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Ogoh S, Hirasawa A, Sugawara J, Nakahara H, Ueda S, Shoemaker JK, Miyamoto T. The effect of an acute increase in central blood volume on the response of cerebral blood flow to acute hypotension. J Appl Physiol (1985) 2015; 119:527-33. [DOI: 10.1152/japplphysiol.00277.2015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2015] [Accepted: 07/07/2015] [Indexed: 11/22/2022] Open
Abstract
The purpose of the present study was to examine whether the response of cerebral blood flow to an acute change in perfusion pressure is modified by an acute increase in central blood volume. Nine young, healthy subjects voluntarily participated in this study. To measure dynamic cerebral autoregulation during normocapnic and hypercapnic (5%) conditions, the change in middle cerebral artery mean blood flow velocity was analyzed during acute hypotension caused by two methods: 1) thigh-cuff occlusion release (without change in central blood volume); and 2) during the recovery phase immediately following release of lower body negative pressure (LBNP; −50 mmHg) that initiated an acute increase in central blood volume. In the thigh-cuff occlusion release protocol, as expected, hypercapnia decreased the rate of regulation, as an index of dynamic cerebral autoregulation (0.236 ± 0.018 and 0.167 ± 0.025 s−1, P = 0.024). Compared with the cuff-occlusion release, the acute increase in central blood volume (relative to the LBNP condition) with LBNP release attenuated dynamic cerebral autoregulation ( P = 0.009). Therefore, the hypercapnia-induced attenuation of dynamic cerebral autoregulation was not observed in the LBNP release protocol ( P = 0.574). These findings suggest that an acute change in systemic blood distribution modifies dynamic cerebral autoregulation during acute hypotension.
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Affiliation(s)
| | | | - Jun Sugawara
- National Institute of Advanced Industrial Science and Technology, Ibaraki Japan
| | | | - Shinya Ueda
- Morinomiya University of Medical Sciences, Osaka, Japan; and
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152
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Hamilton GF, Rhodes JS. Exercise Regulation of Cognitive Function and Neuroplasticity in the Healthy and Diseased Brain. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2015; 135:381-406. [PMID: 26477923 DOI: 10.1016/bs.pmbts.2015.07.004] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Regular exercise broadly enhances physical and mental health throughout the lifespan. Animal models have provided us with the tools to gain a better understanding of the underlying biochemical, physiological, and morphological mechanisms through which exercise exerts its beneficial cognitive effects. One brain region in particular, the hippocampus, is especially responsive to exercise. It is critically involved in learning and memory and is one of two regions in the mammalian brain that continues to generate new neurons throughout life. Exercise prevents the decline of the hippocampus from aging and ameliorates many neurodegenerative diseases, in part by increasing adult hippocampal neurogenesis but also by activating a multitude of molecular mechanisms that promote brain health. In this chapter, we first describe some rodent models used to study effects of exercise on the brain. Then we review the rodent work focusing on the mechanisms behind which exercise improves cognition and brain health in both the normal and the diseased brain, with emphasis on the hippocampus.
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Affiliation(s)
- Gilian F Hamilton
- Department of Psychology, The Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.
| | - Justin S Rhodes
- Department of Psychology, The Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
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153
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Wallace PJ, Masbou AT, Petersen SR, Cheung SS. The effects of cranial cooling during recovery on subsequent uncompensable heat stress tolerance. Appl Physiol Nutr Metab 2015; 40:811-6. [PMID: 26187272 DOI: 10.1139/apnm-2015-0067] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study compared cranial (CC) with passive (CON) cooling during recovery on tolerance to subsequent exercise while wearing firefighting protective ensemble and self-contained breathing apparatus in a hot-humid environment. Eleven males (mean ± SD; age, 30.9 ± 9.2 years; peak oxygen consumption, 49.5 ± 5.1 mL · kg(-1) · min(-1)) performed 2 × 20 min treadmill walks (5.6 km · h(-1), 4% incline) in 35 °C and 60% relative humidity. During a 20-min recovery (rest), participants sat and removed gloves, helmets, and flash hoods but otherwise remained encapsulated. A close-fitting liquid-perfused hood pumped 13 °C water at ∼ 500 mL · min(-1) through the head and neck (CC) or no cooling hood was worn (CON). During rest, neck temperature was lower in CC compared with CON from 4 min (CC: 35.73 ± 3.28 °C, CON: 37.66 ± 1.35 °C, p = 0.025) until the end (CC: 33.06 ± 4.70 °C, CON: 36.85 ± 1.63 °C, p = 0.014). Rectal temperature rose in both CC (0.11 ± 0.19 °C) and CON (0.26 ± 0.15 °C) during rest, with nonsignificant interaction between conditions (p = 0.076). Perceived thermal stress was lower (p = 0.006) from 5 min of CC (median: 3 (quartile 1: 3, quartile 3: 4)) until the end of rest compared with CON (median: 4 (quartile 1: 4, quartile 3: 4)). However, there were no significant differences (p = 0.906) in tolerance times during the second exercise between CC (16.55 ± 1.14 min) and CON (16.60 ± 1.31 min), nor were there any difference in rectal temperature at the start (CC: 38.30 ± 0.40 °C, CON: 38.40 ± 0.16 °C, p = 0.496) or at the end (CC: 38.82 ± 0.23 °C, CON: 39.07 ± 0.22 °C, p = 0.173). With high ambient heat and encapsulation, cranial and neck cooling during recovery decreases physiological strain and perceived thermal stress, but is ineffective in improving subsequent uncompensable heat stress tolerance.
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Affiliation(s)
- Phillip J Wallace
- a Environmental Ergonomics Laboratory, Department of Kinesiology, Brock University, St. Catharines, ON L2S 3A1, Canada
| | - Anaïs T Masbou
- a Environmental Ergonomics Laboratory, Department of Kinesiology, Brock University, St. Catharines, ON L2S 3A1, Canada
| | - Stewart R Petersen
- b Work Physiology Laboratory, Faculty of Physical Education and Recreation, University of Alberta, Edmonton, AB T6G-2H9, Canada
| | - Stephen S Cheung
- a Environmental Ergonomics Laboratory, Department of Kinesiology, Brock University, St. Catharines, ON L2S 3A1, Canada
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154
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Ice slurry ingestion reduces both core and facial skin temperatures in a warm environment. J Therm Biol 2015; 51:105-9. [DOI: 10.1016/j.jtherbio.2015.03.008] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Revised: 03/17/2015] [Accepted: 03/17/2015] [Indexed: 11/21/2022]
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155
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Lucas SJE, Cotter JD, Brassard P, Bailey DM. High-intensity interval exercise and cerebrovascular health: curiosity, cause, and consequence. J Cereb Blood Flow Metab 2015; 35:902-11. [PMID: 25833341 PMCID: PMC4640257 DOI: 10.1038/jcbfm.2015.49] [Citation(s) in RCA: 136] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Revised: 01/25/2015] [Accepted: 03/01/2015] [Indexed: 12/14/2022]
Abstract
Exercise is a uniquely effective and pluripotent medicine against several noncommunicable diseases of westernised lifestyles, including protection against neurodegenerative disorders. High-intensity interval exercise training (HIT) is emerging as an effective alternative to current health-related exercise guidelines. Compared with traditional moderate-intensity continuous exercise training, HIT confers equivalent if not indeed superior metabolic, cardiac, and systemic vascular adaptation. Consequently, HIT is being promoted as a more time-efficient and practical approach to optimize health thereby reducing the burden of disease associated with physical inactivity. However, no studies to date have examined the impact of HIT on the cerebrovasculature and corresponding implications for cognitive function. This review critiques the implications of HIT for cerebrovascular function, with a focus on the mechanisms and translational impact for patient health and well-being. It also introduces similarly novel interventions currently under investigation as alternative means of accelerating exercise-induced cerebrovascular adaptation. We highlight a need for studies of the mechanisms and thereby also the optimal dose-response strategies to guide exercise prescription, and for studies to explore alternative approaches to optimize exercise outcomes in brain-related health and disease prevention. From a clinical perspective, interventions that selectively target the aging brain have the potential to prevent stroke and associated neurovascular diseases.
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Affiliation(s)
- Samuel J E Lucas
- 1] School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, UK [2] Department of Physiology, University of Otago, Dunedin, New Zealand
| | - James D Cotter
- School of Physical Education, Sport and Exercise Sciences, University of Otago, Dunedin, New Zealand
| | - Patrice Brassard
- 1] Department of Kinesiology, Faculty of Medicine, Université Laval, Québec, Canada [2] Research Center of the Institut Universitaire de Cardiologie et de Pneumologie de Québec, Québec, Canada
| | - Damian M Bailey
- 1] Neurovascular Research Laboratory, Faculty of Life Sciences and Education, University of South Wales, South Wales, UK [2] Université de Provence Marseille, Sondes Moléculaires en Biologie, Laboratoire Chimie Provence UMR 6264 CNRS, Marseille, France
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156
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Barnes JN. Exercise, cognitive function, and aging. ADVANCES IN PHYSIOLOGY EDUCATION 2015; 39:55-62. [PMID: 26031719 PMCID: PMC4587595 DOI: 10.1152/advan.00101.2014] [Citation(s) in RCA: 170] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Accepted: 03/06/2015] [Indexed: 05/31/2023]
Abstract
Increasing the lifespan of a population is often a marker of a country's success. With the percentage of the population over 65 yr of age expanding, managing the health and independence of this population is an ongoing concern. Advancing age is associated with a decrease in cognitive function that ultimately affects quality of life. Understanding potential adverse effects of aging on brain blood flow and cognition may help to determine effective strategies to mitigate these effects on the population. Exercise may be one strategy to prevent or delay cognitive decline. This review describes how aging is associated with cardiovascular disease risks, vascular dysfunction, and increasing Alzheimer's disease pathology. It will also discuss the possible effects of aging on cerebral vascular physiology, cerebral perfusion, and brain atrophy rates. Clinically, these changes will present as reduced cognitive function, neurodegeneration, and the onset of dementia. Regular exercise has been shown to improve cognitive function, and we hypothesize that this occurs through beneficial adaptations in vascular physiology and improved neurovascular coupling. This review highlights the potential interactions and ideas of how the age-associated variables may affect cognition and may be moderated by regular exercise.
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Affiliation(s)
- Jill N Barnes
- Department of Anesthesiology, and Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
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157
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Périard JD, Racinais S. Heat stress exacerbates the reduction in middle cerebral artery blood velocity during prolonged self-paced exercise. Scand J Med Sci Sports 2015; 25 Suppl 1:135-44. [DOI: 10.1111/sms.12379] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/23/2014] [Indexed: 11/30/2022]
Affiliation(s)
- J. D. Périard
- Athlete Health and Performance Research Centre; Aspetar Orthopaedic and Sports Medicine Hospital; Doha Qatar
| | - S. Racinais
- Athlete Health and Performance Research Centre; Aspetar Orthopaedic and Sports Medicine Hospital; Doha Qatar
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158
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Affiliation(s)
- Anthony R Bain
- Centre for Heart Lung and Vascular Health, University of British Columbia, Kelowna, Canada
| | - Philip N Ainslie
- Centre for Heart Lung and Vascular Health, University of British Columbia, Kelowna, Canada
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159
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Exhaustive exercise attenuates the neurovascular coupling by blunting the pressor response to visual stimulation. BIOMED RESEARCH INTERNATIONAL 2015; 2015:671063. [PMID: 25866801 PMCID: PMC4383341 DOI: 10.1155/2015/671063] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/09/2014] [Revised: 10/18/2014] [Accepted: 11/01/2014] [Indexed: 11/17/2022]
Abstract
Neurovascular coupling (NVC) is assessed as an increase response to visual stimulation, and is monitored by blood flow of the posterior cerebral artery (PCA). To investigate whether exhaustive exercise modifies NVC, and more specifically, the relative contributions of vasodilatation in the downstream of PCA and the pressor response on NVC, we measured blood flow velocity in the PCA (PCAv) in 13 males using transcranial Doppler ultrasound flowmetry during a leg-cycle exercise at 75% of maximal heart rate until exhaustion. NVC was estimated as the relative change in PCAv from the mean value obtained during 20-s with the eyes closed to the peak value obtained during 40-s of visual stimulation involving looking at a reversed checkerboard. Conductance index (CI) was calculated by dividing PCAv by mean arterial pressure (MAP) to evaluate the vasodilatation. At exhaustion, PCAv was significantly decreased relative to baseline measurements, and the PCAv response to visual stimulation significantly decreased. Compared to baseline, exhaustive exercise significantly suppressed the increase in MAP to visual stimulation, while the CI response did not significantly change by the exercise. These results suggest that exhaustive exercise attenuates the magnitude of NVC by blunting the pressor response to visual stimulation.
