bluuebunny/crossref_metadata_2025 huggingface dataset:
Endurance Exercise and Selective Breeding for Longevity Extend Drosophila Healthspan by Overlapping Mechanisms
Authors: Sujkowski Alyson , Bazzell Brian , Carpenter Kylie , Arking Robert , Wessells Robert
Published: June 2021

Endurance exercise has emerged as a powerful intervention to extend healthy physiology into advanced age. Normal, age‐associated declines in organ structure and function are alleviated in endurance‐trained individuals. Long‐term exercise also reduces age‐related pathologies. Despite these evident benefits, the genetic pathways required for exercise interventions to achieve these effects are still relatively poorly understood. Here, we compare the effects of endurance training on Drosophila melanogaster to the effects of selective breeding for longevity. We find that both selective breeding and endurance training increase endurance, cardiac performance, running speed, flying height, and levels of autophagy in adipose tissue. Microarrays indicate that 73% of transcriptional changes found in flies selectively bred for longevity are also found in flies subjected to three weeks of exercise training. Both endurance training and longevity selection upregulate folate biosynthesis, stress defense and lipid metabolism. Conversely, both interventions downregulate multiple carbohydrate metabolism pathways. methuselah‐like 3 was also transcriptionally reduced in both groups. Altering mthl3 expression in adult flies was able to reproduce a subset of the shared phenotypes. These results provide support for endurance exercise as a broadly acting anti‐aging intervention and confirm that exercise training acts in part by targeting longevity assurance pathways. In addition, these results identify the mthl3 gene as a potential target of exercise training.
AVP‐mediated regulation of the paracellular permeability in the thick ascending limb (TAL)
Authors: Plain Allein , Marques Rita , Himmerkus Nina , Leipziger Jens , Bleich Markus
Published: June 2021

The TAL drives an important part of the reabsorption of divalent cations. This occurs through the cation selective paracellular pathway. Arginine vasopressin (AVP) stimulates the transepithelial transport in the TAL. We wanted to study how AVP stimulation affects paracellular permeability in the TAL.

TALs were mechanically dissected for microperfusion from 8‐10 weeks old mice who were kept for 4 days on water‐restricted (WR) (0.26ml/gBM/d) or water‐loaded (WL) (0.78ml/gBM/d) conditions, and from 5‐10 week old mice to be stimulated acutely with AVP.

We measured transepithelial resistance and voltage (Rte, Vte), and calculated the equivalent short circuit current (Isc). From diffusion voltages, in presence of furosemide, we calculated the paracellular permeability (P) for Na+, Cl‐, Mg2+ and Ca2+. Measurements were performed at 37°C with continuous perfusion at a constant pressure.

Freshly isolated TAL from the WR group (n=20) were transporting more actively compared to the WL group tubules (n=15). Vte and Isc were a 26% and a 48% higher, respectively, while Rte was 27% lower. Diffusion voltages were also increased in the WR group by 21%, indicating a 30% higher PNa/Cl, and a 27% higher PNa compared to WL.

Acute TAL stimulation ex‐vivo for 12 minutes with AVP (n=6), in paired experiments, increased transepithelial transport. Isc and Vte increased by 23% and 25% respectively, while in the time control group Isc and Vte decreased by 28% and 37%. At the same time, AVP induced 20% more pronounced diffusion voltages compared to control, with a 25% increase in PNa/PCl.

Conclusion

Water restriction and AVP increase paracellular selectivity and permeability for cations in the TAL.
Claudin‐2 Null Mice Reveal Increased Renal Transcellular Na Transport And Kidney Oxygen Consumption
Authors: Pei Lei , Solis Glenn , Welch William , Nguyen Mien , Kamat Nikhil , McDonough Alicia , Yu Alan , Magenheimer Lynn
Published: June 2021

60% of filtered Na is reabsorbed in renal proximal tubules (PT), 40% of which is transported paracellularly. Claudins are a family of tight junction transmembrane proteins that regulate paracellular permeability. Cation‐selective claudin‐2(cldn2) is expressed in PT. Cldn2 knockout (KO) mice were reported to have markedly decreased PT cation permeability but no Na wasting on regular diet. To evaluate the role of cldn2 in renal salt handling, we placed wild‐type (WT) and cldn2 knockout (KO) mice on a Na deficient diet, and urine was collected every 8 hours. The cldn2 KO mice were able to conserve Na to the same extent as their WT littermates. Quantitative RT‐PCR did not reveal compensatory upregulation of other claudin isoforms. The natriuretic response to the NKCC2 inhibitor, furosemide (25mg/kg ip), was 25% higher in KO compared to WT (P<0.05). Thus, loss of PT Na transport was compensated distally, primarily by a functional increase in transcellular Natransport in the thick ascending limb. We hypothesized that the increased transcellular transport would lead to increased renal oxygen consumption. To test this, we determined the ratio between whole kidney Na reabsorption (TNa) and oxygen consumption (QO2 = RBF X A‐VO2) in WT and KO mice. Cldn2 null mice exhibited lower TNa/QO2 (WT: 7.26±0.66 vs KO: 4.96±0.77 µmol/µmol). In conclusion, our findings suggest that in cldn2 KO mice, loss of PT paracellular Na transport is compensated by increased Na reabsorption by distal transcellular transporters at the expense of decreasing kidney oxygen utilization efficiency.
A Common Signal Patch Drives AP‐1 Dependent‐Golgi Export of the Basolateral Kir Channels in the Distal Nephron
Authors: Li Xiangming , Welling Paul
Published: June 2021

