Medicine and Health Sciences Commons^™

The Mitochondrial Calcium Uniporter Regulator 1 (Mcur1) Matrix Domain Is A Self-Associated Multimer Sensitive To Divalent Cations, Naveed Siddiqui

Electronic Thesis and Dissertation Repository

Mitochondria are primarily appreciated for the generation of adenosine triphosphate (ATP), a chemical store of energy required by all cells. These organelles, however, also play key roles in apoptosis, autophagy and shaping cytosolic calcium (Ca²⁺) signaling via Ca²⁺ uptake into the mitochondrial matrix. This Ca²⁺ uptake is mediated chiefly via the mitochondrial Ca²⁺ uniporter (MCU), an inner mitochondrial membrane protein that oligomerizes to form a Ca²⁺ selective pore. MCU is regulated by several protein binding partners, including the recently identified MCU regulator-1 (MCUR1). MCUR1 stabilizes a higher order MCU heterocomplex through interactions with MCU …

Investigating The Role Of Endogenous Atf4 Upregulation On Neuronal Glutathione Level, Fatemeh Mirshafiei

Electronic Thesis and Dissertation Repository

ATF4 is a transcription factor that is activated in response to integrated stress response (ISR). In neurons specifically, ATF4 has been suggested to act as a pro-apoptotic transcription factor. The expression of ATF4, as well as its downstream gene targets have been implicated in both in vivo and in vitro models of Alzheimer’s and Parkinson’s Disease. However, the mechanism by which ATF4 promotes cell death remains unclear. It was previously shown that overexpression of ATF4 in primary cortical neurons caused a reduction in glutathione levels, resulting in oxidative stress-induced cell death. The aim of this project was to investigate whether …

Applications Of Ct Perfusion-Based Triaging And Prognostication In Acute Ischemic Stroke, Eric A. Wright

Electronic Thesis and Dissertation Repository

CT Perfusion (CTP) is a minimally invasive imaging technique that aids acute ischemic stroke (AIS) triage and prognostication by determining tissue viability based on hemodynamic parameters. The goals of this research are to determine: 1) CTP thresholds for estimation of infarct and penumbra volume, 2) how CTP scan duration impacts infarct and penumbra volume estimates, and 3) reliability of CTP for predicting functional outcomes following intra-arterial therapy (IAT).

Chapter 2 introduced an experimental study for determining ischemia-time dependent thresholds for brain infarction using multimodal imaging in a porcine stroke model that is easier to implement than previous large animal stroke …

Medial Geniculate Projections To Auditory And Visual Cortex In Hearing And Deaf Cats, Benjamin Trachtenberg

Electronic Thesis and Dissertation Repository

Following early-onset deafness, studies have demonstrated crossmodal plasticity, throughout “deaf” auditory cortex. Crossmodally reorganized auditory cortex shows increased dendritic spine density, which suggests increased numbers of axon terminals. I examined projections from the medial geniculate body (MGB) of hearing and early-deaf cats in order to reveal the distribution of synaptic boutons in the cortex, originating from MGB neurons. Anterograde fluorescent dextran tracers were deposited bilaterally in the MGB in order to label cortical axon terminals. Deafness resulted in axon terminal increases in visual cortex, and conservation of auditory axon terminal distribution. Visual areas PLLS and area 18 received increased projections …

Multi-Scale Peripheral Vasculopathy With Metabolic Syndrome, Kent Lemaster

Electronic Thesis and Dissertation Repository

The combination of cardiovascular and metabolic risk factors including obesity, dyslipidemia, hypertension, and insulin resistance, in combination with a prothrombotic and proinflammatory state, is a condition termed Metabolic Syndrome (METS). Twenty percent of the adult population is afflicted with METS which increases the risk of type-2 diabetes mellitus and cardiovascular disease. Further, the presence of peripheral vascular disease (PVD) is tightly coupled with METS which is a perfusion-demand mismatch of blood supply to active skeletal muscle resulting in painful claudication and a late-stage potential for amputation. The underlying contributors of METS associated micro-vasculopathies in the skeletal muscle, their impact on …

White Matter Inflammation And Executive Dysfunction: Implications For Alzheimer Disease And Vascular Cognitive Impairment, Alexander Levit

Electronic Thesis and Dissertation Repository

White matter integrity is crucial to healthy executive function, the cognitive domain that enables functional independence. However, in the ageing brain, white matter is highly vulnerable. White matter inflammation increases with age and Alzheimer disease (AD), which disrupts the normal function of white matter. This may contribute to executive dysfunction, but the relationship between white matter inflammation and executive function has not been directly evaluated in ageing nor AD. White matter is also particularly vulnerable to cerebrovascular disease, corresponding with the common presentation of executive dysfunction in vascular cognitive impairment (VCI). Thus, white matter may be an important substrate by …

