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  1. Article ; Online: Global REACH 2018: High Altitude-Related Circulating Extracellular Microvesicles Promote a Proinflammatory Endothelial Phenotype

    Brewster, L Madden / Bain, Anthony R / Garcia, Vinicius P / DeSouza, Noah M / Tymko, Michael M / Greiner, Jared J / Ainslie, Philip N

    High altitude medicine & biology

    2023  Volume 24, Issue 3, Page(s) 223–229

    Abstract: ... J. Greiner, and Philip N. Ainslie. Global REACH 2018: high altitude-related circulating ... Brewster, L. Madden, Anthony R. Bain, Vinicius P. Garcia, Noah M. DeSouza, Michael M. Tymko, Jared ...

    Abstract Brewster, L. Madden, Anthony R. Bain, Vinicius P. Garcia, Noah M. DeSouza, Michael M. Tymko, Jared J. Greiner, and Philip N. Ainslie. Global REACH 2018: high altitude-related circulating extracellular microvesicles promote a proinflammatory endothelial phenotype
    MeSH term(s) Adult ; Humans ; Altitude ; Endothelial Cells ; NF-kappa B ; Interleukin-6 ; Phenotype ; Inflammation
    Chemical Substances NF-kappa B ; Interleukin-6
    Language English
    Publishing date 2023-07-27
    Publishing country United States
    Document type Journal Article
    ZDB-ID 2076262-8
    ISSN 1557-8682 ; 1527-0297
    ISSN (online) 1557-8682
    ISSN 1527-0297
    DOI 10.1089/ham.2023.0013
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: Acute isometric and dynamic exercise do not alter cerebral sympathetic nerve activity in healthy humans.

    Tymko, Michael M / Drapeau, Audrey / Vieira-Coelho, Maria Augusta / Labrecque, Lawrence / Imhoff, Sarah / Coombs, Geoff B / Langevin, Stephan / Fortin, Marc / Châteauvert, Nathalie / Ainslie, Philip N / Brassard, Patrice

    Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism

    2024  , Page(s) 271678X241248228

    Abstract: ... was monitored using the right radial artery. Total NA spillover increased during HG (P = 0.049), PECO ... P = 0.006), and moderate cycling exercise (P = 0.03) compared to rest. Cerebral NA spillover ... remained unchanged during isometric HG exercise (P = 0.36), PECO after the isometric HG exercise (P = 0.45 ...

    Abstract The impact of physiological stressors on cerebral sympathetic nervous activity (SNA) remains controversial. We hypothesized that cerebral noradrenaline (NA) spillover, an index of cerebral SNA, would not change during both submaximal isometric handgrip (HG) exercise followed by a post-exercise circulatory occlusion (PECO), and supine dynamic cycling exercise. Twelve healthy participants (5 females) underwent simultaneous blood sampling from the right radial artery and right internal jugular vein. Right internal jugular vein blood flow was measured using Duplex ultrasound, and tritiated NA was infused through the participants' right superficial forearm vein. Heart rate was recorded via electrocardiogram and blood pressure was monitored using the right radial artery. Total NA spillover increased during HG (P = 0.049), PECO (P = 0.006), and moderate cycling exercise (P = 0.03) compared to rest. Cerebral NA spillover remained unchanged during isometric HG exercise (P = 0.36), PECO after the isometric HG exercise (P = 0.45), and during moderate cycling exercise (P = 0.94) compared to rest. These results indicate that transient increases in blood pressure during acute exercise involving both small and large muscle mass do not engage cerebral SNA in healthy humans. Our findings suggest that cerebral SNA may be non-obligatory for exercise-related cerebrovascular adjustments.
    Language English
    Publishing date 2024-04-13
    Publishing country United States
    Document type Journal Article
    ZDB-ID 604628-9
    ISSN 1559-7016 ; 0271-678X
    ISSN (online) 1559-7016
    ISSN 0271-678X
    DOI 10.1177/0271678X241248228
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Intense exercise at high altitude causes platelet loss across the brain in humans.

    Gibbons, Travis Dylan / Caldwell, Hannah G / Islam, Hashim / Duffy, Jennifer / MacLeod, David B / Ainslie, Philip N

    The Journal of physiology

    2024  

    Abstract: ... jugular venous circulations (exercise: P < 0.001, interaction: P = 0.262), indicating no uptake or release ... values in both the arterial and jugular venous circulations (P = 0.590); however, intense exercise ... at high altitude caused a 31 ± 35% decrease in platelet concentration across the brain (P = 0.016 ...

