bluuebunny/crossref_metadata_2025_split huggingface dataset:
Impact of repeated local heat stress on skeletal muscle structure and function in humans
Authors: Kim Kyoungrae , Trewin Adam , Petersen Aaron C. , Gavin Timothy P. , Roseguini Bruno T. 
Published: June 2021

IntroductionShort‐term exposure to heat stress has been shown to enhance muscle strength and elicit mitochondrial adaptations in human skeletal muscle. We recently documented that exposure to five sessions of heat therapy (HT) accelerates the recovery of fatigue resistance following exercise‐induced muscle damage in humans. However, the long‐term impact of repeated exposure to local heat stress on contractile function and skeletal muscle structure remains unknown. The purpose of the present study was to examine the effects of 8 weeks of daily treatment with local HT on muscle strength, fatigability, fiber size and mitochondrial content in humans.MethodsTwelve healthy young adults (23.6±1.4 years, BMI 24.9±0.9 kg/m2) had one randomly selected thigh treated with daily HT for 8 consecutive weeks while the opposite thigh served as a control. A water‐circulating garment perfused with water at ~52ºC was used to apply HT for 90 min daily. Knee extensor strength (single peak torque during 3 repetition maximums at 180°/s and 60°/s) and fatigue resistance (total work during 40 repetition maximums at 180°/s) were assessed using isokinetic dynamometry before and after 4 and 8 weeks of treatment. Biopsies were obtained from the vastus lateralis muscle for the determination of myofiber cross‐sectional area and maximal citrate synthase activity.ResultsTreatment with HT elicited an increase in thigh skin temperature (39.8±0.1ºC), while skin temperature remained at baseline levels in the control thigh (32.4± 0.1ºC). A significant treatment effect was observed for the changes from baseline in peak isokinetic torque at 180º/s (p=0.04). On average, the changes in peak isokinetic torque from baseline for HT were ~2 fold higher than control at week 4 (Control: 4.1±3.7 Nm vs. HT: 9±4.6 Nm) and ~4 fold higher at week 8 (Control: 1.7±2.7 Nm vs. HT: 7.7±2.9 Nm). There were no differences between treatments for peak isokinetic torque at 60º/s, myofiber cross‐sectional area and citrate synthase activity.ConclusionThese results indicate that daily exposure to HT for 8 weeks enhances muscle strength in humans. Local HT may be a practical therapeutic approach to improve muscle function in individuals with limited mobility and skeletal muscle weakness.Support or Funding InformationSupport: American College of Sports Medicine Research EndowmentThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Mechanisms Underlying the Stimulatory Effect of Inhaled Sulfur Dioxide on Rat Vagal Bronchopulmonary Sensory Nerves
Authors: Lin An‐Hsuan , Hsu Chun‐Chun , Lin You‐Shuei , Lin Ruei‐Lung , Lee Lu‐Yuan 
Published: June 2021

Chronic exposure to sulfur dioxide (SO2), an air pollutant, can cause airway injury and lung diseases. Acute exposure to SO2 triggers cough and reflex bronchoconstriction, indicating a stimulatory effect of SO2 on airway sensory nerves. Indeed, a recent study in our lab has demonstrated that vagal bronchopulmonary C‐fibers are the primary target of inhaled SO2. This study was carried out to investigate the underlying mechanism of this stimulatory effect of SO2 on bronchopulmonary C‐fibers. Our results showed: 1) Inhalation of SO2 (1,000–2,000 ppm, 10 breaths) evoked a pronounced and reproducible stimulatory effect on pulmonary C‐fibers in anesthetized rats. 2) Pretreatment with an intravenous infusion of sodium bicarbonate (120 μmol/kg) raised the baseline arterial pH by 0.08 units, which profoundly diminished the stimulatory effect of SO2 on pulmonary C‐fibers by 83.9%. 3) This stimulatory effect of SO2 was also significantly attenuated by a pretreatment with amiloride (a blocker of acid‐sensing ion channels, ASICs; 11 μmol/kg) alone (Δ = 70.7%); AMG9810 (an antagonist of transient receptor potential vanilloid type‐1, TRPV1; 10 μmol/kg) alone (Δ = 76.7%); and by a combination of amiloride and AMG9810 (Δ = 91.4%). 4) To further investigate if this stimulatory effect is generated by a direct action of SO2 on sensory nerves, the change in intracellular Ca2+ concentration, [Ca2+]i, was measured in isolated rat vagal pulmonary sensory neurons. Perfusion with extracellular fluid saturated with SO2 (1,000 and 2,000 ppm) evoked a significant increase in [Ca2+]i in a concentration‐dependent manner in these neurons, and these responses to SO2 were markedly suppressed by a combined pretreatment with amiloride and AMG9810. 5) In addition, inhalation of SO2 (300 and 600 ppm for 5 min) evoked cough reflex responses consistently in awake mice in a concentration‐dependent manner; the cough responses were almost completely prevented by a pretreatment with amiloride aerosol inhalation (5 mM for 4 min) in TRPV1‐knockout mice. In conclusion, this study suggested that inhalation of SO2 lowered the pH in airway/lung tissues, which exerted a stimulatory effect on vagal bronchopulmonary C‐fibers by activating both ASICs and TRPV1 channels.Support or Funding InformationNIH grants AI123832 & UL1TR001998This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Differential Circulating microRNA Expression after Bed Rest: Potential Role in Cardiovascular Deconditioning
Authors: Ade Carl J 
Published: June 2021

