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Experimental Physiology

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https://www.readbyqxmd.com/read/29052285/fitness-related-differences-in-the-rate-of-whole-body-evaporative-heat-loss-in-exercising-men-are-heat-load-dependent
#1
Dallon T Lamarche, Sean R Notley, Jeffrey C Louie, Martin P Poirier, Glen P Kenny
The effect of aerobic fitness (defined as rate of peak oxygen consumption) on heat loss during exercise is thought to be related to the level of heat stress. However, it remains unclear at what combined exercise and environmental (net) heat load threshold these fitness-related differences occur. To identify this, we assessed whole-body heat exchange (dry and evaporative) by direct calorimetry in young (22 ± 3 years) men matched for physical characteristics with low (Low-fit) (39.8 ± 2.5 mLO2 ·kg(-1) ·min(-1) ), moderate (Mod-fit) (50...
October 20, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/29052280/reappraisal-of-systemic-venous-chemoreceptors-might-they-explain-the-matching-of-breathing-to-metabolic-rate-in-humans
#2
M J Parkes
What is the topic of this review? One of the major unanswered questions in physiology is that of how breathing matches metabolic rate. Venous chemoreceptors seem to have been dismissed since the 1960s. What advances does it highlight? New evidence shows that their apparent dismissal needs reappraisal. The paper on which this depends has more than one interpretation, and another paper obtained the opposite result. Previous search ignored all locations between skeletal muscle and the right heart. Oxygen sensors other than the arterial chemoreceptors do exist...
October 19, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/29034529/reliability-of-muscle-blood-flow-and-oxygen-consumption-response-from-exercise-using-near-infrared-spectroscopy
#3
Adam A Lucero, Gifty Addae, Wayne Lawrence, Beemnet Neway, Daniel P Credeur, James Faulkner, David Rowlands, Lee Stoner
Near-infrared spectroscopy (NIRS), coupled with rapid venous (VO) and arterial occlusions (AO) can be used to non-invasively estimate resting local skeletal muscle blood flow (mBF) and oxygen consumption (mV̇O2 ), respectively. However, the day-to-day reliability of mBF and mV̇O2 responses to stressors such as incremental dynamic exercise has not been established. PURPOSE: To determine the reliability of NIRS derived mBF and mV̇O2 response from incremental dynamic exercise. METHODS: Measurements of mBF and mV̇O2 were collected in the vastus lateralis of twelve healthy, physically active adults [7 m and 5 f; 25 y (SD 6)] over 3 non-consecutive visits within 10 days...
October 16, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/29034524/carotid-chemoreceptor-control-of-muscle-sympathetic-nerve-activity-in-hypobaric-hypoxia
#4
James P Fisher, Daniela Flück, Matthias P Hilty, Carsten Lundby
High altitude hypoxia causes pronounced sympathoexcitation but the underlying mechanisms remain unclear. We tested the hypothesis that intravenous infusion of dopamine to attenuate carotid chemoreceptor responsiveness would reduce muscle sympathetic nerve activity (MSNA) at high altitude. Nine healthy individuals (mean [SD]; 26 [4] yr) were studied at sea level (SL, Zurich) and at high altitude (ALT, 3454 m, 15-17 days after arrival), both while breathing the ambient air and during an acute incremental hypoxia test (8 × 3 min stages, PET O2 90-45 mmHg)...
October 15, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/29024137/do-male-athletes-with-already-high-initial-hemoglobin-mass-benefit-from-live-high-train-low-altitude-training
#5
Anna Hauser, Severin Troesch, Thomas Steiner, Franck Brocherie, Olivier Girard, Jonas J Saugy, Laurent Schmitt, Grégoire P Millet, Jon P Wehrlin
It has been proposed that athletes with high initial values of hemoglobin mass (Hbmass ) will have a lower Hbmass increase in response to 'live high-train low' (LHTL) altitude training. To verify this assumption, the relationship between initial absolute and relative Hbmass values and their respective Hbmass increase following LHTL in male endurance and team-sport athletes was investigated. Overall, 58 male athletes (35 well-trained endurance athletes and 23 elite male field hockey players) undertook an LHTL training camp with similar hypoxic doses (200-230 h)...
