VictorJuiz/thesis huggingface dataset:
The TNFα/S1P Signalling Axis Mediates Elevated Myogenic Tone in Diabetes Mellitus

Diabetes causes changes in microvascular function that can ultimately promote multi-organ failure. Microvascular resistance arteries, integral to blood pressure, tissue perfusion and capillary integrity, are targets for dysregulation in diabetes. Resistance arteries function by adapting their diameter in response to transmural pressure through an intrinsic property of vascular smooth muscle cells (VSMCs), termed the myogenic response. Altered myogenic tone compromises tissue perfusion and aggravates hypertension; permanent structural changes to the microcirculation can result. The bioactive sphingolipid sphingosine-1-phosphate (S1P) is a central regulator of the myogenic response, with the pressure-induced activation of the S1P-generating enzyme sphingosine kinase 1 (Sphk1) and activation of the S1P2 receptor (S1P2R) as key elements. This signalling pathway and hence, myogenic tone are governed by the cytokine tumour necrosis factor alpha (TNFα). Given the association of diabetes with TNFα-induced inflammation, I hypothesized that TNFα recruits the S1P pathway to induce functional changes in resistance arteries. This thesis utilized pressure myography techniques on isolated resistance arteries. To understand the mechanisms by which myogenic tone is affected, I titrated a standard diabetes mouse model (high fat diet + streptozotocin; HFD/STZ), to induce a mild increase in blood glucose levels. HFD/STZ treatment produced a progressive myogenic tone augmentation in mesenteric and olfactory cerebral arteries; HFD alone had no effect on blood glucose or resistance artery myogenic tone. Using gene deletion models that eliminate TNFα or Sphk1, I demonstrated that VSMC TNFα drives augmented myogenic tone via enhanced S1P signalling. Inhibiting both TNFα (etanercept) and S1P (JTE013) signalling was therapeutically utilized to specifically correct this defect. My results add diabetes to a diverse group of microvascular diseases driven by pathological TNFα/S1P signalling. My data demonstrate that microvascular reactivity is an early disease marker and advocates establishing therapies that strategically target the microcirculation in diabetes patients.

Advisor: Bolz, Steffen-Sebastian
The Associative Deficit in Aging: Insights from Task and Resting State Functional Neuroimaging

Human aging is characterized by significant reductions in the ability to remember associations between items, despite having intact memory for single items. In general, neuroimaging studies that investigate the age differences in episodic memory find that older adults show less selective neural recruitment across experimental tasks and weaker resting state functional connectivity (rs-FC) relative to younger adults. However it is unclear whether these neural effects account for older adults’ deficit with associative memory. I used functional magnetic resonance imaging to investigate whether task effects, rest effects, and the dynamic interaction between task and rest relate to the associative deficit. Young and older adults were scanned while at rest and while performing incidental item and associative encoding tasks. As expected, older adults had poorer memory for associations compared to younger adults. In terms of task effects, older adults had less distinct patterns of brain activity during associative encoding and less selective brain activity predicted poorer associative memory. Resting state fluctuations also related to the associative deficit, with older adults showing greater modulation of rs-FC following item and not associative encoding. Furthermore, broader neural recruitment during post-item and post-associative encoding related to better memory. Lastly, older adults failed to show a dissociation between rs-FC in the default and dorsal attention networks and task activity; the lack of dissociation related to associative memory performance and not item memory performance. My results suggest that the associative deficit in older adults results from a lack of distinctiveness in neural activity, which occurs at encoding and is reflected in the interplay between rs-FC and task activity. A subset of higher performing older adults were able to modulate rs-FC in response to task demands and were able to recruit additional neural resources, interpreted as a compensatory mechanism that is engaged to reduce age-related deficits in associative memory.

Keywords: aging
associative deficit
fMRI
memory
resting state networks
Advisor: Grady, Cheryl L.
An Investigation of the Cellular Responses and the Role of the Exocyst Complex in Early Stages of Pollen-Pistil Interactions in Brassicaceae

