Experimental Physiology最新文献

{"title":"High-intensity interval training improves cardiomyocyte contractile function and myofilament sensitivity to intracellular Ca2+ in obese rats","authors":"Matheus Corteletti dos Santos,&nbsp;Daniel Sesana da Silva,&nbsp;Jóctan Pimentel Cordeiro,&nbsp;Lucas Furtado Domingos,&nbsp;Ezio Henrique da Silva Gomes,&nbsp;Breno Valentim Nogueira,&nbsp;Danilo Sales Bocalini,&nbsp;Ana Paula Lima Leopoldo,&nbsp;André Soares Leopoldo","doi":"10.1113/EP092015","DOIUrl":"10.1113/EP092015","url":null,"abstract":"<p>High-intensity interval training (HIIT) has shown significant results in addressing adiposity and risk factors associated with obesity. However, there are no studies that investigate the effects of HIIT on contractility and intracellular Ca²⁺ handling. The purpose of this study was to explore the impact of HIIT on cardiomyocyte contractile function and intracellular Ca²⁺ handling in rats in which obesity was induced by a saturated high-fat diet (HFD). Male Wistar rats were initially randomized into a standard diet and a HFD group. The experimental protocol spanned 23 weeks, comprising the induction and maintenance of obesity (15 weeks) followed by HIIT treatment (8 weeks). Performance was assessed using the maximum oxygen consumption test (<span></span><math>\u0000 <semantics>\u0000 <msub>\u0000 <mover>\u0000 <mi>V</mi>\u0000 <mo>̇</mo>\u0000 </mover>\u0000 <mrow>\u0000 <msub>\u0000 <mi>O</mi>\u0000 <mn>2</mn>\u0000 </msub>\u0000 <mi>max</mi>\u0000 </mrow>\u0000 </msub>\u0000 <annotation>${{dot{V}}_{{{{mathrm{O}}}_{mathrm{2}}}{mathrm{max}}}}$</annotation>\u0000 </semantics></math>). Evaluation encompassed cardiac, adipose and skeletal muscle histology, as well as contractility and intracellular Ca²⁺ handling. HIIT resulted in a reduction in visceral area, an increase in <span></span><math>\u0000 <semantics>\u0000 <msub>\u0000 <mover>\u0000 <mi>V</mi>\u0000 <mo>̇</mo>\u0000 </mover>\u0000 <mrow>\u0000 <msub>\u0000 <mi>O</mi>\u0000 <mn>2</mn>\u0000 </msub>\u0000 <mi>max</mi>\u0000 </mrow>\u0000 </msub>\u0000 <annotation>${{dot{V}}_{{{{mathrm{O}}}_{mathrm{2}}}{mathrm{max}}}}$</annotation>\u0000 </semantics></math>, and an augmentation of gastrocnemius fibre diameter in obese subjects. Additionally, HIIT led to a decrease in collagen fraction, an increase in percentage shortening, and a reduction in systolic Ca²⁺/percentage shortening and systolic Ca²⁺/maximum shortening rates. HIIT induces physiological cardiac remodelling, enhancing the contractile function of cardiomyocytes and improving myofilament sensitivity to Ca²⁺ in the context of obesity. This approach not only enhances cardiorespiratory and physical performance but also reduces visceral area and prevents interstitial fibrosis.</p>","PeriodicalId":12092,"journal":{"name":"Experimental Physiology","volume":"109 10","pages":"1710-1727"},"PeriodicalIF":2.6,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11442780/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142105828","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"High-intensity resistance training and collagen supplementation improve patellar tendon adaptations in professional female soccer athletes.","authors":"Joonsung Lee, David C Robshaw, Robert M Erskine","doi":"10.1113/EP092106","DOIUrl":"https://doi.org/10.1113/EP092106","url":null,"abstract":"<p><p>We investigated whether 10 weeks of pre-season soccer training (including high-intensity resistance exercise) with hydrolysed collagen (COL) supplementation would confer greater changes in patellar tendon (PT) mechanical and material properties compared with placebo (PLA) in professional female soccer athletes. Eleven athletes from the first team squad of a Football Association Women's Championship soccer club volunteered to participate in this study (age, 25.7 ± 4.2 years; height, 1.68 ± 0.04 m; mass, 64.0 ± 4.6 kg). Participants were pair-matched for baseline knee extensor maximum isometric voluntary contraction torque, age, height and mass and were randomly assigned to the COL group (n = 6) or PLA group (n = 5). Participants were given 30 g COL or energy-matched (36.5 g maltodextrin and 8.4 g fructose) PLA, plus 500 mg vitamin C before each training session, which