bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Carotid Sinus Nerve Transection on Ventilation in Juvenile (P25) Male Sprague‐Dawley Rats
Authors: Getsy Paulina M , Coffee Gregory A , Lewis Stephen J
Published: November 2023

The carotid body chemoafferents play an essential role in altering ventilation in response to hypoxia, hypercapnia, and acidosis. The retropezoid nucleus in the brainstem also plays a key role in responding to hypercapnia. The effects of exposure to hypoxic (HX), hypercapnic (HC) or hypoxic‐hypercapnic (HH) gas challenges have been studied in young, adult, and elderly subjects. However, little is known about the role of the carotid body in the ventilatory responses elicited by these gas challenges in juvenile rats.

Our objective was to determine the role of the carotid body chemoafferents in the ventilatory responses elicited by HX (10% O2, 90% N2), HC (5% CO2, 21% O2, 74% N2) or HH (10% O2, 5% CO2, 85% N2) gas challenges (5 episodes of 5 min in duration separated by 15 min) in freely‐moving juvenile (P25) male Sprague‐Dawley rats.

Rats (P21) were subjected to sham or bilateral carotid sinus nerve transection (CSNX) and were allowed 4 days to recover before use in the experiments. On the day of study, the P25 rats were placed in whole‐body plethysmography chambers and after allowing them to acclimatize, they were subjected to one of the above gas exposures. Ventilatory parameters included, frequency of breathing, tidal volume, minute ventilation (= frequency × tidal volume), inspiratory and expiatory times, end inspiratory and expiratory pauses, peak inspiratory and expiratory flows, EF50 (expiratory flow at 50% expired tidal volume) and central inspiratory drive (tidal volume/inspiratory time).

The HX challenges elicited robust ventilatory responses in sham‐operated rats. As expected, these responses, such as the increase in minute ventilation, were markedly diminished in CSNX rats. The HC challenges also elicited robust ventilatory responses in sham‐operated rats. Some responses, including the increases in minute ventilation and EF50, were slightly smaller in CSNX rats. The HH challenges elicited very robust ventilatory responses. Unexpectedly, these responses including, (1) increases in frequency of breathing, tidal volume, minute ventilation, peak inspiratory and expiratory flows, EF50, and central inspiratory drive, and (2) the decreases in inspiratory and expiratory times, and end inspiratory and expiratory pauses, were dramatically diminished in CSNX rats.

These findings demonstrate that the carotid sinus chemoafferents play a major role in integrating the ventilatory responses to hypoxic‐hypercapnic gas challenges in juvenile rats. Considering that these gas challenges alter arterial blood gas chemistry to values seen during apneic episodes, our findings may be relevant to understanding the role of carotid body chemoafferents in sleep‐disordered breathing.

Support or Funding Information

GlaxoSmithKline (GSK) FundingCWRU Internal Number: RES510692
Mesenchymal Stem Cell‐Derived Extracellular Vesicles Improve the Renal Microvasculature in Coexisting Metabolic Syndrome and Renovascular Disease in Swine
Authors: Eirin Alfonso , Zhu Xiang‐Yang , Ferguson Christopher M , van Wijnen Andre J , Lerman Amir , Lerman Lilach O
Published: November 2023

Background

Superimposition of the metabolic syndrome (MetS) on renovascular disease (RVD) amplifies intrarenal microvascular loss. Extracellular vesicles (EVs) released from adipose tissue‐derived mesenchymal stem/stromal cells (MSCs) may mediate their paracrine effect, but their efficacy to protect the renal microcirculation in RVD complicated by MetS remains unclear. Using a novel swine model, we tested the hypothesis that EVs would attenuate microvascular loss in MetS+RVD.

Methods

Four groups of pigs (n=7 each) were studied after 16 weeks of diet‐induced MetS and unilateral RVD (MetS+RVD), MetS+RVD treated 4 weeks earlier with a single intra‐renal delivery of pre‐labeled EVs harvested from autologous MSCs, and Lean and MetS Sham controls. Stenotic‐kidney renal blood flow (RBF) and glomerular filtration rate (GFR) were measured in‐vivo (fast CT), whereas EV characteristics, renal microvascular architecture (micro‐CT), and injury pathways ex‐vivo.

Results

mRNA sequencing of EVs and their parent MSCs revealed that EVs were enriched with pro‐angiogenic genes, including vascular endothelial growth factor (VEGF)‐A, VEGF–C, and Von Willebrand Factor (vWF)‐A Domain Containing‐1 (VWA)‐1 (Figure A). In addition, protein expression of VEGF and vWF was higher in EVs compared to MSCs (Figure B). EVs were detected in the stenotic‐kidney ex‐vivo internalized by tubular and endothelial cells. EVs restored renal expression of the pro‐angiogenic factors VEGF, Notch‐1, and Notch ligand delta‐like‐4 (DLL4) and improved cortical microvascular density (Figure C–D). Tubulointerstitial fibrosis increased and RBF and GFR decreased in MetS+RVD vs. MetS, but were restored in MetS+RVD+EV (Figure E–F).

Conclusions

Intra‐renal delivery of MSC‐derived EVs bearing pro‐angiogenic properties in swine MetS+RVD restored stenotic‐kidney microcirculation, and in turn its hemodynamics and function. Our study suggests a novel therapeutic potential for MSC‐derived EVs in restoring renal function in chronic experimental MetS+RVD.

