282 research outputs found
Sequestration in Plasmodium falciparum malaria: sticky cells and sticky problems.
No full textPlasmodium falciparum is unique among the human malarias in displaying the phenomenon of sequestration, in which mature infected erythrocytes adhere to post-capillary and capillary venular endothelium. In this review, Tony Berendt, David Ferguson and Chris Newbold describe the molecular and cellular biology of sequestration and cytoadherence. Potential host receptors identified to date that are expressed on endothelial cells (CD36, thrombospondin and ICAM-1) and the parasite-mediated changes in the infected erythrocyte (knob formation, senescence and the expression of parasite-derived neoantigens) are considered as well as the relevance of sequestration as a virulence factor in human disease and its potential role in parasite biology
A well-conserved Plasmodium falciparum var gene shows an unusual stage-specific transcript pattern
No full textThe var multicopy gene family encodes Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) variant antigens, which, through their ability to adhere to a variety of host receptors, are thought to be important virulence factors. The predominant expression of a single cytoadherent PfEMP1 type on an infected red blood cell, and the switching between different PfEMP1 types to evade host protective antibody responses, are processes thought to be controlled at the transcriptional level. Contradictory data have been published on the timing of var gene transcription. Reverse transcription-polymerase chain reaction (RT-PCR) data suggested that transcription of the predominant var gene occurs in the later (pigmented trophozoite) stages, whereas Northern blot data indicated such transcripts only in early (ring) stages. We investigated this discrepancy by Northern blot, with probes covering a diverse var gene repertoire. We confirm that almost all var transcript types were detected only in ring stages. However, one type, the well-conserved varCSA transcript, was present constitutively in different laboratory parasites and does not appear to undergo antigenic variation. Although varCSA has been shown to encode a chondroitin sulphate A (CSA)-binding PfEMP1, we find that the presence of full-length varCSA transcripts does not correlate with the CSA-binding phenotype
Protection, pathogenesis and phenotypic plasticity in Plasmodium falciparum malaria.
No full textWhy does Plasmodium falciparum cause severe illness in some but not all infections? How is clinical immunity acquired? These questions have intrigued investigators since the clinical epidemiology of malaria was first described. The search for answers to both questions has highlighted the changes that take place at the surface of infected red blood cells during the last half of the erythrocytic cycle. These changes specify the antigenic and adhesive or cytoadherence phenotypes for the infected cell. Now the antigenic and adhesive phenotypes appear to be linked and together undergo clonal variation. In this article David Roberts, Beverley-Ann Biggs, Graham Brown and Christopher Newbold explain how clonal phenotypic variation and the linkage between adhesive and antigenic types contribute to our understanding of naturally acquired immunity and of pathogenesis of severe malaria
A comprehensive approach to health literacy: validating the All Aspects of Health Literacy Scale in a respresentative sample of Arabic-speaking adult Syrian refugees
No full textMASTER OF SCIENCE (2017), McMaster University, Hamilton ON (Department of Global Health)
TITLE: A comprehensive approach to health literacy: validating the all aspects of health literacy scale (AAHLS) in a representative sample of Arabic-speaking adult Syrian refugees
AUTHOR: Raafia Siddiqui, BSc Hons. (York University, 2014)
SUPERVISOR: Dr. K. Bruce Newbold
NUMBER OF PAGES: vii, 92The purpose of this study is to quantify current health literacy levels amongst a segment of the Syrian refugee population in Canada by translating and validating an existing comprehensive health literacy assessment tool, the All Aspects of Health Literacy Scale (AAHLS) into Arabic. This study (1) determined functional, communicative and critical health literacy levels amongst Syrian refugees. Functional and critical health literacy was comparatively low but respondents seemed able to effectively communicate with their providers and access supports to read and fill in health documents. Significant correlates of low health literacy were presence of long-term health conditions and place of origin (country versus refugee camp). This study also validated the AAHLS in Arabic-speaking Syrian refugees, with a Cronbach’s alpha of 0.67 for the overall scale and 0.63 for health literacy items. The overall scale had high content validity. The feasibility of this instrument as a self-administered screening tool in clinical or community settings was demonstrated with a high response rate of 0.86.ThesisMaster of Science (MSc)Health literacy looks at an individual's ability to read, understand and interpret health information and ultimately use it to exert greater control over their health. The purpose of this study is to understand the factors that influence health literacy levels amongst a segment of the Syrian refugee population in Canada by translating and validating an existing comprehensive health literacy assessment tool, the All Aspects of Health Literacy Scale (AAHLS) into Arabic. This study (1) determined functional (reading and filling in health documents), communicative (speaking to health providers) and critical health (assessing the relevance and appropriateness of health information) literacy levels amongst Syrian refugees. Functional and critical health literacy was comparatively low but respondents seemed able to effectively communicate with their providers and access supports to read and fill in health documents. Low health literacy was associated with having a long-term health conditions and staying in a refugee camp. This study found the translated AAHLS to be reliable, with a Cronbach’s alpha of 0.67 for the overall scale and 0.63 for health literacy items. The overall scale had high content validity. The feasibility of this instrument as a self-administered screening tool in clinical or community settings was demonstrated with a high response rate of 0.86
Thyroid cancer: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up