consisted of high-intensity lower-limb resistance exercise, plyometric or pitch-based exercise 3 days/week for 10 weeks during the pre-season period. We assessed knee extensor maximum isometric voluntary contraction torque and PT properties using isokinetic dynamometry and ultrasonography before and after the intervention. The PT stiffness [COL, +15.4% ± 3.1% (d = 0.81) vs. PLA, +4.6% ± 3.0% (d = 0.32), P = 0.002] and Young's modulus [COL, +14.2% ± 4.0% (d = 0.65) vs. PLA, +3.4% ± 2.8% (d = 0.15), P = 0.004] increased more in COL than in PLA. There was a main effect of training on PT cross-sectional area (P = 0.027), but no interaction effect (P = 0.934). To conclude, 10 weeks of pre-season soccer training (incorporating high-intensity resistance exercise) with 30 g COL increased PT stiffness and Young's modulus more than training alone in professional female soccer athletes. This has positive implications for improving athletic performance and mitigating injury risk.</p>","PeriodicalId":12092,"journal":{"name":"Experimental Physiology","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142105829","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Short-latency afferent inhibition is reduced with cold-water immersion of a limb and remains reduced after removal from the cold stimulus","authors":"Eden T. Delahunty,&nbsp;Leanne M. Bisset,&nbsp;Justin J. Kavanagh","doi":"10.1113/EP091896","DOIUrl":"10.1113/EP091896","url":null,"abstract":"&lt;div&gt;\u0000 \u0000 &lt;section&gt;\u0000 \u0000 \u0000 &lt;p&gt;The experience of pain that is induced by extremely cold temperatures can exert a modulatory effect on motor cortex circuitry. Although it is known that immersion of a single limb in very cold water can increase corticomotor excitability it is unknown how afferent input to the cortex shapes excitatory and inhibitory processes. Therefore, the purpose of this study was to examine motor-evoked potentials (MEP), short-latency afferent inhibition (SAI) and long-latency afferent inhibition (LAI) in response to immersion of a single hand in cold water. Transcranial magnetic stimulation (TMS) was used to assess MEPs, and peripheral nerve stimulation of the median nerve paired with TMS was used to measure SAI and LAI in motor circuits of the ipsilateral hemisphere. Measurements were obtained from electromyography (EMG) of the first dorsal interosseous (FDI) at baseline, during cold-water immersion, and during recovery from cold-water immersion. The intervention caused unconditioned MEPs to increase during exposure to the cold stimulus (&lt;i&gt;P&lt;/i&gt; = 0.008) which then returned to baseline levels once the hand was removed from the cold water. MEP responses were decoupled from SAI responses, where SAI was reduced during exposure to the cold stimulus (&lt;i&gt;P&lt;/i&gt; = 0.005) and remained reduced compared to baseline when the hand was removed from the cold water (&lt;i&gt;P&lt;/i&gt; = 0.002). The intervention had no effect on LAI. The uncoupling of SAI from MEPs during the recovery period suggests that the mechanisms underlying the modulation of corticospinal excitability by sensory input may be distinct from those affecting intracortical inhibitory circuits.&lt;/p&gt;\u0000 &lt;/section&gt;\u0000 \u0000 &lt;section&gt;\u0000 \u0000 &lt;h3&gt; Highlights&lt;/h3&gt;\u0000 \u0000 &lt;div&gt;\u0000 &lt;ul&gt;\u0000 \u0000 &lt;li&gt;\u0000 &lt;p&gt;&lt;b&gt;What is the central question of this study?&lt;/b&gt;&lt;/p&gt;\u0000 \u0000 &lt;p&gt;Does immersion of a limb in very cold water influence corticospinal excitability and the level of afferent inhibition exerted on motor cortical circuits?&lt;/p&gt;\u0000 &lt;/li&gt;\u0000 \u0000 &lt;li&gt;\u0000 &lt;p&gt;&lt;b&gt;What is the main finding and its importance?&lt;/b&gt;&lt;/p&gt;\u0000 \u0000 &lt;p&gt;In additional to perception of temperature, immersion in 6°C water also induced perceptions of pain. Motor evoked potential (MEP) amplitude increased during immersion, and short-latency afferent inhibition (SAI) of the motor cortex was reduced during immersion; however, these responses differed after the limb was removed from the cold stimulus, as MEPs returned to normal levels while SAI remained suppressed.