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acute intermittent hypoxia

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https://www.readbyqxmd.com/read/29220311/quantifying-the-effects-of-acute-hypoxic-exposure-on-exercise-performance-and-capacity-a-systematic-review-and-meta-regression
#1
Sanjoy K Deb, Daniel R Brown, Lewis A Gough, Christopher P McLellan, Paul A Swinton, S Andy Sparks, Lars R McNaughton
OBJECTIVE: To quantify the effects of acute hypoxic exposure on exercise capacity and performance, which includes continuous and intermittent forms of exercise. DESIGN: A systematic review was conducted with a three-level mixed effects meta-regression. The ratio of means method was used to evaluate main effects and moderators providing practical interpretations with percentage change. DATA SOURCES: A systemic search was performed using three databases (Google scholar, PubMed and SPORTDiscus)...
December 8, 2017: European Journal of Sport Science
https://www.readbyqxmd.com/read/29212793/pacap-6-38-or-kynurenate-microinjections-into-the-rvlm-prevent-development-of-sympathetic-long-term-facilitation-following-acute-intermittent-hypoxia
#2
Zohra M Kakall, Paul M Pilowsky, Melissa Mj Farnham
BACKGROUND AND PURPOSE: Intermittent hypoxia causes a persistent increase in sympathetic activity, which progresses to hypertension in chronic conditions such as obstructive sleep apnea (OSA). Pituitary adenylate cyclase activating polypeptide (PACAP) is an excitatory neurotransmitter that causes long-lasting sympathetic excitation. We aimed to determine if intermittent activation of the rostral ventrolateral medulla (RVLM) causes PACAP-mediated elevation of sympathetic nerve activity (sSNA), termed sympathetic long-term facilitation (sLTF)...
December 6, 2017: American Journal of Physiology. Heart and Circulatory Physiology
https://www.readbyqxmd.com/read/29159869/acute-intermittent-hypoxia-with-concurrent-hypercapnia-evokes-p2x-and-trpv1-receptor-dependent-sensory-long-term-facilitation-in-na%C3%A3-ve-carotid-bodies
#3
Arijit Roy, Melissa M J Farnham, Fatemeh Derakhshan, Paul M Pilowsky, Richard J A Wilson
Apneas constitute an acute existential threat to neonates and adults. In large part, this threat is detected by the carotid bodies, the primary peripheral chemoreceptors, and combatted by arousal and acute cardiorespiratory responses, including increased sympathetic output. Similar responses occur with repeated apneas but they continue beyond the last apnea and can persist for hours (i.e. ventilatory and sympathetic LTF). These long-term effects may be adaptive during acute episodic apnea, but may prolong hypertension causing chronic cardiovascular impairment...
November 21, 2017: Journal of Physiology
https://www.readbyqxmd.com/read/29130497/ubc-nepal-expedition-acclimatization-to-high-altitude-increases-spinal-motoneurone-excitability-during-fatigue-in-humans
#4
Luca Ruggiero, Alexandra F Yacyshyn, Jane Nettleton, Chris J McNeil
The fatigue-induced failure of the motor cortex to drive muscles maximally increases in acute hypoxia (AH) compared to normoxia (N) but improves with acclimatization (chronic hypoxia; CH). Despite their importance to muscle output, it is unknown how locomotor motoneurones in humans are affected by hypoxia and acclimatization. Eleven participants performed 16 min of submaximal (25% maximal torque, MVC) intermittent isometric elbow flexions in N, AH (environmental chamber), and CH (7-14 days at 5050 m) (PI O2 =  140, 74, and 76 mmHg, respectively)...
November 11, 2017: Journal of Physiology
https://www.readbyqxmd.com/read/29107023/intermittent-hypoxia-alters-dose-dependent-caffeine-effects-on-renal-prostanoids-and-receptors-in-neonatal-rats
#5
Kay D Beharry, Charles L Cai, Kultida Soontarapornchai, Taimur Ahmad, Gloria B Valencia, Jacob V Aranda
Caffeine, one of the most commonly prescribed drugs in preterm neonates, is given in standard or suprapharmacologic doses. Although known as a diuretic, its effects in the neonatal kidneys are not well studied. We tested the hypothesis that neonatal intermittent hypoxia (IH) and high caffeine doses (HCD) alter renal regulators of vasomotor tone and water balance. Newborn rats were randomized to room air, hyperoxia, or IH and treated with standard or high caffeine doses; or placebo saline. Renal prostanoids; histopathology; and cyclooxygenase (COX), prostanoid receptor, and aquaporin (AQP) immunoreactivity were determined...
