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Kowalewska PM, Milkovich SL, Goldman D, Sandow SL, Ellis CG, Welsh DG. Capillary oxygen regulates demand-supply coupling by triggering connexin40-mediated conduction: Rethinking the metabolic hypothesis. Proc Natl Acad Sci U S A 2024; 121:e2303119121. [PMID: 38349880 PMCID: PMC10895355 DOI: 10.1073/pnas.2303119121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2023] [Accepted: 12/21/2023] [Indexed: 02/15/2024] Open
Abstract
Coupling red blood cell (RBC) supply to O2 demand is an intricate process requiring O2 sensing, generation of a stimulus, and signal transduction that alters upstream arteriolar tone. Although actively debated, this process has been theorized to be induced by hypoxia and to involve activation of endothelial inwardly rectifying K+ channels (KIR) 2.1 by elevated extracellular K+ to trigger conducted hyperpolarization via connexin40 (Cx40) gap junctions to upstream resistors. This concept was tested in resting healthy skeletal muscle of Cx40-/- and endothelial KIR2.1-/- mice using state-of-the-art live animal imaging where the local tissue O2 environment was manipulated using a custom gas chamber. Second-by-second capillary RBC flow responses were recorded as O2 was altered. A stepwise drop in PO2 at the muscle surface increased RBC supply in capillaries of control animals while elevated O2 elicited the opposite response; capillaries were confirmed to express Cx40. The RBC flow responses were rapid and tightly coupled to O2; computer simulations did not support hypoxia as a driving factor. In contrast, RBC flow responses were significantly diminished in Cx40-/- mice. Endothelial KIR2.1-/- mice, on the other hand, reacted normally to O2 changes, even when the O2 challenge was targeted to a smaller area of tissue with fewer capillaries. Conclusively, microvascular O2 responses depend on coordinated electrical signaling via Cx40 gap junctions, and endothelial KIR2.1 channels do not initiate the event. These findings reconceptualize the paradigm of blood flow regulation in skeletal muscle and how O2 triggers this process in capillaries independent of extracellular K+.
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Affiliation(s)
- Paulina M. Kowalewska
- Robarts Research Institute, University of Western Ontario, London, ONN6A 5B7, Canada
- Department of Physiology and Pharmacology, University of Western Ontario, London, ONN6A 5B7, Canada
| | | | - Daniel Goldman
- Department of Medical Biophysics, University of Western Ontario, London, ONN6A 5B7, Canada
| | - Shaun L. Sandow
- School of Health, University of the Sunshine Coast, Maroochydore, QLD4556, Australia
- School of Clinical Medicine, University of Queensland, St. Lucia, QLD4072, Australia
| | - Christopher G. Ellis
- Robarts Research Institute, University of Western Ontario, London, ONN6A 5B7, Canada
- Department of Medical Biophysics, University of Western Ontario, London, ONN6A 5B7, Canada
| | - Donald G. Welsh
- Robarts Research Institute, University of Western Ontario, London, ONN6A 5B7, Canada
- Department of Physiology and Pharmacology, University of Western Ontario, London, ONN6A 5B7, Canada
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2
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Chen X, Yuan S, Mi L, Long Y, He H. Pannexin1: insight into inflammatory conditions and its potential involvement in multiple organ dysfunction syndrome. Front Immunol 2023; 14:1217366. [PMID: 37711629 PMCID: PMC10498923 DOI: 10.3389/fimmu.2023.1217366] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Accepted: 08/10/2023] [Indexed: 09/16/2023] Open
Abstract
Sepsis represents a global health concern, and patients with severe sepsis are at risk of experiencing MODS (multiple organ dysfunction syndrome), which is associated with elevated mortality rates and a poorer prognosis. The development of sepsis involves hyperactive inflammation, immune disorder, and disrupted microcirculation. It is crucial to identify targets within these processes to develop therapeutic interventions. One such potential target is Panx1 (pannexin-1), a widely expressed transmembrane protein that facilitates the passage of molecules smaller than 1 KDa, such as ATP. Accumulating evidence has implicated the involvement of Panx1 in sepsis-associated MODS. It attracts immune cells via the purinergic signaling pathway, mediates immune responses via the Panx1-IL-33 axis, promotes immune cell apoptosis, regulates blood flow by modulating VSMCs' and vascular endothelial cells' tension, and disrupts microcirculation by elevating endothelial permeability and promoting microthrombosis. At the level of organs, Panx1 contributes to inflammatory injury in multiple organs. Panx1 primarily exacerbates injury and hinders recovery, making it a potential target for sepsis-induced MODS. While no drugs have been developed explicitly against Panx1, some compounds that inhibit Panx1 hemichannels have been used extensively in experiments. However, given that Panx1's role may vary during different phases of sepsis, more investigations are required before interventions against Panx1 can be applied in clinical. Overall, Panx1 may be a promising target for sepsis-induced MODS. Nevertheless, further research is needed to understand its complex role in different stages of sepsis fully and to develop suitable pharmaceutical interventions for clinical use.
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Affiliation(s)
| | | | | | - Yun Long
- Department of Critical Care Medicine, State Key Laboratory of Complex Severe and Rare Diseases, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, China
| | - Huaiwu He
- Department of Critical Care Medicine, State Key Laboratory of Complex Severe and Rare Diseases, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, China
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Gou Z, Zhang H, Misbah C. Heterogeneous ATP patterns in microvascular networks. J R Soc Interface 2023; 20:20230186. [PMID: 37464803 PMCID: PMC10354495 DOI: 10.1098/rsif.2023.0186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Accepted: 06/21/2023] [Indexed: 07/20/2023] Open
Abstract
ATP is not only an energy carrier but also serves as an important signalling molecule in many physiological processes. Abnormal ATP level in blood vessel is known to be related to several pathologies, such as inflammation, hypoxia and atherosclerosis. Using advanced numerical methods, we analysed ATP released by red blood cells (RBCs) and its degradation by endothelial cells (ECs) in a cat mesentery-inspired vascular network, accounting for RBC mutual interaction and interactions with vascular walls. Our analysis revealed a heterogeneous ATP distribution in the network, with higher concentrations in the cell-free layer, concentration peaks around bifurcations and heterogeneity among vessels of the same level. These patterns arise from the spatio-temporal organization of RBCs induced by the network geometry. It is further shown that an alteration of hematocrit and flow strength significantly affects ATP level as well as heterogeneity in the network. These findings constitute a first building block to elucidate the intricate nature of ATP patterns in vascular networks and the far reaching consequences for other biochemical signalling, such as calcium, by ECs.
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Affiliation(s)
- Zhe Gou
- CNRS, LIPhy, Université Grenoble Alpes, 38000 Grenoble, France
| | - Hengdi Zhang
- CNRS, LIPhy, Université Grenoble Alpes, 38000 Grenoble, France
- Shenzhen Sibionics Co. Ltd, Shenzhen, People’s Republic of China
| | - Chaouqi Misbah
- CNRS, LIPhy, Université Grenoble Alpes, 38000 Grenoble, France
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Mendelson AA, Erickson D, Villar R. The role of the microcirculation and integrative cardiovascular physiology in the pathogenesis of ICU-acquired weakness. Front Physiol 2023; 14:1170429. [PMID: 37234410 PMCID: PMC10206327 DOI: 10.3389/fphys.2023.1170429] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Accepted: 04/28/2023] [Indexed: 05/28/2023] Open
Abstract
Skeletal muscle dysfunction after critical illness, defined as ICU-acquired weakness (ICU-AW), is a complex and multifactorial syndrome that contributes significantly to long-term morbidity and reduced quality of life for ICU survivors and caregivers. Historically, research in this field has focused on pathological changes within the muscle itself, without much consideration for their in vivo physiological environment. Skeletal muscle has the widest range of oxygen metabolism of any organ, and regulation of oxygen supply with tissue demand is a fundamental requirement for locomotion and muscle function. During exercise, this process is exquisitely controlled and coordinated by the cardiovascular, respiratory, and autonomic systems, and also within the skeletal muscle microcirculation and mitochondria as the terminal site of oxygen exchange and utilization. This review highlights the potential contribution of the microcirculation and integrative cardiovascular physiology to the pathogenesis of ICU-AW. An overview of skeletal muscle microvascular structure and function is provided, as well as our understanding of microvascular dysfunction during the acute phase of critical illness; whether microvascular dysfunction persists after ICU discharge is currently not known. Molecular mechanisms that regulate crosstalk between endothelial cells and myocytes are discussed, including the role of the microcirculation in skeletal muscle atrophy, oxidative stress, and satellite cell biology. The concept of integrated control of oxygen delivery and utilization during exercise is introduced, with evidence of physiological dysfunction throughout the oxygen delivery pathway - from mouth to mitochondria - causing reduced exercise capacity in patients with chronic disease (e.g., heart failure, COPD). We suggest that objective and perceived weakness after critical illness represents a physiological failure of oxygen supply-demand matching - both globally throughout the body and locally within skeletal muscle. Lastly, we highlight the value of standardized cardiopulmonary exercise testing protocols for evaluating fitness in ICU survivors, and the application of near-infrared spectroscopy for directly measuring skeletal muscle oxygenation, representing potential advancements in ICU-AW research and rehabilitation.