&lt;/p&gt;\u0000 &lt;/li&gt;\u0000 &lt;/ul&gt;\u0000 &lt;/div&gt;\u0000 &lt;/section&gt;\u0000 ","PeriodicalId":12092,"journal":{"name":"Experimental Physiology","volume":"109 11","pages":"1817-1825"},"PeriodicalIF":2.6,"publicationDate":"2024-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1113/EP091896","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142079751","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ketone monoester attenuates declines in cognitive performance and oxygen saturation during acute severe hypoxic exposure under resting conditions","authors":"Tyler S. McClure,&nbsp;Jeffrey Phillips,&nbsp;Andrew P. Koutnik,&nbsp;Kody Coleman,&nbsp;Ed Chappe,&nbsp;Gary R. Cutter,&nbsp;Brendan Egan,&nbsp;Todd Norell,&nbsp;Brianna J. Stubbs,&nbsp;Marcas M. Bamman,&nbsp;Dawn Kernagis","doi":"10.1113/EP091794","DOIUrl":"10.1113/EP091794","url":null,"abstract":"&lt;p&gt;Exogenous ketone supplements are a potential augmentation strategy for cognitive resilience during acute hypoxic exposure due to their capacity to attenuate the decline in oxygen (O&lt;sub&gt;2&lt;/sub&gt;) availability, and by providing an alternative substrate for cerebral metabolism. Utilizing a single-blind randomized crossover design, 16 male military personnel (age, 25.3 ± 2.4 year, body mass, 86.2 ± 9.3 kg) performed tests of cognitive performance at rest in three environments: room air (baseline), normoxia (20 min; 0 m; 20.9% O&lt;sub&gt;2&lt;/sub&gt;) and hypoxia (20 min; 6096 m, 9.7% O&lt;sub&gt;2&lt;/sub&gt;) using a reduced O&lt;sub&gt;2&lt;/sub&gt; breathing device (ROBD). (&lt;i&gt;R&lt;/i&gt;)-3-Hydroxybutyl (&lt;i&gt;R&lt;/i&gt;)-3-hydroxybutyrate (R-BD R-βHB) ketone monoester (KME; 650 mg/kg, split dose given at 30 min prior to each exposure) or taste-matched placebo (PLA) was ingested prior to normoxia and hypoxic exposure. Blood R-βHB and glucose concentrations, cognitive performance and O&lt;sub&gt;2&lt;/sub&gt; saturation (&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;S&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;p&lt;/mi&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;O&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msub&gt;\u0000 &lt;annotation&gt;${{S}_{{mathrm{p}}{{{mathrm{O}}}_{mathrm{2}}}}}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;) were collected throughout. KME ingestion increased blood R-βHB concentration, which was rapid and sustained (&gt;4 mM 30 min post; &lt;i&gt;P &lt;/i&gt;&lt; 0.001) and accompanied by lower blood glucose concentration (∼20 mg/dL; &lt;i&gt;P &lt;/i&gt;&lt; 0.01) compared to PLA. Declines in cognitive performance during hypoxic exposure, assessed as cognitive efficiency during a Defense Automated Neurobehavioral Assessment (DANA) code substitution task, were attenuated with KME leading to 6.8 (95% CL: 1.0, 12.6) more correct responses per minute compared to PLA (&lt;i&gt;P&lt;/i&gt; = 0.018). The decline in &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;S&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;p&lt;/mi&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;O&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msub&gt;\u0000 &lt;annotation&gt;${{S}_{{mathrm{p}}{{{mathrm{O}}}_{mathrm{2}}}}}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; during hypoxic exposure was attenuated (6.40% &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;S&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;p&lt;/mi&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;O&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msub&gt;\u0000 &lt;annotation&gt;${{S}_{{mathrm{p}}{{{mathrm{O}}","PeriodicalId":12092,"journal":{"name":"Experimental Physiology","volume":"109 10","pages":"1672-1682"},"PeriodicalIF":2.6,"publicationDate":"2024-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11442756/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142079749","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ketone monoester attenuates oxygen desaturation during weighted ruck exercise under acute hypoxic exposure but does not impact cognitive performance","authors":"Tyler S. McClure,&nbsp;Jeffrey Phillips,&nbsp;Dawn Kernagis,&nbsp;Kody Coleman,&nbsp;Ed Chappe,&nbsp;Gary R. Cutter,&nbsp;Brendan