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Experimental Physiology

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https://www.readbyqxmd.com/read/28714270/resistive-breathing-and-respiratory-muscle-fatigue-a-load-of-concern-just-expired
#1
Ken D O'Halloran
Pulmonary ventilation is a cyclical process of inhalation and exhalation of air providing dynamic tidal exchange between alveolar gas-exchanging units of the lungs and the external environment. This article is protected by copyright. All rights reserved.
July 17, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28714073/sex-differences-in-angii-stimulated-fluid-intake
#2
Jessica Santollo
Sex has a clear effect on the renin-angiotensin-aldosterone system. While sex differences in the pressor response to angiotensin II (AngII) are well established, understanding sex differences in the fluid intake response to AngII are clouded by conflicting reports. Here we suggest that accounting for differences in body weights contribute to the discrepancies in the literature. Our recent findings demonstrate that body weight influences AngII-stimulated water intake under certain conditions in males, but not females...
July 17, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28699679/one-session-of-remote-ischemic-preconditioning-does-not-improve-vascular-function-in-acute-normobaric-and-chronic-hypobaric-hypoxia
#3
Mathew G Rieger, Ryan L Hoiland, Joshua C Tremblay, Mike Stembridge, Anthony R Bain, Daniela Flück, Prajan Subedi, James D Anholm, Philip N Ainslie
Application of repeated short duration bouts of ischemia to the limbs, termed remote ischemic preconditioning (RIPC), is a novel technique that may have protective effects on vascular function during hypoxic exposures. In separate parallel-design studies, at sea-level (SL; n = 16), and after 8-12 days at high-altitude (HA; n = 12; White Mountain, 3800 m), participants underwent either a sham protocol or one session of 4 × 5 minutes of dual-thigh cuff occlusion with 5 minutes recovery. Brachial artery flow-mediated dilation (FMD; ultrasound), pulmonary artery systolic pressure (PASP; echocardiography), and internal carotid artery flow (ICA; ultrasound) were measured at SL in normoxia and isocapnic hypoxia [end-tidal PO₂ (PETO₂) maintained to 50 mmHg], and during normal breathing at HA...
July 12, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28681979/trpv1-channels-in-human-skeletal-muscle-feed-arteries-implications-for-vascular-function
#4
Stephen J Ives, Song Young Park, Oh Sung Kwon, Jayson R Gifford, Robert H I Andtbacka, John R Hyngstrom, Russell S Richardson
To examine the role of transient receptor potential vanilloid type 1 (TRPV1 ) ion channel in the vascular function of human skeletal muscle feed arteries (SMFAs) and if activation of this heat-sensitive receptor could be involved in modulating vascular function, SMFAs from 16 humans (63 ± 5, 41-89 yrs) were studied using wire myography with capsaicin (TRPV1 agonist) and without (control). Specifically, phenylephrine (PE, α1 -adrenergic receptor agonist), dexemedetomidine (DEX, α2 -adrenergic receptor agonist), acetylcholine (ACh), and sodium nitroprusside (SNP) concentration response curves (CRCs) were performed to assess the role of TRPV1 channels in α-receptor-mediated vasocontraction as well as endothelium-dependent and independent vasorelaxation, respectively...
July 6, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28678393/catechin-attenuates-traumatic-brain-injury-induced-impairments-of-blood-brain-barrier-damage-and-improve-longer-term-neurological-outcomes-in-rats
#5
Zhixian Jiang, Jinning Zhang, Yonghui Cai, Jiaxin Huang, Lingtong You
Traumatic brain injury (TBI), resulting from external force on the head usually lead to long-term deficits in motor and cognitive functions. Catechin has shown neuroprotective effect in neurodegenerative diseases and ischemia models. The present study therefore investigated the potential neuroprotective effects of catechin after TBI and explored the underlying mechanisms. Male rats were subjected to controlled cortical impact injury and then treated with catechin. Brain damages, motor and cognitive functions, blood-brain barrier (BBB) integrity and neuro-inflammation were examined...
