bluuebunny/crossref_metadata_2025 huggingface dataset:
Free Radical Scavenging Decreases Endothelin‐1 (ET‐1) Excretion and Glomerular Permeability During Diabetes
Authors: Saleh Mohamed A. , Stevens David I. , Pollock David M. , Pollock Jennifer S.
Published: June 2021

Hyperglycemia induces renal oxidative stress and renal ET‐1 production. In the present study, we hypothesized that diabetes‐induced oxidative stress activates renal ET‐1 production and/or glomerular permeability. Hyperglycemia was induced in 250–275 g male Sprague‐Dawley rats by a single i.v. dose of streptozotocin (65 mg/kg). The free radical scavenger, tempol (1 mM), was provided to half of the hyperglycemic rats in the drinking water and the other half received vehicle. After 3 weeks, urine, plasma, and renal tissue were collected. Tempol treatment decreased urinary excretion of thiobarbituric acid reactive substances (3959 ± 329.1 nmol/day vs. 6706 ± 608.9 nmol/day, N=8, P<0.001), as well as ameliorated glomerular superoxide production as monitored by dihydroethidium staining. Tempol treatment diminished urinary ET‐1 excretion (16.4 ± 1.5 pg/day vs. 30.6 ± 2.6 pg/day, N=8, P<0.001). Inner medullary prepro‐ET‐1 was attenuated with tempol treatment (0.7±0.12 vs. 1.1±0.12, N=8, P<0.05), although tempol treatment did not change cortical or outer medullary preproET‐1 levels. Glomerular permeability, Palb, (change in glomerular volume induced by exposing isolated glomeruli to oncotic gradients of albumin) was attenuated with tempol treatment (0.42±0.17 vs. 0.80±0.04, N=4, P<0.05). Proteinuria and creatinine clearance were similar in both groups of rats. In conclusion, the free radical scavenger, tempol, attenuated the increase in renal oxidative stress, ET‐1 excretion, and glomerular permeability associated with the early phase of diabetes.
Chronic electrical stimulation of the carotid sinus enhances the sensitivity of baroreflex‐mediated heart rate regulation
Authors: Iliescu Radu , Irwin Eric D. , Cates Adam W. , Georgakopoulos Dimitrios , Rossing Martin A. , Lohmeier Thomas E.
Published: June 2021

Prolonged activation of the baroreflex (PBA) by electrical stimulation of the carotid sinus stimulates the afferent limb of the baroreflex producing sustained reductions in sympathetic activity, average daily blood pressure (BP) and heart rate (HR). We used the sequence method to determine if PBA impairs dynamic baroreflex control of HR. Spontaneous, consecutive, parallel changes in systolic BP (SBP, >1 mmHg) and pulse interval (PI, >5msec) were determined 18 hours/day in 6 normotensive dogs during two weeks of PBA. During PBA at moderate intensity, average systolic BP and HR decreased by 27±3mmHg and 9±2bpm along with sustained reductions in the variability of beat‐to‐beat SBP (19±1 to 14±1) but not PI. The occurrence of non‐baroreflex sequences (opposite changes in SBP and PI) decreased from 32±3 to 18±4 / 10 4beats after 2 weeks of PBA, presumably a consequence of depressed sympathetic activity. In contrast, the number of baroreflex sequences of ≥ 4 beats remained constant (551±118/ 10 4beats) during PBA as baroreflex sensitivity increased ~ 2 fold (Figure). All parameters returned to control levels after 1 week of recovery. These data indicate that PBA chronically suppresses sympathetic activity, increases baroreflex sensitivity and preserves baroreflex HR regulation.

image
Effects of water deprivation and Indomethacin on c‐Fos staining in the Rat Supraoptic Nucleus (SON) of the hypothalamus
Authors: Walch Joseph D. , Little Joel , Ji Lisa , Carreno Flavia , Knight David , Cunningham J. Thomas
Published: June 2021

