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https://www.readbyqxmd.com/read/29750475/effects-of-losartan-and-allopurinol-on-cardiorespiratory-regulation-in-obstructive-sleep-apnoea
#1
Barbara J Morgan, Mihaela Teodorescu, David F Pegelow, Emily R Jackson, Devin L Schneider, David T Plante, James P Gapinski, Scott J Hetzel, John M Dopp
Chemoreflex sensitization produced by chronic intermittent hypoxia (CIH) in rats is attenuated by angiotensin II type 1 receptor (AT1 R) blockade. AT1 R blockade and xanthine oxidase inhibition both ameliorate CIH-induced endothelial dysfunction. We hypothesized treatment with losartan and allopurinol would reduce chemoreflex sensitivity and improve hypoxic vasodilation in patients with obstructive sleep apnoea (OSA). Eighty-six hypertensive patients with apnoea-hypopnoea index ≥25 events/hr and no other cardiovascular, pulmonary, renal, or metabolic disease were randomly assigned to receive allopurinol, losartan, or placebo for 6 weeks...
May 11, 2018: Experimental Physiology
https://www.readbyqxmd.com/read/29698108/capsaicin-based-analgesic-balm-attenuates-the-skeletal-muscle-metaboreflex-in-healthy-humans
#2
Lauro C Vianna, Igor A Fernandes, Thales C Barbosa, André L Teixeira, Antonio Claudio Lucas da Nóbrega
The exercise pressor reflex (EPR) is comprised from group III and IV skeletal muscle afferents and is one of the principal mediators of the cardiovascular response to exercise. In animals, capsaicin-based analgesic balm (CAP) attenuates the pressor response to muscle contraction, indicating the transient receptor potential vanilloid 1 (TRPv1) receptor (localized on the group IV afferent neuron) as an important mediator of the EPR. However, whether these findings can be extrapolated to humans remain unknown...
April 26, 2018: Journal of Applied Physiology
https://www.readbyqxmd.com/read/29676840/behavioral-morphological-and-electrophysiological-assessment-of-the-effects-of-type-2-diabetes-mellitus-on-large-and-small-nerve-fibers-in-zucker-diabetic-fatty-rat-zucker-lean-and-wistar-rats
#3
E Garcia-Perez, T Schönberger, M Sumalla, B Stierstorfer, R Solà, H Doods, J Serra, N Gorodetskaya
BACKGROUND: Peripheral neuropathy is a common complication in type 2 diabetes mellitus (T2DM). The most common presentation is in the form of a distal axonal sensory-motor polyneuropathy that involves large and small nerve fibers in variable proportion. METHODS: Zucker Diabetic Fatty rats (ZDF), Zucker Lean (ZL) and Wistar Han (WH) rats were used to asses the behavioral, morphological and electrophysiological effects that T2DM have on peripheral large and small nerve fibers of 6-40 week-old rats...
April 20, 2018: European Journal of Pain: EJP
https://www.readbyqxmd.com/read/29668385/functional-properties-of-human-muscle-spindles
#4
Vaughan G Macefield, Thomas P Knellwolf
Muscle spindles are ubiquitous encapsulated mechanoreceptors found in most mammalian muscles. There are two types of endings, primary and secondary, and both are sensitive to changes in muscle length and velocity, with the primary endings having a greater dynamic sensitivity. Unlike other mechanoreceptors in the somatosensory system, muscle spindles are unique in possessing motor innervation, via  motoneurons (fusimotor neurons), that control their sensitivity to stretch. Much of what we know about human muscles spindles comes from studying the behavior of their afferents via intraneural microelectrodes (microneurography) inserted into accessible peripheral nerves...
April 18, 2018: Journal of Neurophysiology
https://www.readbyqxmd.com/read/29659054/tuning-in-c-nociceptors-to-reveal-mechanisms-in-chronic-neuropathic-pain
#5
Robin Jonas, Barbara Namer, Lenka Stockinger, Kim Chisholm, Mark Schnakenberg, Gunther Landmann, Mateusz Kucharczyk, Christoph Konrad, Roland Schmidt, Richard Carr, Stephen McMahon, Martin Schmelz, Roman Rukwied
OBJECTIVE: Develop and validate a low-intensity sinusoidal electrical stimulation paradigm to preferentially activate C-fibers in human skin. METHODS: Sinusoidal transcutaneous stimulation (4 Hz) was assessed psychophysically in healthy volunteers (n=14) and neuropathic pain patients (n=9). Pursuing laser Doppler imaging and single nociceptor recordings in vivo in humans (microneurography) and pigs confirmed the activation of "silent" C-nociceptors. Synchronized C-fiber compound action potentials were evoked in isolated human nerve fascicles in vitro...
