American journal of physiology. Regulatory, integrative and comparative physiology最新文献

{"title":"Water deprivation induces a systemic pro-catabolic state that differentially affects oxidative and glycolytic skeletal muscles in male mice.","authors":"João da Cruz-Filho, Daniely Messias Costa, Tatiane Oliveira Santos, Raquel Prado da Silva, Hevely Catharine Anjos-Santos, Naima Jamile Santos Marciano, Roger Rodríguez-Gúzman, Ana Beatriz Henrique-Santos, João Eduardo Conceição Melo, Daniel Badauê-Passos, David Murphy, Andre Souza Mecawi, Danilo Lustrino","doi":"10.1152/ajpregu.00187.2024","DOIUrl":"https://doi.org/10.1152/ajpregu.00187.2024","url":null,"abstract":"<p><p>Dehydration, characterized by the loss of total body water and/or electrolytes due to diseases or inadequate fluid intake, is prevalent globally but often underestimated. Its contribution to long-term chronic diseases and sarcopenia is recognized, yet the mechanisms involved in systemic and muscle protein metabolism during dehydration remain unclear. This study investigated metabolic adaptations in a 36-hour water deprivation (WD) model of mice. Male C57BL/6 mice underwent 36-h WD or pair-feeding at rest, with assessments of motor skills along with biochemical, and metabolic parameters. Dehydration was confirmed by hypernatremia, body mass loss, hyporexia, and increased activity of vasopressinergic and oxytocinergic neurons compared to controls. These results were associated with liver mass loss, decreased glycaemia, and increased cholesterolemia. Additionally, increased VO₂ and a decreased respiratory exchange ratio indicated reduced carbohydrate consumption and potentially increased protein use during dehydration. Thus, skeletal muscle protein metabolism was evaluated due to its high protein content. In the oxidative muscles of the WD group, total and proteasomal proteolysis increased, which was associated with decreased Akt-mediated intracellular signaling. Interestingly, there was an increase in fiber cross-sectional area, likely due to higher muscle water content caused by increased intracellular osmolality induced by protein catabolism products. Conversely, no changes were observed in protein turnover or water content in glycolytic muscles. These findings suggest that short-term WD imposes a pro-catabolic state, depleting protein content in skeletal muscle. However, skeletal muscle may respond differently to dehydration based on its phenotype and might adapt for a limited time.</p>","PeriodicalId":7630,"journal":{"name":"American journal of physiology. Regulatory, integrative and comparative physiology","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142492998","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Gulf toadfish (<i>Opsanus beta</i>) urinary bladder ion and water transport is enhanced by acclimation to higher salinity to serve water balance.","authors":"Erik John Folkerts, Martin Grosell","doi":"10.1152/ajpregu.00077.2024","DOIUrl":"https://doi.org/10.1152/ajpregu.00077.2024","url":null,"abstract":"<p><p>Marine teleosts experience ion gain and water loss in their natural habitats. Among other tissues, the urinary bladder epithelium of marine fishes has been shown to actively transport ions to facilitate water absorption. However, transport properties of the urinary bladder epithelium of marine fishes and its plasticity in altered ambient salinities is relatively under-investigated. We describe urinary bladder epithelium electrophysiology, water flux, and expressions of ion transporters in urinary bladder tissue of Gulf toadfish (<i>Opsanus beta</i>) acclimated to either 35 ppt or 60 ppt seawater. Water absorption in bladder sac preparations increased ~ 350% upon acclimation to 60 ppt. Increases in water transport coincided with a significant ~ 137% increase in urinary bladder tissue mucosal-to-serosal short circuit current (<i>I_sc</i>) and a ~ 56% decrease in tissue membrane resistance. Collectively, these metrics indicate that an active electrogenic system facilitates water absorption via Na⁺ (and Cl^-) transport in urinary bladder tissue. Furthermore, pharmacological inhibition of urinary bladder tissue <i>I_sc</i> and expression of a suite of ion transporters and channels previously unidentified in this tissue provide mechanistic insights into the transport processes responsible for water flux. Analysis of water transport to overall Gulf toadfish water balance reveals a modest water conservation role for the urinary bladder of ~ 0.5% of total water absorption in 35 ppt and 1.9% in 60 ppt acclimated toadfish. These results emphasize that electrogenic ion transport facilitates water-absorptive properties of the urinary bladder in Gulf toadfish - a process that is regulated to facilitate water homeostasis.