October 11, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28987020/cardiac-and-hemodynamic-influence-on-carotid-artery-longitudinal-wall-motion
#6
Jason S Au, Paula A Bochnak, Sydney E Valentino, Jem L Cheng, Eric J Stöhr, Maureen J MacDonald
Carotid artery longitudinal wall motion (CALM) has recently attracted interest as an indicator of arterial health; however, the regulation of CALM is poorly understood. We conducted a series of studies aimed at manipulating pulse pressure (PP), left ventricular (LV) motion, and carotid shear rate, which have been previously suggested to regulate various components of CALM pattern and magnitude. To determine the regulatory influences on CALM, fifteen healthy males (22 ± 2 years) were exposed to three acute interventions: the Serial Subtraction Test (SST), the Cold Pressor Test (CPT), and exposure to sublingual nitroglycerine (NTG)...
October 7, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28986948/the-role-of-the-blood-brain-barrier-in-hypertension
#7
Anthony Setiadi, Willian S Korim, Khalid Elsaafien, Song T Yao
The blood-brain barrier (BBB) is a critical barrier that provides both metabolic and physical protection to an immune-privileged central nervous system. The BBB has been shown to be disrupted in hypertension. This review addresses the importance of the BBB in maintaining homeostasis in the context of diseases related to autonomic dysfunction such as hypertension. We highlight the potentially important roles of the immune system and neurovascular unit in the maintenance of the BBB, whereby dysregulation may lead to autonomic dysfunction in diseases such as heart failure and hypertension...
October 6, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28983981/neurocognitive-performances-of-visuospatial-attention-and-the-correlations-with-metabolic-and-inflammatory-biomarkers-in-adults-with-obesity
#8
Chia-Liang Tsai, Tsang-Hai Huang, Meng-Che Tsai
The purposes of the present study were to explore the neurophysiological mechanism of visuospatial attention deficits in the adults with obesity, and to examine the relationships between neurocognitive (neuropsychological and neurophysiological) performances and the biochemical markers. Thirty adults with obesity and 30 healthy-weight controls, categorized by body mass index and %fat as measured with dual-energy X-ray absorptiometry, completed a fasting blood draw and performed a visuospatial attention paradigm with concomitant electrophysiological recording...
October 5, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28971566/extracellular-cl-regulates-electrical-slow-waves-and-setting-of-smooth-muscle-membrane-potential-by-interstitial-cells-of-cajal-in-mouse-jejunum
#9
Siva Arumugam Saravanaperumal, Simon J Gibbons, John Malysz, Lei Sha, David R Linden, Joseph H Szurszewski, Gianrico Farrugia
Intracellular Cl(-) homeostasis is regulated by anion-permeable channels and transporters and contributes to excitability of many cell types including smooth muscle and interstitial cells of Cajal (ICC) . Our aims were to investigate the effects on electrical activity in mouse jejunal muscle strips, of substituting extracellular Cl(-) (Cl(-)o ) with the impermeant anions, gluconate and isethionate. On reducing Cl(-)o , effects were observed on electrical slow waves with small effects on smooth muscle membrane voltage (Em )...
October 3, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28960529/pro-arrhythmic-atrial-phenotypes-in-incrementally-paced-murine-pgc1%C3%AE-hearts-effects-of-age
#10
Haseeb Valli, Shiraz Ahmad, James A Fraser, Kamalan Jeevaratnam, Christopher L-H Huang
Atrial arrhythmias, most commonly manifesting as atrial fibrillation (AF), represent a major clinical problem. AF incidences increase with both age and conditions associated with energetic dysfunction. Atrial arrhythmic phenotypes were compared in young (12-16 week) and aged (>52 week), WT and peroxisome proliferator receptor gamma co-activator 1β-deficient (Pgc-1β(-/-) ), Langendorff-perfused hearts, previously used to model mitochondrial energetic disorder. Electrophysiological explorations were performed using simultaneous whole-heart electrocardiogram and intracellular atrial action potential (AP) recordings...
