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Experimental Physiology

Thibault Cavey, Nicolas Pierre, Kévin Nay, Coralie Allain, Martine Ropert, Olivier Loréal, Frédéric Derbré
During spaceflight, humans exposed to microgravity exhibit an increase of iron storage and a reduction of circulating iron. Such perturbations could promote oxidative stress and anemia in astronauts. The mechanism by which microgravity modulates iron metabolism is still unknown. Herein, we hypothesized that microgravity up-regulates hepcidin, a hormone produced by the liver that is the main controller of iron homeostasis. To test this hypothesis, rats were submitted to hindlimb unloading (HU), the reference model to mimic the effects of microgravity in rodents...
January 13, 2017: Experimental Physiology
Gisou Mohaddes, Jalal Abdolalizadeh, Shirin Babri, Fezzeh Hossienzadeh
The blood brain barrier (BBB), which serves to protect homeostasis of the central nervous system, is formed by tight junction proteins. Several studies have indicated that systemic hypoxia leads to cerebral edema through disruption of the tight junction proteins such as occludin and zonula occludens-1 (ZO-1). According to our previous studies ghrelin attenuates cerebral edema in the hypoxic brain. However, its mechanisms are not completely understood. The present study was aimed to determine the effect of ghrelin on occludin and Zo-1 in the hypoxic brain...
January 11, 2017: Experimental Physiology
Daniil V Popov, Evgeny A Lysenko, Alexey D Butkov, Tatiana F Vepkhvadze, Dmitriy V Perfilov, Olga L Vinogradova
In human skeletal muscle, PGC-1α is constitutively expressed via the canonical promoter. By contrast, the expression of PGC-1α mRNA via the alternative promoter was found to be highly dependent on the intensity of exercise and to contribute largely to the post-exercise increase of total PGC-1α mRNA. This study investigated the role of AMPK in regulating PGC-1α gene expression via the alternative promoter through a cAMP responsive element-binding protein-1 (CREB1)-dependent mechanism in human skeletal muscle...
January 10, 2017: Experimental Physiology
Heow Won Lee, Monir Ahmad, Hong-Wei Wang, Frans H H Leenen
Exercise training post myocardial infarction (MI) attenuates progressive left ventricle (LV) remodeling and dysfunction, but the peripheral stimuli induced by exercise which trigger these beneficial effects are still unclear. We investigated as possible mediators fibronectin type III domain-containing protein 5 (FNDC5) and brain-derived neurotrophic factor (BDNF) in the skeletal muscle and heart. Male Wistar rats underwent either sham surgery or ligation of left descending coronary artery, and surviving MI rats were allocated to either sedentary (Sed-MI) or exercise group (ExT-MI)...
January 9, 2017: Experimental Physiology
Ruihan Wei, Sean P Parsons, Jan D Huizinga
Interstitial cells of Cajal (ICC) are the pacemaker cells of gut motility and are associated with motility disorders. ICC form a network, but the contributions of its network properties to gut physiology and dysfunction are poorly understood. We modeled an ICC network as a two-dimensional network of weakly coupled oscillators with a frequency gradient and showed changes over time in video and graphical formats. Model parameters were obtained from slow wave driven contraction patterns in the mouse intestine and pacemaker slow wave activities from the cat intestine...
December 30, 2016: Experimental Physiology
Yimin Jia, Jian Hong, Huifang Li, Yun Hu, Longfei Jia, Demin Cai, Ruqian Zhao
Butyrate can prevent diet-induced obesity through increasing energy expenditure. However, it is unclear whether AR3β mediates butyrate -induced adipose lipolysis. In this study, weaned mice were were fed control (Con) or high-fat (HF) diet for 8 weeks to establish obesity. HF-induced obese mice maintained on the HF diet were divided into two sub-groups; HFB group was gavaged with 80 mg sodium butyrate (SB) per mouse every other day for 10 days, while the HF group received vehicle. Chromatin immunoprecipitation assay was performed to determine the status of histone H3 lysine 9 acetylation (H3K9Ac) on the promoter of AR3β gene in epididymal white adipose tissue...
December 28, 2016: Experimental Physiology
Eileen S Rodriguez-Tapia, Vinogran Naidoo, Matthew DeVries, Alberto Perez-Medina, James J Galligan
There is evidence that R-type Ca(2+) channels contribute to synaptic transmission in the myenteric plexus. It is unknown if R-type Ca(2+) channels contribute to neuromuscular transmission. We measured the effects of the nitric oxide synthase (NOS) inhibitor, nitro L-arginine (NLA), Ca(2+) channel blockers and apamin (SK channel blocker) on neurogenic relaxations and contractions of the guinea pig ileum longitudinal muscle-myenteric plexus (LMMP) in vitro. We used intracellular recordings to measure inhibitory junction potentials (IJPs)...
