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Weijs RW, Oudegeest-Sander MH, Hopman MT, Thijssen DH, Claassen JA. Cerebrovascular CO 2 reactivity and dynamic cerebral autoregulation through the eighth decade of life and their implications for cognitive decline. J Cereb Blood Flow Metab 2024; 44:712-725. [PMID: 38064286 DOI: 10.1177/0271678x231219568] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 04/26/2024]
Abstract
Aging is accompanied by a decrease in cerebral blood flow (CBF), especially in the presence of preclinical cognitive decline. The role of cerebrovascular physiology including regulatory mechanisms of CBF in processes underlying aging and subclinical cognitive decline is, however, not fully understood. We explored changes in cerebrovascular CO2 reactivity and dynamic cerebral autoregulation (dCA) through the eighth decade of life, and their relation with early cognitive decline. After 10.9 years, twenty-eight (age, 80.0 ± 3.5 years; 46% female) out of forty-eight healthy older adults who had participated in a previous study (age at baseline, 70 ± 4 years; 42% female), underwent repeated transcranial Doppler assessments. Linear mixed-model analyses revealed small reductions in cerebrovascular CO2 reactivity with aging (-0.37%/mmHg, P = 0.041), whereas dCA was modestly enhanced (gain: -0.009 cm/s/mmHg, P = 0.038; phase: +8.9 degrees, P = 0.004). These changes were more pronounced in participants who had developed subjective memory complaints at follow-up. Our observations confirm that dCA is not impaired in aging, despite lower cerebral perfusion and cerebrovascular reactivity. Altogether, this unique longitudinal study highlights the involvement of cerebrovascular health in preclinical cognitive decline, which is of clinical relevance in the development of dementia management strategies.
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Affiliation(s)
- Ralf Wj Weijs
- Department of Medical BioSciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Madelijn H Oudegeest-Sander
- Department of Medical BioSciences, Radboud University Medical Center, Nijmegen, The Netherlands
- Department of Geriatric Medicine, Radboudumc Alzheimer Center, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Maria Te Hopman
- Department of Medical BioSciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Dick Hj Thijssen
- Department of Medical BioSciences, Radboud University Medical Center, Nijmegen, The Netherlands
- Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, UK
| | - Jurgen Ahr Claassen
- Department of Geriatric Medicine, Radboudumc Alzheimer Center, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
- Department of Cardiovascular Sciences, University of Leicester, Leicester, UK
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Douglas AJM, Talbot JS, Perkins D, Dawkins TG, Oliver JL, Lloyd RS, Ainslie PN, McManus A, Pugh CJA, Lord RN, Stembridge M. The influence of maturation and sex on intracranial blood velocities during exercise in children. J Appl Physiol (1985) 2024; 136:451-459. [PMID: 38126090 DOI: 10.1152/japplphysiol.00478.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Accepted: 12/15/2023] [Indexed: 12/23/2023] Open
Abstract
Cerebral blood velocity (CBv) increases in response to moderate exercise in humans, but the magnitude of change is smaller in children compared with postpubertal adolescents and adults. Whether sex differences exist in the anterior or posterior CBv response to exercise across pubertal development remains to be determined. We assessed middle cerebral artery (MCAv) and posterior cerebral artery (PCAv) blood velocity via transcranial Doppler in 38 prepubertal (18 males) and 48 postpubertal (23 males) with cerebrovascular and cardiorespiratory measures compared at baseline and ventilatory threshold. At baseline, MCAv was higher in both sexes pre- versus postpuberty. Females demonstrated a greater MCAv (P < 0.001) than their male counterparts (prepubertal females; 78 ± 11 cm·s-1 vs. prepubertal males; 72 ± 8 cm·s-1, and postpubertal females; 68 ± 10 cm·s-1 vs. postpubertal males; 62 ± 7 cm·s-1). During exercise, MCAv remained higher in postpubertal females versus males (81 ± 15 cm·s-1 vs. 73 ± 11 cm·s-1), but there were no differences in prepuberty. The relative increase in PCAv was greater in post- versus prepubertal females (51 ± 9 cm·s-1 vs. 45 ± 11 cm·s-1; P = 0.032) but was similar in males and females. Our findings suggest that biological sex alters anterior cerebral blood velocities at rest in both pre- and postpubertal youth, but the response to submaximal exercise is only influenced by sex postpuberty.NEW & NOTEWORTHY Cerebral blood velocity (CBv) in the anterior circulation was higher in females compared with males irrespective of maturational stage, but not in the posterior circulation. In response to exercise, females demonstrated a greater CBv compared with males, especially post-peak height velocity (post-PHV) where the CBv response to exercise was more pronounced. Our findings suggest that both CBv at rest and in response to acute submaximal exercise are altered by biological sex in a maturity-dependent manner.
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Affiliation(s)
- Andrew J M Douglas
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, United Kingdom
- Centre for Health, Activity and Wellbeing Research, Cardiff Metropolitan University, Cardiff, United Kingdom
| | - Jack S Talbot
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, United Kingdom
- Centre for Health, Activity and Wellbeing Research, Cardiff Metropolitan University, Cardiff, United Kingdom
| | - Dean Perkins
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, United Kingdom
- Department of Sport Science, University of Innsbruck, Innsbruck, Austria
| | - Tony G Dawkins
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, United Kingdom
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada
| | - Jon L Oliver
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, United Kingdom
- Youth Physical Development Centre, Cardiff Metropolitan University, Cardiff, United Kingdom
- Sports Performance Research Institute New Zealandy, AUT University, Auckland, New Zealand
| | - Rhodri S Lloyd
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, United Kingdom
- Youth Physical Development Centre, Cardiff Metropolitan University, Cardiff, United Kingdom
- Sports Performance Research Institute New Zealandy, AUT University, Auckland, New Zealand
- Centre for Sport Science and Human Performance, Waikato Institute of Technology, Waikato, New Zealand
| | - Philip N Ainslie
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada
| | - Ali McManus
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada
| | - Christopher J A Pugh
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, United Kingdom
- Centre for Health, Activity and Wellbeing Research, Cardiff Metropolitan University, Cardiff, United Kingdom
| | - Rachel N Lord
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, United Kingdom
- Centre for Health, Activity and Wellbeing Research, Cardiff Metropolitan University, Cardiff, United Kingdom
| | - Mike Stembridge
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, United Kingdom
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O'Brien NF, Chetcuti K, Fonseca Y, Vidal L, Raghavan P, Postels DG, Chimalizeni Y, Ray S, Seydel KB, Taylor TE. Cerebral Metabolic Crisis in Pediatric Cerebral Malaria. J Pediatr Intensive Care 2023; 12:278-288. [PMID: 37970136 PMCID: PMC10631841 DOI: 10.1055/s-0041-1732444] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Accepted: 06/12/2021] [Indexed: 10/20/2022] Open
Abstract
Cerebral metabolic energy crisis (CMEC), often defined as a cerebrospinal fluid (CSF) lactate: pyruvate ratio (LPR) >40, occurs in various diseases and is associated with poor neurologic outcomes. Cerebral malaria (CM) causes significant mortality and neurodisability in children worldwide. Multiple factors that could lead to CMEC are plausible in these patients, but its frequency has not been explored. Fifty-three children with CM were enrolled and underwent analysis of CSF lactate and pyruvate levels. All 53 patients met criteria for a CMEC (median CSF LPR of 72.9 [interquartile range [IQR]: 58.5-93.3]). Half of children met criteria for an ischemic CMEC (median LPR of 85 [IQR: 73-184]) and half met criteria for a nonischemic CMEC (median LPR of 60 [IQR: 54-79]. Children also underwent transcranial doppler ultrasound investigation. Cerebral blood flow velocities were more likely to meet diagnostic criteria for low flow (<2 standard deviation from normal) or vasospasm in children with an ischemic CMEC (73%) than in children with a nonischemic CMEC (20%, p = 0.04). Children with an ischemic CMEC had poorer outcomes (pediatric cerebral performance category of 3-6) than those with a nonischemic CMEC (46 vs. 22%, p = 0.03). CMEC was ubiquitous in this patient population and the processes underlying the two subtypes (ischemic and nonischemic) may represent targets for future adjunctive therapies.
