bluuebunny/crossref_metadata_2025_split huggingface dataset:
A new view of macula densa cell microanatomy
Authors: Gyarmati Georgina , Moon Ju‐Young , Brison Anne Riquier , Peti‐Peterdi Janos 
Published: November 2023

Macula densa (MD) cells are well known as chief regulators of renal and glomerular hemodynamics and renin secretion. However, their new, non‐traditional function as master regulators of renal tissue remodeling is emerging. The present study aimed to explore the microanatomical basis and regulation of the secretory phenotype of MD cells by directly visualizing the morphological features of living MD cells in male and female mice on low, normal, and high salt diet. A new mouse model (MD‐GFP mice) was generated with inducible and conditional MD‐specific, membrane‐targeted expression of the fluorescence reporter EGFP by crossing nNOS‐CreERT2 and mTmG‐floxed mice. MD cells were freshly isolated from digested kidneys of MD‐GFP mice using FACS sorting, and high resolution time‐lapse multiphoton imaging was performed to visualize single, living MD cells. Also, suboptimal tamoxifen induction was performed in MD‐GFP mice, which resulted in the membrane‐targeted expression of EGFP only in a single MD cell per MD plaque and allowed high resolution imaging of the MD ultrastructure on fixed histological sections, including both the plasma and intracellular membranes. MD cells featured very long (~10 μm) single primary cilia at the apical membrane, and a dense network of thin cell processes (up to 20 μm long) at the base of cells projecting into the extraglomerular mesangium. The basal cell processes were more detailed in female mice and in response to low salt diet. Time‐lapse imaging of living MD cells visualized a high number of membrane vesicles trafficking within these cell processes from the cell center to the periphery. These results are consistent with the highly regulated paracrine signaling function and secretory phenotype of MD cells, and suggest the high rate of synthesis and release of novel, yet to be identified secreted MD proteins and their actions on target cell types at the glomerular entrance.Support or Funding InformationNIH R01 DK64324
Direct Evidence that in Rat the Renal Interstitium Contracts in vivo
Authors: Rodríguez‐Martínez Manuel , López‐Rodríguez Juan Francisco , Flores‐Sandoval Omar , Calvo‐Turrubiartes Miriam Zarahí , LLamazares‐Azuara Lilia 
Published: November 2023

Dibutyryl‐cAMP abolishes the RIHP increase in response to renal medullary direct interstitial volume expansion (DIVE = 100 μl in 30 s) with 0.9% saline solution (SS) in hydropenic rats (FASEB J 30:739.9: 2016), suggesting that renal interstitium contracts in vivo. To assess more directly if such an event happens in vivo, we decided to evaluate in hydropenic rats the time course of RIHP before and after either an acute sham (CTR group, n = 9) or an acute (1s) real renal interstitial medullary application (RIMA) of a 5μ bolus of either vehicle (0.9% SS, SS group, n = 9) or 10 μM alpha‐trinositol (anti‐inflammatory drug that increases β1 integrin‐mediated collagen fiber network contraction, A‐T group, n = 9). Left subcapsular RIHP (subcRIHP) and % change of renal outer medullary blood flow (%ΔRoMBF by L‐D) were continuously measured in anesthetized rats with right nephrectomy, acute left renal denervation, hormonal clamp and renal perfusion pressure control (100 mmHg), before (baseline = BL = 30 min) and after sham or real RIMA of 5 μl bolus of either SS or A‐T. There were no differences among groups in body weight, hematocrit nor plasma protein concentration at any time. The table below shows both BL RIHP and ΔRIHP (RIHPafter – RIHPbefore) values (mean ± SEM) obtained at different times points after sham or real RIMA. Three were no differences among groups in BL RIHP. Overall RMMANOVA of ΔRIHP data showed no time effect, but if group (P<0.0004) and time * group interaction effects (P<0.009); 1WRMMANOVA:* P = 0.05, ** P <0.001 vs. Before; 1WANOVA + Tukey test:•P<0.04 vs. SS group, ••P<0.001 vs. CTR group. The %ΔRoMBF showed a similar decrease over time in the three groups.CONCLUSIONSThe results show that acute RIMA of alfa‐trinositol is able to increase the RIHP in hydropenic rats by a mechanism independent of increased renal medullary blood flow, which reinforces the idea of that, at least in hydropenia, renal interstitium contracts in vivo.Support or Funding InformationC15‐FAI‐04‐96.66/UASLP