Quantitative Analysis Of Three-Dimensional Cone-Beam Computed Tomography Using Image Quality Phantoms, Rudy Baronette

Electronic Thesis and Dissertation Repository

In the clinical setting, weight-bearing static 2D radiographic imaging and supine 3D radiographic imaging modalities are used to evaluate radiographic changes such as, joint space narrowing, subchondral sclerosis, and osteophyte formation. These respective imaging modalities cannot distinguish between tissues with similar densities (2D imaging), and do not accurately represent functional joint loading (supine 3D imaging). Recent advances in cone-beam CT (CBCT) have allowed for scanner designs that can obtain weight-bearing 3D volumetric scans. The purpose of this thesis was to analyze, design, and implement advanced imaging techniques to quantify image quality parameters of reconstructed image volumes generated by a commercially-available …

Wearable Sensors And Total Knee Arthroplasty: Assessing Quantitative Function To Improve The Patient Experience, Megan Fennema

Electronic Thesis and Dissertation Repository

Osteoarthritis (OA) is a chronic degenerative disease for which the only long-term solution is total knee arthroplasty (TKA), though many patients are not satisfied with their TKA. Satisfaction in TKA patients is not well understood. Subjective questionnaires and objective functional tests have been previously used to assess TKA outcomes, but both have disadvantages. Wearable sensors have facilitated affordable biomechanical measurement in OA and TKA populations. The objective of this work was to use wearable sensors alongside functional tests with TKA patients to identify quantitative function that related to subjective function and satisfaction. A wearable sensor-setup was validated before implementation in …

Validation Of A Hyperspectral Nirs Method For Measuring Tissue Oxygen Saturation, Matthew Kewin

Electronic Thesis and Dissertation Repository

Brain injury during preterm infancy can cause serious intellectual and behavioral disabilities, as such, measurements of cerebral health are needed to aid in the diagnosis and treatment of these injuries. Near infrared spectroscopy (NIRS) is considered ideal for this purpose because it is non-invasive and provides a continuous measure of tissue oxygen saturation (StO₂), a key marker of cerebral health. Current commercial NIRS systems have considerable variability between devices and between infants restricting them to monitoring trends. Time-resolved (TR) NIRS is considered the gold standard in biomedical optics for quantifying tissue optical properties, but the technology is more …

Effects Of Maternal Protein Restriction On The Pulmonary Surfactant System During The Early Life And Adulthood, Reza Khazaee

Electronic Thesis and Dissertation Repository

Fetal growth restriction (FGR) is defined by low birth weight and contributes to a variety of adult-onset diseases with different severities between males and females. However, the effects of FGR on the pulmonary surfactant are not fully elucidated. In this thesis, first, we investigated the FGR effects on the lung function and the surfactant system at the early postnatal life. It was hypothesized that FGR contributes to alterations of lung mechanics and the surfactant system during the neonatal period. Second, we assessed the FGR effects on the surfactant system in response to sepsis in adulthood. It was hypothesized that FGR …

Limbic System Involvement In Absence Seizures, Rukham Ajaz

Electronic Thesis and Dissertation Repository

Absence epilepsy is characterized by brief spells of absent stare and spike wave discharges (SWDs), generally believed to be generated by a thalamocortical network. Our lab showed that hippocampal neuronal firings were synchronous with SWDs in a gamma butyrolactone (GBL) model of absence epilepsy in rats (Arcaro et al., 2016). We hypothesize that, in a GBL model of absence seizures, 30-400 Hz oscillations in the spontaneous local field potentials (LFPs) in the hippocampus and other parts of limbic system (amygdala and nucleus accumbens) are phase modulated by SWDs, and this modulation is mediated through nucleus reuniens of midline thalamus (RE). …

An Integrated Approach To Analyzing Arteriolar Network Hemodynamics., Zahra Farid

Electronic Thesis and Dissertation Repository

The objective of this thesis was to optimize our technique for studying blood flow in arteriolar networks by including capillary resistance and venular network geometry. We aimed to validate our technique using experimental flow measurements and Murray’s law. First, arteriolar and venular networks were reconstructed from intravital videomicroscopy (IVVM) images of the gluteus maximus muscle, and capillary resistance was estimated and distributed to each terminal arteriole (TA) segment according to its diameter. Resistance for small arterioles and venules that were likely missed in our IVVM experiments were also added to each TA segment in our reconstructed networks based on measured …

