Medicine and Health Sciences Commons^™

Discovery Of Novel Mechanisms Regulating Cancer Extravasation In The Chorioallantoic Membrane Model, Yohan Kim

Electronic Thesis and Dissertation Repository

Cancer metastasis is a multistep process that begins with the invasion of tumour cells into the stroma and migration towards the blood vessels. Tumour cells that have entered the bloodstream must then survive and leave by a process known as extravasation. Finally, extravasated cells proliferate and establish the secondary site in the metastatic cascade. Although extravasation encompasses key events during cancer cell invasion to aid in the development of effective treatments, an in vivo model that rapidly, reproducibly and economically recapitulates cancer cell extravasation is needed. Therefore, the objectives of my research were to 1) establish and validate an in …

Effect Of N-Acetyl-L-Cysteine Prevention Or Intervention On Diet Induced Beta Cell Compensation And Dysfunction, Madison Wallace

Electronic Thesis and Dissertation Repository

Type 2 diabetes mellitus (T2DM) progression increases oxidative stress which contributes to beta cell compensation and eventual dysfunction. To investigate the role of antioxidant N-acetyl-L-cysteine (NAC) on beta cell function and pancreatic stellate cell activation (aSMA⁺) during early and late stages of compensation, NAC was used for preventative (p) and intervention (i) treatments in C57BL/6N mice fed a 60% kcal high-fat diet (HFD) for 8 or 22 weeks. Significantly improved glucose tolerance was observed at 22 weeks following pNAC treatment in HFD mice. Although 22-week HFD mice displayed hyperinsulinemia, beta cell hypertrophy, decreased beta cell PDX-1 nuclear localization, …

Virally Packaged Rna In Virus-Like Particle Vaccines Enhances Antigenicity And Augments Latency Reversal Of Hiv-1, Chanuka Wijewardhana

Electronic Thesis and Dissertation Repository

Introduction:

Since Human Immunodeficiency Virus (HIV)-1 was determined to be the etiological agent behind acquired immunodeficiency syndrome (AIDS) in 1983, numerous attempts at a cure have been made; however, none have been effective. One of the primary roadblocks in achieving a cure is a transcriptionally-silent latent reservoir of memory CD4+ T cells harboring HIV provirus. Combined antiretroviral therapy (cART) inhibits actively replicating virus by interfering with various stages of the replication cycle. Therefore, non-replicative viruses–like the proviruses found in latently infected cells–are hidden from the actions of continued antiretroviral therapy. As a result, cART discontinuation or treatment holidays can result …

High Frequency Oscillations Are Phase-Amplitude Coupled In Stress Induced Seizures Following Traumatic Brain Injury, Paul Jung

Electronic Thesis and Dissertation Repository

Traumatic Brain Injury (TBI) often leads to the development of epilepsy, especially with the occurrence of stressful events. Stressors increase the levels of corticotropin-releasing factor (CRF) in the amygdala, which can be damaged by the secondary effects of TBI. It is hypothesized that the activity of CRF receptor type 1 (CRFR₁) in the amygdala is altered post-TBI and supports the generation of epileptiform waves, namely high-frequency oscillations (HFOs). Sprague-Dawley rats were given a moderate TBI and in vivo recordings of the amygdala were taken during the administration of an acute tail pinch stressor. The stressor increased broadband activity …

Characterization Of Wilms' Tumour 1 (Wt1) As A Biomarker For Fibrosis In Duchenne Muscular Dystrophy, Patrick Murphy

Electronic Thesis and Dissertation Repository

Duchenne muscular dystrophy (DMD) is the most common inherited pediatric muscle dystrophy. It is characterized by muscle degeneration, resulting in fibrosis that is a significant impediment to both endogenous muscle repair and any potential regenerative strategy. At present, there are few therapies that specifically address fibrosis and microenvironment improvement, but one possibility rests in targeting the Wilms’ tumour 1 (Wt1) protein. Wt1 is a zinc finger transcription factor, recently shown to be expressed in fibrotic conditions such as Dupuytren’s disease and pulmonary fibrosis. This thesis examines the expression pattern of Wt1 in several mouse models of DMD, through both histological …

Piezo1: Proteins For Mechanotransduction And Integration Of Endothelial Shear Stress & Intravascular Pressure, Juan Garcia Robledo M.D.