July 5, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28677340/rapid-onset-pressor-response-to-exercise-in-young-women-with-a-family-history-of-hypertension
#6
Evan L Matthews, Jody L Greaney, Megan M Wenner
Hypertensive adults demonstrate atypical increases in blood pressure (BP) and muscle sympathetic nerve activity (MSNA) at the immediate onset of static muscle contraction. However, it is unknown whether these abnormal responses occur in young, otherwise healthy adults at risk for developing future disease, such as those with a family history of hypertension (+FH). We tested the hypothesis that +FH young women have exaggerated increases in BP and MSNA at the onset of static muscle contraction compared to those without a family history of hypertension (-FH)...
July 5, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28675564/activation-of-serotonergic-neurons-in-the-medullary-caudal-raphe-shortens-the-laryngeal-chemoreflex-in-anaesthetized-neonatal-rats
#7
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/28671737/the-phase-response-and-state-space-of-slow-wave-contractions-in-the-small-intestine
#8
Sean P Parsons, Jan D Huizinga
The interstitial cells of Cajal (ICC) generate electrical oscillations in the gut. Synchronisation of the ICC population is required for generation of coherent electrical waves ("slow waves") that cause muscular contraction and thereby move gut content. The phase response curve (PRC) is an experimental measure of the dynamical rules governing a population of oscillators, that determine their synchrony, and gives an experimental window onto the state space of the oscillator, its dynamical landscape. We measured the PRC of slow wave contractions in the mouse small intestine by the novel combination of diameter mapping and single pulse electrical field stimulation...
July 3, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28671307/cutaneous-microvascular-perfusion-responses-to-insulin-iontophoresis-are-differentially-affected-by-insulin-resistance-after-spinal-cord-injury
#9
Michael F La Fountaine, Christopher M Cirnigliaro, Frank Azarello, Joshua C Hobson, Oriana Tascione, Kirsten N Swonger, Trevor Dyson-Hudson, William A Bauman
Endothelial-mediated mechanisms that regulate skin blood flow may play an integral role in optimizing skin perfusion in vascular beds with sympathetic nervous system vasomotor impairment, such as in spinal cord injury (SCI). Insulin is a vasoactive hormone and second messenger of nitric oxide that facilitates endothelial-mediated dilatation. The effects of insulin resistance (IR) on sublesional cutaneous perfusion responses to insulin provocation have yet to be described in persons with SCI. Persons with SCI and an able-bodied (AB) cohort were divided into subgroups based upon fasting plasma insulin (FPI) concentration cut-offs for IR (≥13...
July 3, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28665499/restoration-of-pharyngeal-dilator-muscle-force-in-dystrophin-deficient-mdx-mice-following-co-treatment-with-neutralising-il-6-receptor-antibodies-and-urocortin-2
#10
David P Burns, Jane Rowland, Leonie Canavan, Kevin H Murphy, Molly Brannock, Dervla O'Malley, Ken D O'Halloran, Deirdre Edge
The mdx mouse model of Duchenne muscular dystrophy (DMD) shows evidence of impaired pharyngeal dilator muscle function. We hypothesised that inflammatory and stress-related factors are implicated in airway dilator muscle dysfunction. Six week old mdx (n = 26) and wild-type (WT; n = 26) mice received either saline (0.9% w v(-1) ) or a co-administration of neutralising IL-6 receptor antibodies (xIL-6R; 0.2 mg kg(-1) ) and corticotrophin releasing factor receptor 2 agonist (Urocortin 2; 30 μg kg(-1) ) over 2 weeks...
June 30, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28646592/influence-of-inspiratory-resistive-loading-on-expiratory-muscle-fatigue-in-healthy-humans
#11
Carli M Peters, Joseph F Welch, Paolo B Dominelli, Yannick Molgat-Seon, Lee M Romer, Donald C McKenzie, A William Sheel
Expiratory resistive loading elicits inspiratory as well as expiratory muscle fatigue, suggesting parallel co-activation of the inspiratory muscles during expiration. It is unknown whether the expiratory muscles are similarly co-activated to the point of fatigue during inspiratory resistive loading (IRL). The purpose of this study was to determine whether IRL elicits expiratory as well as inspiratory muscle fatigue. Healthy male subjects (n = 9) underwent isocapnic IRL (60% maximal inspiratory pressure, 15 breaths∙min(-1) , 0...
