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

{"title":"Early-life sodium restriction programs autonomic dysfunction and salt sensitivity in male C57BL/6J mice.","authors":"Alisha A Ziegler, Samuel B R Lawton, Eva M Fekete, Daniel T Brozoski, Valerie A Wagner, Connie C Grobe, Curt D Sigmund, Pablo Nakagawa, Justin L Grobe, Jeffrey L Segar","doi":"10.1152/ajpregu.00250.2024","DOIUrl":"10.1152/ajpregu.00250.2024","url":null,"abstract":"<p><p>Preterm birth increases the risk of cardiometabolic disease in adulthood. Infants born during the second trimester of pregnancy, a critical period of hypothalamic development, are at risk of sodium (Na) depletion due to renal immaturity and large urine Na losses. We previously demonstrated in male mice that Na restriction during the equivalent mouse hypothalamic development period [postnatal day (PD)21-PD42] programs long-term changes in energy balance via increased thermogenic sympathetic nervous activity. We therefore hypothesized that early-life Na restriction programs changes in cardiovascular control via altered autonomic activity. C57BL/6J male mice were supplied a low (0.04%) Na or supplemented (0.30%) Na diet from PD21 to PD42, before return to standard (0.15%) Na diet. Hemodynamic and autonomic functions were assessed by radiotelemetry and acute administration of autonomic antagonists before and after all animals were switched to a high Na diet (HSD; 1% Na) at 12 wk of age. Mice were additionally treated with the angiotensin II type 1 receptor antagonist losartan for 2 wk. On standard diet, early-life Na restriction resulted in small but significantly different hemodynamic responses to autonomic blockers without any effect on systolic blood pressure (SBP) or heart rate. HSD increased SBP in 0.04% but not 0.30% Na mice, accompanied by increased cardiac sympathetic activity. Losartan had a greater BP-lowering effect in early-life Na-restricted mice. Our findings suggest that Na restriction during a critical hypothalamic developmental period programs long-term changes in the autonomic control of cardiovascular functions and may offer insight into the increased risk of cardiovascular disease in former preterm infants.<b>NEW & NOTEWORTHY</b> Mechanisms by which preterm birth increases the risk of adult-onset cardiometabolic diseases are not well understood. The renin-angiotensin system (RAS) has been implicated in the programming of adult disease, although contributors to RAS dysregulation remain to be identified. Findings from this study suggest that failure to maintain postnatal sodium homeostasis during a critical developmental window may contribute to RAS dysregulation and the risk of salt sensitivity of autonomic and cardiovascular function.</p>","PeriodicalId":7630,"journal":{"name":"American journal of physiology. Regulatory, integrative and comparative physiology","volume":" ","pages":"R109-R120"},"PeriodicalIF":2.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142643242","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 index of maximum sweat ion reabsorption rates of sweat glands does not correlate to whole body sweat sodium concentration in exercising young healthy men.","authors":"Shoma Oshima, Yumi Okamoto, Junto Otsuka, Shotaro Yokoyama, Yuki Hashimoto, Takako Ishihara, Hiroyoshi Togo, Tatsuro Amano","doi":"10.1152/ajpregu.00149.2024","DOIUrl":"10.1152/ajpregu.00149.2024","url":null,"abstract":"<p><p>Factors explaining individual variations in whole body sweat sodium ion concentration ([Na⁺]) during exercise are not fully understood. Galvanic skin conductance (GSC) reflects the electrical properties of the skin influenced by sweat rate (SR) and the presence of ions. Initiation of increases in this response to elevating sweating may reflect exceeding the maximal capacity of sweat ion reabsorption in sweat glands. We investigated whether the SR threshold for increasing GSC, an indirect measure of maximum ion reabsorption rates of sweat glands, explains the variations in whole body sweat [Na⁺]. Thirty young healthy males cycled for 90 min at incremental exercise intensities of 30, 45, and 60% peak oxygen uptake (30 min each) in the heat (32°C, 50% relative humidity). Whole body sweat [Na⁺] was measured using a whole body washdown technique. The SR threshold for increasing GSC was determined from the