April 16, 2018: Annals of Neurology
https://www.readbyqxmd.com/read/29605303/inverse-association-between-sympathetic-nervous-system-activity-and-bone-mass-in-middle-aged-overweight-individuals
#6
Elisabeth Lambert, Sarah Phillips, Ainura Tursunalieva, Nina Eikelis, Carolina Sari, John Dixon, Nora Straznicky, Mariee Grima, Markus Schlaich, Gavin Lambert
BACKGROUND/PURPOSE: Sympathetic nervous system activation in obesity is associated with impaired cardiovascular and metabolic function. Animal studies have shown a direct link between sympathetic nervous activation and bone health but little is known about this link in humans. This study examined whether sympathetic activation may impact bone health in overweight adults. METHODS: This cross sectional study included 96 overweight or obese middle-aged adults (51 males, mean body mass index: 32...
March 29, 2018: Bone
https://www.readbyqxmd.com/read/29551562/low-frequency-stimulation-of-silent-nociceptors-induces-secondary-mechanical-hyperalgesia-in-human-skin
#7
Katja Sauerstein, Jan Liebelt, Barbara Namer, Roland Schmidt, Roman Rukwied, Martin Schmelz
Secondary mechanical hyperalgesia to punctate mechanical stimuli and light touch (allodynia) are prominent symptoms in neuropathic pain states. In a combined microneurographic and psychophysical study, we investigated the role of mechano-insensitive (silent) nociceptors regarding induction. Electrical thresholds of mechano-sensitive and silent nociceptors were assessed by microneurography with two closely spaced intracutaneous electrodes (i.c.) and a transcutaneous configuration (t.c.) in the foot dorsum. For t...
March 15, 2018: Neuroscience
https://www.readbyqxmd.com/read/29528117/the-carotid-chemoreceptor-contributes-to-the-elevated-arterial-stiffness-and-vasoconstrictor-outflow-in-copd
#8
Devin B Phillips, Craig D Steinback, Sophie É Collins, Desi P Fuhr, Tracey L Bryan, Eric Y L Wong, Vincent Tedjasaputra, Mohit Bhutani, Michael K Stickland
COPD patients have increased central arterial stiffness and muscle sympathetic nervous activity (MSNA), both of which contribute to cardiovascular (CV) dysfunction and increased CV risk. Previous work suggests that COPD patients have elevated carotid chemoreceptor (CC) activity/sensitivity, which may contribute to the elevated MSNA and arterial stiffness. Accordingly, the effect of CC inhibition on central arterial stiffness, MSNA and CV function at rest in COPD patients was examined in a randomized placebo-controlled study...
March 12, 2018: Journal of Physiology
https://www.readbyqxmd.com/read/29488839/pharmacological-assessment-of-the-contribution-of-the-arterial-baroreflex-to-sympathetic-discharge-patterns-in-healthy-humans
#9
Jacqueline K Limberg, Elizabeth P Ott, Walter W Holbein, Sarah Elizabeth Baker, Timothy B Curry, Wayne T Nicholson, Michael J Joyner, J Kevin Shoemaker
To study how changes in baroreceptor afferent activity affect patterns of sympathetic neural activation, we manipulated arterial blood pressure using intravenous nitroprusside (NTP) and phenylephrine (PE) and measured action potential (AP) patterns with wavelet-based methodology. We hypothesized: 1) Baroreflex unloading (NTP) would increase firing of low-threshold axons and recruitment of latent axons, and 2) Baroreflex loading (PE) would decrease firing of low-threshold axons. Heart rate (HR, ECG), arterial blood pressure (BP, brachial catheter), and muscle sympathetic nerve activity (MSNA, microneurography of the peroneal nerve) were measured at baseline and during steady-state systemic, intravenous NTP (0...
February 28, 2018: Journal of Neurophysiology
https://www.readbyqxmd.com/read/29472865/intracranial-pressure-is-a-determinant-of-sympathetic-activity
#10
Eric A Schmidt, Fabien Despas, Anne Pavy-Le Traon, Zofia Czosnyka, John D Pickard, Kamal Rahmouni, Atul Pathak, Jean M Senard
Intracranial pressure (ICP) is the pressure within the cranium . ICP rise compresses brain vessels and reduces cerebral blood delivery. Massive ICP rise leads to cerebral ischemia, but it is also known to produce hypertension, bradycardia and respiratory irregularities due to a sympatho-adrenal mechanism termed Cushing response. One still unresolved question is whether the Cushing response is a non-synaptic acute brainstem ischemic mechanism or part of a larger physiological reflex for arterial blood pressure control and homeostasis regulation...
