TY - JOUR AU - Sullivan, Brian P. AU - Collins, Brittany C. AU - McMillin, Shawna L. AU - Toussaint, Elise AU - Stein, Clara Z. AU - Spangenburg, Espen E. AU - Lowe, Dawn A. TI - Ablation of skeletal muscle estrogen receptor alpha impairs contractility in male mice JF - JOURNAL OF APPLIED PHYSIOLOGY J2 - J APPL PHYSIOL VL - 136 PY - 2024 IS - 4 SP - 764 EP - 773 PG - 10 SN - 8750-7587 DO - 10.1152/japplphysiol.00714.2023 UR - https://m2.mtmt.hu/api/publication/34828355 ID - 34828355 AB - Estradiol and estrogen receptor α (ERα) have been shown to be important for the maintenance of skeletal muscle strength in females; however, little is known about the roles of estradiol and ERα in male muscle. The purpose of this study was to determine if skeletal muscle ERα is required for optimal contractility in male mice. We hypothesize that reduced ERα in skeletal muscle impairs contractility in male mice. Skeletal muscle-specific knockout (skmERαKO) male mice exhibited reduced strength across multiple muscles and several contractile parameters related to force generation and kinetics compared with wild-type littermates (skmERαWT). Isolated EDL muscle-specific isometric tetanic force, peak twitch force, peak concentric and peak eccentric forces, as well as the maximal rates of force development and relaxation were 11%–21% lower in skmERαKO compared with skmERαWT mice. In contrast, isolated soleus muscles from skmERαKO mice were not affected. In vivo peak torque of the anterior crural muscles was 20% lower in skmERαKO compared with skmERαWT mice. Muscle masses, contractile protein contents, fiber types, phosphorylation of the myosin regulatory light chain, and caffeine-elicited force did not differ between muscles of skmERαKO and skmERαWT mice, suggesting that strength deficits were not due to size, composition, or calcium release components of muscle contraction. These results indicate that in male mice, reduced skeletal muscle ERα blunts contractility to a magnitude similar to that previously reported in females; however, the mechanism may be sexually dimorphic.NEW & NOTEWORTHY We comprehensively measured in vitro and in vivo contractility of leg muscles with reduced estrogen receptor α (ERα) in male mice and reported that force generation and contraction kinetics are impaired. In contrast to findings in females, phosphorylation of myosin regulatory light chain cannot account for low force production in male skeletal muscle ERα knockout mice. These results indicate that ERα is required for optimal contractility in males and females but via sexually dimorphic means. LA - English DB - MTMT ER - TY - JOUR AU - Peták, Ferenc AU - Südy, Roberta AU - Diaper, John AU - Fontao, Fabienne AU - Bizzotto, Davide AU - Dellacà, Raffaele L. AU - Habre, Walid AU - Schranc, Álmos TI - Benefits of intratracheal and extrathoracic high-frequency percussive ventilation in a model of capnoperitoneum JF - JOURNAL OF APPLIED PHYSIOLOGY J2 - J APPL PHYSIOL VL - 136 PY - 2024 IS - 4 SP - 928 EP - 937 PG - 10 SN - 8750-7587 DO - 10.1152/japplphysiol.00881.2023 UR - https://m2.mtmt.hu/api/publication/34798171 ID - 34798171 AB - The present study examines an alternative and innovative mechanical ventilation modality in improving oxygen delivery, CO 2 clearance, and respiratory mechanical abnormalities in a clinically relevant experimental model of capnoperitoneum. Our data reveal that high-frequency oscillations combined with conventional ventilation improve gas exchange, with intratracheal oscillations being more effective than extrathoracic oscillations in this clinically relevant translational model. LA - English DB - MTMT ER - TY - JOUR AU - Rodrigues, P. AU - Orssatto, L.B.R. AU - Gagnon, D. AU - Dahhak, A. AU - Hecksteden, A. AU - Stewart, I.B. AU - Minett, G.M. TI - Passive heat therapy: a promising preventive measure for people at risk of adverse health outcomes during heat extremes JF - JOURNAL OF APPLIED PHYSIOLOGY J2 - J APPL PHYSIOL VL - 136 PY - 2024 IS - 4 SP - 677 EP - 694 PG - 18 SN - 8750-7587 DO - 10.1152/japplphysiol.00701.2023 UR - https://m2.mtmt.hu/api/publication/34778140 ID - 34778140 N1 - Institute of Physiology, Medical University of Innsbruck, Innsbruck, Austria Institute of Sport Science, Leopold-Franzens-University of Innsbruck, Innsbruck, Austria School of Exercise and Nutrition Sciences, Faculty of Health, Queensland University of Technology (QUT), Brisbane, QLD, Australia Institute for Physical Activity and Nutrition (IPAN), School of Exercise and Nutrition Sciences, Faculty of Health, Deakin University, Geelong, VIC, Australia Montreal Heart Institute, Montréal, QC, Canada School of Kinesiology and Exercise Science, Université de Montréal, Montréal, QC, Canada Export Date: 8 April 2024 CODEN: JAPHE Correspondence Address: Rodrigues, P.; Institute of Physiology, Austria; email: patrick.rodrigues@uibk.ac.at LA - English DB - MTMT ER - TY - JOUR AU - Strohm, Alexandra O. AU - O'Connor, Thomas N. AU - Oldfield, Sadie AU - Young, Sala AU - Hammond, Christian AU - Mccall, Matthew AU - Dirksen, Robert T. AU - Majewska, Ania K. TI - Cortical microglia dynamics are conserved during voluntary wheel running JF - JOURNAL OF APPLIED PHYSIOLOGY J2 - J APPL PHYSIOL VL - 136 PY - 2024 IS - 1 SP - 89 EP - 108 PG - 20 SN - 8750-7587 DO - 10.1152/japplphysiol.00311.2023 UR - https://m2.mtmt.hu/api/publication/34661776 ID - 34661776 LA - English DB - MTMT ER - TY - JOUR AU - Flensted-Jensen, Mathias AU - Kleis-Olsen, Ann-Sofie AU - Hasso, Rasmus Kinimond AU - Lindtofte, Soren AU - Perez, Juan Corral AU - Ortega-Gomez, Sonia AU - Larsen, Steen TI - Combined changes in temperature and pH mimicking exercise result in decreased efficiency in muscle mitochondria JF - JOURNAL OF APPLIED PHYSIOLOGY J2 - J APPL PHYSIOL VL - 136 PY - 2024 IS - 1 SP - 79 EP - 88 PG - 10 SN - 8750-7587 DO - 10.1152/japplphysiol.00293.2023 UR - https://m2.mtmt.hu/api/publication/34629819 ID - 34629819 LA - English DB - MTMT ER - TY - JOUR AU - Toien, Tiril AU - Nielsen, Jakob Lindberg AU - Berg, Ole Kristian AU - Brobakken, Mathias Forsberg AU - Nyberg, Stian Kwak AU - Espedal, Lars AU - Malmo, Thomas AU - Frandsen, Ulrik AU - Aagaard, Per AU - Wang, Eivind TI - The impact of life-long strength versus endurance training on muscle fiber morphology and phenotype composition in older men JF - JOURNAL OF APPLIED PHYSIOLOGY J2 - J APPL PHYSIOL VL - 135 PY - 2023 IS - 6 SP - 1360 EP - 1371 PG - 12 SN - 8750-7587 DO - 10.1152/japplphysiol.00208.2023 UR - https://m2.mtmt.hu/api/publication/34649722 ID - 34649722 LA - English DB - MTMT ER - TY - JOUR AU - Huggard, Joshua D. AU - Guluzade, Nasimi A. AU - Duffin, James AU - Keir, Daniel A. TI - The ventilatory response to modified rebreathing is unchanged by hyperoxic severity: implications for the hyperoxic hyperventilation paradox JF - JOURNAL OF APPLIED PHYSIOLOGY J2 - J APPL PHYSIOL VL - 135 PY - 2023 IS - 6 SP - 1446 EP - 1456 PG - 11 SN - 8750-7587 DO - 10.1152/japplphysiol.00455.2023 UR - https://m2.mtmt.hu/api/publication/34637756 ID - 34637756 LA - English DB - MTMT ER - TY - JOUR AU - Boyes, Natasha G. AU - Mannozzi, Joseph AU - Rapin, Nicole AU - Alvarez, Alberto AU - Al-Hassan, Mohamed-Hussein AU - Lessanework, Beruk AU - Lahti, Dana S. AU - Olver, T. Dylan AU - O'Leary, Donal S. AU - Tomczak, Corey R. TI - Augmented sympathoexcitation