relationship between the local SR (ventilated capsule) and GSC on the forearm and chest. The average whole body sweat [Na⁺] was 42.8 ± 18.9 (range: 14.4-81.0) mmol L^-1, and the SR threshold for increasing GSC was 0.29 ± 0.20 (range: 0.02-0.62) and 0.35 ± 0.30 (range: 0.01-1.40) mg cm^-2 min^-1 for the forearm and chest, respectively. Whole body sweat [Na⁺] was not correlated with the SR threshold for increasing GSC in the forearm or chest (<i>r</i>² ≤ 0.001, <i>P</i> ≥ 0.921). We conclude that the SR threshold for increasing GSC at the forearm and chest does not explain the individual variation in whole body sweat [Na⁺] during exercise in the heat.<b>NEW & NOTEWORTHY</b> Galvanic skin conductance is influenced by sweat rate and sweat ions, and the sweat rate at which this response begins to increase may reflect the exceeding capacity of sweat ion reabsorption in sweat glands. However, we show that this indirect measure of the sweat gland's capacity of ion regulation on the forearm and chest does not correlate with whole body sweat sodium concentration during exercise, excluding its role as a determinant of systemic sweat sodium loss.</p>","PeriodicalId":7630,"journal":{"name":"American journal of physiology. Regulatory, integrative and comparative physiology","volume":" ","pages":"R102-R108"},"PeriodicalIF":2.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142724823","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":"CCK-expressing neurons in the NTS are directly activated by CCK-sensitive C-type vagal afferents.","authors":"Eric T Winzenried, Drew M Neyens, Rowan Calkins, Suzanne M Appleyard","doi":"10.1152/ajpregu.00280.2023","DOIUrl":"10.1152/ajpregu.00280.2023","url":null,"abstract":"<p><p>Vagal sensory afferents carrying information from the gastrointestinal tract (GI) terminate in the nucleus of the solitary tract (NTS). Different subpopulations of NTS neurons then relay this information throughout the brain. Cholecystokinin (CCK) is a satiety peptide that activates vagal afferents in the GI. However, CCK is also expressed by neurons in the NTS, and activation of these neurons decreases food intake. What is less clear is how these NTS CCK neurons are activated by vagal afferents and what type of information they integrate about meal size and content. To address this, we identified NTS-CCK neurons by crossing CCK-IRES-Cre mice with floxed-Rosa-tdtomato mice and made a horizontal brain slice containing vagal afferents in the solitary tract (ST). Voltage clamp recordings of NTS-CCK neurons show that activation of the ST evokes excitatory postsynaptic currents (EPSCs) mediated by both α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and <i>N</i>-methyl-d-aspartate (NMDA) receptors. Analysis of these EPSCs revealed that 80% of NTS-CCK neurons receive direct, monosynaptic inputs, with many also receiving indirect, or polysynaptic, inputs. NTS-CCK neurons are sensitive to the transient receptor potential vanilloid type 1 agonist capsaicin, suggesting that they are downstream of C-fibers. In addition, both CCK and a 5 hydroxytryptamine 3 receptor (5-HT3R) agonist increased spontaneous EPSC (sEPSC) frequency in NTS-CCK neurons, with 69% of NTS-CCK neurons sensitive to CCK and 42% to the 5-HT3 receptor agonist, as well as 45% sensitive to both and 10% to neither. Taken together with previous studies, this suggests that NTS-CCK neurons are driven primarily by vagal afferents that are sensitive to CCK and are only weakly driven by those sensitive to serotonin.<b>NEW & NOTEWORTHY</b> Nucleus of the solitary tract (NTS) cholecystokinin (CCK) expressing neurons are directly activated by glutamate released from vagal afferents. They are downstream of primarily C-type CCK-sensitive afferents, with a small proportion also downstream of serotonin-sensitive afferents. These findings suggest that NTS-CCK neurons integrate signals from the gut about ingestion of fats and proteins as well as stretch of the stomach, which they then relay to other brain regions important for the control of food intake.</p>","PeriodicalId":7630,"journal":{"name":"American journal of physiology. Regulatory, integrative and comparative physiology","volume":" ","pages":"R121-R132"},"PeriodicalIF":2.