2018: Frontiers in Physiology
https://www.readbyqxmd.com/read/29412776/fifty-years-of-microneurography-learning-the-language-of-the-peripheral-sympathetic-nervous-system-in-humans
#11
J Kevin Shoemaker, Stephen A Klassen, Mark B Badrov, Paul J Fadel
As a primary component of homeostasis, the sympathetic nervous system enables rapid adjustments to stress through its ability to communicate messages among organs and cause targeted and graded end organ responses. Key in this communication model is the pattern of neural signals emanating from the central to peripheral components of the sympathetic nervous system. But what is the communication strategy employed in peripheral sympathetic nerve activity (SNA)? Can we develop and interpret the system of coding in SNA that improves our understanding of the neural control of the circulation? In 1968, Hagbarth and Vallbo (Hagbarth KE, Vallbo AB...
May 1, 2018: Journal of Neurophysiology
https://www.readbyqxmd.com/read/29378730/evidence-for-pressure-independent-sympathetic-modulation-of-central-pulse-wave-velocity
#12
Massimo Nardone, Anthony V Incognito, Philip J Millar
BACKGROUND: Whether the sympathetic nervous system can directly alter central aortic stiffness remains controversial, mainly because of the difficulty in experimentally augmenting peripheral vasoconstrictor activity without changing blood pressure. METHODS AND RESULTS: To address this limitation, we utilized low-level cardiopulmonary baroreflex loading and unloading shown previously to alter sympathetic outflow without evoking parallel hemodynamic modulation. Blood pressure and carotid-femoral aortic pulse wave velocity (cf-PWV) were measured in 32 healthy participants (24±2 years; women: n=15) before and during 12-minute applications of low-level lower body negative pressure; -7 mm Hg) and lower body positive pressure; +7 mm Hg), applied in a random order...
January 29, 2018: Journal of the American Heart Association
https://www.readbyqxmd.com/read/29336094/sympathetic-neurovascular-regulation-during-pregnancy-a-longitudinal-case-series-study
#13
Laura M Reyes, Charlotte W Usselman, Rachel J Skow, Nisha Charkoudian, Jeffery S Staab, Margie H Davenport, Craig D Steinback
NEW FINDINGS: What is the main observation in this case? The main observation of this case report is that during pregnancy there is a progressive sympatho-excitation in basal conditions and under stress, which is offset by a concurrent reduction in neurovascular transduction. Strong correlations between autonomic nervous system activity and sex hormones (oestrogen and progesterone), vasopressin and aldosterone were found. What insights does it reveal? Our findings suggest that hormonal surges might be associated with central sympathetic activation...
March 1, 2018: Experimental Physiology
https://www.readbyqxmd.com/read/29334157/elevated-sympathetic-vasomotor-outflow-in-response-to-increased-inspiratory-muscle-activity-during-exercise-is-less-in-young-women-compared-with-men
#14
Keisho Katayama, Joshua R Smith, Kanako Goto, Kaori Shimizu, Mitsuru Saito, Koji Ishida, Teruhiko Koike, Satoshi Iwase, Craig A Harms
NEW FINDINGS: What is the central question of this study? Premenopausal women have an attenuated inspiratory muscle metaboreflex-induced increase in arterial blood pressure compared with men. It is unclear whether sympathetic vasomotor outflow during dynamic exercise with increased inspiratory muscle activation is less in young women than in men. What is the main finding and its importance? The magnitude of increased sympathetic vasomotor outflow during leg cycling with inspiratory resistance was smaller in women than in men...
April 1, 2018: Experimental Physiology
https://www.readbyqxmd.com/read/29300244/sympathetic-and-baroreflex-abnormalities-in-the-uncomplicated-prediabetic-state
#15
Raffaella Dell'Oro, Fosca Quarti Trevano, Pierluigi Gamba, Claudia Ciuffarella, Gino Seravalle, Giuseppe Mancia, Guido Grassi
BACKGROUND: Neurogenic abnormalities characterize overt diabetic state. However, how early is their appearance in the clinical course of the disease is unclear. METHODS: In 26 normotensive and normoweight prediabetic patients, aged 45.2 ± 3.2 years (mean ± SEM), we assessed efferent postganglionic muscle sympathetic nerve traffic (MSNA, microneurography), spontaneous baroreflex sensitivity, and a number of hemodynamic and metabolic variables, including homeostatic model assessment (HOMA) index...