Vasopressin (AVP) is released from magnocellular neurosecretory cells in the supraoptic nucleus (SON) during water deprivation. AVP is also released in response to LPS‐induced systemic cytokine signals. Prostaglandin signaling plays a role in cytokine‐induced AVP release, and may be involved in other signaling pathways causing AVP release although the precise central mechanism is not well understood. To evaluate the effect of prostaglandin during water deprivation, we studied c‐Fos staining in the SON from adult male rats after water deprivation (48 h) with chronic Indomethacin (2mg/ml/hour) or vehicle minipump microinfusion intracerebroparenchymally (ICP) terminating on the dorsal border of the left SON unilaterally. After 7 days recovery, these rats were randomly assigned to groups that were either water deprived (48 h) or had access to water ad libidum. At the end of 48 hours, all rats were anesthetized and perfused for immunohistochemical analysis of c‐fos and AVP. Water deprived Rats treated with Indomethacin ICP showed increased expression of c‐fos and co‐localization of c‐fos with AVP compared to water deprived rats treated with vehicle. These results suggest that inhibition of prostaglandin production during water deprivation increased Fos staining in AVP SON neurons associated with water deprivation. (R01 HL062576 & F30 DK083884)
Neurotrophins induce NO generation in pulmonary artery endothelial cells
Authors: Meuchel Lucas W , Thompson Michael A , Pabelick Christina M , Prakash Y S
Published: June 2021

Traditionally associated with neuronal structure and function, neurotrophins (NTs; e.g. brain derived neurotrophic factor (BDNF), neurotrophin‐3 (NT3 )) and their receptors (tropomyosin related kinase; Trk) have been found in the adult lung, pulmonary artery and airway; however, their roles remain unclear. Based on previous findings of pulmonary hypertension in NT receptor knockout mice, we hypothesized that NTs induce production of nitric oxide (NO) in pulmonary endothelial cells (EC), thereby modulating pulmonary vascular tone. In human pulmonary artery EC loaded with the NO sensitive fluorescent dye DAF‐2, 50 ƒÝM ATP and both BDNF and NT3 (1 and 10 nM) acutely (<5 min) and substantially in increased fluorescence levels. Addition of the NO scavenger PTIO reversed these changes. Specificity of DAF2 for NO was tested using the short‐acting NO donor MAHMA‐NONOate, and the nitrous oxide donor Sulfa‐NONOate. Furthermore, NT‐induced elevation in NO was significantly reduced by pre‐exposure to the tyrosine kinase inhibitor K252A (100 nM, 20 min), the NOS inhibitors L‐NMMA or L‐NAME, and the Ca2+ chelator BAPTA. Acute NT exposure also increased eNOS phosphorylation. These results indicate that NT¡¦s such as BDNF and NT3 can acutely modulate endothelial NO production, and may contribute to pulmonary vasodilation.

Supported by NIH grants HL088029, (YSP), HL56470 (YSP), and Mayo Graduate School (LWM).
TNFR1 shedding by mitochondrial RISP in lung microvascular endothelium
Authors: Rowlands David John , Lindert Jens , Das Shonit , Bhattacharya Jahar
Published: June 2021

In sepsis, ligation of the endothelial (EC) TNFα receptor 1 (TNFR1) tumor necrosis factor alpha (TNFα) promotes lung inflammation. However, the role of EC TNFR1 shedding in lung inflammation is unknown. To determine real‐time, in‐situ TNFR1 dynamics and inflammation, we imaged ECs of single microvessels of inflated isolated, blood‐perfused mouse lungs by live confocal microscopy. By micropuncture, we infused microvessels with a fluorophore‐conjugated TNFR1 or E‐selectin mAb followed by buffer wash. At baseline, TNFR1 expression was stable for >1h. Following 10 min infusion of TNFα (1 ng/ml), EC fluorescence decreased by 72±3% (P<0.05 n=3) in 30 min. TNFR1 shedding was blocked in lungs from mice injected with siRNA to mitochondrial complex III Rieske Iron‐Sulphur protein (siRISP). Infusion of TNFα for 2h increased EC E‐selectin expression and leukocyte adhesion two‐fold (P<0.05). By contrast, TNFα infusion in lungs from siRISP‐mice resulted in a three‐fold increase in E‐selectin expression and leukocyte adhesion relative to control (P<0.05). To determine shedding in sepsis, we instilled mice with lipopolysaccharide (LPS 1 mg/kg, 4h). TNFR1 shedding was inhibited >50% (P<0.05). We interpret, TNFR1 ligation promotes RISP‐dependent TNFR1 shedding, possibly limiting inflammation. In sepsis, mitochondrial dysfunction may impair TNFR1 shedding thus exacerbating inflammation (support: HL57556).
TTF‐1 Regulates α5 nAChRs in Proximal Lung Epithelium During Lung Development
Authors: Willnauer Charles P , Reynolds Paul R
Published: June 2021