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Affiliation(s)
- Nicole F. O'Brien
- Division of Critical Care Medicine, Department of Pediatrics, Nationwide Children's Hospital, The Ohio State University, Columbus, Ohio, United States
| | - Karen Chetcuti
- Department of Radiology, College of Medicine, Chichiri, Blantyre, Malawi
| | - Yudy Fonseca
- Division of Critical Care Medicine, Department of Pediatrics, University of Maryland Medical Center, University of Maryland School of Medicine, Baltimore, Maryland, United States
| | - Lorenna Vidal
- Division of Neuroradiology, Department of Radiology Children's Hospital of Philadelphia, Clinical Instructor at Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States
| | - Prashant Raghavan
- Department of Diagnostic Radiology and Nuclear Medicine, University of Maryland School of Medicine, Baltimore, Maryland, United States
| | - Douglas G. Postels
- Department of Neurology, George Washington University/Children's National Medical Center, Washington, District of Columbia, United States
| | - Yamikani Chimalizeni
- Department of Pediatrics and Child Health, University of Malawi, Malawi College of Medicine, Chichiri, Blantyre, Malawi
| | - Stephen Ray
- Department of Paediatric, Malawi Liverpool Wellcome Trust Clinical Research Programme, Blantyre, Malawi
| | - Karl B. Seydel
- Department of Osteopathic Medical Specialties, College of Osteopathic Medicine, Michigan State University, East Lansing, Michigan, United States
- Blantyre Malaria Project, Blantyre, Malawi
| | - Terrie E. Taylor
- Department of Osteopathic Medical Specialties, College of Osteopathic Medicine, Michigan State University, East Lansing, Michigan, United States
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Aframian K, Yousef Yengej D, Nwaobi S, Raman S, Faas GC, Charles A. Effects of chronic caffeine on patterns of brain blood flow and behavior throughout the sleep-wake cycle in freely behaving mice. PNAS Nexus 2023; 2:pgad303. [PMID: 37780231 PMCID: PMC10538474 DOI: 10.1093/pnasnexus/pgad303] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Accepted: 09/05/2023] [Indexed: 10/03/2023]
Abstract
Caffeine has significant effects on neurovascular activity and behavior throughout the sleep-wake cycle. We used a minimally invasive microchip/video system to continuously record effects of caffeine in the drinking water of freely behaving mice. Chronic caffeine shifted both rest and active phases by up to 2 h relative to the light-dark cycle in a dose-dependent fashion. There was a particular delay in the onset of rapid eye movement (REM) sleep as compared with non-REM sleep during the rest phase. Chronic caffeine increased wakefulness during the active phase and consolidated sleep during the rest phase; overall, there was no net change in the amount of time spent in the wake, sleep, or REM sleep states during caffeine administration. Despite these effects on wakefulness and sleep, chronic caffeine decreased mean cerebral blood volume (CBV) during the active phase and increased mean CBV during the rest phase. Chronic caffeine also increased heart rate variability in both the sleep and wake states. These results provide new insight into the effects of caffeine on the biology of the sleep-wake cycle. Increased blood flow during sleep caused by chronic caffeine may have implications for its potential neuroprotective effects through vascular mechanisms of brain waste clearance.
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Affiliation(s)
- Kimiya Aframian
- Department of Neurology, David Geffen School of Medicine at UCLA, 635 Charles Young Drive, Los Angeles, CA 90095, USA
| | - Dmitri Yousef Yengej
- Department of Neurology, David Geffen School of Medicine at UCLA, 635 Charles Young Drive, Los Angeles, CA 90095, USA
| | - Sinifunanya Nwaobi
- Department of Neurology, David Geffen School of Medicine at UCLA, 635 Charles Young Drive, Los Angeles, CA 90095, USA
| | - Shrayes Raman
- Department of Neurology, David Geffen School of Medicine at UCLA, 635 Charles Young Drive, Los Angeles, CA 90095, USA
| | - Guido C Faas
- Department of Neurology, David Geffen School of Medicine at UCLA, 635 Charles Young Drive, Los Angeles, CA 90095, USA
| | - Andrew Charles
- Department of Neurology, David Geffen School of Medicine at UCLA, 635 Charles Young Drive, Los Angeles, CA 90095, USA
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Akins JD, Brothers RM. Unlocking the complications of chronic concussion in rugby players: A traumatic tale of cerebral injury. Exp Physiol 2023; 108:1106-1107. [PMID: 37551823 PMCID: PMC10988438 DOI: 10.1113/ep091352] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2023] [Accepted: 07/19/2023] [Indexed: 08/09/2023]
Affiliation(s)
- John D. Akins
- Institute for Exercise and Environmental Medicine at Texas Health Presbyterian Hospital DallasDallasTXUSA
- The University of Texas Southwestern Medical CenterDallasTXUSA
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Ogoh S, Watanabe H, Saito S, Fisher JP, Iwamoto E. Can Alterations in Cerebrovascular CO 2 Reactivity Be Identified Using Transfer Function Analysis without the Requirement for Carbon Dioxide Inhalation? J Clin Med 2023; 12:jcm12062441. [PMID: 36983441 PMCID: PMC10051076 DOI: 10.3390/jcm12062441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Revised: 03/09/2023] [Accepted: 03/21/2023] [Indexed: 03/30/2023] Open
Abstract
The present study aimed to examine the validity of a novel method to assess cerebrovascular carbon dioxide (CO2) reactivity (CVR) that does not require a CO2 inhalation challenge, e.g., for use in patients with respiratory disease or the elderly, etc. In twenty-one healthy participants, CVR responses to orthostatic stress (50° head-up tilt, HUT) were assessed using two methods: (1) the traditional CO2 inhalation method, and (2) transfer function analysis (TFA) between middle cerebral artery blood velocity (MCA V) and predicted arterial partial pressure of CO2 (PaCO2) during spontaneous respiration. During HUT, MCA V steady-state (i.e., magnitude) and MCA V onset (i.e., time constant) responses to CO2 inhalation were decreased (p < 0.001) and increased (p = 0.001), respectively, indicative of attenuated CVR. In contrast, TFA gain in the very low-frequency range (VLF, 0.005-0.024 Hz) was unchanged, while the TFA phase in the VLF approached zero during HUT (-0.38 ± 0.59 vs. 0.31 ± 0.78 radians, supine vs. HUT; p = 0.003), indicative of a shorter time (i.e., improved) response of CVR. These findings indicate that CVR metrics determined by TFA without a CO2 inhalation do not track HUT-evoked reductions in CVR identified using CO2 inhalation, suggesting that enhanced cerebral blood flow response to a change in CO2 using CO2 inhalation is necessary to assess CVR adequately.
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Affiliation(s)
- Shigehiko Ogoh
- Department of Biomedical Engineering, Toyo University, Kawagoe 350-8585, Japan
- Neurovascular Research Laboratory, University of South Wales, Pontypridd CF37 1DL, UK
| | - Hironori Watanabe
- Department of Biomedical Engineering, Toyo University, Kawagoe 350-8585, Japan
| | - Shotaro Saito
- Department of Biomedical Engineering, Toyo University, Kawagoe 350-8585, Japan
| | - James P Fisher
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Auckland 1023, New Zealand
| | - Erika Iwamoto
- School of Health Sciences, Sapporo Medical University, Sapporo 060-8556, Japan
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Abstract
A minimal model of cerebral blood flow and respiratory control was developed to describe hypocapnic and hypercapnic responses. Important nonlinear properties such as cerebral blood flow changes with arterial partial pressure of carbon dioxide ([Formula: see text]) and associated time-dependent circulatory time delays were included. It was also necessary to vary cerebral metabolic rate as a function of [Formula: see text]. The cerebral blood flow model was added to a previously developed respiratory control model to simulate central and peripheral controller dynamics for humans. Model validation was based on previously collected data. The variable time delay due to brain blood flow changes in hypercapnia was an important determinant of predicted instability due to nonlinear interaction in addition to linear loop gain considerations. Peripheral chemoreceptor gains above a critical level, but within normal limits, were necessary to produce instability. Instability was observed in recovery from hypercapnia and hypocapnia. The 20-s breath-hold test appears to be a simple test of brain blood flow-mediated instability in hypercapnia. Brain blood flow was predicted to play an important role with nonlinear properties. There is an important interaction predicted by the current model between central and peripheral control mechanisms related to instability in hypercapnia recovery. Posthyperventilation breathing pattern can also reveal instability tied to brain blood flow. Previous data collected in patients with chronic obstructive lung disease were closely fitted with the current model and instability predicted. Brain vascular volume was proposed as a potential cause of instability despite cerebral autoregulation promoting constant brain flow.NEW & NOTEWORTHY Prior models of brain blood flow and respiratory control have not focused on instability. Time varying time delay resulting from brain blood flow changes due to carbon dioxide (CO2) and peripheral chemoreceptor gain were predicted to be important determinants of instability due to nonlinear interaction in addition to linear control loop gain. Time delay was assumed to be set by the ratio of brain arterial vascular volume and blood flow. This vascular volume was predicted to also significantly change with CO2.