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160
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Avnstorp MB, Rasmussen P, Brassard P, Seifert T, Overgaard M, Krustrup P, Secher NH, Nordsborg NB. Cerebral water and ion balance remains stable when humans are exposed to acute hypoxic exercise. High Alt Med Biol 2015; 16:18-25. [PMID: 25761236 DOI: 10.1089/ham.2014.1075] [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: 11/12/2022] Open
Abstract
BACKGROUND Intense physical activity increases the prevalence of acute mountain sickness (AMS) that can occur within 10 h after ascent to altitudes above 1500 m and is likely related to development of cerebral edema. This study evaluated whether disturbed cerebral water and ion homeostasis can be detected when intense exercise is carried out in hypoxia and monitored the influence of muscle metabolism for changes in arterial variables. METHODS On two separate days, in random order, 30 min cycling exercise was performed in either hypoxia (10% O2) or normoxia at an intensity that was exhaustive in the hypoxic trial (∼120 W; n=9). RESULTS Exercise in hypoxia affected muscle metabolism, as evidenced by higher (p<0.05) leg lactate release at 7.5 min and a continuous decline in arterial pH (p<0.001) that was not observed in normoxia. Middle cerebral artery flow velocity increased (p<0.01) with exercise under both circumstances. No cerebral net exchange of Na(+) or K(+) was evident. Likewise, no significant net-exchange of water over the brain was demonstrated and the arterial and jugular venous hemoglobin concentrations were similar. CONCLUSION Challenging exercise in hypoxia for 30 min affected muscle metabolism and increased an index of cerebral blood flow, but cerebral net water and ion homeostasis remained stable. Thus, although AMS develops within hours and may be related to exercise-induced disturbance of cerebral ion and water balance, such changes are not detectable when subjects are exposed to acute 30 min maximal exercise in hypoxia.
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Affiliation(s)
- Magnus B Avnstorp
- 1 Department of Anesthesia, The Copenhagen Muscle Research Center, Rigshospitalet, University of Copenhagen , Copenhagen, Denmark
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161
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Ogoh S, Sato K, Okazaki K, Miyamoto T, Hirasawa A, Sadamoto T, Shibasaki M. Blood flow in internal carotid and vertebral arteries during graded lower body negative pressure in humans. Exp Physiol 2015; 100:259-66. [DOI: 10.1113/expphysiol.2014.083964] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Accepted: 01/09/2015] [Indexed: 11/08/2022]
Affiliation(s)
- Shigehiko Ogoh
- Department of Biomedical Engineering; Toyo University; Saitama Japan
| | - Kohei Sato
- Research Institute of Physical Fitness; Japan Women's College of Physical Education; Tokyo Japan
| | - Kazunobu Okazaki
- Department of Environmental Physiology for Exercise; Osaka City University Graduate School of Medicine; Osaka Japan
| | | | - Ai Hirasawa
- Department of Biomedical Engineering; Toyo University; Saitama Japan
| | - Tomoko Sadamoto
- Research Institute of Physical Fitness; Japan Women's College of Physical Education; Tokyo Japan
| | - Manabu Shibasaki
- Department of Environmental Health; Nara Women's University; Nara Japan
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162
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Smith KJ, MacLeod D, Willie CK, Lewis NCS, Hoiland RL, Ikeda K, Tymko MM, Donnelly J, Day TA, MacLeod N, Lucas SJE, Ainslie PN. Influence of high altitude on cerebral blood flow and fuel utilization during exercise and recovery. J Physiol 2014; 592:5507-27. [PMID: 25362150 PMCID: PMC4270509 DOI: 10.1113/jphysiol.2014.281212] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Accepted: 10/18/2014] [Indexed: 11/08/2022] Open
Abstract
We examined the hypotheses that: (1) during incremental exercise and recovery following 4-6 days at high altitude (HA) global cerebral blood flow (gCBF) increases to preserve cerebral oxygen delivery (CDO2) in excess of that required by an increasing cerebral metabolic rate of oxygen ( CM RO2); (2) the trans-cerebral exchange of oxygen vs. carbohydrates (OCI; carbohydrates = glucose + ½lactate) would be similar during exercise and recovery at HA and sea level (SL). Global CBF, intra-cranial arterial blood velocities, extra-cranial blood flows, and arterial-jugular venous substrate differences were measured during progressive steady-state exercise (20, 40, 60, 80, 100% maximum workload (Wmax)) and through 30 min of recovery. Measurements (n = 8) were made at SL and following partial acclimatization to 5050 m. At HA, absolute Wmax was reduced by ∼50%. During submaximal exercise workloads (20-60% Wmax), despite an elevated absolute gCBF (∼20%, P < 0.05) the relative increases in gCBF were not different at HA and SL. In contrast, gCBF was elevated at HA compared with SL during 80 and 100% Wmax and recovery. Notwithstanding a maintained CDO2 and elevated absolute CM RO2 at HA compared with SL, the relative increase in CM RO2 was similar during 20-80% Wmax but half that of the SL response (i.e. 17 vs. 27%; P < 0.05 vs. SL) at 100% Wmax. The OCI was reduced at HA compared with SL during 20, 40, and 60% Wmax but comparable at 80 and 100% Wmax. At HA, OCI returned almost immediately to baseline values during recovery, whereas at SL it remained below baseline. In conclusion, the elevations in gCBF during exercise and recovery at HA serve to maintain CDO2. Despite adequate CDO2 at HA the brain appears to increase non-oxidative metabolism during exercise and recovery.
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Affiliation(s)
- K J Smith
- Centre for Heart Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, BC, Canada
| | - D MacLeod
- Department of Anesthesiology, Duke University Medical Center, Durham, NC, USA
| | - C K Willie
- Centre for Heart Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, BC, Canada
| | - N C S Lewis
- Centre for Heart Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, BC, Canada
| | - R L Hoiland
- Centre for Heart Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, BC, Canada
| | - K Ikeda
- Department of Anesthesiology, Duke University Medical Center, Durham, NC, USA
| | - M M Tymko
- Centre for Heart Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, BC, Canada
| | - J Donnelly
- University of Otago, Dunedin, New Zealand University Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
| | - T A Day
- Department of Biology, Mount Royal Univeristy, Calgary, AB, Canada
| | - N MacLeod
- Carolina Friends School, Durham, NC, USA
| | - S J E Lucas
- University of Otago, Dunedin, New Zealand University of Birmingham, Birmingham, UK
| | - P N Ainslie
- Centre for Heart Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, BC, Canada
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163
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Di Achille P, Tellides G, Figueroa CA, Humphrey JD. A haemodynamic predictor of intraluminal thrombus formation in abdominal aortic aneurysms. Proc Math Phys Eng Sci 2014. [DOI: 10.1098/rspa.2014.0163] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Intraluminal thrombus (ILT) is present in over 75% of all abdominal aortic aneurysms (AAAs) and probably contributes to the complex biomechanics and pathobiology of these lesions. A reliable predictor of thrombus formation in enlarging lesions could thereby aid clinicians in treatment planning. The primary goal of this work was to identify a new phenomenological metric having clinical utility that is motivated by the hypothesis that two basic haemodynamic features must coincide spatially and temporally to promote the formation of a thrombus on an intact endothelium—platelets must be activated within a shear flow and then be presented to a susceptible endothelium. Towards this end, we propose a new thrombus formation potential (TFP) that combines information on the flow-induced shear history experienced by blood-borne particles that come in close proximity to the endothelium with information on both the time-averaged wall shear stress (WSS) and the oscillatory shear index (OSI) that locally affect the endothelial mechanobiology. To illustrate the possible utility of this new metric, we show computational results for 10 carotid arteries from five patients where regions of low WSS and high OSI tend not to be presented with activated platelets (i.e. they have a low TFP), consistent with the thrombo-resistance of the healthy carotid despite its complex haemodynamics. Conversely, we show results for three patients that high TFP co-localizes with regions of observed thin thrombus in AAAs, which contrasts with findings of low TFP for the abdominal aorta of three healthy subjects. We submit that these promising results suggest the need for further consideration of the TFP, or a similar combined metric, as a potentially useful clinical predictor of the possible formation of ILT in AAAs.
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Affiliation(s)
- P. Di Achille
- Department of Biomedical Engineering, Yale University, New Haven, CT, USA
| | - G. Tellides
- Department of Surgery, Yale School of Medicine, New Haven, CT, USA
- Vascular Biology and Therapeutics Program, Yale School of Medicine, New Haven, CT, USA
| | - C. A. Figueroa
- Department of Surgery and Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - J. D. Humphrey
- Department of Biomedical Engineering, Yale University, New Haven, CT, USA
- Vascular Biology and Therapeutics Program, Yale School of Medicine, New Haven, CT, USA
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164
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Nybo L, Rasmussen P, Sawka MN. Performance in the heat-physiological factors of importance for hyperthermia-induced fatigue. Compr Physiol 2014; 4:657-89. [PMID: 24715563 DOI: 10.1002/cphy.c130012] [Citation(s) in RCA: 201] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
This article presents a historical overview and an up-to-date review of hyperthermia-induced fatigue during exercise in the heat. Exercise in the heat is associated with a thermoregulatory burden which mediates cardiovascular challenges and influence the cerebral function, increase the pulmonary ventilation, and alter muscle metabolism; which all potentially may contribute to fatigue and impair the ability to sustain power output during aerobic exercise. For maximal intensity exercise, the performance impairment is clearly influenced by cardiovascular limitations to simultaneously support thermoregulation and oxygen delivery to the active skeletal muscle. In contrast, during submaximal intensity exercise at a fixed intensity, muscle blood flow and oxygen consumption remain unchanged and the potential influence from cardiovascular stressing and/or high skin temperature is not related to decreased oxygen delivery to the skeletal muscles. Regardless, performance is markedly deteriorated and exercise-induced hyperthermia is associated with central fatigue as indicated by impaired ability to sustain maximal muscle activation during sustained contractions. The central fatigue appears to be influenced by neurotransmitter activity of the dopaminergic system, but inhibitory signals from thermoreceptors arising secondary to the elevated core, muscle and skin temperatures and augmented afferent feedback from the increased ventilation and the cardiovascular stressing (perhaps baroreceptor sensing of blood pressure stability) and metabolic alterations within the skeletal muscles are likely all factors of importance for afferent feedback to mediate hyperthermia-induced fatigue during submaximal intensity exercise. Taking all the potential factors into account, we propose an integrative model that may help understanding the interplay among factors, but also acknowledging that the influence from a given factor depends on the exercise hyperthermia situation.
