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Experimental Physiology

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https://www.readbyqxmd.com/read/28635124/regular-aerobic-exercise-reduces-endothelin-1-mediated-vasoconstrictor-tone-in-overweight-and-obese-adults
#1
Caitlin A Dow, Brian L Stauffer, Danielle L Brunjes, Jared J Greiner, Christopher A DeSouza
Endothelin (ET)-1-mediated vasoconstrictor tone is elevated in overweight and obese adults, contributing to vasomotor dysfunction and increased cardiovascular disease risk. While the effects of habitual aerobic exercise on endothelium-dependent vasodilation in overweight/obese adults has been studied, little is known regarding ET-1 vasoconstriction. Accordingly, the aims of the present study were to determine: (1) if regular aerobic exercise training reduces ET-1-mediated vasoconstrictor tone in overweight and obese adults; and, if so (2) whether the reduction in ET-1 vasoconstriction contributes to exercise-induced improvement in endothelium-dependent vasodilation in this population...
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
#2
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
#3
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
#4
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
#5
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
Rosiglitazone and pioglitazone are thiazolidinedione (TZD) compounds that have been used clinically as insulin-sensitizing drugs and are generally believed to mediate their effects via activation of the peroxisome proliferator-activated receptor γ (PPARγ). Recent work has shown that it is possible to synthesize TZD compounds with potent insulin-sensitizing effects and markedly-diminished affinity for PPARγ. Both clinically-used TZDs and investigational PPARγ-sparing TZDs, such as MSDC-0602, interact with the mitochondrial pyruvate carrier (MPC) and inhibit its activity...
June 9, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28594464/do-changes-in-neuromuscular-activation-contribute-to-the-knee-extensor-angle-torque-relationship
#6
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
#7
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
https://www.readbyqxmd.com/read/28585766/one-minute-plantar-flexors-static-stretch-transiently-increases-h-reflex-excitability-and-exerts-no-effect-on-corticospinal-pathways
#8
Francesco Budini, Eugen Gallasch, Monica Christova, Dietmar Rafolt, Andreas Benedikt Rauscher, Tilp Markus
The purpose of this study was to determine whether the neural responses observed following static stretching are mediated by muscle spindles sensitivity, spinal excitability or cortical excitability and how long these influences last. Nineteen volunteers (25.7 ± 5.6 years) were tested for tap reflex (T-reflex), H-reflex and motor evoked potentials (MEPs) on ankle flexors and extensors at immediately, five and ten minutes after one minute static stretching applied at individual maximal ankle dorsiflexion, as well as immediately, five and ten minutes after a control period of same duration...
June 6, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28568648/influence-of-sex-on-circulating-endothelial-microparticle-number-and-microrna-expression-in-middle-aged-adults
#9
Tyler D Bammert, Jamie G Hijmans, Philip J Kavlich, Grace M Lincenberg, Whitney R Reiakvam, Ryan T Fay, Jared J Greiner, Brian L Stauffer, Christopher A DeSouza
The aims of this study were to determine: 1) if circulating concentrations of endothelial microparticles (EMPs) differ in middle-aged men compared with women; and 2) whether there are sex-related differences in microRNA expression in EMPs. Peripheral blood was collected from 30 sedentary adults: 15 men (52 ± 8 yr) and 15 women (52 ± 8 yr). EMPs were defined by markers of activation (CD62e(+) ) or apoptosis (CD31(+) /CD42b(-) ) by flow cytometry. MicroRNA (miR-34a, 92a, 125a, and 126) expression in activation- and apoptosis-derived EMPs was measured by RT-PCR...
June 1, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28560751/differential-control-of-respiratory-frequency-and-tidal-volume-during-high-intensity-interval-training
#10
Andrea Nicolò, Samuele M Marcora, Ilenia Bazzucchi, Massimo Sacchetti
Since respiratory frequency (fR ) has been proposed as a good marker of physical effort, furthering the understanding of how fR is regulated during exercise is of great importance. We manipulated recovery intensity and exercise duration during high-intensity interval training (HIIT) to test the hypothesis that fast inputs (including central command) contribute more than metabolic stimuli to fR regulation. Seven male cyclists performed an incremental test, a 10 min and a 20 min continuous time trial (TT) as preliminary tests...
