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acute intermittent hypoxia

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https://www.readbyqxmd.com/read/29423544/high-intensity-interval-training-in-hypoxia-does-not-affect-muscle-hif-responses-to-acute-hypoxia-in-humans
#1
Stefan De Smet, Gommaar D'Hulst, Chiel Poffé, Ruud Van Thienen, Emanuele Berardi, Peter Hespel
PURPOSE: The myocellular response to hypoxia is primarily regulated by hypoxia-inducible factors (HIFs). HIFs thus conceivably are implicated in muscular adaptation to altitude training. Therefore, we investigated the effect of hypoxic versus normoxic training during a period of prolonged hypoxia ('living high') on muscle HIF activation during acute ischaemia. METHODS: Ten young male volunteers lived in normobaric hypoxia for 5 weeks (5 days per week, ~ 15.5 h per day, FiO2: 16...
February 8, 2018: European Journal of Applied Physiology
https://www.readbyqxmd.com/read/29373484/mechanisms-of-cardiovascular-protection-associated-with-intermittent-hypobaric-hypoxia-exposure-in-a-rat-model-role-of-oxidative-stress
#2
Miguel Aguilar, Alejandro González-Candia, Jorge Rodríguez, Catalina Carrasco-Pozo, Daniel Cañas, Claudio García-Herrera, Emilio A Herrera, Rodrigo L Castillo
More than 140 million people live and works (in a chronic or intermittent form) above 2500 m worldwide and 35 million live in the Andean Mountains. Furthermore, in Chile, it is estimated that 55,000 persons work in high altitude shifts, where stays at lowlands and interspersed with working stays at highlands. Acute exposure to high altitude has been shown to induce oxidative stress in healthy human lowlanders, due to an increase in free radical formation and a decrease in antioxidant capacity. However, in animal models, intermittent hypoxia (IH) induce preconditioning, like responses and cardioprotection...
January 26, 2018: International Journal of Molecular Sciences
https://www.readbyqxmd.com/read/29357503/the-hypothalamic-pvn-contributes-to-acute-intermittent-hypoxia-induced-sympathetic-but-not-phrenic-long-term-facilitation
#3
Megan Bardgett Blackburn, Mary Ann Andrade, Glenn M Toney
Acute intermittent hypoxia (AIH) repetitively activates the arterial chemoreflex and triggers a progressive increase of sympathetic nerve activity (SNA) and phrenic nerve activity (PNA) referred to as sympathetic and phrenic long-term facilitation (S-LTF and P-LTF), respectively. Neurons of the hypothalamic paraventricular nucleus (PVN) participate in the arterial chemoreflex, but their contribution to AIH-induced LTF is unknown. To determine this, anesthetized rats were vagotomized and exposed to 10 cycles of AIH, each consisting of ventilation for 3 minutes with 100% O2 followed by 3 minutes with 15% O2...
December 21, 2017: Journal of Applied Physiology
https://www.readbyqxmd.com/read/29233741/cyclooxygenase-enzyme-activity-does-not-impair-respiratory-motor-plasticity-after-one-night-of-intermittent-hypoxia
#4
Adrianne G Huxtable, Elizabeth Kopp, Brendan J Doughtery, Jyoti J Watters, Gordon S Mitchell
Although inflammation is prevalent in many clinical disorders challenging breathing, we are only beginning to understand the impact of inflammation on neural mechanisms of respiratory control. We recently demonstrated one form of respiratory motor plasticity is extremely sensitive to even mild inflammation induced by a single night (8 h) of intermittent hypoxia (IH-1), mimicking aspects of obstructive sleep apnea. Specifically, phrenic long-term facilitation (pLTF) following moderate acute intermittent hypoxia (AIH) is abolished by IH-1, but restored by high doses of the non-steroidal anti-inflammatory drug, ketoprofen...
December 9, 2017: Respiratory Physiology & Neurobiology
https://www.readbyqxmd.com/read/29220311/quantifying-the-effects-of-acute-hypoxic-exposure-on-exercise-performance-and-capacity-a-systematic-review-and-meta-regression
#5
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
#6
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
#7
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
#8
Luca Ruggiero, Alexandra F Yacyshyn, Jane Nettleton, Chris J McNeil
KEY POINTS: Acute exposure and acclimatization to hypoxia are associated with an impairment and partial recovery, respectively, of the capability of the central nervous system to drive muscles during prolonged efforts. Motoneurones play a vital role in muscle contraction and in fatigue, although the effect of hypoxia on motoneurone excitability during exercise has not been assessed in humans. We studied the impact of fatigue on motoneurone excitability in normoxia, acute and chronic exposure (5050 m) to hypoxia...
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
#9
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
#10
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
#11
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
#12
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
#13
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
#14
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
#15
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
#16
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
#17
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
#18
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% O 2 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
#19
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
#20
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
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