Support or Funding Information

This study was partly supported by NIH grant numbers DK73608, DK104273, HL123160, and DK102325, DK106427, the Mayo Clinic Center for Regenerative Medicine, and the Mayo Clinic Mary Kathryn and Michael B. Panitch Career Development Award.
TRPV4 channels contribute to renal myogenic response in neonatal pigs
Authors: Soni Hitesh , Peixoto‐Neves Dieniffer , Adebiyi Adebowale
Published: November 2023

Myogenic response, a phenomenon in which resistance size arteries and arterioles swiftly constrict or dilate in response to acute elevation or reduction, respectively in intravascular pressure is a key component of renal blood flow (RBF) autoregulation mechanisms. Although it is well‐established that the renal system is functionally immature in newborns, renal autoregulation mechanisms in neonates remain poorly understood. In this study, we investigated the hypothesis that members of the transient receptor potential vanilloid (TRPV) channels are molecular components of myogenic response in newborns. We show that TRPV4 channels are predominantly expressed in neonatal pig preglomerular vascular smooth muscle cells (SMCs). Stretch‐induced intracellular Ca2+ ([Ca2+]i) elevation in distal interlobular artery SMCs and vasoconstriction were diminished by selective TRPV4 channel blocker HC‐067047. HC‐067047 also inhibited pressure‐induced membrane depolarization, [Ca2+]i elevation, and constriction in the microvessels. In anesthetized and mechanically ventilated neonatal pigs, step increases in arterial pressure up to 120 mmHg induced efficient autoregulation of RBF and cortical perfusion. Furthermore, intrarenal infusion of TRPV4 channel blockers HC‐067047 and RN‐1734 attenuated renal autoregulation in the pigs. These data suggest that renal myogenic autoregulation is functional in neonates. Our findings also indicate that TRPV4 channels are mechanosensors in neonatal pig preglomerular vascular SMCs, and contribute to renal myogenic autoregulation.

Support or Funding Information

NIH R01 DK101668
Characterization of pHi Regulation by NBCe1/SLC4A4 Variants with Known Clinical Phenotypes in Human Immortalized Trabecular Meshwork Cells with a Red‐Shifted Genetically‐Encoded pH‐Indicator “pHire”
Authors: Rossano Adam J , Caldas Font Paola N. , Holmes Heather L , Romero Michael F
Published: November 2023

The electrogenic Na+/HCO3− cotransporter (NBCe1/SLC4A4) maintains systemic acid/base balance by reabsorbing HCO3− in the renal proximal tubule but also contributes to intracellular pH (pHi) regulation in the eye, nervous system, pancreas, and intestine. Human recessive mutations lead to diverse phenotypes (glaucoma, proximal renal tubular acidosis, poor dentition) and mouse models suggest some organ manifestations are partially penetrant. The objective of this study was to develop a full spectrum genetically‐encoded live‐imaging toolkit which could be adapted to assay NBCe1‐mediated pHi regulation across a variety of cell types to further characterize how NBCe1 recessive mutations and polymorphisms functionally interact with each other and wild‐type (WT) NBCe1 to produce alterations in cellular acid/base physiology. WT human NBCe1 (WT‐NBCe1) and a recently characterized human recessive mutation (Mut‐NBCe1) were tagged with GFP. Each construct was co‐expressed via transfection in human immortalized trabecular meshwork cells (TM5) with “pHire”, a red‐shifted (556/630nm ex/em) pH‐sensitive variant of mApple, to assay NBCe1 function through real‐time quantification of pHi via widefield epifluorescent live‐imaging. pHire successfully reported pHi of TM5 cells in response to H+ loading with NH4Cl pulses. Calibration of pHire revealed an in vitro pKa of 7.44, a 5‐fold linear fluorescence response from pH 6.5 to 8.0, and stability following acid loads (pH 5.0) and long imaging protocols (30 min). pHi of TM5 cells fell in response to CO2/HCO3−— buffered solution and displayed a modest Na+‐dependent recovery (dpHi/dt = 0.02 ± 0.01 pH units min−1 in CO2/HCO3−, −0.06 ± 0.02 in Na+‐free), consistent with intrinsic TM5‐cell NBCe1 activity. Transfection of WT‐NBCe1 did not consistently alter HCO3− recovery but accelerated pHi decrease in Na+‐free solution by 10‐fold (1017 ± 3%) relative to neighboring untransfected cells. Transfection with E91R‐NBCe1 failed to similarly potentiate acidification upon Na+ withdrawal (117 ± 81%), and transfection with Mut‐NBCe1 suppressed Na+‐dependent acidification to 72 ± 28% of untransfected cells. These data suggest that although both Mut‐NBCe1 and E91R‐NBCe1 are functionally “transporter‐null” they possess different capacities to impair endogenous WT‐NBCe1, possibly through dimerization and localization deficits. Such differences could manifest discretely in specific cell types and may underlie the partial penetrance of some NBCe1‐associated phenotypes.

Support or Funding Information

Funding: T32‐DK007013 to AJR, DK092408, DK100227 and R25‐DK101405 to MFR.
Nominal Carbonic Anhydrase Activity Mitigates Airway‐Surface Liquid pH Changes During the Respiratory Cycle
Authors: Thornell Ian M , Li Xiaopeng , Tang Xiao Xiao , Zabner Joseph L , Welsh Michael J
Published: November 2023