September 27, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28944982/evaluation-of-inos-inhibition-on-kidney-function-and-structure-in-high-fat-diet-induced-kidney-disease
#11
Blanche Martin, Nathalie Caron, Inès Jadot, Vanessa Colombaro, Gabrielle Federici, Clara Depommier, Anne-Émilie Declèves
BACKGROUND: Central obesity is related to caloric excess promoting deleterious cellular responses in targeted organs. Nitric oxide (NO) has been determined as a key player in the pathogenesis of metabolic diseases. Here, we investigated the implication of inducible NO synthase (iNOS) in the development of obesity-induced kidney disease. MATERIALS AND METHODS: C57Bl/6 male mice were randomized to a low-fat diet (LFD) or a high-fat diet (HFD) and treated with L-NIL, a specific iNOS inhibitor for 16 weeks...
September 25, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28940861/intrarenal-mas-and-at1-receptors-play-a-role-in-mediating-the-excretory-actions-of-renal-interstitial-angiotensin-1-7-infusion-in-anaesthetized-rats
#12
Julie O'Neill, Vincent Healy, Edward J Johns
We investigated whether Angiotensin (1-7) induced renal haemodynamic and excretory actions were solely dependent upon intra-renal Mas receptor activation or required functional AT1 receptors. The renin-angiotensin system (RAS) was enhanced by manipulating dietary sodium intake in anaesthetized rats. Angiotensin (1-7) and AT1 and Mas receptor antagonists were infused into the kidney at the cortico-medullary border Mas receptor expression was measured in the kidney. Mean arterial pressure (MAP), urine flow (UF) and fractional sodium excretion (FENa) were 93{plus minus}4 mmHg, 46...
September 21, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28940693/hyperbaric-oxygenation-and-20-hete-inhibition-reduce-stroke-volume-in-female-diabetic-sprague-dawley-rats
#13
Mihael Mišir, Marija Renić, Sanja Novak, Martina Mihalj, Anita Ćosić, Monika Vesel, Ines Drenjančević
We evaluated the effects of acute and repetitive hyperbaric oxygenation (HBO2 ), 20-HETE inhibition by N-hydroxy-N'-(4-butyl-2methylphenyl)-formamidine (HET0016) and their combinations on experimental stroke outcomes. Streptozotocin-induced type-1 diabetic Sprague-Dawley female rats (N = 42, N = 7/group), were subjected to 30' transient middle cerebral artery occlusion (t-MCAO) / reperfusion and divided in following groups; (a) Control group, without treatment; and groups exposed to: (b) HBO2 ; (c) multiple HBO2 (HBO2 immediately and second exposure 12 h after t-MCAO); (d) HET0016 pretreatment (1 mg kg(-1) /3 days prior to t-MCAO) combined with HBO2 after t-MCAO; (e) HET0016 treatment (1 h before, during and for 6 hours after t-MCAO); and (f) HET0016 treatment followed by HBO2 after t-MCAO...
September 21, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28940594/characteristics-of-bioelectrical-activity-of-oviducts-and-uterus-during-early-pregnancy-in-sows-recorded-by-telemetry-method
#14
Bartosz Pawlinski, Malgorzata Domino, Romuald Zabielski, Katarzyna Siewruk, Malgorzata Polanska-Plachta, Zdzislaw Gajewski
The aim of the present study was to record the myoelectric activity of the reproduction tract in sows during the estrous phase and the early pregnancy period via telemetry recording system. In a total of eight non-pregnant pigs, the bioelectrical activity was recorded through three silicone electrodes sutured on the oviduct (isthmus and ampulla) and the uterine horn. Blood samples were collected to monitor the levels of progesterone (P4) and luteinizing hormone (LH). The estrous cycle was synchronized with eCG and hCG and the animals were subjected to artificial insemination (AI)...
September 21, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28940638/does-l-citrulline-supplementation-improve-exercise-blood-flow-in-older-adults
#15
Joaquin U Gonzales, Andrea Raymond, John Ashley, Youngdeok Kim
What is the central question of this study? Does short-term supplementation with l-citrulline in order to increase l-arginine improve exercise blood flow and peripheral dilatation responses to exercise in older adults? What is the main finding and its importance? l-Citrulline increased femoral blood flow by 11% and vascular conductance by 14% during lower-limb exercise in older men, whereas no changes were observed in older women. This modest improvement in bulk muscle blood flow in older men has implications for altering muscle metabolism that may result in enhanced exercise tolerance in older adults...