Polarized distribution of inward rectifying K+ (Kir) channels in the distal nephron is essential for K+ excretion. Here we explore a new polarized trafficking mechanism, focusing on a Golgi trafficking step, which couples Apical/Basolateral membrane (BLM) cargo selection and clathrin‐coated vesicle (CCV) formation to Golgi export. Our previous work on the prototypical Kir channel, Kir2.1, identified a novel signal patch embedded within its tertiary structure that forms a recognition site for AP1A clathrin adaptor, marking channels for inclusion into CCVs at the trans‐Golgi network (Ma et al Cell, 2011). Here we test if the Golgi export patch is conserved in the basolateral Kir channels for polarized trafficking to the BLM. We focused on Kir 4.1, mutations in which underlie EAST/SeSAME syndrome, and Kir2.3, because they both contribute to the basolateral K+ conductance in the distal convoluted tubule, the connecting tubule and the collecting duct. Sequence analysis and atomic resolution modeling revealed both channels share common residues with the Golgi export patch in Kir 2.1, pointing to a common “SY” motif. Kir4.1 and Kir2.3 channels bearing ΔSY mutations lost cell surface expression. These mutant channels largely colocalized with the cis‐ and trans‐ Golgi markers, which suggest ΔSY mutations block channel forward trafficking at the Golgi apparatus. siRNA mediated ablation of γ subunit of AP‐1 clathrin adaptor, caused a significant reduction of the cell surface expression of WT Kir channels, paralleled by channel accumulation in the Golgi. Overall, these data suggest basolateral Kir channels in the distal nephron rely on a common AP‐1 dependent Golgi export patch to gain access to the cell surface.
UROTHELIAL EPAC: NOVEL MEDIATOR IN THE REGULATION OF BLADDER CAPACITY
Authors: Nakagomi Hiroshi , Kullmann F Aura , Ruiz Wily , Wolf‐Johnston Amanda , Apodaca Gerard , Birder Lori
Published: June 2021

Bladder filling elicits exocytosis and vesicle fusion increasing the apical surface area of epithelial cells (measured by membrane capacitance). One stimulus governing apical exocytosis is cAMP. Although initially the effects of cAMP were solely attributed to activation of protein kinase A (PKA), recent findings uncovered a novel c‐AMP sensor, EPAC (exchange protein directly activated by cAMP). This protein plays a critical role in calcium handling and ion transport, vesicle trafficking and secretion, and barrier function in various organs. Here we investigated the expression and role of EPAC in signaling apical membrane dynamics.

Bladders from female Sprague Dawley rats and New Zealand white rabbits were used for western blot and immunohistochemistry or for culturing urothelial cells for fura‐2 calcium imaging and ATP release. Transepithelial capacitance was measured by placing bladder mucosa in modified Ussing chambers and increasing hydrostatic pressure to mimic bladder filling (in the presence or the absence of EPAC agonist‐ 8‐pCPT, or antagonist‐ ESI‐09).

EPAC was expressed in the urothelium, however the agonist did not alter Ca2+ nor ATP release in cultured cells. Nevertheless, the EPAC agonist (used in rabbit UT) significantly increased transepithelial capacitance (30% vs 7% in control) in the absence of stretch; stretch‐induced capacitance was reduced by the EPAC antagonist.

Our results indicate that EPAC plays an important role in augmenting bladder filling induced increases in urothelial surface area. The lack of ATP involvement suggests that EPAC mediated pathways could lead to increasing bladder capacity without affecting underlying bladder nerves.
Tumor necrosis factor‐alpha (TNF) regulates NKCC2 and AQP2 expression and adaptation to high NaCl intake
Authors: Hao Shoujin , DelliPizzi AnnMarie , Hao Mary , Knepper Mark , Ferreri Nicholas
Published: June 2021

We previously showed that ambient urine osmolality was higher in TNF deficient mice compared with age‐ and sex‐matched wild type (WT) mice. As the role of TNF in the kidney is still being defined, effects of renal‐specific TNF silencing on renal Na(+)‐K(+)‐2Cl(‐) cotransporter (NKCC2) and aquaporin‐2 (AQP2) expression was determined. Six days after intrarenal injection of lentivirus construct EGFP‐TNF‐ex4 into both kidneys of WT mice, renal but not splenic TNF mRNA levels were significantly reduced. Injection of control lentivirus (U6) did not alter TNF mRNA in either kidney or spleen. EGFP‐TNF‐ex4, but not U6, also increased NKCC2A mRNA levels in renal outer medulla and inner medullary AQP2 mRNA and protein expression. Urine osmolality increased in mice injected with EGFP‐TNF‐ex4 compared with those injected with U6, suggesting that the increase in NKCC2 and AQP2 due to renal silencing of TNF contributed to an increase osmolality. As TNF production by the TAL was induced by administration of 1% NaCl in the drinking water for 3 days, the effects of TNF silencing on urine volume were determined. Mice were acclimated in metabolic cages for 3 days after receiving intrarenal injections of either EGFP‐TNF‐ex4 or U6. Food, body weight, water intake, and urine output was then measured in mice given 1% NaCl or tap water for 3 days. Both water intake and urine output were reduced in mice injected with EGFP‐TNF‐ex4 compared with mice given U6 lentivirus. The decrease in urine volume was associated with an increase in NKCC2A and AQP2 mRNA accumulation. Collectively, these findings suggest that TNF produced by the kidney inhibits transporter expression and regulates responses to high NaCl intake.
A Renal Olfactory Receptor Aids in Glucose Handling in the Proximal Tubule
Authors: Shepard Blythe , Cheval Lydie , Doucet Alain , Pluznick Jennifer
Published: June 2021

Olfactory receptors (ORs) are seven transmembrane‐domain G protein‐coupled chemosensors that detect odorants in the nose. We previously reported that ORs play roles in the kidney, and identified 9 renal ORs including Olfr1393. In reverse‐transcribed RNA from microdissected renal segments, Olfr1393 is exclusively expressed in the proximal tubule (PT; S1, S2 and S3). When stably expressed in polarized MDCK cells, Olfr1393 localizes to the apical plasma membrane (PM), but not to cilia. Because Olfr1393 is an “orphan receptor” with no known ligand, we screened over 1400 chemicals and found that Olfr1393 detects preconstrained cyclic molecules containing carbonyl or alcohol groups. To determine the physiological role of Olfr1393, we generated knockout (KO) mice. At baseline, KO mice are similar to wild‐type (WT) littermates with regard to plasma electrolytes, blood pressure and GFR (measured via iStat, tail cuff, and elimination kinetics of plasma sinistrin). However, despite being euglycemic, KO mice exhibit glycosuria (1.4x increase in glucose/creatinine vs WT) and can better handle a glucose challenge during a glucose tolerance test as indicated by plasma glucose values (area under curve: WT 22.4 ± 1.9 vs KO 15.7 ± 1.1; P = 0.001). These data suggest that Olfr1393 helps to regulate glucose reabsorption on the apical PM of the PT. In support of this, preliminary data suggests that heterologously expressed Olfr1393 can co‐immunoprecipitate with Sglt1 and Sglt2, the two Na+/glucose co‐transporters responsible for apical glucose reabsorption. We are currently examining the possibility that Olfr1393 influences the function of these transporters to regulate PT glucose handling.