subcRIHP (mmHg)Before RIMA
subcΔRIHP (mmHg)After RIMA

Group
BL
15 min
30 min
45 min
60 min

CTR
3.0 ± 0.1
−0.85 ± 0.22**
−1.11 ± 0.16**
−1.17 ± 0.19**
−1.16 ± 0.17**

SS
3.1 ± 0.03
−0.30 ± 0.20
−0.15 ± 0.36
−0.38 ± 0.56
−0.51 ± 0.55

A‐T
3.1 ± 0.06
0.54 ± 0.25•◆
1.26 ± 0.51*•◆
0.76 ± 0.37◆
0.68 ± 0.38◆
Hydrophobic residues in the Zonula occludens‐1 (ZO‐1) ZU5 domain contribute to essential junctional activity
Authors: King Jonathan M , Thomason Nicole C , White Addison R , Kannen Krista M , Shen Le , Turner Jerrold R 
Published: November 2023

Zonula occludens‐1 (ZO‐1) is a cytosolic scaffolding protein involved in tight junction formation and maintenance of barrier function. The carboxy‐terminus contains a unique and poorly characterized ZU5 domain while structural data indicates exposed hydrophobic residues that are putative sites of protein interaction. We hypothesized the ZU5 domain contributes to stabilizing interactions and barrier properties of the tight junction. To determine ZO‐1‐ZU5 domain function, EGFP‐ZO‐1, EGFP‐ZO‐1ΔZU5, and EGFP‐ZO‐1 constructs mutated within the hydrophobic pocket of ZU5 were engineered and stably transfected into low‐resistance MDCK lines. The carboxy‐terminus of ZO‐1 contains an actin binding region (ABR) in close proximity to the ZU5 region that has been found to bind to F‐actin, and we hypothesized that the ZU5 region may have a stabilizing effect on these interactions. Actin protection assays indicated the EGFP‐ZO‐1 provides enhanced protection of perijunctional actin from degradation compared to the EGFP‐ZO‐1ΔZU5. The hydrophobic pocket mutants displayed varying degrees of actin protection. ZO‐1 knockdown cells have an increased paracellular flux, and FITC‐dextran paracellular flux assays in ZO‐1‐ZU5 mutants display enhanced leak pathway permeability. FRAP analyses show that EGFP‐ZO‐1ΔZU5 rapidly recovers and the mobile fraction (Mf) is elevated compared to EGFP‐ZO‐1 suggesting an important role in stabilization. Hydrophobic pocket mutants displayed similar changes suggesting the ZU5 domain participates scaffolding ZO‐1 at the tight junction.Support or Funding InformationR01DK061931
Transcranial direct current stimulation transiently increases the blood‐brain barrier solute permeability in rat brain
Authors: Fu Bingmei , Shin Da Wi , Khadka Niranjan , Fan Jie , Bikson Marom 
Published: November 2023

