Heat-related changes in the velocity and kinetic energy of flowing blood influence the human heart's output during hyperthermia
J Physiol. 2024 May 1. doi: 10.1113/JP285760. Online ahead of print.ABSTRACTPassive whole-body hyperthermia increases limb blood flow and cardiac output ( Q ̇ $\dot Q$ ), but the interplay between peripheral and central thermo-haemodynamic mechanisms remains unclear. Here we tested the hypothesis that local hyperthermia-induced alterations in peripheral blood flow and blood kinetic energy modulate flow to the heart and Q ̇ $\dot Q$ . Body temperatures, regional (leg, arm, head) and systemic haemodynamics, and left ventricular (LV) volumes and functions were assessed in eight healthy males during: (1) 3 h control (nor...
Source: The Journal of Physiology - May 1, 2024 Category: Physiology Authors: Kazuhito Watanabe Nuno Koch Esteves Oliver R Gibson Koichi Akiyama Sumie Watanabe Jos é González-Alonso Source Type: research
Lactate and hydrogen ions play a predominant role in evoking the exercise pressor reflex during ischaemic contractions but not during freely perfused contractions
J Physiol. 2024 Apr 29. doi: 10.1113/JP286488. Online ahead of print.ABSTRACTWe investigated the role played by lactate and hydrogen in evoking the exercise pressor reflex (EPR) in decerebrated rats whose hindlimb muscles were either freely perfused or ischaemic. Production of lactate and hydrogen by the contracting hindlimb muscles was manipulated by knocking out the myophosphorylase gene (pygm). In knockout rats (pygm-/-; n = 13) or wild-type rats (pygm+/+; n = 13), the EPR was evoked by isometrically contracting the triceps surae muscles. Blood pressure, tension, blood flow, renal sympathetic nerve activity and blood la...
Source: The Journal of Physiology - April 30, 2024 Category: Physiology Authors: Guillaume P Ducrocq Laura Anselmi Victor Ruiz-Velasco Marc P Kaufman Source Type: research
Regulation of cardiomyocyte t-tubule structure by preload and afterload: Roles in cardiac compensation and decompensation
In conclusion, modest augmentation of workload promotes compensatory increases in t-tubule density and Ca2+ cycling, whereas this adaptation is reversed in overloaded hearts during heart failure progression. KEY POINTS: Excised papillary muscle experiments demonstrated a bell-shaped relationship between cardiomyocyte t-tubule density and workload (preload or afterload), which was only present when muscles were electrically stimulated. The in vivo heart at baseline is positioned on the rising phase of this curve because moderate increases in preload (mice with brief aortic shunt surgery, patients with mitral valve regurgita...
Source: The Journal of Physiology - April 30, 2024 Category: Physiology Authors: Marianne Ruud Michael Frisk Arne Olav Melleby Per Andreas Norseng Belal A Mohamed Jia Li Jan Magnus Aronsen Ingunn E Setterberg Joanna Jakubiczka Isabelle van Hout Sean Coffey Xin Shen St åle Nygård Ida G Lunde Theis T ønnessen Peter P Jones Ivar Sjaas Source Type: research
Specificity of early motor unit adaptations with resistive exercise training
J Physiol. 2024 Apr 30. doi: 10.1113/JP282560. Online ahead of print.ABSTRACTAfter exposure of the human body to resistive exercise, the force-generation capacity of the trained muscles increases significantly. Despite decades of research, the neural and muscular stimuli that initiate these changes in muscle force are not yet fully understood. The study of these adaptations is further complicated by the fact that the changes may be partly specific to the training task. For example, short-term strength training does not always influence the neural drive to muscles during the early phase (<100 ms) of force development in ...
Source: The Journal of Physiology - April 30, 2024 Category: Physiology Authors: Alessandro Del Vecchio Roger Maro Enoka Dario Farina Source Type: research
Cerebral blood flow regulation in hypobaric hypoxia: role of haemoconcentration
J Physiol. 2024 Apr 30. doi: 10.1113/JP285169. Online ahead of print.ABSTRACTDuring acute hypoxic exposure, cerebral blood flow (CBF) increases to compensate for the reduced arterial oxygen content (CaO2). Nevertheless, as exposure extends, both CaO2 and CBF progressively normalize. Haemoconcentration is the primary mechanism underlying the CaO2 restoration and may therefore explain, at least in part, the CBF normalization. Accordingly, we tested the hypothesis that reversing the haemoconcentration associated with extended hypoxic exposure returns CBF towards the values observed in acute hypoxia. Twenty-three healthy lowla...
