Graduate Theses & Dissertations

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Mfsd8 regulates growth and multicellular development in Dictyostelium discoideum
The neuronal ceroid lipofuscinoses (NCLs), commonly known as Batten disease, are a family of inherited neurodegenerative lysosomal storage disorders. CLN7 disease is a subtype of NCL that is caused by mutations in the MFSD8 gene. MFSD8 encodes a lysosomal transmembrane protein that is predicted to play a role in transporting small substrates across membranes. However, little is known about its role and substrate specificity. Previous work identified an ortholog of human MFSD8 in the social amoeba Dictyostelium discoideum and reported its localization to endocytic compartments. In this study, the effects of mfsd8 loss during Dictyostelium growth and multicellular development were further characterized. Dictyostelium mfsd8- cells displayed increased rates of proliferation and pinocytosis in liquid media. During growth, loss of mfsd8 altered lysosomal enzymatic activities and reduced the intracellular and extracellular levels of autocrine proliferation repressor A. mfsd8- cells grown on a lawn of bacteria formed plaques in a shorter period of time compared to WT cells, providing additional support for the enhanced growth of mfsd8- cells. Upon starvation, the aggregation of mfsd8- cells was delayed, and mfsd8- cells formed more mounds that were smaller in size, which may be attributed to the reduced cell-substrate adhesion and altered lysosomal enzymatic activities observed for mfsd8- cells. Following aggregation, tipped mound formation was delayed, however, loss of mfsd8 did not affect the timing of slug/finger and fruiting body formation. Additionally, slug migration was reduced in mfsd8- cells. These aberrant phenotypes, excluding fruiting body formation, were effectively or partially rescued when Mfsd8-GFP was introduced into mfsd8- cells. Overall, these results show that Mfsd8 plays a role in regulating growth and developmental processes in Dictyostelium via lysosomal-associated functions. Author Keywords: CLN7, Dictyostelium discoideum, Lysosomes, MFSD8, Neuronal Ceroid Lipofuscinoses
Isotopes of the Caribbean
This research represents the first stable carbon and nitrogen isotope analysis of human bone collagen (n = 29) from the Escape Site (AD 300 - 1000), Saint Vincent. As a two-pronged investigation, this research had the following goals: (1) determining the ideal pretreatment for poorly preserved bones and (2) reconstructing the Escape Site sample population diet. By incorporating powdered specimens, shorter demineralizations and increased acid:sample exposure, higher collagen yields were produced, thereby expanding the sample size for isotopic analysis. Notably, the elemental data suggests that not all isolated collagen was biogenic and was perhaps contaminated by non-collagenous proteins. This highlighted the importance of using multiple criteria to rigorously evaluate collagen based on the full quality indicator profile. In the end, 5 individuals yielded useable isotope data which was consistent with a broad spectrum diet relying primarily on C3 plants as well as terrestrial, reef, nearshore and freshwater fauna. Within the broad region, the Escape Site data was comparable to other islands from the Lesser Antilles and Cuba emphasizing the influence of regional biodiversity as well as the likelihood that the studied population contributed and benefitted from the extensive Saladoid trade networks which existed at the time. Author Keywords: Caribbean, Collagen, Escape Site, Human diet, Saladoid, Stable isotope analysis
Modelling Request Access Patterns for Information on the World Wide Web
In this thesis, we present a framework to model user object-level request patterns in the World Wide Web.This framework consists of three sub-models: one for file access, one for Web pages, and one for storage sites. Web Pages are modelled to be made up of different types and sizes of objects, which are characterized by way of categories. We developed a discrete event simulation to investigate the performance of systems that utilize our model.Using this simulation, we established parameters that produce a wide range of conditions that serve as a basis for generating a variety of user request patterns. We demonstrated that with our framework, we can affect the mean response time (our performance metric of choice) by varying the composition of Web pages using our categories. To further test our framework, it was applied to a Web caching system, for which our results showed improved mean response time and server load. Author Keywords: discrete event simulation (DES), Internet, performance modelling, Web caching, World Wide Web
Clonal structure and mating patterns in a natural population of Sagittaria latifolia