Transcranial Direct Current Stimulation (tDCS) is a non‐invasive electrical stimulation technique investigated for a broad range of medical and performance indications. To test the hypothesis that tDCS with proper dosages can achieve non‐invasive, selective and temporary increases in the blood‐brain barrier (BBB) permeability (P), we used laser scanning multiphoton microscopy with 800~850nm excitation wavelength to determine P of the cerebral microvessels in the rat brain 100–200 μm below the pia mater. After 1 mA tDCS treatment for 20 min, sodium fluorescein (MW 376), or FITC‐dextrans 20K and 70K in 1% bovine serum albumin mammalian Ringer was injected into the rat (SD, 250–300g) cerebral circulation via the ipsilateral carotid artery by a syringe pump at a constant rate of ~3 ml/min. P was determined from the rate of dye spreading images surround individual microvessels in the brain tissue. It was found that the relative increase in P is about 8‐fold for small solute, sodium fluorescein, ~35‐fold for both intermediate sized (Dex‐20k) and large (Dex‐70k) solutes, 10 min after 20 min 1 mA tDCS pretreatment. All of the increased permeability returns to the control after 20 min post treatment. Our results demonstrate that tDCS at a proper strength and duration indeed transiently increases the BBB permeability to different sized solutes to different levels. It can be used as a non‐invasive method for delivering therapeutic agents to brain through the BBB.Support or Funding InformationSupported by NIH R21EB017510‐01.
Single‐vs. double‐leg cycling: lower cardiorespiratory demands and perceived effort for a greater relative power output
Authors: MacInnis Martin J , Morris Nathaniel , Sonne Michael W , Zuniga Amanda Farias , Keir Peter J , Potvin Jim R , Gibala Martin J 
Published: November 2023

Single‐leg cycling is an insightful model of unilateral exercise. It affords a unique comparison of exercise interventions in a within‐subject manner, as the addition of a counterweight to the contralateral pedal facilitates the ‘feel’ of normal double‐leg cycling. The present study characterized physiological responses to single‐ and double‐leg cycling performed at the same relative intensities in twelve men (age: 21 ± 2 years; BMI: 24 ± 3 kg/m2). Graded‐exercise tests initially established that peak oxygen uptake (VO2 peak; +31%), ventilation (VE peak; +33%), heart rate (HRpeak; +9%), and power output (PPO; +78%) were higher (main effect of mode; p < 0.05) during double‐compared to single‐leg cycling. On separate days, subjects subsequently performed four experimental trials, which involved 30‐min bouts of either moderate‐intensity continuous training (MICT) or high‐intensity interval training (HIIT) in a single‐ or double‐leg manner. Although performed at the same percentage of the respective PPO, single‐leg exercise elicited a greater average power output per leg than double‐leg exercise (+13%; p < 0.001). In contrast, average EMG responses from the vastus lateralis and vastus medialis were similar for single‐ and double‐leg cycling (p > 0.05), although the semitendinosus was activated to a greater extent for single‐leg cycling relative to double‐leg cycling (p < 0.001). Single‐leg cycling elicited markedly lower VE, VO2, and HR responses and ratings of perceived exertion compared to double‐leg cycling (p < 0.05). In summary, single‐leg cycling allows for a greater power output (per leg) than double‐leg cycling, while eliciting lower cardiorespiratory and perceptual responses.Support or Funding InformationNatural Sciences and Engineering Research Council of Canada (NSERC)
Muscle Sympathetic Nerve Responses to Passive and Active One‐legged Cycling: Insight into the Contributions of Central Command
Authors: Doherty Connor J. , Incognito Anthony V. , Notay Karambir , Burns Matthew J. , Nardone Massimo , Seed Jeremy D. , Millar Philip J. 
Published: November 2023