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Affiliation(s)
- Stanley M Yamashiro
- Biomedical Engineering Department, University of Southern California, Los Angeles, California
| | - Takahide Kato
- Department of General Education, National Institute of Technology, Toyota College, Toyota, Japan
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Ruediger SL, Koep JL, Keating SE, Pizzey FK, Coombes JS, Bailey TG. Effect of menopause on cerebral artery blood flow velocity and cerebrovascular reactivity: Systematic review and meta-analysis. Maturitas 2021; 148:24-32. [PMID: 34024348 DOI: 10.1016/j.maturitas.2021.04.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 03/28/2021] [Accepted: 04/11/2021] [Indexed: 12/31/2022]
Abstract
BACKGROUND Menopause and its associated decline in oestrogen is linked to chronic conditions like cardiovascular disease and osteoporosis, which may be difficult to disentangle from the effects of ageing. Further, post-menopausal women are at increased risk of cerebrovascular disease, linked to declines in cerebral blood flow (CBF) and cerebrovascular reactivity (CVR), yet the direct understanding of the impact of the menopause on cerebrovascular function is unclear. The aim of this systematic review and meta-analysis was to examine the literature investigating CBF and CVR in pre- compared with post-menopausal women METHODS: Five databases were searched for studies assessing CBF or CVR in pre- and post-menopausal women. Meta-analysis examined the effect of menopausal status on middle cerebral artery velocity (MCAv), and GRADE-assessed evidence certainty RESULTS: Nine studies (n=504) included cerebrovascular outcomes. Six studies (n=239) reported negligible differences in MCAv between pre- and post-menopausal women [2.11cm/s (95% CI: -8.94 to 4.73, p=0.54)], but with a "low" certainty of evidence. MCAv was lower in post-menopausal women in two studies, when MCAv was adjusted for blood pressure. CVR was lower in post- compared with pre-menopausal women in two of three studies, but high-quality evidence is lacking. Across outcomes, study methodology and reporting criteria for menopause were inconsistent CONCLUSIONS: MCAv was similar in post- compared with pre-menopausal women. Methodological differences in characterising menopause and inconsistent reporting of cerebrovascular outcomes make comparisons difficult. Comprehensive assessments of cerebrovascular function of the intra- and extracranial arteries to determine the physiological implications of menopause on CBF with healthy ageing is warranted.
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Affiliation(s)
- Stefanie L Ruediger
- Physiology and Ultrasound Laboratory in Science and Exercise, Centre for Research on Exercise, Physical Activity and Health; School of Human Movement and Nutrition Sciences, The University of Queensland, Brisbane, QLD, Australia
| | - Jodie L Koep
- Physiology and Ultrasound Laboratory in Science and Exercise, Centre for Research on Exercise, Physical Activity and Health; School of Human Movement and Nutrition Sciences, The University of Queensland, Brisbane, QLD, Australia; Children's Health and Exercise Research Centre, Sport and Health Sciences, College of Life and Environmental Sciences, University of Exeter, Exeter, UK
| | - Shelley E Keating
- Physiology and Ultrasound Laboratory in Science and Exercise, Centre for Research on Exercise, Physical Activity and Health; School of Human Movement and Nutrition Sciences, The University of Queensland, Brisbane, QLD, Australia
| | - Faith K Pizzey
- Physiology and Ultrasound Laboratory in Science and Exercise, Centre for Research on Exercise, Physical Activity and Health; School of Human Movement and Nutrition Sciences, The University of Queensland, Brisbane, QLD, Australia
| | - Jeff S Coombes
- Physiology and Ultrasound Laboratory in Science and Exercise, Centre for Research on Exercise, Physical Activity and Health; School of Human Movement and Nutrition Sciences, The University of Queensland, Brisbane, QLD, Australia
| | - Tom G Bailey
- Physiology and Ultrasound Laboratory in Science and Exercise, Centre for Research on Exercise, Physical Activity and Health; School of Human Movement and Nutrition Sciences, The University of Queensland, Brisbane, QLD, Australia; School of Nursing, Midwifery and Social Work, The University of Queensland, Brisbane, QLD, Australia
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Tibballs J, Bhatia N. New Challenges to the Legal Definition and Medical Determination of Brain Death: A Multi-jurisdictional Approach - Cases from the United States, the United Kingdom, Canada and Australia. J Law Med 2021; 28:831-854. [PMID: 34369133] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Legal definitions of death and its medical determination have been challenged in high-profile cases in several jurisdictions which define death as either cessation of all functions of the brain or only of the brain stem. Several patients diagnosed brain dead have recovered some vestigial brain activity. Plaintiffs, seeking to prevent withdrawal of life-sustaining treatment, have sought to prevent performance of the key test, the apnoeic-oxygenation test, because it can cause harm and as a medical procedure requires informed consent. Reform of the American Uniform Determination of Death Act, which resembles Australian legislation, has been proposed to include specification of the medical determination of death and lack of requirement of consent to conduct testing. In this article we consider cases and proposals for law reform, concluding that the Australian definition of brain death ought to be retained but that the apnoeic-oxygenation test should be abandoned in lieu of testing brain blood flow and that religious accommodation should be considered.
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Affiliation(s)
- James Tibballs
- Associate Professor, Paediatric Intensive Care Unit, Royal Children's Hospital Melbourne and Departments of Paediatrics and of Pharmacology, University of Melbourne
| | - Neera Bhatia
- Associate Professor, School of Law, Faculty of Business and Law, Deakin University, Burwood
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Ashley JD, Shelley JH, Sun J, Song J, Trent JA, Ambrosio LD, Larson DJ, Larson RD, Yabluchanskiy A, Kellawan JM. Cerebrovascular responses to graded exercise in young healthy males and females. Physiol Rep 2020; 8:e14622. [PMID: 33112497 PMCID: PMC7592493 DOI: 10.14814/phy2.14622] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2020] [Accepted: 10/04/2020] [Indexed: 01/06/2023] Open
Abstract
Although systemic sex-specific differences in cardiovascular responses to exercise are well established, the comparison of sex-specific cerebrovascular responses to exercise has gone under-investigated especially, during high intensity exercise. Therefore, our purpose was to compare cerebrovascular responses in males and females throughout a graded exercise test (GXT). Twenty-six participants (13 Females and 13 Males, 24 ± 4 yrs.) completed a GXT on a recumbent cycle ergometer consisting of 3-min stages. Each sex completed 50W, 75W, 100W stages. Thereafter, power output increased 30W/stage for females and 40W/stage for males until participants were unable to maintain 60-80 RPM. The final stage completed by the participant was considered maximum workload(Wmax ). Respiratory gases (End-tidal CO2 , EtCO2 ), middle cerebral artery blood velocity (MCAv), heart rate (HR), non-invasive mean arterial pressure (MAP), cardiac output (CO), and stroke volume (SV) were continuously recorded on a breath-by-breath or beat-by-beat basis. Cerebral perfusion pressure, CPP = MAP (0. 7,355 distance from heart-level to doppler probe) and cerebral vascular conductance index, CVCi = MCAv/CPP 100mmHg were calculated. The change from baseline (Δ) in MCAv was similar between the sexes during the GXT (p = .091, ωp2 = 0.05). However, ΔCPP (p < .001, ωp2 = 0.25) was greater in males at intensities ≥ 80% Wmax and ΔCVCi (p = .005, ωp2 = 0.15) was greater in females at 100% Wmax . Δ End-tidal CO2 (ΔEtCO2 ) was not different between the sexes during exercise (p = .606, ωp2 = -0.03). These data suggest there are sex-specific differences in cerebrovascular control, and these differences may only be identifiable at high and severe intensity exercise.
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Affiliation(s)
- John D. Ashley
- Department of Health and Exercise ScienceHuman Circulation Research LaboratoryUniversity of OklahomaNormanOKUSA
| | - Joe H. Shelley
- Department of Health and Exercise ScienceHuman Circulation Research LaboratoryUniversity of OklahomaNormanOKUSA
| | - Jongjoo Sun
- Department of Health and Exercise ScienceHuman Circulation Research LaboratoryUniversity of OklahomaNormanOKUSA
| | - Jiwon Song
- Department of Health and Exercise ScienceHuman Circulation Research LaboratoryUniversity of OklahomaNormanOKUSA
| | - Jacob A. Trent
- Department of Health and Exercise ScienceHuman Circulation Research LaboratoryUniversity of OklahomaNormanOKUSA
| | - Luis D. Ambrosio
- Department of Health and Exercise ScienceHuman Circulation Research LaboratoryUniversity of OklahomaNormanOKUSA
| | - Daniel J. Larson
- Department of Health and Exercise Science, Sport, Health, and Exercise Data Analytics LaboratoryUniversity of OklahomaNormanOKUSA
| | - Rebecca D. Larson
- Department of Health and Exercise ScienceBody Composition and Physical Performance Research LaboratoryUniversity of OklahomaNormanOKUSA
| | - Andriy Yabluchanskiy
- Oklahoma Center for GeroscienceDepartment of Biochemistry and Molecular BiologyUniversity of Oklahoma Health Sciences CenterOklahoma CityOKUSA
| | - J. Mikhail Kellawan
- Department of Health and Exercise ScienceHuman Circulation Research LaboratoryUniversity of OklahomaNormanOKUSA
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11
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Abstract
Patients with chronic kidney disease (CKD) and end-stage kidney disease (ESKD) experience an increased risk of cerebrovascular disease and cognitive dysfunction. Hemodialysis (HD), a major modality of renal replacement therapy in ESKD, can cause rapid changes in blood pressure, osmolality, and acid-base balance that collectively present a unique stress to the cerebral vasculature. This review presents an update regarding cerebral blood flow (CBF) regulation in CKD and ESKD and how the maintenance of cerebral oxygenation may be compromised during HD. Patients with ESKD exhibit decreased cerebral oxygen delivery due to anemia, despite cerebral hyperperfusion at rest. Cerebral oxygenation further declines during HD due to reductions in CBF, and this may induce cerebral ischemia or "stunning." Intradialytic reductions in CBF are driven by decreases in cerebral perfusion pressure that may be partially opposed by bicarbonate shifts during dialysis. Intradialytic reductions in CBF have been related to several variables that are routinely measured in clinical practice including ultrafiltration rate and blood pressure. However, the role of compensatory cerebrovascular regulatory mechanisms during HD remains relatively unexplored. In particular, cerebral autoregulation can oppose reductions in CBF driven by reductions in systemic blood pressure, while cerebrovascular reactivity to CO2 may attenuate intradialytic reductions in CBF through promoting cerebral vasodilation. However, whether these mechanisms are effective in ESKD and during HD remain relatively unexplored. Important areas for future work include investigating potential alterations in cerebrovascular regulation in CKD and ESKD and how key regulatory mechanisms are engaged and integrated during HD to modulate intradialytic declines in CBF.