    Abstract Platelets are known primarily for their role in blood clotting; however, it is becoming clear that they play diverse roles beyond that of haemostasis. Exercise has been shown to activate platelets and stimulate neurogenesis, neuroplasticity and improve cognitive function, highlighting a potentially powerful link between platelet function and brain health. Despite this clear link between platelets and the brain, very little is known about the behaviour of platelets through the cerebral circulation in humans. We examined platelet concentration across the brain in exercising humans at sea level (340 m) and high altitude (6-8 days at 3800 m; a stimulus known to modify platelet function). During intense exercise at sea level, platelet concentration increased similarly by 27 ± 17% in the arterial and internal jugular venous circulations (exercise: P < 0.001, interaction: P = 0.262), indicating no uptake or release of platelets into/from the brain. At high altitude, resting platelet concentrations were similar to sea level values in both the arterial and jugular venous circulations (P = 0.590); however, intense exercise at high altitude caused a 31 ± 35% decrease in platelet concentration across the brain (P = 0.016). This divergent response across the brain was not observed in any other haematological or metabolic variables. These data highlight a unique situation where the combination of intense exercise and high altitude hypoxia cause a decrease in platelet concentration across the cerebral circulation. The physiological implications and mechanisms that might influence platelet function across the brain during exercise at high altitude remain to be established. KEY POINTS: Platelets are known primarily for their role in blood clotting; however, it is becoming clear that they play diverse roles beyond that of haemostasis. Exercise has been shown to activate platelets, which in turn stimulate neurogenesis, neuroplasticity and improve cognitive function, highlighting a powerful link between platelet function and brain health. At sea level, platelet concentration in blood going into and out of the brain was similar at rest, during maximal exercise and in recovery from exercise. During maximal exercise at high altitude, platelet concentration was 31% lower in the blood exiting the brain; the final destination of these platelets is unknown. The physiological implications and mechanisms that might influence platelet function across the cerebral circulation during exercise at high altitude remain to be established.
    Language English
    Publishing date 2024-01-05
    Publishing country England
    Document type Journal Article
    ZDB-ID 3115-x
    ISSN 1469-7793 ; 0022-3751
    ISSN (online) 1469-7793
    ISSN 0022-3751
    DOI 10.1113/JP285603
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article ; Online: Jumping at a chance to control cerebral blood flow in astronauts.

    Bailey, Damian M / Ainslie, Philip N / Petersen, Lonnie / Zu Eulenburg, Peter

    Experimental physiology

    2021  Volume 106, Issue 7, Page(s) 1407–1409

    MeSH term(s) Astronauts ; Cerebrovascular Circulation ; Humans ; Space Flight ; Weightlessness
    Language English
    Publishing date 2021-05-27
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't ; Research Support, U.S. Gov't, Non-P.H.S. ; Comment
    ZDB-ID 1016295-1
    ISSN 1469-445X ; 0958-0670
    ISSN (online) 1469-445X
    ISSN 0958-0670
    DOI 10.1113/EP089648
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Article ; Online: Short-term ketone monoester supplementation improves cerebral blood flow and cognition in obesity: A randomized cross-over trial.

    Walsh, Jeremy J / Caldwell, Hannah G / Neudorf, Helena / Ainslie, Philip N / Little, Jonathan P

    The Journal of physiology

    2021  Volume 599, Issue 21, Page(s) 4763–4778

    Abstract: Adults with obesity are at increased risk of neurocognitive impairments, partly as a result of reduced cerebral blood flow and brain-derived neurotrophic factor (BDNF). Ketone supplements containing β-hydroxybutyrate (β-OHB) are a purported therapeutic ... ...

    Abstract Adults with obesity are at increased risk of neurocognitive impairments, partly as a result of reduced cerebral blood flow and brain-derived neurotrophic factor (BDNF). Ketone supplements containing β-hydroxybutyrate (β-OHB) are a purported therapeutic strategy for improving brain health in at-risk populations. We tested the hypothesis that short-term β-OHB supplementation will elevate cerebral blood flow and BDNF, as well as improve cognition in adults with obesity. In a placebo-controlled double-blind, cross-over design, 14 adults with obesity (10 females; aged 56 ± 12 years; body mass index = 33.8 ± 6.9 kg m
    MeSH term(s) Adult ; Cerebrovascular Circulation ; Cognition ; Cross-Over Studies ; Dietary Supplements ; Female ; Humans ; Ketones ; Obesity/complications
    Chemical Substances Ketones
    Language English
    Publishing date 2021-10-04
    Publishing country England
    Document type Journal Article ; Randomized Controlled Trial ; Research Support, Non-U.S. Gov't
    ZDB-ID 3115-x
    ISSN 1469-7793 ; 0022-3751
    ISSN (online) 1469-7793
    ISSN 0022-3751
    DOI 10.1113/JP281988
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article ; Online: Pulmonary vascular reactivity to supplemental oxygen in Sherpa and lowlanders during gradual ascent to high altitude.