</p>","PeriodicalId":7630,"journal":{"name":"American journal of physiology. Regulatory, integrative and comparative physiology","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142492995","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The relationships between age, sex and exercise intensity on cerebral artery haemodynamics during isometric handgrip exercise.","authors":"Jodie L Koep, Bert Bond, Chloe E Taylor, Alan R Barker, Stefanie L Ruediger, Faith K Pizzey, Jeff S Coombes, Tom G Bailey","doi":"10.1152/ajpregu.00014.2024","DOIUrl":"https://doi.org/10.1152/ajpregu.00014.2024","url":null,"abstract":"<p><p>Age and sex may alter the cerebral blood flow (CBF) responses to acute isometric exercise, via associated elevations in mean arterial pressure (MAP) and sympathetic activation. Our aim was to determine the relationships between age, sex and exercise intensity on cerebrovascular responses to isometric handgrip exercise. In 78 healthy adults (18-80 years, N=42 female), cerebrovascular responses were assessed during two minute isometric exercise bouts at three intensities (15, 30, 45% maximal voluntary contraction). Intracranial responses of the middle cerebral artery (MCA) and posterior cerebral artery (PCA) velocity (v) were measured using transcranial Doppler ultrasound. Extracranial responses of the internal carotid artery (ICA) and vertebral artery (VA) were assessed using Duplex ultrasound. Cardiopulmonary haemodynamic and neural parameters were measured throughout, including muscle sympathetic nerve activity, end-tidal carbon dioxide, and MAP. There were significant positive relationships between exercise intensity and the cerebral responses of the MCAv (P<0.001) and PCAv (P=0.005). There were no effects of intensity on ICA and VA responses (P>0.05), despite intensity-dependent increases in MAP (P<0.001). The increased MCAv response to exercise was blunted with advancing age (P=0.01) with no influence of sex (P=0.86). The present study provides data on age, sex and intensity specific relationships with intracranial and extracranial cerebrovascular responses to isometric exercise. Despite similar ICA, VA, and PCA responses, MCAv responses were attenuated with advancing age during handgrip exercise with no sex dependent influence. Further, intracranial responses were intensity dependent, whereas extracranial blood flow, shear-stress and velocity responses were similarly increased at all intensities during handgrip exercise.</p>","PeriodicalId":7630,"journal":{"name":"American journal of physiology. Regulatory, integrative and comparative physiology","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142492997","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Is muscle sympathetic nerve activity associated with cerebral blood velocity? A partial coherence analysis.","authors":"Edgar Toschi-Dias, Ricardo C Nogueira, Edna O Silva, Graziela Amaro-Vicente, Carlos E Negrão, Maria Urbana P B Rondon, Ronney B Panerai","doi":"10.1152/ajpregu.00112.2024","DOIUrl":"https://doi.org/10.1152/ajpregu.00112.2024","url":null,"abstract":"<p><p>Despite some evidence, the role of sympathetic nerve activity in the regulation of cerebral blood flow remains controversial. In humans, muscle sympathetic nervous activity (MSNA) is the only direct measure of sympathetic nerve activity that can be recorded with sufficient temporal resolution, to allow association with dynamic regulation of cerebral blood velocity (CBv). This study tested the hypothesis that MSNA is associated with the regulation of CBv at rest and during different physiological maneuvers. Nine healthy subjects underwent two sympathoexcitatory maneuvers: <i>i</i>) isometric handgrip exercise (HGR), and <i>ii</i>) cold pressor test (CPT). Mean arterial pressure (MAP, oscillometric method), CBv (transcranial Doppler ultrasound), and MSNA (microneurography) were measured continuously during experimental