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https://www.readbyqxmd.com/read/29025748/compromised-cerebrovascular-regulation-and-cerebral-oxygenation-in-pulmonary-arterial-hypertension
#1
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
#2
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
#3
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
#4
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
#5
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
#6
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
#7
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
#8
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
#9
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 (33±12 yrs), we measured muscle sympathetic nerve activity (MSNA) at baseline, during preparatory rebreathing (RBR), and during i) functional residual capacity apnea (FRCApnea) and ii) continued RBR. Data from RBR were analyzed at matched (i.e., to FRCApnea) hemoglobin saturation (HbSat) levels (RBRMatched) or more severe levels (RBREnd)...
August 23, 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
#10
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
#11
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
#12
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
#13
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
https://www.readbyqxmd.com/read/28675564/activation-of-serotonergic-neurons-in-the-medullary-caudal-raphe-shortens-the-laryngeal-chemoreflex-in-anaesthetized-neonatal-rats
#14
William T Donnelly, Luxi Xia, Donald Bartlett, J C Leiter
What is the central question of this study? Does activation of serotonergic neurons in the caudal medullary raphe, some of which project to the nucleus of the solitary tract, shorten the laryngeal chemoreflex? What is the main finding and its importance? We found that serotonin originating from neurons in the caudal raphe acts through a 5-HT3 receptor located in the nucleus of the solitary tract to terminate reflex apnoea. Failure or deficiency of this arousal-related process is likely to be relevant to the pathogenesis of sudden infant death syndrome...
July 3, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28666602/integrated-cardiovascular-respiratory-control-in-type-1-diabetes-evidences-functional-imbalance-possible-role-of-hypoxia
#15
L Bianchi, C Porta, A Rinaldi, C Gazzaruso, P Fratino, P DeCata, P Protti, R Paltro, L Bernardi
BACKGROUND: Cardiovascular (baroreflex) and respiratory (chemoreflex) control mechanisms were studied separately in diabetes, but their reciprocal interaction (well known for diseases like heart failure) had never been comprehensively assessed. We hypothesized that prevalent autonomic neuropathy would depress both reflexes, whereas prevalent autonomic imbalance through sympathetic activation would depress the baroreflex but enhance the chemoreflexes. METHODS: In 46 type-1 diabetic subjects (7...
June 15, 2017: International Journal of Cardiology
https://www.readbyqxmd.com/read/28659824/hypersensitivity-of-vagal-pulmonary-afferents-induced-by-tumor-necrosis-factor-alpha-in-mice
#16
Ruei-Lung Lin, Qihai Gu, Lu-Yuan Lee
Tumor necrosis factor alpha (TNFα), a pro-inflammatory cytokine, plays a significant role in the pathogenesis of allergic asthma. Inhalation of TNFα also induces airway hyperresponsiveness in healthy human subjects, and the underlying mechanism is not fully understood. A recent study reported that TNFα caused airway inflammation and a sustained elevation of pulmonary chemoreflex responses in mice, suggesting a possible involvement of heightened sensitivity of vagal pulmonary C-fibers. To investigate this possibility, the present study aimed to investigate the effect of a pretreatment with TNFα on the sensitivity of vagal pulmonary afferents in anesthetized mice...
2017: Frontiers in Physiology
https://www.readbyqxmd.com/read/28650915/the-brainstem-network-controlling-blood-pressure-an-important-role-for-pressor-sites-in-the-caudal-medulla-and-cervical-spinal-cord
#17
Michael G Z Ghali
: Although medullary control of blood pressure (BP) has been extensively studied, the contribution of critical regions, such as pressor sites in the caudal medulla and upper cervical spinal cord and the lateral tegmental field, remains controversial and underappreciated. A series of pressor sites caudal to the caudal ventrolateral medulla (CVLM), including the caudal pressor area (CPA) and medullocervical pressor area, play an important role in control of BP. Activation and inhibition of these sites elicits pressor and depressor responses, respectively...
June 24, 2017: Journal of Hypertension
https://www.readbyqxmd.com/read/28640969/control-of-breathing-and-ventilatory-acclimatization-to-hypoxia-in-deer-mice-native-to-high-altitudes
#18
Catherine M Ivy, Graham R Scott
AIM: We compared the control of breathing and heart rate by hypoxia between high- and low-altitude populations of Peromyscus mice, to help elucidate the physiological specializations that help high-altitude natives cope with O2 limitation. METHODS: Deer mice (P. maniculatus) native to high altitude and congeneric mice native to low altitude (P. leucopus) were bred in captivity at sea level. The F1 progeny of each population were raised to adulthood and then acclimated to normoxia or hypobaric hypoxia (12 kPa, simulating hypoxia at ~4300 m) for 5 months...
June 22, 2017: Acta Physiologica
https://www.readbyqxmd.com/read/28637679/characterization-of-ectonucleotidase-expression-in-the-rat-carotid-body-regulation-by-chronic-hypoxia
#19
Shaima Salman, Cathy Vollmer, Grant B McClelland, Colin A Nurse
The carotid body (CB) chemoreflex maintains blood Po2 and Pco2/H(+) homeostasis and displays sensory plasticity during exposure to chronic hypoxia. Purinergic signaling via P1 and P2 receptors plays a pivotal role in shaping the afferent discharge at the sensory synapse containing catecholaminergic chemoreceptor (type I) cells, glial-like type II cells, and sensory (petrosal) nerve endings. However, little is known about the family of ectonucleotidases that control synaptic nucleotide levels. Using quantitative PCR (qPCR), we first compared expression levels of ectonucleoside triphosphate diphosphohydrolases (NTPDases1,2,3,5,6) and ecto-5'-nucleotidase (E5'Nt/CD73) mRNAs in juvenile rat CB vs...
September 1, 2017: American Journal of Physiology. Cell Physiology
https://www.readbyqxmd.com/read/28620058/intermittent-hypercapnic-hypoxia-during-sleep-does-not-induce-ventilatory-long-term-facilitation-in-healthy-males
#20
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
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