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Affiliation(s)
- Asher A. Mendelson
- Section of Critical Care Medicine, Department of Medicine, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, MB, Canada
| | - Dustin Erickson
- Section of Critical Care Medicine, Department of Medicine, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, MB, Canada
| | - Rodrigo Villar
- Faculty of Kinesiology and Recreation Management, University of Manitoba, Winnipeg, MB, Canada
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Dufner TJ, Moon JM, Fukuda DH, Wells AJ. The Effects of Two Weeks of Oral PeakATP ® Supplementation on Performance during a Three-Minute All out Test. J Funct Morphol Kinesiol 2023; 8:jfmk8020042. [PMID: 37092374 PMCID: PMC10123745 DOI: 10.3390/jfmk8020042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Revised: 03/29/2023] [Accepted: 03/30/2023] [Indexed: 04/25/2023] Open
Abstract
Exogenous ATP has been shown to increase total weight lifted during resistance training interventions and attenuate fatigue during repeated Wingate assessments. However, the influence of exogenous ATP on single bout maximal effort performance has yet to be examined. The purpose of this study was to investigate the effects of PeakATP® supplementation on performance during a 3-min all-out test (3MT). Twenty adults (22.3 ± 4.4 years, 169.9 ± 9.5 cm, 78.7 ± 14.6 kg) completed two identical 3MT protocols in a double-blind, counter-balanced, crossover design. Participants were randomized to either PeakATP® (400 mg·day-1) or placebo (PLA) treatments and consumed their assigned supplement for 14 days and ingested an acute dose 30 min before each 3MT. A 14-day wash-out period was completed between each supplementation period and subsequent 3MT. Peak power, time to peak power, work above end power, end power, and fatigue index were assessed during each 3MT. Dependent t-tests and Hedge's g effect sizes were used to assess differences between treatments. No significant differences were observed between treatments for 3MT performance (p > 0.05). These findings indicate that 3MT performance was not significantly impacted by PeakATP® supplementation. This may be due in part to the continuous nature of the 3MT as disodium ATP has been shown to be beneficial for repeated bout activities.
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Affiliation(s)
- Trevor J Dufner
- School of Kinesiology and Rehabilitation Sciences, University of Central Florida, 12494 University Blvd, Orlando, FL 32816, USA
| | - Jessica M Moon
- School of Kinesiology and Rehabilitation Sciences, University of Central Florida, 12494 University Blvd, Orlando, FL 32816, USA
| | - David H Fukuda
- School of Kinesiology and Rehabilitation Sciences, University of Central Florida, 12494 University Blvd, Orlando, FL 32816, USA
| | - Adam J Wells
- School of Kinesiology and Rehabilitation Sciences, University of Central Florida, 12494 University Blvd, Orlando, FL 32816, USA
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Russell McEvoy GM, Wells BN, Kiley ME, Kaur KK, Fraser GM. Dynamics of capillary blood flow responses to acute local changes in oxygen and carbon dioxide concentrations. Front Physiol 2022; 13:1052449. [PMID: 36561216 PMCID: PMC9764012 DOI: 10.3389/fphys.2022.1052449] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Accepted: 11/15/2022] [Indexed: 12/24/2022] Open
Abstract
Objectives: We aimed to quantify the magnitude and time transients of capillary blood flow responses to acute changes in local oxygen concentration ([O2]), and carbon dioxide concentration ([CO2]) in skeletal muscle. Additionally, we sought to quantify the combined response to both low [O2] and high [CO2] to mimic muscle microenvironment changes at the onset of exercise. Methods: 13 Sprague Dawley rats were anaesthetized, mechanically ventilated, and instrumented with indwelling catheters for systemic monitoring. The extensor digitorum longus muscle was blunt dissected, and reflected over a microfluidic gas exchange chamber in the stage of an inverted microscope. Four O2 challenges, four CO2 challenges, and a combined low O2 (7-2%) and high CO2 (5-10%) challenges were delivered to the surface with simultaneous visualization of capillary blood flow responses. Recordings were made for each challenge over a 1-min baseline period followed by a 2-min step change. The combined challenge employed a 1-min [O2] challenge followed by a 2-min change in [CO2]. Mean data for each sequence were fit using least-squared non-linear exponential models to determine the dynamics of each response. Results: 7-2% [O2] challenges decreased capillary RBC saturation within 2 s following the step change (46.53 ± 19.56% vs. 48.51 ± 19.02%, p < 0.0001, τ = 1.44 s), increased RBC velocity within 3 s (228.53 ± 190.39 μm/s vs. 235.74 ± 193.52 μm/s, p < 0.0003, τ = 35.54 s) with a 52% peak increase by the end of the challenge, hematocrit and supply rate show similar dynamics. 5-10% [CO2] challenges increased RBC velocity within 2 s following the step change (273.40 ± 218.06 μm/s vs. 276.75 ± 215.94 μm/s, p = 0.007, τ = 79.34s), with a 58% peak increase by the end of the challenge, supply rate and hematocrit show similar dynamics. Combined [O2] and [CO2] challenges resulted in additive responses to all microvascular hemodynamic measures with a 103% peak velocity increase by the end of the collection period. Data for mean responses and exponential fitting parameters are reported for all challenges. Conclusion: Microvascular level changes in muscle [O2] and [CO2] provoked capillary hemodynamic responses with differing time transients. Simulating exercise via combined [O2] and [CO2] challenges demonstrated the independent and additive nature of local blood flow responses to these agents.
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7
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Christie JR, Kong I, Mawdsley L, Milkovich S, Doornekamp A, Baek J, Fraser GM, Ellis CG, Sové RJ. Optical method to determine in vivo capillary hematocrit, hemoglobin concentration, and 3-D network geometry in skeletal muscle. Microcirculation 2022; 29:e12751. [PMID: 35146836 DOI: 10.1111/micc.12751] [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: 07/31/2021] [Revised: 12/18/2021] [Accepted: 02/02/2022] [Indexed: 12/30/2022]
Abstract
OBJECTIVE The aim of this study was to develop a tool to visualize and quantify hemodynamic information, such as hemoglobin concentration and hematocrit, within microvascular networks recorded in vivo using intravital video microscopy. Additionally, we aimed to facilitate the 3-D reconstruction of the microvascular networks. METHODS Digital images taken from an intravital video microscopy preparation of the extensor digitorum longus muscle in rats for 25 capillary segments were used. The developed algorithm was used to delineate capillaries of interest, calculate the optical density for each pixel in the image, and reconstruct the 3-D capillary geometry using the calculated light path-lengths. Subsequently, the mean corpuscular hemoglobin concentration (MCHC), hemoglobin concentration, and hematocrit for these capillaries were calculated. We evaluated the hematocrit values determined by our methodology by comparing them to those obtained using a previously published method. RESULTS The hematocrit values from the proposed optical method were strongly correlated with those calculated using published methods r2 (25) = .92, p < .001, and demonstrated excellent agreement with a mean difference of 1.3% and a coefficient of variation (CV) of 11%. The average MCHC, hemoglobin concentration, and light path-lengths were 23.83 g/dl, 8.06 g/dl, and 3.92 µm, respectively. CONCLUSION The proposed methodology can quantify hemodynamic measurements and produce functional images for visualization of the microcirculation in vivo.