protocols. Ordinary and partial coherences of the MAP, CBv and MSNA time series were estimated by transfer function analysis in the low-frequency range (LF: 0.07-0.20 Hz), using MAP and MSNA as inputs and CBv as the output variable. When the influence of MSNA was taken into account, the partial coherences between MAP and CBv were considerably reduced at baseline (<i>P</i><0.01), HGR (<i>P</i>=0.02), and CPT (<i>P</i><0.01). Similarly, when the influence of MAP was taken into account, the coherence between MSNA and CBv was considerably reduced at baseline (<i>P</i><0.01), HGR (<i>P</i>=0.02), and CPT (<i>P</i>=0.01), leading to the conclusion, that MSNA was associated to dynamic regulation of CBv. Partial coherence analysis is a promising method for assessing the influence of the sympathetic nervous system on cerebral hemodynamics.</p>","PeriodicalId":7630,"journal":{"name":"American journal of physiology. Regulatory, integrative and comparative physiology","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142492996","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cerebral Vasomotor Reactivity to Carbon Dioxide Using the Rebreathe Technique: Assessment of Within-day and Between-day Repeatability.","authors":"Damsara Nandadeva, Rachel J Skow, Zachary T Martin, Jordan C Patik, Ziba Taherzadeh, Alison Ortiz, Yungfei Kao, Paul J Fadel, R Matthew Brothers","doi":"10.1152/ajpregu.00030.2024","DOIUrl":"https://doi.org/10.1152/ajpregu.00030.2024","url":null,"abstract":"<p><p>The cerebral vasodilator response to increased arterial carbon dioxide (CO₂) concentration, termed cerebral vasomotor reactivity (CVMR), is used to assess cerebral vascular function. We sought to assess the within-day and between-day repeatability of CVMR to rebreathing-induced hypercapnia. Twelve healthy adults performed a <i>within-day short interval</i> protocol (17±2 minutes between trials), ten performed <i>a within-day long interval</i> protocol (145±16 minutes between trials), and seventeen performed a <i>between-day</i> protocol (5±2 days between visits). Repeatability of the slope of the percent change in middle cerebral artery mean blood velocity (%MCAv_mean) and cerebral vascular conductance index (%CVCi), to the change in partial pressure of end-tidal CO₂ (PETCO₂) between the two trials/days was assessed. <i>Within-day short interval</i> %MCAv_mean slope demonstrated fair to excellent repeatability (intraclass correlation, ICC=0.92 [95% confidence interval 0.72-0.98]; p<0.001) while %CVCi slope showed more variability (ICC=0.84 [0.47-0.95]; p=0.002]). <i>Within-day long interval</i>, %MCAv_mean (ICC=0.95 [0.80-0.99]) and %CVCi (ICC=0.94 [0.71-0.99]) slopes showed good to excellent and fair to excellent repeatability respectively (p<0.001 for both). For <i>between-day</i> trials, better repeatability was observed for %CVCi (ICC=0.85 [0.57-0.95]; p<0.001) compared to %MCAv_mean (ICC=0.76 [0.33-0.91]; p=0.004) slope. These findings indicate repeatable <i>within- and between-day</i> CVMR responses to rebreathe induced hypercapnia. However, a longer interval may be better for <i>within-day</i> repeat trials, particularly for CVCi measures.</p>","PeriodicalId":7630,"journal":{"name":"American journal of physiology. Regulatory, integrative and comparative physiology","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142455943","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Profiling growth performance, insulin-like growth factors (IGFs), and IGF-binding proteins (IGFBPs) in rainbow trout lacking IGFBP-2b.","authors":"Beth M Cleveland, Ayaka Izutsu, Yuika Ushizawa, Lisa Radler, Munetaka Shimizu","doi":"10.1152/ajpregu.00209.2024","DOIUrl":"https://doi.org/10.1152/ajpregu.00209.2024","url":null,"abstract":"<p><p>Insulin-like growth factor binding proteins (IGFBP) regulate insulin-like growth factor (IGF) signaling, but IGFBP-specific functions are not well characterized in fishes. A line of rainbow trout (<i>Oncorhynchus mykiss</i>) lacking a functional IGFBP-2b was produced using gene editing and subsequent breeding to an F2 generation. This loss-of-function model (2bKO) was subjected to either continuous feeding or feed deprivation (3 wk) followed by refeeding (1 wk). During continuous feeding, the 2bKO line displayed faster specific growth rate for both body weight and fork length, higher feed