Nicotinic acetylcholine receptors (nAChRs) are ligand‐gated ion channels formed by five similar subunits that combine to function in signal transduction, proliferation, and apoptosis. α5 nAChRs are structural subunits detected in many non‐neuronal tissues; however, their contributions to signaling during pulmonary development are unknown. α5 was assessed by immunohistochemistry in mouse lungs from embryonic day (E)13.5 to post‐natal day (PN)10. From E15.5 to E18.5, α5 was expressed in primitive airway epithelial cells and mesenchyme. α5 expression followed the proximal‐distal axis and was detected throughout the lung at PN5. Because perinatal expression was abundant in bronchiolar epithelium, we assessed transcriptional control of α5 in Beas2B cells, a human bronchiolar epithelial cell line, by TTF‐1, a transcription factor that controls pulmonary morphogenesis. TTF‐1 significantly increased α5 transcription by acting on the α5 promoter. Site‐directed mutagenesis revealed that TTF‐1 controlled transcription by binding to specific TTF‐1 response elements. These data demonstrate that α5 is specifically controlled in a temporal and spatial manner during pulmonary morphogenesis and that it may function in differentiating pulmonary epithelial cells involved in normal organogenesis. Supported by the Flight Attendants Medical Research Institute (FAMRI, PRR) and a BYU MEG Award (PRR).
Acute intermittent hypoxia‐induced decrease in pharyngeal collapsibility requires 5‐HT2 and NMDA receptors in rats
Authors: Cao Ying , Liu Chun , Ling Liming
Published: June 2021

Long‐term facilitation (LTF) has been studied for 3 decades, yet its physiological significance is still unclear. Since LTF was present in obstructive sleep apnea (OSA) patients during sleep, LTF has been speculated to help stabilize pharyngeal airway (PA) patency in OSA patients after repeated apneas/hypopneas. We previously reported a progressive decrease in PA critical pressure (Pcrit) after acute intermittent hypoxia (AIH) and a lower Pcrit in peak inspiration (I) vs. expiration (E). We hypothesized that AIH induces a persistent decrease in PA collapsibility across the breathing cycle via LTF, and the 5‐HT2 or NMDA receptor antagonism, which blocks LTF, eliminates this collapsibility decrease. Adult male Sprague‐Dawley rats were anesthetized, vagotomized and ventilated. Genioglossal activity and Pcrit were measured in E and peak I, before and after 5 × 3‐min isocapnic 12% O2 with 3‐min 30% O2 intervals. AIH induced a progressive/persistent decrease in both E‐ and I‐Pcrit, which reached its nadir (mean: −3.7 cmH2O in E‐Pcrit and −5.9 in I‐Pcrit) at 45 min post‐AIH. Both the Pcrit decrease and LTF were eliminated by pretreatment with ketanserin (a specific 5‐HT2 antagonist, 2 mg/kg, i.v.) or MK‐801 (NMDA antagonist, 0.2 mg/kg, i.v.). These data suggest that AIH induces a persistent decrease in PA collapsibility via LTF of PA dilators, and this decrease requires 5‐HT2 and NMDA receptors. (Supported by NIH HL64912)
Microdialysis (MD) of atropine into the Kölliker‐Fuse Nucleus (KFN) alters breathing of awake and sleeping goats
Authors: Bonis Josh , Neumueller Suzanne , Marshall Brooke , Krause Katie , Kiner Tom , Smith Alex , Baogang Qian , Pan Lawrence , Forster Hubert
Published: June 2021