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Affiliation(s)
- Jaryd R Christie
- Department of Medical Biophysics, University of Western Ontario, London, Ontario, Canada
| | - Isaac Kong
- Division of Radiation Oncology, Department of Oncology, Juravinski Cancer Centre, McMaster University, Hamilton, Ontario, Canada
| | - Laura Mawdsley
- Department of Medical Biophysics, University of Western Ontario, London, Ontario, Canada.,Robarts Research Institute, University of Western Ontario, London, Ontario, Canada
| | - Stephanie Milkovich
- Department of Medical Biophysics, University of Western Ontario, London, Ontario, Canada.,Robarts Research Institute, University of Western Ontario, London, Ontario, Canada
| | - Ande Doornekamp
- Department of Medical Biophysics, University of Western Ontario, London, Ontario, Canada
| | - Jason Baek
- Temerty Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Graham M Fraser
- Division of BioMedical Sciences, Memorial University of Newfoundland, St. John's, NL, Canada
| | - Christopher G Ellis
- Department of Medical Biophysics, University of Western Ontario, London, Ontario, Canada.,Robarts Research Institute, University of Western Ontario, London, Ontario, Canada
| | - Richard J Sové
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland, USA
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8
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Cold Blood: Some Ways by Which Animals Cope with Low Temperatures. Blood 2022. [DOI: 10.1017/9781009205528.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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9
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Spectroscopy detects skeletal muscle microvascular dysfunction during onset of sepsis in a rat fecal peritonitis model. Sci Rep 2022; 12:6339. [PMID: 35428849 PMCID: PMC9012880 DOI: 10.1038/s41598-022-10208-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Accepted: 03/15/2022] [Indexed: 01/20/2023] Open
Abstract
Sepsis is a dysregulated host inflammatory response to infection potentially leading to life-threatening organ dysfunction. The objectives of this study were to determine whether early microvascular dysfunction (MVD) in skeletal muscle can be detected as dynamic changes in microvascular hemoglobin (MVHb) levels using spectroscopy and whether MVD precedes organ histopathology in septic peritonitis. Skeletal muscle of male Sprague-Dawley rats was prepared for intravital microscopy. After intraperitoneal injection of fecal slurry or saline, microscopy and spectroscopy recordings were taken for 6 h. Capillary red blood cell (RBC) dynamics and SO2 were quantified from digitized microscopy frames and MVHb levels were derived from spectroscopy data. Capillary RBC dynamics were significantly decreased by 4 h after peritoneal infection and preceded macrohemodynamic changes. At the same time, low-frequency oscillations in MVHb levels exhibited a significant increase in Power in parts of the muscle and resembled oscillations in RBC dynamics and SO2. After completion of microscopy, tissues were collected. Histopathological alterations were not observed in livers, kidneys, brains, or muscles 6 h after induction of peritonitis. The findings of this study show that, in our rat model of sepsis, MVD occurs before detectable organ histopathology and includes ~ 30-s oscillations in MVHb. Our work highlights MVHb oscillations as one of the indicators of MVD onset and provides a foundation for the use of non-invasive spectroscopy to continuously monitor MVD in septic patients.
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10
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Horn AG, Schulze KM, Weber RE, Barstow TJ, Musch TI, Poole DC, Behnke BJ. Post-occlusive reactive hyperemia and skeletal muscle capillary hemodynamics. Microvasc Res 2022; 140:104283. [PMID: 34822837 PMCID: PMC8830587 DOI: 10.1016/j.mvr.2021.104283] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Revised: 11/12/2021] [Accepted: 11/16/2021] [Indexed: 10/19/2022]
Abstract
Post-occlusive reactive hyperemia (PORH) is an accepted diagnostic tool for assessing peripheral macrovascular function. While conduit artery hemodynamics have been well defined, the impact of PORH on capillary hemodynamics remains unknown, despite the microvasculature being the dominant site of vascular control. Therefore, the purpose of this investigation was to determine the effects of 5 min of feed artery occlusion on capillary hemodynamics in skeletal muscle. We tested the hypothesis that, upon release of arterial occlusion, there would be: 1) an increased red blood cell flux (fRBC) and red blood cell velocity (VRBC), and 2) a decreased proportion of capillaries supporting RBC flow compared to the pre-occlusion condition. METHODS In female Sprague-Dawley rats (n = 6), the spinotrapezius muscle was exteriorized for evaluation of capillary hemodynamics pre-occlusion, 5 min of feed artery occlusion (Occ), and 5 min of reperfusion (Post-Occ). RESULTS There were no differences in mean arterial pressure (MAP) or capillary diameter (Dc) between pre-occlusion and post-occlusion (P > 0.05). During 30 s of PORH, capillary fRBC was increased (pre: 59 ± 4 vs. 30 s-post: 77 ± 2 cells/s; P < 0.05) and VRBC was not changed (pre: 300 ± 24 vs. 30 s post: 322 ± 25 μm/s; P > 0.05). Capillary hematocrit (Hctcap) was unchanged across the pre- to post-occlusion conditions (P > 0.05). Following occlusion, there was a 20-30% decrease in the number of capillaries supporting RBC flow at 30 s and 300 s-post occlusion (pre: 92 ± 2%; 30 s-post: 66 ± 3%; 300 s-post: 72 ± 6%; both P < 0.05). CONCLUSION Short-term feed artery occlusion (i.e. 5 min) resulted in a more heterogeneous capillary flow profile with the presence of capillary no-reflow, decreasing the percentage of capillaries supporting RBC flow. A complex interaction between myogenic and metabolic mechanisms at the arteriolar level may play a role in the capillary no-reflow with PORH. Measurements at the level of the conduit artery mask significant alterations in blood flow distribution in the microcirculation.
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Affiliation(s)
- Andrew G Horn
- Department of Kinesiology, Kansas State University, Manhattan, KS, United States of America.
| | - Kiana M Schulze
- Department of Kinesiology, Kansas State University, Manhattan, KS, United States of America
| | - Ramona E Weber
- Department of Kinesiology, Kansas State University, Manhattan, KS, United States of America
| | - Thomas J Barstow
- Department of Kinesiology, Kansas State University, Manhattan, KS, United States of America
| | - Timothy I Musch
- Department of Kinesiology, Kansas State University, Manhattan, KS, United States of America; Department of Anatomy and Physiology, Kansas State University, Manhattan, KS, United States of America
| | - David C Poole
- Department of Kinesiology, Kansas State University, Manhattan, KS, United States of America; Department of Anatomy and Physiology, Kansas State University, Manhattan, KS, United States of America
| | - Bradley J Behnke
- Department of Kinesiology, Kansas State University, Manhattan, KS, United States of America; Johnson Cancer Research Center, Kansas State University, Manhattan, KS, United States of America
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11
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Afas KC, Goldman D. A two-layer continuously distributed capillary O 2 transport model applied to blood flow regulation in resting skeletal muscle. J Theor Biol 2022; 539:111058. [PMID: 35181287 DOI: 10.1016/j.jtbi.2022.111058] [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: 09/20/2021] [Revised: 02/07/2022] [Accepted: 02/08/2022] [Indexed: 10/19/2022]
Abstract
The microcirculation is the site of direct oxygen transfer from blood to tissue, and also of oxygen delivery control via regulation of local blood flow. In addition, a number of diseases including type II diabetes mellitus (DMII) and sepsis are known to produce microcirculatory dysfunction in their early phases. Given the complexity of microvascular structure and physiology, and the difficulty of measuring tissue oxygenation at the micro-scale, mathematical modelling has been necessary for understanding the physiology and pathophysiology of O2 transport in the microcirculation and for interpreting in vivo experiments. To advance this area, a model of blood-tissue O2 transport in skeletal muscle was recently developed which uses continuously distributed capillaries and includes O2 diffusion, convection, and consumption. The present work extends this model to two adjacent layers of skeletal muscle with different blood flow rates and applies it to study steady-state O2 transport when flow regulation is stimulated using an O2 exchange chamber. To generate a model which may be validated through in vivo experiments, an overlying O2 permeable membrane is included. The model is solved using traditional methods including separation of variables and Fourier decomposition, and to ensure smooth profiles at the muscle-muscle and muscle-membrane interfaces matching conditions are developed. The study presents qualitative verification for the model, using visualizations of tissue PO2 distributions for varying capillary density (CD), and presents capillary velocity response values in the near layer for varying chamber PO2 under the assumption that outlet capillary O2 saturation is equalized between adjacent layers. These compensatory velocity profiles, along with effective 'no-flux' chamber PO2 values, are presented for varying CD and tissue O2 consumption values. Insights gained from the two-layer model provide guidance for interpreting and planning future in-vivo experiments, and also provide motivation for further development of the model to improve understanding of the interaction between O2 transport and blood flow regulation.
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Affiliation(s)
- Keith Christian Afas
- School of Biomedical Engineering, University of Western Ontario, London, N6G1G8, Ontario, CA
| | - Daniel Goldman
- School of Biomedical Engineering, University of Western Ontario, London, N6G1G8, Ontario, CA; Department of Medical Biophysics, University of Western Ontario, London, N6A5C1, Ontario, CA; Department of Applied Mathematics, University of Western Ontario, London, N6A5C1, Ontario, CA.
