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Journal of Physiology

Etienne Desrochers, Jonathan Harnie, Adam Doelman, Marie-France Hurteau, Alain Frigon
KEY POINTS: The control of locomotion is thought to be generated by activating groups of muscles that perform similar actions, which are termed muscle synergies. Here, we investigated if muscle synergies are controlled at the level of the spinal cord. We did this by comparing muscle activity in the legs of cats during stepping on a treadmill before and after a complete spinal transection that abolishes commands from the brain. We show that muscle synergies were maintained following spinal transection, validating the concept that muscle synergies for locomotion are primarily controlled by circuits of neurons within the spinal cord...
October 18, 2018: Journal of Physiology
Bożena Bądzyńska, Iwona Baranowska, Olga Gawryś, Janusz Sadowski
KEY POINTS: The development of new effective methods to treat arterial hypertension is hindered by uncertainty regarding its causes. According to one widespread concept hypertension is caused by abnormal blood circulation in the kidney, specifically by reduction of blood flow through the kidney medulla. However. such causal relationship has never been rigorously verified. We checked if in rats with three different forms of experimental hypertension prolonged selective elevation of renal medullary blood flow using local infusion of vasodilator bradykinin would lower arterial pressure...
October 18, 2018: Journal of Physiology
Elizabeth Karvasarski, Lucas Azevedo, David Granton, Stephen P Wright
No abstract text is available yet for this article.
October 17, 2018: Journal of Physiology
Juan J Ferreira, Alice Butler, Richard Stewart, Ana Laura Gonzalez-Cota, Pascale Lybaert, Chinwendu Amazu, Erin L Reinl, Monali Wakle-Prabagaran, Lawrence Salkoff, Sarah K England, Celia M Santi
KEY POINTS: At the end of pregnancy, the uterus transitions from a quiescent state to a highly contractile state. This transition requires that the uterine (myometrial) smooth muscle cells increase their excitability, but how this occurs is not fully understood. We identified SLO2.1, a potassium channel heretofore unknown to be in uterine smooth muscle as a potential significant contributor to the electrical excitability of myometrial smooth muscle cells. We found that activity of the SLO2...
October 17, 2018: Journal of Physiology
Lauren K Walsh, Thaysa Ghiarone, T Dylan Olver, Areli Medina-Hernandez, Jenna C Edwards, Pamela K Thorne, Craig A Emter, Jonathan R Lindner, Camila Manrique-Acevedo, Luis A Martinez-Lemus, Jaume Padilla
KEY POINT: It has been postulated that increased blood flow-associated shear stress on endothelial cells is an underlying mechanism by which physical activity enhances insulin-stimulated vasodilation. This report provides evidence supporting the hypothesis that increased shear stress exerts insulin-sensitizing effects in the vasculature and this evidence is based on experiments in vitro in endothelial cells, ex vivo in isolated arterioles, and in vivo in humans. Given the recognition that vascular insulin signaling, and associated enhanced microvascular perfusion, contributes to glycemic control and maintenance of vascular health, strategies that stimulate an increase in limb blood flow and shear stress have the potential to have profound metabolic and vascular benefits mediated by improvements in endothelial insulin sensitivity...
October 17, 2018: Journal of Physiology
Justin J Kavanagh, Amelia J McFarland, Janet L Taylor
KEY POINTS: Animal preparations have revealed that moderate synaptic release of serotonin (5-HT) onto motoneurones enhances motor activity via activation of 5-HT2 receptors, whereas intense release of 5-HT causes spillover of 5-HT to extrasynaptic 5-HT1A receptors on the axon initial segment to reduce motoneurone activity. We explored if increasing extracellular concentrations of endogenously released 5-HT (via the SSRI paroxetine) influences the ability to unfatigued and fatigued maximal voluntary contractions in humans...