Increased plant size is expected to have negative consequences for mating by increasing pollen transfer among the same plant. However, recent theoretical studies have demonstrated that this may not be true for clonal plants. Instead, clonal expansion could enhance outcrossing opportunities without increasing selfing by reducing distances to potential mates. I investigated how the spatial structure of clones influences patterns of pollen dispersal, selfing rates and siring success in a natural population of Sagittaria latifolia. I found that pollen dispersal distances typically exceeded the spatial extent of clones and there was a positive association between clone size and the likelihood that clones were intermingled. Together, this resulted in a weak positive association between clone size and selfing rates, and a strong positive association between clone size and outcross siring success. This is the first empirical support for the theoretical expectation that any negative effects of selfing in large clones might be offset by increased siring success. Author Keywords: clonal growth, fitness gain curve, geitonogamy, plant mating, plant reproductive ecology, sex allocation theory
Assessing habitat suitability and connectivity for an endangered salamander complex
Habitat loss and fragmentation have significantly contributed to amphibian population declines, globally. Evaluating the state of remaining habitat patches can prove to be beneficial in identifying areas to prioritize in conservation efforts. Pelee Island, Ontario is home to a complex of salamanders including small-mouthed salamanders (Ambystoma texanum), blue-spotted salamanders (A. laterale) and unisexual Ambystoma (small-mouthed salamander dependent population). These populations have declined from intense landscape changes since the late 1800s, particularly from the historical drainage of wetlands. In this thesis, I evaluated the suitability and connectivity of habitat patches occupied by these salamanders to assess the size of, and dispersal capabilities between, remaining habitat patches. I found that there was a low amount of suitable terrestrial habitat available for this complex of salamanders, and existing habitat patches were small and isolated. Forested areas and non-breeding wetlands were considered to be suitable habitat when adjacent to existing breeding locations, suggesting that these habitats should be a focus for conservation efforts. Notably, intervention may be necessary to maintain this amphibian complex as many assemblages are isolated from one another and potential corridors currently consist of primarily unsuitable habitat. Given that much of the salamander complex is reliant on one species for reproduction, the long-term viability of this population of Ambystoma salamanders may rely on the enhancement of suitable habitat near current breeding sites by conservation organizations and local stakeholders. Ultimately, the approach used in this thesis emphasizes the value of evaluating habitat within a fragmented landscape to focus conservation efforts on imperilled species. Author Keywords: amphibians, connectivity, habitat suitability, landscape fragmentation, landscape resistance, unisexual
Application of Data Science to Paramedic Data
Paramedic data has significant potential for research. Paramedics see many patients every year and collect a wide variety of crucial data at each encounter. This data is rarely used for good reason: it’s messy and hard to work with. But like theunderdog character in a classic movie, with a little bit of work and a lot of understanding, paramedic data has significant potential to change the world of medical research. Paramedics throughout the world are involved in research every day, but most of this research uses purpose-built data structures and never takes advantage of the existing data that paramedics create as part of their everyday work. Through a project-based approach grounded in developing a better understanding of the opioid crisis, this thesis will examine the quantity and structure of the existing paramedic data, the complexities of its current design, the steps necessary to access it, and the processes necessary to clean existing data to a point where it can be easily modelled. Once we have our dataset, we will explore the challenges of choosing key metrics by examining the effectiveness of metrics currently employed to monitor the opioid crisis and the influences public health programs and changing policies have had on these metrics. Next, we will explore the temporal distributions of opioid and other intoxicant use with an eye to providing data to support public health in their harm reduction efforts. And lastly, we will look at the effect of fixed- and floating-point temporal influences on intoxicant-related calls with an eye to how these temporal points can affect call volumes. By using this exploration of the opioid crisis, this thesis will show that with a more thorough understanding of what paramedic data is, what data points are available, and the processes needed to transform it, paramedic data has the potential to greatly expand the limits of health care data science into a more precise and more all-encompassing discipline. Author Keywords: Ambulance, Data Science, Opioid, Overdose, Paramedic, Pre-hospital
Differences and similarities in exploration and risk-taking behaviours of two Myotis bat species.