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Affiliation(s)
- Justin D Sprick
- Division of Renal Medicine, Department of Medicine, Emory University Department of Medicine, Atlanta, Georgia.,Department of Veterans Affairs Health Care System, Decatur, Georgia
| | - Joe R Nocera
- Department of Veterans Affairs Health Care System, Decatur, Georgia.,Center for Visual and Neurocognitive Rehabilitation, Department of Veterans Affairs Health Care System, Decatur, Georgia.,Departments of Neurology and Rehabilitation Medicine, Emory University Department of Medicine, Atlanta, Georgia
| | - Ihab Hajjar
- Department of Neurology, Emory University Department of Medicine, Atlanta, Georgia
| | - W Charles O'Neill
- Division of Renal Medicine, Department of Medicine, Emory University Department of Medicine, Atlanta, Georgia
| | - James Bailey
- Division of Renal Medicine, Department of Medicine, Emory University Department of Medicine, Atlanta, Georgia
| | - Jeanie Park
- Division of Renal Medicine, Department of Medicine, Emory University Department of Medicine, Atlanta, Georgia.,Department of Veterans Affairs Health Care System, Decatur, Georgia.,Center for Visual and Neurocognitive Rehabilitation, Department of Veterans Affairs Health Care System, Decatur, Georgia
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12
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Bracko O, Njiru BN, Swallow M, Ali M, Haft-Javaherian M, Schaffer CB. Increasing cerebral blood flow improves cognition into late stages in Alzheimer's disease mice. J Cereb Blood Flow Metab 2020; 40:1441-1452. [PMID: 31495298 PMCID: PMC7308509 DOI: 10.1177/0271678x19873658] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Alzheimer's disease is associated with a 20-30% reduction in cerebral blood flow. In the APP/PS1 mouse model of Alzheimer's disease, inhibiting neutrophil adhesion using an antibody against the neutrophil specific protein Ly6G was recently shown to drive rapid improvements in cerebral blood flow that was accompanied by an improvement in performance on short-term memory tasks. Here, in a longitudinal aging study, we assessed how far into disease development a single injection of anti-Ly6G treatment can acutely improve short-term memory function. We found that APP/PS1 mice as old as 15-16 months had improved performance on the object replacement and Y-maze tests of spatial and working short-term memory, measured at one day after anti-Ly6G treatment. APP/PS1 mice at 17-18 months of age or older did not show acute improvements in cognitive performance, although we did find that capillary stalls were still reduced and cerebral blood flow was still increased by 17% in 21-22-months-old APP/PS1 mice given anti-Ly6G antibody. These data add to the growing body of evidence suggesting that cerebral blood flow reductions are an important contributing factor to the cognitive dysfunction associated with neurodegenerative disease. Thus, interfering with neutrophil adhesion could be a new therapeutic approach for Alzheimer's disease.
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Affiliation(s)
- Oliver Bracko
- Nancy E. and Peter C. Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY, USA
| | - Brendah N Njiru
- Nancy E. and Peter C. Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY, USA
| | - Madisen Swallow
- Nancy E. and Peter C. Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY, USA
| | - Muhammad Ali
- Nancy E. and Peter C. Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY, USA
| | - Mohammad Haft-Javaherian
- Nancy E. and Peter C. Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY, USA
| | - Chris B Schaffer
- Nancy E. and Peter C. Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY, USA
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13
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Kellawan JM, Peltonen GL, Harrell JW, Roldan-Alzate A, Wieben O, Schrage WG. Differential contribution of cyclooxygenase to basal cerebral blood flow and hypoxic cerebral vasodilation. Am J Physiol Regul Integr Comp Physiol 2019; 318:R468-R479. [PMID: 31868517 DOI: 10.1152/ajpregu.00132.2019] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cyclooxygenase (COX) is proposed to regulate cerebral blood flow (CBF); however, accurate regional contributions of COX are relatively unknown at baseline and particularly during hypoxia. We hypothesized that COX contributes to both basal and hypoxic cerebral vasodilation, but COX-mediated vasodilation is greater in the posterior versus anterior cerebral circulation. CBF was measured in 9 healthy adults (28 ± 4 yr) during normoxia and isocapnic hypoxia (fraction of inspired oxygen = 0.11), with COX inhibition (oral indomethacin, 100mg) or placebo. Four-dimensional flow magnetic resonance imaging measured cross-sectional area (CSA) and blood velocity to quantify CBF in 11 cerebral arteries. Cerebrovascular conductance (CVC) was calculated (CVC = CBF × 100/mean arterial blood pressure) and hypoxic reactivity was expressed as absolute and relative change in CVC [ΔCVC/Δ pulse oximetry oxygen saturation (SpO2)]. At normoxic baseline, indomethacin reduced CVC by 44 ± 5% (P < 0.001) and artery CSA (P < 0.001), which was similar across arteries. Hypoxia (SpO2 80%-83%) increased CVC (P < 0.01), reflected as a similar relative increase in reactivity (% ΔCVC/-ΔSpO2) across arteries (P < 0.05), in part because of increases in CSA (P < 0.05). Indomethacin did not alter ΔCVC or ΔCVC/ΔSpO2 to hypoxia. These findings indicate that 1) COX contributes, in a largely uniform fashion, to cerebrovascular tone during normoxia and 2) COX is not obligatory for hypoxic vasodilation in any regions supplied by large extracranial or intracranial arteries.
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Affiliation(s)
- J Mikhail Kellawan
- Department of Kinesiology, University of Wisconsin, Madison, Wisconsin.,Department of Health and Exercise Science, University of Oklahoma, Norman, OK
| | - Garrett L Peltonen
- Department of Kinesiology, University of Wisconsin, Madison, Wisconsin.,Department of Kinesiology, Western New Mexico University, Silver City, New Mexico
| | - John W Harrell
- Department of Kinesiology, University of Wisconsin, Madison, Wisconsin
| | - Alejandro Roldan-Alzate
- Department of Radiology, University of Wisconsin, Madison, Wisconsin.,Department of Mechanical Engineering, University of Wisconsin, Madison, Wisconsin
| | - Oliver Wieben
- Department of Medical Physics, University of Wisconsin, Madison, Wisconsin
| | - William G Schrage
- Department of Kinesiology, University of Wisconsin, Madison, Wisconsin
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14
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Chapman CL, Hess HW, Worley ML. Heterogeneous redistribution of cerebral oxygen delivery to combined thermal and hypoxic exposure. J Physiol 2019; 598:443-445. [PMID: 31856421 DOI: 10.1113/jp279311] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Christopher L Chapman
- Center for Research and Education in Special Environments, University at Buffalo, Buffalo, NY, 14214, USA
| | - Hayden W Hess
- Center for Research and Education in Special Environments, University at Buffalo, Buffalo, NY, 14214, USA
| | - Morgan L Worley
- Center for Research and Education in Special Environments, University at Buffalo, Buffalo, NY, 14214, USA
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15
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Neumann S, Burchell AE, Rodrigues JC, Lawton CB, Burden D, Underhill M, Kobetić MD, Adams ZH, Brooks JC, Nightingale AK, Paton JFR, Hamilton MC, Hart EC. Cerebral Blood Flow Response to Simulated Hypovolemia in Essential Hypertension: A Magnetic Resonance Imaging Study. Hypertension 2019; 74:1391-1398. [PMID: 31656098 PMCID: PMC7069391 DOI: 10.1161/hypertensionaha.119.13229] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Supplemental Digital Content is available in the text. Hypertension is associated with raised cerebral vascular resistance and cerebrovascular remodeling. It is currently unclear whether the cerebral circulation can maintain cerebral blood flow (CBF) during reductions in cardiac output (CO) in hypertensive patients thereby avoiding hypoperfusion of the brain. We hypothesized that hypertension would impair the ability to effectively regulate CBF during simulated hypovolemia. In the present study, 39 participants (13 normotensive, 13 controlled, and 13 uncontrolled hypertensives; mean age±SD, 55±10 years) underwent lower body negative pressure (LBNP) at −20, −40, and −50 mmHg to decrease central blood volume. Phase-contrast MR angiography was used to measure flow in the basilar and internal carotid arteries, as well as the ascending aorta. CBF and CO decreased during LBNP (P<0.0001). Heart rate increased during LBNP, reaching significance at −50 mmHg (P<0.0001). There was no change in mean arterial pressure during LBNP (P=0.3). All participants showed similar reductions in CBF (P=0.3, between groups) and CO (P=0.7, between groups) during LBNP. There was no difference in resting CBF between the groups (P=0.36). In summary, during reductions in CO induced by hypovolemic stress, mean arterial pressure is maintained but CBF declines indicating that CBF is dependent on CO in middle-aged normotensive and hypertensive volunteers. Hypertension is not associated with impairments in the CBF response to reduced CO.
