Cerebral blood flow is associated with matrix metalloproteinase levels during the early symptomatic phase of concussion.

Concussion is associated with disrupted cerebral blood flow (CBF), although there appears to be substantial inter-individual variability in CBF response. At present, the mechanisms of variable CBF response remain incompletely understood, but one potential contributor is matrix metalloproteinase (MMP) expression. In more severe forms of acquired brain injury, MMP up-regulation contributes to CBF impairments via increased blood-brain barrier permeability.

Brain function associated with reaction time after sport-related concussion.

Concussion is associated with significant functional disturbances in the first week post-injury. Computerized neurocognitive testing tools have become widely adopted in concussion management, to identify specific domains of impairment and obtain more objective measures of recovery. Reaction time (RT) slowing is a common sequela of concussion, however, the functional brain networks that underlie RT performance remain under-studied in both healthy and concussed athletic cohorts.

Neurometabolites and sport-related concussion: From acute injury to one year after medical clearance.

Sport-related concussion is associated with acute disturbances in neurometabolic function, with effects that may last weeks to months after injury. However, is presently unknown whether these disturbances resolve at medical clearance to return to play (RTP) or continue to evolve over longer time intervals. Moreover, little is known about how these neurometabolic changes correlate with other measures of brain physiology.

Distinguishing cognitive effort and working memory load using scale-invariance and alpha suppression in EEG.

Despite being intuitive, cognitive effort has proven difficult to define quantitatively. Here, we proposed to study cognitive effort by investigating the degree to which the brain deviates from its default state, where brain activity is scale-invariant. Specifically, we measured such deviations by examining changes in scale-invariance of brain activity as a function of task difficulty and posited suppression of scale-invariance as a proxy for exertion of cognitive effort.

Remote ischemic conditioning improves outcome independent of anesthetic effects following shockwave-induced traumatic brain injury.

Traumatic brain injury due to primary blast exposure is a major cause of ongoing neurological and psychological impairment in soldiers and civilians. Animal and human evidence suggests that low-level blast exposure is capable of inducing white matter injury and behavioural deficits. There are currently no effective therapies to treat the underlying suspected pathophysiology of low-level primary blast or concussion.

Sex Differences in Cerebral Blood Flow Associated with a History of Concussion.

Growing evidence suggests that a history of sport concussion may lead to long-term changes in brain physiology, with cerebral blood flow (CBF) being particularly sensitive to injury. However, it is unknown whether these changes are sex specific. The goal of this study was to evaluate sex differences in CBF of asymptomatic athletes, with and without a history of concussion (HOC) using arterial spin labeling (ASL).

White matter during concussion recovery: Comparing diffusion tensor imaging (DTI) and neurite orientation dispersion and density imaging (NODDI).

Concussion pathophysiology in humans remains incompletely understood. Diffusion tensor imaging (DTI) has identified microstructural abnormalities in otherwise normal appearing brain tissue, using measures of fractional anisotropy (FA), axial diffusivity (AD), and radial diffusivity (RD). The results of prior DTI studies suggest that acute alterations in microstructure persist beyond medical clearance to return to play (RTP), but these measures lack specificity.

Evaluating Cerebrovascular Reactivity during the Early Symptomatic Phase of Sport Concussion.

Cerebrovascular reactivity (CVR) indexes the ability of blood vessels to respond to vasoactive stimuli and may be a sensitive biomarker of concussion. However, alterations in whole-brain CVR remain poorly understood during the early symptomatic phase of injury. In this study, CVR was assessed using blood-oxygenation-level dependent functional magnetic resonance imaging (BOLD fMRI) combined with a respiratory challenge paradigm; resting cerebral blood flow (CBF) was also evaluated using arterial spin labeling (ASL).

Connectomic markers of symptom severity in sport-related concussion: Whole-brain analysis of resting-state fMRI.

Concussion is associated with significant adverse effects within the first week post-injury, including physical complaints and altered cognition, sleep and mood. It is currently unknown whether these subjective disturbances have reliable functional brain correlates. Resting-state functional magnetic resonance imaging (rs-fMRI) has been used to measure functional connectivity of individuals after traumatic brain injury, but less is known about the relationship between functional connectivity and symptom assessments after a sport concussion.