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Affiliation(s)
- Lars Nybo
- Department of Nutrition, Exercise and Sport Sciences, University of Copenhagen, Denmark
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165
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Gassner M, Killu K, Bauman Z, Coba V, Rosso K, Blyden D. Feasibility of common carotid artery point of care ultrasound in cardiac output measurements compared to invasive methods. J Ultrasound 2014; 18:127-33. [PMID: 26191100 DOI: 10.1007/s40477-014-0139-9] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2014] [Accepted: 10/14/2014] [Indexed: 10/24/2022] Open
Abstract
BACKGROUND Cardiac output (CO) measurement in the intensive care unit (ICU) requires invasive devices such as the pulmonary artery (PA) catheter or arterial waveform pulse contour analysis (PCA). This study tests the accuracy and feasibility of point of care ultrasound (POCUS) of the common carotid artery to estimate the CO non-invasively and compare it to existing invasive CO measurement modalities. METHODS Patients admitted to the surgical and cardiothoracic ICU in a tertiary university-affiliated academic center during a 4-month period, with invasive hemodynamic monitoring devices for management, were included in this cohort study. Common carotid artery POCUS was performed to measure the CO and the results were compared to an invasive device. RESULTS Intensivists and ICU fellows, using ultrasound of the common carotid artery, obtained the CO measurements. Images of the Doppler flow and volume were obtained at the level of the thyroid gland. Concurrent CO measured via invasive devices was recorded. The patient cohort comprised 36 patients; 52 % were females. The average age was 59 ± 13 years, and 66 % were monitored via PCA device and 33 % via PA catheter. Intraclass correlation coefficient (ICC) analysis demonstrated almost perfect correlation (0.8152) between measurements of CO via ultrasound vs. invasive modalities. The ICC between POCUS and the invasive measurement via PCA was 0.84 and via PA catheter 0.74, showing substantial agreement between the ultrasound and both invasive modalities. CONCLUSIONS Common carotid artery POCUS offers a non-invasive method of measuring the CO in the critically ill population.
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Affiliation(s)
- Marika Gassner
- Division of Trauma and Critical Care/Department of Surgery/Senior Staff, Henry Ford Hospital, 2799 W. Grand Blvd, Detroit, Michigan, MI 48202 USA
| | - Keith Killu
- Division of Trauma and Critical Care/Department of Surgery/Senior Staff, Henry Ford Hospital, 2799 W. Grand Blvd, Detroit, Michigan, MI 48202 USA
| | - Zachary Bauman
- Division of Trauma and Critical Care/Department of Surgery/Senior Staff, Henry Ford Hospital, 2799 W. Grand Blvd, Detroit, Michigan, MI 48202 USA
| | - Victor Coba
- Division of Trauma and Critical Care/Department of Surgery/Senior Staff, Henry Ford Hospital, 2799 W. Grand Blvd, Detroit, Michigan, MI 48202 USA
| | - Kelly Rosso
- Division of Trauma and Critical Care/Department of Surgery/Senior Staff, Henry Ford Hospital, 2799 W. Grand Blvd, Detroit, Michigan, MI 48202 USA
| | - Dionne Blyden
- Division of Trauma and Critical Care/Department of Surgery/Senior Staff, Henry Ford Hospital, 2799 W. Grand Blvd, Detroit, Michigan, MI 48202 USA
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166
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Fonseca CG, Pires W, Lima MRM, Guimarães JB, Lima NRV, Wanner SP. Hypothalamic temperature of rats subjected to treadmill running in a cold environment. PLoS One 2014; 9:e111501. [PMID: 25365556 PMCID: PMC4218756 DOI: 10.1371/journal.pone.0111501] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Accepted: 09/30/2014] [Indexed: 12/02/2022] Open
Abstract
Different strategies for cooling the body prior to or during physical exercise have been shown to improve prolonged performance. Because of ethical and methodological issues, no studies conducted in humans have evaluated the changes in brain temperature promoted by cooling strategies. Therefore, our first aim sought to measure the hypothalamic temperature (Thyp) of rats subjected to treadmill running in a cold environment. Moreover, evidence suggests that Thyp and abdominal temperature (Tabd) are regulated by different physiological mechanisms. Thus, this study also investigated the dynamics of exercise-induced changes in Thyp and Tabd at two ambient temperatures: 25°C (temperate environment) and 12°C (cold). Adult male Wistar rats were used in these experiments. The rats were implanted with a guide cannula in the hypothalamus and a temperature sensor in the abdominal cavity. After recovery from this surgery, the rats were familiarized with running on a treadmill and were then subjected to the two experimental trials: constant-speed running (20 m/min) at 12°C and 25°C. Both Thyp and Tabd increased during exercise at 25°C. In contrast, Thyp and Tabd remained unchanged during fatiguing exercise at 12°C. The temperature differential (i.e., Thyp - Tabd) increased during the initial min of running at 25°C and thereafter decreased toward pre-exercise values. Interestingly, external cooling prevented this early increase in the temperature differential from the 2nd to the 8th min of running. In addition, the time until volitional fatigue was higher during the constant exercise at 12°C compared with 25°C. Together, our results indicate that Thyp and Tabd are regulated by different mechanisms in running rats and that external cooling affected the relationship between both temperature indexes observed during exercise without environmental thermal stress. Our data also suggest that attenuated hypothalamic hyperthermia may contribute to improved performance in cold environments.
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Affiliation(s)
- Cletiana Gonçalves Fonseca
- Exercise Physiology Laboratory, School of Physical Education, Physiotherapy and Occupational Therapy, Universidade Federal de Minas Gerais, Belo Horizonte (MG), Brazil
| | - Washington Pires
- Exercise Physiology Laboratory, School of Physical Education, Physiotherapy and Occupational Therapy, Universidade Federal de Minas Gerais, Belo Horizonte (MG), Brazil
| | - Milene Rodrigues Malheiros Lima
- Exercise Physiology Laboratory, School of Physical Education, Physiotherapy and Occupational Therapy, Universidade Federal de Minas Gerais, Belo Horizonte (MG), Brazil
| | - Juliana Bohnen Guimarães
- Exercise Physiology Laboratory, School of Physical Education, Physiotherapy and Occupational Therapy, Universidade Federal de Minas Gerais, Belo Horizonte (MG), Brazil
- Instituto Superior de Educação Anísio Teixeira, Universidade Estadual de Minas Gerais, Ibirité (MG), Brazil
| | - Nilo Resende Viana Lima
- Exercise Physiology Laboratory, School of Physical Education, Physiotherapy and Occupational Therapy, Universidade Federal de Minas Gerais, Belo Horizonte (MG), Brazil
| | - Samuel Penna Wanner
- Exercise Physiology Laboratory, School of Physical Education, Physiotherapy and Occupational Therapy, Universidade Federal de Minas Gerais, Belo Horizonte (MG), Brazil
- * E-mail:
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167
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Ishii K, Matsukawa K, Liang N, Endo K, Idesako M, Hamada H, Kataoka T, Ueno K, Watanabe T, Takahashi M. Differential contribution of ACh-muscarinic and β-adrenergic receptors to vasodilatation in noncontracting muscle during voluntary one-legged exercise. Physiol Rep 2014; 2:e12202. [PMID: 25413322 PMCID: PMC4255809 DOI: 10.14814/phy2.12202] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2014] [Revised: 10/15/2014] [Accepted: 10/15/2014] [Indexed: 12/21/2022] Open
Abstract
We have demonstrated the centrally induced cholinergic vasodilatation in skeletal muscle at the early period of voluntary one-legged exercise and during motor imagery in humans. The purpose of this study was to examine whether central command may also cause β-adrenergic vasodilatation during the exercise and motor imagery. Relative changes in oxygenated hemoglobin concentration (Oxy-Hb) of bilateral vastus lateralis (VL) muscles, as index of tissue blood flow, and femoral blood flow to nonexercising limb were measured during one-legged cycling and mental imagery of the exercise for 1 min before and after propranolol (0.1 mg/kg iv). The Oxy-Hb of noncontracting muscle increased (P < 0.05) at the early period of exercise and the increase was sustained throughout exercise, whereas the Oxy-Hb of contracting muscle increased at the early period but thereafter decreased. We subtracted the Oxy-Hb response with propranolol from the control response in individual subjects to identify the propranolol-sensitive component of the Oxy-Hb response during exercise. In both noncontracting and contracting VL muscles, the increase in Oxy-Hb at the early period of one-legged exercise did not involve a significant propranolol-sensitive component. However, as the exercise proceeded, the propranolol-sensitive component of the Oxy-Hb response was developed during the later period of exercise. Propranolol also failed to affect the initial increases in femoral blood flow and vascular conductance of nonexercising leg but significantly attenuated (P < 0.05) their later increases during exercise. Subsequent atropine (10-15 μg/kg iv) abolished the initial increases in Oxy-Hb of both VL muscles. Mental imagery of the one-legged exercise caused the bilateral increases in Oxy-Hb, which were not altered by propranolol but abolished by subsequent atropine. It is likely that the rapid cholinergic and delayed β-adrenergic vasodilator mechanisms cooperate to increase muscle blood flow during exercise.
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Affiliation(s)
- Kei Ishii
- Department of Integrative Physiology, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - Kanji Matsukawa
- Department of Integrative Physiology, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - Nan Liang
- Department of Integrative Physiology, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - Kana Endo
- Department of Integrative Physiology, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - Mitsuhiro Idesako
- Department of Integrative Physiology, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - Hironobu Hamada
- Department of Physical Analysis and Therapeutic Sciences, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - Tsuyoshi Kataoka
- Department of Health Care for Adults, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - Kazumi Ueno
- Department of Health Care for Adults, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - Tae Watanabe
- Department of Health Care for Adults, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - Makoto Takahashi
- Department of Biomechanics, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
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168
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Brain BDNF levels elevation induced by physical training is reduced after unilateral common carotid artery occlusion in rats. J Cereb Blood Flow Metab 2014; 34:1681-7. [PMID: 25052557 PMCID: PMC4269729 DOI: 10.1038/jcbfm.2014.133] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/18/2014] [Revised: 06/17/2014] [Accepted: 06/26/2014] [Indexed: 11/09/2022]
Abstract
We investigated the contribution of blood flow elevation in the cerebrovasculature to physical training-induced brain-derived neurotrophic factor (BDNF) levels elevation in the brain. Brain-derived neurotrophic factor protein levels were measured in the motor cortex 24 h after the last session of a forced treadmill walking (30 minutes a day, 18 m/minute for 7 consecutive days). Unilateral common carotid artery occlusion and modulation of exercise intensity (0 versus -10% inclination of the treadmill) were used as strategies to reduce the (normal) elevation of flow in the cerebrovasculature occurring during exercise. Administration of N-nitro-L-arginine methyl ester (L-NAME, 60 mg/kg before each exercise sessions) and genetic hypertension (spontaneously hypertensive rats) were used as approaches to reduce stimulation of nitric oxide production in response to shear stress elevation. Vascular occlusion totally and partially abolished the effect of physical training on BDNF levels in the hemisphere ipsilateral and contralateral to occlusion, respectively. BDNF levels were higher after high than low exercise intensity. In addition, both genetic hypertension and L-NAME treatment blunted the effects of physical training on BDNF. From these results, we propose that elevation of brain BDNF levels elicited by physical training involves changes in cerebral hemodynamics.