AbstractDifferences and similarities in exploration and risk-taking behaviours of two Myotis bat species. Laura Michele Scott Behaviours that are repeatable across circumstances and time determine an individual’s personality. Personality and behavioural variation are subject to selective pressures, including risks related to the use of different habitat types. I explored the ecological and evolutionary consequences of habitat selection by comparing the behaviour of two sympatric bat species, Myotis leibii and M. lucifugus. These species display overlap in roosting preferences, however, M. leibii tend to roost in crevices on the ground, while M. lucifugus tend to roost in crevices or cavities that are raised off the ground. I hypothesized that the habitat selection patterns of these two species create behavioural reaction norms at the species level. I predicted that ground roosting behaviour favours bolder personality and more exploratory and active traits when compared with bats that do not ground roost. I examined inter- and intra-specific variation in behaviour using a modified, three-dimensional open-field test and quantified the frequency and duration of behaviours such as flying, landing, and crawling. Bats were continuously video-recorded over 1-hour nocturnal and diurnal trials. I used a priori mixed models with combinations of individual characteristics and life-history traits to select the models that best describe each species. We found that M. leibii (n = 15) displayed more exploratory and bolder behaviours than M. lucifugus while on the ground (n = 21) and higher overall activity during the trial. I also found that M. leibii displayed crawling behaviours and movements consistent with foraging while on the ground which is a rare behaviour in bats and only observed in a few species (Desmodus rotundus and Mystacina tuberculate to my knowledge). Future research should explore biomechanical adaptations associated with ground-foraging in M. leibii. Author Keywords: Bats, Behaviour, Exploration, Myotis leibii, Myotis lucifugus, Roosting
Contributions of Mayflies (EPHEMEROPTERA
Walleye (Sander vitreus) are an ecologically and economically significant fish harvestedby recreational and commercial fisheries across Ontario. Adult Walleye are piscivores, but anecdotal evidence from anglers suggests that Walleye often target aquatic insects such as mayfly larvae (Ephemeroptera). My research examined the diet of Walleye caught from May to September in Lake St. Joseph in northern Ontario. I examined the stomach contents of angle harvested Walleye to identify the prey over two summers. Through morphological analysis of stomach contents, mayflies were found to be a significant prey source for Walleye, during larval emergence events in early summer, and to a lesser extent throughout the rest of the summer season. These findings are important for long term management of Walleye populations and associated resources. I also assess the potential and problems of Walleye management and research from my experiences of having worked with industry, government, and university partners on this project. Author Keywords: alternative prey, Food web interactions, invertebrate, piscivore, Predator prey interactions
Impacts of Cover Crops on Soil Health, Soil Nitrogen Dynamics, and Cytokinin Profiles
In Ontario, the dominant cash crop rotations consist of soybean (SB), which is a leguminous crop grown in rotation with maize (MZ) and winter wheat (WW). In addition to these crops, some farmers integrate cover crops (CC) into crop rotation, especially during the fallow period and winter seasons, to reduce nitrogen (N) losses via nitrate (NO3-) leaching and emission of N2 and the greenhouse gas nitrous oxide (N2O). This thesis focused on understanding the impact of crop phases in a MZ-(SB-WW)-CC rotation on the abundance of N-cycling bacterial communities that mediate nitrification and denitrification pathways. In addition, the influence of CCs on soil cytokinin (CK) profiles, which are plant growth-promoting hormones, were studied in a greenhouse trial to assess their potential impacts when integrating CCs into crop rotations. In particular, the relationship between traditional soil health parameters and the soil CK profiles was studied to understand how CKs might reflect biotic interactions and soil vitality. Results indicate N fertilizer application mono ammonium phosphate (MAP) and starter N:P: K (24:6:24) during WW planting in fall largely supported nitrifying bacterial communities (amoA) and potentially contributed to NO3- leaching. Management of MZ, which included spring-applied MAP resulted in larger denitrifying (nirK) bacterial communities, increasing the potential risk of N-loss via emission of dinitrogen gas (N2) and greenhouse gas N2O. However, CC soils had significantly lower nirK than MZ, reflecting the importance of strong and deep root systems of CCs, which have a higher ability to scavenge the substrates for denitrifying communities (NO3-). This highlights the importance of growing CCs in reducing