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Alhummiany B, Sharma K, Buckley DL, Soe KK, Sourbron SP. Physiological confounders of renal blood flow measurement. MAGMA (NEW YORK, N.Y.) 2024; 37:565-582. [PMID: 37971557 PMCID: PMC11417086 DOI: 10.1007/s10334-023-01126-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Revised: 09/26/2023] [Accepted: 10/12/2023] [Indexed: 11/19/2023]
Abstract
OBJECTIVES Renal blood flow (RBF) is controlled by a number of physiological factors that can contribute to the variability of its measurement. The purpose of this review is to assess the changes in RBF in response to a wide range of physiological confounders and derive practical recommendations on patient preparation and interpretation of RBF measurements with MRI. METHODS A comprehensive search was conducted to include articles reporting on physiological variations of renal perfusion, blood and/or plasma flow in healthy humans. RESULTS A total of 24 potential confounders were identified from the literature search and categorized into non-modifiable and modifiable factors. The non-modifiable factors include variables related to the demographics of a population (e.g. age, sex, and race) which cannot be manipulated but should be considered when interpreting RBF values between subjects. The modifiable factors include different activities (e.g. food/fluid intake, exercise training and medication use) that can be standardized in the study design. For each of the modifiable factors, evidence-based recommendations are provided to control for them in an RBF-measurement. CONCLUSION Future studies aiming to measure RBF are encouraged to follow a rigorous study design, that takes into account these recommendations for controlling the factors that can influence RBF results.
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Affiliation(s)
- Bashair Alhummiany
- Department of Biomedical Imaging Sciences, University of Leeds, Leeds, LS2 9NL, UK.
| | - Kanishka Sharma
- Department of Imaging, Infection, Immunity and Cardiovascular Disease, The University of Sheffield, Sheffield, UK
| | - David L Buckley
- Department of Biomedical Imaging Sciences, University of Leeds, Leeds, LS2 9NL, UK
| | - Kywe Kywe Soe
- Department of Imaging, Infection, Immunity and Cardiovascular Disease, The University of Sheffield, Sheffield, UK
| | - Steven P Sourbron
- Department of Imaging, Infection, Immunity and Cardiovascular Disease, The University of Sheffield, Sheffield, UK.
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2
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Simpson LL, Stembridge M, Siebenmann C, Moore JP, Lawley JS. Mechanisms underpinning sympathoexcitation in hypoxia. J Physiol 2024. [PMID: 38533641 DOI: 10.1113/jp284579] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Accepted: 02/28/2024] [Indexed: 03/28/2024] Open
Abstract
Sympathoexcitation is a hallmark of hypoxic exposure, occurring acutely, as well as persisting in acclimatised lowland populations and with generational exposure in highland native populations of the Andean and Tibetan plateaus. The mechanisms mediating altitude sympathoexcitation are multifactorial, involving alterations in both peripheral autonomic reflexes and central neural pathways, and are dependent on the duration of exposure. Initially, hypoxia-induced sympathoexcitation appears to be an adaptive response, primarily mediated by regulatory reflex mechanisms concerned with preserving systemic and cerebral tissue O2 delivery and maintaining arterial blood pressure. However, as exposure continues, sympathoexcitation is further augmented above that observed with acute exposure, despite acclimatisation processes that restore arterial oxygen content (C a O 2 ${C_{{\mathrm{a}}{{\mathrm{O}}_{\mathrm{2}}}}}$ ). Under these conditions, sympathoexcitation may become maladaptive, giving rise to reduced vascular reactivity and mildly elevated blood pressure. Importantly, current evidence indicates the peripheral chemoreflex does not play a significant role in the augmentation of sympathoexcitation during altitude acclimatisation, although methodological limitations may underestimate its true contribution. Instead, processes that provide no obvious survival benefit in hypoxia appear to contribute, including elevated pulmonary arterial pressure. Nocturnal periodic breathing is also a potential mechanism contributing to altitude sympathoexcitation, although experimental studies are required. Despite recent advancements within the field, several areas remain unexplored, including the mechanisms responsible for the apparent normalisation of muscle sympathetic nerve activity during intermediate hypoxic exposures, the mechanisms accounting for persistent sympathoexcitation following descent from altitude and consideration of whether there are sex-based differences in sympathetic regulation at altitude.