Prior studies using neuromuscular blockade to increase perception of effort during mild or moderate intensity handgrip exercise have demonstrated that activation of higher brain regions, termed central command, contribute importantly to cardiac parasympathetic withdrawal but have limited influence on muscle sympathetic activation. The purpose of the present study was to investigate the contribution of central command to the control of muscle sympathetic nerve activity (MSNA) during dynamic one‐legged cycling. Heart rate (HR), mean arterial pressure (MAP), stroke volume, and MSNA (contralateral leg microneurography) were measured in 18 healthy participants (9 men; 22±3 yr of age) at baseline and during two minutes of upright passive cycling movement and active unloaded cycling, each separated by 10 minutes of rest. The increases in HR were greater during the first (Δ3±3 vs. Δ11±7 bpm, p<0.0001) and second (Δ3±4 vs. Δ9±6 bpm, p<0.0001) minute, and MAP during the second minute (Δ4±3 vs. Δ7±5 mmHg, p<0.01), of active unloaded cycling compared to passive cycling movement. Stroke volume increased over time (p<0.001) but was not different between passive and active unloaded cycling (p>0.05). MSNA burst frequency decreased similarly during the first (Δ−4±5 vs. Δ−3±5 bursts/min, p>0.05) and second (Δ−6±4 vs. Δ−4±4 bursts/min, p>0.05) minute of passive and active unloaded cycling. In contrast, total MSNA demonstrated attenuated reductions during the first (Δ−3.2±3.0 vs. Δ−0.6±3.3 arbitrary units/min, p<0.05 [Δ−18±16% vs. Δ0±31%, p<0.05]) and second (Δ−4.5±3.3 vs. Δ−1.5±3.5 arbitrary units/min, p<0.01 [Δ−28±17% vs. Δ−11±24%, p<0.05]) minute of active unloaded cycling. These results support the concept that muscle sympathetic burst occurrence and strength can be regulated independently and suggest that during dynamic leg exercise central command primarily alters vasoconstrictor outflow through modulations in muscle sympathetic burst strength.Support or Funding InformationThis 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.), and a Canadian Institutes of Health Research Fredrick Banting and Charles Best Canada Graduate Scholarship (A.V.I.).
Poincare Analysis of Spontaneous Respiratory Sinus Arrhythmia during High Altitude Ascent: Effects on oxygenation
Authors: Saran Gurkarn , Lavoie Lauren , Linares Andrea , Pfoh Jamie , Bruce Christina , Borle Kennedy , Brandt Rachelle , Tjandra Kartika , Day Trevor A 
Published: November 2023

Respiratory sinus arrhythmia (RSA) is the transient fluctuation in heart rate (HR) in phase with the respiratory cycle. Poincare spectral analysis is used to (a) quantify heart rate variability (HRV) through short term (SD1; i.e., RSA) and long term (SD2) fluctuations in heart rate and (b) determine components of autonomic nervous system activity (low and high frequency; LF and HF; sympathetic and parasympathetic, respectively). Although RSA likely represents the dominance of the parasympathetic nervous system at rest, there is controversy regarding the mechanisms underlying RSA, as well as the possible physiological utility. RSA may improve ventilation and perfusion (V/Q) matching in the lungs, and may protect against oxygen desaturation in the context of hypoxic exposure. We aimed to investigate the relationship between RSA magnitude and peripheral oxygen saturation (SpO2) during incremental ascent to high altitude (4370m). We hypothesized that (a) RSA magnitude (SD1/SD2) ratio would decrease during ascent to high altitude as a result of sympathetic nervous system activation and (b) individuals with a larger SD1/SD2 ratio during ascent would have increased SpO2 through improved V/Q matching. Measurements were conducted over eleven days at 1045m (baseline, day 1), 3440m (day 7), 3860m (day 9), and 4370m (day 11) during a trek to altitude in the Nepal Himalaya. Participants (26±2.1 years; BMI 23.8±1.1 kg/m2; 9 females, n=12) were instrumented with an ECG and finger pulse oximeter (SpO2 %) and tested on rest days after one night at each altitude. Spontaneous RSA was measured from the ECG periods during the last 7‐min of a 10‐min baseline and evaluated using Poincare plots. There was no significant difference between the SD1/SD2 ratio during incremental ascent to 4370m (P=0.65). There was also no significant difference observed in the LF/HF ratios during ascent to 4370m (P=0.66), suggesting that the sympathetic/parasympathetic ratio remained unchanged with ascent. Additionally, we correlated SD1/SD2 ratio and SpO2 at 4370m when individuals were most hypoxic at rest (SpO2 87.2±0.8%) and found no significant correlation (r=0.32, P=0.31). Our data suggests that during slow incremental ascent to high altitude, there is no difference in spontaneous RSA or the balance between sympathetic and parasympathetic nervous system activity. Individuals with larger SD1/SD2 ratios do not have improved SpO2, suggesting that RSA magnitude does not improve V/Q matching during high altitude ascent.Support or Funding InformationNatural Sciences and Engineering Research Council of Canada, Student Temporary Employment Program of Alberta, Alberta Innovates Health Solutions Summer Studentship,
Imposed expiratory resistance, hyperinflation, and dyspnea are dissociated from locomotor fatigue during moderate exercise
Authors: Wickman Brooke E , Sasaki Katelynn G , Torrecillas‐Sanchez Eduardo , Cannon Daniel T 
Published: November 2023