No full textThis ESMO Clinical Practice Guidelines provide updated state-of-the-art recommendations on management of thyroid cancer (diagnosis, treatment and follow-up), compiled by a multidisciplinary author panel and accompanied by level of evidence and grade of recommendation, depending on the strength of supporting data and magnitude of benefit from particular intervention
The role of Plasmodium falciparum var genes in malaria in pregnancy
No full textSequestration of Plasmodium falciparum-infected erythrocytes in the placenta is responsible for many of the harmful effects of malaria during pregnancy. Sequestration occurs as a result of parasite adhesion molecules expressed on the surface of infected erythrocytes binding to host receptors in the placenta such as chondroitin sulphate A (CSA). Identification of the parasite ligand(s) responsible for placental adhesion could lead to the development of a vaccine to induce antibodies to prevent placental sequestration. Such a vaccine would reduce the maternal anaemia and infant deaths that are associated with malaria in pregnancy. Current research indicates that the parasite ligands mediating placental adhesion may be members of the P. falciparum variant surface antigen family PfEMP1, encoded by var genes. Two relatively well-conserved subfamilies of var genes have been implicated in placental adhesion, however, their role remains controversial. This review examines the evidence for and against the involvement of var genes in placental adhesion, and considers whether the most appropriate vaccine candidates have yet been identified
Structural change and unit roots
No full textThis thesis contains a discussion of three problems related to structural changes and unit-roots in time-series analysis. First, it is shown under which conditions it is possible to consistently estimate the break date in a model with one structural break. It is also shown that when the errors have a unit-root, it is possible to spuriously estimate a break when there is none. Second, the same issues are discussed with respect to estimating the number of breaks. Finally, it is considered the problem of testing for unit-roots in the presence of structural breaks. New evidence is presented for the Nelson-Plosser macroeconomic data that strongly weaken recent results that reject the unit-root hypothesis for these series.Made available in DSpace on 2011-05-07T14:25:05Z (GMT). No. of bitstreams: 2
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CR1 Knops blood group alleles are not associated with severe malaria in the Gambia
No full textThe Knops blood group antigen erythrocyte polymorphisms have been associated with reduced falciparum malaria-based in vitro rosette formation (putative malaria virulence factor). Having previously identified single-nucleotide polymorphisms (SNPs) in the human complement receptor 1 (CR1/CD35) gene underlying the Knops antithetical antigens Sl1/Sl2 and McC(a)/McC(b), we have now performed genotype comparisons to test associations between these two molecular variants and severe malaria in West African children living in the Gambia. While SNPs associated with Sl:2 and McC(b+) were equally distributed among malaria-infected children with severe malaria and control children not infected with malaria parasites, high allele frequencies for Sl 2 (0.800, 1,365/1,706) and McC(b) (0.385, 658/1706) were observed. Further, when compared to the Sl 1/McC(a) allele observed in all populations, the African Sl 2/McC(b) allele appears to have evolved as a result of positive selection (modified Nei-Gojobori test Ka-Ks/s.e.=1.77, P-valu
State-dependent model, multi-step-ahead, multiple forecasts: Experience with the United States unemployment rate series
No full textThis study develops a framework for the fitting, analysis, and forecasting of linear and nonlinear time series models. Through Priestley's State Dependent Model and the Kalman filter algorithm, linear, nonlinear and nonstationary models have been fitted to the US unemployment rate series. The algorithm has been extended to account for both nonlinearity and nonstationarity. Also, some of the existing tests for linearity in the time domain have been applied and indicate the existence of bilinear type nonlinearity in the series. Models fitted in the state dependent framework and the bilinear models have been used for one to twelve step ahead forecasting. The models fitted in the state dependent framework outperform other models, and the bilinear models outperform the linear model. The performance of the existing forecast accuracy comparison tests has been analyzed empirically and through simulation. An alternative to the Diebold and Mariano test has been suggested, which appears to have better size than the Diebold and Mariano test.Made available in DSpace on 2011-05-07T12:51:49Z (GMT). No. of bitstreams: 2
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Time series analysis of macroeconometric constructs
No full textThis thesis addresses the issue of estimating persistence of economic shocks using time series models. First, it is shown that the log likelihood function for ARIMA models is not strictly quadratic with respect to the persistence estimate. This result explains why the persistence literature has attained conflicting results. In addition, nonparametric estimates of persistence based on the variance ratio are analyzed. It is found that the distribution of the variance ratio statistic depends upon the data generating process of ARIMA models, and that the variance ratio for log U.S. GNP falls within the bounds of simulated variance ratios for models with persistence of zero and persistence greater than one. However, a model adequacy test based on the variance ratio is derived for ARIMA(p, 1, q) model specification; the distribution of the test statistic does not depend upon unknown model parameters. Finally, persistence is analyzed within a multivariate framework. A permanent/transitory components model representation is found for a bivariate vector autoregression for log U.S. GNP and unemployment rates. It is found that there is considerable uncertainty about both the persistence of the permanent component and the implied univariate persistence for even lightly parameterized vector autoregression models.Made available in DSpace on 2011-05-07T12:33:54Z (GMT). No. of bitstreams: 2
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