October 16, 2018: Journal of Physiology
Sebastian Quezada, Margie Castillo-Melendez, David W Walker, Mary Tolcos
KEY POINTS: Normal folding of the cerebral cortex (gyrification) is fundamental for neurodevelopment. Some molecular mechanisms of gyrification during fetal development have been identified, but the impact of maternal health and the intrauterine environment has been largely overlooked. Recent evidence suggests that the intrauterine environment has a significant impact on the normal folding of the fetal cerebral cortex. This article reviews evidence for the effect of the most common intrauterine alterations on the normal development of the cortical folding in the fetus...
October 16, 2018: Journal of Physiology
Ching-Yi Tsai, Yan-Yuen Poon, Julie Y H Chan, Samuel H H Chan
By application of diffusion tensor imaging (DTI) as a physiological tool to evaluate changes in functional connectivity between key brain stem nuclei in the baroreflex neural circuits of mice and rats, recent work revealed several hitherto unidentified phenomena regarding baroreflex functionality. (1) The presence of robust functional connectivity between nucleus tractus solitarii (NTS) and nucleus ambiguus (NA) or rostral ventrolateral medulla (RVLM) offers a holistic view on the moment-to-moment modus operandi of the cardiac vagal baroreflex or baroreflex-mediated sympathetic vasomotor tone...
October 16, 2018: Journal of Physiology
Dorte E Steenberg, Nichlas B Jørgensen, Jesper B Birk, Kim A Sjøberg, Bente Kiens, Erik A Richter, Jørgen F P Wojtaszewski
KEYPOINTS: A single bout of exercise is capable of increasing insulin sensitivity in human skeletal muscle. Whether this ability is affected by training status is not clear. Studies in mice suggest that the AMPK-TBC1D4 signalling axis is important for the increased insulin-stimulated glucose uptake after a single bout of exercise. This study is the first longitudinal intervention study to show that, while exercise training increases insulin-stimulated glucose uptake in skeletal muscle at rest, it diminishes the ability of a single bout of exercise to enhance muscle insulin-stimulated glucose uptake...
October 16, 2018: Journal of Physiology
Sandor Koszegi, Agnes Molnar, Lilla Lenart, Judit Hodrea, Dora Bianka Balogh, Tamas Lakat, Edgar Szkibinszkij, Adam Hosszu, Nadja Sparding, Federica Genovese, Laszlo Wagner, Adam Vannay, Attila J Szabo, Andrea Fekete
KEY POINTS SUMMARY: Increased activation of the renin-angiotensin-aldosterone system (RAAS) and elevated growth factor production have crucial importance in the development of renal fibrosis leading to diabetic kidney disease. The aim of this study was to provide evidence for the antifibrotic potential of RAAS inhibitor (RAASi) treatment and to explore the exact mechanism of this protective effect. We found that RAASi ameliorate diabetes-induced renal interstitial fibrosis and decrease profibrotic growth factor production...
October 16, 2018: Journal of Physiology
Tze-Huan Lei, James D Cotter, Zachary J Schlader, Stephen R Stannard, Blake G Perry, Matthew J Barnes, Toby Mündel
KEY POINTS: One in two female athletes chronically take a combined, mono-phasic oral contraceptive pill (OCP). Previous thermoregulatory investigations having theorised that an endogenous rhythm of the menstrual cycle still occurs with OCP usage. Forthcoming large international sporting events will expose female athletes to hot environments differing in their thermal profile, yet few data exist on how trained women will respond from both a thermoregulatory and performance standpoint. We demonstrated here that a small endogenous rhythm of the menstrual cycle still affects Tcore, and that chronic OCP use attenuates the sweating response but behavioural thermoregulation is maintained...
October 15, 2018: Journal of Physiology
Wenli Dai, Christopher Weber
No abstract text is available yet for this article.
October 15, 2018: Journal of Physiology
Piotr Sirko, Jonathan E Gale, Jonathan F Ashmore
Intercellular Ca2+ waves are increases in cytoplasmic Ca2+ levels that propagate between cells Periodic Ca2+ waves have been linked to gene regulation and are thought to play a crucial role in the development of our hearing epithelium the organ of Corti and the acquisition of hearing We have observed regular periodic intercellular Ca2+ waves in supporting cells of an ex vivo preparation of the adult mouse organ of Corti, the waves were found to propagate independently of extracellular ATP and were inhibited by the gap junction blockers 1-octanol and carbenoxolone...