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12
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Mendelson AA, Ho E, Scott S, Vijay R, Hunter T, Milkovich S, Ellis CG, Goldman D. Capillary module hemodynamics and mechanisms of blood flow regulation in skeletal muscle capillary networks: Experimental and computational analysis. J Physiol 2022; 600:1867-1888. [DOI: 10.1113/jp282342] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2021] [Accepted: 01/19/2022] [Indexed: 11/08/2022] Open
Affiliation(s)
- Asher A Mendelson
- Department of Medicine Section of Critical Care Medicine Rady Faculty of Health Sciences University of Manitoba Winnipeg Manitoba Canada
| | - Edward Ho
- Department of Medical Biophysics Schulich School of Medicine and Dentistry Western University London Ontario Canada
| | - Shayla Scott
- Department of Medical Biophysics Schulich School of Medicine and Dentistry Western University London Ontario Canada
| | - Raashi Vijay
- Department of Medical Biophysics Schulich School of Medicine and Dentistry Western University London Ontario Canada
| | - Timothy Hunter
- Department of Medical Biophysics Schulich School of Medicine and Dentistry Western University London Ontario Canada
| | - Stephanie Milkovich
- Department of Medical Biophysics Schulich School of Medicine and Dentistry Western University London Ontario Canada
- Robarts Research Institute London Ontario Canada
| | - Christopher G Ellis
- Department of Medical Biophysics Schulich School of Medicine and Dentistry Western University London Ontario Canada
- Robarts Research Institute London Ontario Canada
| | - Daniel Goldman
- Department of Medical Biophysics Schulich School of Medicine and Dentistry Western University London Ontario Canada
- School of Biomedical Engineering Western University London Ontario Canada
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13
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Gou Z, Zhang H, Abbasi M, Misbah C. Red blood cells under flow show maximal ATP release for specific hematocrit. Biophys J 2021; 120:4819-4831. [PMID: 34547277 DOI: 10.1016/j.bpj.2021.09.025] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Revised: 05/13/2021] [Accepted: 09/14/2021] [Indexed: 11/17/2022] Open
Abstract
ATP release by red blood cells (RBCs) under shear stress (SS) plays a pivotal role in endothelial biochemical signaling cascades. The aim of this study is to investigate through numerical simulation how RBC spatiotemporal organization depends on flow and geometrical conditions to generate ATP patterns. Numerical simulations were conducted in a straight channel by considering both plasma and explicit presence of RBCs, their shape deformation and cell-cell interaction, and ATP release by RBCs. Two ATP release pathways through cell membrane are taken into account: pannexin 1 channel, sensitive to SS, and cystic fibrosis transmembrane conductance regulator, which responds to cell deformation. Several flow and hematocrit conditions are explored. The problem is solved by the lattice Boltzmann method. Application of SS to the RBC suspension triggers a nontrivial spatial RBC organization and ATP patterns. ATP localizes preferentially in the vicinity of the cell-free layer close to channel wall. Conditions for maximal ATP release per cell are identified, which depend on vessel size and hematocrit Ht. Increasing further Ht beyond optimum enhances the total ATP release but should degrade oxygen transport capacity, a compromise between an efficient ATP release and minimal blood dissipation. Moreover, ATP is boosted in capillaries, suggesting a vasomotor activity coordination throughout the resistance network.
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Affiliation(s)
- Zhe Gou
- Université Grenoble Alpes, CNRS, LIPhy, Grenoble, France
| | - Hengdi Zhang
- Université Grenoble Alpes, CNRS, LIPhy, Grenoble, France; Shenzhen Sibionics Co. Ltd., Shenzhen, China
| | - Mehdi Abbasi
- Université Grenoble Alpes, CNRS, LIPhy, Grenoble, France
| | - Chaouqi Misbah
- Université Grenoble Alpes, CNRS, LIPhy, Grenoble, France.
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14
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Yin H, Arpino JM, Lee JJ, Pickering JG. Regenerated Microvascular Networks in Ischemic Skeletal Muscle. Front Physiol 2021; 12:662073. [PMID: 34177614 PMCID: PMC8231913 DOI: 10.3389/fphys.2021.662073] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Accepted: 05/10/2021] [Indexed: 12/24/2022] Open
Abstract
Skeletal muscle is the largest organ in humans. The viability and performance of this metabolically demanding organ are exquisitely dependent on the integrity of its microcirculation. The architectural and functional attributes of the skeletal muscle microvasculature are acquired during embryonic and early postnatal development. However, peripheral vascular disease in the adult can damage the distal microvasculature, together with damaging the skeletal myofibers. Importantly, adult skeletal muscle has the capacity to regenerate. Understanding the extent to which the microvascular network also reforms, and acquires structural and functional competence, will thus be critical to regenerative medicine efforts for those with peripheral artery disease (PAD). Herein, we discuss recent advances in studying the regenerating microvasculature in the mouse hindlimb following severe ischemic injury. We highlight new insights arising from real-time imaging of the microcirculation. This includes identifying otherwise hidden flaws in both network microarchitecture and function, deficiencies that could underlie the progressive nature of PAD and its refractoriness to therapy. Recognizing and overcoming these vulnerabilities in regenerative angiogenesis will be important for advancing treatment options for PAD.
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Affiliation(s)
- Hao Yin
- Robarts Research Institute, Western University, London, ON, Canada
| | | | - Jason J Lee
- Robarts Research Institute, Western University, London, ON, Canada.,Department of Medicine, Western University, London, ON, Canada
| | - J Geoffrey Pickering
- Robarts Research Institute, Western University, London, ON, Canada.,Department of Medicine, Western University, London, ON, Canada.,Department of Medical Biophysics, Western University, London, ON, Canada.,Department of Biochemistry, Western University, London, ON, Canada
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15
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Ghonaim NW, Fraser GM, Goldman D, Milkovich S, Yang J, Ellis CG. Evidence for role of capillaries in regulation of skeletal muscle oxygen supply. Microcirculation 2021; 28:e12699. [PMID: 33853202 DOI: 10.1111/micc.12699] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Revised: 02/23/2021] [Accepted: 03/22/2021] [Indexed: 11/30/2022]
Abstract
How oxygen (O2 ) supply to capillaries is regulated to match the tissue's demand is unknown. Erythrocytes have been proposed as sensors in this regulatory mechanism since they release ATP, a vasodilator, in an oxygen saturation (SO2 )-dependent manner. ATP causes hyperpolarization of endothelial cells resulting in conducted vasodilation to arterioles. OBJECTIVE We propose individual capillary units can regulate their own O2 supply by direct communication to upstream arterioles via electrically coupled endothelium. METHODS To test this hypothesis, we developed a transparent micro-exchange device for localized O2 exchange with surface capillaries of intact tissue. The device was fabricated with an O2 permeable micro-outlet 0.2 × 1.0 mm. Experiments were performed on rat extensor digitorum longus (EDL) muscle using dual wavelength video microscopy to measure capillary hemodynamics and erythrocyte SO2 . Responses to local O2 perturbations were measured with only capillaries positioned over the micro-outlet. RESULTS Step changes in the gas mixture %O2 caused physiological changes in erythrocyte SO2 , and appropriate changes in flow to offset the O2 challenge if at least 3-4 capillaries were stimulated. CONCLUSION These results support our hypothesis that individual capillary units play a role in regulating their erythrocyte supply in response to a changing O2 environment.