intake, and reduced feed conversion ratio compared to a wild type (WT) line. However, loss of IGFBP-2b did not affect the feed deprivation or refeeding response in terms of weight loss or weight gain, respectively. Several components of the IGF/IGFBP system were affected by loss of IGFBP2b. Total serum IGF-1 in the 2bKO line was reduced to 0.5 - 0.8-fold of the WT line although the concentration of free serum IGF-1 was not affected. Gene expression differences include reduced abundance of <i>igfbp1a1</i>, <i>igfbp1b2</i>, <i>igfbp5b2</i>, and <i>igfbp6b1</i> transcripts, and elevated <i>igf2</i> and <i>igfbp6b2</i> transcripts in liver of the 2bKO line. Collectively, these findings suggest that although IGFBP-2b is a carrier of circulating IGF-1 in salmonids, the presence of IGFBP-2a and compensatory responses of other IGF/IGFBP system components support an anabolic response that improved growth performance in the loss-of-function model.</p>","PeriodicalId":7630,"journal":{"name":"American journal of physiology. Regulatory, integrative and comparative physiology","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142455956","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Liraglutide ameliorates inflammation and fibrosis by downregulating the TLR4/MyD88/NF-κB pathway in diabetic kidney disease.","authors":"Linjing Huang, Tingting Lin, Meizhen Shi, Peiwen Wu","doi":"10.1152/ajpregu.00083.2024","DOIUrl":"10.1152/ajpregu.00083.2024","url":null,"abstract":"<p><p>Inflammation and fibrosis play important roles in diabetic kidney disease (DKD). Previous studies have shown that glucagon-like peptide-1 receptor (GLP-1R) agonists had renal protective effects. However, the mechanisms are not clear. The present study explored the effect of liraglutide (LR), a GLP-1R agonist, on the downregulation of glomerular inflammation and fibrosis in DKD by regulating the Toll-like receptor (TLR)4/myeloid differentiation marker 88 (MyD88)/nuclear factor κB (NF-κB) signaling pathway in mesangial cells (MCs). In vitro, rat MCs were cultured in high glucose (HG). We found that liraglutide treatment significantly reduced the HG-mediated activation of the TLR4/MYD88/NF-κB signaling pathway, extracellular matrix (ECM)-related proteins, and inflammatory factors. A combination of TLR4 inhibitor (TAK242) and liraglutide did not synergistically inhibit inflammatory factors and ECM proteins. Furthermore, in the presence of TLR4 siRNA, liraglutide significantly blunted HG-induced expression of fibronectin protein and inflammatory factors. Importantly, TLR4 selective agonist LPS or TLR4 overexpression eliminated the improvement effects of liraglutide on the HG-induced response. In vivo, administration of liraglutide for 8 wk significantly improved the glomerular damage in streptozotocin-induced diabetic mice and reduced the expression of TLR4/MYD88/NF-κB signaling proteins, ECM protein, and inflammatory factors in renal cortex. TLR4^-/- diabetic mice showed significant amelioration in urine protein excretion rate, glomerular pathological damage, inflammation, and fibrosis. Liraglutide attenuated glomerular hypertrophy, renal fibrosis, and inflammatory response in TLR4^-/- diabetic mice. Taken together, our findings suggest that TLR4/MYD88/NF-κB signaling is involved in the regulation of inflammatory response and ECM protein proliferation in DKD. Liraglutide alleviates inflammation and fibrosis by downregulating the TLR4/MYD88/NF-κB signaling pathway in MCs.<b>NEW & NOTEWORTHY</b> Liraglutide, a glucagon-like peptide-1 receptor agonist (GLP-1RA), has renoprotective effect in diabetic kidney disease (DKD). In DKD, TLR4/MYD88/NF-κB signaling is involved in the regulation of inflammatory responses and extracellular matrix (ECM) protein proliferation. Liraglutide attenuates renal inflammation and overexpression of ECM proteins by inhibiting TLR4/MYD88/NF-κB signaling pathway. Therefore, we have identified a new mechanism that contributes to the renal protection of GLP-1RA, thus helping to design innovative treatment strategies for diabetic patients with various complications.