Bed rest, an analog of spaceflight microgravity, elicits changes in left ventricular loading conditions resulting in cardiac deconditioning that adversely effects functional outcomes and cardiopulmonary exercise performance. Given the significant and time‐dependent changes in cardiovascular function associated with bed rest, a continued evaluation of these adaptations are required, particularly in regards to their molecular regulators. MicroRNAs are noncoding RNA that regulate gene expression, with several plasma‐based ‘circulating’ microRNAs (c‐miRs) used as biomarkers of tissue‐specific physiologic adaptation. Quantification of cardiac‐c‐miRs may allow for manifestations of cardiovascular deconditioning to be identified and be used to predict cardiovascular related outcomes in response to bed rest. Therefore, the primary aim of this study was to test the hypotheses that cardiovascular‐c‐miRs are differentially expressed following bed rest and their changes associated with decreases in cardiac function and cardiopulmonary exercise capacity. Eleven participants completed 30‐days bed rest at an ambient CO2 of 0.05% (replicate CO2 levels on the International Space Station). Blood samples were obtained prior to and immediately following bed rest. 44‐targeted c‐miRs identified from published roles in cardiovascular structure/function were analyzed via RT‐qPCR. Resting stroke volume was evaluated via ultrasonography. Peak oxygen uptake (peakVO2) was determined using a grade exercise test. Ten cardiovascular‐c‐miRs were significantly increased following bed rest. The differentially expressed c‐miRs were grouped into clusters according to their expression profile. Cluster A included c‐miRs that have been identified as regulators of cardiac function and hypertrophy (c‐miR‐133), atrial fibrillation and mitochondrial function (c‐miR‐1), skeletal muscle atrophy (c‐miR‐1), vascular control (c‐miR‐155) and aerobic capacity (c‐miR‐133). Cluster B contained c‐miR identified as regulators of cardiac hypertrophy (c‐miR‐30, c‐miR‐15), fibrosis (c‐miR‐22, c‐miR‐18), mitochondrial function (c‐miR‐181), and aerobic capacity (c‐miR‐20a). Following bed rest stroke volume was decreased and correlated with changes in cmiR‐18a and c‐miR‐378a. PeakVO2 was decreased and correlated with changes in c‐miR‐133. In conclusion, we found that bed rest induced a distinct and specific cardiovascular‐c‐miR response, which was associated with changes in cardiac function and cardiopulmonary exercise capacity. Although future work is required, these results suggest the potential value of c‐miRs as biomarkers and their possible role as physiological mediators of cardiovascular deconditioning to bed rest.Support or Funding InformationNational Aeronautics and Space Administration (NASA) research grant awarded to C.J AdeThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Age‐Associated Differences in Central Artery Responsiveness to Sympathoexcitation: Influence of Blood Pressure
Authors: Bock Joshua M , Hughes William , Sheehy Kathryn , Asama Thomas , Horak Jeffrey , Casey Darren 
Published: June 2021