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Affiliation(s)
- Lydia L Simpson
- Department of Sport Science, Performance Physiology and Prevention, Universität Innsbruck, Innsbruck, Austria
| | - Mike Stembridge
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, UK
| | | | - Jonathan P Moore
- School of Psychology and Sport Science, Institute of Applied Human Physiology, Bangor University, Bangor, UK
| | - Justin S Lawley
- Department of Sport Science, Performance Physiology and Prevention, Universität Innsbruck, Innsbruck, Austria
- Institute of Mountain Emergency Medicine, EURAC Research, Bolzano, Italy
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3
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Richalet JP, Hermand E, Lhuissier FJ. Cardiovascular physiology and pathophysiology at high altitude. Nat Rev Cardiol 2024; 21:75-88. [PMID: 37783743 DOI: 10.1038/s41569-023-00924-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 08/16/2023] [Indexed: 10/04/2023]
Abstract
Oxygen is vital for cellular metabolism; therefore, the hypoxic conditions encountered at high altitude affect all physiological functions. Acute hypoxia activates the adrenergic system and induces tachycardia, whereas hypoxic pulmonary vasoconstriction increases pulmonary artery pressure. After a few days of exposure to low oxygen concentrations, the autonomic nervous system adapts and tachycardia decreases, thereby protecting the myocardium against high energy consumption. Permanent exposure to high altitude induces erythropoiesis, which if excessive can be deleterious and lead to chronic mountain sickness, often associated with pulmonary hypertension and heart failure. Genetic factors might account for the variable prevalence of chronic mountain sickness, depending on the population and geographical region. Cardiovascular adaptations to hypoxia provide a remarkable model of the regulation of oxygen availability at the cellular and systemic levels. Rapid exposure to high altitude can have adverse effects in patients with cardiovascular diseases. However, intermittent, moderate hypoxia might be useful in the management of some cardiovascular disorders, such as coronary heart disease and heart failure. The aim of this Review is to help physicians to understand the cardiovascular responses to hypoxia and to outline some recommendations that they can give to patients with cardiovascular disease who wish to travel to high-altitude destinations.
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Affiliation(s)
- Jean-Paul Richalet
- Hypoxie et Poumon, Université Sorbonne Paris Nord, INSERM U1272, Paris, France.
| | - Eric Hermand
- Unité de Recherche Pluridisciplinaire Sport Santé Société, ULR 7369-URePSSS, Université Littoral Côte d'Opale, Université Artois, Université Lille, CHU Lille, Dunkirk, France
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Forrer A, Gaisl T, Sevik A, Meyer M, Senteler L, Lichtblau M, Bloch KE, Ulrich S, Furian M. Partial Pressure of Arterial Oxygen in Healthy Adults at High Altitudes: A Systematic Review and Meta-Analysis. JAMA Netw Open 2023; 6:e2318036. [PMID: 37326993 PMCID: PMC10276310 DOI: 10.1001/jamanetworkopen.2023.18036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Accepted: 04/27/2023] [Indexed: 06/17/2023] Open
Abstract
Importance With increasing altitude, the partial pressure of inspired oxygen decreases and, consequently, the Pao2 decreases. Even though this phenomenon is well known, the extent of the reduction as a function of altitude remains unknown. Objective To calculate an effect size estimate for the decrease in Pao2 with each kilometer of vertical gain among healthy unacclimatized adults and to identify factors associated with Pao2 at high altitude (HA). Data Sources A systematic search of PubMed and Embase was performed from database inception to April 11, 2023. Search terms included arterial blood gases and altitude. Study Selection A total of 53 peer-reviewed prospective studies in healthy adults providing results of arterial blood gas analysis at low altitude (<1500 m) and within the first 3 days at the target altitude (≥1500 m) were analyzed. Data Extraction and Synthesis Primary and secondary outcomes as well as study characteristics were extracted from the included studies, and individual participant data (IPD) were requested. Estimates were pooled using a random-effects DerSimonian-Laird model for the meta-analysis. Main Outcomes and Measures Mean effect size estimates and 95% CIs for reduction in Pao2 at HA and factors associated with Pao2 at HA in healthy adults. Results All of the 53 studies involving 777 adults (mean [SD] age, 36.2 [10.5] years; 510 men [65.6%]) reporting 115 group ascents to altitudes between 1524 m and 8730 m were included in the aggregated data analysis; 13 of those studies involving 305 individuals (mean [SD] age, 39.8 [13.6] years; 185 men [60.7%]) reporting 29 ascents were included in the IPD analysis. The estimated effect size of Pao2 was -1.60 kPa (95% CI, -1.73 to -1.47 kPa) for each 1000 m of altitude gain (τ2 = 0.14; I2 = 86%). The Pao2 estimation model based on IPD data revealed that target altitude (-1.53 kPa per 1000 m; 95% CI, -1.63 to -1.42 kPa per 1000 m), age (-0.01 kPa per year; 95% CI, -0.02 to -0.003 kPa per year), and time spent at an altitude of 1500 m or higher (0.16 kPa per day; 95% CI, 0.11-0.21 kPa per day) were significantly associated with Pao2. Conclusions and Relevance In this systematic review and meta-analysis, the mean decrease in Pao2 was 1.60 kPa per 1000 m of vertical ascent. This effect size estimate may improve the understanding of physiological mechanisms, assist in the clinical interpretation of acute altitude illness in healthy individuals, and serve as a reference for physicians counseling patients with cardiorespiratory disease who are traveling to HA regions.