Bone-Marrow-Derived Endothelial Progenitor Cell Treatment in a Model of Lateral Fluid Percussion Injury in Rats: Evaluation of Acute and Subacute Outcome Measures.

Traumatic brain injury (TBI) continues to be a serious health care issue while therapies to treat TBI remain elusive. Promising results from the use of endothelial progenitor cells (EPCs) in numerous disease states highlight the pleiotropic capacity of this cell type. We have previously demonstrated that EPC-conditioned media reduces axonal degeneration subsequent to in vitro oxygen-glucose deprivation insult and concurrently improves white matter and microvascular outcome in vivo after mid-line fluid percussion injury.

The first week after concussion: Blood flow, brain function and white matter microstructure.

Concussion is a major health concern, associated with short-term deficits in physical function, emotion and cognition, along with negative long-term health outcomes. However, we remain in the early stages of characterizing MRI markers of concussion, particularly during the first week post-injury when symptoms are most severe. In this study, 52 varsity athletes were scanned using Magnetic Resonance Imaging (MRI), including 26 athletes with acute concussion (scanned 1-7 days post-injury) and 26 matched control athletes.

Determining rates of overweight and obese status in children using electronic medical records: Cross-sectional study.

Objective: To determine the prevalence of overweight and obese status in children by age, sex, and visit type, using data from EMRALD (Electronic Medical Record Administrative data Linked Database).

Design: Heights and weights were abstracted for children 0 to 19 years of age who had at least one well-child visit from January 2010 to December 2011. Using the most recent visit, the proportions and 95% CIs of patients defined as overweight and obese were compared by age group, sex, and visit type using the World Health Organization growth reference standards.

Research projects in the Surgeon-Scientist and Clinician-Investigator programs at the University of Toronto (1987-2016): a cohort study.

Background: Physicians have traditionally been at the forefront of medical research, bringing clinical questions to the laboratory and returning with ideas for treatment. However, we have anecdotally observed a decline in the popularity of basic science research among trainees. We hypothesized that fewer resident physicians have been pursuing basic science research training over time.

The Functional Segregation and Integration Model: Mixture Model Representations of Consistent and Variable Group-Level Connectivity in fMRI.

The brain consists of specialized cortical regions that exchange information between each other, reflecting a combination of segregated (local) and integrated (distributed) processes that define brain function. Functional magnetic resonance imaging (fMRI) is widely used to characterize these functional relationships, although it is an ongoing challenge to develop robust, interpretable models for high-dimensional fMRI data. Gaussian mixture models (GMMs) are a powerful tool for parcellating the brain, based on the similarity of voxel time series.

Factors associated with out-of-hospital cardiac arrest with pulseless electric activity: A population-based study.

Background: Many patients with out-of-hospital cardiac arrest present with pulseless electric activity (PEA) rather than shockable rhythm. Despite improvements in resuscitation care, survival of PEA patients remains dismal. Our main objective was to characterize out-of-hospital cardiac arrest patients by initial presenting rhythm and to evaluate independent determinants of PEA.

Mental health service use by recent immigrants from different world regions and by non-immigrants in Ontario, Canada: a cross-sectional study.

Background: Given that immigration has been linked to a variety of mental health stressors, understanding use of mental health services by immigrant groups is particularly important. However, very little research on immigrants' use of mental health service in the host country considers source country. Newcomers from different source countries may have distinct experiences that influence service need and use after arrival.

Therapeutically Targeting Tumor Necrosis Factor-α/Sphingosine-1-Phosphate Signaling Corrects Myogenic Reactivity in Subarachnoid Hemorrhage.

Background And Purpose: Subarachnoid hemorrhage (SAH) is a complex stroke subtype characterized by an initial brain injury, followed by delayed cerebrovascular constriction and ischemia. Current therapeutic strategies nonselectively curtail exacerbated cerebrovascular constriction, which necessarily disrupts the essential and protective process of cerebral blood flow autoregulation. This study identifies a smooth muscle cell autocrine/paracrine signaling network that augments myogenic tone in a murine model of experimental SAH: it links tumor necrosis factor-α (TNFα), the cystic fibrosis transmembrane conductance regulator, and sphingosine-1-phosphate signaling.