Expiratory flow resistance (e.g. asthma, chronic obstructive pulmonary disease) results in dyspnea, dynamic hyperinflation, and premature exercise intolerance during heavy intensity exercise. This cascade seems to be primarily precipitated by abnormal lung mechanics that result in exacerbated symptoms and reduced maximal evocable limb motor activity. We do not know whether this cascade behaves in the same way during moderate exercise where only modest locomotor fatigue is expected to develop.We hypothesized that expiratory flow resistance would result in dynamic hyperinflation, dyspnea, and exacerbated locomotor fatigue during moderate intensity exercise in a similar manner to that during heavy intensity exercise.Volunteers (N=10, 27±6 yr) completed constant power moderate exercise (50% peak ramp power) with 3 levels of imposed expiratory flow resistance (7, 9, 11 cm H2O·L·s−1) or control (no imposed flow resistance). We measured operating lung volumes during exercise with inspiratory capacity maneuvers. Participants reported dyspnea and leg effort using a Borg 10‐point scale. At the termination of exercise we used a rapid switch from hyperbolic to isokinetic cycling to measure the decline in peak isokinetic power (Piso).Decline in Piso was not different when expiratory flow resistance was imposed (p>0.05). Inspiratory capacity was smaller at the end of exercise in the most severe resistance (11 cm H2O·L·s−1) as compared to control (2.31±1.52 vs. 3.15±0.71 L; p<0.05). Similarly, inspiratory reserve volume was smaller at the end of exercise in the most severe resistance as compared to control (−0.07±1.28 vs. 0.82±0.43 L; p<0.05). Dyspnea was greater at the end of exercise in both mild and severe resistance (7 and 11 cm H2O·L·s−1) as compared to control (5.7±2.5 and 5.2±1.9 vs. 3.7±1.6; p<0.05). Piso was not related to inspiratory reserve volume, inspiratory capacity, or dyspnea (p>0.05).Imposed severe expiratory flow resistance results in hyperinflation and exacerbated dyspnea in healthy volunteers. Unlike what we have found during heavy exercise, however, abnormal lung mechanics and dyspnea were not related to maximal locomotor power during moderate exercise.
Muscle Inflammatory Signaling's Contribution to Cancer Cachexia‐induced Decrements in Muscle Function
Authors: VanderVeen Brandon , Hardee Justin , Fix Dennis , Carson James 
Published: November 2023