Aging is associated with increased central artery stiffness, a potential consequence of greater tonic sympathetic nerve activity. However, less is known regarding age‐associated changes in central artery responsiveness to acute sympathoexcitation. Therefore, we tested the hypothesis that older adults would demonstrate greater increases in central artery stiffness (carotid‐femoral pulse wave velocity, cfPWV) and wave reflection (augmentation index, AIx) during the cold pressor test (CPT) compared to young adults. To control for the potential confound of blood pressure on our measurements we also employed lower‐body negative pressure (LBNP), a sympathoexcitatory stimuli with minimal influence on blood pressure. We hypothesized that older adults would have less reduction in AIx during LBNP compared to the young adults. Fourteen young (25±4yrs) and 15 older (68±4yrs) subjects completed three minutes of LBNP and CPT on a single study visit, separated by a 15‐minute washout period, in random order. Duplicate measures of cfPWV and AIx were taken at baseline and during the final minute of each perturbation. Baseline heart rate and mean arterial pressure (MAP) were not different between groups (p≥0.05 for both); however, young subjects had lower baseline cfPWV and AIx compared to older subjects (p<0.05 for both). In response to the CPT, heart rate, MAP, cfPWV, and AIx increased in both young and older groups (main effect of time p<0.01 for all); however, the change (Δ) in MAP (18±7 vs. 9±5mmHg), cfPWV (1.3±0.7 vs. 0.6±0.9m·sec−1), and AIx (17±9 vs. 7±4%) were greater in young compared to older subjects, respectively (p<0.05 for all). In response to LBNP, the changes (Δ) in MAP (−1±3 vs. −3±5mmHg), and cfPWV (0.5±0.3 vs. 0.5±0.7m·sec−1) were similar between age groups (main effect of time p<0.05 for all) although young subjects showed a greater reduction in AIx compared to their older counterparts (−8±7 vs. −2±6%, p<0.01). Interestingly, when MAP was used as a covariate, the group‐by‐time interaction for cfPWV and AIx during the CPT as well as AIx during LBNP were no longer significant (p=0.48, 0.11, and 0.39, respectively). Given that the age‐associated differences in cfPWV responsiveness to the CPT was mitigated with MAP as a covariate, and the increase in cfPWV was not different between groups in response to LBNP (no change in MAP), our data suggest age‐associated differences in central artery responsiveness to sympathoexcitation are greatly influenced by changes in MAP.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Are Spontaneous Low Frequency Oscillations in Arterial Pressure and Cerebral Blood Flow Associated with the Protection of Cerebral Tissue Oxygenation during Simulated Hemorrhage?
Authors: Anderson Garen K. , Rosenberg Alexander (A.J.) , Kay Victoria L. , Sprick Justin D. , Rickards Caroline A. 
Published: June 2021

IntroductionPrior studies have independently demonstrated that subjects with higher tolerance to simulated hemorrhage elicited by lower body negative pressure (LBNP) exhibit maintenance of cerebral tissue oxygenation, and higher amplitude in spontaneously generated low frequency (~0.1 Hz) oscillations in arterial pressure and cerebral blood flow. We hypothesized that these two independent observations are related, wherein subjects with higher tolerance to LBNP would exhibit increased low frequency power in arterial pressure and cerebral blood flow, which may contribute to the protection of cerebral tissue oxygenation.MethodsHealthy male (n=19, 25±1 y) and female (n=13, 28±1 y) subjects participated in a stepwise LBNP protocol to pre‐syncope. Mean arterial pressure (MAP), middle cerebral artery velocity (MCAv), cerebral tissue oxygen saturation (ScO2), and end tidal CO2 (etCO2) were measured continuously. Subjects were classified as high tolerant if they completed the −60 mmHg step of LBNP. Low frequency oscillations in MAP and MCAv were assessed in the 0.04–0.15 Hz range. Both time and frequency domain data were analyzed using a linear mixed model analysis of variance with Tukey post hoc tests. Comparisons were made at baseline across LBNP stages (−15, −30, −45, and −60 mmHg).ResultsOf the 32 subjects tested, 20 were classified as high tolerant and 12 as low tolerant. No differences were observed between high and low tolerant subjects in MAP (P=0.28), low frequency power of MAP (P=0.13), or low frequency power of MCAv (P=0.24) during LBNP. However, high tolerant subjects exhibited greater protection against reductions in ScO2 (P<0.01), MCAv (P<0.01), and etCO2 (P<0.01) compared to low tolerant subjects during LBNP.ConclusionContrary to our hypothesis, low frequency oscillations in MAP and MCAv did not account for the observed protection in ScO2 for high tolerant subjects. Rather, maintenance of oxygen delivery (indexed via MCAv) appeared to account for the protection in cerebral oxygenation in this cohort of young, healthy subjects.Support or Funding InformationFunding for this study was provided by the U.S. Army MRMC Combat Casualty Care Research Program Grant # W81XWH‐11‐2‐0137, and a contract with Pendar Medical LLC. The content is solely the responsibility of the authors and does not necessarily represent the official views the US Department of Defense.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
High intensity interval exercise reduces tolerance to a simulated hemorrhagic challenge relative to steady state exercise in heat stressed individuals
Authors: Trotter Claire E , Pizzey Faith K , Batterson Philip M , Jacobs Robert A , Pearson James 
Published: June 2021