October 15, 2018: Journal of Physiology
Damian Miles Bailey
Rising atmospheric oxygen (O2 ) levels provided a selective pressure for the evolution of O2 -dependent micro-organisms that began with the autotrophic eukaryotes. Since these primordial times, the respiring mammalian cell has become entirely dependent on the constancy of electron flow with molecular O2 serving as the terminal electron acceptor in mitochondrial oxidative phosphorylation. Indeed, the ability to "sense" O2 and maintain homeostasis is considered one of the most important roles of the central nervous system (CNS) and likely represented a major driving force in the evolution of the human brain...
October 13, 2018: Journal of Physiology
J AlexanderClark, Stuart G Campbell
KEY POINTS: Prior studies have shown variation in the functional properties of cardiomyocytes isolated from different regions of the left ventricular myocardium. We found that these region-dependent variations vanish below a tissue volume of ∼7 mm3 in the adult rat myocardium, revealing a fixed level of intrinsic relaxation rate heterogeneity that is independent of tissue volume. Within these microscopically varying cell populations, fast-relaxing cells were shown to have elevated phosphorylated troponin I compared to slow-relaxing cells...
October 13, 2018: Journal of Physiology
Hong Gao, Willian S Korim, Song T Yao, Cheryl M Heesch, Andrei V Derbenev
KEY POINTS: To maintain appropriate blood flow to various tissues of the body under a variety of physiological states, autonomic nervous system reflexes regulate regional sympathetic nerve activity and arterial blood pressure. Our data in anesthetized rats revealed that glycine released in the RVLM plays a critical role in maintaining arterial baroreflex sympathoinhibition. Manipulation of brainstem nuclei with known inputs to the RVLM (NTS and CVLM) unmasked tonic glycinergic inhibition in the RVLM...
October 12, 2018: Journal of Physiology
Souhei Sakata, Yasushi Okamura
The voltage-sensing phosphatase, VSP, consists of the voltage sensor domain (VSD) and the cytoplasmic catalytic region. The latter contains the phosphatase domain and the C2 domain, showing remarkable similarity to a tumor suppressor enzyme, PTEN. In VSP, membrane depolarization induces the conformational change in the VSD, which activates the phosphoinositide phosphatase. The final outcome of VSP is enzymatic activity of the cytoplasmic region unlike voltage-gated ion channels where conformational change of the transmembrane pore is induced by the VSD...
October 12, 2018: Journal of Physiology
E N Bardsley, D J Paterson
Cardiac sympathetic over-activity is a well-established contributor to the progression of neurogenic hypertension and heart failure, yet the underlying pathophysiology remains unclear. Recent studies have highlighted the importance of acutely regulated cyclic nucleotides and their effectors in the control of intracellular calcium and exocytosis. Emerging evidence now suggests that a significant component of sympathetic over-activity and enhanced transmission may arise from impaired cyclic nucleotide signalling, resulting from compromised phosphodiesterase activity, as well as alterations in receptor-coupled G-protein activation...
October 11, 2018: Journal of Physiology
Bryan K Becker
No abstract text is available yet for this article.
October 9, 2018: Journal of Physiology
James Kolasinski, Emily L Hinson, Amir P Divanbeighi Zand, Assen Rizov, Uzay E Emir, Charlotte J Stagg
The ability to learn new motor skills is supported by plasticity in the structural and functional organisation of the primary motor cortex in the human brain. Changes inhibitory signalling by gamma-aminobutyric acid (GABA) are thought to be crucial in inducing motor cortex plasticity. This study used magnetic resonance spectroscopy (MRS) to quantify the concentration of GABA in human motor cortex during a period of motor learning, as well as during a period of movement, and a period at rest. We report evidence for a reduction in the MRS-measured concentration of GABA specific to learning...
October 9, 2018: Journal of Physiology
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