Mozambique, and S. Tomé e Príncipe were screened for the TPI gene promoter variants -5A-->G, -8G-->A and -24T-->G. Three haplotypes were identified in the three populations: the haplotype -5A-8G-24T (average frequency 65.3%) and two less common haplotypes -5G-8G-24T (average frequency 24.7%) and -5G-8A-24T (average frequency 10.0%). A population sample from Central Portugal showed the haplotype -5A-8G-24T in 139 chromosomes and one subject heterozygous for haplotype -5G-8A-24G. The exact test of sample differentiation among three groups of malaria-infected individuals classified according to the severity of the disease showed no significant differences. We confirmed TPI gene diversity in sub-Saharan Africa, but we could not detect any association between TPI promoter variation and a malarial protective effect. Larger scale epidemiological studies are thus required to clarify this putative mechanism of natural host defense against this worldwide public health problem.
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Pyruvate kinase deficiency in sub-Saharan Africa: identification of a highly frequent missense mutation (G829A;Glu277Lys) and association with malaria.
PLoS ONE
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Pyruvate kinase (PK) deficiency, causing hemolytic anemia, has been associated to malaria protection and its prevalence in sub-Saharan Africa is not known so far. This work shows the results of a study undertaken to determine PK deficiency occurrence in some sub-Saharan African countries, as well as finding a prevalent PK variant underlying this deficiency.
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JoVE Visualize is a tool created to match the last 5 years of PubMed publications to methods in JoVE's video library.

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In developing our video relationships, we compare around 5 million PubMed articles to our library of over 4,500 methods videos. In some cases the language used in the PubMed abstracts makes matching that content to a JoVE video difficult. In other cases, there happens not to be any content in our video library that is relevant to the topic of a given abstract. In these cases, our algorithms are trying their best to display videos with relevant content, which can sometimes result in matched videos with only a slight relation.