June 24, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28639723/changes-in-the-inspiratory-pattern-contribute-to-modulate-the-sympathetic-activity-in-sino-aortic-denervated-rats
#12
Mateus R Amorim, Leni G H Bonagamba, George M P R Souza, Davi J A Moraes, Benedito H Machado
The activity of pre-sympathetic neurons is under respiratory modulation and changes in the central respiratory network may impact on the baseline sympathetic activity and mean arterial pressure (MAP). It is well known that after baroreceptor afferents removal (sino-aortic denervation, SAD), rats present an unexpected normal levels of MAP. We hypothesized that changes in the respiratory pattern and in the respiratory modulation of the sympathetic activity contribute to keep the sympathetic outflow in a normal range of variation in absence of arterial baroreceptors in rats...
June 22, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28639297/autophagy-activation-not-pgc-1%C3%AE-may-mediate-exercise-induced-improvements-in-glucose-handling-during-diet-induced-obesity
#13
Megan E Rosa-Caldwell, Jacob L Brown, David E Lee, Thomas A Blackwell, Kyle W Turner, Lemuel A Brown, Richard A Perry, Wesley S Haynie, Tyrone A Washington, Nicholas P Greene
Prevalence of glucose intolerance is at alarming levels. Efforts to promote mitochondrial biogenesis through PGC-1α to mitigate glucose intolerance have been controversial. However, physical activity remains a primary means to alleviate the condition. PURPOSE: To determine combined effects of muscle-specific overexpression of PGC-1α and physical activity on glucose handling during diet-induced obesity. METHODS: Wild-type (WT, ∼20) and PGC-1α muscle transgenic (MCK-PGC-1α, ∼20) mice were given Western diet (WD) at 8 wks age and allowed to consume food ab libitum throughout the study...
June 21, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28635124/regular-aerobic-exercise-reduces-endothelin-1-mediated-vasoconstrictor-tone-in-overweight-and-obese-adults
#14
Caitlin A Dow, Brian L Stauffer, Danielle L Brunjes, Jared J Greiner, Christopher A DeSouza
What is the central question of this study? Does aerobic exercise training reduce endothelin-1 (ET-1)-mediated vasoconstrictor tone in overweight/obese adults? And, if so, does lower ET-1 vasoconstriction underlie the exercise-related enhancement in endothelium-dependent vasodilatation in overweight/obese adults? What is the main finding and its importance? Regular aerobic exercise reduces ET-1-mediated vasoconstrictor tone in previously sedentary overweight/obese adults, independent of weight loss. Decreased ET-1 vasoconstriction is an important mechanism underlying the aerobic exercise-induced improvement in endothelium-dependent vasodilator function in overweight/obese adults...
June 20, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28627041/prior-exercise-speeds-pulmonary-oxygen-uptake-kinetics-and-increases-critical-power-during-supine-but-not-upright-cycling
#15
Richie P Goulding, Denise M Roche, Simon Marwood
Critical power (CP) is a fundamental parameter defining high-intensity exercise tolerance and is related to the time constant of phase II pulmonary oxygen uptake kinetics (τV̇O2 ). To test the hypothesis that this relationship is causal we determined the impact of prior exercise ("priming") on CP and τV̇O2 in the upright and supine positions. 17 healthy men were assigned to either upright or supine exercise groups, whereby CP, τV̇O2 and muscle deoxyhaemoglobin kinetics (τ[HHb] ) were determined via constant-power tests to exhaustion at four work-rates with (primed) and without (control) priming exercise at ∼31%Δ...