Source: The Journal of Physiology - April 30, 2024 Category: Physiology Authors: Rachel Turner Peter Rasmussen Hannes Gatterer Joshua C Tremblay Johanna Roche Giacomo Strapazzon Giulia Roveri Justin Lawley Christoph Siebenmann Source Type: research
Electrophysiology and 3D-imaging reveal properties of human intracardiac neurons and increased excitability with atrial fibrillation
J Physiol. 2024 Apr 30. doi: 10.1113/JP286278. Online ahead of print.ABSTRACTAltered autonomic input to the heart plays a major role in atrial fibrillation (AF). Autonomic neurons termed ganglionated plexi (GP) are clustered on the heart surface to provide the last point of neural control of cardiac function. To date the properties of GP neurons in humans are unknown. Here we have addressed this knowledge gap in human GP neuron structure and physiology in patients with and without AF. Human right atrial GP neurons embedded in epicardial adipose tissue were excised during open heart surgery performed on both non-AF and AF p...
Source: The Journal of Physiology - April 30, 2024 Category: Physiology Authors: J L Ashton B Prince G Sands L Argent M Anderson J E G Smith A Tedoldi A Ahmad D Baddeley A G Pereira N Lever T Ramanathan B H Smaill Johanna M Montgomery Source Type: research
Lactate and hydrogen ions play a predominant role in evoking the exercise pressor reflex during ischaemic contractions but not during freely perfused contractions
J Physiol. 2024 Apr 29. doi: 10.1113/JP286488. Online ahead of print.ABSTRACTWe investigated the role played by lactate and hydrogen in evoking the exercise pressor reflex (EPR) in decerebrated rats whose hindlimb muscles were either freely perfused or ischaemic. Production of lactate and hydrogen by the contracting hindlimb muscles was manipulated by knocking out the myophosphorylase gene (pygm). In knockout rats (pygm-/-; n = 13) or wild-type rats (pygm+/+; n = 13), the EPR was evoked by isometrically contracting the triceps surae muscles. Blood pressure, tension, blood flow, renal sympathetic nerve activity and blood la...
Source: The Journal of Physiology - April 30, 2024 Category: Physiology Authors: Guillaume P Ducrocq Laura Anselmi Victor Ruiz-Velasco Marc P Kaufman Source Type: research
Regulation of cardiomyocyte t-tubule structure by preload and afterload: Roles in cardiac compensation and decompensation
In conclusion, modest augmentation of workload promotes compensatory increases in t-tubule density and Ca2+ cycling, whereas this adaptation is reversed in overloaded hearts during heart failure progression. KEY POINTS: Excised papillary muscle experiments demonstrated a bell-shaped relationship between cardiomyocyte t-tubule density and workload (preload or afterload), which was only present when muscles were electrically stimulated. The in vivo heart at baseline is positioned on the rising phase of this curve because moderate increases in preload (mice with brief aortic shunt surgery, patients with mitral valve regurgita...
Source: The Journal of Physiology - April 30, 2024 Category: Physiology Authors: Marianne Ruud Michael Frisk Arne Olav Melleby Per Andreas Norseng Belal A Mohamed Jia Li Jan Magnus Aronsen Ingunn E Setterberg Joanna Jakubiczka Isabelle van Hout Sean Coffey Xin Shen St åle Nygård Ida G Lunde Theis T ønnessen Peter P Jones Ivar Sjaas Source Type: research
Specificity of early motor unit adaptations with resistive exercise training
J Physiol. 2024 Apr 30. doi: 10.1113/JP282560. Online ahead of print.ABSTRACTAfter exposure of the human body to resistive exercise, the force-generation capacity of the trained muscles increases significantly. Despite decades of research, the neural and muscular stimuli that initiate these changes in muscle force are not yet fully understood. The study of these adaptations is further complicated by the fact that the changes may be partly specific to the training task. For example, short-term strength training does not always influence the neural drive to muscles during the early phase (<100 ms) of force development in ...