    Subedi, Prajan / Gasho, Christopher / Stembridge, Michael / Williams, Alexandra M / Patrician, Alexander / Ainslie, Philip N / Anholm, James D

    Experimental physiology

    2022  Volume 108, Issue 1, Page(s) 111–122

    Abstract: ... irreversible. Study subjects were lowlanders (n = 20) and two Sherpa groups. All Sherpa were born and raised ... at altitude. One group (ascent Sherpa, n = 11) left altitude and after de-acclimatization in Kathmandu for ∼7 ... Sherpa, n = 12) remained continuously at altitude. Pulmonary artery systolic pressure (PASP) and ...

    Abstract New findings: What is the central question of this study? How does hypoxic pulmonary vasoconstriction and the response to supplemental oxygen change over time at high altitude? What is the main finding and its importance? Lowlanders and partially de-acclimatized Sherpa both demonstrated pulmonary vascular responsiveness to supplemental oxygen that was maintained for 12 days' exposure to progressively increasing altitude. An additional 2 weeks' acclimatization at 5050 m altitude rendered the pulmonary vasculature minimally responsive to oxygen similar to the fully acclimatized non-ascent Sherpa. Additional hypoxic exposure at that time point did not augment hypoxic pulmonary vasoconstriction.
    Abstract: Prolonged alveolar hypoxia leads to pulmonary vascular remodelling. We examined the time course at altitude, over which hypoxic pulmonary vasoconstriction goes from being acutely reversible to potentially irreversible. Study subjects were lowlanders (n = 20) and two Sherpa groups. All Sherpa were born and raised at altitude. One group (ascent Sherpa, n = 11) left altitude and after de-acclimatization in Kathmandu for ∼7 days re-ascended with the lowlanders over 8-10 days to 5050 m. The second Sherpa group (non-ascent Sherpa, n = 12) remained continuously at altitude. Pulmonary artery systolic pressure (PASP) and pulmonary vascular resistance (PVR) were measured while breathing ambient air and following supplemental oxygen. During ascent PASP and PVR increased in lowlanders and ascent Sherpa; however, with supplemental oxygen, lowlanders had significantly greater decrease in PASP (P = 0.02) and PVR (P = 0.02). After ∼14 days at 5050 m, PASP decreased with supplemental oxygen (mean decrease: 3.9 mmHg, 95% CI 2.1-5.7 mmHg, P < 0.001); however, PVR was unchanged (P = 0.49). In conclusion, PASP and PVR increased with gradual ascent to altitude and decreased via oxygen supplementation in both lowlanders and ascent Sherpa. Following ∼14 days at 5050 m altitude, there was no change in PVR to hypoxia or O
    MeSH term(s) Humans ; Altitude ; Hypoxia ; Altitude Sickness ; Acclimatization/physiology ; Oxygen
    Chemical Substances Oxygen (S88TT14065)
    Language English
    Publishing date 2022-11-20
    Publishing country England
    Document type Journal Article
    ZDB-ID 1016295-1
    ISSN 1469-445X ; 0958-0670
    ISSN (online) 1469-445X
    ISSN 0958-0670
    DOI 10.1113/EP090458
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  7. Article ; Online: Manipulation of iron status on cerebral blood flow at high altitude in lowlanders and adapted highlanders.

    Patrician, Alexander / Willie, Christopher / Hoiland, Ryan L / Gasho, Christopher / Subedi, Prajan / Anholm, James D / Tymko, Michael M / Ainslie, Philip N

    Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism

    2023  Volume 43, Issue 7, Page(s) 1166–1179

    Abstract: Cerebral blood flow (CBF) increases during hypoxia to counteract the reduction in arterial oxygen content. The onset of tissue hypoxemia coincides with the stabilization of hypoxia-inducible factor (HIF) and transcription of downstream HIF-mediated ... ...