Development And Validation Of A Stand-Alone Dcs System For Monitoring Absolute Cerebral Blood Flow., Mahro Khalid

Electronic Thesis and Dissertation Repository

Premature infants are at high risk of neonatal brain injury due to poor cerebrovascular regulation, leading to periods of dangerously low cerebral blood flow (CBF) and possible injury. However, there are currently no established bedside methods of monitoring CBF to alert the intensive care staff to cerebrovascular dysfunction. Diffuse correlation spectroscopy (DCS) is an emerging noninvasive optical technique for monitoring relative CBF. I developed a stand-alone DCS method of monitoring absolute CBF by incorporating a quantitative dynamic contrast-enhanced (DCE) technique. This required modifying a DCS system to capture multi-distance data to measure the tissue optical properties and to perform DCE …

Diffusion And Functional Mri Of The Brain Following Sports-Related Impacts And Concussion, Kathryn Y. Manning

Electronic Thesis and Dissertation Repository

Concussion is a prevalent injury associated with contact sports, however the underlying brain changes associated with concussion remain poorly understood. Therefore it is critical to (a) understand the complex sequelae that underlie concussion, (b) when or if the brain recovers, and (c) if there are brain changes associated with contact sports in general. Advanced imaging techniques may be sensitive to changes that persist beyond relatively prompt symptom recovery and clearance to return to play.

Resting state functional MRI (RS-fMRI) and diffusion tensor imaging (DTI) data was acquired on the 3T at Robarts Research Institute from healthy and concussed athletes from …

Understanding The Impact Of Hiv-1 Genetic Diversity On The Function Of Nef And Its Role In Serinc5 Antagonism, Aaron Leslie Johnson

Electronic Thesis and Dissertation Repository

HIV-1 Nef is a key pathogenic protein, allowing HIV-1 to evade the host immune system by downregulating MHC-I and CD4. Furthermore, it was recently discovered that Nef counteracts the host factor SERINC5 to increase HIV-1 infectivity, but the mechanistic details of the Nef:SERINC5 interaction still need to be explored. Throughout this dissertation, I will explore the hypothesis that the genetic diversity that defines HIV-1 has a pronounced effect on the HIV-1 protein Nef, altering its function between and within group M subtypes. To address this hypothesis I investigated how MHC-I and CD4 downregulation differ among all non-recombinant group M subtypes. …

The Epidemiology Of Infective Endocarditis Among People Who Inject Drugs In London, Ontario., Brian Hallam

Electronic Thesis and Dissertation Repository

Infective endocarditis is an infectious disease that affects the valves of the heart. Injection drug use is currently a leading risk factor among patients with endocarditis. We conducted a prospective study using data from hospital chart records among patients with endocarditis in London, Ontario, which has a relatively high prevalence of people who inject drugs to assess the severity of the issue and the major risk factors of mortality pertaining to this population. This study had a sample size of 353 and included a review of the incidence of admissions of endocarditis, as well as a survival analysis, using both …

Localization And Trafficking Of Pannexin 1 In Polarized And Non-Polarized Cells, Michelle Shum

Electronic Thesis and Dissertation Repository

The channel-forming membrane protein pannexin 1 (Panx1) is best characterized as an ATP release channel and has been linked to over a dozen human pathologies. Along with protein- protein interactions and post-translational modifications, the physiological function of Panx1 channels is highly dictated by its subcellular localization. In polarized epithelial cells in vivo, Panx1 is reported to selectively localize to distinct plasma membrane domains. Here, we investigated whether this polarized distribution is guided by internal motifs contained within the Panx1 polypeptide. In polarized MDCK cells, Panx1 was localized predominantly at the apical membrane domain, although a subset remained detectable in the …

Inhibition Of Nk Cell-Mediated Cytotoxicity By Tubular Epithelial Cell Expression Of Clr Proteins, Benjamin B. Fuhrmann

Electronic Thesis and Dissertation Repository

Cytotoxic effector cells can target and kill parenchymal cells of the kidney which results in injury and loss of function. Endogenous regulatory systems may exist to attenuate Natural Killer (NK) and other effector cell activation and cytotoxicity in diverse conditions, including ischemia-reperfusion injury associated with kidney transplantation. Understanding these mechanisms will direct new therapeutic strategies. Kidney tubular epithelial cells (TEC), the predominant cell type in kidneys, may negatively regulate NK cell activation by surface expression of C-type lectin-related proteins (Clr). Clr-b and -f were found to be expressed by wild type (WT) TEC. Clr-b was upregulated by …