June 19, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28626963/exercise-training-modulates-the-hepatic-renin-angiotensin-system-in-fructose-fed-rats
#16
Eliete Dalla Corte Frantz, Renata Frauches Medeiros, Isabele Gomes Giori, Juliana Bittencourt Silveira Lima, Thais Bento-Bernardes, Thaiane Gadioli Gaique, Caroline Fernandes-Santos, Tiago Fernandes, Edilamar Menezes Oliveira, Carla Paulo Vieira, Carlos Adam Conte-Junior, Karen Jesus Oliveira, Antonio Claudio Lucas da Nóbrega
The renin-angiotensin system (RAS) has been implicated in the development of metabolic syndrome. We investigated whether the hepatic RAS is modulated by exercise training and if this modulation improves the deleterious effects of fructose overload in rats. Male Wistar rats were divided into (n = 8 each) control (CT), exercise control (CT-Ex), high fructose (HFr) and exercise high fructose (HFr-Ex) groups. Fructose-drinking rats received D-fructose (100 g L(-1) ). After two weeks, CT-Ex and HFr-Ex rats were assigned to a treadmill training protocol at moderate-intensity for eight weeks (60 min day(-1) , four days/week)...
June 19, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28605068/endoplasmic-reticulum-stress-in-the-pathogenesis-of-hypertension
#17
Colin N Young
The endoplasmic reticulum (ER) is a cellular organelle specialized in the synthesis, folding, assembly, and modification of proteins. In situations of increased protein demand, complex signaling pathways, termed the unfolded protein response (UPR), influence a series of cellular feedback loops to strictly control ER function. While initially a compensatory attempt to maintain cellular homeostasis, chronic activation of the UPR, known as ER stress, leads to sustained changes in cellular function. A growing body of literature points to ER stress in diverse cardioregulatory systems, including the brain, kidney and vasculature, as central to the development of hypertension...
June 12, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28597936/the-beneficial-metabolic-effects-of-insulin-sensitizers-are-not-attenuated-by-mitochondrial-pyruvate-carrier-2-hypomorphism
#18
Patrick A Vigueira, Kyle S McCommis, Wesley T Hodges, George G Schweitzer, Serena L Cole, Lalita Oonthonpan, Eric B Taylor, William G McDonald, Rolf F Kletzien, Jerry R Colca, Brian N Finck
What is the central question of this study? The antidiabetic effects of thiazolidinedione (TZD) drugs may be mediated in part by a molecular interaction with the constituent proteins of the mitochondrial pyruvate carrier complex (MPC1 and MPC2). We examined the ability of a mutant mouse strain expressing an N-terminal truncation of MPC2 (Mpc2Δ16 mice) to respond to TZD treatment. What is the main finding and its importance? The response of Mpc2Δ16 mice to TZD treatment was not significantly different from that of wild-type C57BL6/J control animals, suggesting that the 16 N-terminal amino acids of MPC2 are dispensable for the effects of TZD treatment...
June 9, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28594464/do-changes-in-neuromuscular-activation-contribute-to-the-knee-extensor-angle-torque-relationship
#19
Marcel B Lanza, Thomas G Balshaw, Jonathan P Folland
The influence of joint angle on knee extensor neuromuscular activation is unclear due in part due to the diversity of surface electromyography (sEMG) and/or interpolated twitch technique (ITT) methods employed. The aim of the study was to compare neuromuscular activation, using rigorous contemporary sEMG and ITT procedures, during isometric maximal voluntary contractions (iMVC) of the quadriceps femoris (Q) at different knee-joint angles and examine if activation contributes to the angle-torque relationship...
June 8, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28590038/effects-of-estrogen-and-cimicifuga-racemosa-on-the-cardiac-norepinephrine-pathway-of-ovariectomized-rats
#20
Yao Liu, Jing Zhang, Shuya Liu, Wenjuan Wang, Xing Chen, Hai Jiang, Junlei Li, Ke Wang, Wenpei Bai, Haicheng Zhang, Lihua Qin
This study aimed to investigate the effects of estrogen and Cimicifuga racemosa on the stellate ganglion, cardiac norepinephrine pathway, and Ca(2+) /calmodulin-dependent protein kinase II (CaMK II). Forty adult female Sprague Dawley rats were randomly divided into four groups: SHAM, ovariectomized (OVX), ovariectomized with estrogen treatment (E2), and ovariectomized with Cimicifuga racemosa treatment (iCR). After 4 weeks of treatment, norepinephrine (NE) content was determined by high-performance liquid chromatography, and dopamine beta-hydroxylase (DBH) and norepinephrine transporter (NET) expression was detected by immunohistochemistry...
June 7, 2017: Experimental Physiology
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