Egan,&nbsp;Todd Norell,&nbsp;Brianna J. Stubbs,&nbsp;Marcas M. Bamman,&nbsp;Andrew P. Koutnik","doi":"10.1113/EP091789","DOIUrl":"10.1113/EP091789","url":null,"abstract":"<p>Acute ingestion of exogenous ketone supplements in the form of a (<i>R</i>)-3-hydroxybutyl (<i>R</i>)-3-hydroxybutyrate (R-BD R-βHB) ketone monoester (KME) can attenuate declines in oxygen availability during hypoxic exposure and might impact cognitive performance at rest and in response to moderate-intensity exercise. In a single-blind randomized crossover design, 16 males performed assessments of cognitive performance before and during hypoxic exposure with moderate exercise [2 × 20 min weighted ruck (∼22 kg) at 3.2 km/h at 10% incline] in a normobaric altitude chamber (4572 m, 11.8% O₂). The R-BD R-βHB KME (573 mg/kg) or a calorie- and taste-matched placebo (∼50 g maltodextrin) were co-ingested with 40 g of dextrose before exposure to hypoxia. The R-βHB concentrations were rapidly elevated and sustained (&gt;3 mM; <i>P </i>&lt; 0.001) by KME. The decline in oxygen saturation during hypoxic exposure was attenuated in KME conditions by 2.4%–4.2% (<i>P </i>&lt; 0.05) compared with placebo. Outcomes of cognitive performance tasks, in the form of the Defense Automated Neurobehavioral Assessment (DANA) code substitution task, the Stroop color and word task, and a shooting simulation, did not differ between trials before and during hypoxic exposure. These data suggest that the acute exogenous ketosis induced by KME ingestion can attenuate declining blood oxygen saturation during acute hypoxic exposure both at rest and during moderate-intensity exercise, but this did not translate into differences in cognitive performance before or after exercise in the conditions investigated.</p>","PeriodicalId":12092,"journal":{"name":"Experimental Physiology","volume":"109 10","pages":"1768-1781"},"PeriodicalIF":2.6,"publicationDate":"2024-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11442785/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142079750","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Skeletal muscle myosin heavy chain fragmentation as a potential marker of protein degradation in response to resistance training and disuse atrophy","authors":"Daniel L. Plotkin,&nbsp;Madison L. Mattingly,&nbsp;Derick A. Anglin,&nbsp;J. Max Michel,&nbsp;Joshua S. Godwin,&nbsp;Mason C. McIntosh,&nbsp;Nicholas J. Kontos,&nbsp;João G. A. Bergamasco,&nbsp;Maíra C. Scarpelli,&nbsp;Vitor Angleri,&nbsp;Lemuel W. Taylor,&nbsp;Darryn S. Willoughby,&nbsp;C. Brooks Mobley,&nbsp;Andreas N. Kavazis,&nbsp;Carlos Ugrinowitsch,&nbsp;Cleiton A. Libardi,&nbsp;Michael D. Roberts","doi":"10.1113/EP092093","DOIUrl":"10.1113/EP092093","url":null,"abstract":"&lt;div&gt;\u0000 \u0000 &lt;section&gt;\u0000 \u0000 \u0000 &lt;p&gt;We examined how resistance exercise (RE), cycling exercise and disuse atrophy affect myosin heavy chain (MyHC) protein fragmentation. The 1boutRE study involved younger men (&lt;i&gt;n&lt;/i&gt; = 8; 5 ± 2 years of RE experience) performing a lower body RE bout with vastus lateralis (VL) biopsies being obtained prior to and acutely following exercise. With the 10weekRT study, VL biopsies were obtained in 36 younger adults before and 24 h after their first/naïve RE bout. Participants also engaged in 10 weeks of resistance training and donated VL biopsies before and 24 h after their last RE bout. VL biopsies were also examined in an acute cycling study (&lt;i&gt;n&lt;/i&gt; = 7) and a study involving 2 weeks of leg immobilization (&lt;i&gt;n&lt;/i&gt; = 20). In the 1boutRE study, fragmentation of all MyHC isoforms (MyHC&lt;sub&gt;Total&lt;/sub&gt;) increased 3 h post-RE (∼200%, &lt;i&gt;P&lt;/i&gt; = 0.018) and returned to pre-exercise levels by 6 h post-RE. Interestingly, a greater magnitude increase in MyHC type IIa versus I isoform fragmentation occurred 3 h post-RE (8.6 ± 6.3-fold vs. 2.1 ± 0.7-fold, &lt;i&gt;P&lt;/i&gt; = 0.018). In 10weekRT participants, the first/naïve and last RE bouts increased MyHC&lt;sub&gt;Total&lt;/sub&gt; fragmentation 24 h post-RE (+65% and +36%, &lt;i&gt;P &lt;/i&gt;&lt; 0.001); however, the last RE bout response was attenuated compared to the first bout (&lt;i&gt;P&lt;/i&gt; = 0.045). Although cycling exercise did not alter MyHC&lt;sub&gt;Total&lt;/sub&gt; fragmentation, ∼8% VL atrophy with 2 weeks of leg immobilization increased MyHC&lt;sub&gt;Total&lt;/sub&gt; fragmentation (∼108%, &lt;i&gt;P &lt;/i&gt;&lt; 0.001). Mechanistic C&lt;sub&gt;2&lt;/sub&gt;C&lt;sub&gt;12&lt;/sub&gt; myotube experiments indicated that MyHC&lt;sub&gt;Total&lt;/sub&gt; fragmentation is likely due to calpain proteases. In summary, RE and disuse atrophy increase MyHC protein fragmentation. Research into how ageing and disease-associated muscle atrophy affect these outcomes is needed.