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Experimental Physiology

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https://www.readbyqxmd.com/read/29235182/spinal-cord-injury-induced-cardiomyocyte-atrophy-and-impaired-cardiac-function-are-severity-dependent
#1
Jordan W Squair, Jie Liu, Wolfram Tetzlaff, Andrei V Krassioukov, Christopher R West
The principle aim of the present study was to assess how the severity of spinal cord injury (SCI) affects LV mechanics, function, and underlying cardiomyocyte morphology. Here, we utilized different severities of T3 spinal cord contusions (MODERATE, 200Kdyn contusion; SEVERE, 400kdyn contusion; SHAM) and combined standard echocardiography with speckle tracking analyses to investigate in vivo cardiac function and deformation (contractility) after experimental SCI in the Wistar rat. In addition, we investigated changes in the intrinsic structure of cardiac myocytes ex vivo...
December 12, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/29215757/hypothalamic-paraventricular-nucleus-neuronal-nitric-oxide-synthase-activity-is-a-major-determinant-of-renal-sympathetic-discharge-in-conscious-wistar-rats
#2
F D McBryde, B H Liu, E V Roloff, S Kasparov, J F R Paton
The paraventricular nucleus of the hypothalamus (PVN) plays a crucial role in cardiovascular and neuroendocrine regulation. Application of nitric oxide donors to the PVN stimulates GABAergic transmission, and may suppress sympathetic nerve activity (SNA) to lower arterial pressure. However, the role of endogenous nitric oxide within PVN in regulating renal SNA chronically remains to be established in conscious animals. To address this, we used our previously established lentiviral vectors to selectively knock down neuronal nitric oxide synthase (nNOS) in the PVN of conscious Wistar rats...
December 7, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/29215172/fibroblast-growth-factor-21-increases-hepatic-oxidative-capacity-but-not-physical-activity-or-energy-expenditure-in-hepatic-pgc-1%C3%AE-deficient-mice
#3
Justin A Fletcher, Melissa A Linden, Ryan D Sheldon, Grace M Meers, E Matthew Morris, Anthony Butterfield, James W Perfield, R Scott Rector, John P Thyfault
Fibroblast growth factor 21 (FGF21) treatment drives metabolic improvements, including increased metabolic flux and reduced hepatic steatosis, but mechanisms responsible for these effects remain to be fully elucidated. We tested if a targeted reduction in hepatic PGC-1α, which has been shown to occur with obesity, negatively impacted the metabolic effects of FGF21. We infused FGF21 (1 mg kg-1  day-1 ) or saline in chow-fed wild-type (WT) and liver-specific PGC-1α +/- (LPGC-1α) mice for 4 weeks. FGF21 administration lowered serum insulin and cholesterol (P ≤ 0...
December 7, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/29214684/pharmacotherapies-for-apnoea-of-prematurity-time-to-pause-and-consider-targeted-sex-specific-strategies
#4
Ken D O'Halloran, Fiona B McDonald
Developmental plasticity in the neural network orchestrating respiratory control is such that pre-term birth is associated with the elaboration of dysrhythmic breathing patterns characterized by periodic suppression of the central drive to breathe, evoking recurrent respiratory pauses termed central apnoeas. This article is protected by copyright. All rights reserved.
December 6, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/29210478/type-2-diabetes-specifically-attenuates-purinergic-skin-vasodilatation-without-affecting-muscarinic-and-nicotinic-skin-vasodilatation-and-sweating
#5
Naoto Fujii, Robert D Meade, Brendan D McNeely, Takeshi Nishiyasu, Ronald J Sigal, Glen P Kenny
The present study evaluated whether type 2 diabetes (T2D) attenuates muscarinic and/or nicotinic cutaneous vasodilatation and sweating as well as purinergic cutaneous vasodilatation. Cutaneous vascular conductance and sweat rate were evaluated in 12 healthy nondiabetic older adults (Control, 60 ± 8 years) and 13 older adults with T2D (62 ± 10 years) at three intradermal forearm skin sites perfused with the following: 1) methacholine (muscarinic receptor agonist, 5 doses: 0.0125, 0.25, 5, 100, 2000 mm), 2) nicotine (nicotinic receptor agonist, 5 doses: 1...