The airway‐surface liquid pH (pHASL) is slightly acidic relative to the plasma pH and becomes more acidic in airway disease (e.g., cystic fibrosis, asthma, and COPD). Pathological pHASL may dysregulate ASL viscosity, mucociliary transport, and bacterial killing. Under constant 5% CO2, porcine large airways are more acidic (~7.0) than small airways (~7.4). However, the small airways are exposed to a constant 5% CO2, whereas the large airways are exposed to wide swings in pCO2 during respiration. Therefore, pHASL in the large airway may oscillate and be more alkaline during respiration. In this study, we investigated how oscillating CO2 affects the large airway pHASL for differentiated porcine tracheal epithelia cultured at the airway‐liquid interface. The apical surface of epithelia was initially exposed to 5% CO2. Apical CO2 was then rapidly switched to 0.04% CO2, allowed to equilibrate, and was then returned to 5% CO2. The pH was monitored by SNARF‐1 dextran fluorescence. Relative to a breath (~4 s), the time constant for pH changes were unexpectedly slow (τ = 51.9 ± 5.8 s, n = 12). We hypothesize that this slow time constant might be due to low carbonic anhydrase activity, which catalyzes the carbonic buffering reaction. Consistent with this hypothesis, the carbonic anhydrase inhibitor acetazolamide did not appreciably change the time constant (τ = 64.1 ± 6.1 s, n = 10; p = 0.21 vs. non‐treated). In contrast, adding exogenous carbonic anhydrase strikingly decreased the mean time constant (τ = 17.3 ± 3.1 s, n = 16; p < 0.01 vs. non‐treated). Curated mRNA microarray data indicated nominal expression for all extracellular and secreted carbonic anhydrase isoforms in large airway epithelia. To further understand how CO2 affects pHASL in the large airway, we modeled the pHASL during respiration using the pH‐dependent rates (dph/dt) obtained from our functional experiments. There were three major findings from our simulations. First, under physiological conditions (inspiratory:expiratory ratio = 1:2; respiration rate = 15 breathes per minute), the pHASL oscillations were small (peak‐to‐peak pHASL = 0.09 ± 0.02 pH units). In contrast, adding carbonic anhydrase increased the pHASL oscillations (peak‐to‐peak pHASL = 0.56 ± 0.16 pH units). Second, correcting the large airway steady‐state pHASL for the respiratory cycle still yields an acidic pHASL relative to the small airway (pHlarge 7.05 vs. pHsmall 7.45). Third, the inspiratory:expiratory ratio affected the average pHASL, whereas the respiration rate affected the magnitude of pHASL oscillations. Thus, minimal carbonic anhydrase activity in large airways prevents sizeable shifts in pHASL during respiration. Maintaining relatively constant pHASL may optimize airway host defense by antimicrobials and mucociliary transport.

Support or Funding Information

NIH HL091842, NIH HL5167, CF Foundation LI1410
Fungus‐Derived Zearalenone as an Inhibitor of cAMP‐Dependent Chloride Secretion in Human Colonic Epithelial T84 Cells
Authors: Muangnil Paradorn , Tadpetch Kwanruthai , Rukachaisirikul Vatcharin , Chatsudthipong Varanuj , Muanprasat Chatchai
Published: November 2023

Secretory diarrhea remains a major health problem caused by either intestinal infection or side‐effect of many drugs. An elevation in intracellular cAMP activates transepithelial Cl− secretion, which provides the driving force for secretory diarrhea. Therefore, inhibition of cAMP‐activated transepithelial Cl− secretion in intestinal mucosa is regarded as a potential therapeutic strategy for secretory diarrhea. This study aimed to identify fungus‐derived compounds that inhibit cAMP‐activated transepithelial Cl− secretion and investigate its underlying mechanism(s). From the screening of compounds derived from fungi, zearalenone (β‐resorcyclic acid lactone produced by Fusarium fungi) was found to inhibit cAMP‐activated Cl− secretion across human intestinal epithelial (T84) cell monolayers as measured by short‐circuit current (Isc) analysis with half maximal inhibitory concentration (IC50) of ~ 0.5 μM. This effect was observed only when zearalenone was added into apical side, but not basolateral side, suggesting that zearalenone affects mainly apical transport processes. We further demonstrated that zearalenone reversibly inhibited cystic fibrosis transmembrane conductance regulator (CFTR)‐mediated apical Cl− transport with IC50 ~ 0.8 μM, indicating that zearalenone inhibits cAMP‐acivated Cl− secretion in T84 cell, at least in part, by inhibiting CFTR Cl− channel activity. The mechanisms of zearalenone‐induced CFTR inhibition involved neither phosphodiesterase‐mediated cAMP degradation, multi‐drug resistance protein 4‐mediated cAMP efflux nor protein phosphatase‐mediated CFTR dephosphorylation. In addition, the CFTR inhibitory effect of zearalenone was not affected by co‐treatment with β‐estradiol, indicating that the CFTR inhibition by this compound did not result from its binding to estrogen binding site on the CFTR. Zearalenone at concentrations up to 50 μM did not produce the cytotoxic effect on T84 cells. This study revealed that zearalenone represents the first class of CFTR inhibitors derived from fungi, which may be useful in the treatment of secretory diarrhea resulting from overactivation of cAMP‐dependent chloride secretion.

Support or Funding Information

This work was supported by the NSTDA Chair Professor grant (the Fourth Grant) of the Crown Property Bureau Foundation and the National Science and Technology Development Agency and BRG5890008 grant from the Thailand Research Fund and Mahidol University
Curation of Renal Inner Medullary Collecting Duct Proteome Database with Sequence‐Based Searching Using K‐BLAST
Authors: Medvar Barbara , Pisitkun Trairak , Sarkar Abhijit , Knepper Mark
Published: November 2023

The renal collecting duct regulates water excretion through the action of vasopressin to regulate the water channels aquaporin‐2 (AQP2) and AQP3. A long‐term goal is to understand the mechanisms involved in collecting duct function and regulation at a cellular and molecular level. Ancillary to laboratory‐based investigations, mathematical modeling of the cellular mechanisms can provide a guide to experimentation and curation of information. The first step in modeling is the generation of a list of model components. For collecting duct modeling we have now curated a list of proteins expressed in the rat renal inner medullary collecting duct from proteomic data from 18 different publications. The database has been posted as a public resource at https://hpcwebapps.cit.nih.gov/ESBL/Database/IMCD_Proteome_Database/. It includes proteins corresponding to 8,959 different genes. To search the IMCD Proteomic Database efficiently we have created a Java‐based program called K‐BLAST, which uses the NCBI BLAST kernel to search for specific amino acid sequences corresponding to proteins in the database. K‐BLAST reports information on the matched protein and identifies proteins in the database that have similar sequences. We have also adapted K‐BLAST to interrogate our previously published IMCD Transcriptome Database. We have made the K‐BLAST program available for use either as a web application or a downloadable .jar file at https://hpcwebapps.cit.nih.gov/ESBL/Database/K‐BLAST/. Database searching based on protein sequence removes ambiguities arising from the standard search method based on official gene symbols and allows the user efficient identification of related proteins that may fulfill the same functional roles.