slows postexercise heart rate recovery JF - JOURNAL OF APPLIED PHYSIOLOGY J2 - J APPL PHYSIOL VL - 135 PY - 2023 IS - 6 SP - 1300 EP - 1311 PG - 12 SN - 8750-7587 DO - 10.1152/japplphysiol.00549.2023 UR - https://m2.mtmt.hu/api/publication/34597754 ID - 34597754 AB - Slow heart rate recovery following exercise may be influenced by persistent sympathoexcitation. This study examined 1) the effect of muscle metaboreflex activation (MMA) on heart rate recovery following dynamic exercise; and 2) whether the effect of MMA on heart rate recovery is reversible by reducing sympathoexcitation [baroreflex activation via phenylephrine (PE)] in canines. Twenty-two young adults completed control and MMA protocols during cycle ergometry at 110% ventilatory threshold with 5 min recovery. Heart rate recovery kinetics [tau (tau), amplitude, end-exercise, and end-recovery heart rate] and root mean square of successive differences (RMSSD) were measured. Five chronically instrumented canines completed control, MMA (50%-60% imposed reduction in hindlimb blood flow), and MMA with end-exercise PE infusion (MMA + PE) protocols during moderate exercise (6.4 kmh(-1)) and 3 min recovery. Heart rate recovery kinetics and MAP were measured. MAP increased during MMA versus control in canines (P < 0.001). Heart rate recovery tau was slower during MMA versus control in humans (17% slower; P = 0.011) and canines (150% slower; P = 0.002). Heart rate recovery tau was faster during MMA + PE versus MMA (40% faster; P = 0.034) and was similar to control in canines (P = 0.426). Amplitude, end-exercise, and end-recovery heart rate were similar between conditions in humans (all P >= 0.122) and in canines (all P >= 0.084). MMA decreased RMSSD in early recovery (P = 0.004). MMA-induced sympathoexcitation slows heart rate recovery and this effect is markedly attenuated with PE. Therefore, elevated sympathoexcitation via MMA impairs heart rate recovery and inhibition of this stimulus normalizes, in part, heart rate recovery. NEW & NOTEWORTHY Augmented sympathoexcitation, via muscle metaboreflex activation, functionally slows heart rate recovery in both young healthy adults and chronically instrumented canines. Furthermore, elevated sympathoexcitation corresponded with lower parasympathetic activity, as assessed by heart rate variability, during the first 3 min of recovery. Finally, sympathoinhibition, via phenylephrine infusion, normalizes heart rate recovery during muscle metaboreflex activation. LA - English DB - MTMT ER - TY - JOUR AU - Haak, Jodie L. AU - Kregel, Kevin C. AU - Bloomer, Steven A. TI - Altered accumulation of hepatic mitochondrial antioxidant proteins with age and environmental heat stress JF - JOURNAL OF APPLIED PHYSIOLOGY J2 - J APPL PHYSIOL VL - 135 PY - 2023 IS - 6 SP - 1339 EP - 1347 PG - 9 SN - 8750-7587 DO - 10.1152/japplphysiol.00610.2023 UR - https://m2.mtmt.hu/api/publication/34595619 ID - 34595619 AB - Aging impairs overall physiological function, particularly the response to environmental stressors. Repeated heat stress elevates reactive oxygen species and macromolecular damage in the livers of aged animals, likely due to mitochondrial dysfunction. The goal of this investigation was to determine potential mechanisms for mitochondrial dysfunction after heat stress by evaluating key redox-sensitive and antioxidant proteins (Sirt-3, MnSOD, Trx-2, and Ref-1). We hypothesized that heat stress would result in greater mitochondrial abundance of these proteins, but that aging would attenuate this response. For this purpose, young (6 mo) and old (24 mo) Fisher 344 rats were exposed to heat stress on two consecutive days. During each heating