May 31, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28560747/can-assessment-of-afferent-thermal-sensitivity-shed-light-into-multiple-sclerosis-diagnosis-and-disease-progression
#11
R Matthew Brothers
Multiple Sclerosis (MS) is a disabling disease effecting approximately 2.5 million people worldwide. Common symptomology experienced by MS patients include complications with: vision, motor control, fatigue, bladder control, and sensory function. This article is protected by copyright. All rights reserved.
May 31, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28556994/hyperglycemia-in-pregnant-rats-causes-gender-related-vascular-dysfunction-in-adult-offspring-role-of-cyclooxygenase-2
#12
Francine Gomes de Sá, Diego Barbosa de Queiroz, Fernanda Elizabethe Ramos-Alves, Juliana Santos-Rocha, Odair Alves da Silva, Hicla Steffany Moreira, Geórgia Andrade Leal, Marcelo Aurélio da Rocha, Gloria Pinto Duarte, Fabiano Elias Xavier
Exposure to maternal hyperglycemia induces hypertension and vascular dysfunction in adult male offspring. Because female offspring from several fetal programming models are protected from the effects of fetal insult, in this study we analyzed possible differences relative to gender in blood pressure and vascular function in hyperglycemia-programmed offspring. Hyperglycemia was induced on gestation day 7 (streptozotocin, 50 mg.kg(-1) ). Blood pressure, acetylcholine and phenylephrine/noradrenaline responses were analyzed in aorta and mesenteric resistance arteries (MRA) of 3-, 6- and 12-month-old male and female offspring...
May 30, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28556421/gastrointestinal-disorders-after-immunosuppression-an-experimental-model-to-evaluate-the-influence-of-monotherapy-on-motility-parameters
#13
Denize Jussara Rupolo Dall'Agnol, Luciana Aparecida Corá, Maria do Carmo Borges Teixeira, Maysa Bruno de Lima, Loyane Almeida Gama, José Ricardo de Arruda Miranda, Madileine Francely Américo
OBJECTIVES: The aim was to propose an animal model for investigating the effects of immunosuppressive monotherapy on gastrointestinal motility using a non-invasive biomagnetic technique. METHODS: Male Wistar rats were randomly distributed into groups: Cyclosporine, Tacrolimus, Prednisone, Sirolimus, Mycophenolate Mofetil, Everolimus and Azathioprine. Each animal was treated during 14 days by gavage with dosage ranging from 1 to 20 mg Kg(-1)  day(-1) considering area per volume ratio and hepatic metabolism...
May 26, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28544046/time-related-changes-in-firing-rates-are-influenced-by-recruitment-threshold-and-twitch-force-potentiation-in-the-first-dorsal-interosseous
#14
Jonathan D Miller, Trent J Herda, Michael A Trevino, Adam J Sterczala, Anthony B Ciccone
There are contradictory reports regarding changes in motor unit firing rates during steady force contractions. Inconsistencies are likely the result of previous studies disregarding motor unit recruitment thresholds and not examining firing rates on a subject-by-subject basis. It is hypothesized that firing rates are manipulated by twitch force potentiation during contractions. Therefore, this study examined time-related changes in firing rates at steady force in relation to motor unit recruitment threshold in the first dorsal interosseous and the influence of twitch force potentiation on such changes in young versus aged individuals...
May 24, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28543947/%C3%AE-1-adrenoceptor-but-not-%C3%AE-2-adrenoceptor-subtype-regulates-heart-rate-in-type-2-diabetic-rats-in-vivo
#15
Rosalind F Cook, Carol T Bussey, Kimberley M Mellor, Patricia A Cragg, Regis R Lamberts
What is the central question of the study? The sympathetic system regulates heart rate via β-adrenoceptors; this is impaired during diabetes. However, the specific β-adrenoceptor subtype contributions in heart rate regulation in diabetes in vivo are unknown. What is the main finding and its importance? Telemetric recordings in conscious non-diabetic and type 2 diabetic rats demonstrated that the β1 -adrenoceptor subtype, and not the β2 -adrenoceptor, regulated the lower resting heart rate and increased β-adrenoceptor responsiveness in diabetes in vivo...
