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https://www.readbyqxmd.com/read/29333725/chemoreflex-function-and-brain-blood-flow-during-upright-posture-in-men-and-women
#1
Christopher Hazlett, Heather Edgell
Orthostatic intolerance is more common in women than men, and some studies have found that women in the early follicular (EF) phase of the menstrual cycle experience the greatest feelings of lightheadedness. Chemoreflex function while supine or upright was investigated to determine the potential contribution of ventilatory control to these phenomena. Men (n = 13) and women (n = 14) were tested while supine and 70° upright (head-up tilt [HUT]) and given: (1) normoxia or (2) hypercapnia (5% CO2 ). Women were tested during the EF phase (days 2-5) and the midluteal phase (ML; days 18-24)...
January 2018: Physiological Reports
https://www.readbyqxmd.com/read/29326331/predicting-response-to-oxygen-therapy-in-obstructive-sleep-apnoea-patients-using-a-10-minute-daytime-test
#2
David Wang, Keith K Wong, Luke Rowsell, Garrick W Don, Brendon J Yee, Ronald R Grunstein
There is no satisfactory treatment for obstructive sleep apnoea (OSA). Supplemental low-flow oxygen therapy (LFO2) has been shown to reduce hypoxaemia and is well tolerated by patients with OSA. However, oxygen therapy may be beneficial only to certain subsets of patients with OSA. In this study, we evaluated a 10-min awake ventilatory chemoreflex test in predicting individual OSA response to 2 months of LFO2 therapy.At baseline, patients with OSA underwent ventilatory chemoreflex testing in the afternoon, prior to the overnight polysomnography...
January 2018: European Respiratory Journal: Official Journal of the European Society for Clinical Respiratory Physiology
https://www.readbyqxmd.com/read/29313987/variable-role-of-carotid-bodies-in-cardiovascular-responses-to-exercise-hypoxia-and-hypercapnia-in-spontaneously-hypertensive-rats
#3
Wioletta Pijacka, Pedro L Katayama, Helio C Salgado, Gisele S Lincevicius, Ruy R Campos, Fiona D McBryde, Julian F R Paton
The carotid body has recently emerged as a promising therapeutic target for treating cardiovascular disease, however the potential impact of carotid bodies removal on the dynamic cardiovascular responses to acute stressors such as exercise, hypoxia and hypercapnia in hypertension is an important safety consideration that has not been studied. We first validated a novel surgical approach to selectively resect the carotid bodies bilaterally (CBR) sparing the carotid sinus baroreflex. Second, we evaluated the impact of CBR on the cardiovascular responses to exercise, hypoxia and hypercapnia in the conscious, chronically instrumented spontaneously hypertensive (SH) rats...
January 5, 2018: Journal of Physiology
https://www.readbyqxmd.com/read/29308430/sex-specific-consequences-of-neonatal-stress-on-cardio-respiratory-inhibition-following-laryngeal-stimulation-in-rat-pups
#4
Cécile Baldy, Simon Chamberland, Stéphanie Fournier, Richard Kinkead
The presence of liquid near the larynx of immature mammals triggers prolonged apneas with significant O2 desaturations and bradycardias. When excessive, this reflex (the laryngeal chemoreflex; LCR) can be fatal. Our understanding of the origins of abnormal LCR are limited; however, perinatal stress and male sex are risk factors for cardio-respiratory failure in infants. Because exposure to stress during early life has deleterious and sex-specific consequences on brain development it is plausible that respiratory reflexes are vulnerable to neuroendocrine dysfunction...
November 2017: ENeuro
https://www.readbyqxmd.com/read/29209423/the-physiological-effects-of-slow-breathing-in-the-healthy-human
#5
Marc A Russo, Danielle M Santarelli, Dean O'Rourke
Slow breathing practices have been adopted in the modern world across the globe due to their claimed health benefits. This has piqued the interest of researchers and clinicians who have initiated investigations into the physiological (and psychological) effects of slow breathing techniques and attempted to uncover the underlying mechanisms. The aim of this article is to provide a comprehensive overview of normal respiratory physiology and the documented physiological effects of slow breathing techniques according to research in healthy humans...
December 2017: Breathe
https://www.readbyqxmd.com/read/29167119/revisiting-the-physiological-effects-of-exercise-training-on-autonomic-regulation-and-chemoreflex-control-in-heart-failure-does-ejection-fraction-matter
#6
David Cristobal Andrade, Alexis Arce-Alvarez, Camilo Toledo, Hugo S Diaz, Claudia Lucero, Rodrigo Quintanilla, Harold D Schultz, Noah J Marcus, Markus Amman, Rodrigo Del Rio
Heart failure (HF) is a global public health problem that, independent of its etiology (reduced (HFrEF) or preserved ejection fraction (HFpEF)), is characterized by functional impairments of cardiac function, chemoreflex hypersensitivity, baroreflex sensitivity (BRS) impairment, and abnormal autonomic regulation, all of which contribute to increased morbidity and mortality. Exercise training (ExT) has been identified as a nonpharmacological therapy capable of restoring normal autonomic function and improving survival in patients with HFrEF...