&lt;/p&gt;\u0000 &lt;/section&gt;\u0000 \u0000 &lt;section&gt;\u0000 \u0000 &lt;h3&gt; Highlights&lt;/h3&gt;\u0000 \u0000 &lt;div&gt;\u0000 &lt;ul&gt;\u0000 \u0000 &lt;li&gt;\u0000 &lt;p&gt;&lt;b&gt;What is the central question of this study?&lt;/b&gt;&lt;/p&gt;\u0000 \u0000 &lt;p&gt;How different exercise stressors and disuse affect skeletal muscle myosin heavy chain fragmentation.&lt;/p&gt;\u0000 &lt;/li&gt;\u0000 \u0000 &lt;li&gt;\u0000 &lt;p&gt;&lt;b&gt;What is the main finding and its importance?&lt;/b&gt;&lt;/p&gt;\u0000 \u0000 &lt;p&gt;This investigation is the first to demonstrate that resistance exercise and disuse atrophy lead to skeletal muscle myosin heavy chain protein fragmentation in humans. Mechanistic in vitro experiments provide additional evidence that MyHC fragmentation occurs through calpain proteases.&lt;/p&gt;\u0000 &lt;/li&gt;\u0000 &lt;/ul&gt;\u0000 &lt;/div&gt;\u0000 &lt;/","PeriodicalId":12092,"journal":{"name":"Experimental Physiology","volume":"109 10","pages":"1739-1754"},"PeriodicalIF":2.6,"publicationDate":"2024-08-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11442757/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142046475","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Is there reversible dimerization of albumin in blood plasma? And does it matter?","authors":"Gemma Harris,&nbsp;Michelle L. Bradshaw,&nbsp;David J. Halsall,&nbsp;David J. Scott,&nbsp;Robert J. Unwin,&nbsp;Anthony G. W. Norden","doi":"10.1113/EP092012","DOIUrl":"10.1113/EP092012","url":null,"abstract":"<p>Most albumin in blood plasma is thought to be monomeric with some 5% covalently dimerized. However, many reports in the recent biophysics literature find that albumin is reversibly dimerized or even oligomerized. We review data on this from X-ray crystallography and diverse biophysical techniques. The number-average molecular weight of albumin would be increased by dimerization, affecting size-dependent filtration processes of albumin such as at the glycocalyx of the capillary endothelium and the podocyte slit-diaphragm of the renal glomerulus. If correct, and depending on characteristics of the process, such as <i>K</i>_d, reversible dimerization of albumin in plasma would have major implications for normal physiology and medicine. We present quantitative models of the impact of dimerization on albumin molecular forms, on the number-average molecular weight of albumin, and estimate the effect on the colloid osmotic pressure of albumin. Dimerization reduces colloid osmotic pressure as total albumin concentration increases below that expected in the absence of dimerization. Current models of albumin filtration by the renal glomerulus would need revision to account for the dynamic size of albumin molecules filtered. More robust biophysical data are needed to give a definitive answer to the questions posed and we suggest possible approaches to this.</p>","PeriodicalId":12092,"journal":{"name":"Experimental Physiology","volume":"109 10","pages":"1663-1671"},"PeriodicalIF":2.6,"publicationDate":"2024-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11442857/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142035600","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Heat and carbon monoxide exposure: Is two better than one?","authors":"Kevin L. Webb,&nbsp;José González-Alonso","doi":"10.1113/EP092198","DOIUrl":"10.1113/EP092198","url":null,"abstract":"&lt;p&gt;A fundamental aim in the field of human physiology is to understand and delineate the limits of human function. In the realm of exercise physiology, sports and aerobic performance, the preceding decades have been marked by investigation into exogenous mechanisms of blood doping, exemplified by the administration of recombinant erythropoietin (EPO), erythropoiesis stimulating agents and whole blood transfusion. Yet, the line between such ‘artificial’ methods of blood doping and natural adaptation becomes blurred as we better understand how to manipulate haematological parameters through methodologies currently allowed by international sporting committees.