Funding: ASN, NIDDK
Time Course of Immune Cell Infiltration and Cytokine Production in the Kidneys of Dahl Salt‐Sensitive (SS) Rats
Authors: Petrova Galina , Mattson David
Published: June 2021

Inflammation and immunity has been implicated in hypertension and renal disease in animals and humans. Previous studies from our lab have demonstrated that pharmacological or genetic inhibition of immune cell infiltration in the kidney attenuates salt‐sensitive hypertension and kidney damage in SS rats. The present studies were performed to assess the temporal infiltration of different immune cell subsets into the kidneys of Dahl SS rats when maintained on a low salt (0.4% NaCl, Day 0) diet and after 7, 14 and 21 days of high salt (4.0% NaCl) intake. Using a flow cytometry‐based approach, a progressive increase of infiltrating cells in the kidneys of Dahl SS was observed with time on the high NaCl diet. The total number of CD45+ cells (9.3±1.96 vs 35.2±6.8 x 105 cells/kidney), CD3+CD8+ cells (.69±.13 vs 1.9±0.2 x 105 cells/kidney) and CD3+CD4+ cells (.36±.08 vs 1.78±0.37 x 105 cells/kidney) significantly increased from Day 0 to 21 of a high salt diet (n=9‐17 rats/group). Stimulation of isolated kidney cells with PMA and ionomycin followed by intracellular cytokine staining revealed an increase in the number of IFN‐g producing CD8+ T cells and also in TNF, IFN‐g and IL‐17 producing CD4+ T cells (e.g. CD3+CD4+IL‐17+ cells increased from .05±.01 to .56±.16 x 105 cells/kidney from Day 0 to Day 21). IFN‐g and IL‐17 production by CD4+ T cells positively correlated with the number of regulatory T cells (increased from .09±.02 to .43±.01 x 105 cells/kidney from Day 0 to 21) and the total number of activated CD4+ T cells (increased from .14±.02 to .84±.02 x 105 cells/kidney from Day 0 to 21). These data indicate that the time course of immune cells infiltration and cytokine production by T cells parallels hypertension and kidney damage in Dahl SS rats fed a high salt diet.

This work is supported by DK‐96859 and HL116264.
NH3 Permeability versus CO2 Permeability: Insights from Mathematical Modeling
Authors: Occhipinti Rossana , Boron Walter
Published: June 2021

Exposing a cell to a solution containing NH3/NH4+ leads to a rapid NH3 influx, which causes a rise in intracellular pH (pHi) and a transient decrease in surface pH (pHS). Conversely, exposing a cell to a solution containing CO2/HCO3− leads to a rapid CO2 influx, which causes a fall in pHi and a transient increase in pHS.

In our laboratory we use the maximal change in the height of the pHS transient (ΔpHS) as a semiquantitative index of membrane permeability to NH3 (PM,NH3) or to CO2 (PM,CO2). As a first step in extracting absolute membrane permeability from pHS measurements, in 2012 we developed a reaction‐diffusion mathematical model of CO2 influx to investigate the dependence of ΔpHS predicted by the model on PM,CO2 values (Somersalo et al, J Theor Biol, 2012). To account for physiological data on gas channels, the model predicts that,contrary to widespread assumptions, the membrane must offer considerable resistance to the movement of CO2.

Here, we investigate the dependence of ΔpHS versus PM,NH3 with a reaction‐diffusion mathematical model of NH3 influx into a spherical cell. The model is an extension of the model of Somersalo et al, in which now we include the NH3/NH4+ buffer equilibrium and passive transmembrane flux of NH3. After having checked that the model correctly predicts the transient changes in pHi and pHS that one would expect as NH3 enters a cell, we performed simulations in which we systematically decreased PM,NH3 from that corresponding to a thin film of water. By comparing the dependence of ΔpHS versus a range of PM,NH3 (present study) with the dependence of ΔpHS versus PM,CO2 (Somersalo et al), we conclude that, contrary to the Overton's prediction (which considers only solubility in the membrane), the background PM,NH3 (in absence of gas channels) is far higher than the background PM,CO2.
On the Interaction of the Na/K ‐Pump ATPase (NAKPA) with Pro‐Survival and Pro‐Apoptotic Bcl‐2 Proteins
Authors: Lauf Peter , Alqahtani Tariq , Flues Karin , Maharjan Chandra , Adragna Norma
Published: June 2021

By combining in silico approaches with pharmacological studies on the inhibitory action of quaternary benzenephenanthridine alkaloids (QBA) on Na/K Pump ATPase (NAKPA), we recently proposed that QBA, which binds to specific motifs in Bcl‐2 proteins (J Mol Biol 364: 536‐549, 2006), does so also to analogous regions in the NAKPA protein. Hence by analogy, Bcl‐2 proteins must also interact with and may modulate NAKPA (Cell Physiology and Biochemistry 2013). To prove this new hypothesis, we have recently demonstrated by immunochemical techniques that indeed NAKPA interacts with both pro‐survival BclXl and pro‐apoptotic BAK proteins, and thus may constitute an important sensor complex in life and death decisions of the cell (Am J Cell Physiol 2014, PMID 25318106). Presently, this complex appears to be of quaternary nature, in which Bcl‐2 proteins of opposite action may bind to and modulate directly NAKPA and vice versa because only NAKPA antibodies can pull down both Bcl‐2 proteins but not vice versa. Here we review this new model and present further immunochemical data with additional Bcl‐2 proteins, and with bodipy‐fluorescent ouabain and anti‐Bcl‐2 protein directed antibodies to support or modify this new concept.
The efficacy of adipose‐derived stem cells sheet in preventing pancreatic fistula following pancreas body transection in rats
Authors: Kaneko Hirokazu , Yokoyama Yukihiro , Yamaguchi Jyunpei , Yamamoto Tokunori , Shibata Rei , Kokuryo Toshio , Nagino Masato
Published: June 2021

BACKGROUND

A pancreatic fistula (PF) is one of the most common and fatal complications after pancreatic resection. Thus the prevention of PF is urgent in pancreatic surgery. However, there is no effective strategy in preventing PF.