Individuals who are exposed to an increased risk of experiencing a hemorrhagic insult, such as soldiers and firefighters, are often required to complete intermittent high intensity exercise in the presence of environmental heat stress. In normothermic conditions, increases in heart rate and reductions in vascular resistance can be greater following high intensity interval exercise relative to continuous steady state exercise. These hemodynamic alterations following high intensity interval exercise may reduce the capacity to withstand a hemorrhagic insult. We investigated whether high intensity interval exercise reduces tolerance to a simulated hemorrhagic challenge (lower body negative pressure; LBNP) relative to steady state exercise in heat stressed individuals. Eight healthy participants (Age: 27 ± 5 years; Ht: 179 ± 9 cm; Wt: 78.9 ± 18.7 kg) completed two trials (Steady state and Interval). Participants performed cycling exercise either by alternating between 10 and 88% (Interval) or continuously at 38% (Steady state) of the predetermined maximal aerobic power output whilst wearing a warm water perfused suit until core temperatures increased by 1.40 ± 0.21°C. Participants then underwent progressive LBNP (−20mmHg, −30mmHg, etc.) to pre syncope. LBNP tolerance was quantified as cumulative stress index (CSI; mmHg*min). Following exercise and prior to LBNP, mean skin temperatures were similarly elevated from baseline in both trials (from: 32.35 ± 0.42 to 37.95 ± 0.59°C, P < 0.05). Mean arterial pressure was not different between trials prior to LBNP (Interval: 79 ± 6 vs. Steady state: 77 ± 7 mmHg; P = 0.57) and were similarly reduced in both trials at pre syncope (to 63 ± 6 and 62 ± 6 mmHg respectively, both P < 0.05). CSI was lower in the interval trial relative to the steady state trial (280 ± 204 vs. 518 ± 285 mmHg*min, respectively; P = 0.024). In heat stressed individuals, tolerance to a simulated hemorrhagic challenge was reduced following high intensity interval exercise relative to steady state exercise. These findings have implications for individuals who exercise at intermittent high intensities in hot environments and are at increased risk of experiencing a hemorrhagic injury (e.g. soldiers, firefighters and miners).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Childhood Adversity Impairs the Autonomic Response to Acute Stress
Authors: Looney Jacob , Tucker Matthew A. , Jeong Jin Hee , Pollock David M. , Pollock Jennifer S. , Harris Ryan A. 
Published: June 2021

Individuals exposed to adverse childhood events (ACE) have an increased risk of developing cardiovascular disease in adulthood. In addition, low heart rate variability (HRV) is associated with an increased risk of coronary heart disease and is an independent predictor of mortality. The HRV response to acute stress, such as the cold pressor test (CPT), provides insight into autonomic function. Whether or not ACE impacts autonomic function during the CPT has yet to be determined.PURPOSETo determine whether ACE influences HRV during the CPT.METHODS12 adult participants (aged 34±5 years) volunteered for this study, half of which were classified as HI‐ACE (ACE score ≥ 4; n=6) and the other half as NO‐ACE (ACE score = 0; n=6). All participants underwent a CPT protocol which consisted of a 5 min baseline, 3 min of right hand submersion in ice water (~2°C), and a 5 min recovery period. HRV was determined using inter‐beat intervals and calculation of the root mean square of successive differences (rMSSD). In addition, hemodynamic parameters including heart rate (HR), cardiac index (CI), mean arterial pressure (MAP), and total peripheral resistance index (TPRI) were measured throughout the CPT protocol using infrared fingertip plethysmography (Finapres NOVA).RESULTSDemographics were similar between groups and no differences (all p>0.05) were observed in baseline values of HR (61±9 vs.65±5 bpm), SBP (125±9 vs. 124±15 mm Hg), or DBP (78±8 vs. 71±10 mm Hg). rMSSD was significantly lower during the CPT compared to both baseline (p=0.032) and recovery (p=0.006) in NO‐ACE. No significant changes in rMSSD in response to CPT were observed in HI‐ACE. The hemodynamic (HR, CI, MAP, and TPRI) response to CPT was similar (all p>0.05) between ACE groups.CONCLUSIONThese data indicate that autonomic function, represented by rMSSD in response to CPT, is blunted in individuals who have experienced childhood adversity compared to those who have not. Given that the HI‐ACE group presented as normotensive and otherwise apparently healthy, future studies are needed to better understand contributors to autonomic dysfunction in this cohort.Support or Funding InformationSupported in part by NIH/NHLBI P01HL069999 (DMP, JSP, RAH).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Effects of Acute Beetroot Juice Supplementation on Power, Velocity, and Repetitions to Failure during Resistance Exercise
Authors: Ballmann Christopher G , Martin Mary Page , Rogers Rebecca R , Williams Tyler D 
Published: June 2021