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Affiliation(s)
- Aglaia Forrer
- Department of Respiratory Medicine, University Hospital Zurich, Zurich, Switzerland
| | - Thomas Gaisl
- Department of Respiratory Medicine, University Hospital Zurich, Zurich, Switzerland
- Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, Massachusetts
| | - Ahmet Sevik
- Department of Respiratory Medicine, University Hospital Zurich, Zurich, Switzerland
| | - Michelle Meyer
- Department of Respiratory Medicine, University Hospital Zurich, Zurich, Switzerland
| | - Luzi Senteler
- Department of Respiratory Medicine, University Hospital Zurich, Zurich, Switzerland
| | - Mona Lichtblau
- Department of Respiratory Medicine, University Hospital Zurich, Zurich, Switzerland
| | - Konrad Ernst Bloch
- Department of Respiratory Medicine, University Hospital Zurich, Zurich, Switzerland
- Swiss-Kyrgyz High-Altitude Medicine and Research Initiative, Zurich, Switzerland
| | - Silvia Ulrich
- Department of Respiratory Medicine, University Hospital Zurich, Zurich, Switzerland
- Swiss-Kyrgyz High-Altitude Medicine and Research Initiative, Zurich, Switzerland
| | - Michael Furian
- Department of Respiratory Medicine, University Hospital Zurich, Zurich, Switzerland
- Swiss-Kyrgyz High-Altitude Medicine and Research Initiative, Zurich, Switzerland
- Research Department, Swiss University for Traditional Chinese Medicine, Bad Zurzach, Switzerland
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Rathi V, Tiwari I, Kulshreshtha R, S. K. Sagi S. Hypobaric hypoxia induced renal injury in rats: Prophylactic amelioration by quercetin supplementation. PLoS One 2023; 18:e0279304. [PMID: 36827356 PMCID: PMC9955615 DOI: 10.1371/journal.pone.0279304] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Accepted: 12/05/2022] [Indexed: 02/26/2023] Open
Abstract
The present study aims at assessing the effect of hypobaric hypoxia induced renal damage and associated renal functions in male SD rats. Further, this study was extended to explore the protective efficacy of quercetin in ameliorating the functional impairment in kidneys of rats under hypobaric hypoxia. Rats were exposed to 7620m (25000 ft.) at 25°C ±2 in a simulated hypobaric hypoxia chamber for different time durations (0h,1h, 3h, 6h, 12h, 24h and 48h) in order to optimize the time at which maximum renal damage would occur. The rats were exposed to hypoxia for 12h duration was considered as the optimum time, due to significant increase in oxidative stress (ROS, MDA) and renal metabolites (creatinine, BUN and uric acid) with remarkable reduction (p<0.001) in antioxidants (GSH) in plasma, as compared to other tested durations. Moreover, these findings were in support with the histopathology analysis of renal tissues. For optimum quercetin dose selection, the rats were administered with different doses of quercetin (25mg, 50mg, 100mg and 200mg/Kg BW) for 12h at 7620 m, 25°C ±2, 1h prior to hypoxia exposure. Quercetin 50mg/kg BW was considered as the optimum dose at which significant (p<0.001) reduction in oxidative stress levels followed by reduction in creatinine and BUN levels were obtained in plasma of the rats compared to hypoxia control rats. Quercetin prophylaxis (50mg/kg BW) stabilized the HIF-1α protein expression followed by reduced VEGF protein expression along with reduced levels of LDH (p<0.001) in the kidneys of rats compared to hypoxia control. Histopathological observations further substantiated these findings in reducing the renal tissue injury. The study findings revealed that, quercetin prophylaxis abrogates the possibility of hypobaric hypoxia induced renal injury by reducing the oxidative stress in rats.
