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Journal of Physiology

Charles B Trelford, Stephanie Wojtowicz, Caroline A Banas
No abstract text is available yet for this article.
February 20, 2019: Journal of Physiology
R Ryley Parrish, Neela K Codadu, Connie Mackenzie-Gray Scott, Andrew J Trevelyan
KEY POINTS: There is a rapid interneuronal response to focal activity in cortex, which restrains laterally propagating activity, including spreading epileptiform activity. The interneuronal response involves intense activation of both parvalbumin (PV) and somatostatin (SST) expressing interneurons. Interneuronal bursting is time-locked to glutamatergic barrages in the pre-ictal period. Ca2+ imaging using conditional expression of GCaMP6f provides an accurate readout of the evolving firing patterns in both types of interneuron...
February 19, 2019: Journal of Physiology
Shawn D Youngstedt, Jeffrey A Elliott, Daniel F Kripke
KEY POINTS: Exercise elicits circadian phase-shifting effects, but additional information is needed. The phase-response curve describing the magnitude and direction of circadian rhythm phase shifts depending on the time of the zeigeber (time cue) stimulus is the most fundamental chronobiological tool for alleviating circadian misalignment and related morbidity. 51 older and 48 young adults followed a circadian rhythms measurement protocol for up to 5.5 days, and performed 1 h of moderate treadmill exercise for 3 consecutive days at one of 8 times of day/night...
February 19, 2019: Journal of Physiology
Francisco J Alvarez
No abstract text is available yet for this article.
February 18, 2019: Journal of Physiology
Alexander U Fischer, Nicolas Ic Müller, Thomas Deller, Domenico Del Turco, Jonas O Fisch, Désirée Griesemer, Kathrin Kattler, Ayse Maraslioglu, Vera Roemer, Matthew A Xu-Friedman, Jörn Walter, Eckhard Friauf
KEY POINTS: The LSO, a brainstem hub involved in sound localization, integrates excitatory and inhibitory inputs from the ipsilateral and the contralateral ear, respectively. In gerbils and rats, inhibition to the LSO reportedly shifts from GABAergic to glycinergic within the first three postnatal weeks. Surprisingly, we found no evidence for synaptic GABA signalling during this time window in mouse LSO principal neurons. However, we found that presynaptic GABAB Rs modulate Ca2+ influx into MNTB axon terminals, resulting in reduced synaptic strength...
February 18, 2019: Journal of Physiology
Shanna Hamilton, Iuliia Polina, Radmila Terentyeva, Peter Bronk, Tae Yun Kim, Karim Roder, Richard T Clements, Gideon Koren, Bum-Rak Choi, Dmitry Terentyev
KEY POINTS SUMMARY: Small-conductance Ca2+ -activated K+ (SK) channels expressed in ventricular myocytes are dormant in health yet become functional in cardiac disease. SK channels are voltage independent and their gating is controlled by intracellular [Ca2+ ] in a biphasic manner. Submicromolar [Ca2+ ] activates the channel via constitutively-bound calmodulin, while higher [Ca2+ ] exerts inhibitory effect during depolarization. Using a rat model of cardiac hypertrophy induced by thoracic aortic banding, we found that functional upregulation of SK2 channels in hypertrophic rat ventricular cardiomyocytes is driven by PKA phosphorylation...
February 16, 2019: Journal of Physiology
Alexander G Nickel, Michael Kohlhaas, Edoardo Bertero, Daniel Wilhelm, Michael Wagner, Vasco Sequeira, Michael M Kreusser, Matthias Dewenter, Reinhard Kappl, Markus Hoth, Jan Dudek, Johannes Backs, Christoph Maack
KEY POINTS: Mitochondrial Ca2+ uptake stimulates the Krebs cycle to regenerate the reduced forms of pyridine nucleotides (NADH, NADPH and FADH2 ) required for ATP production and ROS elimination. It was previously proposed that Ca2+ /calmodulin-dependent protein kinase II (CaMKII) regulates mitochondrial Ca2+ uptake via MCU phosphorylation. We used two mouse models with either global deletion of CaMKIIδ (CaMKIIδ KO) or cardiomyocyte-specific deletion of CaMKIIδ and γ (CaMKIIδ/γ DKO) to interrogate whether CaMKII controls mitochondrial Ca2+ uptake in isolated mitochondria and during β-adrenergic stimulation in cardiac myocytes...
February 16, 2019: Journal of Physiology
N N Chattergoon, S Louey, T Scanlan, I Lindgren, G D Giraud, K L Thornburg
KEY POINTS: Plasma thyroid hormone (T3 ) concentrations rise near the end of gestation and are known to inhibit proliferation and stimulate maturation of cardiomyocytes before birth. Thyroid hormone receptors are required for thyroid hormone action in fetal cardiomyocytes. Loss of TRα1 abolishes T3 signalling through ERK and AKT in fetal cardiomyocytes. The expression of thyroid receptors alpha 1 (TRα1) and beta 1 (TRβ1) in ovine fetal myocardium increases with age, though TRα1 levels always remain higher than those of TRβ1...
February 16, 2019: Journal of Physiology
William Schmidt, Anthony Cammarato
Striated muscle contraction is regulated by Ca2+ -dependent modulation of myosin cross-bridge binding to F-actin by the thin filament troponin (Tn)-tropomyosin (Tm) complex. In the absence of Ca2+ , Tn binds to actin and constrains Tm to an azimuthal location where it sterically occludes myosin binding sites along the thin filament surface. This limits force production and promotes muscle relaxation. In addition to Tn-actin interactions, inhibitory Tm positioning requires associations between other thin filament constituents...