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169
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Ogoh S, Tsukamoto H, Hirasawa A, Hasegawa H, Hirose N, Hashimoto T. The effect of changes in cerebral blood flow on cognitive function during exercise. Physiol Rep 2014; 2:2/9/e12163. [PMID: 25263210 PMCID: PMC4270220 DOI: 10.14814/phy2.12163] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
No studies have identified the direct effect of changes in cerebral blood flow (CBF) on cognitive function at rest and during exercise. In this study, we manipulated CBF using hypercapnic gas to examine whether an increase in CBF improves cognitive function during prolonged exercise. The speed and the accuracy of cognitive function were assessed using the Stroop color-word test. After the Stroop test at rest, the subjects began exercising on a cycling ergometer in which the workload was increased by 0.5 kilopond every minute until a target heart rate of 140 beats/min was achieved. Then, the subjects continued to cycle at a constant rate for 50 min. At four time points during the exercise (0, 10, 20, 50 min), the subjects performed a Stroop test with and without hypercapnic respiratory gas (2.0% CO2), with a random order of the exposures in the two tests. Despite a decrease in the mean blood flow velocity in the middle cerebral artery (MCA Vmean), the reaction time for the Stroop test gradually decreased during the prolonged exercise without any loss of performance accuracy. In addition, the hypercapnia-induced increase in MCA Vmean produced neither changes in the reaction time nor error in the Stroop test during exercise. These findings suggest that the changes in CBF are unlikely to affect cognitive function during prolonged exercise. Thus, we conclude that improved cognitive function may be due to cerebral neural activation associated with exercise rather than global cerebral circulatory condition.
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Affiliation(s)
- Shigehiko Ogoh
- Graduate School of Engineering, Toyo University, Kawagoe-Shi, Saitama, Japan
| | - Hayato Tsukamoto
- Graduate School of Sport and Health Science, Ritsumeikan University, Shiga, Japan
| | - Ai Hirasawa
- Graduate School of Engineering, Toyo University, Kawagoe-Shi, Saitama, Japan
| | - Hiroshi Hasegawa
- Graduate School of Integrated Arts and Sciences, Hiroshima University, Hiroshima, Japan
| | | | - Takeshi Hashimoto
- Graduate School of Sport and Health Science, Ritsumeikan University, Shiga, Japan
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170
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Eom JH, Chung SH, Shim JH. The effects of squat exercises in postures for toilet use on blood flow velocity of the leg vein. J Phys Ther Sci 2014; 26:1485-7. [PMID: 25276042 PMCID: PMC4175263 DOI: 10.1589/jpts.26.1485] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Accepted: 03/31/2014] [Indexed: 11/24/2022] Open
Abstract
[Purpose] The purpose of this study was to identify the effects of squat exercises
performed in toilet-using postures on the blood flow velocity of the lower extremities for
the prevention of deep vein thrombosis. [Subjects] The subjects were 28 students who were
attending B University in Cheonan. They were divided into a group of 14 subjects of
sitting toilet users and a group of 14 subjects of squat toilet users. [Methods] The
subjects performed squat exercises in different toilet-using postures and we investigated
the changes in blood flow velocity. [Results] The variations in blood flow velocities
before and after the exercises showed significant differences in both groups but the
differences between the two groups were not significant. [Conclusion] Based on the results
of this study, we consider squat exercises are effective at improving the variation in
lower-extremity blood flow velocity when using a toilet.
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Affiliation(s)
- Jun Ho Eom
- Department of Physical Therapy, Baekseok University, Republic of Korea
| | - Sin Ho Chung
- Hanyang University Medical Center, Republic of Korea
| | - Jae Hun Shim
- Department of Physical Therapy, Baekseok University, Republic of Korea
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171
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Sørensen H, Rasmussen P, Sato K, Persson S, Olesen N, Nielsen H, Olsen N, Ogoh S, Secher N. External carotid artery flow maintains near infrared spectroscopy-determined frontal lobe oxygenation during ephedrine administration. Br J Anaesth 2014; 113:452-8. [DOI: 10.1093/bja/aet481] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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172
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Boschen KE, Hamilton GF, Delorme JE, Klintsova AY. Activity and social behavior in a complex environment in rats neonatally exposed to alcohol. Alcohol 2014; 48:533-41. [PMID: 25150044 DOI: 10.1016/j.alcohol.2014.07.005] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Environmental complexity (EC) is a powerful, stimulating paradigm that engages animals through a variety of sensory and motor pathways. Exposure to EC (30 days) following 12 days of wheel running preserves hippocampal neuroplasticity in male rats neonatally exposed to alcohol during the third-trimester equivalent (binge-like exposure on postnatal days [PD] 4-9). The current experiment investigates the importance of various components of EC (physical activity, exploration, social interaction, novelty) and examines whether neonatal alcohol exposure affects how male rats interact with their environment and other male rats. Male pups were assigned to 1 of 3 neonatal conditions from PD 4-9: suckle control (SC), sham-intubated (SI), or alcohol-exposed (AE, 5.25 g/kg/day). From PD 30-42 animals were housed with 24-h access to a voluntary running wheel. The animals were then placed in EC from PD 42-72 (9 animals/cage, counterbalanced by neonatal condition). During EC, the animals were filmed for five 30-min sessions (PD 42, 48, 56, 64, 68). For the first experiment, the videos were coded for distance traveled in the cage, overall locomotor activity, time spent near other animals, and interaction with toys. For the second experiment, the videos were analyzed for wrestling, mounting, boxing, grooming, sniffing, and crawling over/under. AE animals were found to be less active and exploratory and engaged in fewer mounting behaviors compared to control animals. Results suggest that after exposure to wheel running, AE animals still have deficits in activity and social behaviors while housed in EC compared to control animals with the same experience.
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Affiliation(s)
- Karen E Boschen
- Department of Psychological and Brain Sciences, University of Delaware, Newark, DE, USA
| | - Gillian F Hamilton
- Department of Psychological and Brain Sciences, University of Delaware, Newark, DE, USA
| | - James E Delorme
- Department of Psychological and Brain Sciences, University of Delaware, Newark, DE, USA
| | - Anna Y Klintsova
- Department of Psychological and Brain Sciences, University of Delaware, Newark, DE, USA.
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173
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Sato K, Yoneya M, Otsuki A, Sadamoto T, Ogoh S. Anatomical vertebral artery hypoplasia and insufficiency impairs dynamic blood flow regulation. Clin Physiol Funct Imaging 2014; 35:485-9. [PMID: 24980216 DOI: 10.1111/cpf.12179] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2014] [Accepted: 05/26/2014] [Indexed: 11/30/2022]
Abstract
Recent studies have suggested that vertebral artery (VA) hypoplasia is a predisposing factor for posterior cerebral stroke. We examined whether anatomical vertebrobasilar ischemia, i.e., unilateral VA hypoplasia and insufficiency, impairs dynamic blood flow regulation. Twenty-eight female subjects were divided into three groups by defined criteria: (i) unilateral VA hypoplasia (n = 8), (ii) VA insufficiency (n = 6), and (iii) control (n = 14). Hypoplastic VA criterion was VA blood flow of 40 ml min(-1) , whereas VA insufficiency criterion was net (left + right) VA blood flow of 100 ml min(-1) or less. We evaluated left, right, and net VA blood flows by ultrasonography during hypercapnia, normocapnia, and hypocapnia to evaluate VA CO2 reactivity. The unilateral VA hypoplasia group showed lower CO2 reactivity at hypoplastic VA than at non-hypoplastic VA (2.65 ± 0.58 versus 3.00 ± 0.48% per mmHg, P = 0.027) and net VA CO2 reactivity was preserved (Unilateral VA hypoplasia, 2.95 ± 0.48 versus Control, 2.93 ± 0.42% per mmHg, P = 0.992). However, the VA insufficiency group showed a lower net VA CO2 reactivity compared to the control (2.29 ± 0.55 versus 2.93 ± 0.42% per mmHg, P = 0.032) and the unilateral VA hypoplasia (P = 0.046). VA hypoplasia reduced CO2 reactivity, although non-hypoplastic VA may compensate this regulatory limitation. In subjects with VA insufficiency, lowered CO2 reactivity at the both VA could not preserve normal net VA CO2 reactivity. These findings provide a possible physiological mechanism for the increased risk of posterior cerebral stroke in subjects with VA hypoplasia and insufficiency.
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Affiliation(s)
- Kohei Sato
- Research Institute of Physical Fitness, Japan Women's College of Physical Education, Tokyo, Japan
| | - Marina Yoneya
- Research Institute of Physical Fitness, Japan Women's College of Physical Education, Tokyo, Japan
| | - Aki Otsuki
- Research Institute of Physical Fitness, Japan Women's College of Physical Education, Tokyo, Japan
| | - Tomoko Sadamoto
- Research Institute of Physical Fitness, Japan Women's College of Physical Education, Tokyo, Japan
| | - Shigehiko Ogoh
- Research Institute of Physical Fitness, Japan Women's College of Physical Education, Tokyo, Japan.,Department of Biomedical Engineering, Toyo University, Saitama, Japan
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174
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Bhambhani Y, Fan JL, Place N, Rodriguez-Falces J, Kayser B. Electromyographic, cerebral, and muscle hemodynamic responses during intermittent, isometric contractions of the biceps brachii at three submaximal intensities. Front Physiol 2014; 5:190. [PMID: 24966837 PMCID: PMC4052733 DOI: 10.3389/fphys.2014.00190] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Accepted: 04/29/2014] [Indexed: 11/25/2022] Open
Abstract
This study examined the electromyographic, cerebral and muscle hemodynamic responses during intermittent isometric contractions of biceps brachii at 20, 40, and 60% of maximal voluntary contraction (MVC). Eleven volunteers completed 2 min of intermittent isometric contractions (12/min) at an elbow angle of 90° interspersed with 3 min rest between intensities in systematic order. Surface electromyography (EMG) was recorded from the right biceps brachii and near infrared spectroscopy (NIRS) was used to simultaneously measure left prefrontal and right biceps brachii oxyhemoglobin (HbO2), deoxyhemoglobin (HHb), and total hemoglobin (Hbtot). Transcranial Doppler ultrasound was used to measure middle cerebral artery velocity (MCAv) bilaterally. Finger photoplethysmography was used to record beat-to-beat blood pressure and heart rate. EMG increased with force output from 20 to 60% MVC (P < 0.05). Cerebral HbO2 and Hbtot increased while HHb decreased during contractions with differences observed between 60% vs. 40% and 20% MVC (P < 0.05). Muscle HbO2 decreased while HHb increased during contractions with differences being observed among intensities (P < 0.05). Muscle Hbtot increased from rest at 20% MVC (P < 0.05), while no further change was observed at 40 and 60% MVC (P > 0.05). MCAv increased from rest to exercise but was not different among intensities (P > 0.05). Force output correlated with the root mean square EMG and changes in muscle HbO2 (P < 0.05), but not changes in cerebral HbO2 (P > 0.05) at all three intensities. Force output declined by 8% from the 1st to the 24th contraction only at 60% MVC and was accompanied by systematic increases in RMS, cerebral HbO2 and Hbtot with a leveling off in muscle HbO2 and Hbtot. These changes were independent of alterations in mean arterial pressure. Since cerebral blood flow and oxygenation were elevated at 60% MVC, we attribute the development of fatigue to reduced muscle oxygen availability rather than impaired central neuronal activation.