Support or Funding Information

NIH ZIA‐HL006129
Blast Exposure with mTBI is associated with Impaired Cerebral Blood Flow in US Veterans
Authors: Serrador Jorge Manuel , Haber Yaa , Brewer Kelly , De La Cruz Leslie , Falvo Michael
Published: November 2023

Blast exposure is a significant problem for the current and recent military conflicts, however, data remains limited on the effects of a pressure wave on autonomic and cerebral blood flow regulation. The goal of this work was to determine if veterans with a blast exposure and/or mild traumatic brain injury (mTBI) demonstrate impaired cerebral blood flow regulation.

Thirty veterans (2 females, 44.8 ± 13.7 years) participated. Nine were controls with no history of blast or mTBI, four had blast exposure with mTBI, five had blast with mTBI and 11 had history of mTBI without blast exposure. One subject was excluded because they had a moderate TBI. To assess cerebral blood flow regulation we monitored TCD in both the anterior (ACA) and middle cerebral arteries (MCA) during three sit to stand maneuvers. We also measured beat by beat blood pressure and end tidal CO2 via nasal cannula. Veterans with a history of Blast+mTBI had significantly higher mean arterial pressure (100±13 mmHg) than either mTBI (87±13 mmHg), Blast only (84±13 mmHg) or controls (84±13 mmHg). Cerebral flow velocity while standing was significantly reduced in the Blast+mTBI group (MCA: 87±9%; ACA: 87±9% of seated baseline) compared to mTBI group (MCA: 94±9%; ACA: 98±10%) or Blast only group (MCA: 103±9%; ACA: 99±9%) or Controls (MCA: 99±9%; ACA: 101±10%). In contrast, autoregulatory index was not significantly different between groups in the MCA or ACA. End tidal CO2 was also not different between the groups when standing.

These data indicate that veterans who had a blast exposure and a head injury had higher blood pressures and lower cerebral flow velocity when standing, even when compared to those with a head injury not due to blast, or those that were exposed to a blast but did not receive a head injury. These data suggest that blast waves that have sufficient energy to cause a head injury result in more significant impairment of cerebral blood flow when standing than those with an impact mTBI not associated with a blast wave. This may contribute to some of the persistent symptoms these Veterans report after returning. Future work needs to verify these findings in a larger group of Veterans.

Support or Funding Information

Supported by the War Related Illness & Injury Study Center, Veterans Administration and NIH grant R21DC009900 (Serrador).
Factors Predictive of Human One‐Kilometer Ice Swimming Race Time Performance
Authors: Wulf Cailey A , Treu Spencer P , Wilson Ted
Published: November 2023

Ice swimming is a popular sport under consideration as a possible Winter Olympic Event. Swimming in water that is ≤5°C brings inherent risks such as hypothermia and factors that influence swimming performance are poorly understood in this regard. This study evaluated International Ice Swimming Association data for one‐kilometer ice swimming performance that included swimmer age, sex (144 male; 75 female), height/weight for body mass index (BMI) calculation, swim time, swim stroke, and swim conditions for 177 swimmers who (without wetsuits) performed 219 different ice swimming races on 9 different times and locations (December 19, 2015–August 10, 2016). Swimmers using the crawl stroke required 19.38 ± 0.27 minutes for these one‐kilometer swims. Four factors were highly predictive of swim time. Age is most predictive, air temperature and gender are moderately predictive, and BMI is least predictive. As age increases, swim time gets significantly slower. Warmer air temperature was surprisingly associated with slower swim time. Males were faster than females. In many sports decreased BMI is predictive of improved fitness, however increased BMI is also associated with improved thermal conservation, a factor that could be important for ice swimming. A BMI of 20 was the absolute lower observed limit for ability to complete these one‐kilometer swims, increasing BMI was associated with increases in race time, and gender specific BMI differences were not statistically significant. When swimmers completed more than one race, the second swim was significantly faster than the first. Water temperature did not significantly impact swim times. The physiology of cold‐water exposure can be applied to athletes, survival situations, the military, and the medical field. This study provides data that increases the understanding of the human body's physiological reaction when exposed to cold conditions, specifically in water, and provides a framework that allows for the prediction of ice water swim times.
Effects of Resting Muscle Carnosine Content on the Intramuscular Antioxidant Response to a Bout of Resistance Exercise
Authors: Varanoske Alyssa N , Hoffman Jay R , Church David D , Jajtner Adam R , Townsend Jeremy R , Beyer Kyle S , Oliveira Leonardo P , Fukuda David H , Stout Jeffrey R
Published: November 2023

INTRODUCTION

Acute bouts of resistance exercise can result in elevations in oxidative stress. Carnosine (CARN) is a histidine dipeptide that has been suggested to have antioxidant properties, and as a result may enhance the recovery processes following exercise. However, there appears to be only limited data that has examined the effect of resting muscle CARN content on its role as an antioxidant or reducing oxidative stress following an acute bout of resistance exercise. The purpose of this study was to compare the effects of high (HI) and low (LO) resting muscle CARN on antioxidant status. A secondary purpose was to compare the intramuscular oxidative stress response following an acute bout of resistance exercise between individuals with HI and LO CARN values.