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Affiliation(s)
- Sandra Neumann
- From the Faculty of Life Sciences, School of Physiology, Pharmacology and Neuroscience (S.N., Z.H.A., J.B., A.K.N., J.P., E.C.H.), University of Bristol, United Kingdom
- Faculty of Health Sciences, Bristol Medical School (S.N., M.K.), University of Bristol, United Kingdom
| | - Amy E. Burchell
- University Hospitals Bristol NHS Foundation Trust, United Kingdom (A.E.B., J.R., C.B.L., D.B., M.U., A.K.N., M.H.)
| | - Jonathan C.L. Rodrigues
- University Hospitals Bristol NHS Foundation Trust, United Kingdom (A.E.B., J.R., C.B.L., D.B., M.U., A.K.N., M.H.)
- Department of Radiology, Royal United Hospitals Bath NHS Foundation Trust, United Kingdom (J.R.)
| | - Christopher B. Lawton
- University Hospitals Bristol NHS Foundation Trust, United Kingdom (A.E.B., J.R., C.B.L., D.B., M.U., A.K.N., M.H.)
| | - Daniel Burden
- University Hospitals Bristol NHS Foundation Trust, United Kingdom (A.E.B., J.R., C.B.L., D.B., M.U., A.K.N., M.H.)
| | - Melissa Underhill
- University Hospitals Bristol NHS Foundation Trust, United Kingdom (A.E.B., J.R., C.B.L., D.B., M.U., A.K.N., M.H.)
| | - Matthew D. Kobetić
- Faculty of Health Sciences, Bristol Medical School (S.N., M.K.), University of Bristol, United Kingdom
| | - Zoe H. Adams
- From the Faculty of Life Sciences, School of Physiology, Pharmacology and Neuroscience (S.N., Z.H.A., J.B., A.K.N., J.P., E.C.H.), University of Bristol, United Kingdom
| | - Jonathan C.W. Brooks
- From the Faculty of Life Sciences, School of Physiology, Pharmacology and Neuroscience (S.N., Z.H.A., J.B., A.K.N., J.P., E.C.H.), University of Bristol, United Kingdom
| | - Angus K. Nightingale
- From the Faculty of Life Sciences, School of Physiology, Pharmacology and Neuroscience (S.N., Z.H.A., J.B., A.K.N., J.P., E.C.H.), University of Bristol, United Kingdom
- University Hospitals Bristol NHS Foundation Trust, United Kingdom (A.E.B., J.R., C.B.L., D.B., M.U., A.K.N., M.H.)
| | - Julian F. R. Paton
- From the Faculty of Life Sciences, School of Physiology, Pharmacology and Neuroscience (S.N., Z.H.A., J.B., A.K.N., J.P., E.C.H.), University of Bristol, United Kingdom
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, New Zealand (J.P.)
| | - Mark C.K. Hamilton
- University Hospitals Bristol NHS Foundation Trust, United Kingdom (A.E.B., J.R., C.B.L., D.B., M.U., A.K.N., M.H.)
| | - Emma C. Hart
- From the Faculty of Life Sciences, School of Physiology, Pharmacology and Neuroscience (S.N., Z.H.A., J.B., A.K.N., J.P., E.C.H.), University of Bristol, United Kingdom
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16
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Abstract
PURPOSE To demonstrate the feasibility of a novel noninvasive MRI technique for the comprehensive evaluation of blood flow to the brain: combined angiography and perfusion using radial imaging and arterial spin labeling (CAPRIA). METHODS In the CAPRIA pulse sequence, blood labeled with a pseudocontinuous arterial spin labeling pulse train is continuously imaged as it flows through the arterial tree and into the brain tissue using a golden ratio radial readout. From a single raw data set, this flexible imaging approach allows the reconstruction of both high spatial/temporal resolution angiographic images with a high undersampling factor and low spatial/temporal resolution perfusion images with a low undersampling factor. The sparse and high SNR nature of angiographic images ensures that radial undersampling artifacts are relatively benign, even when using a simple regridding image reconstruction. Pulse sequence parameters were optimized through sampling efficiency calculations and the numerical evaluation of modified pseudocontinuous arterial spin labeling signal models. A comparison was made against conventional pseudocontinuous arterial spin labeling angiographic and perfusion acquisitions. RESULTS 2D CAPRIA data in healthy volunteers demonstrated the feasibility of this approach, with good vessel visualization in the angiographic images and clear tissue perfusion signal when reconstructed at 108-ms and 252-ms temporal resolution, respectively. Images were qualitatively similar to those from conventional acquisitions, but CAPRIA had significantly higher SNR efficiency (48% improvement on average, P = 0.02). CONCLUSION The CAPRIA technique shows potential for the efficient evaluation of both macrovascular blood flow and tissue perfusion within a single scan, with potential applications in a range of cerebrovascular diseases.
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Affiliation(s)
- Thomas W. Okell
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical NeurosciencesUniversity of OxfordOxfordUnited Kingdom
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17
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Flück D, Ainslie PN, Bain AR, Wildfong KW, Morris LE, Fisher JP. Extra- and intracranial blood flow regulation during the cold pressor test: influence of age. J Appl Physiol (1985) 2017; 123:1071-1080. [PMID: 28663374 DOI: 10.1152/japplphysiol.00224.2017] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Revised: 05/30/2017] [Accepted: 06/26/2017] [Indexed: 11/22/2022] Open
Abstract
We determined how the extra- and intracranial circulations respond to generalized sympathetic activation evoked by a cold pressor test (CPT) and whether this is affected by healthy aging. Ten young [23 ± 2 yr (means ± SD)] and nine older (66 ± 3 yr) individuals performed a 3-min CPT by immersing the left foot into 0.8 ± 0.3°C water. Common carotid artery (CCA) and internal carotid artery (ICA) diameter, velocity, and flow were simultaneously measured (duplex ultrasound) along with middle cerebral artery and posterior cerebral artery mean blood velocity (MCAvmean and PCAvmean) and cardiorespiratory variables. The increases in heart rate (~6 beats/min) and mean arterial blood pressure (~14 mmHg) were similar in young and older groups during the CPT (P < 0.01 vs. baseline). In the young group, the CPT elicited an ~5% increase in CCA diameter (P < 0.01 vs. baseline) and a tendency for an increase in CCA flow (~12%, P = 0.08); in contrast, both diameter and flow remained unchanged in the older group. Although ICA diameter was not changed during the CPT in either group, ICA flow increased (~8%, P = 0.02) during the first minute of the CPT in both groups. Whereas the CPT elicited an increase in MCAvmean and PCAvmean in the young group (by ~20 and ~10%, respectively, P < 0.01 vs. baseline), these intracranial velocities were unchanged in the older group. Collectively, during the CPT, these findings suggest a differential mechanism(s) of regulation between the ICA compared with the CCA in young individuals and a blunting of the CCA and intracranial responses in older individuals.NEW & NOTEWORTHY Sympathetic activation evoked by a cold pressor test elicits heterogeneous extra- and intracranial blood vessel responses in young individuals that may serve an important protective role. The extra- and intracranial responses to the cold pressor test are blunted in older individuals.
