919 research outputs found
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
Mildred Coes Wasson Correspondence
No full textEntries include brief biographical information, a biography typed on green paper stationery describing Wasson\u27s authorship as grounded in the family history of her former husband David A. Wasson whose passing was causal to her writing of the Nancy books at the start of her writing career, typed book loan correspondence on the stationery of Frank D. Rowe, Superintendent of Schools, Warren, Maine, requesting The Big House by Wasson whom he had met on vacation with his mother, a fan, and a folded biographical letter sent to Maine state librarian Henry Ernest Dunnack that Wasson had sent to Frank D. Rowe\u27s mother in 1926 with a handwritten biographical note, a typed introductory letter to the Maine Author Collection in 1935, Wasson\u27s typed letter of regret on personal notepaper stationery concerning awarding free copies of her books to libraries, and typed correspondence from the Maine State Library on the acquisition of her books from the publisher and on receipt of the inscribed titles for the Maine Author Collection
Behaviour of buried pipelines subjected to external loading.
No full textThe research presented in this Thesis was carried out at the University of Sheffield under
the supervision of Dr I. C. Pyrah and Dr W. F. Anderson, and Mr G. Leach at British Gas
Engineering Research Station (ERS). The research was financially supported by a British
Gas Research Scholarship and by the Overseas Research Students Awards Scheme.
The Author would like to express his sincere gratitude to his supervisors for their invaluable
help, guidance and encouragement during the development of the research.
The Author is also grateful to Dr S. R. Mi for his interest and assistance throughout the
research. Special thanks also go to Dr S. J. Wheeler for his supervision during the first year
of the research and sound advice in the initial stage of the work.
The Author would like to express his gratitude to all members of the geotechnics group at
the University of Sheffield for the useful discussions and comments. Special thanks and
appreciation are extended to the staff at the ERS, particularly Mr E. Middleton for
providing the data of the field tests and constructive comments.
The laboratory tests were performed at ERS Soils Laboratory for which the Author is
thankful to the laboratory staff. The Author must also thank British Gas for providing the
computer hardware and software for performing the numerical analyses, and the printing
facilities to produce the Thesis. Thanks also go to Mr D. Reay and Mr B. Bellwood at the
Gas Research Centre of British Gas for ensuring continuous financial support throughout
the award period.
Finally, the Author wishes to thank his family and friends for their endless support and
encouragement throughout the period of study in the UK. Without them, this Thesis may
never have been completed
Identification of the Kna/Knb polymorphism and a method for Knops genotyping
No full textDNA mutations resulting in the McCoy and Swain-Langley polymorphisms have been identified on complement receptor 1 (CR1)-a ligand for rosetting of Plasmodium falciparum-infected RBCs. The molecular identification of the Kna/Knb polymorphism was sought to develop a genotyping method for use in the study of the Knops blood group and malaria
Hybrid Rowe cell for measurement of complex conductivity
No full textPeat is sediment consisting of incompletely decomposed organic matter deposited in swamp and marsh. It has served for a long time as benefits for human beings. Meanwhile, it has posed huge challenges to geotechnical engineers because of its unique characteristics such as anisotropy, low stiffness, high compressibility and strong creep susceptibility. In order to realise more effective and efficient site investigations, it is highly expected to apply geophysical techniques as well as core-boring, CPTs, sampling and laboratory tests because the techniques promise to be great contributions not only for two- or three-dimensional mapping but also for accurate interpretation of its physical, chemical and engineering properties in non-destructive way. Then, a new apparatus has been developed, called hybrid Rowe cell. It combines the functions of a traditional hydraulic cell and an electrical capacitor. This can simultaneously measure electrical properties and physical, mechanical and hydrological properties of soil samples, allowing to investigate their correlation accurately. This work focuses on the study of the applicability and calibration of the new hybrid cell, and the relationship between electrical conductivities of bulk peat and pore water which saturates the sample. The applicability of the hybrid cell was examined by using water as calibration. The results were then compared with values reported earlier and the experimental set-up was also compared with similar one found in literature. As a result, it was proven that the new cell successfully prevented electrode polarization and was applicable for this type of measurements. The electrical measurements on peat showed a relationship between the electrical conductivities of bulk peat and pore water which could be well predicted by a model previously developed for peat as well as the modified Archie’s law. In addition, the modified Archie’s law could be considered to be a persuasive model for the electrical behaviours observed in this study. For the future research, it is highly expected that the frequency of input currents is extended to lower range (< 20 Hz), input electric currents are properly controlled to avoid non-linear effects, and also hydraulic consolidation tests are performed in parallel with electrical measurements.Geo-EngineeringGeotechnologyCivil Engineering and Geoscience
Plasmodium falciparum:Rosettes do not protect merozoites from invasion-inhibitory antibodies
No full textRosetting is a parasite adhesion phenotype associated with severe malaria in African children. Why parasites form rosettes is unknown, although enhanced invasion or immune evasion have been suggested as possible functions. Previous work showed that rosetting does not enhance parasite invasion under standard in vitro conditions. We hypothesised that rosetting might promote invasion in the presence of host invasion-inhibitory antibodies, by allowing merozoites direct entry into the erythrocytes in the rosette and so minimising exposure to plasma antibodies. We therefore investigated whether rosetting influences invasion in the presence of invasion-inhibitory antibodies to MSP-1. We found no difference in invasion rates between isogenic rosetting and non-rosetting lines from two parasite strains, R29 and TM284, in the presence of MSP-1 antibodies (P = 0.62 and P = 0.63, Student's t test, TM284 and R29, respectively). These results do not support the hypothesis that rosettes protect merozoites from inhibitory antibodies during invasion. The biological function of rosetting remains unknown
Erythrocyte complement receptor 1 (CR1) expression level is not associated with polymorphisms in the promoter or 3' untranslated regions of the CR1 gene
No full textComplement receptor 1 (CR1) expression level on erythrocytes is genetically determined and is associated with high (H) and low (L) expression alleles identified by a HindIII restriction fragment-length polymorphism (RFLP) in intron 27 of the CR1 gene. The L allele confers protection against severe malaria in Papua New Guinea, probably because erythrocytes with low CR1 expression, are less able to form pathogenic rosettes with Plasmodium falciparum-infected erythrocytes. Despite the biological importance of erythrocyte CR1, the genetic mutation controlling CR1 expression level remains unknown. We investigated the possibility that mutations in the upstream or 3' untranslated regions of the CR1 gene could control erythrocyte CR1 level. We identified several novel polymorphisms; however, the mutations did not segregate with erythrocyte CR1 expression level or the H and L alleles. Therefore, high and low erythrocyte CR1 levels cannot be explained by polymorphisms in transcriptional control elements in the upstream or 3' untranslated regions of the CR1 gene
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
Identification of Plasmodium falciparum var1CSA and var2CSA domains that bind IgM natural antibodies
No full textMalaria in pregnancy is responsible for maternal anaemia, low-birth-weight babies and infant deaths. Plasmodium falciparum infected erythrocytes are thought to cause placental pathology by adhering to host receptors such as chondroitin sulphate A (CSA). CSA binding infected erythrocytes also bind IgM natural antibodies from normal human serum, a process that may facilitate placental adhesion or promote immune evasion. The parasite ligands that mediate placental adhesion are thought to be members of the variant erythrocyte surface antigen family P. falciparum erythrocyte membrane protein 1 (PfEMP1), encoded by the var genes. Two var gene sub-families, var1CSA and var2CSA, have been identified as parasite CSA binding ligands and are leading candidates for a vaccine to prevent pregnancy-associated malaria. We investigated whether these two var gene subfamilies implicated in CSA binding are also the molecules responsible for IgM natural antibody binding. By heterologous expression of domains in COS-7 cells, we found that both var1CSA and var2CSA PfEMP1 variants bound IgM, and in both cases the binding region was a DBL epsilon domain occurring proximal to the membrane. None of the domains from a control non-IgM-binding parasite (R29) bound IgM when expressed in COS-7 cells. These results show that PfEMP1 is a parasite ligand for non-immune IgM and are the first demonstration of a specific adhesive function for PfEMP1 epsilon type domains
Retrieving, Remapping and Rewriting Histories of British Art: Lubaina Himid's 'Revenge'
No full textThis chapter thinks about how one might begin to address a “remapping” of the boundaries of both “British” art and the concomitant practices of art history. Research into the visual resonances of Lubaina Himid's “Revenge” has taken the author on a visually, culturally, and historically rich journey that resists the closure that the concept of drawing conclusions seems to suggest. By attending to the content of her works and her divergent aesthetic strategies, the author hopes to be able to retrieve some of its legacies from the archives of the past, in the present, for the future. She also hopes to continue the dialogue with her work in the present in an attempt to rethink the borders, boundaries, and maps of British art's histories and concepts of national identity as constructed in the visual field
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