METHODS

Fifteen recreationally‐active men volunteered for this study. Muscle biopsies were sampled from the vastus lateralis of the left leg at baseline (BL). A subset of these participants (n=12) then completed an acute muscle‐damaging protocol consisting of the squat (6 sets × 10 repetitions), leg press (4 sets × 10 repetitions) and leg extension (4 sets × 10 repetitions) exercises at 70% of their 1‐repetition maximum. Additional muscle biopsies were sampled at one (1H), five (5H), and 24 (24H) hours post‐exercise. Intramuscular CARN content from biopsy samples was determined via high‐performance liquid chromatography, whereas glutathione (GSH), catalase (CAT), peroxiredoxin 2 (PRX2), superoxide dismutase 1 (SOD1), superoxide dismutase 2 (SOD2), and thioredoxin 1 (TRX1) were quantified via enzyme‐linked immunosorbent assays. Participants were categorized into HI (n=7; 21.7±2.9 y; CARN: 14.8±4.2 mmol·kg−1 ww) and LO (n=8; 21.8±2.5 y; CARN: 6.4±2.3 mmol·kg−1 ww) groups by their BL CARN levels. Magnitude‐based inferences were used to analyze group differences and change scores in antioxidant concentrations at BL and after exercise.

RESULTS

Subjects with HI CARN had “Likely” greater GSH at BL compared to those with LO CARN (11.50±2.71 μM vs. 8.75±3.75 μM, respectively). In individuals who completed the resistance exercise protocol, GSH values at 1H were “Likely” greater in individuals with HI CARN compared to those with LO CARN. Decreases in CAT, PRX2, SOD1, and TRX1 from BL to 24H were all “Likely” greater in individuals with HI CARN compared to those with LO CARN. Furthermore, changes in SOD2 from BL to 1H, BL to 5H, and BL to 24H were “Very Likely”, “Likely”, and “Very Likely” lower in individuals with HI CARN compared to those with LO CARN, respectively.

DISCUSSION

In conclusion, individuals with HI CARN at BL appear to exhibit a differential antioxidant recovery response to resistance exercise compared to individuals with LO CARN.
Effects of the Different Acute Exercise on Serum Cortisol of Undergraduate
Authors: He Jing , Sun Ping You , Qiu Li Lin
Published: November 2023

OBJECTIVE

To compare the effects of different acute exercise on Serum Cortisol of undergraduate.

METHODS

Subjects (n=160)were randomized into endurance training(E, n=40), strength training (S, n=40), combined strength and endurance training(SE, n=40), or control group(C, n=40)for 45min, and take 4ml venous blood at before and after training.

RESULTS

1、 The Serum Cortisol of female significantly increased in E (438.90±60.48 651.10±138.45; P < 0.01). Serum Cortisol significantly increased in S (436.52±72.68; 690.64±92.06; P < 0.01), Serum Cortisol significantly increased in SE (416.09±8.49; 752.90±135.79; P < 0.01). and it increased significantly in C also (427.90±56.72; 679.37±177.95; P < 0.05). 2、 The Serum Cortisol of male significantly increased in E (394.31±685.73; 733.23±97.82; P < 0.01). Serum Cortisol significantly increased in S (353.04±131.08; 698.18±103.07; P < 0.05), Serum Cortisol significantly increased in SE (440.14±65.60; 761.18±108.29; P < 0.01), but it increased no significantly in C (424.95±98.24; 552.01±208.12; P > 0.05). 3、 The change of the Serum Cortisol of E、 S、 SE and C exist significant difference (female: P < 0.01; male: P < 0.05).

CONCLUSION

Endurance training and Strength training and their combination all led to increase in Serum Cortisol. The different acute exercises have difference influence on Serum Cortisol, and the influence of combined training on serum cortisol is the largest.

Support or Funding Information

The key lab of adolescent health intervention and exercise assessment, Ministry of China,
Inter‐individual Variability in Muscle Sympathetic Nerve Activity during Static Handgrip in Healthy Young Men
Authors: Incognito Anthony V. , Doherty Connor J. , Lee Jordon B. , Burns Matthew J. , Millar Philip J.
Published: November 2023

Cardiovascular responses at the onset of static handgrip are thought to be governed primarily by activation of higher brain regions (central command) and stretch‐sensitive group III/IV skeletal muscle afferents (muscle mechanoreflex), whereas responses during more prolonged contractions also involve activation of chemically‐sensitive group III/IV afferents (muscle metaboreflex). However, the contribution of central command to the muscle sympathetic nerve activity (MSNA) response at exercise onset is unclear. Existing evidence suggests that central stressors (e.g. mental stress) can either increase or decrease MSNA, identifying two populations of responders. We hypothesized that considerable inter‐individual variability may exist also at the onset of static handgrip, when the net contribution of central command is greatest. Continuous supine measurements of multi‐unit MSNA (microneurography) and blood pressure (Finometer) were recorded in 28 healthy men (24±5 years) during 2 minutes of static handgrip (30% maximal voluntary contraction) and 3 minutes of post‐exercise circulatory occlusion (PECO). Participants were divided into high (n=14) and low (n=14) MSNA responders based on the median MSNA burst frequency response during the first minute of static handgrip. High responders demonstrated greater MSNA responses during the first (Δ6±5 vs. −3±3 bursts/min, p<0.001) and second (Δ13±5 vs. 5±6 bursts/min, p<0.001) minute of handgrip and during the last minute of PECO (Δ9±7 vs. 4±6 bursts/min, p<0.05) compared to low responders. However, the change in MSNA between the first and second minute of handgrip was similar between high and low responders (Δ6±7 vs. 7±4 bursts/min, p>0.05). The increases in mean arterial pressure during handgrip (minute one: Δ9±6 vs. 7±4 mmHg; minute two: Δ20±9 vs. 16±9 mmHg) and PECO (Δ15±9 vs. 12±8 mmHg) were similar between high and low responders (All p>0.05), as were changes in heart rate, stroke volume, cardiac output, and total vascular conductance (All p>0.05). Examining the individual data as a continuous variable, the changes in MSNA and mean arterial pressure were unrelated during the first minute of handgrip (r=0.04, p>0.05), but related positively during the second minute of handgrip (r=0.50, p<0.01) and last minute of PECO (r=0.50, p<0.01). In summary, MSNA responses at the onset of static handgrip in young healthy men are highly variable and exhibit a dissociation with the pressor response.