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Affiliation(s)
- Nour W Ghonaim
- Biomedical Engineering Graduate Program, The University of Western Ontario, London, ON, Canada
| | - Graham M Fraser
- Division of BioMedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's, NL, Canada
| | - Daniel Goldman
- Biomedical Engineering Graduate Program, The University of Western Ontario, London, ON, Canada.,Department of Medical Biophysics, The University of Western Ontario, London, ON, Canada
| | - Stephanie Milkovich
- Department of Medical Biophysics, The University of Western Ontario, London, ON, Canada.,Schulich School of Medicine & Dentistry, Robarts Research Institute, The University of Western Ontario, London, ON, Canada
| | - Jun Yang
- Biomedical Engineering Graduate Program, The University of Western Ontario, London, ON, Canada.,Department of Mechanical and Materials Engineering, The University of Western Ontario, London, ON, Canada
| | - Christopher G Ellis
- Biomedical Engineering Graduate Program, The University of Western Ontario, London, ON, Canada.,Department of Medical Biophysics, The University of Western Ontario, London, ON, Canada.,Schulich School of Medicine & Dentistry, Robarts Research Institute, The University of Western Ontario, London, ON, Canada
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16
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Mendelson AA, Milkovich S, Hunter T, Vijay R, Choi YH, Milkovich S, Ho E, Goldman D, Ellis CG. The capillary fascicle in skeletal muscle: Structural and functional physiology of RBC distribution in capillary networks. J Physiol 2021; 599:2149-2168. [PMID: 33595111 DOI: 10.1113/jp281172] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Accepted: 02/04/2021] [Indexed: 12/13/2022] Open
Abstract
KEY POINTS The capillary module, consisting of parallel capillaries from arteriole to venule, is classically considered as the building block of complex capillary networks. In skeletal muscle, this structure fails to address how blood flow is regulated along the entire length of the synchronously contracting muscle fibres. Using intravital video microscopy of resting extensor digitorum longus muscle in rats, we demonstrated the capillary fascicle as a series of interconnected modules forming continuous columns that align naturally with the dimensions of the muscle fascicle. We observed structural heterogeneity for module topology, and functional heterogeneity in space and time for capillary-red blood cell (RBC) haemodynamics within a module and between modules. We found that module RBC haemodynamics were independent of module resistance, providing direct evidence for microvascular flow regulation at the level of the capillary module. The capillary fascicle is an updated paradigm for characterizing blood flow and RBC distribution in skeletal muscle capillary networks. ABSTRACT Capillary networks are the fundamental site of oxygen exchange in the microcirculation. The capillary module (CM), consisting of parallel capillaries from terminal arteriole (TA) to post-capillary venule (PCV), is classically considered as the building block of complex capillary networks. In skeletal muscle, this structure fails to address how blood flow is regulated along the entire length of the synchronously contracting muscle fibres, requiring co-ordination from numerous modules. It has previously been recognized that TAs and PCVs interact with multiple CMs, creating interconnected networks. Using label-free intravital video microscopy of resting extensor digitorum longus muscle in rats, we found that these networks form continuous columns of linked CMs spanning thousands of microns, herein denoted as the capillary fascicle (CF); this structure aligns naturally with the dimensions of the muscle fascicle. We measured capillary-red blood cell (RBC) haemodynamics and module topology (n = 9 networks, 327 modules, 1491 capillary segments). The average module had length 481 μm, width 157 μm and 9.51 parallel capillaries. We observed structural heterogeneity for CM topology, and functional heterogeneity in space and time for capillary-RBC haemodynamics within a module and between modules. There was no correlation between capillary RBC velocity and lineal density. A passive inverse relationship between module length and haemodynamics was remarkably absent, providing direct evidence for microvascular flow regulation at the level of the CM. In summary, the CF is an updated paradigm for characterizing RBC distribution in skeletal muscle, and strengthens the theory of capillary networks as major contributors to the signal that regulates capillary perfusion.
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Affiliation(s)
- Asher A Mendelson
- Department of Medicine, Section of Critical Care Medicine, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Stephanie Milkovich
- Department of Medical Biophysics, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada
| | - Timothy Hunter
- Department of Medical Biophysics, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada
| | - Raashi Vijay
- Department of Medical Biophysics, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada
| | - Yun-Hee Choi
- Department of Epidemiology and Biostatistics, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada
| | - Shaun Milkovich
- Department of Medical Biophysics, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada
| | - Edward Ho
- Department of Medical Biophysics, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada
| | - Daniel Goldman
- Department of Medical Biophysics, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada.,Department of Applied Mathematics, Faculty of Science, Western University, London, Ontario, Canada
| | - Christopher G Ellis
- Department of Medical Biophysics, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada.,Robarts Research Institute, London, Ontario, Canada
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17
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Poole DC. Spatial matching of microvascular oxygen delivery to demand in skeletal muscle: Has the missing link been found? J Physiol 2021; 599:2127-2128. [PMID: 33638180 DOI: 10.1113/jp281518] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Accepted: 02/23/2021] [Indexed: 12/31/2022] Open
Affiliation(s)
- David C Poole
- Departments of Kinesiology, Anatomy & Physiology, Kansas State University, Manhattan, KS, USA
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18
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Arpino JM, Nong Z, Li F, Yin H, Ghonaim N, Milkovich S, Balint B, O’Neil C, Fraser GM, Goldman D, Ellis CG, Pickering JG. Four-Dimensional Microvascular Analysis Reveals That Regenerative Angiogenesis in Ischemic Muscle Produces a Flawed Microcirculation. Circ Res 2017; 120:1453-1465. [DOI: 10.1161/circresaha.116.310535] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Revised: 01/20/2017] [Accepted: 02/07/2017] [Indexed: 12/19/2022]
Abstract
Rationale:
Angiogenesis occurs after ischemic injury to skeletal muscle, and enhancing this response has been a therapeutic goal. However, to appropriately deliver oxygen, a precisely organized and exquisitely responsive microcirculation must form. Whether these network attributes exist in a regenerated microcirculation is unknown, and methodologies for answering this have been lacking.
Objective:
To develop 4-dimensional methodologies for elucidating microarchitecture and function of the reconstructed microcirculation in skeletal muscle.
Methods and Results:
We established a model of complete microcirculatory regeneration after ischemia-induced obliteration in the mouse extensor digitorum longus muscle. Dynamic imaging of red blood cells revealed the regeneration of an extensive network of flowing neo-microvessels, which after 14 days structurally resembled that of uninjured muscle. However, the skeletal muscle remained hypoxic. Red blood cell transit analysis revealed slow and stalled flow in the regenerated capillaries and extensive arteriolar-venular shunting. Furthermore, spatial heterogeneity in capillary red cell transit was highly constrained, and red blood cell oxygen saturation was low and inappropriately variable. These abnormalities persisted to 120 days after injury. To determine whether the regenerated microcirculation could regulate flow, the muscle was subjected to local hypoxia using an oxygen-permeable membrane. Hypoxia promptly increased red cell velocity and flux in control capillaries, but in neocapillaries, the response was blunted. Three-dimensional confocal imaging revealed that neoarterioles were aberrantly covered by smooth muscle cells, with increased interprocess spacing and haphazard actin microfilament bundles.
Conclusions:
Despite robust neovascularization, the microcirculation formed by regenerative angiogenesis in skeletal muscle is profoundly flawed in both structure and function, with no evidence for normalizing over time. This network-level dysfunction must be recognized and overcome to advance regenerative approaches for ischemic disease.
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Affiliation(s)
- John-Michael Arpino
- From the Robarts Research Institute (J.-M.A., Z.N., F.L., H.Y., B.B., C.O., J.G.P.), Departments of Medicine (C.G.E., J.G.P.), Medical Biophysics (J.-M.A., S.M., B.B., G.M.F., D.G., C.G.E., J.G.P.), Biochemistry (J.G.P.), and Biomedical Engineering (N.G., D.G.), Western University, London, Canada; and Division of BioMedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John’s, Canada (G.M.F.)
| | - Zengxuan Nong
- From the Robarts Research Institute (J.-M.A., Z.N., F.L., H.Y., B.B., C.O., J.G.P.), Departments of Medicine (C.G.E., J.G.P.), Medical Biophysics (J.-M.A., S.M., B.B., G.M.F., D.G., C.G.E., J.G.P.), Biochemistry (J.G.P.), and Biomedical Engineering (N.G., D.G.), Western University, London, Canada; and Division of BioMedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John’s, Canada (G.M.F.)
| | - Fuyan Li
- From the Robarts Research Institute (J.-M.A., Z.N., F.L., H.Y., B.B., C.O., J.G.P.), Departments of Medicine (C.G.E., J.G.P.), Medical Biophysics (J.-M.A., S.M., B.B., G.M.F., D.G., C.G.E., J.G.P.), Biochemistry (J.G.P.), and Biomedical Engineering (N.G., D.G.), Western University, London, Canada; and Division of BioMedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John’s, Canada (G.M.F.)
| | - Hao Yin
- From the Robarts Research Institute (J.-M.A., Z.N., F.L., H.Y., B.B., C.O., J.G.P.), Departments of Medicine (C.G.E., J.G.P.), Medical Biophysics (J.-M.A., S.M., B.B., G.M.F., D.G., C.G.E., J.G.P.), Biochemistry (J.G.P.), and Biomedical Engineering (N.G., D.G.), Western University, London, Canada; and Division of BioMedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John’s, Canada (G.M.F.)
