Physiological reports
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Physiological reports · Nov 2019
Acute effects of resonance frequency breathing on cardiovascular regulation.
Acute slow breathing may have beneficial effects on cardiovascular regulation by affecting hemodynamics and the autonomic nervous system. Whether breathing at the resonance frequency (RF), a breathing rate that maximizes heart rate oscillations, induces differential effects to that of slow breathing is unknown. We compared the acute effects of breathing at either RF and RF + 1 breaths per minute on muscle sympathetic nervous activity (MSNA) and baroreflex function. ⋯ The sympathetic baroreflex function remained unchanged at either breathing rates. The slope of the cardiac baroreflex function was unaltered but the cardiac baroreflex efficiency was improved during both RF and RF + 1. Acute breathing at either RF or RF + 1 has similar hemodynamic and sympatho-inhibitory effects in healthy men.
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Physiological reports · Oct 2019
Differential regulation of myofibrillar proteins in skeletal muscles of septic mice.
Sepsis elicits skeletal muscle atrophy as a result of decreased total protein synthesis and/or increased total protein degradation. It is unknown how and whether sepsis differentially affects the expression of specific myofibrillar proteins in respiratory and limb muscles. In this study, we measured the effects of sepsis myofibrillar mRNAs and their corresponding protein levels in the diaphragm (DIA) and tibialis anterior (TA) muscles in a murine cecal ligation and perforation (CLP) model of sepsis. ⋯ Myosin heavy chain isoforms decreased at 24 h in the DIA and across the time-course in the TA, myosin light chain isoforms decreased across the time-course in both muscles, and troponins T and C as well as tropomyosin decreased after 24 and 48 h in both the DIA and TA. α-Actin and troponin I were unaffected by sepsis. Sepsis-induced decreases in myofibrillar protein levels coincided with decreased mRNA expressions of these proteins, suggesting that transcriptional inhibition is involved. We hypothesize that sepsis-induced muscle atrophy is mediated by decreased transcription and enhanced degradation of specific myofibrillar proteins, including myosin heavy and light chains, troponin C, troponin T, and tropomyosin.
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Physiological reports · Jul 2019
Randomized Controlled TrialEffects of all-out sprint interval training under hyperoxia on exercise performance.
All-out sprint interval training (SIT) is speculated to be an effective and time-efficient training regimen to improve the performance of aerobic and anaerobic exercises. SIT under hypoxia causes greater improvements in anaerobic exercise performance compared with that under normoxia. The change in oxygen concentration may affect SIT-induced performance adaptations. ⋯ The accumulated oxygen deficit (AOD) during 90-sec maximal exercise test significantly increased only in the NST group. The average values of mean power outputs over four bouts during the acute SIT test significantly improved only in the NST group. These findings suggest that all-out SIT might induce greater improvement in aerobic exercise performance (blood lactate curve) but impair SIT-induced enhancements in anaerobic exercise performance (AOD and mean power output).
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Physiological reports · Jul 2019
Cardiopulmonary fitness predicts postoperative major morbidity after esophagectomy for patients with cancer.
Surgery for radical treatment of esophageal cancer (EC) carries significant inherent risk. The objective identification of patients who are at high risk of complications is of importance. In this study the prognostic value of cardiopulmonary fitness variables (CPF) derived from cardiopulmonary exercise testing (CPET) was assessed in patients undergoing potentially curative surgery for EC within an enhanced recovery program. ⋯ Multivariable analysis revealed V ˙ O 2 Peak to be the only independent factor to predict major morbidity (OR 0.85, 95% CI 0.75-0.97, P = 0.018). Cumulative survival was associated with operative morbidity severity (χ2 = 4.892, df = 1, P = 0.027). These results indicate that V ˙ O 2 Peak as derived from CPET is a significant predictor of major morbidity after oesophagectomy highlighting the physiological importance of cardiopulmonary fitness.
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Physiological reports · Jul 2019
Sex is no determinant of cardioprotection by ischemic preconditioning in rats, but ischemic/reperfused tissue mass is for remote ischemic preconditioning.
We determined the impact of sex on the magnitude of cardioprotection by local and remote ischemic preconditioning (IPC and RIPC) and of ischemic/reperfused peripheral tissue mass on protection by RIPC. Hearts of female and male Lewis rats were excised, perfused with buffer, and underwent either IPC by 3 × 5/5 min global zero-flow ischemia/reperfusion (GI/R) or time-matched perfusion (TP) before 30/120 min GI/R. In a second approach, anesthetized female and male Lewis rats underwent RIPC, 3 × 5/5 min ischemia/reperfusion of one or both hindlimbs (1-RIPC or 2-RIPC), or placebo. ⋯ Infarct size after the placebo protocol and GI/R was not different between female and male hearts (36 ± 8% vs. 34 ± 5%). Sex is no determinant of IPC- and RIPC-induced cardioprotection in isolated Lewis rat hearts. RIPC-induced cardioprotection is greater with greater mass of ischemic/reperfused peripheral tissue.