Support or Funding Information

This research was supported by a Natural Science and Engineering Research Council (NSERC) of Canada Discovery Grant (P.J.M), the Canada Foundation for Innovation (P.J.M.), University of Guelph‐Humber Research Grant (P.J.M), and a Canadian Institutes of Health Research Fredrick Banting and Charles Best Canada Graduate Scholarship (A.V.I.).
Hypoxic response in skeletal muscle contributes to the adaptation of muscle fibers in mice
Authors: Nunomiya Aki , Shin Junchul , Kitajima Yasuo , Dan Takashi , Miyata Toshio , Suzuki Naoki , Aoki Masashi , Nagatomi Ryoichi
Published: November 2023

Background

Previously, we reported that activation of the hypoxia‐inducible factor pathway induced by prolyl hydroxylase domain 2 (PHD2) deficiency enhances the effect of running training in mice (Nunomiya et al., 2016). We also reported that muscle cross sectional area (CSA) of Phd2‐deficient mice was significantly smaller compared to that of control mice (Shin et al., 2016). Decreased cross sectional area of muscle fibers may favor oxygen delivery during training. It is unknown, whether the observed adaptations in skeletal muscle is due to the systemic‐ or local hypoxic response within the skeletal muscle fibers. We hypothesized that the hypoxic adaptation of skeletal muscle is independent of systemic hypoxic adaptation. The aim of this study is to determine whether systemic‐or local hypoxic response affected the muscle fiber size.

Methods

Two independent lines of Phd2‐floxed mice were used in this study; global Phd2 knockout mice (conditional knockout: cKO) and skeletal muscle specific Phd2 knockout mice (muscle specific knockout: MuKO). Because global Phd2 knockout is embryonic lethal, estrogen receptor (ER) agonist‐induced Phd2 conditional KO mouse using Cre‐loxP system was generated. To delete floxed Phd2 exon 2, tamoxifen was administrated to Phd2 cKO mice by i.p. injection.

Results

As we reported previously, we detected the reduced CSA in the gastrocnemius muscle of Phd2 cKO mice. Additionally, soleus CSA in Phd2 cKO mice was also reduced in Phd2 cKO. These results suggest that the reduction of CSA was induced not only in type 2b fiber, but also in type 2a and type 1 fiber. Moreover, soleus CSA was decreased in Phd2 MuKO mice compared with control mice. These data suggest that the reduction of muscle CSA may depend on local hypoxic response in skeletal muscle fiber rather than systemic hypoxic response.

Conclusions

Our data suggest that hypoxic response in skeletal muscle fiber induced by Phd2 deficiency resulted in smaller skeletal muscle fiber size in all fiber types.

Support or Funding Information

This work was supported by a JSPS Grant‐in‐Aid for JSPS fellows (26‐3209).
Acute Hypoxia Decreases Systemic Blood Pressure at Exercise in Hypertensive and Normotensive Subjects
Authors: Richalet Jean‐Paul , Winkler Laurent , Lhuissier François J
Published: November 2023

This study aimed to determine whether acute hypoxia associated with exercise induces an increase in systemic blood pressure (SBP) in normotensive and hypertensive subjects, and whether hypertensive subjects are more prone to develop Severe High Altitude Illnesses (SHAI). Finally, to determine if SBP and ECG changes at exercise in hypoxia in hypertensive subjects are predictive factors for SHAI. From 2012 to 2015, 1113 sea‐level natives went through a hypoxia exercise test before a sojourn at high altitude, allowing the calculation of a SHAI prediction score. A total of 958 subjects were enrolled in the study, including 106 hypertensive subjects. From 272 subjects who sent back a questionnaire evaluating their tolerance to high altitude, 52 suffered from SHAI. When compared to normoxia, for the same heart rate, acute hypoxia induced a decrease in SBP at exercise in normotensive and hypertensive subjects. Hypertensive subjects treated by beta‐blockers showed a lower arterial oxygen saturation (vs other treatments) and blunted cardiac and ventilatory responses to hypoxia at exercise. Hypertensive subjects were not more prone than normotensive subjects to develop SHAI. Hypertensive subjects suffering from SHAI although taking acetazolamide showed similar SBP and ECG characteristics than hypertensive subjects without SHAI and without acetazolamide. In conclusion, hypoxia induces a peripheral vasodilation that balances vasoconstriction and tachycardia centrally induced through the adrenergic system. Hypertensive and normotensive subjects behave similarly during exercise in acute hypoxia. Hypoxia does not exacerbate the exercise‐induced increase in SBP. Systemic arterial pressure is not a useful predictor of intolerance to high altitude.
Nitrite Infusion Does Not Alter Isolated Canine Muscle Oxidative Metabolism In Situ During Hypoxia With Normal Convective O2 Delivery
Authors: Porcelli Simone , Rasica Letizia , Ferguson Brian S. , Kavazis Andreas N. , McDonald James R. , Mowry Francesca , Hogan Michael C. , Grassi Bruno , Gladden Bruce L.
Published: November 2023

Introduction

Previous studies have shown a decreased muscle oxygen consumption (V′O2) during moderate intensity exercise in hypoxia after augmented nitric oxide (NO) bioavailability, which suggests an increased efficiency of oxidative metabolism. It is not clear if these effects are related to an NO‐induced increase in convective O2 delivery and/or to an enhanced mitochondrial coupling efficiency. The aim of this study was to examine skeletal muscle contraction economy during hypoxic exercise following nitrite infusion with unchanged convective O2 delivery.