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Affiliation(s)
- Vaishnavi Rathi
- Defence Institute of Physiology and Allied Sciences, DRDO, Delhi, India
| | - Isha Tiwari
- Defence Institute of Physiology and Allied Sciences, DRDO, Delhi, India
| | - Ritu Kulshreshtha
- Vallabhbhai Patel Chest Institute, University of Delhi, New Delhi, India
| | - Sarada S. K. Sagi
- Defence Institute of Physiology and Allied Sciences, DRDO, Delhi, India
- * E-mail:
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Steele AR, Ainslie PN, Stone R, Tymko K, Tymko C, Howe CA, MacLeod D, Anholm JD, Gasho C, Tymko MM. Global REACH 2018: Characterizing Acid-Base Balance Over 21 Days at 4,300 m in Lowlanders. High Alt Med Biol 2022; 23:185-191. [PMID: 35231184 DOI: 10.1089/ham.2021.0115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Steele, Andrew R., Philip N. Ainslie, Rachel Stone, Kaitlyn Tymko, Courtney Tymko, Connor A. Howe, David MacLeod, James D. Anholm, Christopher Gasho, and Michael M. Tymko. Global REACH 2018: characterizing acid-base balance over 21 days at 4,300 m in lowlanders. High Alt Med Biol. 23:185-191, 2022. Introduction: High altitude exposure results in hyperventilatory-induced respiratory alkalosis, followed by metabolic compensation to return arterial blood pH (pHa) toward sea level values. However, previous work has limited sample sizes, short-term exposure, and pharmacological confounders (e.g., acetazolamide). The purpose of this investigation was to characterize acid-base balance after rapid ascent to high altitude (i.e., 4,300 m) in lowlanders. We hypothesized that despite rapid bicarbonate ([HCO3-]) excretion during early acclimatization, partial respiratory alkalosis would still be apparent as reflected in elevations in pHa compared with sea level after 21 days of acclimatization to 4,300 m. Methods: In 16 (3 female) healthy volunteers not taking any medications, radial artery blood samples were collected and analyzed at sea level (150 m; Lima, Peru), and on days 1, 3, 7, 14, and 21 after rapid automobile (∼8 hours) ascent to high altitude (4,300 m; Cerro de Pasco, Peru). Results and Discussion: Although reductions in [HCO3-] occurred by day 3 (p < 0.01), they remained stable thereafter and were insufficient to fully normalize pHa back to sea level values over the subsequent 21 days (p < 0.01). These data indicate that only partial compensation for respiratory alkalosis persists throughout 21 days at 4,300 m.