Electronic Thesis and Dissertation Repository

Piezo proteins are transmembrane ion channels, specialized in detecting mechanosensitive stimuli and transduce mechanical forces into biochemical signals. Piezo proteins research has helped understand physiological mechanisms, but the integrative role that Piezo1 plays in the regulation of the microvasculature has remained unstudied. Our main objective was to characterize ex vivo microvascular responses to the blockade of Piezo1 mechanotransduction in male (n=29) and female (n=24) Sprague-Dawley (SD) rats. Gracilis arterioles (GA) and middle cerebral arterioles (MCA) were harvested for ex-vivo vessel preparations. After vessel viability confirmation, every vessel was submitted to myogenic and flow challenges under control conditions and after Grammostola …

Comorbid Metabolic Syndrome And Prodromal Alzheimer's Disease In A Rat Model, Nadezda Ivanova

Electronic Thesis and Dissertation Repository

Metabolic syndrome (MetS), the development of which is associated with high-caloric Western diet intake, represents a risk factor for mild cognitive impairment (MCI) and Alzheimer’s disease (AD) and appears to contribute to AD progression when MetS and AD are comorbid. The interaction between AD and MetS might be through white matter inflammation, since white matter abnormalities and inflammation are important early events in the etiopathogenesis of both diseases. In these investigations, the effect of a high-caloric diet (HCD), to induce metabolic disturbances, on white matter neuroinflammation and cognitive function was investigated in a transgenic (TG) rat model of prodromal AD …

Mri Investigations Of Metabolic And Structural Brain Changes In Alzheimer’S Disease And Vitamin D Deprivation, Dickson Wong

Electronic Thesis and Dissertation Repository

Alzheimer's disease (AD) is a neurodegenerative disorder of the brain that presents as progressive impairment across several cognitive domains. The biological mechanisms underlying the development of AD remain unclear, with amyloid-beta plaques, neurofibrillary tangles, calcium dysregulation, and oxidative stress all contributing to neurodegeneration in AD. Vitamin D (VitD) deficiency, a common condition in the elderly, may modulate these mechanisms and complicate the AD process. Due to this complicated pathogenesis, the diagnosis of AD requires subjective clinical judgement, staging of AD is challenging, and it remains difficult to predict when and who will progress to AD. The purpose of this thesis …

Development Of A Computational Method For Assessing Static Field Induced Torque On Medical Implants, Xiao Fan Ding

Electronic Thesis and Dissertation Repository

The objective of this thesis is the development of a computational method for finding the torque induced on an object when placed in the static magnetic field of an MR scanner. As a preliminary step, the classic EM problems of a sphere and infinitely long cylinder of linear material was modeled in commercially available simulation software. Upon verification of the parameters implemented, the second step is the simulation of simple objects with realistic material properties, stainless-steel cylinders. Physical cylinders were machined to match those in the simulations and underwent the ASTM standard method for measuring induced torque. An adjacent study …

The Role Of Atf4 In Amyloid-Beta-Induced Neuronal Death., Gillian Petroff

Electronic Thesis and Dissertation Repository

Alzheimer’s disease (AD) is partially characterized by excessive accumulation of amyloid-b (Ab) in the brain. Ab oligomers have greater toxicity than Ab fibrils and induce neuronal stress. The Integrated Stress Response (ISR) is activated in response to cellular stress and increases expression of activating transcription factor 4 (ATF4) and its target genes. Prolonged activation has been shown to induce aberrant cell death, and increased markers of the ISR have been found in the brains of AD patients. However, the exact mechanism of amyloid-b-induced death is largely unknown. We aimed to determine if Ab-induced neuronal death occurs through ATF4-mediated upregulation of …

Dynamic Mechanostimulation Of Live Cells During Real-Time Microscopy, Daniel Lorusso

Electronic Thesis and Dissertation Repository

Our body’s functioning depends on the ability of cells to sense and react to their local mechanical environment; this process is known as mechanotransduction. Despite the importance of understanding how cells interact with mechanical stimuli, the specific mechanisms governing such processes have yet to be elucidated. Using microscopy to detect the early responses of living cells to mechanical loads and forces would be a critical step towards further understanding cellular mechanotransduction. Dynamic and high-frequency cyclical loads are relevant to human physiology and disease. Yet, modern microscopy systems are not capable of delivering the appropriate mechanical stimuli to live cell cultures. …

Effects Of A Unilateral Injection Of Botulinum Neurotoxin Subtype-A In The Subthalamic Nucleus Of A Parkinsonian Rat Model, Olga Khazov

Electronic Thesis and Dissertation Repository

Dopaminergic degeneration in Parkinson’s disease (PD) leads to altered functional activity within the basal ganglia (BG) circuitry, including hyperactivity of the subthalamic nucleus (STN). Treatments restoring the BG functional circuitry often result in improvements in parkinsonian symptoms in patients and animal models. A recent study from our laboratory identified that infusing botulinum toxin (BoNT-A) into the internal globus pallidus provided a transient restoration of motor asymmetry and goal-directed locomotion in a rat model of PD. We hypothesized that infusions of BoNT-A into the STN in a parkinsonian rat model will improve motor asymmetry and locomotor abnormalities. Infusions of BoNT-A into …