Methods

Canine gastrocnemius muscles (n=8) were surgically isolated and electrically stimulated via the sciatic nerve, eliciting 1 contraction every 3 seconds (≈35% V′O2peak) for 3 minutes in hypoxic conditions (PaO2=42±3 mmHg). During contractions, sodium nitrite (NITR) or sodium chloride (SAL) was infused into the popliteal artery. Muscle blood flow was kept constant by a perfusion pump. Muscle force was measured and muscle V′O2 was calculated from the Fick principle. Muscle biopsies were obtained before and after NITR and were used to isolate mitochondria. Mitochondrial respiration rates were recorded by high‐resolution respirometry.

Results

Muscle V′O2 was not significantly different between NITR (60.6±18.0 ml/kg/min) and SAL (61.7±18.3ml/kg/min). After normalizing V′O2 per unit of developed force, the values were slightly but not significantly higher in NITR vs. SAL (p=0.10). No differences were found for ADP‐stimulated mitochondrial respiration (both for complex I and complex II), leak respiration and oxidative phosphorylation coupling.

Conclusion

In hypoxic conditions, but in the presence of constant and normal convective O2 delivery, nitrite infusion did not affect canine skeletal muscle oxidative metabolism. These results suggest that the effects of increased NO availability on muscle contraction efficiency in hypoxia, if present, are likely not attributable to changes in mitochondrial respiratory function.
Active Shortening Protects Against Stretch‐Induced Force Deficits in Human Skeletal Muscle
Authors: Saripalli Anjali L. , Sugg Kristoffer B. , Mendias Christopher L. , Brooks Susan V. , Claflin Dennis R.
Published: November 2023

Skeletal muscle contraction results from molecular interactions of myosin “crossbridges” with adjacent actin filament binding sites. The binding of myosin to actin can be “weak” or “strong”, and only strong binding states contribute to force production. During active shortening, the number of strongly‐bound crossbridges declines with increasing shortening velocity. Forcibly stretching a muscle that is actively shortening at high velocity results in no apparent negative consequences whereas stretch of an isometrically (fixed‐length) contracting muscle causes ultrastructural damage and a decline in force‐generating capability. Our working hypothesis is that stretch‐induced damage is uniquely attributable to the population of crossbridges that are strongly‐bound. We tested the hypothesis that stretch‐induced force deficits decline as the prevailing shortening velocity is increased. Experiments were performed on permeabilized segments of individual skeletal muscle fibers obtained from human subjects. Fibers were maximally activated and either allowed to generate maximum isometric force (Fo), or to shorten at velocities that resulted in force maintenance of ≈50% Fo or ≈2% Fo. For each test condition, a rapid stretch equivalent to 0.1 × optimal fiber length was applied. Relative to pre‐stretch Fo, force deficits resulting from stretches applied during force maintenance of 100%, ≈50%, and ≈2% Fo were 23.2 ± 8.6%, 7.8 ± 4.2% and 0.3 ± 3.3%, respectively (mean ± SD, n=20). We conclude that stretch‐induced damage declines with increasing shortening velocity, in support of the possibility that the fraction of strongly‐bound crossbridges is a causative factor in the susceptibility of skeletal muscle to stretch‐induced damage.

Support or Funding Information

NIH R01‐AG050676, R01‐AR063649, F32‐AR067086
Human Skeletal Muscle Proteins and Metabolic Pathways are Susceptible to Dicarbonyl Stress
Authors: Mey Jacob T , Haus Jacob M
Published: November 2023

INTRODUCTION

Individuals with Type 2 Diabetes Mellitus (T2DM) present with hyperglycemia concomitant with increased generation of methylglyoxal (MG), a highly reactive dicarbonyl and glycolytic intermediate. MG modifies proteins at arginine residues creating the advanced glycation endproduct methylglyoxal‐derived hydroimidazolone (MG‐H1). Accumulation of MG‐modified proteins has been referred to as dicarbonyl stress and has been implicated in the etiology of T2DM and development of future complications. The mechanisms and tissue specificity underlying MG‐directed protein modifications are largely unknown, but MG has been hypothesized to target the regulatory gamma subunit of AMPK (AMPKγ), due to exposed arginine residues within the AMPKγ catalytic site.

PURPOSE

Therefore, the purpose of this study was to investigate the effects of hyperglycemia or exogenous MG treatment on the formation of total MG‐modified proteins and specific AMPKγ protein modifications in primary human skeletal muscle cells (HSKMCs). Skeletal muscle tissue was selected given the paucity of evidence and the importance to whole body glucose metabolism.

METHODS

HSKMCs were incubated in euglycemic (5.5mM glucose) or hyperglycemic (30mM glucose) media and total MG‐directed protein modifications were assessed at 24 hrs and 5 days in cell lysates via immunoblotting of MG‐H1 residues. Specific MG‐modifications of AMPKγ were assessed by incubating HSKMCs in MG‐supplemented media (0, 5, 50, 100, or 500μM MG) for 4 hours after which AMPKγ was immunoprecipitated and immunoblotted for MG‐H1 residues. We also examined the effects of MG treatment on AMPK activity, with and without AICAR stimulation (2mM), as assessed by the expression of phosphorylated acetyl coa carboxylase β (pACCβ), a commonly used surrogate marker for AMPK activity in skeletal muscle.

RESULTS

Hyperglycemia showed no effect on total MG‐modified proteins at 24 hrs (p>0.05), but increased MG‐modified proteins by 50±18% (p<0.035) at 5 days. Experimental MG treatment did not increase MG‐modifications of AMPKγ at any MG concentration. However, ACCβ phosphorylation increased in stepwise fashion with increasing MG concentrations, becoming significant at 10μM (141±4%, p=0.0066), 50 μM (202±9%, p=0.0007) and peaking at 100μM (342±27%, p=0.0010). Interestingly, pre‐incubating HSKMCs with low dose MG (10μM) was additive to AICAR stimulated AMPK activity as the combination increased pACCβ expression by 24±4% compared to AICAR alone (p=0.011). However, pre‐incubating cells with MG at high doses showed no additional effect or abolished pACC expression (500μM, no different from Control).