October 26, 2017: Prostaglandins & Other Lipid Mediators
https://www.readbyqxmd.com/read/29081358/spinal-activation-of-protein-kinase-c-elicits-phrenic-motor-facilitation
#6
Michael J Devinney, Gordon S Mitchell
The protein kinase C family regulates many cellular functions, including multiple forms of neuroplasticity. The novel PKCθ and atypical PKCζ isoforms have been implicated in distinct forms of spinal, respiratory motor plasticity, including phrenic motor facilitation (pMF) following acute intermittent hypoxia or inactivity, respectively. Although these PKC isoforms are critical in regulating spinal motor plasticity, other isoforms may be important for phrenic motor plasticity. We tested the impact of conventional/novel PKC activator, phorbol 12-myristate 13-acetate (PMA) on pMF...
November 2, 2017: Respiratory Physiology & Neurobiology
https://www.readbyqxmd.com/read/29074711/enhanced-cerebral-perfusion-during-brief-exposures-to-cyclic-intermittent-hypoxemia
#7
Xiaoli Liu, Diqun Xu, James R Hall, Sarah Ross, Shande Chen, Howe Liu, Robert T Mallet, Xiangrong Shi
Cerebral vasodilation and increased cerebral oxygen extraction help maintain cerebral oxygen uptake in the face of hypoxemia. This study examined cerebrovascular responses to intermittent hypoxemia in eight healthy men breathing 10% O2 for 5 cycles, each 6 min, interspersed with 4 min of room air breathing. Hypoxia exposures raised heart rate (P<0.01) without altering arterial pressure, and increased ventilation (P<0.01) by expanding tidal volume. Arterial oxygen saturation (SaO2) and cerebral tissue oxygenation (ScO2) fell (P<0...
October 26, 2017: Journal of Applied Physiology
https://www.readbyqxmd.com/read/29074449/intermittent-but-not-sustained-moderate-hypoxia-elicits-long-term-facilitation-of-hypoglossal-motor-output
#8
Julia E R Wilkerson, Michael Devinney, Gordon S Mitchell
Phrenic long-term facilitation (pLTF) is a form of serotonin-dependent respiratory motor plasticity induced by moderate acute intermittent hypoxia (AIH), but not by moderate acute sustained hypoxia (ASH) of similar cumulative duration. Thus, moderate AIH-induced pLTF is sensitive to the pattern of hypoxia. On the other hand, pLTF induced by severe AIH protocols is neither pattern sensitive nor serotonin dependent (it converts to an adenosine-dependent mechanism). Although moderate AIH also induces hypoglossal LTF (hLTF), no data are available concerning its sensitivity/insensitivity to the pattern of hypoxia...
October 23, 2017: Respiratory Physiology & Neurobiology
https://www.readbyqxmd.com/read/29052004/hypoxia-regulated-catecholamine-secretion-in-chromaffin-cells
#9
REVIEW
Colin A Nurse, Shaima Salman, Angela L Scott
Adrenal catecholamine (CAT) secretion is a general physiological response of animals to environmental stressors such as hypoxia. This represents an important adaptive mechanism to maintain homeostasis and protect vital organs such as the brain. In adult mammals, CAT secretory responses are triggered by activation of the sympathetic nervous system that supplies cholinergic innervation of adrenomedullary chromaffin cells (AMC) via the splanchnic nerve. In the neonate, the splanchnic innervation of AMC is immature or absent, yet hypoxia stimulates a non-neurogenic CAT secretion that is critical for adaptation to extra-uterine life...
October 19, 2017: Cell and Tissue Research
https://www.readbyqxmd.com/read/29021191/enhancement-of-phrenic-long-term-facilitation-following-repetitive-acute-intermittent-hypoxia-is-blocked-by-the-glycolytic-inhibitor-2-deoxyglucose
#10
Peter M MacFarlane, Stephane Vinit, Gordon S Mitchell
Moderate acute intermittent hypoxia (mAIH) elicits a form of respiratory motor plasticity known as phrenic long-term facilitation (pLTF). Preconditioning with modest protocols of chronic intermittent hypoxia enhances pLTF, demonstrating pLTF metaplasticity. Since "low dose" protocols of repetitive acute intermittent hypoxia show promise as a therapeutic modality to restore respiratory (and non-respiratory) motor function in clinical disorders with compromised breathing, we tested the hypothesis that preconditioning with a mild repetitive AIH (rAIH) protocol enhances pLTF and hypoglossal (XII) LTF, and whether the enhancement is regulated by glycolytic flux...