AIM

We studied the efficacy of adipose tissue‐derived stem cells (ADSCs) sheet with mannose for the prevention of PF in rat pancreatic fistula model.

METHODS

Wister rats underwent transection of the pancreas body to develop PF. ADSCs cultured in sheet form were made and applied to the transected pancreatic stump. Rats were allocated to the following three groups; non‐treatment (n=9), ADSCs sheet treatment (n=5), ADSCs sheet treatment with mannose (n=5) groups. The amylase and lipase levels were measured in the ascetic fluid at two days after operation.

RESULTS

Ascitic amylase levels were (107±30)×103 U/L in the non‐treated group, (26±10)×103 U/L in the ADSCs sheet group, and (15±3)×103 U/L in the ADSCs sheet with mannose group. The levels were significantly lower in the ADSCs sheet with mannose group compared to the non‐treated group(P= 0.04). Lipase levels also showed a similar trend in ascitis. Intra‐peritoneal lipolysis was minimum in the ADSCs sheet with mannose group compared to other groups.

CONCLUSION

The application of ADSCs sheet on the pancreatic stump is effective in preventing PF. Adding mannose enhanced the effect of ADSCs sheet. We are now investigating the molecular mechanisms of ADSCs sheet concerning tissue repair process.
ERK 1/2 Mediates H2O2‐Induced Increase in Renal Epithelial Paracellular Permeability
Authors: Jaggi Shirin , Voronina Angelina , Axis Josephine , Amsler Kurt
Published: June 2021

The paracellular permeability of renal epithelia is determined primarily by the integrity of the tight junction (TJ) structure located at the apicolateral borders of adjacent epithelial cells. Treatment of confluent populations of MDCK cells (distal tubule‐like) and LLC‐PK1 cells (proximal tubule‐like) with hydrogen peroxide (H2O2) increases the paracellular permeability to large solutes in a concentration‐dependent manner. H2O2 was cytotoxic at higher concentrations. We have examined the involvement of Mitogen‐Activated Protein Kinases (MAPKs) in mediating these H2O2 actions. Treatment with H2O2 increased the phosphorylation (activation) of multiple MAPKs, ERK ½, JNK ½, and p38MAPK, in a time‐dependent manner. Phosphorylation of each MAPK peaked at 10‐30 minutes and declined by 120 minutes. Pretreatment of cells with U0126 or PD98059, inhibitors of ERK ½ activation, blocked the ability of H­2O2 to increase paracellular permeability. SB202190, a p38MAPK inhibitor, diminished but did not entirely block the H2O2 effect. Treatment of cells with SP600125, an inhibitor of JNK ½ activation, did not affect the ability of H2O2 to increase paracellular permeability. Pretreatment with U0126 and SB202190, but not SP600125, also diminished the cytotoxicity observed at higher H2O2 concentrations. These results indicate that MAPKs, in particular ERK ½, have a central role in mediating the effects of H2O2 on both modulation of paracellular permeability and induction of cytotoxicity in renal epithelial cells. (supported by NIH 1R15DK091749)
Rapid Onset Vasodilation is Blunted with Aging: Evidence for Limb Specificity?
Authors: Hughes William , Treichler David , Ueda Kenichi , Casey Darren
Published: June 2021

We aimed to examine the impact of aging on rapid onset vasodilation (ROV) in the leg following single muscle contractions. Young (n=14; 23±1yr; 9M/5F) and older (n=14; 66±1yr; 10M/4F) adults performed single muscle contractions at 20%, 40%, and 60% work rate maximum for knee extension. Diameter and blood velocity were measured in the femoral artery using Doppler ultrasound. Limb vascular conductance (VC) was calculated using blood flow (mL/min), mean arterial pressure (mmHg) and normalized for muscle mass (kg). Older adults demonstrated lower peak and total contraction‐induced vasodilation in the leg across exercise intensities compared to young adults (P < 0.001). To explore limb specific differences, leg responses at 20% and 40% were compared to single contractions of the forearm (handgrip) within each subject. At 20%, both older and young adults had a higher ΔVC in the arm vs leg (Older: 90±7 vs. 49±4 mL/kg/min/100mmHg, P < 0.01; Young: 123±7 vs. 94±10 mL/kg/min/100mmHg, P < 0.05). Similarly, a higher ΔVC in the arm vs. leg was also observed at 40% in older and young adults (Older: 126 ± 9 vs. 62±5 mL/kg/min/100mmHg, P < 0.01; Young: 168±11 vs. 109±10 mL/kg/min/100mmHg, P < 0.05). Our data demonstrate that 1) aging blunts skeletal muscle contraction‐induced ROV in the leg and 2) when normalized for muscle mass, both young and older adults demonstrate a greater ROV in the arm compared to the leg.
The Blood Pressure Lowering Effect of the Aqueous Calyx Extract of Hibiscus sabdariffa May Occur via a Sympathetic Nervous System Dependent Mechanism
Authors: Mojiminiyi Frank , Aliyu Buhari , Oyeniran Oluwatosin , Alex Isu
Published: June 2021