| | - Nour Ghonaim
- From the Robarts Research Institute (J.-M.A., Z.N., F.L., H.Y., B.B., C.O., J.G.P.), Departments of Medicine (C.G.E., J.G.P.), Medical Biophysics (J.-M.A., S.M., B.B., G.M.F., D.G., C.G.E., J.G.P.), Biochemistry (J.G.P.), and Biomedical Engineering (N.G., D.G.), Western University, London, Canada; and Division of BioMedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John’s, Canada (G.M.F.)
| | - Stephanie Milkovich
- From the Robarts Research Institute (J.-M.A., Z.N., F.L., H.Y., B.B., C.O., J.G.P.), Departments of Medicine (C.G.E., J.G.P.), Medical Biophysics (J.-M.A., S.M., B.B., G.M.F., D.G., C.G.E., J.G.P.), Biochemistry (J.G.P.), and Biomedical Engineering (N.G., D.G.), Western University, London, Canada; and Division of BioMedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John’s, Canada (G.M.F.)
| | - Brittany Balint
- From the Robarts Research Institute (J.-M.A., Z.N., F.L., H.Y., B.B., C.O., J.G.P.), Departments of Medicine (C.G.E., J.G.P.), Medical Biophysics (J.-M.A., S.M., B.B., G.M.F., D.G., C.G.E., J.G.P.), Biochemistry (J.G.P.), and Biomedical Engineering (N.G., D.G.), Western University, London, Canada; and Division of BioMedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John’s, Canada (G.M.F.)
| | - Caroline O’Neil
- From the Robarts Research Institute (J.-M.A., Z.N., F.L., H.Y., B.B., C.O., J.G.P.), Departments of Medicine (C.G.E., J.G.P.), Medical Biophysics (J.-M.A., S.M., B.B., G.M.F., D.G., C.G.E., J.G.P.), Biochemistry (J.G.P.), and Biomedical Engineering (N.G., D.G.), Western University, London, Canada; and Division of BioMedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John’s, Canada (G.M.F.)
| | - Graham M. Fraser
- From the Robarts Research Institute (J.-M.A., Z.N., F.L., H.Y., B.B., C.O., J.G.P.), Departments of Medicine (C.G.E., J.G.P.), Medical Biophysics (J.-M.A., S.M., B.B., G.M.F., D.G., C.G.E., J.G.P.), Biochemistry (J.G.P.), and Biomedical Engineering (N.G., D.G.), Western University, London, Canada; and Division of BioMedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John’s, Canada (G.M.F.)
| | - Daniel Goldman
- From the Robarts Research Institute (J.-M.A., Z.N., F.L., H.Y., B.B., C.O., J.G.P.), Departments of Medicine (C.G.E., J.G.P.), Medical Biophysics (J.-M.A., S.M., B.B., G.M.F., D.G., C.G.E., J.G.P.), Biochemistry (J.G.P.), and Biomedical Engineering (N.G., D.G.), Western University, London, Canada; and Division of BioMedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John’s, Canada (G.M.F.)
| | - Christopher G. Ellis
- From the Robarts Research Institute (J.-M.A., Z.N., F.L., H.Y., B.B., C.O., J.G.P.), Departments of Medicine (C.G.E., J.G.P.), Medical Biophysics (J.-M.A., S.M., B.B., G.M.F., D.G., C.G.E., J.G.P.), Biochemistry (J.G.P.), and Biomedical Engineering (N.G., D.G.), Western University, London, Canada; and Division of BioMedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John’s, Canada (G.M.F.)
| | - J. Geoffrey Pickering
- From the Robarts Research Institute (J.-M.A., Z.N., F.L., H.Y., B.B., C.O., J.G.P.), Departments of Medicine (C.G.E., J.G.P.), Medical Biophysics (J.-M.A., S.M., B.B., G.M.F., D.G., C.G.E., J.G.P.), Biochemistry (J.G.P.), and Biomedical Engineering (N.G., D.G.), Western University, London, Canada; and Division of BioMedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John’s, Canada (G.M.F.)
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19
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Sové RJ, Fraser GM, Goldman D, Ellis CG. Finite Element Model of Oxygen Transport for the Design of Geometrically Complex Microfluidic Devices Used in Biological Studies. PLoS One 2016; 11:e0166289. [PMID: 27829071 PMCID: PMC5102494 DOI: 10.1371/journal.pone.0166289] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Accepted: 10/26/2016] [Indexed: 01/09/2023] Open
Abstract
Red blood cells play a crucial role in the local regulation of oxygen supply in the microcirculation through the oxygen dependent release of ATP. Since red blood cells serve as an oxygen sensor for the circulatory system, the dynamics of ATP release determine the effectiveness of red blood cells to relate the oxygen levels to the vessels. Previous work has focused on the feasibility of developing a microfluidic system to measure the dynamics of ATP release. The objective was to determine if a steep oxygen gradient could be developed in the channel to cause a rapid decrease in hemoglobin oxygen saturation in order to measure the corresponding levels of ATP released from the red blood cells. In the present study, oxygen transport simulations were used to optimize the geometric design parameters for a similar system which is easier to fabricate. The system is composed of a microfluidic device stacked on top of a large, gas impermeable flow channel with a hole to allow gas exchange. The microfluidic device is fabricated using soft lithography in polydimethyl-siloxane, an oxygen permeable material. Our objective is twofold: (1) optimize the parameters of our system and (2) develop a method to assess the oxygen distribution in complex 3D microfluidic device geometries. 3D simulations of oxygen transport were performed to simulate oxygen distribution throughout the device. The simulations demonstrate that microfluidic device geometry plays a critical role in molecule exchange, for instance, changing the orientation of the short wide microfluidic channel results in a 97.17% increase in oxygen exchange. Since microfluidic devices have become a more prominent tool in biological studies, understanding the transport of oxygen and other biological molecules in microfluidic devices is critical for maintaining a physiologically relevant environment. We have also demonstrated a method to assess oxygen levels in geometrically complex microfluidic devices.
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Affiliation(s)
- Richard J. Sové
- Department of Medical Biophysics, Western University, London, Ontario, Canada
| | - Graham M. Fraser
- Department of Medical Biophysics, Western University, London, Ontario, Canada
- Cardiovascular Research Group, Division of BioMedical Sciences, Faculty of Medicine, Memorial University, St. John’s, Newfoundland, Canada
| | - Daniel Goldman
- Department of Medical Biophysics, Western University, London, Ontario, Canada
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20
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Zhang L, Liang L, Tong T, Qin Y, Xu Y, Tong X. Antihyperlipidemic activity of adenosine triphosphate in rabbits fed a high-fat diet and hyperlipidemic patients. PHARMACEUTICAL BIOLOGY 2016; 54:2358-2363. [PMID: 26955742 DOI: 10.3109/13880209.2016.1149493] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Context Recently, adenosine triphosphate (ATP) was occasionally found to decrease the triglyceride (TG) levels in several hyperlipidemic patients in our clinical practice. Objective The study investigates the anti-hyperlipidemic effects of ATP in a high-fat fed rabbit model and hyperlipidemic patients. Materials and methods Twenty-four rabbits were randomly divided into three groups of eight animals each as follows: normal diet, high-fat diet and high-fat diet + ATP group. ATP supplementation (40 mg/day) was started at the 20th day and lasted for 10 days. Serum concentrations of total cholesterol (TC), TG, LDL-C, HDL-C were measured on the 20th day and 30th day. Heart, liver and aorta were subjected histopathological examination. Twenty outpatients diagnosed primary hyperlipidemia took ATP at a dose of 60 mg twice a day for 1 week. Results Feeding rabbits with a high-fat diet resulted in a significant elevation of lipid parameters including TC, TG, LDL-C, VLDL-C compared to the normal diet group (p < 0.01). ATP treatment significantly decreased serum TG level (p < 0.01), whilst other parameters remained statistically unaltered. Meanwhile, ATP significantly reduced the thickness of fat layer in cardiac epicardium (p < 0.05) and pathological gradation of ballooning degeneration in hepatocytes (p < 0.05). After taking ATP for 1 week, hyperlipidemia patients exhibited a significant decrease of TG (p < 0.01), but other lipid parameters had no significant change. Discussion and conclusion The study indicates that ATP selectively decreases serum TG levels in high-fat diet rabbits and hyperlipidemic patients. Therefore, ATP supplementation may provide an effective approach to control TG level.
