1,720,956 research outputs found
Development of molecular assays on Plasmodium falciparum gametocytes for functional analysis and novel diagnostics on malaria parasite transmission
Get PDFTransmission of P. falciparum malaria parasite from human host to mosquito is mediated by gametocytes in human peripheral blood. Both male and female gametocytes are required for the development of the parasite inside a female Anopheles mosquito. This work aims first to develop a molecular method for detecting gametocyte sex ratios as a parameter to predict parasite infectiousness to mosquito and then to investigate the effects of antimalarial compounds on gametocytes from natural infections. The results were compared with Direct Membrane Feeding Assay (DMFA) on mosquito data.
Two multiplex RTqPCR assays, targeting sex-specific transcripts (pfCCp4 and pfs25 for females, pfMGET for males), were developed for simultaneous assessment of male and female gametocytes. These assays were applied to three laboratory lines to measure their sex ratio by using two analytical approaches: the DCt and the TSEX RATIO. The results were compared with morphological sex ratios obtained by immunofluorescence assays (IFA). A linear relation exists between molecular parameters obtained in RTqPCT and the sex ratios determined by IFA analysis only in the lines NF54 and HB3 sel 4 lines but not in the case of the transgenic line pfDynGFP/P47mCherry. TSEX RATIO parameter represents a novel approach to track the copy number of sex-specific transcripts in a gametocyte population offering indirect insights into how the proportion of male and female gametocytes evolves over time and under various experimental conditions.
The above RTqPCR assays were used on gametocytes from infected individuals treated with gametocytocidal compounds to evaluate their effect on sex specific transcripts. The data of these assays were analyzed with ΔΔCt method. Molecular analysis performed after 24 hours of treatment did not align with DMFA outcomes. However, compound effects on transcript abundance became evident after an extended cultivation period of 48 hours following the 24 hours of treatment in NF54 gametocyte
An improved multiplex RT–quantitative PCR assay can reveal sex-specific activity of transmission-blocking drugs on ex vivo gametocytes from Plasmodium falciparum asymptomatic infections
No full textObjectives To develop a multiplex RT-quantitative PCR (RT-qPCR) assay to quantify sex-specific Plasmodium falciparum gametocyte transcripts (pfCCp4, pfMGET), for evaluating the impact of drug treatments on gametocyte viability for malaria transmission-blocking drug development. Methods We optimized an RT-qPCR assay incorporating a normalization transcript to use the & Delta;ΔCt method (differences in Cycle threshold) to quantify gametocyte transcript levels. The assay was used on ex vivo gametocytes from P. falciparum natural infections exposed for 24 h to six drugs impairing mosquito transmission, as measured by the direct membrane feeding assay. Follow-up in vitro experiments showed that an additional 48 h incubation, following drug wash-out, was required to monitor decline in transcript levels and potential sex-specific effects. Results The optimized assay revealed efficacy of drug treatment as a reduction in transcript levels for two of the six drugs tested: 30% for pfMGET and 80% for pfCCp4 in methylene blue (5 μM)-treated samples, and 75% for both sex-specific transcripts in samples treated with P218 (0.25 μM). In the remaining drugs, a 48 h incubation period post drug wash-out was required to measure a decline in transcript levels. Furthermore, a differential reduction in the levels of male versus female gametocyte transcripts suggested sex-specific effects for two of the drugs. Conclusions The multiplex RT-qPCR assay provides a reliable method to assess the inhibitory effects of drug treatments on P. falciparum gametocytes, with the potential to evaluate both overall and sex-specific impacts on gametocyte viability. This assay represents a valuable tool in the development and evaluation of transmission-blocking drugs, particularly in distinguishing effects on male and female gametocytes
Identification and preliminary characterization of Plasmodium falciparum proteins secreted upon gamete formation
Get PDFMalaria long-term elimination depends on parasite transmission control. Plasmodium sexual stage maturation in the mosquito, including egress from the host erythrocyte, is one of the prime targets for transmission-blocking interventions. This work aims to identify candidate molecules potentially involved in gamete emergence from the host erythrocyte, as novel transmission blocking targets. We analyzed by quantitative mass spectrometry the proteins released/secreted by purified Plasmodium falciparum gametocytes upon induction of gametogenesis. The proteome obtained showed a good overlap (74%) with the one previously characterized in similar conditions from gametocytes of the rodent malaria parasite P. berghei. Four candidates were selected based on comparative analysis of their abundance values in released vs total gametocyte proteome. We also characterized the P. falciparum orthologue of the microgamete surface protein (MiGS), a marker of male gametocyte secretory vesicles in murine models of malaria. The findings of this study reveal that all the selected candidate proteins are expressed in both genders and localize to vesicle-like structures that respond to gametogenesis stimuli. This result, together with the fact that the selected proteins are released during gamete emergence in both Plasmodium species, makes them interesting candidates for future functional studies to investigate their potential role in the gametogenesis process
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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