the potential risk for N-loss via leaching and denitrification. Additionally, in the greenhouse trial, the ability of CCs to affect CK was detected, highlighting the importance of integrating CC in crop rotations. This is particularly noteworthy, given that total CK profiles showed strong associations with traditional soil health parameters such as labile or active carbon and soil microbial community diversity. It was concluded that total soil CK can be used as a novel and dynamic soil health measure. Future research on quantifying N2O fluxes and levels of NO3- in leachates would provide a more precise understanding of the impact of different crop rotation phases on N-dynamics in these fields. Further studies on single or combined measures of soil CKs are warranted to develop its potential as a practical and effective soil health parameter. Author Keywords: Cover crops, Crop rotations, Cytokinin hormone, Nitrogen Cycle, qPCR, Soil health
Deep learning for removal of non-resonant background in CARS hyperspectroscopy
In this work, a deep learning approach proposed by Valensise et al. [3] for extracting Raman resonant spectra from measured broadband CARS spectra was explored to see how effective it is at removing NRB from our experimentally measured “spectral-focusing”-based approach to CARS. A large dataset of realistic simulated CARS spectra was used to train a model capable of performing this spectral retrieval task. The non-resonant background shape used in creating the simulated CARS spectra was altered, to mimic our experimentally measured NRB response. Two models were trained: one using the original approach (Specnet) and one using the updated NRB “Specnet Plus”, and then tested their ability to retrieve the vibrationally resonant spectrum from simulated and measured CARS spectra. An error analysis was performed to compare the model's retrieval performance on two simulated CARS spectra. The modified model's mean squared error value was five and two times lower for the first and second simulated CARS spectra, respectively. Specnet Plus was found to be more effective at extracting the resonant signals. Finally, the NRB extraction abilities of both models are tested on two experimentally measured CARS hyperspectroscopy samples (starch and chitin), with the updated NRB model (Specnet Plus) outperforming the original Specnet model. These results suggest that tailoring the approach to reflect what we observe experimentally will improve our spectral analysis workflow and increase our imaging potential. Author Keywords:
Effect of Attending a Virtual Oncology Camp on Childhood Cancer Patient's Pyshcosocial Functioning and Parental Stress - A Pilot Study
Objectives/purpose: The current study examined whether attending a 1-month virtual oncology camp (VOC) improved resilience and hope in childhood cancer patients and parental/caregiver stress. Methods:Childhood cancer patients/survivors and their parent/caregivers enrolled for VOC, participated in an online anonymous survey: before, after and 3-months after VOC. The survey included the Child and Youth Resilience Measure (CYRM) and the Snyder’s Children’s Hope Scale (CHS) for the childhood cancer patients/survivors and the Pediatric Inventory for Parents (PIP) for parent/caregivers. Results:CYRM scores increased from T1 to T2 (d=0.86). Compared to T1, at T2 CHS scores also increased (d=1.33). Both CHS and CYRM scores remained higher at T3 compared with T1 (d=1.34; d=0.86). There were no changes in PIP scores between any time points. Conclusion and significance: Our study demonstrated that participation in a VOC improved children’s resilience and hope but did not change parental stress. Highlighting the clinical significance of these VOCs and the impacts they have on childhood cancer patients/survivors. Author Keywords: cancer, children, hope, parental stress, resilience, virtual oncology camp
Organic Matter and Total Mercury in Acid-Sensitive Lakes in Ireland
The following study measured dissolved organic carbon (DOC) and total mercury (THg) concentrations in acid sensitive lakes in the Republic of Ireland. Sixty-eight upland lakes and 48 lowland lakes were sampled for DOC; the upland lakes were additionally sampled for THg. Spatial variability of DOC was explained by regional precipitation and soil organic matter. A subset of lakes was tested for long-term trends and in contrast to reports of rising DOC in European surface waters, changes in DOC were minor. Spatial variability in THg was explained by DOC and organic matter aromaticity. Long-term THg concentrations increased, likely caused by inputs of terrestrial THg. A subset of lakes was sampled for sediment and soil and the results suggested soils drove THg variation in lake water and sediment. Lake water and sediment THg was low and consistent with background regions, while soil THg was relatively high due to high organic content. Author Keywords: Dissolved Organic Carbon, Lakes, Organic Matter, Soil, Total Mercury, Water

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Format: 2024/03/28