Source: The Journal of Physiology - April 30, 2024 Category: Physiology Authors: Alessandro Del Vecchio Roger Maro Enoka Dario Farina Source Type: research
Cerebral blood flow regulation in hypobaric hypoxia: role of haemoconcentration
J Physiol. 2024 Apr 30. doi: 10.1113/JP285169. Online ahead of print.ABSTRACTDuring acute hypoxic exposure, cerebral blood flow (CBF) increases to compensate for the reduced arterial oxygen content (CaO2). Nevertheless, as exposure extends, both CaO2 and CBF progressively normalize. Haemoconcentration is the primary mechanism underlying the CaO2 restoration and may therefore explain, at least in part, the CBF normalization. Accordingly, we tested the hypothesis that reversing the haemoconcentration associated with extended hypoxic exposure returns CBF towards the values observed in acute hypoxia. Twenty-three healthy lowla...
Source: The Journal of Physiology - April 30, 2024 Category: Physiology Authors: Rachel Turner Peter Rasmussen Hannes Gatterer Joshua C Tremblay Johanna Roche Giacomo Strapazzon Giulia Roveri Justin Lawley Christoph Siebenmann Source Type: research
Practical considerations for continuous glucose monitoring in elite athletes with type 1 diabetes mellitus: A narrative review
J Physiol. 2024 Apr 28. doi: 10.1113/JP285836. Online ahead of print.ABSTRACTType 1 diabetes mellitus (T1DM) refers to a metabolic condition where a lack of insulin impairs the usual homeostatic mechanisms to control blood glucose levels. Historically, participation in competitive sport has posed a challenge for those with T1DM, where the dynamic changes in blood glucose during exercise can result in dangerously high (hyperglycaemia) or low blood glucoses (hypoglycaemia) levels. Over the last decade, research and technological development has enhanced the methods of monitoring and managing blood glucose levels, thus reduci...
Source: The Journal of Physiology - April 29, 2024 Category: Physiology Authors: Gurneet Brar Sean Carmody Alistair Lumb Andrew Shafik Chris Bright Robert C Andrews Source Type: research
Correction to 'Physiological and pathophysiological roles of the KCNK3 potassium channel in the pulmonary circulation and the heart'
J Physiol. 2024 Apr 28. doi: 10.1113/JP286737. Online ahead of print.NO ABSTRACTPMID:38678577 | DOI:10.1113/JP286737 (Source: The Journal of Physiology)
Source: The Journal of Physiology - April 28, 2024 Category: Physiology Source Type: research
Correction to 'Physiological and pathophysiological roles of the KCNK3 potassium channel in the pulmonary circulation and the heart'
J Physiol. 2024 Apr 28. doi: 10.1113/JP286737. Online ahead of print.NO ABSTRACTPMID:38678577 | DOI:10.1113/JP286737 (Source: The Journal of Physiology)
Source: The Journal of Physiology - April 28, 2024 Category: Physiology Source Type: research
Recurrence of ventricular fibrillation in out-of-hospital cardiac arrest: Clinical evidence and underlying ionic mechanisms
J Physiol. 2024 Apr 25. doi: 10.1113/JP284621. Online ahead of print.ABSTRACTDefibrillation remains the optimal therapy for terminating ventricular fibrillation (VF) in out-of-hospital cardiac arrest (OHCA) patients, with reported shock success rates of ∼90%. A key persistent challenge, however, is the high rate of VF recurrence (∼50-80%) seen during post-shock cardiopulmonary resuscitation (CPR). Studies have shown that the incidence and time spent in recurrent VF are negatively associated with neurologically-intact survival. Recurrent VF also results in the administration of extra shocks at escalating energy levels, ...
Source: The Journal of Physiology - April 25, 2024 Category: Physiology Authors: Sandeep V Pandit Joshua W Lampe Annemarie E Silver Source Type: research
Resveratrol in renal health: bridging therapeutic gaps from acute kidney injury to chronic disease prevention
J Physiol. 2024 Apr 25. doi: 10.1113/JP286658. Online ahead of print.NO ABSTRACTPMID:38662688 | DOI:10.1113/JP286658 (Source: The Journal of Physiology)
Source: The Journal of Physiology - April 25, 2024 Category: Physiology Authors: Satriyo Dwi Suryantoro Gilang Iwanoski Henry Sutanto Bagus Aulia Mahdi Source Type: research