October 11, 2017: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/28973619/effect-of-routine-low-dose-oxygen-supplementation-on-death-and-disability-in-adults-with-acute-stroke-the-stroke-oxygen-study-randomized-clinical-trial
#11
RANDOMIZED CONTROLLED TRIAL
Christine Roffe, Tracy Nevatte, Julius Sim, Jon Bishop, Natalie Ives, Phillip Ferdinand, Richard Gray
Importance: Hypoxia is common in the first few days after acute stroke, is frequently intermittent, and is often undetected. Oxygen supplementation could prevent hypoxia and secondary neurological deterioration and thus has the potential to improve recovery. Objective: To assess whether routine prophylactic low-dose oxygen therapy was more effective than control oxygen administration in reducing death and disability at 90 days, and if so, whether oxygen given at night only, when hypoxia is most frequent, and oxygen administration is least likely to interfere with rehabilitation, was more effective than continuous supplementation...
September 26, 2017: JAMA: the Journal of the American Medical Association
https://www.readbyqxmd.com/read/28972191/effects-of-acute-intermittent-hypoxia-on-hand-use-after-spinal-cord-trauma-a-preliminary-study
#12
RANDOMIZED CONTROLLED TRIAL
Randy D Trumbower, Heather B Hayes, Gordon S Mitchell, Steven L Wolf, Victoria A Stahl
OBJECTIVE: To test the hypothesis that daily acute intermittent hypoxia (AIH) combined with hand opening practice improves hand dexterity, function, and maximum hand opening in persons with chronic, motor-incomplete, cervical spinal cord injury. METHODS: Six participants completed the double-blind, crossover study. Participants received daily (5 consecutive days) AIH (15 episodes per day: 1.5 minutes of fraction of inspired oxygen [FIo2] = 0.09, 1-minute normoxic intervals) followed by 20 repetitions of hand opening practice and normoxia (sham, FIo2 = 0...
October 31, 2017: Neurology
https://www.readbyqxmd.com/read/28822818/phrenic-long-term-facilitation-following-intrapleural-ctb-sap-induced-respiratory-motor-neuron-death
#13
Nicole L Nichols, Taylor A Craig, Miles A Tanner
Amyotrophic lateral sclerosis (ALS) is a devastating disease leading to progressive motor neuron degeneration and death by ventilatory failure. In a rat model of ALS (SOD1(G93A)), phrenic long-term facilitation (pLTF) following acute intermittent hypoxia (AIH) is enhanced greater than expected at disease end-stage but the mechanism is unknown. We suggest that one trigger for this enhancement is motor neuron death itself. Intrapleural injections of cholera toxin B fragment conjugated to saporin (CTB-SAP) selectively kill respiratory motor neurons and mimic motor neuron death observed in SOD1(G93A) rats...
August 16, 2017: Respiratory Physiology & Neurobiology
https://www.readbyqxmd.com/read/28758418/intermittent-hypoxia-training-in-prediabetes-patients-beneficial-effects-on-glucose-homeostasis-hypoxia-tolerance-and-gene-expression
#14
Tetiana V Serebrovska, Alla G Portnychenko, Tetiana I Drevytska, Vladimir I Portnichenko, Lei Xi, Egor Egorov, Anna V Gavalko, Svitlana Naskalova, Valentina Chizhova, Valeriy B Shatylo
The present study aimed at examining beneficial effects of intermittent hypoxia training (IHT) under prediabetic conditions. We investigate the effects of three-week IHT on blood glucose level, tolerance to acute hypoxia, and leukocyte mRNA expression of hypoxia inducible factor 1α (HIF-1α) and its target genes, i.e. insulin receptor, facilitated glucose transporter-solute carrier family-2, and potassium voltage-gated channel subfamily J. Seven healthy and 11 prediabetic men and women (44-70 years of age) were examined before, next day and one month after three-week IHT (3 sessions per week, each session consisting 4 cycles of 5-min 12% O2 and 5-min room air breathing)...
September 2017: Experimental Biology and Medicine
https://www.readbyqxmd.com/read/28751456/intermittent-hypoxia-enhances-functional-connectivity-of-midcervical-spinal-interneurons
#15
Kristi A Streeter, Michael D Sunshine, Shreya Patel, Elisa J Gonzalez-Rothi, Paul J Reier, David M Baekey, David D Fuller
Brief, intermittent oxygen reductions [acute intermittent hypoxia (AIH)] evokes spinal plasticity. Models of AIH-induced neuroplasticity have focused on motoneurons; however, most midcervical interneurons (C-INs) also respond to hypoxia. We hypothesized that AIH would alter the functional connectivity between C-INs and induce persistent changes in discharge. Bilateral phrenic nerve activity was recorded in anesthetized and ventilated adult male rats and a multielectrode array was used to record C4/5 spinal discharge before [baseline (BL)], during, and 15 min after three 5 min hypoxic episodes (11% O2, H1-H3)...