We MD atropine, a muscarinic receptor antagonist, at sites in the rostral pons of awake and sleeping goats to test the hypothesis that cholinergic mechanisms have site‐ and state‐dependent effects on the control of breathing. Cannula were bilaterally implanted into either rostral pontine tegmental nuclei (n = 3), the lateral (n = 3) or medial (n = 4) parabrachial nuclei, or the KFN (n = 6). After >2 weeks recovery from surgery, the goats were studied during a 45 minute period of MD with mock cerebrospinal fluid, followed by 30 minutes of recovery and 45 minutes of MD with atropine. Unilateral and bilateral MD of atropine into the KFN at night decreased pulmonary ventilation and breathing frequency and increased inspiratory and expiratory time by 12 to 14% during both wakefulness and NREM sleep. However, during daytime studies, MD of atropine into the KFN had no affect on these variables but increased the variation of genioglossus muscle activity. Nighttime unilateral and bilateral MD of atropine into the KFN increased NREM sleep by 63% (p > 0.05) and 365% (p < 0.01), respectively. MD during the day or at night into the other 3 pontine sites had only minimal effects on any variable studied. Finally, bilateral MD of atropine decreased levels of acetylcholine and choline in the effluent dialysate. Our data support the concept that the KFN is a significant contributor to cholinergically modulated control of breathing and sleep.
Enhanced Phrenic Long‐Term Facilitation Following Repetitive Acute Intermittent Hypoxia: Role of Glycolytic Flux
Authors: MacFarlane Peter M , Vinit Stéphane , Roopra Avtar , Mitchell Gordon S
Published: June 2021

Acute intermittent hypoxia (AIH) elicits a form of respiratory plasticity known as phrenic long‐term facilitation (pLTF). pLTF is enhanced by pre‐treatment with repetitive AIH (3xwAIH: 10.5% O2; 10, 5min episodes/day, 3 days/week for 4 weeks; Vinit et al. ibid), and this enhancement (metaplasticity) is associated with increased expression of key molecules necessary for pLTF (Satriotomo et al. ibid). Since cell glycolysis affects transcriptional regulation of the same key molecules (Carriga‐Canut et al. 2006), we tested the hypothesis that the glycolytic inhibitor 2‐deoxyglucose (2‐DG) prevents the metaplasticity associated with pLTF following 3xwAIH. In anesthetized rats, phrenic nerve activity was increased (ie. pLTF 47%, p<0.05) 60min post‐AIH (3, 5min episodes, 10.5% O2) and this was enhanced by pre‐treatment with 3xwAIH (110%, p<0.05). Further, the enhanced pLTF was prevented in rats that also received 2‐DG in their drinking water (80mg/kg/day) during 3xwAIH, but similar to normoxic‐treated rats (50%). Acute 2‐DG administration (240mg/kg i.p.) had no effect on pLTF indicating glycolytic flux is necessary for the metaplasticity underlying 3xwAIH‐induced pLTF. Our data suggest a novel link between glycolysis and pLTF induced by repetitive AIH and that genes regulating respiratory metaplasticity may be linked to cellular energy metabolism (NIH HL‐80209 and Francis Family Foundation).
Diaphragm and intercostal neuromuscular plasticity following C2 spinal hemisection injury (C2HS)
Authors: Gill Luther , Lee Kun‐Ze , Smith Barbara K , Vandenborne Krista , Reier Paul J , Fuller David D
Published: June 2021