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142602715","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":"Adrenal epinephrine facilitates erythropoietin gene activation by hypoxia through β2 adrenergic receptor interaction with Hif-2α.","authors":"Xiaoyu Su, Matthew Hildreth, Srikar Rapaka, Ying-Jie Peng, Jayasri Nanduri, Nanduri R Prabhakar","doi":"10.1152/ajpregu.00201.2024","DOIUrl":"10.1152/ajpregu.00201.2024","url":null,"abstract":"<p><p>Hypobaric hypoxia (HH) occurring at high altitudes activates the sympathetic nervous system (SNS) and increases circulating erythropoietin (EPO) levels. EPO stimulates red blood cell production (erythropoiesis), enhancing oxygen transport in arterial blood to counteract hypoxemia. The present study tested the hypothesis that SNS contributes to EPO activation by HH through epinephrine (EPI) release from the adrenal medullae. Adult male C57B6 mice were exposed to 18 h of HH (0.4 atm), and renal <i>EPO</i> mRNA and plasma EPO levels were measured. HH increased <i>EPO</i> mRNA and plasma EPO levels, and SNS activation, as indicated by elevated plasma norepinephrine (NE) and EPI levels. In adrenal-medullectomized mice, HH-induced EPO response was reduced, correlating with decreased circulating NE and absence of EPI elevation. EPI, but not NE infusion, mimicked the effects of HH in room air-breathing mice. EPO responses to HH were reduced with β-adrenergic receptor (AR) blockade using dl-propranolol and in β2 adrenergic receptor knockout mice. Mice with heterozygous Hif-2α deficiency (<i>Hif-2α</i>^+/-), but not <i>Hif-1α</i>^+/-, showed attenuated <i>EPO</i> gene activation and elevated plasma EPO levels in response to HH and EPI infusion. These results demonstrate that adrenal EPI facilitates the <i>EPO</i> gene activation by HH through the interaction of β2 AR with HIF-2α.<b>NEW & NOTEWORTHY</b> Hypobaric hypoxia activates the sympathetic nervous system (SNS) and the erythropoietin (<i>EPO</i>) gene. Whether SNS activation by hypoxia influences the <i>EPO</i> gene activation is an unresolved question. The present study demonstrates that adrenal epinephrine facilitates hypoxia-induced <i>EPO</i> gene activation through the interaction of β2 adrenergic receptors (β2 ARs) with the transcriptional activator HIF-2α.</p>","PeriodicalId":7630,"journal":{"name":"American journal of physiology. Regulatory, integrative and comparative physiology","volume":" ","pages":"R75-R80"},"PeriodicalIF":2.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142715017","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 effect of high-intensity exercise in temperate and hot ambient conditions on autophagy and the cellular stress response in young and older females.","authors":"James J McCormick, Nicholas Goulet, Kelli E King, Naoto Fujii, Tatsuro Amano, Glen P Kenny","doi":"10.1152/ajpregu.00178.2024","DOIUrl":"10.1152/ajpregu.00178.2024","url":null,"abstract":"<p><p>The process of autophagy is vital in maintaining normal cellular function, especially during exposure to elevated states of physiological stress associated with exercise and hot ambient temperatures. Although prior observations are primarily limited to responses in males, the autophagic response to acute physiological stress in females represents a considerable knowledge gap. Therefore, we assessed autophagy and related pathways of cellular stress in peripheral blood mononuclear cells (PBMCs) from 20 healthy young [<i>n</i> = 10, mean (SD): aged 23 yr (3)] and older [<i>n</i> = 10, aged 69 yr (3)] females in response to 30 min of semi-recumbent high-intensity cycling exercise (70% of predetermined maximal oxygen consumption) in temperate (25°C) and hot (40°C) ambient conditions (15% relative humidity). Mean body temperature (rectal and skin) was measured throughout, whereas cellular responses were evaluated before and after exercise, including up to 6 h of seated recovery. Proteins associated with autophagy and related pathways were assessed via Western blot. Mean body temperature was elevated after exercise in both conditions, with significant elevations observed after exercise in the heat (all, <i>P</i> ≤ 0.05). Although young females displayed signs of elevated autophagic activity [elevations in microtubule-associated light chain 3B (LC3)-II and beclin-2] in response to exercise performed in both temperate and hot ambient conditions (all, <i>P</i> ≤ 0.05), responses were attenuated in older females. This was accompanied by elevations in chaperone-mediated autophagy in young but not in older females in response to exercise independent of ambient temperature. Our findings indicate exercise, with and without ambient heat exposure may stimulate the autophagic response in young but not in older females.