PURPOSEThe purpose of this study was to examine the effects of acute beetroot juice (BRJ) supplementation on power, velocity, and repetitions to failure (RTF) during bench press exercise.METHODSResistance‐trained male participants were recruited for this study. In a within groups counterbalanced study design, participants were supplemented with either 70 ml of BRJ or placebo (Black‐currant juice; PL) two hours before exercise. During each exercise trial, participants began by completing 2 sets × 2 reps of bench press at 70% 1‐RM with maximum explosive intent. Power and velocity of barbell movement was measured using a linear position transducer. Participants then completed 3 sets × RTF at 70% 1‐RM separated by 2 minutes of rest between each set. Maximum mean power, velocity, and total RTF were analyzed.RESULTSVelocity of barbell movement was significantly higher with BRJ when compared to PL (p=0.011; ES=1.3). Furthermore, power of barbell movement was significantly higher with BRJ versus PL (p=0.015; ES= 0.58). Total RTF was not different with BRJ versus PL (p=0.091; ES= 0.55).CONCLUSIONResults indicate that acute BRJ supplementation positively impacts both velocity and power during bench press exercise.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
The Influence of Caffeine and the −163 A>C CYP1A2 Polymorphism on Peak and Mean Power during a Wingate Test
Authors: Smith Caleb R. , Eberly Julia , Steckbeck Rachel J. , Wright Madison R. , Shenk Brian , Shin Michael , Kieffer H. Scott 
Published: June 2021

The influence of the cytochrome P450 enzymes, specifically a polymorphism of the CYP1A2 genotype, following caffeine ingestion has been shown to influence aerobic endurance; however, the effect on short‐term anaerobic performance is inconclusive. Individuals with the AA variant are responders to caffeine and those with the AC/CC variant are non‐responders.PURPOSETo examine the effects of caffeine and specific CYP1A2 genotype on anaerobic performance.METHODS10 subjects completed two 30 second Wingate Anaerobic Tests (WAnT30) (resistance = 0.075 kg•BW−1) on the Velotron that were separated by 2 to 7 days. Relative peak power (PP) and relative mean power (MP) were computed by the Velotron software. An oral bolus of caffeine (CAF), 5mg•kg−1, or placebo (PLA), maltodextrin, was given in a randomized and counterbalanced design 60 min prior to testing. Buccal epithelial cells were collected via a mouth rinse of 0.9% NaCl. Genomic extraction was obtained using QiAmp Mini spin columns and cell lysing with proteinase k, followed by PCR amplification with Fast Taq. The restriction enzyme (ApaI) was used to cut fragments. Cut and uncut samples underwent electrophoresis in 1% agarose gel and ultraviolet light photography identified genotype. The data was analyzed using a 2 (condition) × 2 (CYP) ANOVA with repeated measures (p>0.05).RESULTS5 people were AA and 5 people were AC/CC. The results revealed that CAF elicited no ergogenic effects. The main effect of condition, PLA versus CAF, showed no significant difference for PP or MP (p = 0.49). The main effect of CYP1A2, AA or AC/CC, did not reveal power differences for PP or MP (p = 0.96). Follow‐up pairwise comparisons between PLA to CAF for PP (W•kg−1) showed non‐significant D's of 1.17% in AA (10.3 and 10.42) and −0.38% for AC/CC (10.36 and 10.46, respectively). Likewise, MP resulted in non‐significant D's of 3.66% for AA (8.2 and 8.5 W•kg−1, respectively) and 2.24% for AC/CC (8.3 and 8.5, W•kg−1 respectively).CONCLUSIONCaffeine did not produce an ergogenic effect for anaerobic exercise, regardless of an individual's CYP1A2 variant. However, the larger percent increases, specifically in MP, suggest that further research should be conducted, such as increasing sample size and identifying confounding variables such as other receptor sites that may interact with caffeine.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.