August 30, 2017: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
https://www.readbyqxmd.com/read/28744643/involvement-of-autonomic-nervous-system-in-antiarrhythmic-effect-of-intermittent-hypobaric-hypoxia
#16
N V Naryzhnaya, A V Mukhamedzyanov, T V Lasukova, L N Maslov
We studied the involvement of the autonomic nervous system in the antiarrhythmic effect of intermittent hypobaric hypoxia modeled by daily placing the rats into an altitude chamber at 405 mm Hg (5000 m above sea level). The antiarrhythmic effect of hypoxia was observed on the model of acute coronary occlusion/reperfusion in vivo, but not during simulation of total ischemia/reperfusion of the isolated myocardium. Intravenous injection of ganglionic blocker hexamethonium (30 mg/kg) 15 min prior to in vivo coronary occlusion modeling abolished the antiarrhythmic effect of intermittent hypobaric hypoxia, which suggests that this effect is mediated via activation of the autonomic nervous system...
July 25, 2017: Bulletin of Experimental Biology and Medicine
https://www.readbyqxmd.com/read/28686686/protective-effect-of-zinc-preconditioning-against-renal-ischemia-reperfusion-injury-is-dose-dependent
#17
Kenny Rao, Kapil Sethi, Joseph Ischia, Luke Gibson, Laurence Galea, Lin Xiao, Mildred Yim, Mike Chang, Nathan Papa, Damien Bolton, Arthur Shulkes, Graham S Baldwin, Oneel Patel
OBJECTIVES: Ischemia-reperfusion injury (IRI) is a major cause of acute kidney injury and chronic kidney disease. Two promising preconditioning methods for the kidney, intermittent arterial clamping (IC) and treatment with the hypoxia mimetic cobalt chloride, have never been directly compared. Furthermore, the protective efficacy of the chemically related transition metal Zn2+ against renal IRI is unclear. Although Co2+ ions have been shown to protect the kidney via hypoxia inducible factor (HIF), the effect of Zn2+ ions on the induction of HIF1α, HIF2α and HIF3α has not been investigated previously...
2017: PloS One
https://www.readbyqxmd.com/read/28620058/intermittent-hypercapnic-hypoxia-during-sleep-does-not-induce-ventilatory-long-term-facilitation-in-healthy-males
#18
Naomi Louise Deacon, Doug R McEvoy, Daniel L Stadler, Peter G Catcheside
Intermittent hypoxia induced ventilatory neuroplasticity is likely important in obstructive sleep apnea pathophysiology. Although concomitant CO2 levels and arousal state critically influence neuroplastic effects of intermittent hypoxia, no studies have investigated intermittent hypercapnic hypoxia effects during sleep in humans. Thus, the purpose of this study was to investigate if intermittent hypercapnic hypoxia during sleep induces neuroplasticity (ventilatory long-term facilitation and increased chemoreflex responsiveness) in humans...
June 15, 2017: Journal of Applied Physiology
https://www.readbyqxmd.com/read/28592693/nongenomic-actions-of-17-%C3%AE-estradiol-restore-respiratory-neuroplasticity-in-young-ovariectomized-female-rats
#19
Brendan J Dougherty, Elizabeth S Kopp, Jyoti J Watters
Gonadal steroids modulate CNS plasticity, including phrenic long-term facilitation (pLTF), a form of spinal respiratory neuroplasticity resulting in increased phrenic nerve motor output following exposure to acute intermittent hypoxia (aIH; three 5 min episodes, 10.5% O2). Despite the importance of respiratory system neuroplasticity, and its dependence on estrogen in males, little is known about pLTF expression or mechanisms of estrogen signaling in females. Here, we tested the hypotheses that (1) pLTF expression in young, gonadally intact female rats would be expressed during estrous cycle stages in which 17β-estradiol (E2) is naturally high (e...
July 12, 2017: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
https://www.readbyqxmd.com/read/28585890/hypoxic-conditioning-and-the-central-nervous-system-a-new-therapeutic-opportunity-for-brain-and-spinal-cord-injuries
#20
REVIEW
S Baillieul, S Chacaroun, S Doutreleau, O Detante, J L Pépin, S Verges
Central nervous system diseases are among the most disabling in the world. Neuroprotection and brain recovery from either acute or chronic neurodegeneration still represent a challenge in neurology and neurorehabilitation as pharmacology treatments are often insufficiently effective. Conditioning the central nervous system has been proposed as a potential non-pharmacological neuro-therapeutic. Conditioning refers to a procedure by which a potentially deleterious stimulus is applied near to but below the threshold of damage to the organism to increase resistance to the same or even different noxious stimuli given above the threshold of damage...
June 2017: Experimental Biology and Medicine
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