&lt;/p&gt;&lt;p&gt;In this issue of &lt;i&gt;Experimental Physiology&lt;/i&gt;, DiMarco et al. provide insight into two acute interventions that elicit haematological adaptation with potential ergogenic effects (DiMarco et al., &lt;span&gt;2024&lt;/span&gt;). First, carbon monoxide exposure reduces arterial blood oxygenation, impairing oxygen delivery to the visceral organs such as the kidneys with little renal blood flow compensation (Schmidt et al., &lt;span&gt;2020&lt;/span&gt;). In response, the kidney detects a reduction in oxygen delivery and stimulates the production of EPO, increasing haemoglobin mass in compensation (Montero &amp; Lundby, &lt;span&gt;2019&lt;/span&gt;). Through differing mechanisms, acute heat exposure is generally considered to reduce renal blood flow, lowering oxygen delivery and thus evoking a similar EPO response in compensation (Oberholzer et al., &lt;span&gt;2019&lt;/span&gt;). The potential utility of carbon monoxide and heat exposure is to increase the total amount of red blood cells and haemoglobin mass, which have been positively associated with a greater aerobic capacity and athletic performance (Schmidt &amp; Prommer, &lt;span&gt;2010&lt;/span&gt;). Both methodologies elicit haematological responses that have been studied previously, but the novelty of DiMarco et al.’s work stems from (1) evaluating a hypothetical potentiating effect of performing acute carbon monoxide exposure and passive heating concomitantly, and (2) investigating potential sex differences yet to be addressed.&lt;/p&gt;&lt;p&gt;DiMarco et al. undertook their investigation with 16 participants (eight males and females), measuring the circulatory EPO response and appropriate physiological parameters during three randomized visits (carbon monoxide inhalation, heat exposure through hot water immersion, and both carbon monoxide inhalation and heat exposure) (DiMarco et al., &lt;span&gt;2024&lt;/span&gt;). Each visit involved 6 h of venous measurements following the acute intervention. For the visits containing carbon monoxide exposure, a single bolus was rebreathed for 10 min with the aim of increasing carboxyhaemoglobin to 10–15%. For the visits with hot water immersion, participants sat upright in heated water (40°C) for 45 min while measuring core body temperature through an ingested pill sensor. When administered independently, acute carbon monoxide and heat exposure elicited a significant incr","PeriodicalId":12092,"journal":{"name":"Experimental Physiology","volume":"109 10","pages":"1627-1628"},"PeriodicalIF":2.6,"publicationDate":"2024-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11442776/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142035599","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The effect of female breast surface area on skin stiffness and tactile sensitivity at rest and following exercise in the heat","authors":"Hannah Blount,&nbsp;Alessandro Valenza,&nbsp;Jade Ward,&nbsp;Silvia Caggiari,&nbsp;Peter R. Worsley,&nbsp;Davide Filingeri","doi":"10.1113/EP091990","DOIUrl":"10.1113/EP091990","url":null,"abstract":"<p>Female development includes significant morphological changes across the breast. Yet, whether differences in breast surface area (BrSA) modify breast skin stiffness and tactile sensitivity at rest and after exercise in the heat remain unclear. We investigated the relationship between BrSA and skin stiffness and tactile sensitivity in 20 young to middle-aged women (27 ± 8 years of age) of varying breast sizes (BrSA range: 147–502 cm²) at rest and after a submaximal run in a warm climatic chamber (32<span></span><math>\u0000 <semantics>\u0000 <mi>C</mi>\u0000 <annotation>${mathrm{C}}$</annotation>\u0000 </semantics></math> ± <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mn>0</mn>\u0000 <mrow>\u0000 <mo>.