Examining the relationship between neighbourhood deprivation and mental health service use of immigrants in Ontario, Canada: a cross-sectional study.

Objective: While newcomers are often disproportionately concentrated in disadvantaged areas, little attention is given to the effects of immigrants' postimmigration context on their mental health and care use. Intersectionality theory suggests that understanding the full impact of disadvantage requires considering the effects of interacting factors. This study assessed the inter-relationship between recent immigration status, living in deprived areas and service use for non-psychotic mental health disorders.

Nonaneurysmal perimesencephalic subarachnoid hemorrhage: diagnosis, pathophysiology, clinical characteristics, and long-term outcome.

Patients with nonaneurysmal perimesencephalic subarachnoid hemorrhage (NAPSAH) have no discernible source for the bleeding and generally are considered to have a benign condition. Correctly diagnosing these patients is essential because a missed aneurysm can have catastrophic consequences. Those presenting with NAPSAH have a low risk of complications and better outcome than patients presenting with aneurysmal subarachnoid hemorrhage; however, a limited body of literature suggests that not all of these patients are able to return to their premorbid functional status.

Implementation trial of the basic life support termination of resuscitation rule: reducing the transport of futile out-of-hospital cardiac arrests.

Background: The basic life support (BLS) termination of resuscitation (TOR) rule recommends transport and continued resuscitation when cardiac arrest is witnessed by EMT-Ds, or there is a return of spontaneous circulation, or a shock is given, and prior studies have suggested the transport rate should fall to 37%.

Methods And Results: This real-time prospective multi-center implementation trial evaluated the BLS TOR rule for compliance, transport rate and provider and physician comfort. Both provider and physician noted their decision-making rationale and ranked their comfort on a 5-point Likert scale.

Impact of socioeconomic status on initial clinical presentation to a memory disorders clinic.

Background: Dementia affects 15% of Canadians 65 and older, and the prevalence is expected to double over the next two decades. Low socioeconomic status (SES) can increase the risk of Alzheimer's disease (AD) and the precursor mild cognitive impairment (MCI), but it is unknown what the relationship of SES is on initial clinical presentation to a memory disorders clinic.

Methods: Data from 127 AD and 135 MCI patients who presented to our Memory Disorders Clinic from 2004 to 2013 were analyzed retrospectively.

Pedicled no-touch saphenous vein graft harvest limits vascular smooth muscle cell activation: the PATENT saphenous vein graft study.

Objective: Neointimal hyperplasia secondary to vascular smooth muscle cell (VSMC) activation limits the long-term patency of saphenous vein grafts (SVGs). We compared markers of vascular injury and VSMC activation in SVGs harvested using the pedicled 'no-touch' (NT) vs the conventional (CON) technique.

Methods: Patients undergoing coronary artery bypass surgery were enrolled in the PATENT SVG trial (clinicaltrials.

Perioperative cardiovascular system failure in South Asians undergoing cardiopulmonary bypass is associated with prolonged inflammation and increased Toll-like receptor signaling in inflammatory monocytes.

Background: South Asian ethnicity is an independent risk factor for mortality after coronary artery bypass. We tested the hypothesis that this risk results from a greater inflammatory response to cardiopulmonary bypass (CPB).

Methods: This was a single-site prospective cohort study.

A comprehensive assessment of health care utilization among homeless adults under a system of universal health insurance.

Objectives: We comprehensively assessed health care utilization in a population-based sample of homeless adults and matched controls under a universal health insurance system.

Methods: We assessed health care utilization by 1165 homeless single men and women and adults in families and their age- and gender-matched low-income controls in Toronto, Ontario, from 2005 to 2009, using repeated-measures general linear models to calculate risk ratios and 95% confidence intervals (CIs).

Results: Homeless participants had mean rates of 9.