trial, colonic temperature was elevated to 41 degrees C during the first 60 min, and then clamped at this temperature for 30 min. Nonheated animals served as controls. At 2 and 24 h after the second heat stress, hepatic mitochondria were isolated from each animal, and then immunoblotted for Sirt-3, acetylated lysine residues (Ac-K), MnSOD, Trx-2, and Ref-1. Aging increased Sirt-3 and lowered Ac-K. In response to heat stress, Sirt-3, Ac-K, MnSOD, and Ref-1 increased in mitochondrial fractions in both young and old animals. At 2 h after the second heat stress, mitochondrial Trx-2 declined in old, but not in young animals. Our results suggest that some components of the response to heat stress are preserved with aging. However, the decline in Trx-2 represents a potential mechanism for age-related mitochondrial damage and dysfunction after heat stress. LA - English DB - MTMT ER - TY - JOUR AU - Herskind, Jon AU - Gravholt, Anders AU - Hvid, Lars G. AU - Overgaard, Kristian TI - The effect of low-frequency fatigue on the torque-velocity relationship in human quadriceps JF - JOURNAL OF APPLIED PHYSIOLOGY J2 - J APPL PHYSIOL VL - 135 PY - 2023 IS - 6 SP - 1457 EP - 1466 PG - 10 SN - 8750-7587 DO - 10.1152/japplphysiol.00637.2022 UR - https://m2.mtmt.hu/api/publication/34588387 ID - 34588387 AB - Low-frequency fatigue (LFF) is usually defined as the decline in low:high-frequency force of electrically evoked isometric muscle contractions. The influence of LFF on dynamic muscle function is not well studied. Our aim was to assess the effect of LFF on the electrically evoked torque-velocity relationship in humans. Sixteen participants underwent a series of electrically evoked knee extensions in an isokinetic dynamometer to establish torque-velocity relationships at 15 and 50 Hz using isokinetic contractions. Hereafter, fatigue was induced by five sets of 10 repetitions of maximal voluntary dynamic knee extensions. After 30 min of rest, torque-velocity tests were repeated. Maximal torque (F-max) was measured, whereas maximal contraction velocity (V-max) and maximal power (P-max) were estimated using Hill's force-velocity equation, 15:50 Hz ratios were calculated for F-max, V-max, and P(max )as markers of LFF. F(max )decreased by 40% at 15 Hz (P = 0.001) and by 15% at 50 Hz (P = 0.001) in the fatigued state. No significant change was detected for V(max )at 15 Hz [-2%, (P = 0.349)] or 50 Hz [+3% (P = 0.763)], whereas 15 and 50 Hz P-max decreased by 30% (P = 0.004) and 10% (P = 0.008), respectively. Following the fatigue protocol, the 15:50 Hz F-max ratio decreased by 31% (P < 0.001), indicating LFF. The 15:50 Hz P-max ratio also decreased by 23% (P = 0.002), whereas the 15:50 Hz Vmax ratio was unchanged (P = 0.313). In conclusion, fatiguing contractions decreased Fmax and Pmax at both high and low stimulation frequencies, whereas Vmax appeared unaffected. Nevertheless, LFF influences power production during human dynamic contractions at a range of submaximal velocities.NEW & NOTEWORTHY Force-velocity relationships were established using either low- or high-frequency electrical stimulation before and after fatiguing voluntary eccentric/concentric contractions of the knee extensors. Low-frequency fatigue was assessed by the relative decrease in low- and high-frequency maximal torque, maximal shortening velocity, and maximal power estimated by the force-velocity relationship. Low-frequency fatigue manifests itself as a large decrease in low-frequency maximal force and power with a modest decrease in high-frequency maximal force and power. Contraction velocity does not seem to decrease in the same manner. LA - English DB - MTMT ER -