The aqueous calyx extract of Hibiscus sabdariffa (HS) has been reported to lower blood pressure (BP) in animals and man. This study tested the hypothesis that the hypotensive effect of HS may occur through a sympathetic nervous system (SNS) dependent mechanism. Following ethical approval and informed consent, the Harvard step test (HST) was performed in healthy subjects (n=14) to activate the sympathetic nervous system (SNS) before and after the oral administration of HS (15mg/Kg). The BP and pulse rate (PR) responses were measured. Mean arterial pressure (MAP; taken as representative BP) was calculated. Experiments were performed in accordance with the Principles of the Declaration of Helsinki. Results are expressed as mean ±SEM. Paired t test was used for statistical analyses and P<0.05 was considered significant. HST without HS resulted in a significant rise in MAP and PR (112.6 ± 2.7mmHg and 97.7 ± 2.5/min) from the basal values (98.5±2.3mmHg and 76.6±2.0/min; P<0.001 and 0.01 respectively). In the presence of HS, HST‐induced changes (ΔMAP=14.2±2.6 ΔPR= 11.4±3.5) were significantly dampened compared to its absence (ΔMAP= 24.1±2.5 ΔPR= 20.1±3.1; P<0.001 and 0.01 respectively). The HST‐induced increases in BP and PR suggest SNS activation. These were dampened by HS suggesting that its hypotensive effect may occur through the inhibition of systemic vascular resistance mediated by the SNS.
Cerebral Blood Flow Velocity and Cognitive Function Preceding Post‐Exercise Syncope
Authors: Sieck Dylan , Luttrell Meredith , Romero Steven , Ely Mathew , Halliwill John
Published: June 2021

Adequate cerebral perfusion is necessary to maintain consciousness in the upright human. Following maximal anaerobic exercise, cerebral perfusion can become compromised as evident by post‐exercise syncope. It is unknown whether post‐exercise reductions in cerebral perfusion after exercise lead to cognitive deficits prior to the onset of syncope, which would be of utmost concern in populations such as emergency workers and soldiers. Therefore, the purpose of this experiment was to determine if reductions in cerebral blood flow velocity induced by maximal anaerobic exercise and head up tilt lead to visual/cognitive deficits prior to the onset of syncope. We hypothesized that a modified Wingate test followed by a head‐up tilt would reduce cerebral blood flow velocity and result in visual/cognitive deficits prior to the onset of syncope. Ten recreationally active volunteers were subjected to a symptom‐limited 60° head‐up tilt for up to 16 min before and after a 60‐s Wingate test. Blood flow velocity of the middle cerebral artery was measured via transcranial Doppler ultrasound and a visual decision‐reaction time test was assessed in the peripheral visual field. Cerebral blood flow velocity decreased as tilt progressed from 49.6 ± 3.2 to 46.2 ± 2.4 cm/s (mean ± SE; p < 0.05). Also, peripheral decision‐reaction time increased as tilt progressed from 363.7 ± 12.7 to 385.3 ± 18.4 ms (p < 0.05). These data suggest that the reduction in cerebral blood flow velocity following maximal anaerobic exercise contributes to cognitive deficits as evidenced by the concurrent increase in peripheral field decision‐reaction time prior to syncope.

Support provided by NIH grant HL115027
Using the Population Approach to Obtain Individual Estimates From Indirect Calorimetry
Authors: Marsteller Douglas , Del Campo Jacob , St. Peter John , Pirner Mark
Published: June 2021

Quantification of human energy encompasses several domains of research. Consumption of oxygen and release of carbon dioxide are used as an indirect measure of energy output. The goal of this research was to understand if mixed effects modeling could be used to identify structural parameter estimates and the covariates that help explain population variance from measures of indirect calorimetry. Indirect calorimetry was assessed in 160 individuals stratified by gender, aged 18‐30, and with BMI of 20‐25. Measurements were taken for 20 minutes at rest, during a stationary cycling to obtain maximum VO2, and at a load of 125 Watts on stationary cycle for 60 minutes. In the instances of rest and a 125 Watt load, O2, CO2, and the respiratory quotient were modeled as stationary with time. The covariates of gender and weight both explain relevant variance. During the maximum VO2 test, O2 and CO2 were described with a linear model with slope and intercept and included between subject variability, and the respiratory quotient was described as an EMAX model with baseline, EMAX asymptote, Hill Coefficient, and slope. This effort determined a mixed effects modeling approach could be used to assess indirect calorimetry measures. Future studies with additional covariates such as direct measure of body composition may be informative. A design focused on a broad general population to potentially identify sub‐groups would be ideal.
Androgen Mediated Leukocyte Responses to Acute Resistance Exercise
Authors: Fragala Maren , Townsend Jeremy , Jajtner Adam , Oliveira Leonardo , Willoughby Darryn , Beyer Kyle , Gonzalez Adam , Wells Adam , Hoffman Jay , Stout Jeffrey , Fukuda David
Published: June 2021

Testosterone is involved in anabolic and inflammatory pathways by way of its androgen receptor and associated cytokines. We examined androgen (AR), interferon‐γ (INF‐γR), and interleukin‐1 (IL‐1R2) receptor expression and mRNA on circulating leukocytes in response to resistance exercise. Eight resistance trained men (24.8±4.4 y; 91.2±12.4 kg; 14.2±4.1 % body fat) performed resistance exercise and a control test in a balanced, randomized order. Peripheral blood leukocytes were sampled at baseline (BL), immediately (IP), 2‐hours (2H), and 6‐hours (6H) post exercise. AR, INF‐γ R, and IL‐1R2 expression on circulating CD14+ monocytes was evaluated with flow cytometry and mRNA was evaluated with real‐time‐PCR. Time and treatment effects were analyzed with two‐way ANOVA followed by post‐hoc pairwise comparisons. Interactions (p<0.05) were observed for AR mRNA, AR expression, INF‐γR mRNA, and INF‐γR expression. AR mRNA in circulating leukocytes increased from BL at IP (6.22±3.02‐fold; p=0.004), 2H (5.92±2.52‐fold; p=0.002) and 6H (3.67±2.06‐fold; p=0.014) in the exercise trial. AR expression on CD14+ cells increased from BL to 2H in the exercise trial (p=0.045). INF‐γR mRNA in circulating leukocytes increased from BL to 2H (4.02±1.02‐fold; p=0.025) in the exercise trial (p=0.047). No significant interactions in IL‐1R2 mRNA or receptor expression were observed. Observed increases in mRNA content and expression for AR and INF‐γR on circulating leukocytes and CD14+ monocytes support the hypothesized role of testosterone in the acute inflammatory response to resistance exercise in men.
Estrogen Source Influences Muscle Soreness and Recovery in Young Women
Authors: Anderson Lindsey , Baker Lucinda , Schroeder E Todd
Published: June 2021