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Affiliation(s)
- Lianshan Zhang
- a Department of Pathology , Hebei Medical University , Shijiazhuang , P.R. China
| | - Libin Liang
- b Hebei Xinglong Institute of Pharmacological and Medical Science , Shijiazhuang , P.R. China
| | - Tong Tong
- b Hebei Xinglong Institute of Pharmacological and Medical Science , Shijiazhuang , P.R. China
| | - Yuguo Qin
- b Hebei Xinglong Institute of Pharmacological and Medical Science , Shijiazhuang , P.R. China
| | - Yanping Xu
- b Hebei Xinglong Institute of Pharmacological and Medical Science , Shijiazhuang , P.R. China
| | - Xinglong Tong
- b Hebei Xinglong Institute of Pharmacological and Medical Science , Shijiazhuang , P.R. China
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21
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Ellsworth ML, Ellis CG, Sprague RS. Role of erythrocyte-released ATP in the regulation of microvascular oxygen supply in skeletal muscle. Acta Physiol (Oxf) 2016; 216:265-76. [PMID: 26336065 DOI: 10.1111/apha.12596] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Revised: 05/18/2015] [Accepted: 08/28/2015] [Indexed: 12/23/2022]
Abstract
In a 1914 book entitled The Respiratory Function of the Blood, Joseph Barcroft stated that 'the cell takes what it needs and leaves the rest'. He postulated that there must be both a 'call for oxygen' and a 'mechanism by which the call elicits a response...' In the past century, intensive investigation has provided significant insights into the haemodynamic and biophysical mechanisms involved in supplying oxygen to skeletal muscle. However, the identification of the mechanism by which tissue oxygen needs are sensed and the affector responsible for altering the upstream vasculature to enable the need to be appropriately met has been a challenge. In 1995, Ellsworth et al. proposed that the oxygen-carrying erythrocyte, by virtue of its capacity to release the vasoactive mediator ATP in response to a decrease in oxygen saturation, could serve both roles. Several in vitro and in situ studies have established that exposure of erythrocytes to reduced oxygen tension induces the release of ATP which does result in a conducted arteriolar vasodilation with a sufficiently rapid time course to make the mechanism physiologically relevant. The components of the signalling pathway for the controlled release of ATP from erythrocytes in response to exposure to low oxygen tension have been determined. In addition, the implications of defective ATP release on human pathological conditions have been explored. This review provides a perspective on oxygen supply and the role that such a mechanism plays in meeting the oxygen needs of skeletal muscle.
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Affiliation(s)
- M. L. Ellsworth
- Department of Pharmacological and Physiological Science; Saint Louis University School of Medicine; St. Louis MO USA
| | - C. G. Ellis
- Departments of Medical Biophysics and Medicine; Schulich School of Medicine & Dentistry; The University of Western Ontario; London ON Canada
| | - R. S. Sprague
- Department of Pharmacological and Physiological Science; Saint Louis University School of Medicine; St. Louis MO USA
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22
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Burnstock G. Blood cells: an historical account of the roles of purinergic signalling. Purinergic Signal 2015; 11:411-34. [PMID: 26260710 PMCID: PMC4648797 DOI: 10.1007/s11302-015-9462-7] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2015] [Accepted: 07/23/2015] [Indexed: 12/17/2022] Open
Abstract
The involvement of purinergic signalling in the physiology of erythrocytes, platelets and leukocytes was recognised early. The release of ATP and the expression of purinoceptors and ectonucleotidases on erythrocytes in health and disease are reviewed. The release of ATP and ADP from platelets and the expression and roles of P1, P2Y(1), P2Y(12) and P2X1 receptors on platelets are described. P2Y(1) and P2X(1) receptors mediate changes in platelet shape, while P2Y(12) receptors mediate platelet aggregation. The changes in the role of purinergic signalling in a variety of disease conditions are considered. The successful use of P2Y(12) receptor antagonists, such as clopidogrel and ticagrelor, for the treatment of thrombosis, myocardial infarction and stroke is discussed.
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Affiliation(s)
- Geoffrey Burnstock
- Autonomic Neuroscience Centre, University College Medical School, Rowland Hill Street, London, NW3 2PF, UK.
- Department of Pharmacology and Therapeutics, The University of Melbourne, Melbourne, Australia.
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23
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Bateman RM, Sharpe MD, Jagger JE, Ellis CG. Sepsis impairs microvascular autoregulation and delays capillary response within hypoxic capillaries. CRITICAL CARE : THE OFFICIAL JOURNAL OF THE CRITICAL CARE FORUM 2015; 19:389. [PMID: 26537126 PMCID: PMC4634189 DOI: 10.1186/s13054-015-1102-7] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Accepted: 10/16/2015] [Indexed: 11/10/2022]
Abstract
Introduction The microcirculation supplies oxygen (O2) and nutrients to all cells with the red blood cell (RBC) acting as both a deliverer and sensor of O2. In sepsis, a proinflammatory disease with microvascular complications, small blood vessel alterations are associated with multi-organ dysfunction and poor septic patient outcome. We hypothesized that microvascular autoregulation—existing at three levels: over the entire capillary network, within a capillary and within the erythrocyte—was impaired during onset of sepsis. This study had three objectives: 1) measure capillary response time within hypoxic capillaries, 2) test the null hypothesis that RBC O2-dependent adenosine triphosphate (ATP) efflux was not altered by sepsis and 3) develop a framework of a pathophysiological model. Methods This was an animal study, comparing sepsis with control, set in a university laboratory. Acute hypotensive sepsis was studied using cecal ligation and perforation (CLP) with a 6-hour end-point. Rat hindlimb skeletal muscle microcirculation was imaged, and capillary RBC supply rate (SR = RBC/s), RBC hemoglobin O2 saturation (SO2) and O2 supply rate (qO2 = pLO2/s) were quantified. Arterial NOx (nitrite + nitrate) and RBC O2-dependent ATP efflux were measured using a nitric oxide (NO) analyzer and gas exchanger, respectively. Results Sepsis increased capillary stopped-flow (p = 0.001) and increased plasma lactate (p < 0.001). Increased plasma NOx (p < 0.001) was related to increased capillary RBC supply rate (p = 0.027). Analysis of 30-second SR–SO2–qO2 profiles revealed a shift towards decreased (p < 0.05) O2 supply rates in some capillaries. Moreover, we detected a three- to fourfold increase (p < 0.05) in capillary response time within hypoxic capillaries (capillary flow states where RBC SO2 < 20 %). Additionally, sepsis decreased the erythrocyte’s ability to respond to hypoxic environments, as normalized RBC O2-dependent ATP efflux decreased by 62.5 % (p < 0.001). Conclusions Sepsis impaired microvascular autoregulation at both the individual capillary and erythrocyte level, seemingly uncoupling the RBC acting as an “O2 sensor” from microvascular autoregulation. Impaired microvascular autoregulation was manifested by increased capillary stopped-flow, increased capillary response time within hypoxic capillaries, decreased capillary O2 supply rate and decreased RBC O2-dependent ATP efflux. This loss of local microvascular control was partially off-set by increased capillary RBC supply rate, which correlated with increased plasma NOx. Electronic supplementary material The online version of this article (doi:10.1186/s13054-015-1102-7) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Ryon M Bateman
- Department of Medical Biophysics, University of Western Ontario, London, ON, Canada. .,Department of Biochemistry, Keio University School of Medicine, Tokyo, Japan. .,Ryleeon, 18519-77 Ave NW, Edmonton, AB, T5T6A8, Canada.
| | - Michael D Sharpe
- Department of Anesthesia and Critical Care Western, University of Western Ontario, London, ON, Canada.
| | - Justin E Jagger
- Department of Medical Biophysics, University of Western Ontario, London, ON, Canada.
| | - Christopher G Ellis
- Department of Medical Biophysics, University of Western Ontario, London, ON, Canada.
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Abstract
PURPOSE OF REVIEW Oxygen (O2) delivery, the maintenance of which is fundamental to supporting those with critical illness, is a function of blood O2 content and flow. Here, we review red blood cell (RBC) physiology relevant to disordered O2 delivery in the critically ill. RECENT FINDINGS Flow (rather than content) is the focus of O2 delivery regulation. O2 content is relatively fixed, whereas flow fluctuates by several orders of magnitude. Thus, blood flow volume and distribution vary to maintain coupling between O2 delivery and demand. The trapping, processing and delivery of nitric oxide (NO) by RBCs has emerged as a conserved mechanism through which regional blood flow is linked to biochemical cues of perfusion sufficiency. We will review conventional RBC physiology that influences O2 delivery (O2 affinity & rheology) and introduce a new paradigm for O2 delivery homeostasis based on coordinated gas transport and vascular signaling by RBCs. SUMMARY By coordinating vascular signaling in a fashion that links O2 and NO flux, RBCs couple vessel caliber (and thus blood flow) to O2 need in tissue. Malfunction of this signaling system is implicated in a wide array of pathophysiologies and may be explanatory for the dysoxia frequently encountered in the critical care setting.