Although skeletal muscle mass loss defines cachexia, changes in muscle function related to strength loss and increased fatigue can further impact life quality and health status. However, there are gaps in our understanding of the cachectic environment that regulates muscle function. While cancer‐induced inflammatory signaling can disrupt skeletal muscle protein turnover regulation, inflammatory signaling's contribution to altered cachectic muscle function remains to be determined. Therefore, the purpose of this study was to determine cancer cachexia‐induced inflammatory signaling's contribution to decrements in the functional properties of skeletal muscle. Two preclinical models of cancer cachexia were examined; the ApcMin/+ (MIN) and Lewis lung carcinoma (LLC) implanted mice. The MIN mouse has a nonsense mutation on the Apc gene and develop intestinal tumors by 12 weeks of age resulting in a cachectic phenotype by 20 weeks of age. 106 LLC tumor cells were injected into the flank and mice develop severe cachexia within 5 weeks. Skeletal muscle function and inflammatory signaling was examined in male, MIN (20‐wk, >5% BW loss) and LLC (13‐wk, 30 days' post injection) mice. Tibialis anterior (TA) twitch properties, tetanic force and fatigue were examined in‐situ to maintain intact nerve and blood supply. LLC and MIN decreased TA mass and twitch characteristics compared to their respective controls. LLC and MIN increased 1/2 relaxation time (½ RT), and this change was independent to altered twitch tension. LLC (−33%) and MIN (−41%) decreased tetanic force. Interestingly, only MIN decreased specific tetanic force (−13%). TA fatigability was increased in both MIN (−22%) and LLC (−11%). MIN and LLC increased muscle STAT3 and p65 phosphorylation. The induction of STAT3 and p65 phosphorylation was inversely related to absolute force (R=−0.76, p<0.0001), but only p65 phosphorylation was inversely related to specific tension (R=−0.71, p=0.002). Inflammation was not associated with increased fatigue. There was a trend for STAT3 phosphorylation to be related too increased ½ RT (R=0.46, p=0.07). Cachexia progression altered several skeletal muscle functional properties in 2 distinct cancer cachexia models. While decrements in force production were associated with muscle inflammatory signaling, fatigue susceptibility was not.Support or Funding InformationR01CA121249‐07
Passive Heating Impairs Cardiac Autonomic Regulation during Exercise and Post‐Exercise Recovery
Authors: Peçanha Tiago , Forjaz Cláudia , Low David 
Published: November 2023

AIMThe aim of this study was to assess the effects of passive heating on exercise and post‐exercise cardiac autonomic regulation.METHODSTwelve healthy young men (25±5 yrs, 23.8±1.9 kg/m2, 47.3±7.9 ml.kg−1.min−1) randomly underwent two experimental sessions: heat stress (HEAT) and control (CON). Each session composed of: a heat stress or normothermic control intervention; 7 min of cycling at 40% HRreserve (EX1); 7 min of cycling at 60% HRreserve (EX2); and 10 min of recovery in the seated position (REC). HEAT consisted of 60 min whole‐body passive heating by perfusing hot water (48°C) in a tube‐lined suit to increase core temperature (Tc) by ~1°C. CON consisted of normothermia exposure for a similar timeframe. Heart rate (HR) and finger blood pressure were continuously assessed. HR variability (HRV) was assessed using the vagal‐related RMSSD index, baroreflex sensitivity (BRS) was assessed using the sequence technique and HR recovery (HRR) was assessed through the absolute decrease of HR at 60 (HRR60s) and 300 s (HRR300s) after exercise. Tc, skin temperature (Tsk), forearm skin blood flow (SKBF) and cutaneous vascular conductance (CVC) were also continuously measured throughout.RESULTSTc, Tsk, SKBF and CVC were significantly increased in HEAT compared with CON (Tc: 38.0±0.3 vs. 37.1±0.3 °C; Tsk: 36.8±0.6 vs. 33.2±0.8 °C; SKBF: 160±96 vs. 50±34 A.U.; CVC: 2.3±1.3 vs. 0.6±0.3 A.U/mmHg; all p<0.05). During exercise, HRV and BRS were not different between trials during EX1 and EX2. However, when comparing EX1 of CON with EX2 of HS (i.e. similar absolute workloads), HRV (0.8 ± 0.4 vs. 1.9 ± 0.7 ms; p<0.01) and BRS (0.6 vs. 0.3 vs. 1.5 ± 1.0 ms/mmHg; p<0.01) were significantly reduced in HS. During recovery, HRV (1.7 ± 0.6 vs. 2.6 ± 0.9 ms, p<0.01) and BRS (6 ± 3 vs. 4 ± 3 ms/mmHg; p<0.01) were significantly reduced in HS. Furthermore, HRR60s and HRR300s were significantly reduced in HS (HRR60s = 27±9 vs. 46±10 bpm; HRR300s = 39 ± 12 vs. 61 ± 13 bpm; p<0.01).CONCLUSIONPassive heating impairs cardiac autonomic regulation during exercise at the same absolute workload and during recovery.Support or Funding InformationFAPESP 2013/04997‐0; 2013/05519‐4; 2015/15466‐0