Methods

100 contractions of maximally tolerated neuromuscular electrical stimulation (NMES) were performed on one quadriceps. The oral contraceptive (OC) group, consuming an exogenous estrogen source, performed NMES between days 8‐11 of pill consumption. The high (HI) and low (LO) endogenous estrogen groups performed NMES between days 19‐21 or 1‐3 of the menstrual cycle, respectively; day 1 was menses onset. HI and LO did not take OC. Maximal voluntary isometric contraction (MVIC) was assessed before, 0, and 48 hours post. Soreness was measured before and 48 hours post with a 7‐point and 10‐point Likert Scale of Muscle Soreness for Lower Limb (LSMSLL) and a 100 mm visual analog scale (VAS). Maximum and average Rating of Perceived Exertion (RPE) and Pain were reported for the NMES bout.

Results

Mean maximum (15.9) and average (13.8) RPE were similar across groups. HI reported 2‐3 points lower mean maximum and average Pain than OC or LO.

OC (N=5)
HI (N=2)
LO (N=2)

Age (years)
25 (3)
25 (1)
27 (3)

BMI (kg/m2)
23.2 (1.4)
22.6 (4.7)
24.1 (3.8)

Body Weight (kg)
63.9 (5.3)
58.1 (12.0)
65.5 (7.4)

Lean Mass (kg)
45.9 (3.4)
41.7 (3.6)
41.3 (2.8)

Percent Fat
27.8 (5.9)
27.4 (8.7)
32.2 (17.3)

NMES

MVIC (N)
335.4 (49.6)
355.5 (41.0)
263.1 (96.1)

%MVIC (avg NMES force)
34.2 (7.7)
44.8 (3.6)
43.3 (26.0)

%MVIC (0 hrs post)
86.4 (18.3)
82.7 (4.6)
71.4 (3.2)

%MVIC (48 hrs post)
97.4 (7.6)
86.4 (11.0)
91.1 (40.4)

Soreness

Delta_VAS (mm)
380.5 (196.4)
587.5 (116.7)
375.0 (176.8)

Delta_7 pt
2.8 (0.8)
4.0 (0.7)
3.8 (1.1)

Delta_10 pt
4.2 (1.9)
5.8 (1.8)
6.0 (2.8)

Conclusion

These results are interpreted with the knowledge that this is an ongoing study with recruitment goals of N=7 per group. Given the current small sample size and large variability, exogenous estrogen may increase exertion perception as OC did less work and experienced less soreness and faster recovery than HI and LO despite higher lean mass and similar exertion rating. Either source of estrogen may decrease immediate post‐exercise fatigue as LO displayed a greater degree of strength loss at 0 hours post NMES despite doing similar work to HI and more work than OC. Future analysis requires covarying for absolute force and lean mass.
Relationship Between Cortisol and Free Testosterone in Response to Exhaustive Endurance Exercise
Authors: Lane Amy , Anderson Travis , Hackney Anthony
Published: June 2021

Research has shown intensive exercise to induce significant changes in cortisol (C) and testosterone (T). Typically, increases in C are witnessed concurrently to decreases in T. To determine whether there was the existence of a relationship between the changes observed in these two hormones, we measured the change scores (Δ) for 12 healthy, endurance trained males (X±SD: age 22.8±3.1y; VO2max 66.3±4.8 mL/kg/min) in response to an exhaustive exercise session (EES) (96.9±10.8 min at 74.7±4.6% of VO2max). The change scores were determined for basal levels of C and free T from pre to post EES (Δ0), post to +24h (Δ24), +48h (Δ48) and +72h (Δ72) into recovery. All basal hormonal levels were within acceptable clinical ranges for these subjects. The EES induced highly significant C increases (pre: 326.5±29.3nmol/L, post: 700.8±177.7nmol/L; p<0.001) and free T decreases (pre: 162.3±23.6pmol/L, post: 106.1±38.6 pmol/L; p<0.001) at Δ0. A significant negative correlation existed between C (Δ 374.3 nmol/L) and free T (Δ ‐56.2 pmol/L) at Δ0 (p=0.028, rs = ‐0.629; Spearman rho). No additional significant changes were detected into recovery. Cumming et al (J Clin Endocrinol Metab. 57:671, 1983) illustrated the phenomenon of C induced T reduction via pharmaceutical intervention. This study indicates a single bout of EES will induce similar effects endogenously, i.e., with elevated levels of C being associated with suppressed free T, perhaps through mechanisms directly associated with T production inhibition.
Response Analysis of Hemodynamics Parameters to Tyramine Infusion Post‐Exercise Training in Spountaneously Hypertensive Rats
Authors: Miranda Munique , Fonseca Pinheiro Rafael , Santos Milena , Rocha Alessandro , Mota Gustavo , Marocolo Júnior Moacir , Barbosa Neto Octavio
Published: June 2021

The aim of the study was to assess the effects of exercise training in the vascular control after sympathetic stimulation mimicked by tyramine infusion in spontaneously hypertensive rats (SHR). Thirty two male SHR and wistar kyoto were submitted or not to a swimming protocol, resulting in four groups: sedentary normotensive (SN), trained normotensive (TN), sedentary hypertensive (SH) and trained hypertensive (TH). Arterial pressure (AP), heart rate (HR), power spectral analysis of HR (HRV), systolic AP variability (SAPV) and diastolic (DAPV) were recorded in baseline conditions. Following, the infusion of tyramine was administrated. Resting bradycardia was observed in both TN and TH rats compared with their respective sedentary animals. Exercise training attenuated AP in TH vs. SH. The variance of HRV was lower in SH vs. TH. The variance of SAPV and DAPV were higher in SH vs. TH. The LF component of HRV, SAPV and DAPV were lower in TH than SH. The pressor response to tyramine was enhanced in trained SHR but not kyoto. In conclusion, the results points to a sympatolitic effect of exercise training, probably at pre synaptic level, suggesting an up regulation of α1‐receptors in vascular smooth muscle. These findings showed that exercise training may be a therapeutic tool for improving function in hypertensive individuals.
Exercise Attenuates Age‐Associated Reductions in Muscle Strength and Cardiorespiratory Fitness in Mice
Authors: Dillon Gabrielle , Drake Ty , Huey Kimberly
Published: June 2021