November 22, 2017: American Journal of Physiology. Heart and Circulatory Physiology
https://www.readbyqxmd.com/read/29166377/the-effect-of-body-position-on-esophageal-reflexes-in-cats-a-possible-mechanism-of-sids
#7
Ivan M Lang, Bidyut K Medda, Reza Shaker, Sudarshan Jadcherla
BACKGROUND: It has been hypothesized that life threatening events are caused by supra-esophageal reflux (SER) of gastric contents which activates laryngeal chemoreflex-stimulated apnea. Placing infants supine decreases the risk of sudden infant death syndrome (SIDS). The aim of this study was to determine whether body position affects esophageal reflexes that control SER. METHODS: We instrumented the pharyngeal and esophageal muscles of decerebrate cats (N=14) to record EMG or manometry, and investigated the effects of body position on the esophago-upper esophageal sphincter (UES) contractile reflex (EUCR), esophago-UES relaxation reflex (EURR), esophagus-stimulated pharyngeal swallow response (EPSR), secondary peristalsis (SP), and pharyngeal swallow (PS)...
November 22, 2017: Pediatric Research
https://www.readbyqxmd.com/read/29025748/compromised-cerebrovascular-regulation-and-cerebral-oxygenation-in-pulmonary-arterial-hypertension
#8
Simon Malenfant, Patrice Brassard, Myriam Paquette, Olivier Le Blanc, Audrey Chouinard, Valérie Nadeau, Philip D Allan, Yu-Chieh Tzeng, Sébastien Simard, Sébastien Bonnet, Steeve Provencher
BACKGROUND: Functional cerebrovascular regulatory mechanisms are important for maintaining constant cerebral blood flow and oxygen supply in heathy individuals and are altered in heart failure. We aim to examine whether pulmonary arterial hypertension (PAH) is associated with abnormal cerebrovascular regulation and lower cerebral oxygenation and their physiological and clinical consequences. METHODS AND RESULTS: Resting mean flow velocity in the middle cerebral artery mean flow velocity in the middle cerebral artery (MCAvmean); transcranial Doppler), cerebral pressure-flow relationship (assessed at rest and during squat-stand maneuvers; analyzed using transfer function analysis), cerebrovascular reactivity to CO2, and central chemoreflex were assessed in 11 patients with PAH and 11 matched healthy controls...
October 12, 2017: Journal of the American Heart Association
https://www.readbyqxmd.com/read/29023738/klf2-mediates-enhanced-chemoreflex-sensitivity-disordered-breathing-and-autonomic-dysregulation-in-heart-failure
#9
Noah J Marcus, Rodrigo Del Rio, Yanfeng Ding, Harold D Schultz
KEY POINTS: Enhanced carotid body chemoreflex activity contributes to development of disordered breathing patterns, autonomic dysregulation and increases in incidence of arrhythmia in animal models of reduced ejection fraction heart failure. Chronic reductions in carotid artery blood flow are associated with increased carotid body chemoreceptor activity. Krüppel-like Factor 2 (KLF2) is a shear stress-sensitive transcription factor that regulates the expression of enzymes which have previously been shown to play a role in increased chemoreflex sensitivity...
September 6, 2017: Journal of Physiology
https://www.readbyqxmd.com/read/28987939/a-hypothalamo-midbrain-medullary-pathway-involved-in-the-inhibition-of-the-respiratory-chemoreflex-response-induced-by-potassium-cyanide-in-rodents
#10
Tabinda Zafar, Charly Brouillard, Laurence Lanfumey, Caroline Sévoz-Couche
Recent studies have demonstrated that a mild stimulation of the dorsomedian nucleus of the hypothalamus (DMH), a defense area, induces the inhibition of the carotid chemoreflex tachypnea. DMH activation reduces the cardiac chemoreflex response via the dorsolateral part of the periaqueductal grey matter (dlPAG) and serotonin receptors (5-HT3 subtype) in the nucleus tractus solitarius (NTS). The objectives of this study were to assess whether dlPAG and subsequent NTS 5-HT3 receptors are involved in chemoreflex tachypnea inhibition during mild activation of the DMH...