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Affiliation(s)
- Yagesh Bhambhani
- Department of Occupational Therapy, Faculty of Rehabilitation Medicine, University of Alberta Edmonton, AB, Canada
| | - Jui-Lin Fan
- Institute of Sports Sciences and Department of Physiology, Faculty of Biology and Medicine, University of Lausanne Lausanne, Switzerland ; Lemanic Neuroscience Doctoral School, University of Lausanne Lausanne, Switzerland
| | - Nicolas Place
- Institute of Sports Sciences and Department of Physiology, Faculty of Biology and Medicine, University of Lausanne Lausanne, Switzerland
| | - Javier Rodriguez-Falces
- Department of Electrical and Electronic Engineering, Public University of Navarra Pamplona, Spain
| | - Bengt Kayser
- Institute of Sports Sciences and Department of Physiology, Faculty of Biology and Medicine, University of Lausanne Lausanne, Switzerland
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175
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Trangmar SJ, Chiesa ST, Stock CG, Kalsi KK, Secher NH, González-Alonso J. Dehydration affects cerebral blood flow but not its metabolic rate for oxygen during maximal exercise in trained humans. J Physiol 2014; 592:3143-60. [PMID: 24835170 PMCID: PMC4214665 DOI: 10.1113/jphysiol.2014.272104] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Intense exercise is associated with a reduction in cerebral blood flow (CBF), but regulation of CBF during strenuous exercise in the heat with dehydration is unclear. We assessed internal (ICA) and common carotid artery (CCA) haemodynamics (indicative of CBF and extra-cranial blood flow), middle cerebral artery velocity (MCA Vmean), arterial–venous differences and blood temperature in 10 trained males during incremental cycling to exhaustion in the heat (35°C) in control, dehydrated and rehydrated states. Dehydration reduced body mass (75.8 ± 3 vs. 78.2 ± 3 kg), increased internal temperature (38.3 ± 0.1 vs. 36.8 ± 0.1°C), impaired exercise capacity (269 ± 11 vs. 336 ± 14 W), and lowered ICA and MCA Vmean by 12–23% without compromising CCA blood flow. During euhydrated incremental exercise on a separate day, however, exercise capacity and ICA, MCA Vmean and CCA dynamics were preserved. The fast decline in cerebral perfusion with dehydration was accompanied by increased O2 extraction (P < 0.05), resulting in a maintained cerebral metabolic rate for oxygen (CMRO2). In all conditions, reductions in ICA and MCA Vmean were associated with declining cerebral vascular conductance, increasing jugular venous noradrenaline, and falling arterial carbon dioxide tension () (R2 ≥ 0.41, P ≤ 0.01) whereas CCA flow and conductance were related to elevated blood temperature. In conclusion, dehydration accelerated the decline in CBF by decreasing and enhancing vasoconstrictor activity. However, the circulatory strain on the human brain during maximal exercise does not compromise CMRO2 because of compensatory increases in O2 extraction.
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Affiliation(s)
- Steven J Trangmar
- Centre for Sports Medicine and Human Performance, Brunel University, London, UK
| | - Scott T Chiesa
- Centre for Sports Medicine and Human Performance, Brunel University, London, UK
| | - Christopher G Stock
- Centre for Sports Medicine and Human Performance, Brunel University, London, UK
| | - Kameljit K Kalsi
- Centre for Sports Medicine and Human Performance, Brunel University, London, UK
| | - Niels H Secher
- Centre for Sports Medicine and Human Performance, Brunel University, London, UK Department of Anaesthesia, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
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176
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Ogoh S, Lericollais R, Hirasawa A, Sakai S, Normand H, Bailey DM. Regional redistribution of blood flow in the external and internal carotid arteries during acute hypotension. Am J Physiol Regul Integr Comp Physiol 2014; 306:R747-51. [DOI: 10.1152/ajpregu.00535.2013] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The present study examined to what extent an acute bout of hypotension influences blood flow in the external carotid artery (ECA) and the corresponding implications for blood flow regulation in the internal carotid artery (ICA). Nine healthy male participants were subjected to an abrupt decrease in arterial pressure via the thigh-cuff inflation-deflation technique. Duplex ultrasound was employed to measure beat-to-beat ECA and ICA blood flow. Compared with the baseline normotensive control, acute hypotension resulted in a heterogeneous blood flow response. ICA blood flow initially decreased following cuff release and then returned quickly to baseline levels. In contrast, the reduction in ECA blood flow persisted for 30 s following cuff release. Thus, the contribution of common carotid artery blood flow to the ECA circulation decreased during acute hypotension (−10 ± 4%, P < 0.001). This finding suggests that a preserved reduction in ECA blood flow, as well as dynamic cerebral autoregulation likely prevent a further decrease in intracranial blood flow during acute hypotension. The peripheral vasculature of the ECA may, thus, be considered an important vascular bed for intracranial cerebral blood flow regulation.
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Affiliation(s)
- Shigehiko Ogoh
- Department of Biomedical Engineering, Toyo University, Kawagoe-Shi, Saitama, Japan
| | - Romain Lericollais
- Université de Caen Basse-Normandie and Institut National de la Santé et de la Recherche Médicale, U-1075, F-14032, Caen, France; and
| | - Ai Hirasawa
- Department of Biomedical Engineering, Toyo University, Kawagoe-Shi, Saitama, Japan
| | - Sadayoshi Sakai
- Department of Biomedical Engineering, Toyo University, Kawagoe-Shi, Saitama, Japan
| | - Hervé Normand
- Université de Caen Basse-Normandie and Institut National de la Santé et de la Recherche Médicale, U-1075, F-14032, Caen, France; and
| | - Damian M. Bailey
- Neurovascular Research Laboratory, Faculty of Life Sciences and Education, University of South Wales, United Kingdom
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177
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Yamaguchi Y, Kashima H, Fukuba Y, Hayashi N. Cerebral blood flow and neurovascular coupling during static exercise. J Physiol Sci 2014; 64:195-201. [PMID: 24682807 PMCID: PMC10717924 DOI: 10.1007/s12576-014-0311-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Accepted: 03/13/2014] [Indexed: 12/30/2022]
Abstract
The effect of static exercise on neurovascular coupling (NVC) was investigated by measuring the blood flow velocity in the posterior cerebral artery (PCAv) during 2-min static handgrip exercises (HG) at 30 % of the maximum voluntary contraction in 17 healthy males. NVC was estimated as the relative change in PCAv from eye closing to a peak response to looking at a reversed checkerboard. The conductance index (CI) was calculated by dividing PCAv by the mean arterial pressure (MAP). HG significantly increased PCAv from the resting baseline, with an increase in MAP and a reduction in CI, whereas NVC did not differ significantly between the resting and HG. Compared to the resting baseline, HG significantly increased the pressor response to visual stimulation by 5.6 ± 1.1 (mean ± SE) mmHg, while the CI response was significantly inhibited by -7.0 ± 1.5 %. These results indicate that NVC was maintained during HG via contributions from both the pressor response and vasodilatation.
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Affiliation(s)
- Yuji Yamaguchi
- Graduate School of Human-Environment Studies, Kyushu University, Kasuga, Fukuoka 816-8580 Japan
| | - Hideaki Kashima
- Department of Exercise Science and Physiology, School of Health and Nutritional Sciences, Prefectural University of Hiroshima, Hiroshima, 734-8558 Japan
| | - Yoshiyuki Fukuba
- Department of Exercise Science and Physiology, School of Health and Nutritional Sciences, Prefectural University of Hiroshima, Hiroshima, 734-8558 Japan
| | - Naoyuki Hayashi
- Graduate School of Decision Science and Technology, Tokyo Insitute of Technology, Meguro, Tokyo, 152-8852 Japan
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178
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Blood flow distribution in an anatomically detailed arterial network model: criteria and algorithms. Biomech Model Mechanobiol 2014; 13:1303-30. [DOI: 10.1007/s10237-014-0574-8] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2013] [Accepted: 03/14/2014] [Indexed: 12/11/2022]
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179
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Lefferts WK, Augustine JA, Heffernan KS. Effect of acute resistance exercise on carotid artery stiffness and cerebral blood flow pulsatility. Front Physiol 2014; 5:101. [PMID: 24678301 PMCID: PMC3958641 DOI: 10.3389/fphys.2014.00101] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2014] [Accepted: 02/28/2014] [Indexed: 01/27/2023] Open
Abstract
Arterial stiffness is associated with cerebral flow pulsatility. Arterial stiffness increases following acute resistance exercise (RE). Whether this acute RE-induced vascular stiffening affects cerebral pulsatility remains unknown. Purpose: To investigate the effects of acute RE on common carotid artery (CCA) stiffness and cerebral blood flow velocity (CBFv) pulsatility. Methods: Eighteen healthy men (22 ± 1 yr; 23.7 ± 0.5 kg·m−2) underwent acute RE (5 sets, 5-RM bench press, 5 sets 10-RM bicep curls with 90 s rest intervals) or a time control condition (seated rest) in a randomized order. CCA stiffness (β-stiffness, Elastic Modulus (Ep)) and hemodynamics (pulsatility index, forward wave intensity, and reflected wave intensity) were assessed using a combination of Doppler ultrasound, wave intensity analysis and applanation tonometry at baseline and 3 times post-RE. CBFv pulsatility index was measured with transcranial Doppler at the middle cerebral artery (MCA). Results: CCA β-stiffness, Ep and CCA pulse pressure significantly increased post-RE and remained elevated throughout post-testing (p < 0.05). No changes in MCA or CCA pulsatility index were observed (p > 0.05). There were significant increases in forward wave intensity post-RE (p < 0.05) but not reflected wave intensity (p > 0.05). Conclusion: Although acute RE increases CCA stiffness and pressure pulsatility, it does not affect CCA or MCA flow pulsatility. Increases in pressure pulsatility may be due to increased forward wave intensity and not pressure from wave reflections.
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Affiliation(s)
- Wesley K Lefferts
- Department of Exercise Science, Syracuse University Syracuse, NY, USA
| | | | - Kevin S Heffernan
- Department of Exercise Science, Syracuse University Syracuse, NY, USA
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180
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Blood flow distribution during heat stress: cerebral and systemic blood flow. J Cereb Blood Flow Metab 2013; 33:1915-20. [PMID: 23942362 PMCID: PMC3851900 DOI: 10.1038/jcbfm.2013.149] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2013] [Revised: 07/24/2013] [Accepted: 07/25/2013] [Indexed: 11/08/2022]
Abstract
The purpose of the present study was to assess the effect of heat stress-induced changes in systemic circulation on intra- and extracranial blood flows and its distribution. Twelve healthy subjects with a mean age of 22±2 (s.d.) years dressed in a tube-lined suit and rested in a supine position. Cardiac output (Q), internal carotid artery (ICA), external carotid artery (ECA), and vertebral artery (VA) blood flows were measured by ultrasonography before and during whole body heating. Esophageal temperature increased from 37.0±0.2°C to 38.4±0.2°C during whole body heating. Despite an increase in Q (59±31%, P<0.001), ICA and VA decreased to 83±15% (P=0.001) and 87±8% (P=0.002), respectively, whereas ECA blood flow gradually increased from 188±72 to 422±189 mL/minute (+135%, P<0.001). These findings indicate that heat stress modified the effect of Q on blood flows at each artery; the increased Q due to heat stress was redistributed to extracranial vascular beds.
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181
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Immink RV, Pott FC, Secher NH, van Lieshout JJ. Hyperventilation, cerebral perfusion, and syncope. J Appl Physiol (1985) 2013; 116:844-51. [PMID: 24265279 DOI: 10.1152/japplphysiol.00637.2013] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This review summarizes evidence in humans for an association between hyperventilation (HV)-induced hypocapnia and a reduction in cerebral perfusion leading to syncope defined as transient loss of consciousness (TLOC). The cerebral vasculature is sensitive to changes in both the arterial carbon dioxide (PaCO2) and oxygen (PaO2) partial pressures so that hypercapnia/hypoxia increases and hypocapnia/hyperoxia reduces global cerebral blood flow. Cerebral hypoperfusion and TLOC have been associated with hypocapnia related to HV. Notwithstanding pronounced cerebrovascular effects of PaCO2 the contribution of a low PaCO2 to the early postural reduction in middle cerebral artery blood velocity is transient. HV together with postural stress does not reduce cerebral perfusion to such an extent that TLOC develops. However when HV is combined with cardiovascular stressors like cold immersion or reduced cardiac output brain perfusion becomes jeopardized. Whether, in patients with cardiovascular disease and/or defect, cerebral blood flow cerebral control HV-induced hypocapnia elicits cerebral hypoperfusion, leading to TLOC, remains to be established.