<b>NEW & NOTEWORTHY</b> We show for the first time that an acute bout (30 min) of high-intensity intensity exercise stimulates autophagy in young females irrespective of ambient heat exposure. However, older females did not display the same increase in autophagy as their younger counterparts when high-intensity exercise was performed in temperate or hot ambient conditions. Consequently, older females may be at an elevated risk of heat-induced cellular damage during exertional heat stress.</p>","PeriodicalId":7630,"journal":{"name":"American journal of physiology. Regulatory, integrative and comparative physiology","volume":" ","pages":"R90-R101"},"PeriodicalIF":2.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142724810","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, and IGF-binding proteins 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":"10.1152/ajpregu.00209.2024","url":null,"abstract":"<p><p>Insulin-like growth factor-binding proteins (IGFBPs) 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 [IGFBP-2b knockout (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 with 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 IGFBP-2b. Total serum IGF-1 in the 2bKO line was reduced to 0.5- to 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.<b>NEW & NOTEWORTHY</b> Knocking out IGFBP-2b in rainbow trout improved food intake, growth performance, and feed conversion ratio and reduced serum IGF-1 by 0.5- to 0.8-fold, without changes in the concentration of free serum IGF-1. Based on these findings, we propose that, in addition to IGFBP-2b, the 32-kDa IGFBP (putative IGFBP-2a) also serves as a major carrier of circulating IGF-1 in salmonids.</p>","PeriodicalId":7630,"journal":{"name":"American journal of physiology. Regulatory, integrative and comparative physiology","volume":" ","pages":"R34-R44"},"PeriodicalIF":2.2,"publicationDate":"2025-01-01","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":"Cardiovascular function and autonomic regulation in urethane-anesthetized and conscious mice.","authors":"Anastasiia Vasileva, Laura D M Flores, Mikhail Vasilyev, Michelle A Buckman, Lara R DeRuisseau, Michael H Tomasson, Melissa L Bates","doi":"10.1152/ajpregu.00097.2024","DOIUrl":"10.1152/ajpregu.00097.2024","url":null,"abstract":"<p><p>Urethane is widely used for its ability to induce prolonged anesthesia. Variability in previously reported cardiovascular parameters in murine models makes it challenging to definitively evaluate the cardiovascular effects of urethane anesthesia. We aimed to address these challenges, thereby advancing our understanding of urethane's effects on cardiovascular function in mice. In this study, we investigated how urethane anesthesia, with and without supplemental oxygen, impacts heart rate, arterial oxygen saturation ([Formula: see text]), blood pressure, and heart rate variability in mice. First, we conducted a literature review and found that data in mice were both limited and lacking in reproduction. Next, we conducted a series of physiological measurements to address gaps in the literature and subjected C57BL/6J mice to three conditions: <i>1</i>) conscious, <i>2</i>) urethane-anesthetized, and <i>3</i>) urethane-anesthetized with supplemental oxygen. Blood pressure, heart rate, [Formula: see text], and heart rate variability (via time, frequency, and M-curve analyses) were assessed. We observed an increase in heart rate with urethane anesthesia (<i>P</i> = 0.012) compared with the conscious state. Urethane caused a decrease in heart rate variability, which was independent of oxygen supplementation. Urethane anesthesia caused a significant reduction in arterial blood pressure (<i>P</i> < 0.001) with oxygen-supplemented mice remained hypotensive. Urethane decreased [Formula: see text] (<i>P</i> = 0.001), which was restored by oxygen supplementation (<i>P</i> < 0.001). We did not observe sex effects of urethane anesthesia on blood pressure, heart rate, heart rate variability, or [Formula: see text]. Taken together, these results underscore the importance of a cautious approach when using urethane in mice, as urethane significantly impacts arterial blood pressure, heart rate, oxygen saturation, and heart rate variability.