May 2018: Journal of Hypertension
https://www.readbyqxmd.com/read/29212669/long-duration-bed-rest-modifies-sympathetic-neural-recruitment-strategies-in-males-and-females
#16
Stephen A Klassen, Steven De Abreu, Danielle K Greaves, Derek S Kimmerly, Philippe Arbeille, Pierre Denise, Richard L Hughson, Hervé Normand, J Kevin Shoemaker
To understand the impact of physical deconditioning with head-down tilt bed rest (HDBR) on the malleability of sympathetic discharge patterns, we studied a) baseline integrated muscle sympathetic nerve activity (MSNA; microneurography) from 13 females participating in the WISE-2005 60-day HDBR study (Female, retrospective analysis), b) integrated MSNA and multi-unit action potential (AP) analysis in 13 males (Male) performed on data collected at baseline and during physiological stress imposed by end-inspiratory apnea, in a new 60-day HDBR study, and c) a repeatability study (Control, n = 6, retrospective analysis, 4 weeks between tests)...
December 6, 2017: Journal of Applied Physiology
https://www.readbyqxmd.com/read/29206785/three-weeks-of-overload-training-increases-resting-muscle-sympathetic-activity
#17
Alexandra M Coates, Anthony V Incognito, Jeremy D Seed, Connor J Doherty, Philip J Millar, Jamie F Burr
PURPOSE: Overload training is hypothesized to alter autonomic regulation, though interpretations using indirect measures of heart rate variability are conflicting. The aim of the present study was to examine the effects of overload training on muscle sympathetic nerve activity (MSNA), a direct measure of central sympathetic outflow, in recreational endurance athletes. METHODS: Measurements of heart rate variability, cardiac baroreflex sensitivity (BRS), MSNA (microneurography), and sympathetic BRS were obtained in seventeen healthy triathletes and cyclists after 1-week of reduced training (baseline) and following 3-weeks of either regular (CON, n=7) or overload (OL, n=10) training...
December 2, 2017: Medicine and Science in Sports and Exercise
https://www.readbyqxmd.com/read/29070505/interindividual-variability-in-muscle-sympathetic-responses-to-static-handgrip-in-young-men-evidence-for-sympathetic-responder-types
#18
Anthony V Incognito, Connor J Doherty, Jordan B Lee, Matthew J Burns, Philip J Millar
Negative and positive muscle sympathetic nerve activity (MSNA) responders have been observed during mental stress. We hypothesized that similar MSNA response patterns could be identified during the first minute of static handgrip and contribute to the interindividual variability throughout exercise. Supine measurements of multiunit MSNA (microneurography) and continuous blood pressure (Finometer) were recorded in 29 young healthy men during the first (HG1) and second (HG2) minute of static handgrip (30% maximal voluntary contraction) and subsequent postexercise circulatory occlusion (PECO)...
January 1, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29057701/the-relationship-between-the-sensory-responses-to-ankle-joint-loading-and-corticomotor-excitability
#19
Alan R Needle, Jochen Baumeister, William B Farquhar, Jody L Greaney, Jill S Higginson, Thomas W Kaminski, C Buz Swanik
PURPOSE: Maintaining joint stability is dependent on the ability of the nervous system to sense and react to potentially injurious loads. In attempts to understand the neurophysiologic mechanisms underlying joint stability, this afferent and efferent activity has been quantified separately at the cortical, segmental and peripheral levels using various electrophysiologic techniques in vivo. However, no studies have attempted to quantify sensory and motor activation at multiple levels of the nervous system in a single subset, to understand potential adaptations for optimizing joint stability...
May 2018: International Journal of Neuroscience
https://www.readbyqxmd.com/read/29040222/neurovascular-response-during-exercise-and-mental-stress-in-anabolic-steroid-users
#20
Rafael Armani Porello, Marcelo Rodrigues Dos Santos, Francis Ribeiro DE Souza, Guilherme Wesley Peixoto DA Fonseca, Ana Luiza Carrari Sayegh, Tiago Franco DE Oliveira, César Abreu Akiho, Maurício Yonamine, Rosa Maria Rodrigues Pereira, Carlos Eduardo Negrão, Maria-Janieire DE Nazaré Nunes Alves
PURPOSE: Increased resting muscle sympathetic nerve activity (MSNA) and lower forearm blood flow (FBF) were observed in young men who use anabolic androgenic steroids (AAS). However, the response of MSNA and FBF in AAS users triggered by muscle mechanoreflex and central command has never been tested. In addition, we evaluated the blood pressure (BP) and heart rate (HR) responses during these maneuvers. METHODS: Nineteen AAS users (AASU) 31 ± 6 yr of age and 18 AAS nonusers (AASNU) 29 ± 4 yr of age were recruited...
March 2018: Medicine and Science in Sports and Exercise
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