Aging is associated with losses in muscle strength and cardiovascular fitness that may be offset with regular exercise. While exercise adaptations may diminish with age, robust adaptations still occur. We tested the hypothesis that aging reduces muscle function and cardiorespiratory endurance, however voluntary (running wheel, RW) or prescribed (treadmill (TM) training) exercise will attenuate these aging‐associated decreases in strength and fitness. In vivo plantarflexor maximal force and fatigue (% of max force after 10 contractions) were measured in young (4 mo. old) and aged (24 mo. old) sedentary (SED) mice and following 2 wks of RW (24h wheel access) or TM training (45 min/day, 5 day/wk). Cardiorespiratory adaptations were assessed with pre‐ and post‐maximal treadmill tests. Maximal muscle force was lower in aged than young SED mice (1.1±0.04 vs. 1.6±0.07 g/kg BW, respectively, p<0.05). In young groups, neither RW nor TM increased force over SED. In aged groups, RW and TM were associated with respective 22 and 26% higher maximal forces than aged SED mice (p<0.05), but still were lower than young groups. Plantarflexor fatigue resistance was higher in aged than young SED mice (50±3 vs. 35±3% of max, respectively, p<0.05) with no age differences in RW and TM groups. In treadmill pre‐tests, young groups ran longer than aged groups (9:23±0:52 vs. 5:09± 0:51, respectively p<0.05). Increases in treadmill time after training occurred only in young and aged TM with respective 25:34±8:24 and 16:42±2:39 increases from pre to post test (p<0.05). These findings suggest voluntary and prescribed exercise attenuate some age‐associated reductions in muscle force, but prescribed exercise is most effective in improving cardiorespiratory fitness in young and older mice.
Enhanced Muscle Mass and Contractile Function Recovery via Resistance Training after VML Injury
Authors: Song Taejeong , Lee Kwangjun , Farrar Roger
Published: June 2021

Volumetric muscle loss (VML) is traumatic muscle injury that causes irreversible loss of muscle mass and permanent deficit of muscle function. Decellularized muscle scaffold has been utilized to fill the defected area and provide platform for muscle regrowth, but it has limited effects on recovering muscle mass and contractile functions. Thus additional intervention is required for promoting restorations of muscle mass and function after the VML injury.

PURPOSE

To test effects of resistance exercise on muscle mass and functional recoveries after VML injury

METHODS

1×1cm full thickness proximal portion of later gastrocnemious (LGAS) was cut to induce VML injury of adult rats. About 19% of total LGAS mass was removed from one leg and decellularized porcine skeletal muscle extracellular matrix (ECM) was transplanted in the defected site connecting remnant of muscle. Ladder climbing exercise started ten days after the injury. Every third day, the mechanical load of the resistance training was increased each bout. In‐situ peak tetanic tension of LGAS was measured at 8 weeks after the injury followed by measuring length and mass of LGAS.

RESULTS

Progressive resistance training utilizing ladder climbing exercises significantly improved recovery of LGAS muscle mass (88% of contralateral LGAS) compared to that of sedentary control (77%)(P<0.05). Peak tetanic tension of injured LGAS recovered 90% of contralateral LGAS in exercised group, but it was only reached 75% of non‐injured LGAS in the sedentary control. The specific tension of the LGAS of the trained group was same as control muscle.

CONCLUSION

Resistance exercise treatment has beneficial effect on restoration of muscle mass, and it also enhanced functional recovery of defected LGAS muscle after VML injury.
Exercise‐ and Kefir‐induced Internalization of the Anti‐inflammatory Melanocortin 3 Receptor in Monocytes
Authors: Scott Valerie , O'Brien Keely , Boeneke Charles , Stewart Laura , Forney Laura , Henagan Tara
Published: June 2021

Exercise decreases chronic inflammation and kefir, a fermented milk product, has the potential to further attenuate inflammation. Exercise may upregulate anti‐inflammatory pathways in monocytes by activating and increasing internalization of melanocortin 1 (MC1R) and 3 receptors (MC3R). Here, we determined the effects of marathon training and kefir supplementation on systemic monocyte cell surface and internal MC1R and MC3R protein expression via flow cytometry. Healthy, adult males and females (18‐24 yrs) were assigned to one of 4 groups: 1) active control + control beverage (C), 2) active control + kefir (K), 3) endurance training + control beverage (EC) or 4) endurance training + kefir (EK). EC and EK completed 15 weeks of marathon training. C and K maintained their usual exercise routines. EK and K supplemented with kefir and C and EC with a calorie/macronutrient matched placebo beverage twice/week. Blood samples were collected (72h post exercise) and stained with CD14 and MC1R or MC3R antibodies. Internal MC3R but not MC1R was increased in EK compared to K (45.16 ± 4.79 vs 24.51 ± 4.62 MFI, P < 0.05) but not EC; additionally, EC was not different from C. Endurance training plus kefir supplementation may act synergistically to decreased chronic inflammation through activation and internalization of the anti‐inflammatory MC3R in monocytes.
Effects of Aerobic Interval and Moderate Continuous Training on Left Ventricular Mechanics in Sedentary Men
Authors: Huang Yu‐Chieh , Wang Jong‐Shyan
Published: June 2021