<b>NEW & NOTEWORTHY</b> This investigation documents cardiovascular outcomes in mice receiving urethane anesthesia, emphasizing sex as a biological variable, and considering oxygen supplementation during anesthesia. This is the first report of M-curve analysis in rodents as a heart rate-independent variability analysis.</p>","PeriodicalId":7630,"journal":{"name":"American journal of physiology. Regulatory, integrative and comparative physiology","volume":" ","pages":"R133-R144"},"PeriodicalIF":2.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142783941","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":"Relationship between regional sympathetic vascular transduction and sympathetic transduction of blood pressure in young adults at rest.","authors":"Devin G McCarthy, Massimo Nardone, Kathryn Pfundt, Philip J Millar","doi":"10.1152/ajpregu.00199.2024","DOIUrl":"10.1152/ajpregu.00199.2024","url":null,"abstract":"<p><p>A burst of muscle sympathetic nerve activity (MSNA) induces vasoconstriction that transiently reduces regional vascular conductance and increases systemic blood pressure (BP) over the subsequent 4-8 cardiac cycles. These responses are termed sympathetic neurovascular transduction and sympathetic transduction of BP, respectively. Sympathetic transduction of BP is commonly calculated and interpreted as a proxy measure for regional sympathetic neurovascular transduction despite the systemic nature of BP regulation. The present analysis tested whether the peak change in signal-averaged sympathetic transduction of BP was correlated to the change in regional sympathetic vascular transduction at rest. Fourteen adults (5 females, 23 ± 3 yr) arrived at the laboratory, ate a standardized meal, and rested for 90-120 min. MSNA (fibular nerve microneurography), heart rate (electrocardiography), beat-to-beat BP (finger photoplethysmography), and superficial femoral artery blood flow (Doppler ultrasound) were obtained continuously for 10 min in the supine position. Femoral vascular conductance (FVC) was calculated as blood flow divided by mean arterial BP. The peak change in diastolic BP following a burst of MSNA was correlated to the corresponding nadir change in femoral vascular conductance (<i>r</i> = -0.58 [-0.07 to -0.85], <i>P</i> = 0.03) and superficial femoral artery blood flow (<i>r</i> = -0.54 [-0.17 to -0.83], <i>P</i> = 0.04). The nadir change in diastolic BP in cardiac cycles not following an MSNA burst was correlated to the peak change in femoral vascular conductance (<i>r</i> = -0.42 [-0.83 to 0.00], <i>P</i> = 0.05), but not superficial femoral artery blood flow (<i>r</i> = 0.41 [-0.77 to 0.15], <i>P</i> = 0.14). In conclusion, more commonly assessed sympathetic transduction of BP provides moderate insight into regional sympathetic neurovascular transduction.<b>NEW & NOTEWORTHY</b> The majority of studies have used signal-averaged sympathetic transduction of blood pressure as a generalized measure of transduction. In this analysis, we show that sympathetic transduction of blood pressure and regional sympathetic vascular transduction were moderately correlated in healthy adults at rest. The moderate strength of this relationship highlights potential differences between regional and systemic assessments of sympathetic transduction and suggests that future work should choose the transduction measure best aligned with the research question.</p>","PeriodicalId":7630,"journal":{"name":"American journal of physiology. Regulatory, integrative and comparative physiology","volume":" ","pages":"R528-R533"},"PeriodicalIF":2.2,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142387293","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":"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 min between trials), ten performed <i>a within-day long interval</i> protocol (145 ± 16 min 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 ([Formula: see text]) 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]; <i>P</i> < 0.001) while %CVCi slope showed more variability (ICC = 0.84 [0.47-0.95]; <i>P</i> = 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 (<i>P</i> < 0.001 for both). For <i>between-day</i> trials, better repeatability was observed for %CVCi (ICC = 0.85 [0.57-0.95]; <i>P</i> < 0.001) compared with %MCAv_mean (ICC = 0.76 [0.33-0.91]; <i>P</i> = 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.