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Affiliation(s)
- Daniela Flück
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan, Kelowna, British Columbia, Canada; and
| | - 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
| | - Anthony R Bain
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan, Kelowna, British Columbia, Canada; and
| | - Kevin W Wildfong
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan, Kelowna, British Columbia, Canada; and
| | - Laura E Morris
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan, Kelowna, British Columbia, Canada; and
| | - James P Fisher
- School of Sport, Exercise, and Rehabilitation Sciences, College of Life and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom
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18
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Flück D, Morris LE, Niroula S, Tallon CM, Sherpa KT, Stembridge M, Ainslie PN, McManus AM. UBC-Nepal expedition: markedly lower cerebral blood flow in high-altitude Sherpa children compared with children residing at sea level. J Appl Physiol (1985) 2017; 123:1003-1010. [PMID: 28572497 DOI: 10.1152/japplphysiol.00292.2017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Revised: 05/28/2017] [Accepted: 05/30/2017] [Indexed: 12/12/2022] Open
Abstract
Developmental cerebral hemodynamic adaptations to chronic high-altitude exposure, such as in the Sherpa population, are largely unknown. To examine hemodynamic adaptations in the developing human brain, we assessed common carotid (CCA), internal carotid (ICA), and vertebral artery (VA) flow and middle cerebral artery (MCA) velocity in 25 (9.6 ± 1.0 yr old, 129 ± 9 cm, 27 ± 8 kg, 14 girls) Sherpa children (3,800 m, Nepal) and 25 (9.9 ± 0.7 yr old, 143 ± 7 cm, 34 ± 6 kg, 14 girls) age-matched sea level children (344 m, Canada) during supine rest. Resting gas exchange, blood pressure, oxygen saturation and heart rate were assessed. Despite comparable age, height and weight were lower (both P < 0.01) in Sherpa compared with sea level children. Mean arterial pressure, heart rate, and ventilation were similar, whereas oxygen saturation (95 ± 2 vs. 99 ± 1%, P < 0.01) and end-tidal Pco2 (24 ± 3 vs. 36 ± 3 Torr, P < 0.01) were lower in Sherpa children. Global cerebral blood flow was ∼30% lower in Sherpa compared with sea level children. This was reflected in a lower ICA flow (283 ± 108 vs. 333 ± 56 ml/min, P = 0.05), VA flow (78 ± 26 vs. 118 ± 35 ml/min, P < 0.05), and MCA velocity (72 ± 14 vs. 88 ± 14 cm/s, P < 0.01). CCA flow was similar between Sherpa and sea level children (425 ± 92 vs. 441 ± 81 ml/min, P = 0.52). Scaling flow and oxygen uptake for differences in vessel diameter and body size, respectively, led to the same findings. A lower cerebral blood flow in Sherpa children may reflect specific cerebral hemodynamic adaptations to chronic hypoxia.NEW & NOTEWORTHY Cerebral blood flow is lower in Sherpa children compared with children residing at sea level; this may reflect a cerebral hemodynamic pattern, potentially due to adaptation to a hypoxic environment.
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Affiliation(s)
- Daniela Flück
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, British Columbia, Canada;
| | - Laura E Morris
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, British Columbia, Canada
| | - Shailesh Niroula
- Institute of Medicine, Tribhuvan University, Kirtipur, Nepal.,Khunde Hospital, Khunde, Nepal; and
| | - Christine M Tallon
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, British Columbia, Canada
| | | | - Mike Stembridge
- Cardiff School of Sport, Cardiff Metropolitan University, Cardiff, United Kingdom
| | - Philip N Ainslie
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, British Columbia, Canada
| | - Ali M McManus
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, British Columbia, Canada
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19
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Billinger SA, Craig JC, Kwapiszeski SJ, Sisante JFV, Vidoni ED, Maletsky R, Poole DC. Dynamics of middle cerebral artery blood flow velocity during moderate-intensity exercise. J Appl Physiol (1985) 2017; 122:1125-1133. [PMID: 28280106 DOI: 10.1152/japplphysiol.00995.2016] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Revised: 02/21/2017] [Accepted: 03/02/2017] [Indexed: 12/25/2022] Open
Abstract
The dynamic response to a stimulus such as exercise can reveal valuable insights into systems control in health and disease that are not evident from the steady-state perturbation. However, the dynamic response profile and kinetics of cerebrovascular function have not been determined to date. We tested the hypotheses that bilateral middle cerebral artery blood flow mean velocity (MCAV) increases exponentially following the onset of moderate-intensity exercise in 10 healthy young subjects. The MCAV response profiles were well fit to a delay (TD) + exponential (time constant, τ) model with substantial agreement for baseline [left (L): 69, right (R): 64 cm/s, coefficient of variation (CV) 11%], response amplitude (L: 16, R: 13 cm/s, CV 23%), TD (L: 54, R: 52 s, CV 9%), τ (L: 30, R: 30 s, CV 22%), and mean response time (MRT) (L: 83, R: 82 s, CV 8%) between left and right MCAV as supported by the high correlations (e.g., MRT r = 0.82, P < 0.05) and low CVs. Test-retest reliability was high with CVs for the baseline, amplitude, and MRT of 3, 14, and 12%, respectively. These responses contrasted markedly with those of three healthy older subjects in whom the MCAV baseline and exercise response amplitude were far lower and the kinetics slowed. A single older stroke patient showed baseline ipsilateral MCAV that was lower still and devoid of any exercise response whatsoever. We conclude that kinetics analysis of MCAV during exercise has significant potential to unveil novel aspects of cerebrovascular function in health and disease.NEW & NOTEWORTHY Resolution of the dynamic stimulus-response profile provides a greater understanding of the underlying the physiological control processes than steady-state measurements alone. We report a novel method of measuring cerebrovascular blood velocity (MCAv) kinetics under ecologically valid conditions from rest to moderate-intensity exercise. This technique reveals that brain blood flow increases exponentially following the onset of exercise with 1) a strong bilateral coherence in young healthy individuals, and 2) a potential for unique age- and disease-specific profiles.
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Affiliation(s)
- Sandra A Billinger
- Department of Physical Therapy and Rehabilitation Science, University of Kansas Medical Center, Kansas City, Kansas;
| | - Jesse C Craig
- Department of Kinesiology, Kansas State University, Manhattan, Kansas.,College of Veterinary Medicine, Kansas State University, Manhattan, Kansas; and
| | - Sarah J Kwapiszeski
- Department of Physical Therapy and Rehabilitation Science, University of Kansas Medical Center, Kansas City, Kansas
| | - Jason-Flor V Sisante
- Department of Physical Therapy and Rehabilitation Science, University of Kansas Medical Center, Kansas City, Kansas
| | - Eric D Vidoni
- University of Kansas Alzheimer's Disease Center, Fairway, Kansas
| | | | - David C Poole
- Department of Kinesiology, Kansas State University, Manhattan, Kansas.,College of Veterinary Medicine, Kansas State University, Manhattan, Kansas; and
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20
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Khalil A, Bennet S, Thilaganathan B, Paladini D, Griffiths P, Carvalho JS. Prevalence of prenatal brain abnormalities in fetuses with congenital heart disease: a systematic review. Ultrasound Obstet Gynecol 2016; 48:296-307. [PMID: 27062519 DOI: 10.1002/uog.15932] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2015] [Revised: 03/18/2016] [Accepted: 03/21/2016] [Indexed: 06/05/2023]
Abstract
OBJECTIVES Studies have shown an association between congenital heart defects (CHDs) and postnatal brain abnormalities and neurodevelopmental delay. Recent evidence suggests that some of these brain abnormalities are present before birth. The primary aim of this study was to perform a systematic review to quantify the prevalence of prenatal brain abnormalities in fetuses with CHDs. METHODS MEDLINE, EMBASE and The Cochrane Library were searched electronically. Reference lists within each article were hand-searched for additional reports. The outcomes observed included structural brain abnormalities (on magnetic resonance imaging (MRI)) and changes in brain volume (on MRI, three-dimensional (3D) volumetric MRI, 3D ultrasound and phase-contrast MRI), brain metabolism or maturation (on magnetic resonance spectroscopy and phase-contrast MRI) and brain blood flow (on Doppler ultrasound, phase-contrast MRI and 3D power Doppler ultrasound) in fetuses with CHDs. Cohort and case-control studies were included and cases of chromosomal or genetic abnormalities, case reports and editorials were excluded. Proportion meta-analysis was used for analysis. Between-study heterogeneity was assessed using the I(2) test. RESULTS The search yielded 1943 citations, and 20 studies (n = 1175 cases) were included in the review. Three studies reported data on structural brain abnormalities, while data on altered brain volume, metabolism and blood flow were reported in seven, three and 14 studies, respectively. The three studies (221 cases) reporting on structural brain abnormalities were suitable for inclusion in a meta-analysis. The prevalence of prenatal structural brain abnormalities in fetuses with CHD was 28% (95% CI, 18-40%), with a similar prevalence (25% (95% CI, 14-39%)) when tetralogy of Fallot was considered alone. These abnormalities included ventriculomegaly (most common), agenesis of the corpus callosum, ventricular bleeding, increased extra-axial space, vermian hypoplasia, white-matter abnormalities and delayed brain development. Fetuses with CHD were more likely than those without CHD to have reduced brain volume, delay in brain maturation and altered brain circulation, most commonly in the form of reduced middle cerebral artery pulsatility index and cerebroplacental ratio. These changes were usually evident in the third trimester, but some studies reported them from as early as the second trimester. CONCLUSION In the absence of known major aneuploidy or genetic syndromes, fetuses with CHD are at increased risk of brain abnormalities, which are discernible prenatally. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.