CONCLUSION

These data suggest that hyperglycemia increases dicarbonyl stress in HSKMCs and that exogenous MG treatment augments AMPK activity in the absence of AMPKγ specific MG‐modifications. The biphasic response in AMPK activity in response to exogenous MG requires further investigation.
Development of a chronic irradiation and simulated microgravity facility
Authors: Chowdhury Parimal , Griffin Robert J. , Narayanasamy Ganesh , Pathak Rupak , Hauer‐Jensen Martin , Boerma Marjan , Dobretsov Maxim
Published: November 2023

Chronic irradiation (IR) and microgravity (MG) are associated with multiple physiological, cellular, molecular, and genetic alterations and thus it is a risk factor during long term human space exploration missions. However, studies on the combined effects of chronic IR and MG on biological systems are largely unknown, because of lack of appropriate facilities. Ground based studies on in‐vivo or/in‐vitro models of simulated MG (SMG) have targeted studies on acute exposure to IR (and usually at relatively high doses). In contrast, relatively few studies with hind‐limb suspended rodents (model of SMG) studies were conducted at various time points following a single or repetitive exposure to IR. The effects of chronic low dose IR administered under conditions of SMG or without are even less studied. Thus in order to study the effects of chronic SMG and IR administered either in combination or in isolation we have planned to build a facility capable of delivering both stresses to small animals. Our approach calls for immediate need of developing facilities in which space flight conditions (SMG and continuous low grade IR with occasional bursts of IR (solar sparks) can be mimicked with a reasonable reliability. Here we discuss the minimal requirements for such facility and provide further arguments showing that without such facility we will unlikely be able to address the question about combined and dissociated effects of IR and MG on human health. Furthermore, having the facility will allow enhanced development of targeted countermeasures diminishing the deteriorating effects of prolonged space flight on human crew health and operational capacity.

Support or Funding Information

Arkansas Space Grant Consortium
Similar Effects of Type 1 Diabetes on the Pressor Reflex in Male and Female Rats
Authors: Grotle Ann‐Katrin , Garcia Elizabeth A. , Stone Audrey J
Published: November 2023

Type 1 diabetes (T1DM) pathophysiology and prevalence differ in males as do the mechanisms of cardiovascular related diseases. The purpose of this study was to establish whether the pressor and cardioaccelerator responses evoked by static contraction or tendon stretch differ by sex in T1DM rats. We injected (i.p) 50 mg/kg of Streptozotocin (STZ) or the vehicle (CTL) i.p. in either sex and waited 1wk (female CTL: BW=267±5 g, glucose=195±10 mg/dl, HbA1C=4.5±0.8%; male CTL: BW=360±12 g, glucose=361±12 mg/dl, HbA1C=4.4±0.1%; female STZ: BW=254±12 g, glucose=495±29 mg/dl, HbA1C=6.3±0.2%; male STZ: BW=273±16 g, glucose=408±29 mg/dl, HbA1C=6.5±0.5%;) or 3wks (female CTL: BW=286±6 g, glucose=177±28 mg/dl, HbA1C=4.3±0.1%; %; male CTL: BW=427± g, glucose=238±36 mg/dl, HbA1C=5.1±0.7%; female STZ: BW=274±15 g, glucose=503±37 mg/dl, HbA1C=9.2±0.6%; male STZ: BW=306±11 g, glucose=436±26 mg/dl, HbA1C=10.7±0.2) before performing experiments. In unanaesthetized, decerebrate rats, we statically contracted the hindlimb muscles or stretched the Achilles tendon for 30s and measured changes in mean arterial pressure (MAP) and heart rate (HR). We found that the pressor (female CTL: ΔMAP=19±12 mmHg, n=4; male CTL: ΔMAP=21±4 mmHg, n=5; female STZ: ΔMAP=50±18 mmHg, n=3; male STZ: ΔMAP=49±12 mmHg, n=3, p=0.99) and cardioaccelerator (female CTL: ΔHR=8±2 bpm, n=4; male CTL ΔHR=10±3 bpm, n=5; female STZ: ΔHR=10±1 bpm, n=3; male STZ: ΔHR=23±5.1 bpm n=3, p=0.25) responses to tendon stretch were not significantly different between sexes 1wk after STZ injection. Likewise, the pressor (female CTL: ΔMAP=15±2 mmHg, n=6; male CTL: ΔMAP=23±5 mmHg, n=3; female STZ: ΔMAP=35±8 mmHg, n=5; male STZ: ΔMAP=27±5 mmHg, n=3, p=0.18) and cardioaccelerator (female CTL: ΔHR=16±2 bpm, n=6; male CTL: ΔHR=12±6 bpm, n=3; female STZ: ΔHR=16±8 bpm, n=6; male STZ: ΔHR=27±10 bpm, n=3, p=0.25) responses to static contraction were not different between sexes 3wks after STZ injection. Furthermore, the pressor (female CTL: ΔMAP=21±4 mmHg, n=5; male CTL: ΔMAP=55±4 mmHg, n=3; female STZ: ΔMAP=30±11 mmHg, n=5; male STZ: ΔMAP=30±11 mmHg, n=6, p=0.45) and cardioaccelerator (female CTL: ΔHR=9±3 bpm, n=5; male CTL: ΔHR=17±3 bpm, n=3; female STZ: ΔHR=14±8 bpm, n=5; male STZ: ΔHR=12±3 bpm, n=6, p=0.3) responses to tendon stretch were not significantly different between sexes 3wks after STZ injection. The developed tensions from contraction or tendon stretch were similar within each comparison. We conclude that the pressor and cardioaccelerator responses to tendon stretch and static contraction are not different between male and female rats in either the beginning or later stage of T1DM.