<b>NEW & NOTEWORTHY</b> The cerebral vasodilator response to increases in arterial carbon dioxide concentration, termed cerebral vasomotor reactivity, provides an index of cerebral vascular function/health. Reduced responses are present in populations with elevated cerebral vascular and neurocognitive disease risk/overt disease. Cerebral vasomotor reactivity is often assessed during rebreathing-induced hypercapnia. This study determined that the day-to-day and between-day variability in this response is repeatable, thereby providing important methodological information to the scientific community.</p>","PeriodicalId":7630,"journal":{"name":"American journal of physiology. Regulatory, integrative and comparative physiology","volume":" ","pages":"R580-R589"},"PeriodicalIF":2.2,"publicationDate":"2024-12-01","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":"Cerebral hemodynamic and systemic physiological changes in trained freedivers completing sled-assisted dives to two different depths.","authors":"Eva-Maria S Bønnelycke, Tommaso A Giacon, Gerardo Bosco, Jana M Kainerstorfer, Matteo Paganini, Alexander Ruesch, Jingyi Wu, J Chris McKnight","doi":"10.1152/ajpregu.00085.2024","DOIUrl":"10.1152/ajpregu.00085.2024","url":null,"abstract":"<p><p>Although existing literature covers significant detail on the physiology of human freediving, the lack of standardized protocols has hindered comparisons due to confounding variables such as exercise and depth. By accounting for these variables, direct depth-dependent impacts on cardiovascular and blood oxygen regulation can be investigated. In this study, depth-dependent effects on <i>1</i>) cerebral hemodynamic and oxygenation changes, <i>2</i>) arterial oxygen saturation ([Formula: see text]), and <i>3</i>) heart rate during breath-hold diving without confounding effects of exercise were investigated. Six freedivers (51.0 ± 12.6 yr; means ± SD), instrumented with continuous-wave near-infrared spectroscopy for monitoring cerebral hemodynamic and oxygenation measurements, heart rate, and [Formula: see text], performed sled-assisted breath-hold dives to 15 m and 42 m. Arterial blood gas tensions were validated through cross-sectional periodic blood sampling. Cerebral hemodynamic changes were characteristic of breath-hold diving, with changes during ascent from both depths likely driven by decreasing [Formula: see text] due to lung expansion. Although [Formula: see text] was significantly lower following 42-m dives [<i>t</i>(5) = -4.183, <i>P</i> < 0.05], mean cerebral arterial-venous blood oxygen saturation remained at 74% following dives to both depths. Cerebral oxygenation during ascent from 42 m may have been maintained through increased arterial delivery. Heart rate was variable with no significant difference in minimum heart rate between both depths [<i>t</i>(5) = -1.017, <i>P</i> > 0.05]. This study presents a standardized methodology, which could provide a basis for future research on human freediving physiology and uncover ways in which freedivers can reduce potential risks of the sport.<b>NEW & NOTEWORTHY</b> We present a standardized methodology in which trained breath-hold divers instrumented with wearable near-infrared spectroscopy (NIRS) technology and a cannula for arterial blood sampling completed sled-assisted dives to two different dive depths to account for the confounding factors of exercise and depth during breath-hold diving. In our investigation, we highlight the utility of wearable NIRS systems for continuous hemodynamic and oxygenation monitoring to investigate the impacts of hydrostatic pressure on cardiovascular and blood oxygen regulation.</p>","PeriodicalId":7630,"journal":{"name":"American journal of physiology. Regulatory, integrative and comparative physiology","volume":" ","pages":"R553-R567"},"PeriodicalIF":2.2,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11687848/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142143011","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}