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Affiliation(s)
- R V Immink
- Laboratory for Clinical Cardiovascular Physiology, Department of Anatomy, Embryology, and Physiology, AMC Center for Heart Failure Research, Academic Medical Centre, University of Amsterdam, Amsterdam, the Netherlands
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182
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The effect of adding CO2 to hypoxic inspired gas on cerebral blood flow velocity and breathing during incremental exercise. PLoS One 2013; 8:e81130. [PMID: 24278389 PMCID: PMC3836745 DOI: 10.1371/journal.pone.0081130] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Accepted: 10/09/2013] [Indexed: 11/19/2022] Open
Abstract
Hypoxia increases the ventilatory response to exercise, which leads to hyperventilation-induced hypocapnia and subsequent reduction in cerebral blood flow (CBF). We studied the effects of adding CO2 to a hypoxic inspired gas on CBF during heavy exercise in an altitude naïve population. We hypothesized that augmented inspired CO2 and hypoxia would exert synergistic effects on increasing CBF during exercise, which would improve exercise capacity compared to hypocapnic hypoxia. We also examined the responsiveness of CO2 and O2 chemoreception on the regulation ventilation (E) during incremental exercise. We measured middle cerebral artery velocity (MCAv; index of CBF), E, end-tidal PCO2, respiratory compensation threshold (RC) and ventilatory response to exercise (E slope) in ten healthy men during incremental cycling to exhaustion in normoxia and hypoxia (FIO2 = 0.10) with and without augmenting the fraction of inspired CO2 (FICO2). During exercise in normoxia, augmenting FICO2 elevated MCAv throughout exercise and lowered both RC onset andE slope below RC (P<0.05). In hypoxia, MCAv and E slope below RC during exercise were elevated, while the onset of RC occurred at lower exercise intensity (P<0.05). Augmenting FICO2 in hypoxia increased E at RC (P<0.05) but no difference was observed in RC onset, MCAv, or E slope below RC (P>0.05). The E slope above RC was unchanged with either hypoxia or augmented FICO2 (P>0.05). We found augmenting FICO2 increased CBF during sub-maximal exercise in normoxia, but not in hypoxia, indicating that the ‘normal’ cerebrovascular response to hypercapnia is blunted during exercise in hypoxia, possibly due to an exhaustion of cerebral vasodilatory reserve. This finding may explain the lack of improvement of exercise capacity in hypoxia with augmented CO2. Our data further indicate that, during exercise below RC, chemoreception is responsive, while above RC the ventilatory response to CO2 is blunted.
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183
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Skow RJ, MacKay CM, Tymko MM, Willie CK, Smith KJ, Ainslie PN, Day TA. Differential cerebrovascular CO2 reactivity in anterior and posterior cerebral circulations. Respir Physiol Neurobiol 2013; 189:76-86. [DOI: 10.1016/j.resp.2013.05.036] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2012] [Revised: 05/30/2013] [Accepted: 05/31/2013] [Indexed: 01/08/2023]
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184
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Miyazawa T, Horiuchi M, Komine H, Sugawara J, Fadel PJ, Ogoh S. Skin blood flow influences cerebral oxygenation measured by near-infrared spectroscopy during dynamic exercise. Eur J Appl Physiol 2013; 113:2841-8. [DOI: 10.1007/s00421-013-2723-7] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2013] [Accepted: 09/03/2013] [Indexed: 10/26/2022]
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185
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Bain AR, Smith KJ, Lewis NC, Foster GE, Wildfong KW, Willie CK, Hartley GL, Cheung SS, Ainslie PN. Regional changes in brain blood flow during severe passive hyperthermia: effects of PaCO2 and extracranial blood flow. J Appl Physiol (1985) 2013; 115:653-9. [DOI: 10.1152/japplphysiol.00394.2013] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We investigated 1) the regional distribution of cerebral blood flow (CBF), 2) the influence of end-tidal Pco2 (PetCO2) on CBF, and 3) the potential for an extracranial blood “steal” from the anterior brain region during passive hyperthermia. Nineteen (13 male) volunteers underwent supine passive heating until a steady-state esophageal temperature of 2°C above resting was established. Measurements were obtained 1) during normothermia (Normo), 2) during poikilocapnic hyperthermia (Hyper), and 3) during hyperthermia with PetCO2 and end-tidal Po2 clamped to Normo levels (Hyper-clamp). Blood flow in the internal carotid (Q̇ica), vertebral (Q̇VA), and external carotid (Q̇eca) arteries (Duplex ultrasound), blood velocity of the middle cerebral (MCAv) and posterior cerebral (PCAv) arteries (transcranial Doppler), and cutaneous vascular conductance on the cheek (cheek CVC; Doppler velocimetry) were measured at each stage. During Hyper, PetCO2 was lowered by 7.0 ± 5.2 mmHg, resulting in a reduction in Q̇ica (−18 ± 17%), Q̇va (−31 ± 21%), MCAv (−22 ± 13%), and PCAv (−18 ± 10%) compared with Normo ( P < 0.05). The reduction in Q̇VA was greater than that in Q̇ICA ( P = 0.017), MCAv ( P = 0.047), and PCAv ( P = 0.034). Blood flow/velocity was completely restored in each intracranial vessel (ICA, VA, MCA, and PCA) during Hyper-clamp. Despite a ∼250% increase in Q̇ECA and a subsequent increase in cheek CVC during Hyper compared with Normo, reductions in Q̇ICA were unrelated to changes in Q̇ECA. These data provide three novel findings: 1) hyperthermia attenuates Q̇VA to a greater extent than Q̇ICA, 2) reductions in CBF during hyperthermia are governed primarily by reductions in arterial Pco2, and 3) increased Q̇ECA is unlikely to compromise Q̇ICA during hyperthermia.
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Affiliation(s)
- Anthony R. Bain
- Center for Heart, Lung, and Vascular Health, University of British Columbia, Okanagan, British Columbia, Canada
| | - Kurt J. Smith
- Center for Heart, Lung, and Vascular Health, University of British Columbia, Okanagan, British Columbia, Canada
| | - Nia C. Lewis
- Center for Heart, Lung, and Vascular Health, University of British Columbia, Okanagan, British Columbia, Canada
| | - Glen E. Foster
- Center for Heart, Lung, and Vascular Health, University of British Columbia, Okanagan, British Columbia, Canada
- School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada; and
| | - Kevin W. Wildfong
- Center for Heart, Lung, and Vascular Health, University of British Columbia, Okanagan, British Columbia, Canada
| | - Christopher K. Willie
- Center for Heart, Lung, and Vascular Health, University of British Columbia, Okanagan, British Columbia, Canada
| | - Geoffrey L. Hartley
- Department of Kinesiology, Brock University, St. Catharines, Ontario, Canada
| | - Stephen S. Cheung
- Department of Kinesiology, Brock University, St. Catharines, Ontario, Canada
| | - Philip N. Ainslie
- Center for Heart, Lung, and Vascular Health, University of British Columbia, Okanagan, British Columbia, Canada
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186
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Fan JL, Bourdillon N, Kayser B. Effect of end-tidal CO2 clamping on cerebrovascular function, oxygenation, and performance during 15-km time trial cycling in severe normobaric hypoxia: the role of cerebral O2 delivery. Physiol Rep 2013; 1:e00066. [PMID: 24303142 PMCID: PMC3835019 DOI: 10.1002/phy2.66] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2013] [Revised: 07/25/2013] [Accepted: 07/29/2013] [Indexed: 11/17/2022] Open
Abstract
During heavy exercise, hyperventilation-induced hypocapnia leads to cerebral vasoconstriction, resulting in a reduction in cerebral blood flow (CBF). A reduction in CBF would impair cerebral O2 delivery and potentially account for reduced exercise performance in hypoxia. We tested the hypothesis that end-tidal Pco2 (PETCO2) clamping in hypoxic exercise would prevent the hypocapnia-induced reduction in CBF during heavy exercise, thus improving exercise performance. We measured PETCO2, middle cerebral artery velocity (MCAv; index of CBF), prefrontal cerebral cortex oxygenation (cerebral O2Hb; index of cerebral oxygenation), cerebral O2 delivery (DO2), and leg muscle oxygenation (muscle O2Hb) in 10 healthy men (age 27 ± 7 years; VO2max 63.3 ± 6.6 mL/kg/min; mean ± SD) during simulated 15-km time trial cycling (TT) in normoxia and hypoxia (FIO2 = 0.10) with and without CO2 clamping. During exercise, hypoxia elevated MCAv and lowered cerebral O2Hb, cerebral DO2, and muscle O2Hb (P < 0.001). CO2 clamping elevated PETCO2 and MCAv during exercise in both normoxic and hypoxic conditions (P < 0.001 and P = 0.024), but had no effect on either cerebral and muscle O2Hb (P = 0.118 and P = 0.124). Nevertheless, CO2 clamping elevated cerebral DO2 during TT in both normoxic and hypoxic conditions (P < 0.001). CO2 clamping restored cerebral DO2 to normoxic values during TT in hypoxia and tended to have a greater effect on TT performance in hypoxia compared to normoxia (P = 0.097). However, post hoc analysis revealed no effect of CO2 clamping on TT performance either in normoxia (P = 0.588) or in hypoxia (P = 0.108). Our findings confirm that the hyperventilation-induced hypocapnia and the subsequent drop in cerebral oxygenation are unlikely to be the cause of the reduced endurance exercise performance in hypoxia.
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Affiliation(s)
- Jui-Lin Fan
- Institute of Sports Sciences, Faculty of Biology and Medicine, University of Lausanne Lausanne, Switzerland ; Lemanic Doctoral School of Neuroscience, University of Lausanne Lausanne, Switzerland
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187
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Shinji M. A study of the association with blood pressure difference causing body temperature ≥37·5°C and hypertension in department of primary care. Clin Physiol Funct Imaging 2013; 33:441-9. [PMID: 23711334 DOI: 10.1111/cpf.12050] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2013] [Accepted: 04/16/2013] [Indexed: 11/29/2022]
Abstract
Previous studies reported the relationship between significant blood pressure difference (ΔBP) and early atherosclerotic markers. Although it is known that body temperature is associated with BP and blood flow, as measured on Korotkoff sound graph (KSG), as well as heart rate and sympathetic nerve activity, it remains unclear whether moderate fever (≥37·5°C) can be caused by significant ΔBP. ΔBP was calculated by subtracting the BP of the left arm from that of the right arm. The aim of our study was to investigate whether an association exists among ΔBP, body temperature, hypertension and KSG area ratio in 1802 new outpatients examined in a seated position in routine clinical practice. Our study documented that absolute systolic blood pressure difference (|ΔSBP|) ≥ 10 mmHg (observed in 14·6% of the patients) was associated with a significantly higher heart rate, moderate fever, tachycardia and hypertension. In multivariate analysis, the odds ratios (ORs) of |ΔSBP| ≥ 10 mmHg showed significant associated markers of body temperature and hypertension, while the ORs of KSG area ratio ≥ 170% showed significant associated markers of sex, age, body temperature, hypertension, diabetes mellitus, prior vascular event and smoking. In conclusion, our study of new outpatients in the department of primary care demonstrated that |ΔSBP| ≥ 10 mmHg and KSG area ratio ≥ 170% were associated with moderate fever and hypertension. Furthermore, our study suggests that the association of moderate fever with |ΔSBP| ≥ 10 mmHg and KSG area ratio ≥ 170% is physiologic as well as pathologic.