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Affiliation(s)
- Andrew R Steele
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia-Okanagan, Kelowna, British Columbia, Canada
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia-Okanagan, Kelowna, British Columbia, Canada
| | - Rachel Stone
- Department of Kinesiology, University of Windsor, Windsor, Ontario, Canada
| | - Kaitlyn Tymko
- Department of Kinesiology and Recreation Management, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Courtney Tymko
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia-Okanagan, Kelowna, British Columbia, Canada
| | - Connor A Howe
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia-Okanagan, Kelowna, British Columbia, Canada
| | - David MacLeod
- Human Pharmacology and Physiology Lab, Duke University Medical Center, Durham, North Carolina, USA
| | - James D Anholm
- Division of Pulmonary and Critical Care, Department of Medicine, School of Medicine, Loma Linda University, Loma Linda, California, USA
| | - Christopher Gasho
- Division of Pulmonary and Critical Care, Department of Medicine, School of Medicine, Loma Linda University, Loma Linda, California, USA
| | - Michael M Tymko
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia-Okanagan, Kelowna, British Columbia, Canada.,Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Edmonton, Alberta, Canada
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Bird JD, Leacy JK, Foster GE, Rickards CA, Wilson RJA, O'Halloran KD, Jendzjowsky NG, Pentz BA, Byman BRM, Thrall SF, Skalk AL, Hewitt SA, Steinback CD, Burns D, Ondrus P, Day TA. Time course and magnitude of ventilatory and renal acid-base acclimatization following rapid ascent to and residence at 3,800 m over nine days. J Appl Physiol (1985) 2021; 130:1705-1715. [PMID: 33703943 PMCID: PMC11025293 DOI: 10.1152/japplphysiol.00973.2020] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Accepted: 03/05/2021] [Indexed: 11/22/2022] Open
Abstract
Rapid ascent to high altitude imposes an acute hypoxic and acid-base challenge, with ventilatory and renal acclimatization countering these perturbations. Specifically, ventilatory acclimatization improves oxygenation, but with concomitant hypocapnia and respiratory alkalosis. A compensatory, renally mediated relative metabolic acidosis follows via bicarbonate elimination, normalizing arterial pH(a). The time course and magnitude of these integrated acclimatization processes are highly variable between individuals. Using a previously developed metric of renal reactivity (RR), indexing the change in arterial bicarbonate concentration (Δ[HCO3-]a; renal response) over the change in arterial pressure of CO2 (Δ[Formula: see text]; renal stimulus), we aimed to characterize changes in RR magnitude following rapid ascent and residence at altitude. Resident lowlanders (n = 16) were tested at 1,045 m (day [D]0) prior to ascent, on D2 within 24 h of arrival, and D9 during residence at 3,800 m. Radial artery blood draws were obtained to measure acid-base variables: [Formula: see text], [HCO3-]a, and pHa. Compared with D0, [Formula: see text] and [HCO3-]a were lower on D2 (P < 0.01) and D9 (P < 0.01), whereas significant changes in pHa (P = 0.072) and RR (P = 0.056) were not detected. As pHa appeared fully compensated on D2 and RR did not increase significantly from D2 to D9, these data demonstrate renal acid-base compensation within 24 h at moderate steady-state altitude. Moreover, RR was strongly and inversely correlated with ΔpHa on D2 and D9 (r≤ -0.95; P < 0.0001), suggesting that a high-gain renal response better protects pHa. Our study highlights the differential time course, magnitude, and variability of integrated ventilatory and renal acid-base acclimatization following rapid ascent and residence at high altitude.NEW & NOTEWORTHY We assessed the time course, magnitude, and variability of integrated ventilatory and renal acid-base acclimatization with rapid ascent and residence at 3,800 m. Despite reductions in [Formula: see text] upon ascent, pHa was normalized within 24 h of arrival at 3,800 m through renal compensation (i.e., bicarbonate elimination). Renal reactivity (RR) was unchanged between days 2 and 9, suggesting a lack of plasticity at moderate steady-state altitude. RR was strongly correlated with ΔpHa, suggesting that a high-gain renal response better protects pHa.
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Affiliation(s)
- Jordan D Bird
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada
| | - Jack K Leacy
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada
| | - Glen E Foster
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada
| | - Caroline A Rickards
- Cerebral and Cardiovascular Physiology Laboratory, Department of Physiology and Anatomy, University of North Texas Health Sciences Centre, Fort Worth, Texas
| | - Richard J A Wilson
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute and Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Ken D O'Halloran
- Department of Physiology, School of Medicine, College of Medicine and Health, University College Cork, Cork, Ireland
| | - Nicholas G Jendzjowsky
- Division of Respiratory and Critical Care Physiology and Medicine, The Lundquist Institute for Biomedical Innovation, Harbor-UCLA Medical Center, Torrance, California
| | - Brandon A Pentz
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada
| | - Britta R M Byman
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada
| | - Scott F Thrall
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada
| | - Alexandra L Skalk
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada
| | - Sarah A Hewitt
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada
| | - Craig D Steinback
- Neurovascular Health Lab, Faculty of Kinesiology, Sport, & Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - David Burns
- Department of Physiology, School of Medicine, College of Medicine and Health, University College Cork, Cork, Ireland
| | - Peter Ondrus
- Department of Family Medicine, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Trevor A Day
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada
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