December 23, 2016: Experimental Physiology
Jeremy P T Ward
Pulmonary hypertension is associated with oxidant stress and increased generation of reactive oxygen species (ROS) by NADPH oxidases (NOX), mitochondria and other sources. There is considerable evidence that these contribute to the aetiology via promotion of pulmonary vascular remodelling, endothelial dysfunction and enhanced vasoreactivity. However, it is now recognised that ROS act as important signalling mediators and second messengers under normal physiological conditions. Many ion channels and protein kinases critical to pulmonary vascular function are directly or indirectly affected by redox/ROS, including K(+) , Ca(2+) and nonselective cation channels and Rho kinase...
December 22, 2016: Experimental Physiology
David W Popok, Christopher R West, Laura McCracken, Andrei V Krassioukov
Spinal cord injury (SCI) reduces physical activity and alters descending supraspinal cardiovascular control, predisposing this population to early onset of cardiovascular disease. We used a T3 SCI rodent model to investigate the effect of early vs. delayed passive hind-limb cycling (PHLC), as well as the effect of detraining on cardiac dysfunction and blood pressure control, including autonomic dysreflexia (AD). 20 male Wistar rats were divided into an early PHLC initiation group followed by a period of detraining (PHLC starting day 6 post-SCI, for 4 weeks, followed by 4 weeks of detraining; "early PHLC/detraining" group) and a delayed PHLC intervention group (no PHLC for first 5 weeks post-SCI, followed by PHLC for 4 weeks; "no PHLC/delayed PHLC" group)...
December 22, 2016: Experimental Physiology
Mario Boehm, Allan Lawrie, Jochen Wilhelm, Hossein A Ghofrani, Friedrich Grimminger, Norbert Weissmann, Werner Seeger, Ralph T Schermuly, Baktybek Kojonazarov
Assessment of right ventricular (RV) function in rodents is a challenge due to the complex RV anatomy and structure. Subsequently, the best characterization of RV function is achieved by accurate cardiovascular phenotyping, involving a combination of non-invasive imaging and intra-cardiac pressure-volume measurements. We sought to investigate the feasibility of two complementary phenotyping techniques for the evaluation of RV function in an experimental mouse model of sustained RV pressure overload. Mice underwent either Sham surgery (n = 5) or pulmonary artery banding (PAB) (n = 8) to induce isolated RV pressure overload...
December 19, 2016: Experimental Physiology
Naoto Fujii, Brendan D McNeely, Sarah Y Zhang, Yasmine C Abdellaoui, Mercy O Danquah, Glen P Kenny
Protease-activated receptor 2 (PAR2) is present in human skin including keratinocytes, endothelial cells of skin microvessels, and eccrine sweat glands. However, whether PAR2 functionally contributes to the regulation of cutaneous blood flow and sweating remains entirely unclear in humans in vivo. We hypothesized that activation of PAR2 directly stimulates cutaneous vasodilatation and sweating via actions of nitric oxide synthase (NOS) and cyclooxygenase (COX). In twelve physically active young males (29 ± 5 years), cutaneous vascular conductance (CVC) and sweat rate were measured at four intradermal microdialysis forearm skin sites that were treated with 1) lactated Ringer's solution (Control), 2) 10 mm N(ω) -nitro-L -arginine (NOS inhibitor), 3) 10 mm ketorolac (COX inhibitor), or 4) a combination of both inhibitors...
December 16, 2016: Experimental Physiology
James Pearson, Rebekah A I Lucas, Zachary J Schlader, Daniel Gagnon, Craig G Crandall
Tolerance to a simulated hemorrhagic insult, such as lower-body negative pressure (LBNP), is profoundly reduced when accompanied by whole-body heat stress. The aim of this study was to investigate the separate and combined influence of elevated skin (Tskin) and core (Tcore) temperatures on LBNP tolerance. We hypothesized that elevations in Tskin as well as Tcore would both contribute to reductions in LBNP tolerance, and that the reduction in LBNP tolerance would be greatest when both Tskin and Tcore were elevated...
December 16, 2016: Experimental Physiology
Ellen C Breen, Miriam Scadeng, N Chin Lai, Fiona Murray, Timothy D Bigby
Pulmonary arterial hypertension (PAH) is characterized by elevated pulmonary artery pressures and right heart failure. PAH mouse models are instrumental in understanding disease pathophysiology. However, few methods are available to evaluate right cardiac function in small animals. In this study, magnetic resonance imaging (MRI) was used to measure in vivo cardiac dimensions in the Sugen 5416/hypoxia mouse model. Pulmonary hypertension (PH) was induced in C57BL/6 mice by three weeks of exposure to 10% oxygen and VEGF receptor inhibition (20 mg kg(-1) SU5416)...