In Brassicaceae, complex signaling events occur at the early stages of interaction between the pollen grain and the stigmatic surface at the top of the pistil. The initial events of pollen-pistil interactions mediate the recognition of the pollen grain that will lead to the acceptance of a compatible pollen or the rejection of an incompatible pollen. There has been much research into this field in the Brassicaceae, as this family includes many agriculturally important crops; e.g. canola, radish, turnip, cabbage, and many others. My thesis project has focused on the cellular and molecular mechanisms underlying pollen-pistil interactions in the experimentally tractable Arabidopsis thaliana (a self-compatible species). I have also investigated the cellular events regulating pollen-pistil interactions in Arabidopsis lyrata (a self-incompatible species) and Brassica napus Westar and W1 cultivars (a compatible and self-incompatible species, respectively). Compatible pollinations are driven by the ability of the pistil to provide the resources for an acceptable pollen grain to hydrate, germinate and fertilize the ovule. It has been proposed that the delivery of stigmatic resources to the compatible pollen grain is facilitated by polarized vesicle secretion at the pollen-pistil interface. The self-incompatibility response, however, is hypothesized to inhibit the trafficking of stigma-derived compatibility factors to the self pollen to prevent pollen tube entry and hinder fertilization, encouraging genetic diversity within the species. In this thesis, I present my findings on the cytological responses of the stigmatic papillae to the compatible and self-incompatible pollen grains in a detailed time-course. My ultrastructural observations revealed the presence of targeted and localized vesicle secretion at the pollen contact site whereas the absence of secretion after self-incompatible pollination. The octameric exocyst complex is proposed to mediate the aforementioned vesicular trafficking in the stigmatic papillae after compatible pollination. Previously, Exo70A1, a member of the exocyst complex has been identified as an essential component for the acceptance of compatible pollen in A. thaliana. We analyzed the Stigmatic female fertility in RNAi silencing lines for the remaining seven exocyst subunits. Interestingly our novel results uncovered that all eight exocyst subunits are required for the acceptance of compatible pollen in A. thaliana.

Advisor: Goring, Daphne
Mechanisms of Cholinergic Neuromodulation of Prefrontal Cortex in Health and Disease: A Combined Whole-Cell Electrophysiology and Multiphoton Calcium Imaging Approach

The neuromodulation of the prefrontal cortex (PFC) by acetylcholine is essential for optimal executive function, where it exerts robust excitatory actions together with complex calcium ion signals via the nicotinic and muscarinic acetylcholine receptors. This thesis examines how cholinergic calcium fluxes regulate the ability of acetylcholine to excite prefrontal circuits and how these interactions are disrupted in rodent models of psychiatric and neurological illness. Using whole-cell electrophysiology together with multiphoton calcium imaging in slices of rodent PFC, I have found that cholinergic calcium mobilization can exert important regulatory control over cholinergic excitability: by enhancing sub-threshold cholinergic excitation and by constraining supra-threshold effects via the modulation of spike output. Importantly, these distinct interactions were disrupted in two separate models of neuropsychiatric disease with documented cognitive dysfunction. First, in pyramidal cells of prefrontal output layer 5, acetylcholine-induced calcium release was found to potentiate excitatory cholinergic currents via the electrogenic process of sodium/calcium exchange. This phenomenon was found to emerge in young adulthood, when executive function typically reaches maturity. What is more, this developmental consolidation of cholinergic signaling was abolished subsequent to the early stress of repeated maternal separation—a model of psychiatric vulnerability—where cholinergic responses retained an adolescent phenotype accompanied by a disruption in the expression of multiple developmentally-regulated genes associated with Gαq and calcium signaling. Second, in a well-characterized model of Alzheimer’s disease, I have found that layer 6 PFC pyramidal cells, which are known to be essential for peak attentional performance, are unable to sustain cholinergic excitation to the same extent as those of non-transgenic littermate controls as a result of the excessive activation of calcium-activated hyperpolarizing conductances. Further, I demonstrate that cholinergic excitation can be improved in the cortex of these mice by pharmacological blockade of SK channels, suggesting a novel target for the treatment of executive dysfunction. In sum, this thesis characterizes two distinct and potentially complementary mechanisms whereby calcium can shape cholinergic excitability in prefrontal circuits essential to executive function and how these interactions are disrupted in models of brain disease with documented cognitive dysfunction.

Keywords: Acetylcholine
Calcium imaging
Electrophysiology
Muscarinic
Nicotinic
Prefrontal cortex
Advisor: Lambe, Evelyn K
Socioeconomic Position, Modifiable Risk Factors and Coronary Heart Disease Incidence in Canada

Coronary heart disease (CHD) is a leading cause of morbidity and mortality in Canada. Socioeconomic position (SEP; typically measured as education, occupation and/or income) is an important CHD risk factor, in addition to conventional risk factors (e.g. smoking, poor nutrition, physical inactivity, obesity, high blood pressure, diabetes or cholesterol). Evidence to inform which population health interventions will optimally reduce both the population level and social inequalities in CHD is urgently needed in Canada. The overall goal of this dissertation was to explore the relationship between SEP, modifiable risk factors and CHD incidence. The dissertation consists of four related manuscripts, each making a contribution to this area of research. The first manuscript assessed the potential use of mathematical simulation models to evaluate the impacts of population health interventions on social inequalities in CHD. This review served as a conceptual framework for this dissertation, highlighting a number of gaps in research evidence further explored in dissertation chapters. The second manuscript undertakes a causal mediation analysis to examine the direct and indirect pathways linking SEP and incident heart disease in a Canadian population-based cohort study. By assessing individual mediation pathways through modifiable CHD risk factors, the goal of this manuscript was to highlight potential targets for population health interventions that will result in the greatest reduction in social inequalities in CHD. In the third manuscript the ability of the Framingham CHD Risk Score prediction algorithm to predict future CHD incidence across SEP groups was assessed. The results from this study tested an important methodological assumption regarding the risk prediction tool used in the Population Health Model for Cardiovascular Disease (POHEM:CVD), to enable accurate simulation of CHD incidence by SEP group. Finally, the fourth manuscript assessed the validity of socioeconomic trends in modifiable CHD risk factors in Canada from 2001 to 2021 using POHEM:CVD. Combined, this body of work provides evidence regarding the potential benefit of targeting modifiable CHD risk factors on reducing population and social inequalities in CHD in Canada.

Keywords: Heart Disease
Population Health Intervention Research
Simulation modelling
Social Determinants of Health
Advisor: Mustard, Cameron A
Smith, Peter M
Point-of-Care Diagnostics for Lung Transplantation

Over the last few decades, lung transplantation (LTx) has become a well-established therapy for patients suffering from end-stage lung disease. Despite the many innovations that have occurred in recent years, the outcomes following LTx still lag behind those of other organ transplant procedures due to a lack of technologies that could monitor predictive biomarkers. Recently, several genomic and proteomic analytes have been identified that are prognostic of LTx outcome; however, traditional analytical methods are impractical for use in the transplant setting. Rapid analysis of molecular biomarkers reporting on the initial and long-term status of a donated organ would improve utilization rates and transplant outcomes. The work herein focuses on developing a novel class of chip-based sensors that would enable direct analysis of mRNAs and proteins that are correlated with the suitability of a lung for transplant. The biosensing approach utilized in these studies was performed using a simple and elegant electrochemical reporter system with metal electrodes of varying morphologies and sizes. By fabricating fractal circuit sensors (FraCS), we demonstrated the technological and biological validation required for a point-of-care (POC) diagnostic device to be used for gene quantitation in the transplant setting. This approach was applied to confirm the clinical validity of previously reported biomarkers (IL-6, IL-10, EGLN1, and ATP11B) and, importantly, was used to develop a FraCS prediction model (FPM), which was highly predictive (AUC 0.82) of primary graft dysfunction (PGD) in donor lungs. Using nanostructured microelectrodes (NMEs), a sensing platform was developed to detect two proteins implicated in chronic lung rejection: TGFβ1 and ET-1 – biomarkers involved in restrictive allograft syndrome (RAS) and bronchiolitis obliterans syndrome (BOS). We highlight novel strategies used for the electrochemical detection of small (

Keywords: Biomarkers
Diagnostics
Lung Transplantation
Nanotechnology
Advisor: Kelley, Shana O
Printed Educational Materials for Primary Care Physicians

In primary care settings, primary care physicians (PCPs) commonly have multiple brief visits, often with complex patients and have little time to review the multitude of clinical evidence available that may be relevant to their patients’ needs. This dissertation examines printed educational materials (PEMs) as a tool to facilitate the dissemination of clinical information for PCPs. I use the Technology Acceptance Model to study how the perceived ease of use and perceived usefulness of PEMs influences PCP attitude, intention, and use of PEMs. This dissertation is composed of three studies: 1) A systematic review of 40 studies of PEMs for PCPs to determine the effect of PEMs on patient and physician outcomes, 2) A focus group study to determine PCP preferences for the design and content of PEMs, and 3) The redesign and subsequent usability testing by PCPs of an existing PEM. The results of the systematic review demonstrate that PEMs do not have an effect on patient outcomes or physician cognition or behaviour outcomes. I also conclude that the included studies are limited by very poor intervention reporting. In the second paper, I highlight PCP preferences for PEMs, including that PEMs be relevant to their primary care patient population, short, concise, and specific in terms of their practice recommendations. I also present a list of these preferences for use by individuals who create PEMs. Lastly, in the third paper I redesigned an existing PEM using design principles and user preferences. I conducted a modified discrete choice experiment and usability testing to determine if the redesigned version is more usable and more often selected than the original. The redesigned PEM scored significantly higher on the System Usability Scale and was selected more often than the original version by PCPs across two settings: an opportunistic and a controlled setting. The opportunistic setting was at a large Canadian conference for family physicians in Quebec City, Canada. The controlled setting experiments were conducted as individual sessions at St. Michael’s Hospital in Toronto, Canada or at the participant’s clinic. This dissertation concludes that though PEMs are not found to be effective for changing patient or physician behaviour in their current state, there is an opportunity to optimize their design and potentially increase their effect on both physician and patient outcomes.