Drug Response And Metabolism In Crohn's Disease, Aze Wilson

Electronic Thesis and Dissertation Repository

Inflammatory bowel disease (IBD) is an illness of chronic intestinal inflammation comprised of Crohn's disease (CD) and ulcerative colitis (UC). Specialists rely heavily on drugs that target a dysregulated immune system. There is a staggering degree of variation in drug response in CD. Our understanding of drug metabolism and response in IBD is limited. Gaining new insights into IBD-specific modifications of drug metabolism may allow for improved drug efficacy and reduced toxicity. Cytochrome P450 (CYP) 3A4 is the most relevant determinant of drug metabolism and exposure for medications prescribed today. CYP3A4 is highly expressed in the liver, but is also …

Genetic Determinants Underlying Rare Diseases Identified Using Next-Generation Sequencing Technologies, Rosettia Ho

Electronic Thesis and Dissertation Repository

Rare disorders affect less than one in 2000 individuals, placing a huge burden on individuals, families and the health care system. Gene discovery is the starting point in understanding the molecular mechanisms underlying these diseases. The advent of next-generation sequencing has accelerated discovery of disease-causing genetic variants and is showing numerous benefits for research and medicine. I describe the application of next-generation sequencing, namely LipidSeq™ ‒ a targeted resequencing panel for the identification of dyslipidemia-associated variants ‒ and whole-exome sequencing, to identify genetic determinants of several rare diseases. Utilization of next-generation sequencing plus associated bioinformatics led to the discovery of …

Toward Optimization Of Target Planning For Magnetic Resonance Image-Targeted, 3d Transrectal Ultrasound-Guided Fusion Prostate Biopsy, Peter Martin

Electronic Thesis and Dissertation Repository

The current clinical standard for diagnosis of prostate cancer (PCa) is 2D transrectal ultrasound (TRUS)-guided biopsy. However, this procedure has a false negative rate of 21-47% and therefore many patients return for repeat biopsies. A potential solution for improving upon this problem is “fusion” biopsy, where magnetic resonance imaging (MRI) is used for PCa detection and localization prior to biopsy. In this procedure, tumours are delineated on pre-procedural MRI and registered to the 3D TRUS needle guidance modality. However, fusion biopsy continues to yield false negative results and there remains a gap in knowledge regarding biopsy needle target selection. Within-tumour …

Clinical And Genetic Predictors Of Aromatase Inhibitor-Induced Arthralgia, Adrienne Elizabeth Borrie

Electronic Thesis and Dissertation Repository

Aromatase inhibitors (AIs) are the most commonly used first-line endocrine treatment for postmenopausal women with estrogen receptor-positive breast cancer. Significant adverse drug reactions are associated with AIs, the most common being arthralgia. We hypothesized that a comprehensive assessment of pharmacogenetic and clinical variables that affect AI tolerability could improve AI selection and treatment for breast cancer patients. We recruited 196 patients diagnosed with breast cancer initiating AI therapy at the London Regional Cancer Program. Patients completed questionnaires regarding arthralgia symptoms and provided blood samples at baseline, 2 months and 6 months after AI initiation. Plasma letrozole drug concentration was measured …

Clinical And Pharmacogenetic Determinants Of Plasma Factor Xa Inhibitor Systemic Exposure, Markus Gulilat

Electronic Thesis and Dissertation Repository

Inhibition of blood coagulation via oral anticoagulant therapy is the mainstay for preventing a cardioembolic stroke in patients with atrial fibrillation (AF). Factor Xa inhibitors (FXaIs), rivaroxaban and apixaban, represent a new class of oral anticoagulants that are now widely prescribed in AF patients as an alternative to traditional warfarin therapy. An important advantage of these drugs is that routine monitoring of anticoagulation response is not necessary. Nevertheless, because of their mechanism of action, FXaI antithrombotic effect can be inferred based on the observed drug plasma concentration, with prolonged periods of elevated FXaI systemic exposure associated with increased risk for …

Modulation Of Parathyroid Hormone 1 Receptor Signaling By Extracellular Nucleotides, Brandon Kim

Electronic Thesis and Dissertation Repository

Parathyroid hormone (PTH) activates the PTH/PTH-related peptide receptor (PTH1R) on osteoblasts and other target cells. Mechanical stimulation of cells, including osteoblasts, causes release of nucleotides such as ATP into the extracellular fluid. In addition to its role as an energy source, ATP serves as an agonist at P2 receptors and an allosteric regulator of many proteins. We investigated the effects of concentrations of extracellular ATP, comparable to those that activate low affinity P2X7 receptors, on PTH1R signaling. Cyclic AMP levels were monitored in real-time using a bioluminescence reporter and β-arrestin recruitment to PTH1R was followed using a complementation-based luminescence assay. …