November 29, 2016: Experimental Physiology
Robert M Restaino, Shekhar H Deo, Alan R Parrish, Paul J Fadel, Jaume Padilla
Recent evidence suggests that exposure of human monocytes to glucolipotoxic media to mimic the composition of plasma of patients with type 2 diabetes (T2D) results in the induction of endoplasmic reticulum stress markers and formation of reactive oxygen species (ROS). The extent to which these findings translate to patients with T2D remains unclear. Thus, we first measured ROS (dihydroethidium fluorescence) in peripheral blood mononuclear cells (PBMCs) from whole blood of T2D patients (n = 8) and compared to age matched healthy controls (n = 8)...
November 18, 2016: Experimental Physiology
Naoto Fujii, Jeffrey C Louie, Brendan D McNeely, Sarah Y Zhang, My-An Tran, Glen P Kenny
What is the central question of this study? Acetylcholine released from cholinergic nerves can activate both muscarinic and nicotinic receptors. Although each receptor can independently induce cutaneous vasodilatation and eccrine sweating, it remains to be elucidated whether the two receptors interact in order to mediate these responses. What is the main finding and its importance? We show that although nicotinic receptor activation does not modulate muscarinic cutaneous vasodilatation, it lowers the muscarinic receptor agonist threshold at which onset for eccrine sweating (augmentation of muscarinic eccrine sweating) occurs in young men in normothermic resting conditions...
November 18, 2016: Experimental Physiology
Kameljit K Kalsi, Scott T Chiesa, Steven J Trangmar, Leena Ali, Makrand D Lotlikar, José González-Alonso
Local tissue perfusion changes with alterations in temperature during heating and cooling, but the thermosensitivity of the vascular ATP signalling mechanisms for control of blood flow during thermal interventions remains unknown. Here we tested the hypotheses that the release of the vasodilator mediator ATP from human erythrocytes, but not from endothelial cells or other blood constituents, is sensitive to both increases and reductions in temperature and that increasing intravascular ATP availability with ATP infusion would potentiate thermal hyperaemia in limb tissues...
November 17, 2016: Experimental Physiology
Anton Misak, Frantisek Kristek, Lenka Tomasova, Marian Grman, Elena Ondriasova, Olga Krizanova, Karol Ondrias
What is the central question of this study? We wanted to find out whether the relationship between rat arterial pulse waveform (APW) parameters and blood pressure could be described by known mathematical functions and find mathematical parameters for conditions of hypertension resulting from decreased NO bioavailability. What is the main finding and its importance? We found mathematical functions and their parameters that approximate the relationships of 12 APW parameters to systolic and diastolic blood pressure in conditions of decreased NO bioavailability...
November 11, 2016: Experimental Physiology
Matthew N Cramer, Daniel Gagnon, Craig G Crandall, Ollie Jay
What is the central question of this study? Does attenuated skin blood flow diminish sweating and reduce the critical environmental limit for heat balance, which indicates maximal heat loss potential, during severe heat stress? What is the main finding and its importance? Isosmotic hypovolaemia attenuated skin blood flow by ∼20% but did not result in different sweating rates, mean skin temperatures or critical environmental limits for heat balance compared with control and volume-infusion treatments, suggesting that the lower levels of skin blood flow commonly observed in aged and diseased populations may not diminish maximal whole-body heat dissipation...
November 11, 2016: Experimental Physiology
Tatsuro Amano, Seiko Kai, Michi Nakajima, Tomoko Ichinose-Kuwahara, Nicola Gerrett, Narihiko Kondo, Yoshimitsu Inoue
What is the central question of this study? Non-thermal factors (e.g. muscle metaboreflex) contribute to the sweating response during exercise. Although it is well recognized that the sweating responses caused by core temperature elevation in prepubertal children and the elderly are attenuated compared with young adults, it is unknown whether non-thermal sweating is also attenuated in these populations. What is the main finding and its importance? The non-thermal sweating response during isometric hand-grip exercise and isolated muscle metaboreflex were attenuated in prepubertal children compared with young adults in a non-uniform manner over the body, but only during the muscle metaboreflex in the elderly...
November 11, 2016: Experimental Physiology
Krzysztof Gwozdzinski, Anna Pieniazek, Sabina Tabaczar, Anna Jegier, Joanna Brzeszczynska
The objective of study was to establish the role of exercise-induced oxidative stress in the erythrocyte fractions: young (YF), middle-aged (MAF) and old (OF) of young untrained men after acute exercise. Blood samples were collected before exercise, immediately and one hour after exercise. Maximum wattage was 292±27 W and exercise time duration was 8.73±0.9 min. Different optical properties and oxidative stress parameters were found in each erythrocyte fraction. Total thiols in YF and MAF after exercise and after one hour rest were similar to values before exercise, however, in OF (32...
November 10, 2016: Experimental Physiology
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