C2HS transiently paralyzes the ipsilateral (IL) hemidiaphragm (HD) and induces compensatory increases in contralateral (CL) HD activity. In ongoing experiments, we are examining how chronic C2HS in adult male Sprague‐Dawley rats influences CL HD fiber size and type, and the expression of myogenic markers. Parallel experiments are quantifying the impact of chronic C2HS on inspiratory intercostal muscle electromyogram (EMG) activity. Bilateral EMG recordings from the IL and CL HD (medial costal portion) and external intercostal muscles (5th space) were obtained in urethane‐anesthetized spontaneously breathing rats at 1–60 days post‐C2HS. Diaphragm tissue was then harvested and prepared for histological and immunohistochemical evaluation. Preliminary histological analyses indicated an increase in centrally located myonuclei in CL HD myofibers and inflammatory cell infiltration by 24 hrs post‐injury. In addition, there appears to be a reduction in the relative number of type 1 myofibers in the CL HD by 48 hours post‐injury. Robust inspiratory bursting was observed in the CL intercostal EMG of all rats. IL intercostal EMG bursting was evident as early as 24 hrs post‐C2HS, whereas IL HD EMG activity was absent even as late as 14 days post‐C2HS. We conclude that the CL diaphragm begins to remodel almost immediately following C2HS, and cross spinal pathways enable IL intercostal recovery shortly after injury.

Support: NIH 1R01HD052682‐01A1, NIH T32 HD043730
Effects of topical anesthetic on the pharyngeal sensory evoked potential
Authors: Hegland Karen Wheeler , Pitts Teresa , Hegland Dustin L , Davenport Paul W
Published: June 2021

Intact sensation to the upper airways is an integral part of safe and efficient swallowing. The initiation of the pharyngeal stage of swallowing is dependent upon sensory information, largely from mechanoreceptors located in the posterior pharyngeal wall. Degradation of sensory function in that area commonly results in dysphagia (disordered swallowing) characterized by a delay in the initiation of swallowing and discoordinated motor output. It was hypothesized that application of topical anesthetic directly to the surface of the posterior pharyngeal wall would result in quantifiable changes in the pharyngeal sensory evoked potential (PSEP) waveform. Healthy volunteers between the ages of 18 and 35 participated in the study. PSEPs were measured via 32 electrode cap (10–20 system) connected to SynAmps2 Neuroscan EEG System. Paired‐pulse air puffs were delivered to the oropharynx using a thin polyethylene tube connected to a flexible laryngoscope under two conditions. Condition 1 consisted anaesthetized posterior pharyngeal wall, and in condition 2 a topical anesthetic (2% viscous lidocaine) was applied to the posterior pharyngeal wall. Anesthesia resulted in alterations in PSEP waveform, including significant decreased amplitude of the N100 PSEP peak. These results demonstrate the PSEP is mediated in part by mucosal receptors.

Research support by NIH T32‐TNCSD
Hypercapnia and resistance modulate human genioglossus motor unit activities
Authors: Richardson Patrick A. , Bailey E. Fiona
Published: June 2021

The genioglossus (GG) is considered the principle protrudor muscle of the human tongue and plays an important role in preserving airway patency during sleep. Here we report on GG whole muscle and single motor unit activities (SMU) under conditions that mimic sleep i.e., mild‐moderate elevations in CO2 (3% inspired CO2, or 1.0 L dead space) or increased airway resistance (< 10cm H2O). Fine wire and tungsten microelectrodes were inserted into the GG to record whole muscle and SMU activities in 21 subjects (18 women, 10 men; 20–55 years). The addition of 3% inspired CO2 or dead space resulted in a 200–300% increase in whole muscle GG EMG and a doubling of minute ventilation. Importantly, recordings obtained from 102 tonically discharging SMUs show no evidence of change in firing rate under any of the conditions. By comparison, phasically active SMUs (N= 10) switched their discharge pattern from inspiratory‐related to phase‐spanning in response to increased airway resistance but were not otherwise modulated by increasing respiratory drive. On this basis we conclude that, in healthy adults, the increase in the amplitude of the whole muscle GG EMG secondary to respiratory stimulation is attributable to alterations in the firing patterns of phasic motor units and to the recruitment of previously inactive tonic motor units
Nuclear Inositide Signalling: Role of PI‐PLCbeta1 in MDS and AML
Authors: Cocco Lucio , Follo Matilde Yung , Finelli Carlo , Mongiorgi Sara , Faenza Irene , Fiume Roberta , Ramazzotti Giulia , Billi Anna Maria , Martinelli Giovanni , Manzoli Lucia , Martelli Alberto Maria
Published: June 2021