Assessing The Structure-Function Relationships Of The Apolipoprotein(A) Kringle Iv Sub-Type 10 Domain, Matthew J. Borrelli

Electronic Thesis and Dissertation Repository

Elevated plasma lipoprotein(a) (Lp(a)) is the most prevalent heritable risk factor in the development of cardiovascular disease. The apolipoprotein(a) (apo(a)) component of Lp(a) is strongly implicated in the pathogenicity of Lp(a). It is hypothesized that the inflammatory potential of Lp(a)/apo(a) is mediated by the lysine binding ability of the apo(a) kringle IV10 (KIV10) domain, along with its covalently bound oxidized phospholipid (oxPL). Using targeted mutagenesis, two novel null alleles for the LPA gene that generate non-secretable apo(a) species have been identified, resulting from amino acid substitutions in the KIV10 domain. A potential mechanism by which KIV10 oxPL modification is enriched …

The Role Of Pannexin 1 During Human Adipogenesis In Vitro, Jamie Emily Ching

Electronic Thesis and Dissertation Repository

Obesity is the unhealthy accumulation of adipose tissue and affects 10% of the global population. A study reported the loss of mouse pannexin 1 (Panx1), a large channel forming protein, increased adipogenesis in murine adipose derived stem cells (ASCs). Our study was designed to determine if human pannexin 1 (PANX1) inhibits adipogenesis in vitro using human ASCs and induced-mesenchymal stem cells (iMSCs) derived from induced pluripotent stem cells (iPSCs). Pharmacological inhibition of PANX1 using carbenoxolone halted adipogenesis in both the ASCs and iMSCs. When PANX1 was inhibited by probenecid, adipogenesis was impeded in iMSCs, but not in ASCs. PANX1-ablated iPSCs …

Functional Magnetic Resonance Spectroscopy In First-Episode Schizophrenia: Measuring Glutamate And Glutathione Dynamics At 7-Tesla, Peter Jeon

Electronic Thesis and Dissertation Repository

Schizophrenia is a neuropsychiatric illness without known etiology or cure. Current efforts for symptom treatment still seem to leave a large portion of affected individuals without proper symptom management, with those experiencing symptom relief still having to wrestle with potential side-effects from medication trials. There has been growing evidence suggesting that glutamate and glutathione abnormalities hold major roles in development and manifestation of schizophrenia symptoms.

Magnetic resonance spectroscopy (MRS) provides a non-invasive means to observe in-vivo brain chemistry, including glutamate and glutathione. By adding a functional component to an MRS paradigm (fMRS), such as the color-word Stroop task, it is …

Connectomic Analysis Of Substantia Nigra Pars Compacta And Ventral Tegmental Area Projections To The Striatum And Cortex, Nicholas Handfield-Jones

Electronic Thesis and Dissertation Repository

We investigated the connectivity of dopamine (DA) neurons emerging from the substantia nigra pars compacta (SNc) and ventral tegmental area (VTA) and targeting the dorsal striatum (DS), ventral striatum (VS), and prefrontal cortex (PFC). We used diffusion magnetic resonance imaging (dMRI) probabilistic tractography on human connectome project MRI data. We found that unlike conventional descriptions of DA pathways (i.e., nigrostriatal, mesolimbic, mesocortical), connectivity from both SNc and VTA each targeted DS, VS, and PFC. We also found that from the DS, VS, and PFC, a greater proportion of connections targeted the SNc as compared to the VTA. These findings suggest …

Neurodevelopmental Outcomes Of Infantile Hydrocephalus: An Fmri Case Study, Ikhlas Ahmed Hashi

Electronic Thesis and Dissertation Repository

Ventricle dilatation caused by infantile hydrocephalus may result in extensive damage of the posterior cortex (parietal and occipital lobes). We hypothesize that pathological changes in the development of the posterior cortex can be linked to non-verbal learning disabilities in children with previous infantile hydrocephalus. This case study will investigate the neurodevelopmental outcomes of 3 treated hydrocephalus patients, when compared to a group of healthy control children (n = 12). Within the hydrocephalus group, patients displayed differences in non-verbal test performance as well as parietal brain activation during an fMRI number comparison task. We associated these differences with clinical variables such …

Low Birth Weight And Post-Natal Diet Induced Alterations In Skeletal Muscle Oxygen Consumption And Fiber Type Composition, Megan Cedrone