December 6, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/29210126/crosslink-of-calcium-and-sodium-signalling-in-health-and-disease
#6
Alexei Verkhratsky, Mohamed Trebak, Fabiana Perocchi, Daniel Khananishvili, Israel Sekler
Transmembrane ionic gradients, that are indispensable feature of life, are utilised for generation of cytosolic ionic signals that regulate a host of cellular functions. Intracellular signalling mediated by Ca2+ and Na+ is tightly linked through several molecular pathways that generate Ca2+ and Na+ fluxes and are in turn regulated by both ions. Transient receptor potential (TRP) channels bridge endoplasmic reticulum Ca2+ release with generation of Na+ and Ca2+ currents. Plasmalemmal Na+ /Ca2+ exchanger by flickering between forward and reverse mode coordinates influx and efflux of both ions with membrane polarisation and cytosolic ion concentration...
December 6, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/29210120/endogenous-peripheral-hydrogen-sulfide-is-propyretic-its-permissive-role-in-brown-adipose-tissue-thermogenesis-in-rats
#7
Renato N Soriano, Sara P Braga, Jéssica S C Breder, Marcelo E Batalhao, Gabriela R Oliveira-Pelegrin, Luiz Fernando R Ferreira, Maria José A Rocha, Evelin C Carnio, Luiz G S Branco
In recent years hydrogen sulfide (H2 S) has been reported as a gaseous modulator acting in several tissues in health and disease. In systemic inflammation animal models, plasma H2 S concentration increases in response to endotoxin (bacterial lipopolysaccharide, LPS). The most striking response in the acute phase reaction of systemic inflammation is fever, but reports of the peripheral action of H2 S on this thermoregulatory response are not found. We aimed at investigating whether endogenous systemic H2 S modulates LPS-induced fever...
December 6, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/29205610/three-dimensional-morphology-and-volume-of-the-free-achilles-tendon-at-rest-and-under-load-in-people-with-unilateral-mid-portion-achilles-tendinopathy
#8
Leila Nuri, Steven J Obst, Richard Newsham-West, Rod S Barrett
Mid-portion Achilles tendinopathy (MAT) adversely affects free Achilles tendon (AT) structure and composition. However, it is not known how these pathological alterations associated with MAT change the normal three-dimensional (3D) morphology of free AT at rest and under load throughout the entire free tendon length. Here, we used 3D ultrasound to examine the effect of unilateral MAT on free tendon 3D morphology [length, cross-sectional area (CSA), antero-posterior (AP) diameter, and medio-lateral (ML) diameter] and volume at rest and during a sub-maximal (50%) voluntary isometric plantarflexion contraction bilaterally in individuals with unilateral MAT (n = 10) compared to a matched healthy control group (n = 10)...
December 3, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/29193495/premature-birth-affects-the-degree-of-airway-dysanapsis-and-mechanical-ventilatory-constraints
#9
Joseph W Duke, Igor M Gladstone, A William Sheel, Andrew T Lovering
Adult survivors of very preterm birth (≤32 weeks gestational age) without (PRE) and with bronchopulmonary dysplasia (BPD) have obstructive lung disease as evidenced by reduced expiratory airflow at rest and have significant mechanical ventilatory constraints during exercise. Airflow obstruction, under any condition, could be due to several factors including small airways. PRE and/or BPD could have smaller airways than their counterparts born at full-term (CON) due to a greater degree of dysanaptic airway development during the pre- and/or post-natal period...
November 29, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/29178489/daily-inspiratory-muscle-training-lowers-blood-pressure-and-vascular-resistance-in-healthy-men-and-women
#10
Claire M DeLucia, Roxanne M De Asis, E Fiona Bailey
Previous work has shown inspiratory muscle training (IMT) lowers blood pressure after just six weeks, identifying IMT as a potential therapeutic to prevent/treat hypertension. Here, we explore the effects of IMT on respiratory muscle strength and select cardiovascular parameters in recreationally active men and women. Subjects were randomly assigned to IMT (n = 12, 75% maximal inspiratory pressure) or sham training (n = 13, 15% maximum inspiratory pressure) groups and underwent a 6-week intervention comprising 30 breaths day-1 , 5 days week-1 ...