October 4, 2017: Neuropharmacology
https://www.readbyqxmd.com/read/28971842/inorganic-nitrate-supplementation-attenuates-peripheral-chemoreflex-sensitivity-but-does-not-improve-cardiovagal-baroreflex-sensitivity-in-older-adults
#11
Joshua M Bock, Kenichi Ueda, Aaron C Schneider, William E Hughes, Jacqueline K Limberg, Nathan S Bryan, Darren P Casey
Aging is associated with increased peripheral chemoreceptor activity, reduced nitric oxide (NO) bioavailability, as well as attenuation of cardiovagal baroreflex sensitivity (BRS), collectively increasing the risk of cardiovascular disease. Evidence suggests NO may attenuate peripheral chemoreflex sensitivity and increase BRS. Exogenous inorganic nitrate increases NO bioavailability via the nitrate-nitrite-nitric oxide pathway. Our hypothesis was that inorganic nitrate supplementation would attenuate peripheral chemoreflex sensitivity and enhance spontaneous cardiovagal BRS in older adults...
September 29, 2017: American Journal of Physiology. Heart and Circulatory Physiology
https://www.readbyqxmd.com/read/28966145/how-important-is-the-co2-chemoreflex-for-the-control-of-breathing-environmental-and-evolutionary-considerations
#12
REVIEW
Joseph M Santin
Haldane and Priestley (1905) discovered that the ventilatory control system is highly sensitive to CO2. This "CO2 chemoreflex" has been interpreted to dominate control of resting arterial PCO2/pH (PaCO2/pHa) by monitoring PaCO2/pHa and altering ventilation through negative feedback. However, PaCO2/pHa varies little in mammals as ventilation tightly couples to metabolic demands, which may minimize chemoreflex control of PaCO2. The purpose of this synthesis is to (1) interpret data from experimental models with meager CO2 chemoreflexes to infer their role in ventilatory control of steady-state PaCO2, and (2) identify physiological causes of respiratory acidosis occurring normally across vertebrate classes...
September 29, 2017: Comparative Biochemistry and Physiology. Part A, Molecular & Integrative Physiology
https://www.readbyqxmd.com/read/28948697/sustained-sympathetic-activity-in-altitude-acclimatizing-lowlanders-and-high-altitude-natives
#13
C Lundby, J Calbet, G van Hall, B Saltin, M Sander
Combined results from different independent studies suggest that acclimatization to high altitude induces a slowly developing sympathetic activation, even at levels of hypoxia that cause no acute chemoreflex-mediated sympathoexcitation. We here provide direct neurophysiological evidence for this phenomenon. In eight Danish lowlanders, we quantified mean arterial blood pressure (MAP), heart rate (HR), and muscle sympathetic nerve activity (MSNA), twice at sea level (normoxia and with acute hypoxic exposure to 12...
September 25, 2017: Scandinavian Journal of Medicine & Science in Sports
https://www.readbyqxmd.com/read/28899913/central-chemoreflex-activation-induces-sympatho-excitation-without-altering-static-or-dynamic-baroreflex-function-in-normal-rats
#14
Keita Saku, Takeshi Tohyama, Masako Shinoda, Takuya Kishi, Kazuya Hosokawa, Takuya Nishikawa, Yasuhiro Oga, Takafumi Sakamoto, Hiroyuki Tsutsui, Tadayoshi Miyamoto, Kenji Sunagawa
Central chemoreflex activation induces sympatho-excitation. However, how central chemoreflex interacts with baroreflex function remains unknown. This study aimed to examine the impact of central chemoreflex on the dynamic as well as static baroreflex functions under open-loop conditions. In 15 anesthetized, vagotomized Sprague-Dawley rats, we isolated bilateral carotid sinuses and controlled intra-sinus pressure (CSP). We then recorded sympathetic nerve activity (SNA) at the celiac ganglia, and activated central chemoreflex by a gas mixture containing various concentrations of CO2 Under the baroreflex open-loop condition (CSP = 100 mmHg), central chemoreflex activation linearly increased SNA and arterial pressure (AP)...
September 2017: Physiological Reports
https://www.readbyqxmd.com/read/28840941/acute-fall-and-long-term-rise-in-oxygen-saturation-in-response-to-meditation
#15
Nicolò F Bernardi, Marco Bordino, Lucio Bianchi, Luciano Bernardi
The effects of meditation on arterial and tissue oxygenation are unknown and difficult to assess because respiration is often altered, directly or indirectly, during meditation practice. Thus, changes in respiration may affect cardiovascular responses independently from meditation. In this study, we aim to isolate the specific effect of meditation on arterial and tissue oxygenation and other cardiorespiratory indexes while systematically controlling for the role of respiration. Furthermore, we aim to clarify to what extent prior expertise in meditation practice is needed to observe reliable changes...