Electronic Thesis and Dissertation Repository

Adverse in utero and postnatal conditions can increase susceptibility to metabolic syndrome (MS). Altered muscle respiration contributes to MS, but the effects of restricted oxygen and nutrients in utero on skeletal muscle mitochondria remain unknown. In this study guinea pig sows underwent uterine artery ablations mid-gestation, producing fetuses with low birth weight (LBW). Soleus muscle was collected near term or at four months of age, from LBW and control fetuses and offspring, where the offspring were fed either a Western Diet (WD) or a control diet (CD). Soleus muscles from LBW fetuses exhibit lower maximal respiration rates than normal birth …

The Role Of The Tau N-Terminal Phosphatase-Activating Domain And Phosphorylation At Thr175 In The Formation Of Tau Cytoplasmic Inclusions, Matthew A. Hintermayer

Electronic Thesis and Dissertation Repository

Cytoplasmic inclusions and fibrils of the microtubule-associated protein tau (tau protein) are a key neuropathological hallmark in tauopathies, including Alzheimer’s disease, chronic traumatic encephalopathy, and amyotrophic lateral sclerosis with cognitive impairment. Previous research has demonstrated that the phosphorylation of tau protein at Thr¹⁷⁵ is sufficient for the initiation of fibril formation both in vitro and in vivo. Here we use mutated tau protein constructs to demonstrate that phosphorylation at Thr¹⁷⁵ results in the aberrant exposure of an N-terminal phosphatase-activating domain (PAD). The tau PAD interacts with protein phosphatase 1 (PP1) leading to the activation of glycogen synthase …

Microvascular Stenosis In Critical Limb Ischemia: Role Of Partial Endothelial To Mesenchymal Transition, Jacqueline M. Chevalier

Electronic Thesis and Dissertation Repository

Critical limb ischemia (CLI) is a widespread and debilitating manifestation of atherosclerosis. Unfortunately, revascularization strategies are often precluded or unsuccessful, resulting in amputation. A major reason for treatment failure is likely co-existing abnormalities in ­­the microvasculature. However, the specific microvascular defects present in end-stage PAD in humans remain unknown.

The purpose of this study was to delineate abnormalities in the microvascular wall in the critically ischemic skeletal muscle of patients with CLI.

To elucidate the microvascular landscape in CLI, we studied human tibialis anterior and gastrocnemius muscles harvested from below-knee amputations of 10 individuals with CLI. Control muscles are from …

Modulation Of Inflammation Driven Wound Healing After Glaucoma Surgery, James J. Armstrong

Electronic Thesis and Dissertation Repository

Dysregulated wound healing contributes to most currently unanswered ophthalmological morbidity. Opacification and structure altering contractures compromise the delicate ocular anatomy upon which ocular function and healthy vision are reliant. Glaucoma filtration surgery, corneal stromal injury, proliferative vitreoretinopathy and age-related macular degeneration are major contributors to ocular morbidity – all with myofibroblast transdifferentiation and pathognomonic scarring activity at their core.

This thesis aims to revaluate the means by which dysregulated ocular wound healing is combated with evidence describing a novel strategy to mitigate its effects. A translational approach was used. An initial retrospective analysis of over ten thousand glaucoma surgeries found …

An Apodized-Aperture X-Ray Detector Design For Improved Image Quality In Mammography, Tomi F. Nano

Electronic Thesis and Dissertation Repository

X-ray imaging for early cancer detection, such as screening mammography, requires images with high signal-to-noise ratio (SNR) using low levels of radiation exposure. Conventional detectors consist of a matrix of sensor elements, producing images where each pixel corresponds to a single sensor element. This imposes a fundamental limitation on image contrast and SNR for imaging fine detail for a given exposure. The work presented here reconsiders x-ray image formation using a new x-ray detector design that synthesizes image pixels from a large number of very small sensor elements with the goal of optimizing contrast and SNR.

Our new detector design, …

Towards On-Line Plan Adaptation Of Unified Intensity-Modulated Arc Therapy Using A Fast-Direct Aperture Optimization Algorithm, Michael Macfarlane

Electronic Thesis and Dissertation Repository

External beam radiotherapy (EBRT) plays a vital role in the treatment of cancer, with close to half of all cancer patients receiving EBRT at some point over their course of treatment. Although EBRT is a well-established form of treatment, there are a number of ways in which EBRT could still be improved in terms of quality and efficiency for treatment planning and radiation dose delivery. This thesis reports a series of improvements made to EBRT.