    Abstract Cerebral blood flow (CBF) increases during hypoxia to counteract the reduction in arterial oxygen content. The onset of tissue hypoxemia coincides with the stabilization of hypoxia-inducible factor (HIF) and transcription of downstream HIF-mediated processes. It has yet to be determined, whether HIF down- or upregulation can modulate hypoxic vasodilation of the cerebral vasculature. Therefore, we examined whether: 1) CBF would increase with iron depletion (via chelation) and decrease with repletion (via iron infusion) at high-altitude, and 2) explore whether genotypic advantages of highlanders extend to HIF-mediated regulation of CBF. In a double-blinded and block-randomized design, CBF was assessed in 82 healthy participants (38 lowlanders, 20 Sherpas and 24 Andeans), before and after the infusion of either: iron(III)-hydroxide sucrose, desferrioxamine or saline. Across both lowlanders and highlanders, baseline iron levels contributed to the variability in cerebral hypoxic reactivity at high altitude (R
    MeSH term(s) Humans ; Altitude ; Acclimatization/physiology ; Deferoxamine ; Ferric Compounds ; Hypoxia ; Cerebrovascular Circulation ; Altitude Sickness
    Chemical Substances Deferoxamine (J06Y7MXW4D) ; Ferric Compounds
    Language English
    Publishing date 2023-03-08
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 604628-9
    ISSN 1559-7016 ; 0271-678X
    ISSN (online) 1559-7016
    ISSN 0271-678X
    DOI 10.1177/0271678X231152734
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  8. Article ; Online: The first patients treated with MR-CBCT soft-tissue matching in a MR-only prostate radiotherapy pathway.

    Wyatt, J J / Pearson, R A / Frew, J / Walker, C / Richmond, N / Wilkinson, M / Wilkes, K / Driver, S / West, S / Karen, P / Brooks-Pearson, R L / Ainslie, D / Wilkins, E / McCallum, H M

    Radiography (London, England : 1995)

    2023  Volume 29, Issue 2, Page(s) 347–354

    Abstract: ... The MR-only volumes were significantly smaller than MR-CT (p = 0.003), with a volume ratio 0.92 ± 0.02 ... matching was equivalent to CT-CBCT (p < 0.001), with differences of 0.1 ± 0.2 mm (vertical), -0.1 ± 0.2 mm ...

    Abstract Introduction: Magnetic Resonance (MR)-only radiotherapy for prostate cancer has previously been reported using fiducial markers for on-treatment verification. MR-Cone Beam Computed Tomography (CBCT) soft-tissue matching does not require invasive fiducial markers and enables MR-only treatments to other pelvic cancers. This study evaluated the first clinical implementation of MR-only prostate radiotherapy using MR-CBCT soft-tissue matching.
    Methods: Twenty prostate patients were treated with MR-only radiotherapy using a synthetic (s)CT-optimised plan with MR-CBCT soft-tissue matching. Two MR sequences were acquired: small Field Of View (FOV) for target delineation and large FOV for organs at risk delineation, sCT generation and on-treatment verification. Patients also received a CT for validation. The prostate was independently contoured on the small FOV MR, copied to the registered CT and modified if there were MR-CT soft-tissue alignment differences (MR-CT volume). This was compared to the MR-only volume with a paired t-test. The treatment plan was recalculated on CT and the doses compared. Independent offline CT-CBCT matches for 5/20 fractions were performed by three therapeutic radiographers using the MR-only contours and compared to the online MR-CBCT matches using two one-sided paired t-tests for equivalence within ±1 mm.
    Results: The MR-only volumes were significantly smaller than MR-CT (p = 0.003), with a volume ratio 0.92 ± 0.02 (mean ± standard error). The sCT isocentre dose difference to CT was 0.2 ± 0.1%. MR-CBCT soft-tissue matching was equivalent to CT-CBCT (p < 0.001), with differences of 0.1 ± 0.2 mm (vertical), -0.1 ± 0.2 mm (longitudinal) and 0.0 ± 0.1 mm (lateral).
    Conclusions: MR-only radiotherapy with soft-tissue matching has been successfully clinically implemented. It produced significantly smaller target volumes with high dosimetric and on-treatment matching accuracy.
    Implications for practice: MR-only prostate radiotherapy can be safely delivered without using invasive fiducial markers. This enables MR-only radiotherapy to be extended to other pelvic cancers where fiducial markers cannot be used.
    MeSH term(s) Male ; Humans ; Prostate/diagnostic imaging ; Pelvic Neoplasms ; Spiral Cone-Beam Computed Tomography ; Radiotherapy Planning, Computer-Assisted/methods ; Magnetic Resonance Spectroscopy
    Language English
    Publishing date 2023-02-01
    Publishing country Netherlands
    Document type Journal Article
    ZDB-ID 1289102-2
    ISSN 1532-2831 ; 1078-8174
    ISSN (online) 1532-2831
    ISSN 1078-8174
    DOI 10.1016/j.radi.2023.01.015
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  9. Article ; Online: Hourly staircase sprinting exercise "snacks" improve femoral artery shear patterns but not flow-mediated dilation or cerebrovascular regulation: a pilot study.