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Effects of adenosine triphosphate (ATP) on early recovery after total knee arthroplasty (TKA): a randomized, double-blind, controlled study. J Arthroplasty 2014; 29:2347-51. [PMID: 24813646 DOI: 10.1016/j.arth.2014.03.025] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Revised: 03/10/2014] [Accepted: 03/24/2014] [Indexed: 02/01/2023] Open
Abstract
Functional exercise after total knee arthroplasty (TKA) is necessary. However, it may be a difficult and painful process for the patient. Desirable methods of relieving the patient's pain are worth exploring. Oral supplement of adenosine triphosphate (ATP) is a potential option. In the present study, we decide to investigate whether short-term administration of ATP benefits patients undergoing TKA. A total of 244 subjects were randomized to receive 120mg ATP or placebo each day for 4weeks. Significant differences in quadriceps strength, pain scores at postoperative days 7, 14, 21, and 28 and total opioid consumption were detected. It follows that oral supplement of ATP could benefit patients recovering from TKA.
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Ghonaim NW, Fraser GM, Ellis CG, Yang J, Goldman D. Modeling steady state SO2-dependent changes in capillary ATP concentration using novel O2 micro-delivery methods. Front Physiol 2013; 4:260. [PMID: 24069001 PMCID: PMC3781332 DOI: 10.3389/fphys.2013.00260] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2013] [Accepted: 09/03/2013] [Indexed: 11/13/2022] Open
Abstract
Adenosine triphosphate (ATP) is known to be released from the erythrocyte in an oxygen (O2) dependent manner. Since ATP is a potent vasodilator, it is proposed to be a key regulator in the pathway that mediates micro-vascular response to varying tissue O2 demand. We propose that ATP signaling mainly originates in the capillaries due to the relatively long erythrocyte transit times in the capillary and the short ATP diffusion distance to the electrically coupled endothelium. We have developed a computational model to investigate the effect of delivering or removing O2 to limited areas at the surface of a tissue with an idealized parallel capillary array on total ATP concentration. Simulations were conducted when exposing full surface to perturbations in tissue O2 tension (PO2) or locally using a circular micro-outlet (~100 μm in diameter), a square micro-slit (200 × 200 μm), or a rectangular micro-slit (1000 μm wide × 200 μm long). Results indicated the rectangular micro-slit has the optimal dimensions for altering hemoglobin saturations (SO2) in sufficient number capillaries to generate effective changes in total [ATP]. This suggests a threshold for the minimum number of capillaries that need to be stimulated in vivo by imposed tissue hypoxia to induce a conducted micro-vascular response. SO2 and corresponding [ATP] changes were also modeled in a terminal arteriole (9 μm in diameter) that replaces 4 surface capillaries in the idealized network geometry. Based on the results, the contribution of terminal arterioles to the net change in [ATP] in the micro-vascular network is minimal although they would participate as O2 sources thus influencing the O2 distribution. The modeling data presented here provide important insights into designing a novel micro-delivery device for studying micro-vascular O2 regulation in the capillaries in vivo.
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Affiliation(s)
- Nour W Ghonaim
- Department of Biomedical Engineering Graduate Program, Western University London, ON, Canada
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Wilson JM, Joy JM, Lowery RP, Roberts MD, Lockwood CM, Manninen AH, Fuller JC, De Souza EO, Baier SM, Wilson SM, Rathmacher JA. Effects of oral adenosine-5'-triphosphate supplementation on athletic performance, skeletal muscle hypertrophy and recovery in resistance-trained men. Nutr Metab (Lond) 2013; 10:57. [PMID: 24330670 PMCID: PMC3849389 DOI: 10.1186/1743-7075-10-57] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Accepted: 09/13/2013] [Indexed: 11/23/2022] Open
Abstract
Background Currently, there is a lack of studies examining the effects of adenosine-5′-triphosphate (ATP) supplementation utilizing a long-term, periodized resistance-training program (RT) in resistance-trained populations. Therefore, we investigated the effects of 12 weeks of 400 mg per day of oral ATP on muscular adaptations in trained individuals. We also sought to determine the effects of ATP on muscle protein breakdown, cortisol, and performance during an overreaching cycle. Methods The study was a 3-phase randomized, double-blind, and placebo- and diet-controlled intervention. Phase 1 was a periodized resistance-training program. Phase 2 consisted of a two week overreaching cycle in which volume and frequency were increased followed by a 2-week taper (Phase 3). Muscle mass, strength, and power were examined at weeks 0, 4, 8, and 12 to assess the chronic effects of ATP; assessment performance variables also occurred at the end of weeks 9 and 10, corresponding to the mid and endpoints of the overreaching cycle. Results There were time (p < 0.001), and group x time effects for increased total body strength (+55.3 ± 6.0 kg ATP vs. + 22.4 ± 7.1 kg placebo, p < 0.001); increased vertical jump power (+ 796 ± 75 ATP vs. 614 ± 52 watts placebo, p < 0.001); and greater ultrasound determined muscle thickness (+4.9 ± 1.0 ATP vs. (2.5 ± 0.6 mm placebo, p < 0.02) with ATP supplementation. During the overreaching cycle, there were group x time effects for strength and power, which decreased to a greater extent in the placebo group. Protein breakdown was also lower in the ATP group. Conclusions Our results suggest oral ATP supplementation may enhance muscular adaptations following 12-weeks of resistance training, and prevent decrements in performance following overreaching. No statistically or clinically significant changes in blood chemistry or hematology were observed. Trial registration ClinicalTrials.gov NCT01508338
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Welsh DG, Taylor MS. Cell-cell communication in the resistance vasculature: the past, present, and future. Microcirculation 2012; 19:377-8. [PMID: 22640016 DOI: 10.1111/j.1549-8719.2012.00195.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Cell-cell communication among neighboring vascular cells plays an important role in blood flow control. In this overview, we highlight a series of expert opinion articles focused on key issues related to the foundational nature and functional importance of electrical and second messenger communication. These manuscripts are written in an opinionated manner to provoke thought and to illuminate new emerging areas of investigation.
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Affiliation(s)
- Donald G Welsh
- Department of Physiology & Pharmacology, Hotchkiss Brain Institute & Libin Cardiovascular Institute, University of Calgary, Calgary, Alberta, Canada.
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Rathmacher JA, Fuller JC, Baier SM, Abumrad NN, Angus HF, Sharp RL. Adenosine-5'-triphosphate (ATP) supplementation improves low peak muscle torque and torque fatigue during repeated high intensity exercise sets. J Int Soc Sports Nutr 2012; 9:48. [PMID: 23046855 PMCID: PMC3483284 DOI: 10.1186/1550-2783-9-48] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2012] [Accepted: 10/03/2012] [Indexed: 01/08/2023] Open
Abstract
Background Intracellular concentrations of adenosine-5’-triphosphate (ATP) are many times greater than extracellular concentrations (1–10 mM versus 10–100 nM, respectively) and cellular release of ATP is tightly controlled. Transient rises in extracellular ATP and its metabolite adenosine have important signaling roles; and acting through purinergic receptors, can increase blood flow and oxygenation of tissues; and act as neurotransmitters. Increased blood flow not only increases substrate availability but may also aid in recovery through removal of metabolic waste products allowing muscles to accomplish more work with less fatigue. The objective of the present study was to determine if supplemental ATP would improve muscle torque, power, work, or fatigue during repeated bouts of high intensity resistance exercise. Methods Sixteen participants (8 male and 8 female; ages: 21–34 years) were enrolled in a double-blinded, placebo-controlled study using a crossover design. The participants received either supplemental ATP (400 mg/d divided into 2 daily doses) or placebo for 15 d. After an overnight fast, participants underwent strength and fatigue testing, consisting of 3 sets of 50 maximal knee extensions performed on a Biodex® leg dynamometer. Results No differences were detected in high peak torque, power, or total work with ATP supplementation; however, low peak torque in set 2 was significantly improved (p < 0.01). Additionally, in set 3, a trend was detected for less torque fatigue with ATP supplementation (p < 0.10). Conclusions Supplementation with 400 mg ATP/d for 15 days tended to reduce muscle fatigue and improved a participant’s ability to maintain a higher force output at the end of an exhaustive exercise bout.
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Affiliation(s)
- John A Rathmacher
- Department of Animal Science, Iowa State University, Ames, IA, 50010, USA.
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