February 15, 2019: Journal of Physiology
A Del Vecchio, F Negro, A Holobar, A Casolo, J P Folland, F Felici, D Farina
KEY POINTS: We propose and validate a method to accurately identify the activity of populations of motor neurons during contractions at maximal rate of force development in humans. The behaviour of the motor neuron pool during rapid voluntary contractions in humans is presented. We show with this approach that the motor neuron recruitment speed and maximal motor unit discharge rate largely explains the individual ability in generating rapid force contractions. The results also indicate that the synaptic inputs received by the motor neurons before force is generated dictate human potential to generate force rapidly...
February 15, 2019: Journal of Physiology
Melina P da Silva, Davi José A Moraes, Leni G H Bonagamba, André de Souza Mecawi, Wamberto A Varanda, Benedito H Machado
KEY POINTS: Acute hypoxia induces active expiration in Rectus Abdominis (RA) muscles in conscious freely moving rats, but its overall contribution is smaller than internal oblique (IO) muscles. Tonically active and silent RA motoneurons were identified in in vitro preparations of rat spinal cords. Sustained hypoxia (SH) increased the synaptic strength and induced morphological changes in tonically active RA motoneurons. Expiratory RA motoneurons were recorded in the in situ preparation and SH enhanced the excitability as well as the synaptic transmission in those firing during the stage 2 expiration...
February 12, 2019: Journal of Physiology
Maria A Battistone, Maria Merkulova, Yoo-Jin Park, Maria A Peralta, Flavia Gombar, Dennis Brown, Sylvie Breton
KEY POINTS: In the epididymis, elaborate communication networks between epithelial cells are important to establish an optimal acidic luminal environment for the maturation and storage of spermatozoa, which is essential for male fertility. Proton secretion by epididymal clear cells is achieved via the proton pumping V-ATPase located in their apical membrane. Here, we dissect the molecular mechanisms by which clear cells respond to luminal ATP and adenosine to modulate their acidifying activity via the adenosine receptor ADORA2B and the pH-sensitive ATP receptor P2 × 4...
February 12, 2019: Journal of Physiology
Maria Seron-Ferre, Laura Bennet
No abstract text is available yet for this article.
February 11, 2019: Journal of Physiology
Andrea Estrada, Zackary Valenti, Daniel Lark
No abstract text is available yet for this article.
February 11, 2019: Journal of Physiology
Ege T Kavalali
Action potential driven neuronal signaling drives several electrical and biochemical processes in the nervous system. However, neurons can maintain synaptic communication and signaling under resting conditions independent of activity. Importantly, these processes are regulated by Ca2+ signals that occur at rest. Several studies have suggested that opening of voltage-gated Ca2+ channels near resting membrane potentials, activation of NMDA receptors in the absence of depolarization or Ca2+ release from intracellular stores can drive neurotransmitter release as well as subsequent signalling in the absence of action potentials...
February 8, 2019: Journal of Physiology
Alexei Verkhrastky, Verena Untiet, Christine R Rose
Astrocytes are homeostatic and protective cells of the central nervous system. Astroglial homeostatic responses are tightly coordinated with neuronal activity. Astrocytes maintain neuronal excitability through regulation of extracellular ion concentrations as well as assisting and modulating synaptic transmission by uptake and catabolism of major neurotransmitters. Moreover, they support neuronal metabolism and detoxify ammonium and reactive oxygen species. Astroglial homeostatic actions are initiated and controlled by intercellular signalling of ions, including Ca2+ , Na+ , Cl- , H+ and possibly K+ ...
February 7, 2019: Journal of Physiology
Yeukai Tm Mangwiro, James Sm Cuffe, Dayana Mahizir, Kristina Anevska, Sogand Gravina, Tania Romano, Karen M Moritz, Jessica F Briffa, Mary E Wlodek
KEY POINTS: Fetal growth is dependent on effective placental nutrient transportation, which is regulated by mTORC1 modulation of nutrient transporter expression. These transporters are dysregulated in pregnancies affected by uteroplacental insufficiency and maternal obesity. Nutrient transporters and mTOR were altered in placentae of mothers born growth restricted compared to normal birth weight dams, with maternal diet- and fetal sex-specific responses. Exercise initiated during pregnancy (PregEx) downregulated MTOR protein expression, despite an increase in mTOR activation in male associated placentae, and reduced nutrient transporter gene abundance, which was also dependent on maternal diet and fetal sex...
February 7, 2019: Journal of Physiology
Ryan Debi, Robert Lakin, Steven Spector
No abstract text is available yet for this article.
February 7, 2019: Journal of Physiology
David P Ferguson, Tanner O Monroe, Celia Pena Heredia, Ryan E Fleischman, George G Rodney, George E Taffet, Marta L Fiorotto
KEY POINTS: Impaired growth during fetal life can reprogramme heart development and increase the risk for long-term cardiovascular dysfunction. It is uncertain if the developmental window during which the heart is vulnerable to reprogramming as a result of inadequate nutrition extends into the postnatal period. We found that adult female mice that had been undernourished only from birth to 3 wk of age had disproportionately smaller hearts compared to males with thinner ventricle walls and more mononucleated cardiomyocytes...
February 7, 2019: Journal of Physiology
Alessandro Del Vecchio, Andrea Casolo, Francesco Negro, Matteo Scorcelletti, Ilenia Bazzucchi, Roger Enoka, Francesco Felici, Dario Farina
KEY POINTS: Previous studies have indicated that several weeks of strength training is sufficient to elicit significant adaptations in the neural drive sent to the muscles. There are few data, however, on the changes elicited by strength training in the recruitment and rate coding of motor units during voluntary contractions. We show for the first time that the discharge characteristics of motor units in the tibialis anterior muscle tracked across the intervention are changed by 4 weeks of strength training with isometric voluntary contractions...
February 6, 2019: Journal of Physiology
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