Improved myocardial contractility is a critical circulatory adaptation to aerobic exercise training. What kind of the exercise strategy that enhances contractility efficiency in heart has not yet been established. This study investigated how aerobic interval (AIT) and moderate continuous training (MCT) influence the left ventricular (LV) mechanics in sedentary men. Thirty‐six sedentary males were randomized to perform AIT (3‐minute intervals at 40% and 80% VO2max, n=18) or MCT (sustained 60% VO2max, n=18) for 30 minutes/day, 5 days/week for 6 weeks. LV mechanics were measured by two‐dimensional and speckle tracking echocardiography at normoxic (21% of FIO2) and hypoxic (12% of FIO2) environments. The experimental results demonstrated that AIT exhibited higher enhancement of cardiac output and VO2 at peak performance, compared to MCT did. Moreover, the AIT group also had higher increases in LV mass and stroke volume than the MCT group. In LV contractile efficiency, AIT, rather than MCT, significantly decreased apex rotation to reduce degree of torsion and simultaneously increased circumferential strain of mitral valve segmentation under normoxic and hypoxic conditions.Hence, we conclude that AIT is superior to MCT for enhancing aerobic capacity. Moreover, AIT effectively improves LV mechanics by increasing contractile efficiency at normoxic and hypoxic environments in sedentary men.
Interval and Continuous Exercise Regimens Reduce Senescent T‐Lymphocyte Subsets in Blood
Authors: Chou Cheng‐Hsien , Wang Jong‐Shyan
Published: June 2021

The integration and control of systemic immune responses depends on the regulated trafficking of T‐lymphocytes. This study elucidates how interval and continuous exercise regimens affect phenotypic characteristics of T‐lymphocyte subsets in blood. Twenty‐four sedentary males were randomized to perform either aerobic interval training (AIT; 3‐minute intervals at 40% and 80%VO2max, n=12) or moderate continuous training (MCT; sustained 60%VO2max, n=12) for 30 minutes/day, 5 days/week for 6 weeks. At rest and immediately after hypoxic exercise test (HE, 100W under 12%O2 for 30 min), the senescent (CD57), co‐stimulatory (CD28), homing (CD11a and CD62L), and naïve/memory (CD47Ra/CD47Ro) molecules on T‐lymphocyte subsets were measured by flow cytometry. The results showed that HE increased the mobilization of CD4, CD8, or CD8bright lymphocytes expressing CD11a or CD57 molecules into the peripheral blood compartment before performing AIT or MCT. Following the 6‐week intervention, both MCT and AIT up‐regulated CD28, CD11a, and CD45Ra molecules and depressed CD57 expression on CD4, CD8, or CD8bright lymphocytes at rest or following HE. Therefore, we conclude thateither AIT or MCT regimen effectively reduce senescent and enrich homing and co‐stimulatory T‐lymphocyte subsets in blood. These findings can help to determine an effective exercise regimen to minimize immune dysfunction by retarding T‐lymphocyte senescence.
Respiratory Monitoring System for Underwater Use
Authors: Warkander Dan , Boone Henry , Shykoff Barbara
Published: June 2021

Monitoring a diver's respiratory parameters is a challenge. A respiratory monitoring system (RMS) should allow measurements of gas flows, gas composition (O2 and CO2, breath by breath) and pressure swings at the mouth. For physiologic research, breathing resistance and gas composition should be independently adjustable. The pressure of the breathing gas relative to the diver's lung centroid (static lung loading, hydrostatic imbalance) should be controlled. Ideally, an RMS has no depth limitations.

In the RMS described here, the diver breathes through a full face mask and large bore hoses to an inspiratory and an expiratory side. Each side has a flow meter and temperature and pressure (relative to the mask) sensors. The inspiratory side is supplied with a constant, surface‐adjustable gas flow to a bag from which the diver breathes. This flow is adjusted to keep the bag full at the beginning of inhalation. Excess gas bubbles into the water. Expiration is buffered by another bag and bubbles into the water.

Gas from the mask is sampled to a mass spectrometer for continuous analysis. The flow meter, mass spectrometer, pressure and temperature signals are displayed in real time and recorded.

The prone diver is positioned on a cycle ergometer that keeps the chest in a known position relative to the RMS. The depth of the exhaust ports of the RMS relative to the diver's lung centroid controls hydrostatic imbalance. Resistance elements can be added to either breathing hose. The size and shape of the breathing bags set elastic loads.

Breathing gas with selected concentrations of O2 and CO2 permits assessment of gas composition effects on respiratory performance when a diver is challenged by experimenter‐imposed respiratory impediments. The RMS has been used in a pool at a depth of about 3 m in close to 100 experiments without incident.
Where have all the bubbles gone?
Authors: Barak Otto , Madden Dennis , Lovering Andrew , Lambrechts Kate , Ljubkovic Marko , Dujic Zeljko
Published: June 2021

Besides intracardiac shunts, such as a patent foramen ovale (PFO), that allow paradoxical embolization, emboli can bypass the pulmonary microcirculation via dynamic large intrapulmonary arterial‐venous anastomoses (IPAVAs). They are believed to be closed at rest but open with exercise. They allow venous gas emboli (VGE) to cross over to the arterial side of the circulation. Whether these arterial gas emboli (AGE) reach the cerebral circulation is not known. For this study we recruited twenty PFO negative SCUBA divers and conducted a field study with the aim to investigate the appearance of AGE in intracranial vessels. They performed a single dive to a depth of 18m sea water with a 47‐min bottom time and a direct ascent to the surface. Transthoracic echocardiography was used to grade VGE and AGE scores. Transcranial Doppler was used to visualize middle (MCA) and posterior cerebral (PCA) arteries and objective automated bubble counting was applied. Observations were conducted for 45 min post‐dive at rest, throughout an incremental cycle exercise test in the supine position until exhaustion and for 10 min of recovery. After surfacing all divers presented VGE (bubble grades from 1 to 4B) and arterializations were present in 3/20 divers. Incremental exercise increased only the incidence of arterializations at higher workloads but not the AGE grades. The total amount of AGE that reached the MCA and PCA was 2 at 60W, 3 at 90W, 5 at 120W, 7 at 150 W and 5 at 180W. Exercise‐induced IPAVA recruitment was not coupled with a parallel increase in bubble count in the MCA and PCA.