Malaria is a global pandemic that affects millions of people each year. It is a parasitic infection caused by the Plasmodium family, with Plasmodium falciparum being the most virulent strain. Malaria is transmitted to humans by the female Anopheles mosquito. The parasite undergoes two different cycles of its life cycle within the human host: the liver and intraerythrocytic life cycle. The latter consists of an asexual and sexual cycle. The intraerythrocytic cycle is perhaps the most important stage of the parasite's life cycle as it promotes the spread of the disease within and between hosts. The focus of this investigation was aimed at the invasion process of the merozoites into the erythrocytes. The Plasmodium merozoite utilises a cascade of proteins during the erythrocyte invasion process, which is a swift action that takes place in approximately 30 seconds. A number of surface proteins are expressed during merozoite development and are distributed along the merozoite surfaces to assist with attachment and invasion, the most crucial being MSP-1, AMA-1 and RON-2. MSP-1 and AMA-1 are vital targets for the development of malaria vaccines. AMA-1 is the central target protein of this investigation as it plays an essential role in the invasion process. AMA-1 commits the merozoite to invade the erythrocyte, as it assists the RON proteins in the formation of an irreversible tight-junction with the membrane of the erythrocyte. Antibodies, specific to AMA-1, bind to the protein, which prevents the formation of the tight junction and inhibits the invasion of the merozoite into the erythrocyte, therefore preventing the spread of the disease. However, before invasion, AMA-1 undergoes a number of proteolytic processes. It is synthesized as an 83 kDa (AMA-183) precursor protein in the apical organelle of the merozoite. This is then cleaved at the N-terminus to give rise to a 66 kDa (AMA-166) fragment, which is secreted onto the surface of the merozoite. The AMA-166 fragment is then cleaved into either a 48 kDa (AMA-148) or 44 kDa (AMA-144) fragment. One of these three fragments is then used by the merozoite for erythrocyte invasion. The aim of this investigation was to isolate and characterise each of the fragments of the Plasmodium falciparum AMA-1 (PfAMA-1) protein using the 3D7 lab strain of P. falciparum and to visualise the merozoite-erythrocyte invasion process, to possibly identify which of the AMA-1 fragments are involved in the invasion process. In order to achieve this large clusters of merozoites from sorbitol-synchronised cultures were isolated. Schizonts were isolated from culture by magnetic separation and incubated with E64 to prevent the release of merozoites. Merozoites that were required for the isolation of PfAMA-1 were harvested from the schizonts by saponin lysis, then homogenised, separated by SDS-PAGE and digested for LC-MS/MS analysis. Merozoites that were required for the visualisation procedures were not incubated with E64, to allow natural egression from the erythrocyte. The transmission electron microscopy results produced clear images of the merozoiteerythrocyte invasion process and the positioning of PfAMA-1 on the merozoite, before and after schizont rupture, was visualised from results obtained from confocal microscopy. Then PfAMA-1 was identified in isolated merozoite samples by LC-MS/MS analysis. However, due to its low abundance, isolation of high enough concentrations of PfAMA-1 to characterise its different fragments was not achieved. Further investigation into the development of the culturing and isolating methods could help in future projects aimed at isolating higher concentrations of merozoite proteins from synchronised cultures with a lower merozoite egression window period, in order to accomplish detailed analysis on invading proteins for the future development of treatments against malaria. / Dissertation (MSc)--University of Pretoria, 2016. / Pharmacology / MSc / Unrestricted

This thesis explores potential seeding techiniques to limit harmful effects of preemergent herbicide on a seeded species while simultaneously reducing abudance of annual invasive grasses. The first chapter examines the use of activated carbon seed coatings and furrows to limit herbicide effect on seeds of a perrenial bunchgrass. We found that both carbon coatings and furrows mitigated some of the herbicide effects, but that only when the two techniques were combined did we observe unaffected seedling emergence, plant density, and aboveground growth. Therefore, we suggest to management that use of carbon coatings and furrows after herbicide application can likely be used to reduce invasive annual grasses while simultaneously establishing a native bunchgrass. In chapter 2, we examine the effects of a novel preemergent herbicide indaziflam, on native seeds and compare it against a common preemergent herbicide, imazapic. We found that indaziflam provides superior long-term control of annual invasive grasses than imazapic, but that it is also more detrimental to native seeds. Our results suggest that indaziflam is best suited for control purposes only, and is hard to incorporate in restoration seeding efforts due to its strong effects on native seed.