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Affiliation(s)
- A Khalil
- Fetal Medicine Unit, St George's University of London, London, UK
| | - S Bennet
- Fetal Medicine Unit, St George's University of London, London, UK
| | - B Thilaganathan
- Fetal Medicine Unit, St George's University of London, London, UK
| | - D Paladini
- Fetal Medicine & Surgery Unit - Istituto G.Gaslini, Genoa, Italy
| | - P Griffiths
- Academic Unit of Radiology, University of Sheffield, Sheffield, UK
| | - J S Carvalho
- Fetal Medicine Unit, St George's University of London, London, UK
- Brompton Centre for Fetal Cardiology, Royal Brompton Hospital, London, UK
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21
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Borniger JC, Teplitsky S, Gnyawali S, Nelson RJ, Rink C. Photoperiodic Regulation of Cerebral Blood Flow in White-Footed Mice (Peromyscus leucopus). eNeuro 2016; 3:ENEURO. [PMID: 27570829 DOI: 10.1523/ENEURO.0058-16.2016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Revised: 07/05/2016] [Accepted: 07/05/2016] [Indexed: 11/21/2022] Open
Abstract
Individuals living outside the tropics need to adjust their behavioral and physiological repertoires throughout the year to adapt to the changing seasons. White-footed mice (Peromyscus leucopus) reduce hippocampal volumes, hippocampal-dependent memory function, long-term potentiation, and alter neurogenesis in response to short (winter-like) day lengths (photoperiods). During winter, these mice putatively shunt energy away from the brain to maximize peripheral thermogenesis, immune function, and survival. We hypothesized that these changes in brain function are accompanied by alterations in brain vasculature. We maintained white-footed mice in short (8 h light/16 h dark) or long (16 h light/8 h dark) photoperiods for 8–9 weeks. Mice were then perfused with fluorescein isothiocyanate (FITC)-conjugated tomato (Lycopersicon esculentum) lectin to visualize the perfused cerebrovasculature. Short-day mice reduced hippocampal and cortical capillary density (FITC+ area); vessels isolated from short day-exposed mice expressed higher mRNA levels of the gelatinase matrix metalloproteinase 2 (MMP2). Additionally, short-day mice reduced cerebral blood flow ∼15% compared with their long-day counterparts, as assessed by laser speckle flowmetry. Immunohistochemistry revealed higher levels of MMP2 in the hippocampus of mice maintained in short days compared with long days, potentially contributing to the observed vascular remodeling. These data demonstrate that a discrete environmental signal (i.e., day length) can substantially alter cerebral blood flow in adult mammals.
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Flück D, Siebenmann C, Keiser S, Cathomen A, Lundby C. Cerebrovascular reactivity is increased with acclimatization to 3,454 m altitude. J Cereb Blood Flow Metab 2015; 35:1323-30. [PMID: 25806704 PMCID: PMC4528007 DOI: 10.1038/jcbfm.2015.51] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Revised: 02/11/2015] [Accepted: 03/02/2015] [Indexed: 12/27/2022]
Abstract
Controversy exists regarding the effect of high-altitude exposure on cerebrovascular CO2 reactivity (CVR). Confounding factors in previous studies include the use of different experimental approaches, ascent profiles, duration and severity of exposure and plausibly environmental factors associated with altitude exposure. One aim of the present study was to determine CVR throughout acclimatization to high altitude when controlling for these. Middle cerebral artery mean velocity (MCAv mean) CVR was assessed during hyperventilation (hypocapnia) and CO2 administration (hypercapnia) with background normoxia (sea level (SL)) and hypoxia (3,454 m) in nine healthy volunteers (26 ± 4 years (mean ± s.d.)) at SL, and after 30 minutes (HA0), 3 (HA3) and 22 (HA22) days of high-altitude (3,454 m) exposure. At altitude, ventilation was increased whereas MCAv mean was not altered. Hypercapnic CVR was decreased at HA0 (1.16% ± 0.16%/mm Hg, mean ± s.e.m.), whereas both hyper- and hypocapnic CVR were increased at HA3 (3.13% ± 0.18% and 2.96% ± 0.10%/mm Hg) and HA22 (3.32% ± 0.12% and 3.24% ± 0.14%/mm Hg) compared with SL (1.98% ± 0.22% and 2.38% ± 0.10%/mm Hg; P < 0.01) regardless of background oxygenation. Cerebrovascular conductance (MCAv mean/mean arterial pressure) CVR was determined to account for blood pressure changes and revealed an attenuated response. Collectively our results show that hypocapnic and hypercapnic CVR are both elevated with acclimatization to high altitude.
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Affiliation(s)
- Daniela Flück
- 1] Zurich Center for Integrative Human Physiology (ZIHP), Zurich, Switzerland [2] Institute of Physiology, ZIHP, University of Zurich, Zurich, Switzerland
| | | | - Stefanie Keiser
- 1] Zurich Center for Integrative Human Physiology (ZIHP), Zurich, Switzerland [2] Institute of Physiology, ZIHP, University of Zurich, Zurich, Switzerland
| | - Adrian Cathomen
- Institute of Human Movement Sciences, ETH Zurich, Zurich, Switzerland
| | - Carsten Lundby
- 1] Zurich Center for Integrative Human Physiology (ZIHP), Zurich, Switzerland [2] Institute of Physiology, ZIHP, University of Zurich, Zurich, Switzerland [3] Department of Food and Nutrition and Sport Science, Gothenburg University, Gothenburg, Sweden
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Durazzo TC, Meyerhoff DJ, Murray DE. Comparison of Regional Brain Perfusion Levels in Chronically Smoking and Non-Smoking Adults. Int J Environ Res Public Health 2015; 12:8198-213. [PMID: 26193290 DOI: 10.3390/ijerph120708198] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Revised: 07/07/2015] [Accepted: 07/10/2015] [Indexed: 12/20/2022]
Abstract
Chronic cigarette smoking is associated with numerous abnormalities in brain neurobiology, but few studies specifically investigated the chronic effects of smoking (compared to the acute effects of smoking, nicotine administration, or nicotine withdrawal) on cerebral perfusion (i.e., blood flow). Predominately middle-aged male (47 ± 11 years of age) smokers (n = 34) and non-smokers (n = 27) were compared on regional cortical perfusion measured by continuous arterial spin labeling magnetic resonance studies at 4 Tesla. Smokers showed significantly lower perfusion than non-smokers in the bilateral medial and lateral orbitofrontal cortices, bilateral inferior parietal lobules, bilateral superior temporal gyri, left posterior cingulate, right isthmus of cingulate, and right supramarginal gyrus. Greater lifetime duration of smoking (adjusted for age) was related to lower perfusion in multiple brain regions. The results indicated smokers showed significant perfusion deficits in anterior cortical regions implicated in the development, progression, and maintenance of all addictive disorders. Smokers concurrently demonstrated reduced blood flow in posterior brain regions that show morphological and metabolic aberrations as well as elevated beta amyloid deposition demonstrated by those with early stage Alzheimer disease. The findings provide additional novel evidence of the adverse effects of cigarette smoking on the human brain.
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Sofronova SI, Tarasova OS, Gaynullina D, Borzykh AA, Behnke BJ, Stabley JN, McCullough DJ, Maraj JJ, Hanna M, Muller-Delp JM, Vinogradova OL, Delp MD. Spaceflight on the Bion-M1 biosatellite alters cerebral artery vasomotor and mechanical properties in mice. J Appl Physiol (1985) 2015; 118:830-8. [PMID: 25593287 PMCID: PMC4385880 DOI: 10.1152/japplphysiol.00976.2014] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Accepted: 01/13/2015] [Indexed: 01/03/2023] Open
Abstract
Conditions during spaceflight, such as the loss of the head-to-foot gravity vector, are thought to potentially alter cerebral blood flow and vascular resistance. The purpose of the present study was to determine the effects of long-term spaceflight on the functional, mechanical, and structural properties of cerebral arteries. Male C57BL/6N mice were flown 30 days in a Bion-M1 biosatellite. Basilar arteries isolated from spaceflight (SF) (n = 6), habitat control (HC) (n = 6), and vivarium control (VC) (n = 16) mice were used for in vitro functional and mechanical testing and histological structural analysis. The results demonstrate that vasoconstriction elicited through a voltage-gated Ca(2+) mechanism (30-80 mM KCl) and thromboxane A2 receptors (10(-8) - 3 × 10(-5) M U46619) are lower in cerebral arteries from SF mice. Inhibition of Rho-kinase activity (1 μM Y27632) abolished group differences in U46619-evoked contractions. Endothelium-dependent vasodilation elicited by acetylcholine (10 μM, 2 μM U46619 preconstriction) was virtually absent in cerebral arteries from SF mice. The pressure-diameter relation was lower in arteries from SF mice relative to that in HC mice, which was not related to differences in the extracellular matrix protein elastin or collagen content or the elastin/collagen ratio in the basilar arteries. Diameter, medial wall thickness, and medial cross-sectional area of unpressurized basilar arteries were not different among groups. These results suggest that the microgravity-induced attenuation of both vasoconstrictor and vasodilator properties may limit the range of vascular control of cerebral perfusion or impair the distribution of brain blood flow during periods of stress.