</p>","PeriodicalId":7630,"journal":{"name":"American journal of physiology. Regulatory, integrative and comparative physiology","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11483077/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141970425","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The independent effects of hydrostatic pressure and hypercapnic breathing during water immersion on ventilatory sensitivity and cerebrovascular reactivity.","authors":"James R Sackett, Zachary J Schlader, David Hostler, Blair D Johnson","doi":"10.1152/ajpregu.00008.2024","DOIUrl":"10.1152/ajpregu.00008.2024","url":null,"abstract":"<p><p>Head-out water immersion (HOWI) induces ventilatory and hemodynamic changes, which may be a result of hydrostatic pressure, augmented arterial CO₂ tension, or a combination of both. We hypothesized that the hydrostatic pressure and elevated CO₂ tension that occur during HOWI will contribute to an augmented ventilatory sensitivity to CO₂ and an attenuated cerebrovascular reactivity to CO₂ during water immersion. Twelve subjects [age: 24 ± 3 yr, body mass index (BMI): 25 ± 3 kg/m²] completed HOWI, waist water immersion with CO₂ (WWI + CO₂), and WWI, where a rebreathing test was conducted at baseline, 10, 30, and 60 min, and postimmersion. End-tidal pressure of carbon dioxide ([Formula: see text]), minute ventilation, expired gases, blood pressure, heart rate, and middle cerebral artery blood velocity were recorded continuously. [Formula: see text] increased throughout all visits (<i>P</i> ≤ 0.011), was similar during HOWI and WWI + CO₂ (<i>P</i> ≥ 0.264), and was greater during WWI + CO₂ versus WWI at 10, 30, and 60 min (<i>P</i> < 0.001). When HOWI vs. WWI + CO₂ were compared, the change in ventilatory sensitivity to CO₂ was different at 10 (0.59 ± 0.34 vs. 0.06 ± 0.23 L/min/mmHg; <i>P</i> < 0.001), 30 (0.58 ± 0.46 vs. 0.15 ± 0.25 L/min/mmHg; <i>P</i> < 0.001), and 60 min (0.63 ± 0.45 vs. 0.16 ± 0.34 L/min/mmHg; <i>P</i> < 0.001), whereas there were no differences between conditions for cerebrovascular reactivity to CO₂ (<i>P</i> ≥ 0.163). When WWI + CO₂ versus WWI were compared, ventilatory sensitivity to CO₂ was not different between conditions (<i>P</i> ≥ 0.642), whereas the change in cerebrovascular reactivity to CO₂ was different at 30 min (-0.56 ± 0.38 vs. -0.30 ± 0.25 cm/s/mmHg; <i>P</i> = 0.010). These data indicate that during HOWI, ventilatory sensitivity to CO₂ increases due to the hydrostatic pressure, whereas cerebrovascular reactivity to CO₂ decreases due to the combined effects of immersion.<b>NEW & NOTEWORTHY</b> Although not fully elucidated, the ventilatory and hemodynamic alterations during water immersion appear to be a result of the combined effects of immersion (i.e., elevated [Formula: see text], central hypervolemia, increased cerebral perfusion, increased work of breathing, etc.). Our findings demonstrate that an augmented ventilatory sensitivity to CO₂ during immersion may be due to the hydrostatic pressure across the chest wall, whereas an attenuated cerebrovascular reactivity to CO₂ may be due to the combined effects of immersion.</p>","PeriodicalId":7630,"journal":{"name":"American journal of physiology. Regulatory, integrative and comparative physiology","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11483083/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141970427","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Activation of skeletal muscle mechanoreceptors and nociceptors reduces the exercise performance of the contralateral homologous muscles.","authors":"Fabio Zambolin, Fabio Giuseppe Laginestra, Thomas Favaretto, Gaia Giuriato, Matteo Maria Ottaviani, Federico Schena, Pablo Duro-Ocana, Jamie Stewart McPhee, Massimo Venturelli","doi":"10.1152/ajpregu.00069.2024","DOIUrl":"10.1152/ajpregu.00069.2024","url":null,"abstract":"<p><p>Increasing evidence suggests that activation of muscle nerve afferents may inhibit central motor drive, affecting contractile performance of remote exercising muscles. Although these effects are well documented for metaboreceptors, very little is known about the activation of mechano- and mechanonociceptive afferents on performance fatigability. Therefore, the purpose of the present study was to examine the influence of mechanoreceptors and nociceptors on performance fatigability. Eight healthy young males undertook four randomized experimental sessions on separate occasions in which the experimental knee extensors were the following: <i>1</i>) resting (CTRL), <i>2</i>) passively stretched (ST), <i>3</i>) resting