Phalaris arundinacea L. is an aggressive species that can dominate wetlands by producing monotypic stands that suppress native vegetation. In this study invasion windows were created for native species in monotypic stands of P. arundinacea with either fire or herbicide. Three native species groups, herbaceous plants, herbaceous seeds, and woody shrubs, were planted into plots burned or treated with herbicide in the early spring. Fire did not create an effective invasion window for native species; there was no difference in P. arundinacea root and shoot biomass or cover between burned and control plots (p ≥ 0.998). Herbicide treatment created an invasion window for native species by reducing P. arundinacea root and shoot biomass for two growing seasons, but that invasion window was fast closing by the end of the second growing season because P. arundinacea shoot biomass had nearly reached the shoot biomass levels in the control plots (p = 0.053). Transplant mortality, frost, and animal herbivory prevented the herbaceous species and woody seedlings from becoming fully established in the plots treated with herbicide during the first year of the experiment. Transplanted monocots had a greater survival than dicots. By the second growing season the herbaceous group had the greatest mean areal cover (5%), compared to the woody seedlings (3%) and seed group (0%). Long-term monitoring of the plots will determine whether the herbaceous transplants will compete effectively with P. arundinacea and whether the woody species will survive, shade the P. arundinacea, and accelerate forest succession.

No description available.

Invasive plants are widely cited as a major threat to native plant communities, and the correlation between plant invasions and a subsequent decline in native species is well documented at some scales. However, one outstanding question is the degree to which invasive species are a driver of native plant declines versus a correlate of other drivers, such as habitat disturbance. These two hypotheses to explain the dominance of invasive species in communities have been termed the ‘driver’ and ‘passenger’ models, respectively. In order to understand the impacts of plant invasion on native plants we need more studies that consider the role of correlated environmental predictors, which may play unseen roles in the response and recovery of native plant communities frequently attributed to invasion alone. Using a large database of plant community and environmental data from sites across Southern Ontario, I used path analyses to examine the direct and indirect relationships between disturbance, exotic and native plant richness, and relative abundance. Counter to my initial predictions, I found support for both the partial passenger and partial driver models of invasive dominance, while full passenger models were outright rejected. The causal hypotheses consistent with the data indicated significant relationships between native and exotic species richness and native and exotic relative abundance across models. An exploratory analysis, which examined species-specific models, found that the data was consistent with seven out of twelve causal hypotheses. Models that could not be rejected were split almost evenly across full passenger, partial passenger, and partial driver models. Model support varied according to the species included in the dataset suggesting that the best fit underlying model of invasive dominance likely varies by species. While the partial passenger and partial driver models were recurrently consistent with the data, no single model described the underlying patterns of invasive dominance across all systems.

In the autumn of 1775, American revolutionaries invaded Canada in the hope of winning a fourteenth colony for the cause, dealing a fatal blow to the British war effort, and forcing London to reconcile on American terms. Led by Richard Montgomery and Benedict Arnold, the two-pronged effort met with nothing but victory on the way to Quebec. Set back by an unexpected repulse on December 31, however, the Northern Army was finally forced to retreat from the province altogether in the summer of 1776. Having failed either to secure an alliance with Canada or to achieve reconciliation with Britain, the campaign proved a total disaster, and has therefore been understudied or ignored completely by most historians. This dissertation argues that the invasion of Canada proved crucial in destroying the British empire in America and creating the social logic for independence. When the campaign failed to deliver on its primary objectives, American leaders in Philadelphia and colonists throughout the home front recognized that reconciliation was impossible. Historians frequently give credit to Thomas Paine’s Common Sense for igniting widespread calls for independence, but it was the failure of the Canadian campaign that lent urgency to these arguments, occasioning the swift transition from colonial rebellion to all-out civil war for American independence. The nature of the conflict had changed, creating a political-military context that made foreign assistance and a declaration of independence essential to sustaining the Revolution. This study also hopes to break down military history as a category too frequently walled off from other branches of historical inquiry. Early American historians tend to imagine the American Revolution and the War for Independence as two overlapping but distinct events. By analyzing the Canadian campaign’s effect upon the American home front, this dissertation seeks to use military events as a lens to reorient our understanding of the breakdown of empire and the path to independence. / 2022-08-31T00:00:00Z

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第18894号 / 医博第4005号 / 新制||医||1009(附属図書館) / 31845 / 京都大学大学院医学研究科医学専攻 / (主査)教授 山田 泰広, 教授 戸井 雅和, 教授 小川 誠司 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第20221号 / 医博第4180号 / 新制||医||1019(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 椛島 健治, 教授 中川 一路, 教授 生田 宏一 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第20606号 / 医博第4255号 / 新制||医||1023(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 羽賀 博典, 教授 篠原 隆司, 教授 近藤 玄 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第20665号 / 医博第4275号 / 新制||医||1024(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 羽賀 博典, 教授 横出 正之, 教授 瀬原 淳子 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM