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Type d'Item : Item , A Screen for Novel Regulators of Polyphosphate Accumulation in Escherichia Coli Identifies Genes Involved in Envelope Stress, Central Metabolism, and Phosphate Homeostasis(Université d'Ottawa | University of Ottawa, 2026-07-21) Simms, Abby; Downey, MichaelPolyphosphates (polyP) are chains of inorganic phosphate that are present in a wide variety of organisms such as yeast, mammals, and bacteria. Despite the interesting and diverse functions of polyP across systems, bacterial polyP is of particular interest to researchers due to its contributions to bacterial survival. Across bacterial taxa, polyP accumulation promotes resistance to diverse environmental stressors, can act as a protein chaperone, and positively regulates pathogenicity, making polyP an interesting target to help treat bacterial infections. In the gram-negative bacterium, Escherichia coli, polyP is synthesized from ATP by a single polyphosphate kinase (PPK) enzyme, and is degraded into inorganic phosphate by an exopolyphosphatase. PolyP synthesis by PPK in E. coli is stress-dependent, as there is little to no detectable polyP present in the absence of stress, followed by the rapid accumulation of polyP upon exposure to stressors such as nutrient limitation. Despite this stress-specific activity, the exact trigger(s) of PPK activity at the onset of stress remain uncharacterized, as PPK’s expression and in vitro activity do not correlate with polyP accumulation. To address this open question, this work aims to characterize novel regulators of polyP that can be leveraged to investigate the mechanism of PPK activation. To achieve this, we conducted a screen of single-gene deletion mutants targeting a highly conserved family of signalling proteins called two-component systems (TCS), which have existing links to polyP biology. In doing so we highlighted five polyP-regulators, three of which (cpxA, arcB, and arcA) have not yet been reported in the literature. Upon following up on one of our hits, the envelope stress-sensing histidine kinase CpxA, we found that activation of the CpxRA TCS promotes an increase in polyP accumulation. However, polyP regulation by this system appears to be independent of PPK or PPX expression, leaving the door open to future analyses of PPK regulation, possibly at the level of localization or oligomerization. Overall, this work contributes to our fundamental knowledge surrounding the relationship between PPK activity, polyP accumulation, and cellular stress.Type d'Item : Item , Point-of-Care Ultrasound Assessment of Left Ventricular Function in Rapid Atrial Fibrillation or Flutter Patients in the Emergency Department(Université d'Ottawa | University of Ottawa, 2026-07-21) Giannakakis, Sophia-Maria; Perry, Jeffrey J.; Stiell, IanObjective: The aim of this thesis is to evaluate the utilization of point-of-care ultrasound (POCUS) for left ventricular function (LVF) assessment by emergency physicians for the diagnosis and management of heart failure in rapid atrial fibrillation or flutter. Methods: A national survey of emergency physicians explored the integration and perceived barriers related to POCUS use in rapid atrial fibrillation or flutter. Subsequently, a health records review at The Ottawa Hospital ED studied diagnostic agreement of POCUS LVF assessment between ED physicians, cardiologists, and ED POCUS expert. Secondary outcomes were also analyzed regarding rapid atrial fibrillation or flutter management. Results: A fair level of agreement between cardiologists and ED physicians (k= 0.34 CI 95% 0.10-0.58) and moderate agreement was found between cardiologists and ED POCUS expert physician (kappa = 0.63 (CI 95% 0.43-0.82). A higher proportion of rapid atrial fibrillation/flutter patients with ED-performed POCUS were admitted to hospital (40% vs 19%, p<0.0001) and rate controlled with beta blocker (38% vs 24%, p=0.009) or digoxin (14% vs 5%, p=0.007). Conclusion: The utilization of POCUS in the rapid atrial fibrillation/flutter patients can help guide diagnosis and management of heart failure in the ED.Type d'Item : Item , Quantitative MRI as a Biomarker of Disease Severity in Neuromuscular Disease(Université d'Ottawa | University of Ottawa, 2026-07-21) Satarkar, Tanay; Warman Chardon, JodiIntroduction: Oculopharyngeal muscular dystrophy (OPMD) is a slowly progressive disorder marked by ptosis, dysphagia, and proximal muscle weakness. Reliable biomarkers for monitoring are limited, making progression difficult to track in clinics and future trials. Quantitative MRI (qMRI), particularly fat-fraction (FF) and water measures offer a non-invasive way to assess muscle involvement and follow change over time. Aim: To evaluate 97 muscles in OPMD using qMRI and determine if diffusion-related MRI markers [apparent diffusion coefficient (ADC) intravoxel incoherent motion (IVIM)], and T2 relaxation time identify earlier signs of disease activity compared to muscle FF. Methods: The study included 52 participants, 40 patients with OPMD and 12 controls with whole body 3T qMRI. For FF and ADC, 97 muscles were segmented and 24 thigh muscles were segmented for IVIM and T2 map using ITK SNAP version 3.8.0. Statistical analyses used GraphPad Prism and R-studio using, Wilcoxon unpaired tests and Spearman correlation p <0.05. Results: Muscles such as adductor magnus (41.2±28.9 %), soleus (39.2±25.9 %), and biceps femoris long head (BL) (33.8±25.2 %), showed higher FF. Higher FF was linked to a stronger negative correlation between FF-ADC, adductor magnus (spearman’s ρ = -0.90), soleus (spearman’s ρ =-0.83), biceps femoris long head (spearman’s ρ = -0.87)), and FF-IVIM true diffusion (spearman’s ρ =-0.89 CI, -0.94, -0.80 respectively). IVIM perfusion-fraction correlated positively with FF in adductor magnus and biceps femoris long head (spearman’s ρ = 0.80) in the early disease duration period (0-5 years). Exploratory disease-duration stratification showed ADC did not rise prior to fat replacement, as might occur with inflammation and edema; instead, ADC decreased as fat replacement increased. Discussion: FF is a sensitive marker of disease severity and shows a strong negative correlation with diffusivity markers. In this cross-sectional analysis, diffusion values do not rise before fat replacement onset. Identifying sensitive biomarkers of OPMD severity and disease progression is important to identify treatment windows for future trials.Type d'Item : Item , Iatrogenic superior gluteal nerve stretch in surgical fixation of acetabular fractures through a Kocher-Langenbeck approach: a cadaveric study(2026-05-18) Nitikman, Michael; Tubin, Nick; Swift, Brendan; Liew, Allan; Wilkin, Geoffrey; Papp, StevenAbstract Objectives Fixation of posterior column fractures through a Kocher‒Langenbeck approach requires retraction of the gluteus medius and minimus and, therefore, the superior gluteal nerve (SGN). Iatrogenic nerve injury is a concern that may result in hip abductor weakness and altered gait patterns. The purpose of this study was to measure the amount of stretch to the SGN relative to common placement of a retractor during a posterior approach to the acetabulum for fracture fixation. Methods An IRB-approved cadaveric study was performed. The Kocher–Langenbeck approach was performed on ten hips from five cadaveric donors. The superior gluteal nerve was reproducibly identified and isolated, exiting the greater sciatic notch (GSN) and traversing between the gluteus minimus and medius. The length of the nerve was measured with a caliper between the GSN and its insertion into the gluteus medius, along its longest segment. An acetabular retractor was placed anterior to the gluteal pillar, and the length of the SGN was measured with the retractor positioned 30 and 60 degrees relative to the horizontal. The measurements were completed both with the leg in the neutral position and with the leg in 15 degrees of abduction. Interobserver reliability was measured. The percent change in the length of the SGN relative to retractor position was calculated. Results The SGN was consistently found exiting the most proximal aspect of the GSN. The length of the SGN from the GSN to the muscular insertion was 29.3 mm (+/- 7.4 mm). The nerve stretched 28% of its length at 30 degrees of retraction and 56.9% at 60 degrees of retraction. The nerve was stretched over a short segment and tethered at the level of the GSN. The intraclass correlation coefficient (ICC) was excellent between the two observers (0.92 [0.87–0.95]). Significant changes in the length of the nerve were found in four hips with the retractor at 30 degrees and all ten hips at 60 degrees. Conclusions The superior gluteal nerve is subjected to significant stretching during anterior retraction of the gluteal muscles during acetabular fracture fixation through a Kocher–Langenbeck approach. A clinical study with electrodiagnostic studies and gait analysis is needed to determine whether iatrogenic nerve stretch is consequential.Type d'Item : Item , “Healthy bodies, healthy minds”: barriers and solutions to implementing a menstrual hygiene management program in South Sudan(2026-05-23) Razavi, S. D.; Cummings, Hanson; Labonté, Jocelyne; Kapiriri, Lydia; Sohani, SalimAbstract Background Menstrual hygiene management (MHM) can be challenging for women and girls living in conflict-affected low- and middle-income countries, where access to menstrual products, soap, water, and private sanitation facilities is often limited. In response to these challenges, the Canadian Red Cross, in partnership with the South Sudan Red Crescent and the South Sudanese Government, implemented the Healthy Bodies Healthy Minds (HBHM) program from 2020–2023 to support MHM in South Sudan. Despite growing attention to MHM needs, few studies have examined the on-the-ground realities of implementing MHM programming in fragile settings. To address this gap, this study aimed to (i) describe the implementation of HBHM, (ii) identify barriers faced during implementation, (iii) identify potential solutions to overcome barriers, and (iv) understand the impact of the COVID-19 pandemic on program delivery. Methods Data was collected through key informant interviews with individuals involved in program design and implementation and were analyzed via thematic analysis. A total of 14 respondents were interviewed. Results Respondents identified several interrelated and compounding barriers, including resource constraints, logistical challenges, competing stakeholder interests/priorities, ongoing conflict, and climate change. To mitigate these barriers and improve the delivery of MHM programs, respondents recommended solutions and strategies such as extending implementation timelines, planning program activities around anticipated climate events, and strengthening inter-organizational collaboration. The COVID-19 pandemic introduced additional barriers, particularly by restricting the movement of people and goods. However, it also yielded unexpected benefits, notably expanding the project’s reach beyond the target group of girls to the broader community. Conclusions Implementation of the HBHM program was impacted by several interrelated and compounding factors including resource constraints and logistical challenges, protracted conflict, climate change, and COVID-19, however, collaboration between implementing partners and agility in the approach to program rollout supported enhanced program reach. International partnerships enabled community-level implementation, which proved especially effective for continued program implementation. Additionally, the shift to a more community-based model resulted in benefits to the broader community, offering another key insight that should be considered in the design of future MHM programs in South Sudan and similar contexts.