</mo>\u0000 <mn>6</mn>\u0000 <mi>C</mi>\u0000 <mo>;</mo>\u0000 </mrow>\u0000 </mrow>\u0000 <annotation>${mathrm{0}}{mathrm{.6C;}}$</annotation>\u0000 </semantics></math> 53% ± 1.7% relative humidity). Skin stiffness above and below the nipple and tactile sensitivity from the nipple down were measured. Associations between BrSA and both skin stiffness and tactile sensitivity at rest were determined via correlation analyses. Effects of exercise and test site were assessed by a two-way ANOVA. Skin stiffness was positively correlated with BrSA 3 cm above the areola edge (<i>r</i> = 0.61, <i>P </i>= 0.005) and at the superior areola border (<i>r</i> = 0.54, <i>P </i>= 0.016), but not below the nipple (<i>P </i>&gt; 0.05). The area 3 cm below the areola was also significantly stiffer than all other test sites (<i>P </i>&lt; 0.043). Tactile sensitivity did not vary with BrSA (<i>P </i>&gt; 0.09), but it varied across the breast (i.e., the area 3 cm below the areola was more sensitive than the inferior areola edge; <i>P </i>= 0.018). Skin stiffness and tactile sensitivity across the breast decreased after exercise by ∼37% (<i>P </i>&lt; 0.001) and ∼45% (<i>P </i>= 0.008), respectively. These findings expand our fundamental understanding of the mechanosensory properties of the female breast, and they could help to inform sportswear innovation to better meet the support needs of women of different breast sizes at rest and following exercise.</p>","PeriodicalId":12092,"journal":{"name":"Experimental Physiology","volume":"109 10","pages":"1698-1709"},"PeriodicalIF":2.6,"publicationDate":"2024-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11442787/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142035622","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Alpha band oscillations in common synaptic input are explanatory of the complexity of isometric knee extensor muscle torque signals","authors":"Christopher R. J. Fennell,&nbsp;Alexis R. Mauger,&nbsp;James G. Hopker","doi":"10.1113/EP092031","DOIUrl":"10.1113/EP092031","url":null,"abstract":"<p>We investigated whether the strength of oscillations in common synaptic input was explanatory of knee extensor (KE) torque signal complexity during fresh and fatigued submaximal isometric contractions, in adults aged from 18 to 90 years. The discharge times of motor units were derived from the vastus lateralis muscle of 60 participants using high-density surface EMG, during 20 s isometric KE contractions at 20% of maximal voluntary contraction, performed before and after a fatiguing repeated isometric KE contraction protocol at 60% of maximal voluntary contraction. Within-muscle coherence Z-scores were estimated using frequency-domain coherence analysis, and muscle torque complexity was assessed using multiscale entropy analysis and detrended fluctuation analysis. Alpha band (5–15 Hz) coherence was found to predict 23.1% and 31.4% of the variance in the complexity index under 28-scales (CI-28) and detrended fluctuation analysis α complexity metrics, respectively, during the fresh contractions. Delta, alpha and low beta band coherence were significantly increased due to fatigue. Fatigue-related changes in alpha coherence were significantly predictive of the fatigue-related changes in CI-28 and detrended fluctuation analysis α. The fatigue-related increase in sample entropy from scales 11 to 28 of the multiscale entropy analysis curves was significantly predicted by the increase in the alpha band coherence. Age was not a contributory factor to the fatigue-related changes in within-muscle coherence and torque signal complexity. These findings indicate that the strength of alpha band oscillations in common synaptic input can explain, in part, isometric KE torque signal complexity and the fatigue-related changes in torque signal complexity.</p>","PeriodicalId":12092,"journal":{"name":"Experimental Physiology","volume":"109 11","pages":"1938-1954"},"PeriodicalIF":2.6,"publicationDate":"2024-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1113/EP092031","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142003957","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}