September 20, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28929630/muscle-length-matters-new-insights-into-the-neural-control-of-lengthening-muscle-actions-of-the-knee-extensors
#16
Martin Behrens
Every movement of the human organism requires an interaction of the central nervous system and skeletal muscles to generate muscle actions and thereby joint torques. This article is protected by copyright. All rights reserved.
September 20, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28929535/extracellular-acidosis-selectively-inhibits-pharmacomechanical-coupling-induced-by-carbachol-in-strips-of-rat-gastric-fundus
#17
Daniel Maia Nogueira de Oliveira, Francisco José Batista-Lima, Emanuella Carvalho Feitosa, Alexandre Havt, Moisés Tolentino Bento da Silva, Armênio Aguiar Dos Santos, Pedro Jorge Caldas Magalhães
Acute acidosis that results from short-term exercise delays gastric emptying in rats and decreases the responsiveness to carbachol in gastric fundus strips. The regulation of cytosolic Ca(2+) levels appears to be a mechanism of action of acidosis. The present study investigated the way in which acidosis interferes with gastric smooth muscle contractions. Rat gastric fundus isolated strips at pH 6.0 presented a lower magnitude of carbachol-induced contractions compared with preparations at pH 7.4. This lower magnitude was absent in carbachol-stimulated duodenum and KCl-stimulated gastric fundus strips...
September 19, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28925529/cerebrovascular-response-to-the-cold-pressor-test-the-critical-role-of-carbon-dioxide
#18
Michael M Tymko, Thijs P Kerstens, Kevin W Wildfong, Philip N Ainslie
In addition to increasing sympathetic nervous activity, blood pressure, and cerebral blood flow (CBF), the cold pressor test (CPT) stimulates pain receptors, which may increase ventilation above metabolic demand; this response likely reduces the partial pressure of end-tidal carbon dioxide (PET CO2 ), and will attenuate elevations in CBF. We hypothesized: (1) CPT would elicit hyperventilation, effectively lowering PET CO2 ; (2) the CBF response will be elevated during an isocapnic (controlled PET CO2 ), compared to a poikilocapnic CPT (uncontrolled PET CO2 ); (3) In response to CPT, the common carotid artery (CCA) will vasodilatate, while the internal carotid artery (ICA) will remain unchanged to help regulate CBF...
September 19, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28921743/exercise-training-dose-differentially-alters-muscle-and-heart-capillary-density-and-metabolic-functions-in-an-obese-rat-with-metabolic-syndrome
#19
Marcus Vinicius Machado, Aline Bomfim Vieira, Fabiana Gomes da Conceição, Alessandro Rodrigues Nascimento, Antonio Claudio Lucas da Nóbrega, Eduardo Tibirica
We evaluated the effect of frequency, duration and intensity of exercise training on metabolic parameters and structural capillary density in obese rats with metabolic syndrome (MS). Wistar-Kyoto rats were fed a either standard commercial diet (CON) or high-fat diet (HFD). Animals that received the HFD were randomly separated into either a sedentary (SED) group or 8 different exercise groups that varied by the frequency, duration and intensity of training. After 12 weeks of aerobic exercise training, body composition, aerobic capacity, hemodynamic variables, metabolic parameters and capillary density in the heart and skeletal muscle were evaluated...
September 17, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28901662/acute-hypoxemia-and-vascular-function-in-healthy-humans
#20
N C S Lewis, A R Bain, K W Wildfong, D J Green, P N Ainslie
Endothelium-dependent flow mediated dilation (FMD) and endothelium-independent dilation (GTN) are impaired at high altitude (5050 m), and FMD is impaired following acute exposure (<60-minutes) to normobaric hypoxia equivalent to ∼5050 m (∼FI O2  = 0.11). Whether glyceryl trinitrate (GTN)-induced dilation is impaired acutely, and whether FMD is impaired during milder hypoxia is unknown. Therefore, we assessed brachial FMD at baseline and following 30-minutes of mild (74 ± 2 mmHg PET O₂) and moderate (50 ± 3 mmHg PET O₂) normobaric hypoxia (n = 12) or normoxia (time-control trial; n = 10)...
September 13, 2017: Experimental Physiology
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