May 22, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28497900/utility-and-reliability-of-non-invasive-muscle-function-tests-in-high-fat-fed-mice
#16
Sergio F Martinez-Huenchullan, Susan V McLennan, Linda A Ban, Marco Morsch, Stephen M Twigg, Charmaine S Tam
Non-invasive tests are commonly used for assessing muscle function in animal models. The value of these tests in obesity, a condition where muscle strength is reduced, is unclear. We investigated the utility of three non-invasive muscle function tests, namely grip strength (GS), hang wire (HW), and four-limb hanging (FLH) in C57BL/6 mice fed chow (n = 48) or high-fat diet (HFD, n = 48) for 20 weeks. Muscle function tests were performed at 5, 10, and 20 weeks. After 10 and 20 weeks, HFD mice had significantly reduced GS (10 weeks chow:1...
May 12, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28489320/role-of-cyclooxygenase-in-the-vascular-responses-to-extremity-cooling-in-caucasian-and-african-males
#17
Matthew J Maley, James R House, Michael J Tipton, Clare M Eglin
African descent (AFD) individuals are more susceptible to non-freezing cold injury (NFCI) and experience an exaggerated cutaneous vasoconstrictor response to hand cooling compared with Caucasians (CAU). Using a placebo-controlled, crossover design, this study tested the hypothesis that cyclooxygenase (COX) may, in part, be responsible for the exaggerated vasoconstrictor response to local cooling in AFD. Twelve AFD and twelve CAU young healthy males completed foot cooling and hand cooling (separately, in 8°C water for 30 minutes) with spontaneous rewarming in 30°C air following placebo or aspirin (COX inhibition) treatment...
May 10, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28488333/afferent-thermosensory-function-in-relapsing-remitting-multiple-sclerosis-following-exercise-induced-increases-in-body-temperature
#18
Davide Filingeri, Georgia Chaseling, Phu Hoang, Michael Barnett, Scott L Davis, Ollie Jay
What is the central question of this study? Between 60 and 80% of multiple sclerosis (MS) patients experience transient worsening of symptoms with increased body temperature (heat sensitivity). As sensory abnormalities are common in MS, we asked whether afferent thermosensory function is altered in MS following exercise-induced increases in body temperature. What is the main finding and its importance? Increases in body temperature of as little as ∼0.4°C were sufficient to decrease cold, but not warm, skin thermosensitivity (∼10%) in MS, across a wider temperature range than in age-matched healthy individuals...
May 10, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28477375/oral-l-tyrosine-supplementation-augments-the-vasoconstriction-response-to-whole-body-cooling-in-older-adults
#19
James A Lang, Kevin A Smaller
L-tyrosine is the primary substrate for noradrenaline biosynthesis within sympathetic axon terminals. Under stressful conditions requiring increased catecholamine production, axonal L-tyrosine concentration may limit the full expression of the sympathetic effector response and this may be particularly evident in older adults. We hypothesize that oral L-tyrosine supplementation will increase the sympathetic response to whole-body cooling and muscle metaboreflex activation. In a randomized, double-blind design, eleven young (Y = 24 ± 1 years) and eleven older (O = 68 ± 4 years) participants ingested either 150 mg kg(-1) of L-tyrosine or placebo prior to commencing 30 minutes of whole-body cooling to induce a gradual decline in skin temperature from 34 to 30...
May 5, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28470945/mri-evaluation-of-renal-ischemia-reperfusion-injury-in-rabbit-model
#20
Liang Pan, Jie Chen, Wei Xing, Zhaoyu Xing, Jinggang Zhang, Yan Peng, Zhuoli Zhang
To evaluate the feasibility of susceptibility weighted imaging (SWI) as a tool to identify the changes in the renal outer medulla (OM) in a rabbit model of renal ischemia reperfusion injury (IRI). New Zealand rabbits were used in this study (control = 10 and IRI groups = 40). The rabbits in the IRI group were subjected to left renal artery clamping for 60 minutes. T2-weighted (T2WI) and SWI examinations were performed at 1 h, 12 h, 24 h and 48 h after reperfusion (each n = 10). After the examinations, nephrectomy was performed for histologic evaluation...
May 4, 2017: Experimental Physiology
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