November 24, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/29168593/respiratory-regulation-by-steroids-in-newborn-rats-a-sex-specific-balance-between-allopregnanolone-and-progesterone-receptors
#11
Vincent Joseph, NagaPraveena Uppari, Hayet Kouchi, Celia De Bruyn, Ryma Boukari, Aida Bairam
We tested the hypothesis that the effects of progesterone on apnoea frequency in newborn rats are the result of a balance between its neuroactive metabolite allopregnanolone (GABAa receptor modulator) and progesterone receptors. We used male and female rats between 10 and 12 days of age and recorded respiratory and metabolic parameters (whole-body plethysmography), and assessed the frequency and duration of apnoeas under normoxia. We tested the effects of a single injection of progesterone (4 mg kg(-1) , i...
November 23, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/29152797/oxidative-stress-does-not-influence-local-sweat-rate-during-high-intensity-exercise
#12
Robert D Meade, Naoto Fujii, Martin P Poirier, Pierre Boulay, Ronald J Sigal, Glen P Kenny
Nitric oxide (NO)-dependent sweating is diminished during high but not moderate intensity exercise. We evaluated whether this impairment stems from increased oxidative stress during high intensity exercise. On two separate days, 11 young (24 ± 4 years) males cycled in the heat (35°C) at a moderate (500 W; 52 ± 6%VO2peak ) or high (700 W; 71 ± 5%VO2peak ) rate of metabolic heat production. Each session included two 30-min exercise bouts separated by a 20-min recovery. Local sweat rate was monitored at four forearm skin sites continuously perfused via intradermal microdialysis with: (1) lactated Ringer's solution (Control), (2) 10 mm ascorbate (Ascorbate; non-selective antioxidant), (3) 10 mm N(G) -nitro-L -arginine methyl ester (L-NAME; NO synthase inhibitor), or (4) 10 mm Ascorbate + 10 mm L-NAME (Ascorbate + L-NAME)...
November 19, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/29143998/oxytocin-mediates-the-beneficial-effects-of-the-exercise-training-on-breast-cancer
#13
Ali Mohammad Alizadeh, Zahra Heydari, Mostafa Rahimi, Behzad Bazgir, Hossein Shirvani, Sadaf Alipour, Yassaman Heidarian, Solmaz Khalighfard, Amin Isanejad
Exercise training can affect the breast tumor growth. We hypothesized that exercise training may reduce breast tumor growth by inducing Oxytocin (OT) secretion and its related signaling pathways such as PI3K/AKT and ERK. Therefore fifty-six BALB/c mice were equally divided into seven groups to study the effects of OT and atosiban (an oxytocin receptor antagonist) together with the interval exercise training on breast tumor growth, as well as tumor related signaling pathways including PI3K/AKT and ERK. Animal weight, OT plasma level, tumor weight and volume measured at the end of study...
November 16, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/29205954/mechanisms-underpinning-sympathetic-nervous-activity-and-its-modulation-using-transcutaneous-vagus-nerve-stimulation
#14
Susan A Deuchars, Varinder K Lall, Jennifer Clancy, Mohd Mahadi, Aaron Murray, Lucy Peers, Jim Deuchars
What is the topic of this review? This review briefly considers what modulates sympathetic nerve activity and how it may change as we age or in pathological conditions. It then focuses on transcutaneous vagus nerve stimulation, a method of neuromodulation in autonomic cardiovascular control. What advances does it highlight? The review considers the pathways involved in eliciting the changes in autonomic balance seen with transcutaneous vagus nerve stimulation in relationship to other neuromodulatory techniques...
November 11, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/29127736/liver-x-receptor-activation-inhibits-sglt2-mediated-glucose-transport-in-human-renal-proximal-tubular-cells
#15
Pattira Chonlaket, Teerasak Wongwan, Sunhapas Soodvilai
Liver X receptors (LXRs) are members of a nuclear receptor family consisting of two isoforms, LXR-α and LXR-β. They play a major role in energy metabolism including lipid and glucose metabolism. Recent studies reported LXRs regulate plasma glucose although the mechanism is still uncertain. The present study investigated whether LXR activation regulates sodium glucose cotransporter2 (SGLT2) in human renal proximal tubular cells. LXR agonists, T0901317 and GW3965, inhibited SGLT2-mediated glucose uptake in concentration-dependent manners...