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Affiliation(s)
- Svetlana I Sofronova
- Institute for Biomedical Problems, Russian Academy of Sciences, Moscow; Faculty of Biology, M.V. Lomonosov Moscow State University
| | - Olga S Tarasova
- Institute for Biomedical Problems, Russian Academy of Sciences, Moscow; Faculty of Biology, M.V. Lomonosov Moscow State University
| | - Dina Gaynullina
- Institute for Biomedical Problems, Russian Academy of Sciences, Moscow; Faculty of Biology, M.V. Lomonosov Moscow State University; Department of Physiology, Russian National Research Medical University, Moscow, Russia
| | - Anna A Borzykh
- Institute for Biomedical Problems, Russian Academy of Sciences, Moscow
| | - Bradley J Behnke
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, Florida
| | - John N Stabley
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, Florida
| | - Danielle J McCullough
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, Florida
| | - Joshua J Maraj
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, Florida
| | - Mina Hanna
- Department of Materials Science and Engineering, Stanford University, Stanford, California
| | - Judy M Muller-Delp
- Department of Biomedical Sciences, Florida State University, Tallahassee, Florida; and
| | | | - Michael D Delp
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, Florida; Department of Nutrition, Food and Exercise Sciences, Florida State University, Tallahassee, Florida
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Phillips AA, Warburton DE, Ainslie PN, Krassioukov AV. Regional neurovascular coupling and cognitive performance in those with low blood pressure secondary to high-level spinal cord injury: improved by alpha-1 agonist midodrine hydrochloride. J Cereb Blood Flow Metab 2014; 34:794-801. [PMID: 24473484 DOI: 10.1038/jcbfm.2014.3] [Citation(s) in RCA: 75] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Revised: 12/10/2013] [Accepted: 12/30/2013] [Indexed: 12/30/2022]
Abstract
Individuals with high-level spinal cord injury (SCI) experience low blood pressure (BP) and cognitive impairments. Such dysfunction may be mediated in part by impaired neurovascular coupling (NVC) (i.e., cerebral blood flow responses to neurologic demand). Ten individuals with SCI >T6 spinal segment, and 10 age- and sex-matched controls were assessed for beat-by-beat BP, as well as middle and posterior cerebral artery blood flow velocity (MCAv, PCAv) in response to a NVC test. Tests were repeated in SCI after 10 mg midodrine (alpha1-agonist). Verbal fluency was measured before and after midodrine in SCI, and in the control group as an index of cognitive function. At rest, mean BP was lower in SCI (70 ± 10 versus 92 ± 14 mm Hg; P<0.05); however, PCAv conductance was higher (0.56 ± 0.13 versus 0.39 ± 0.15 cm/second/mm Hg; P<0.05). Controls exhibited a 20% increase in PCAv during cognition; however, the response in SCI was completely absent (P<0.01). When BP was increased with midodrine, NVC was improved 70% in SCI, which was reflected by a 13% improved cognitive function (P<0.05). Improvements in BP were related to improved cognitive function in those with SCI (r(2)=0.52; P<0.05). Impaired NVC, secondary to low BP, may partially mediate reduced cognitive function in individuals with high-level SCI.
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Taylor CR, Hanna M, Behnke BJ, Stabley JN, McCullough DJ, Davis RT, Ghosh P, Papadopoulos A, Muller-Delp JM, Delp MD. Spaceflight-induced alterations in cerebral artery vasoconstrictor, mechanical, and structural properties: implications for elevated cerebral perfusion and intracranial pressure. FASEB J 2013; 27:2282-92. [PMID: 23457215 PMCID: PMC3659353 DOI: 10.1096/fj.12-222687] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2012] [Accepted: 02/11/2013] [Indexed: 11/11/2022]
Abstract
Evidence indicates that cerebral blood flow is both increased and diminished in astronauts on return to Earth. Data from ground-based animal models simulating the effects of microgravity have shown that decrements in cerebral perfusion are associated with enhanced vasoconstriction and structural remodeling of cerebral arteries. Based on these results, the purpose of this study was to test the hypothesis that 13 d of spaceflight [Space Transportation System (STS)-135 shuttle mission] enhances myogenic vasoconstriction, increases medial wall thickness, and elicits no change in the mechanical properties of mouse cerebral arteries. Basilar and posterior communicating arteries (PCAs) were isolated from 9-wk-old female C57BL/6 mice for in vitro vascular and mechanical testing. Contrary to that hypothesized, myogenic vasoconstrictor responses were lower and vascular distensibility greater in arteries from spaceflight group (SF) mice (n=7) relative to ground-based control group (GC) mice (n=12). Basilar artery maximal diameter was greater in SF mice (SF: 236±9 μm and GC: 215±5 μm) with no difference in medial wall thickness (SF: 12.4±1.6 μm; GC: 12.2±1.2 μm). Stiffness of the PCA, as characterized via nanoindentation, was lower in SF mice (SF: 3.4±0.3 N/m; GC: 5.4±0.8 N/m). Collectively, spaceflight-induced reductions in myogenic vasoconstriction and stiffness and increases in maximal diameter of cerebral arteries signify that elevations in brain blood flow may occur during spaceflight. Such changes in cerebral vascular control of perfusion could contribute to increases in intracranial pressure and an associated impairment of visual acuity in astronauts during spaceflight.
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Affiliation(s)
| | - Mina Hanna
- Department of Mechanical and Aerospace Engineering
- Department of Applied Physiology and Kinesiology
| | - Bradley J. Behnke
- Department of Applied Physiology and Kinesiology
- Center for Exercise Science, and
| | - John N. Stabley
- Department of Applied Physiology and Kinesiology
- Center for Exercise Science, and
| | | | - Robert T. Davis
- Department of Applied Physiology and Kinesiology
- Center for Exercise Science, and
| | - Payal Ghosh
- Department of Applied Physiology and Kinesiology
- Center for Exercise Science, and
| | | | - Judy M. Muller-Delp
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, Florida, USA; and
| | - Michael D. Delp
- Department of Applied Physiology and Kinesiology
- Center for Exercise Science, and
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Schlader ZJ, Seifert T, Wilson TE, Bundgaard-Nielsen M, Secher NH, Crandall CG. Acute volume expansion attenuates hyperthermia-induced reductions in cerebral perfusion during simulated hemorrhage. J Appl Physiol (1985) 2013; 114:1730-5. [PMID: 23580601 DOI: 10.1152/japplphysiol.00079.2013] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Hyperthermia reduces the capacity to withstand a simulated hemorrhagic challenge, but volume loading preserves this capacity. This study tested the hypotheses that acute volume expansion during hyperthermia increases cerebral perfusion and attenuates reductions in cerebral perfusion during a simulated hemorrhagic challenge induced by lower-body negative pressure (LBNP). Eight healthy young male subjects underwent a supine baseline period (pre-LBNP), followed by 15- and 30-mmHg LBNP while normothermic, hyperthermic (increased pulmonary artery blood temperature ~1.1°C), and following acute volume infusion while hyperthermic. Primary dependent variables were mean middle cerebral artery blood velocity (MCAvmean), serving as an index of cerebral perfusion; mean arterial pressure (MAP); and cardiac output (thermodilution). During baseline, hyperthermia reduced MCAvmean (P = 0.001) by 12 ± 9% relative to normothermia. Volume infusion while hyperthermic increased cardiac output by 2.8 ± 1.4 l/min (P < 0.001), but did not alter MCAvmean (P = 0.99) or MAP (P = 0.39) compared with hyperthermia alone. Relative to hyperthermia, at 30-mmHg LBNP acute volume infusion attenuated reductions (P < 0.001) in cardiac output (by 2.5 ± 0.9 l/min; P < 0.001), MAP (by 5 ± 6 mmHg; P = 0.004), and MCAvmean (by 12 ± 13%; P = 0.002). These data indicate that acute volume expansion does not reverse hyperthermia-induced reductions in cerebral perfusion pre-LBNP, but that it does attenuate reductions in cerebral perfusion during simulated hemorrhage in hyperthermic humans.
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Affiliation(s)
- Zachary J Schlader
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital of Dallas, Dallas, Texas 75231, USA
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Abstract
Electrophysiologic and lesion studies of animals increasingly implicate the amygdala in aspects of emotional processing. Yet, the functions of the human amygdala remain poorly understood. To examine the contributions of the amygdala and other limbic and paralimbic regions to emotional processing, we exposed healthy subjects to aversive olfactory stimuli while measuring regional cerebral blood flow (rCBF) with positron emission tomography. Exposure to a highly aversive odorant produced strong rCBF increases in both amygdalae and in the left orbitofrontal cortex. Exposure to less aversive odorants produced rCBF increases in the orbitofrontal cortex but not in the amygdala. Change of rCBF within the left amygdala and the left OFC was highly intercorrelated, indicating a strong functional interaction between these brain regions. Furthermore, the activity within the left amygdala was associated significantly with subjective ratings of perceived aversiveness. These findings provide evidence that the human amygdala participates in the hedonic or emotional processing of olfactory stimuli.
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Affiliation(s)
- D H Zald
- Cognitive Neuroimaging Unit, Psychiatry Service, Veterans Affairs Medical Center, Minneapolis, MN 55417, USA
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