August 25, 2017: Psychophysiology
https://www.readbyqxmd.com/read/28835525/ventilation-inhibits-sympathetic-action-potential-recruitment-even-during-severe-chemoreflex-stress
#16
Mark B Badrov, Otto F Barak, Tanja Mijacika, Leena N Shoemaker, Lindsay J Borrell, Mihajlo Lojpur, Ivan Drvis, Zeljko Dujic, J Kevin Shoemaker
This study investigated the influence of ventilation on sympathetic action potential (AP) discharge patterns during varying levels of high chemoreflex stress. In seven trained breath-hold divers (age 33 ± 12 yr), we measured muscle sympathetic nerve activity (MSNA) at baseline, during preparatory rebreathing (RBR), and during 1) functional residual capacity apnea (FRCApnea) and 2) continued RBR. Data from RBR were analyzed at matched (i.e., to FRCApnea) hemoglobin saturation (HbSat) levels (RBRMatched) or more severe levels (RBREnd)...
November 1, 2017: Journal of Neurophysiology
https://www.readbyqxmd.com/read/28808320/carotid-body-mediated-chemoreflex-drive-in-the-setting-of-low-and-high-output-heart-failure
#17
Rodrigo Del Rio, David C Andrade, Camilo Toledo, Hugo S Diaz, Claudia Lucero, Alexis Arce-Alvarez, Noah J Marcus, Harold D Schultz
Enhanced carotid body (CB) chemoreflex function is strongly related to cardiorespiratory disorders and disease progression in heart failure (HF). The mechanisms underlying CB sensitization during HF are not fully understood, however previous work indicates blood flow per se can affect CB function. Then, we hypothesized that the CB-mediated chemoreflex drive will be enhanced only in low output HF but not in high output HF. Myocardial infarcted rats and aorto-caval fistulated rats were used as a low output HF model (MI-CHF) and as a high output HF model (AV-CHF), respectively...
August 14, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28757365/assessing-chemoreflexes-and-oxygenation-in-the-context-of-acute-hypoxia-implications-for-field-studies
#18
Jamie R Pfoh, Craig D Steinback, Emily R Vanden Berg, Christina D Bruce, Trevor A Day
Carotid chemoreceptors detect changes in PO2 and elicit a peripheral respiratory chemoreflex (PCR). The PCR can be tested through a transient hypoxic ventilatory response test (TT-HVR), which may not be safe nor feasible at altitude. We characterized a transient hyperoxic ventilatory withdrawal test in the setting of steady-state normobaric hypoxia (13.5-14% FIO2) and compared it to a TT-HVR and a steady-state poikilocapnic hypoxia test, within-individuals. No PCR test magnitude was correlated with any other test, nor was any test magnitude correlated with oxygenation while in steady-state hypoxia...
December 2017: Respiratory Physiology & Neurobiology
https://www.readbyqxmd.com/read/28740186/carotid-sinus-nerve-electrical-stimulation-in-conscious-rats-attenuates-systemic-inflammation-via-chemoreceptor-activation
#19
Fernanda Machado Santos-Almeida, Gean Domingos-Souza, César A Meschiari, Laura Campos Fávaro, Christiane Becari, Jaci A Castania, Alexandre Lopes, Thiago M Cunha, Davi J A Moraes, Fernando Q Cunha, Luis Ulloa, Alexandre Kanashiro, Geisa C S V Tezini, Helio C Salgado
Recent studies demonstrated a critical functional connection between the autonomic (sympathetic and parasympathetic) nervous and the immune systems. The carotid sinus nerve (CSN) conveys electrical signals from the chemoreceptors of the carotid bifurcation to the central nervous system where the stimuli are processed to activate sympathetic and parasympathetic efferent signals. Here, we reported that chemoreflex activation via electrical CSN stimulation, in conscious rats, controls the innate immune response to lipopolysaccharide attenuating the plasma levels of inflammatory cytokines such as tumor necrosis factor (TNF), interleukin 1β (IL-1β) and interleukin 6 (IL-6)...
July 24, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28677303/glial-eaat2-regulation-of-extracellular-nts-glutamate-critically-controls-neuronal-activity-and-cardiorespiratory-reflexes
#20
Michael P Matott, David D Kline, Eileen M Hasser
KEY POINTS: Excitatory amino acid transporter 2 (EAAT2) is present on astrocytes in the nucleus tractus solitarii (nTS), an important nucleus in cardiorespiratory control. Its specific role in influencing nTS neuronal activity and thereby basal and reflex cardiorespiratory function is unknown. The specific role of nTS EAAT2 was determined via whole animal and brainstem slice patch clamp experiments. Astrocytic EAAT2 buffers basal glutamate activation of AMPA-type glutamate receptors and therefore decreases baseline excitability of nTS neurons...
September 1, 2017: Journal of Physiology
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