November 11, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/29114952/age-related-microvascular-dysfunction-novel-insight-from-near-infrared-spectroscopy
#16
Ryan Rosenberry, Madison Munson, Susie Chung, T Jake Samuel, Jordan Patik, Wesley J Tucker, Mark J Haykowsky, Michael D Nelson
Near-infrared spectroscopy (NIRS) has emerged as a promising tool to evaluate vascular reactivity in vivo. Whether this approach can be used to assess age-related impairments in microvascular function has not been tested. Tissue oxygen saturation (StO2 ) post-occlusion recovery kinetics were measured in two distinct age groups (<35 year and >65 years) using NIRS placed over the flexor digitorum profundus. Key end-points included: (1) the desaturation rate during cuff occlusion; (2) the lowest StO2  value obtained during ischemia (StO2min ); (3) StO2  reperfusion rate; (4) the highest StO2  value reached after cuff release (StO2max ); and (5) the reactive hyperemia area under the curve (AUC)...
November 7, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/29114945/hyperglycaemia-induced-by-chronic-i-p-and-oral-glucose-loading-leads-to-hypertension-through-increased-na-retention-in-proximal-tubule
#17
Selim Fakhruddin, Wael A Alanazi, Hussain N Alhamami, Karen P Briski, Keith E Jackson
What is the central question of the study? Chronic glucose feeding accompanied by glucose injection (i.p.) causes sustained hyperglycaemia and hypertension in rats. The exact reason for the hypertension is not known. We explore some molecular pathways of the renal proximal tubule that might promote Na+ retention. What is the main finding and its importance? Development of hypertension was mediated by upregulation of the renal renin-angiotensin system and oxidative stress, acting via the Na+ -K+ -ATPase α1 -subunit in the proximal tubule, which appears to pump intracellular Na+ into the extracellular space, increasing Na+ reabsorption and blood pressure...
November 7, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/29113012/the-suprachiasmatic-nucleus-drives-day-night-variations-in-postprandial-triglyceride-uptake-into-skeletal-muscle-and-brown-adipose-tissue
#18
Sofía Moran-Ramos, Natali N Guerrero-Vargas, Rebeca Mendez-Hernandez, Maria Del Carmen Basualdo, Carolina Escobar, Ruud M Buijs
What is the central question of this study? What are the factors influencing day-night variations in postprandial triglycerides? What is the main finding and its importance? Rats show low postprandial plasma triglyceride concentrations early in the active period that are attributable to a higher uptake by skeletal muscle and brown adipose tissue. We show that these day-night variations in uptake are driven by the suprachiasmatic nucleus, probably via a Rev-erbα-mediated mechanism and independent of locomotor activity...
November 7, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/29094480/myocardial-infarction-does-not-affect-circulating-hematopoietic-stem-and-progenitor-cell-self-renewal-ability-in-a-rat-model
#19
J M Kröpfl, C M Spengler, A Frobert, G Ajalbert, M N Giraud
Due to the importance of peripheral blood hematopoietic stem and progenitor cells (HPCs) in post-acute regeneration after acute myocardial infarction (MI), the present study aimed to investigate count and secondary replating capacity/self-renewal ability of HPCs in peripheral blood before and two weeks after MI. In nine female Lewis inbred rats (n = 9), myocardial infarction was induced by ligation of the left coronary artery while another nine had surgery without ligation for control purposes. Myocardial infarction was confirmed by troponin I concentrations 24 h after MI...
November 2, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/29094471/antifibrillatory-effects-of-renal-denervation-on-ventricular-fibrillation-in-a-canine-model-of-pacing-induced-heart-failure
#20
Qingzhi Luo, Qi Jin, Ning Zhang, Shangwei Huang, Yanxin Han, Changjian Lin, Tianyou Ling, Kang Chen, Wenqi Pan, Liqun Wu
This study investigated the effects of renal denervation (RDN) on vulnerability to ventricular fibrillation (VF) and ventricular electrical properties in a canine model of pacing-induced heart failure (HF). Eighteen beagles were divided into the following three groups: control (n = 6), HF (n = 6) and HF+RDN (n = 6). HF was induced by rapid right ventricular pacing. RDN was performed simultaneously with the pacemaker implantation in the HF+RDN group. A 64-unipolar basket catheter was used to perform global endocardial mapping of the left ventricle...
November 2, 2017: Experimental Physiology
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