Keywords: Evidence-based medicine
Knowledge translation
Primary care
Advisor: Straus, Sharon E
Lifting Problems, Cross-fiberedness, and Diffusive Properties on Elliptic Surfaces

Given an elliptic curve E˜ over Fp the field of p elements, and given points P˜ and Q˜ in E˜(Fp) such that Q˜ = nP˜, the Elliptic Curve Discrete Logarithm Problem (ECDLP) is to find n. The difficulty of the ECDLP is the foundation for much of modern cryptographic security. S. Miri and V.K. Murty considered a lifting problem in which one asks to find lifts of points P ∈ E˜( Fp) to an appropriately chosen elliptic curve over Q. They saw that the ECDLP would be equivalent to this lifting problem if one could find lifts of E˜ with certain properties. We consider a variant of this lifting problem, which we see is unconjecturally equivalent to the ECDLP. Furthermore, we relate these ideas to a conjecture of B. Mazur which asserts that for any non-constant elliptic fibration {Et} t∈Q, the set { t ∈ Q : rk(Et( Q)) > 0} is finite or dense in R with respect to the real topology. Particularly interesting to us are elliptic surfaces considered by R. Munshi on which there is a second fibration by genus one curves such that the two fibrations interact in nice ways. On these surfaces, using the second fibration, non-torsion points are "diffused'' from one fiber Et to others, and hence positive rank fibers are "diffused'' through R, allowing one to conclude Mazur's conjecture for these families. We show that this process also "diffuses'' certain other properties of fibers. We see that, under certain conditions, the set of fibers having a list of properties motivated by our lifting problems is either finite or dense in R. Moreover, we study the dynamics of this process of diffusion, allowing us to bound the proportion of times our process produces fibers with the desired properties. We show that the probability that the diffusion process produces a lift with all of the (seemingly unrelated) properties is the product of each of the respective probabilities up to a controllable error bound. Hence we see that whether the output fiber of the diffusion process has these properties is "asymptotically independent.''

Keywords: cryptography
elliptic surfaces
lifting
Advisor: Murty, Kumar
Dissociative Attachment and Reaction on Silicon

Scanning tunneling microscopy (STM) and density functional theory (DFT) were used to study two types of reaction at a crystal surface: long-range migration and dissociative attachment. We developed the first dynamical model for the observation of long-range migration of ethylene across the rough Si(100) surface. Ab initio molecular dynamics revealed two requirements for this long-range migration: first the molecule must leave the surface through ‘ballistic’ motion, traveling out of range of its roughness, second it must ‘bounce’ like a skipping-stone to reach the observed distances. Additionally, comparable behavior was predicted for atomic chlorine following electron-induced dissociation of chlorophenyl at Cu(110). In a following chapter we examined the factors governing the choice of pathway in the dissociative attachment (DA) of H2 and HCl at Si(100). In a computational study, we correlated the location of the energy barrier along the minimum-energy pathway with the separation of chemisorbed products: an ‘early’ barrier for reaction at closely-separated silicon atoms and a ‘late’ barrier for more-widely separated silicons, suggesting a means of 'steering' the reaction by reagent translation or vibration. In the remainder of the thesis DA at Si(100) was examined for two families of molecules, a series of hydrogen halides and of primary alkyl alcohols. For the hydrogen halides we observed three patterns of DA, unaltered in their relative yields by temperature change. A detailed study of the molecular dynamics for hydrogen bromide linked the choice of pathway to the sequential approach to the surface of the light H followed by the heavy Br. The charge flow resulting from the attachment of H explained the preference for Br to react ‘Inter-Dimer’. For the family of alcohols, methanol, ethanol, 1-propanol, 1-butanol, and 1-pentanol, we again observed a dominant 'Inter-Dimer' reaction path, rather than the previously-accepted 'On-Dimer' mechanism. Neither theory nor experiment gave evidence of a significant alteration in energy-barrier along the series. This finding contrasted with the experimental and theoretical observations by previous workers in which the energy-barrier for DA at Si(100) increased with increasing alkyl chain length along a series of 1-bromoalkanes. The difference here is the absence of ‘chain-lifting’ during the alcohols’ reactions.

Keywords: density functional theory
dissociative attachment
reaction dynamics
scanning tunneling microscopy
silicon
surface science
Advisor: Polanyi, John C.