with delayed onset muscle soreness (DOMS), or <i>4</i>) passively stretched with DOMS (DOMS+ST), whereas the contralateral leg performed an isometric time to task failure (TTF). Changes in maximal voluntary contraction (ΔMVC), potentiated twitch force (ΔQ_tw,pot), and voluntary muscle activation (ΔVA) were also assessed. TTF was reduced in DOMS+ST (-43%) and ST (-29%) compared with CTRL. DOMS+ST also showed a greater reduction of VA (-25% vs. -8%, respectively) and MVC compared with CTRL (-28% vs. -45%, respectively). Rate of perceived exertion (RPE) was significantly increased at the initial stages (20-40-60%) of the TTF in DOMS+ST compared with all conditions. These findings indicate that activation of mechanosensitive and mechanonociceptive afferents of a muscle with DOMS reduces TTF of the contralateral homologous exercising limb, in part, by reducing VA, thereby accelerating mechanisms of central fatigue.<b>NEW & NOTEWORTHY</b> We found that activation of mechanosensitive and nociceptive nerve afferents of a rested muscle group experiencing delayed onset muscle soreness was associated with reduced exercise performance of the homologous exercising muscles of the contralateral limb. This occurred with lower muscle voluntary activation of the exercising muscle at the point of task failure.</p>","PeriodicalId":7630,"journal":{"name":"American journal of physiology. Regulatory, integrative and comparative physiology","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11483073/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141892630","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cardiovascular and hematological responses to a dry dynamic apnea in breath hold divers.","authors":"Courtney V Brown, Alexander Patrician, Joshua C Tremblay, L Madden Brewster, Otto Barak, Ivan Drvis, Goran Dujic, Zeljko Dujic, Philip N Ainslie","doi":"10.1152/ajpregu.00081.2024","DOIUrl":"10.1152/ajpregu.00081.2024","url":null,"abstract":"<p><p>The mammalian dive reflex, characterized by bradycardia and peripheral vasoconstriction, occurs in all mammals, including humans, in response to apnea. However, the dive reflex to a single, maximal, dry, dynamic apnea (DYN) and how it compares to a time-matched exercise control trial (EX) or dry static apnea (SA) has not been studied. We examined the hypotheses that, compared with EX and SA, the magnitude of the <i>1</i>) cardiovascular response and <i>2</i>) hematological response to DYN would be greater. Cardiovascular parameters [heart rate (HR), systolic (SBP), diastolic (DBP), and mean arterial (MAP) blood pressure] were continuously collected in 23 (<i>F</i> = 6 females) moderate and elite freedivers, first during a maximal DYN, then during a time-matched SA and EX on a swimming ergometer in randomized order. Venous blood draws were made before and following each trial. The change in calculated oxygen saturation (DYN: -17 ± 13%, EX: -2 ± 1%, ΔSA: -2 ± 1%; <i>P</i> < 0.05, all comparisons) was greater during DYN compared with EX and SA. During DYN, ΔSBP (DYN: 104 ± 31 mmHg; EX: 38 ± 23 mmHg; and SA: 20 ± 11 mmHg), ΔDBP (DYN: 45 ± 12 mmHg; EX: 14 ± 10 mmHg; and SA: 15 ± 8 mmHg), and ΔMAP (DYN: 65 ± 17 mmHg; EX: 22 ± 13 mmHg; and SA: 16 ± 9 mmHg) were increased compared with EX and SA, while ΔHR was greater during EX (DYN: -24 ± 23 beats/min; EX: 33 ± 13 beats/min; and SA: -1 ± 10 beats/min) than either DYN or SA (<i>P</i> < 0.0001, all comparisons). Females had a greater pressor response to EX (ΔSBP: 59 ± 30 mmHg; ΔDBP: 24 ± 14 mmHg; and ΔMAP: 35 ± 8 mmHg) than males (ΔSBP: 31 ± 15 mmHg; ΔDBP: 11 ± 6 mmHg; and ΔMAP: 18 ± 8 mmHg; <i>P</i> < 0.01, all comparisons). Together, these data indicate that DYN elicits a distinct, exaggerated cardiovascular response compared with EX or SA alone.<b>NEW & NOTEWORTHY</b> This study performed a dry dynamic apnea with sport-specific equipment to closely mimic the physiological demands of competition diving. We found the cardiovascular and hematological responses to dynamic apnea were more robust compared with time-matched exercise and dry static apnea control trials.</p>","PeriodicalId":7630,"journal":{"name":"American journal of physiology. Regulatory, integrative and comparative physiology","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141892631","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}