First, we developed and evaluated a new treatment planning technique called unified intensity-modulated arc therapy (UIMAT) which combines the optimization and delivery of rotational volumetric …

Potential Role Of Extracellular Atp Released By Bacteria In Bladder Infection And Contractility, Behnam Abbasian

Electronic Thesis and Dissertation Repository

Urgency urinary incontinence (UUI), the result of conditions such as overactive bladder (OAB), could potentially be influenced by both commensal and urinary tract infection-associated bacteria. The sensing of bladder filling involves interplay between various parts of the nervous system eventually resulting in contraction of the detrusor muscle during micturition. Here we model host responses to various urogenital bacteria, firstly by using urothelial bladder cell lines and then with myofibroblast contraction assays. To measure responses, we examined calcium influx, gene expression and alpha smooth muscle actin deposition assays. We found that organisms such as Escherichia coli IA2 and Gardnerella vaginalis ATCC …

Texture Analysis And Machine Learning To Predict Pulmonary Ventilation From Thoracic Computed Tomography, Andrew Westcott

Electronic Thesis and Dissertation Repository

Chronic obstructive pulmonary disease (COPD) leads to persistent airflow limitation, causing a large burden to patients and the health care system. Thoracic CT provides an opportunity to observe the structural pathophysiology of COPD, whereas hyperpolarized gas MRI provides images of the consequential ventilation heterogeneity. However, hyperpolarized gas MRI is currently limited to research centres, due to the high cost of gas and polarization equipment. Therefore, I developed a pipeline using texture analysis and machine learning methods to create predicted ventilation maps based on non-contrast enhanced, single-volume thoracic CT. In a COPD cohort, predicted ventilation maps were qualitatively and quantitatively related …

Neural Correlates Of Enhanced Attentional Filtering Of Distractors Across Vs. Within Visual Hemifields In The Lateral Prefrontal Cortex, Maryam Nouri Kadijani

Electronic Thesis and Dissertation Repository

Attention allows us to focus on only important sensory stimuli in a world full of distractors. However, the ability to allocate attention to important targets becomes more difficult when the distractors are located within the same as compared to when they are in the opposite visual hemifield. The neural mechanisms underlying this effect remains unclear. We recorded neuronal responses in lateral prefrontal cortex (LPFC), an area involved in the generation of signals related to attention, of two macaque monkeys while they performed a covert spatial attention task in two different conditions. Two stimuli were either separate in the left and …

Translational Control Of Stress Induced Breast Cancer Plasticity, Michael Jewer

Electronic Thesis and Dissertation Repository

Cancer cell plasticity, whereby stem-cell-like properties are acquired in response to stress, represents a major challenge in cancer treatment. Using cell line and patient-derived xenograft (PDX) models, we demonstrate that translational reprogramming occurs in response to stresses such as hypoxia and chemotherapy which elicits stem cell properties in breast cancer. Other stresses like chemotherapy demonstrate the translational inhibition that has been well characterized as an integral hypoxic cellular response. The inhibition of translation is primarily regulated at initiation by mTOR/4E-BP1 and PERK/eIF2α signalling. We identify previously undescribed 5’ untranslated regions (5’UTRs) of plasticity-associated genes like NANOG, SNAIL and NODAL. …

The Purification Of Human Adult Progenitor Cell Types To Promote Angiogenesis, Stephen E. Sherman

Electronic Thesis and Dissertation Repository

Cellular transplantation strategies have aimed to combat critical limb ischemia (CLI) by inducing endogenous blood vessel regeneration. Transplantation of mesenchymal stromal cells (MSC) for CLI has proven safe and well-tolerated but demonstrated only modestly improved clinical outcomes explained in part by a lack of MSC survival and/or potency in ischemic tissues. This thesis focuses on the development of improved transplantation strategies for patients with CLI utilizing purified pro-angiogenic subsets of MSC and endothelial colony forming cells (ECFC) seeded within decellularized adipose tissue (DAT) bioscaffolds. First, I investigated whether purification of bone marrow-derived MSC based on a conserved stem cell function, …

Improving The Genetic Diagnosis Of Familial Hypercholesterolemia, Michael Iacocca

Electronic Thesis and Dissertation Repository

Familial hypercholesterolemia (FH) is a genetic disorder of severely elevated low-density lipoprotein (LDL) cholesterol that is widely underdiagnosed and undertreated. To improve the identification of FH and initiate timely and appropriate treatment strategies, genetic testing is becoming increasingly offered worldwide as a central part of diagnosis. I describe three main ways providing a genetic diagnosis in FH can be improved. First, next-generation sequencing (NGS)-based approaches can be used to reliably identify large-scale variant types known as copy number variations (CNVs) in the LDL receptor gene (LDLR); second, NGS methodology can be further applied to extend CNV screening to …