    Caldwell, Hannah G / Coombs, Geoff B / Rafiei, Hossein / Ainslie, Philip N / Little, Jonathan P

    Applied physiology, nutrition, and metabolism = Physiologie appliquee, nutrition et metabolisme

    2020  Volume 46, Issue 5, Page(s) 521–529

    Abstract: Healthy males ( ...

    Abstract Healthy males (
    MeSH term(s) Adult ; Carotid Artery, Internal/physiology ; Cerebrovascular Circulation ; Endothelium, Vascular/physiology ; Femoral Artery/physiology ; Hemodynamics ; Humans ; Leg/blood supply ; Male ; Pilot Projects ; Pulmonary Gas Exchange ; Sedentary Behavior ; Stair Climbing/physiology ; Time Factors ; Vasodilation ; Vertebral Artery/physiology ; Young Adult
    Language English
    Publishing date 2020-11-26
    Publishing country Canada
    Document type Journal Article
    ZDB-ID 2236708-1
    ISSN 1715-5320 ; 1715-5312
    ISSN (online) 1715-5320
    ISSN 1715-5312
    DOI 10.1139/apnm-2020-0562
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  10. Article ; Online: Differential Expression of Vascular-Related MicroRNA in Circulating Endothelial Microvesicles in Adults With Spinal Cord Injury: A Pilot Study.

    Park, Andrew J / Fandl, Hannah K / Garcia, Vinicius P / Coombs, Geoff B / DeSouza, Noah M / Greiner, Jared J / Barak, Otto F / Mijacika, Tanja / Dujic, Zeljko / Ainslie, Philip N / DeSouza, Christopher A

    Topics in spinal cord injury rehabilitation

    2023  Volume 29, Issue 2, Page(s) 34–42

    Abstract: Background: Spinal cord injury (SCI) is associated with an increased risk and prevalence of cardiopulmonary and cerebrovascular disease-related morbidity and mortality. The factors that initiate, promote, and accelerate vascular diseases and events in ... ...

    Abstract Background: Spinal cord injury (SCI) is associated with an increased risk and prevalence of cardiopulmonary and cerebrovascular disease-related morbidity and mortality. The factors that initiate, promote, and accelerate vascular diseases and events in SCI are poorly understood. Clinical interest in circulating endothelial cell-derived microvesicles (EMVs) and their microRNA (miRNA) cargo has intensified due to their involvement in endothelial dysfunction, atherosclerosis, and cerebrovascular events.
    Objectives: The aim of this study was to determine whether a subset of vascular-related miRNAs is differentially expressed in EMVs isolated from adults with SCI.
    Methods: We assessed eight adults with tetraplegia (7 male/1 female; age: 46±4 years; time since injury: 26±5 years) and eight uninjured (6 male/2 female; age: 39±3 years). Circulating EMVs were isolated, enumerated, and collected from plasma by flow cytometry. The expression of vascular-related miRNAs in EMVs was assessed by RT-PCR.
    Results: Circulating EMV levels were significantly higher (~130%) in adults with SCI compared with uninjured adults. The expression profile of miRNAs in EMVs from adults with SCI were significantly different than uninjured adults and were pathologic in nature. Expression of miR-126, miR-132, and miR-Let-7a were lower (~100-150%;
    Conclusion: This study is the first examination of EMV miRNA cargo in adults with SCI. The cargo signature of vascular-related miRNAs studied reflects a pathogenic EMV phenotype prone to induce inflammation, atherosclerosis, and vascular dysfunction. EMVs and their miRNA cargo represent a novel biomarker of vascular risk and a potential target for intervention to alleviate vascular-related disease after SCI.
    MeSH term(s) Humans ; Male ; Female ; MicroRNAs/genetics ; MicroRNAs/metabolism ; Pilot Projects ; Spinal Cord Injuries/metabolism ; Cell-Derived Microparticles/metabolism ; Cell-Derived Microparticles/pathology ; Atherosclerosis/metabolism ; Atherosclerosis/pathology
    Chemical Substances MicroRNAs ; MIRN145 microRNA, human
    Language English
    Publishing date 2023-04-03
    Publishing country United States
    Document type Journal Article
    ZDB-ID 1319299-1
    ISSN 1945-5763 ; 1082-0744
    ISSN (online) 1945-5763
    ISSN 1082-0744
    DOI 10.46292/sci22-00032
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