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Affiliation(s)
- Maeda Shinji
- Department of Biostatistics, School of Public Health, The University of Tokyo, Tokyo, Japan; Department of General Medicine, Harasanshin Hospital, Fukuoka, Japan
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188
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Ando S, Hatamoto Y, Sudo M, Kiyonaga A, Tanaka H, Higaki Y. The effects of exercise under hypoxia on cognitive function. PLoS One 2013; 8:e63630. [PMID: 23675496 PMCID: PMC3651238 DOI: 10.1371/journal.pone.0063630] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2012] [Accepted: 04/04/2013] [Indexed: 11/18/2022] Open
Abstract
Increasing evidence suggests that cognitive function improves during a single bout of moderate exercise. In contrast, exercise under hypoxia may compromise the availability of oxygen. Given that brain function and tissue integrity are dependent on a continuous and sufficient oxygen supply, exercise under hypoxia may impair cognitive function. However, it remains unclear how exercise under hypoxia affects cognitive function. The purpose of this study was to examine the effects of exercise under different levels of hypoxia on cognitive function. Twelve participants performed a cognitive task at rest and during exercise at various fractions of inspired oxygen (FIO2: 0.209, 0.18, and 0.15). Exercise intensity corresponded to 60% of peak oxygen uptake under normoxia. The participants performed a Go/No-Go task requiring executive control. Cognitive function was evaluated using the speed of response (reaction time) and response accuracy. We monitored pulse oximetric saturation (SpO2) and cerebral oxygenation to assess oxygen availability. SpO2 and cerebral oxygenation progressively decreased during exercise as the FIO2 level decreased. Nevertheless, the reaction time in the Go-trial significantly decreased during moderate exercise. Hypoxia did not affect reaction time. Neither exercise nor difference in FIO2 level affected response accuracy. An additional experiment indicated that cognitive function was not altered without exercise. These results suggest that the improvement in cognitive function is attributable to exercise, and that hypoxia has no effects on cognitive function at least under the present experimental condition. Exercise-cognition interaction should be further investigated under various environmental and exercise conditions.
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Affiliation(s)
- Soichi Ando
- Faculty of Sports and Health Science, Fukuoka University, Fukuoka, Japan.
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189
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Querido JS, Ainslie PN, Foster GE, Henderson WR, Halliwill JR, Ayas NT, Sheel AW. Dynamic cerebral autoregulation during and following acute hypoxia: role of carbon dioxide. J Appl Physiol (1985) 2013; 114:1183-90. [DOI: 10.1152/japplphysiol.00024.2013] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Previous research has shown an inconsistent effect of hypoxia on dynamic cerebral autoregulation (dCA), which may be explained by concurrent CO2 control. To test the hypothesis that hypoxic dCA is mediated by CO2, we assessed dCA (transcranial Doppler) during and following acute normobaric isocapnic and poikilocapnic hypoxic exposures. On 2 separate days, the squat-stand maneuver was used to determine dCA in healthy subjects ( n = 8; 3 women) in isocapnic and poikilocapnic hypoxia exposures (end-tidal oxygen pressure 50 Torr for 20 min). In isocapnic hypoxia, the amplitude of the cerebral blood flow response to increases and decreases in mean arterial blood pressure were elevated (i.e., increases in gain of +35 and +28%, respectively; P < 0.05). However, dCA gain to increases in pressure was reduced compared with baseline (−32%, P < 0.05) following the isocapnic hypoxia exposure. Similarly, intravenous bolus injections of sodium nitroprusside and phenylephrine in a separate group of subjects ( n = 8; 4 women) also demonstrated a reduction in dCA gain to hypertension following isocapnic hypoxia. In contrast, dCA gain with the squat-stand maneuver did not significantly change from baseline during or following poikilocapnic hypoxia ( P > 0.05). Our results demonstrate that dCA impairment in isocapnic hypoxia can be prevented with hypocapnia, and highlight the integrated nature of hypoxic cerebrovascular control, which is under strong CO2 influence.
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Affiliation(s)
- Jordan S. Querido
- Faculty of Medicine, University of British Columbia-Vancouver, Vancouver, British Columbia, Canada
- School of Kinesiology, University of British Columbia-Vancouver, Vancouver, 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; and
| | - Glen E. Foster
- School of Kinesiology, University of British Columbia-Vancouver, Vancouver, British Columbia, Canada
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia-Okanagan, Kelowna, British Columbia, Canada; and
| | - William R. Henderson
- Faculty of Medicine, University of British Columbia-Vancouver, Vancouver, British Columbia, Canada
- School of Kinesiology, University of British Columbia-Vancouver, Vancouver, British Columbia, Canada
| | - John R. Halliwill
- Department of Human Physiology, University of Oregon, Eugene, Oregon
| | - Najib T. Ayas
- Faculty of Medicine, University of British Columbia-Vancouver, Vancouver, British Columbia, Canada
| | - A. William Sheel
- School of Kinesiology, University of British Columbia-Vancouver, Vancouver, British Columbia, Canada
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190
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Mynard JP, Steinman DA. Effect of velocity profile skewing on blood velocity and volume flow waveforms derived from maximum Doppler spectral velocity. ULTRASOUND IN MEDICINE & BIOLOGY 2013; 39:870-881. [PMID: 23453373 DOI: 10.1016/j.ultrasmedbio.2012.11.006] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2012] [Revised: 10/19/2012] [Accepted: 11/05/2012] [Indexed: 06/01/2023]
Abstract
Given evidence that fully developed axisymmetric flow may be the exception rather than the rule, even in nominally straight arteries, maximum velocity (V(max)) can lie outside the Doppler sample volume (SV). The link between V(max) and derived quantities, such as volume flow (Q), may therefore be more complex than commonly thought. We performed idealized virtual Doppler ultrasound on data from image-based computational fluid dynamics (CFD) models of the normal human carotid artery and investigated how velocity profile skewing and choice of sample volume affected V(max) waveforms and derived Q variables, considering common assumptions about velocity profile shape (i.e., Poiseuille or Womersley). Severe velocity profile skewing caused substantial errors in V(max) waveforms when using a small, centered SV, although peak V(max) was reliably detected; errors with a long SV covering the vessel diameter were orientation dependent but lower overall. Cycle-averaged Q calculated from V(max) was typically within ±15%, although substantial skewing and use of a small SV caused 10%-25% underestimation. Peak Q derived from Womersley's theory was generally accurate to within ±10%. V(max) pulsatility and resistance indexes differed from Q-based values, although the Q-based resistance index could be predicted reliably. Skewing introduced significant error into V(max)-derived Q waveforms, particularly during mid-to-late systole. Our findings suggest that errors in the V(max) and Q waveforms related to velocity profile skewing and use of a small SV, or orientation-dependent errors for a long SV, could limit their use in wave analysis or for constructing characteristic or patient-specific flow boundary conditions for model studies.
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Affiliation(s)
- Jonathan P Mynard
- Biomedical Simulation Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto, Canada
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191
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Hasegawa H, Cheung SS. Hyperthermia effects on brain function and exercise capacity. JOURNAL OF PHYSICAL FITNESS AND SPORTS MEDICINE 2013. [DOI: 10.7600/jpfsm.2.429] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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192
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Klintsova AY, Hamilton GF, Boschen KE. Long-term consequences of developmental alcohol exposure on brain structure and function: therapeutic benefits of physical activity. Brain Sci 2012; 3:1-38. [PMID: 24961305 PMCID: PMC4061829 DOI: 10.3390/brainsci3010001] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2012] [Revised: 12/01/2012] [Accepted: 12/10/2012] [Indexed: 02/07/2023] Open
Abstract
Developmental alcohol exposure both early in life and during adolescence can have a devastating impact on normal brain structure and functioning, leading to behavioral and cognitive impairments that persist throughout the lifespan. This review discusses human work as well as animal models used to investigate the effect of alcohol exposure at various time points during development, as well as specific behavioral and neuroanatomical deficits caused by alcohol exposure. Further, cellular and molecular mediators contributing to these alcohol-induced changes are examined, such as neurotrophic factors and apoptotic markers. Next, this review seeks to support the use of aerobic exercise as a potential therapeutic intervention for alcohol-related impairments. To date, few interventions, behavioral or pharmacological, have been proven effective in mitigating some alcohol-related deficits. Exercise is a simple therapy that can be used across species and also across socioeconomic status. It has a profoundly positive influence on many measures of learning and neuroplasticity; in particular, those measures damaged by alcohol exposure. This review discusses current evidence that exercise may mitigate damage caused by developmental alcohol exposure and is a promising therapeutic target for future research and intervention strategies.
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Affiliation(s)
- Anna Y Klintsova
- Department of Psychology, University of Delaware, Newark, DE 19716, USA.
| | - Gillian F Hamilton
- Department of Psychology, University of Delaware, Newark, DE 19716, USA.
| | - Karen E Boschen
- Department of Psychology, University of Delaware, Newark, DE 19716, USA.
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193
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Fisher JP, Hartwich D, Seifert T, Olesen ND, McNulty CL, Nielsen HB, van Lieshout JJ, Secher NH. Cerebral perfusion, oxygenation and metabolism during exercise in young and elderly individuals. J Physiol 2012; 591:1859-70. [PMID: 23230234 DOI: 10.1113/jphysiol.2012.244905] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
We evaluated cerebral perfusion, oxygenation and metabolism in 11 young (22 ± 1 years) and nine older (66 ± 2 years) individuals at rest and during cycling exercise at low (25% W(max)), moderate (50% Wmax), high (75% W(max)) and exhaustive (100% W(max)) workloads. Mean middle cerebral artery blood velocity (MCA V(mean)), mean arterial pressure (MAP), cardiac output (CO) and partial pressure of arterial carbon dioxide (P(aCO2)) were measured. Blood samples were obtained from the right internal jugular vein and brachial artery to determine concentration differences for oxygen (O2), glucose and lactate across the brain. The molar ratio between cerebral uptake of O2 versus carbohydrate (O2-carbohydrate index; O2/[glucose + 1/2 lactate]; OCI), the cerebral metabolic rate of O2 (CMRO2) and changes in mitochondrial O2 tension ( P(mitoO2)) were calculated. 100% W(max) was ~33% lower in the older group. Exercise increased MAP and CO in both groups (P < 0.05 vs. rest), but at each intensity MAP was higher and CO lower in the older group (P < 0.05). MCA V(mean), P(aCO2) and cerebral vascular conductance index (MCA V(mean)/MAP) were lower in the older group at each exercise intensity (P < 0.05). In contrast, young and older individuals exhibited similar increases in CMRO2 (by ~30 μmol (100 g(-1)) min(-1)), and decreases in OCI (by ~1.5) and (by ~10 mmHg) during exercise at 75% W(max). Thus, despite the older group having reduced cerebral perfusion and maximal exercise capacity, cerebral oxygenation and uptake of lactate and glucose are similar during exercise in young and older individuals.
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Affiliation(s)
- James P Fisher
- School of Sport and Exercise Sciences, College of Life and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, UK.