Optimization Of Decision Making In Personalized Radiation Therapy Using Deformable Image Registration, Jason Vickress

Electronic Thesis and Dissertation Repository

Cancer has become one of the dominant diseases worldwide, especially in western countries, and radiation therapy is one of the primary treatment options for 50% of all patients diagnosed. Radiation therapy involves the radiation delivery and planning based on radiobiological models derived primarily from clinical trials. Since 2015 improvements in information technologies and data storage allowed new models to be created using the large volumes of treatment data already available and correlate the actually delivered treatment with outcomes. The goals of this thesis are to 1) construct models of patient outcomes after receiving radiation therapy using available treatment and patient …

Investigating The Cortical, Metabolic And Behavioral Effects Of Transcranial Direct Current Stimulation In Preparation For Combined Rehabilitation, Kayla N. Ryan

Electronic Thesis and Dissertation Repository

The goal of this thesis was to determine the cortical reorganization that occurs in patients with cervical spondylotic myelopathy (CSM) after surgical decompression and to implement this knowledge into a new rehabilitation strategy. Transcranial direct current stimulation (tDCS) is a non-invasive technique to modulate human behavior. Due to the novel electrode montage used, it was first pertinent that we determine how tDCS would modulate cortical, metabolic and motor behavior in healthy individuals.

We observed the longitudinal functional adaptations that occur in patients with CSM using functional MRI. Enhanced excitation of supplementary motor area (SMA) was observed following surgical decompression and …

Identification And Characterization Of Hiv-1 Antagonists To The Antiviral Protein, Herc5, Divjyot S. Kochar

Electronic Thesis and Dissertation Repository

Interferons that trigger the release of innate antiviral proteins are a vital immune defense mechanism against viruses such as HIV-1. HERC5, an interferon stimulated protein inhibits HIV-1 replication through two independent mechanisms: inhibiting export of HIV-1 RNA through the Rev-dependent pathway and blocking an early step in the assembly of the virion. HERC5 is an antiviral protein yet individuals infected with HIV fail to control the infection. This can be due to viral antagonist mechanisms which counteract the function of restriction factors. Using a viral particle release assay, I discovered HIV-1 Env and Vpu can function as potential antagonists to …

Methods For The Investigation Of Microvascular Control Of Oxygen Distribution, Richard Sove

Electronic Thesis and Dissertation Repository

The purpose of this thesis was to develop tools for studying oxygen-dependent regulation of red blood cell (RBC) flow distribution in the microcirculation. At the microvascular level, arterioles dictate the distribution of oxygen (O₂) carrying RBCs to downstream capillaries, a process which needs to be tightly regulated and coupled to O₂ off loading from capillaries to the tissue. To investigate potential regulatory mechanisms, an O₂ exchange platform was developed to manipulate the RBC hemoglobin O₂ saturation (SO₂) at the muscle surface while limiting the changes in SO₂ to only a single capillary …

A Normalization Circuit Of Attention In Primate Lateral Prefrontal Cortex, Lyndon Duong

Electronic Thesis and Dissertation Repository

The way in which visual neurons encode information pertaining to a cluttered scene with multiple stimuli, and subsequently filter behaviorally relevant information using attention remains poorly understood. Neurons of area 8a in the macaque lateral prefrontal cortex have been shown to encode visual and attentional signals. We trained two macaque monkeys in a visuospatial attention task and performed neurophysiological recordings to test how neurons in this area encode multiply presented stimuli and attentionally filter target stimuli from distractors. We found area 8a neuronal responses to several concurrently presented stimuli to resemble the average of individual responses to those stimuli when …

Functional Anatomy Of Palmar Musculature, Colin W. Moore

Electronic Thesis and Dissertation Repository

The palmaris longus (PL) and palmaris brevis (PB) are upper limb muscles considered atavistic remnants of those found in animal species. Despite their use in surgical grafting and tendon transfer procedures, the functional role of the PL and PB have not been investigated comprehensively in vivo. Using a multi-modal experimental approach consisting of indwelling fine wire electromyography (EMG), ultrasonography and immunohistochemical muscle staining techniques, the function of the PL and PB in the hand was evaluated both in in vivo and in situ.

The purpose of Study 1 was to determine whether the PL provides synergistic contributions to …