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194
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Ogoh S, Sato K, Nakahara H, Okazaki K, Subudhi AW, Miyamoto T. Effect of acute hypoxia on blood flow in vertebral and internal carotid arteries. Exp Physiol 2012; 98:692-8. [PMID: 23143991 DOI: 10.1113/expphysiol.2012.068015] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Hypoxia changes the regional distribution of cerebral blood flow and stimulates the ventilatory chemoreflex, thereby reducing CO2 tension. We examined the effects of both hypoxia and isocapnic hypoxia on acute changes in internal carotid (ICA) and vertebral artery (VA) blood flow. Ten healthy male subjects underwent the following two randomly assigned respiratory interventions after a resting baseline period with room air: (i) hypoxia; and (ii) isocapnic hypoxia with a controlled gas mixture (12% O2; inspiratory mmHg). In the isocapnic hypoxia intervention, subjects were instructed to maintain the rate and depth of breathing to maintain the level of end-tidal partial pressure of CO2 ( ) during the resting baseline period. The ICA and VA blood flow (velocity × cross-sectional area) were measured using Doppler ultrasonography. The was decreased (-6.3 ± 0.9%, P < 0.001) during hypoxia by hyperventilation (minute ventilation +12.9 ± 2.2%, P < 0.001), while was unchanged during isocapnic hypoxia. The ICA blood flow was unchanged (P = 0.429), while VA blood flow increased (+10.3 ± 3.1%, P = 0.010) during hypoxia. In contrast, isocapnic hypoxia increased both ICA (+14.5 ± 1.4%, P < 0.001) and VA blood flows (+10.9 ± 2.4%, P < 0.001). Thus, hypoxic vasodilatation outweighed hypocapnic vasoconstriction in the VA, but not in the ICA. These findings suggest that acute hypoxia elicits an increase in posterior cerebral blood flow, possibly to maintain essential homeostatic functions of the brainstem.
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Affiliation(s)
- Shigehiko Ogoh
- Department of Biomedical Engineering, Toyo University, 2100 Kujirai, Kawagoe-shi, Saitama 350-8585, Japan.
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195
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Sonesson B, Resch T, Dias N, Malina M. New temporary internal introducer shunt for brain perfusion during total endovascular arch replacement with in situ fenestration technique. J Vasc Surg 2012; 56:1162-5. [DOI: 10.1016/j.jvs.2012.04.064] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2012] [Revised: 03/19/2012] [Accepted: 04/19/2012] [Indexed: 10/28/2022]
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196
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Regional cerebral blood flow distribution during exercise: influence of oxygen. Respir Physiol Neurobiol 2012; 184:97-105. [PMID: 22926137 DOI: 10.1016/j.resp.2012.07.014] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2012] [Revised: 07/18/2012] [Accepted: 07/19/2012] [Indexed: 11/22/2022]
Abstract
We investigated regional changes in cerebral artery velocity during incremental exercise while breathing normoxia (21% O2), hyperoxia (100% O2) or hypoxia (16% O2) [n=10; randomized cross over design]. Middle cerebral and posterior cerebral arterial velocities (MCAv and PCAv) were measured continuously using transcranial Doppler ultrasound. At rest, only PCAv was reduced (-7%; P=0.016) with hyperoxia. During low-intensity exercise (40% workload maximum [Wmax]) MCAv (+17 cms(-1); +14cms(-1)) and PCAv (+9cms(-1); +14 cms(-1)) were increased above baseline with normoxia and hypoxia, respectively (P<0.05). The absolute increase from rest in MCAv was greater than the increase in PCAv between 40 and 80% Wmax with normoxia; this greater increase in MCAv was also evident at 60% Wmax with hypoxia and hyperoxia. Hyperoxic exercise resulted in larger absolute (+19 cms(-1)) and relative (+40%) increases in PCAv compared with normoxia. Our findings highlight the selective changes in PCAv during hyperoxic incremental exercise.
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197
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Miyazawa T, Horiuchi M, Ichikawa D, Subudhi AW, Sugawara J, Ogoh S. Face cooling with mist water increases cerebral blood flow during exercise: effect of changes in facial skin blood flow. Front Physiol 2012; 3:308. [PMID: 22934059 PMCID: PMC3429079 DOI: 10.3389/fphys.2012.00308] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2012] [Accepted: 07/13/2012] [Indexed: 11/21/2022] Open
Abstract
Facial cooling (FC) increases cerebral blood flow (CBF) at rest and during exercise; however, the mechanism of this response remains unclear. The purpose of the present study was to test our hypothesis that FC causes facial vasoconstriction that diverts skin blood flow (SkBFface) toward the middle cerebral artery (MCA Vmean) at rest and to a greater extent during exercise. Nine healthy young subjects (20 ± 2 years) underwent 3 min of FC by fanning and spraying the face with a mist of cold water (~4°C) at rest and during steady-state exercise [heart rate (HR) of 120 bpm]. We focused on the difference between the averaged data acquired from 1 min immediately before FC and last 1 min of FC. SkBFface, MCA Vmean, and mean arterial blood pressure (MAP) were higher during exercise than at rest. As hypothesized, FC decreased SkBFface at rest (−32 ± 4%) and to a greater extent during exercise (−64 ± 10%, P = 0.012). Although MCA Vmean was increased by FC (Rest, +1.4 ± 0.5 cm/s; Exercise, +1.4 ± 0.6 cm/s), the amount of the FC-evoked changes in MCA Vmean at rest and during exercise differed among subjects. In addition, changes in MCA Vmean with FC did not correlate with concomitant changes in SkBFface (r = 0.095, P = 0.709). MAP was also increased by FC (Rest, +6.2 ± 1.4 mmHg; Exercise, +4.2 ± 1.2 mmHg). These findings suggest that the FC-induced increase in CBF during exercise could not be explained only by change in SkBFface.
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Affiliation(s)
- Taiki Miyazawa
- Center for Biomedical Engineering Research, Toyo University Kawagoe, Japan
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198
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Sato K, Fisher JP, Seifert T, Overgaard M, Secher NH, Ogoh S. Blood flow in internal carotid and vertebral arteries during orthostatic stress. Exp Physiol 2012; 97:1272-80. [DOI: 10.1113/expphysiol.2012.064774] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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199
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Ishii K, Liang N, Oue A, Hirasawa A, Sato K, Sadamoto T, Matsukawa K. Central command contributes to increased blood flow in the noncontracting muscle at the start of one-legged dynamic exercise in humans. J Appl Physiol (1985) 2012; 112:1961-74. [DOI: 10.1152/japplphysiol.00075.2012] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Whether neurogenic vasodilatation contributes to exercise hyperemia is still controversial. Blood flow to noncontracting muscle, however, is chiefly regulated by a neural mechanism. Although vasodilatation in the nonexercising limb was shown at the onset of exercise, it was unclear whether central command or muscle mechanoreflex is responsible for the vasodilatation. To clarify this, using voluntary one-legged cycling with the right leg in humans, we measured the relative changes in concentrations of oxygenated-hemoglobin (Oxy-Hb) of the noncontracting vastus lateralis (VL) muscle with near-infrared spectroscopy as an index of tissue blood flow and femoral blood flow to the nonexercising leg. Oxy-Hb in the noncontracting VL and femoral blood flow increased ( P < 0.05) at the start period of voluntary one-legged cycling without accompanying a rise in arterial blood pressure. In contrast, no increases in Oxy-Hb and femoral blood flow were detected at the start period of passive one-legged cycling, suggesting that muscle mechanoreflex cannot explain the initial vasodilatation of the noncontracting muscle during voluntary one-legged cycling. Motor imagery of the voluntary one-legged cycling increased Oxy-Hb of not only the right but also the left VL. Furthermore, an increase in Oxy-Hb of the contracting VL, which was observed at the start period of voluntary one-legged cycling, had the same time course and magnitude as the increase in Oxy-Hb of the noncontracting muscle. Thus it is concluded that the centrally induced vasodilator signal is equally transmitted to the bilateral VL muscles, not only during imagery of exercise but also at the start period of voluntary exercise in humans.
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Affiliation(s)
- Kei Ishii
- Department of Physiology, Graduate School of Health Sciences, Hiroshima University, Hiroshima, Japan; and
| | - Nan Liang
- Department of Physiology, Graduate School of Health Sciences, Hiroshima University, Hiroshima, Japan; and
| | - Anna Oue
- Research Institute of Physical Fitness, Japan Women's College of Physical Education, Tokyo, Japan
| | - Ai Hirasawa
- Research Institute of Physical Fitness, Japan Women's College of Physical Education, Tokyo, Japan
| | - Kohei Sato
- Research Institute of Physical Fitness, Japan Women's College of Physical Education, Tokyo, Japan
| | - Tomoko Sadamoto
- Research Institute of Physical Fitness, Japan Women's College of Physical Education, Tokyo, Japan
| | - Kanji Matsukawa
- Department of Physiology, Graduate School of Health Sciences, Hiroshima University, Hiroshima, Japan; and
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Sato K, Sadamoto T, Hirasawa A, Oue A, Subudhi AW, Miyazawa T, Ogoh S. Differential blood flow responses to CO₂ in human internal and external carotid and vertebral arteries. J Physiol 2012; 590:3277-90. [PMID: 22526884 DOI: 10.1113/jphysiol.2012.230425] [Citation(s) in RCA: 151] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Arterial CO2 serves as a mediator of cerebral blood flow(CBF), and its relative influence on the regulation of CBF is defined as cerebral CO2 reactivity. Our previous studies have demonstrated that there are differences in CBF responses to physiological stimuli (i.e. dynamic exercise and orthostatic stress) between arteries in humans. These findings suggest that dynamic CBF regulation and cerebral CO2 reactivity may be different in the anterior and posterior cerebral circulation. The aim of this study was to identify cerebral CO2 reactivity by measuring blood flow and examine potential differences in CO2 reactivity between the internal carotid artery (ICA), external carotid artery (ECA) and vertebral artery (VA). In 10 healthy young subjects, we evaluated the ICA, ECA, and VA blood flow responses by duplex ultrasonography (Vivid-e, GE Healthcare), and mean blood flow velocity in middle cerebral artery (MCA) and basilar artery (BA) by transcranial Doppler (Vivid-7, GE healthcare) during two levels of hypercapnia (3% and 6% CO2), normocapnia and hypocapnia to estimate CO2 reactivity. To characterize cerebrovascular reactivity to CO2,we used both exponential and linear regression analysis between CBF and estimated partial pressure of arterial CO2, calculated by end-tidal partial pressure of CO2. CO2 reactivity in VA was significantly lower than in ICA (coefficient of exponential regression 0.021 ± 0.008 vs. 0.030 ± 0.008; slope of linear regression 2.11 ± 0.84 vs. 3.18 ± 1.09% mmHg−1: VA vs. ICA, P <0.01). Lower CO2 reactivity in the posterior cerebral circulation was persistent in distal intracranial arteries (exponent 0.023 ± 0.006 vs. 0.037 ± 0.009; linear 2.29 ± 0.56 vs. 3.31 ± 0.87% mmHg−1: BA vs. MCA). In contrast, CO2 reactivity in ECA was markedly lower than in the intra-cerebral circulation (exponent 0.006 ± 0.007; linear 0.63 ± 0.64% mmHg−1, P <0.01). These findings indicate that vertebro-basilar circulation has lower CO2 reactivity than internal carotid circulation, and that CO2 reactivity of the external carotid circulation is markedly diminished compared to that of the cerebral circulation, which may explain different CBF responses to physiological stress.
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Affiliation(s)
- Kohei Sato
- Research Institute of Physical Fitness, Japan Women's College of Physical Education, Kita-Karasuyama, Setagaya-ku, Tokyo 157-8565, Japan.
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