The nuclear signaling evoked by phosphoinositide‐ specific‐phospholipase C (PI‐PLC)beta1 targets specific regions of Cyclin D3 as well CD24 promoter, hinting at a role in haematopoiesis, given that both Cyclin D3 and CD24 are involved in the very early steps of this process. PI‐PLCbeta1 could also play a role in the progression of Myelodysplastic Syndromes (MDS) into Acute Myeloid Leukemia (AML) since the mono‐allelic deletion of PI‐PLC beta1 is responsible in MDS patients for a higher risk of evolution to AML. Given that a single patient treated with azacitidine, a DNA methyltransferase inhibitor, displayed a direct correlation between PI‐PLCbeta1 gene expression and drug responsiveness, we hypothesized that PI‐PLCbeta1 could be a target for demethylating therapy. By quantifying the degree of PI‐PLCbeta1 methylation and gene expression in MDS patients at baseline and during azacitidine administration we found an increase of PI‐PLCbeta1 mRNA in responder patients and a reduction of promoter methylation. The molecular response correlated to and anticipated the clinical one, suggesting that PI‐PLCbeta1 gene reactivation predicts azacitidine responsiveness. Our results demonstrate for the first time that PI‐PLCbeta1 promoter is hypermethylated in high‐risk MDS patients and that the amount of PI‐PLCbeta1 mRNA predicts the clinical response to azacitidine.
Mitochondria co‐opt exercise adaptations in defense against oxidative stress in vivo
Authors: Conley Kevin , Jubrias Sharon , Siegel Michael , Syrjala Karen , van Remmen Holly , Aylward Elizabeth , Marcinek David
Published: June 2021

Reactive oxygen species (ROS) are implicated in oxidative damage but at low levels act as signals, especially in exercise. Here we show that the mitochondrial defense against ROS emulates the impact of exercise. Innovative spectroscopic tools applied to muscles in vivo found two key cell changes in a mouse model of the knockout of a key antioxidant defense, Cu,Zn‐superoxide dismutase (SOD1 −/−). These changes were paralleled in two human conditions with oxidative stress but prior to development of oxidative damage (pre‐symptomatic Huntington's disease and cancer survivors). First is an increase in mitochondrial uncoupling (reduced ATP per O2) that raises respiration. Dissipating the mitochondrial membrane potential causes uncoupling and is implicated as a negative feedback mechanism that counteracts elevated ROS but comes at the cost of greater O2 uptake. Second is a mobilization of metabolism. Uncoupling not only elevates respiration but also cellular AMP level, which increases substrate supply and activates mitochondrial biogenesis to raise oxidative capacity of muscle. Thus mitochondria are the first line of defense in response to elevated ROS with a series of compensatory cellular changes that ameliorate the impact of oxidative stress and activate cellular metabolism in a manner similar to the effect of exercise. Supported by AG028455, AR041928, AR036606, CA103728 and the CHDI Foundation.
Loss of ovarian function alters multiple aspects of lipid metabolism in adipose tissue and skeletal muscle from female mice.
Authors: Spangenburg Espen E , Campbell Kathryn M , Wohlers Lindsay M , Maher Amy C , Koves Timothy K , Bonen Arend , Muoio Deborah M
Published: June 2021

Post‐menopausal females are at risk for dyslipidemia, thus we sought to discover if surgical‐induced menopause (OVX) altered mechanisms that regulate lipid metabolism and to determine if voluntary wheel running (Ex) or 17β‐estradiol (E2) attenuated these changes. C57BL/6 mice were placed into the following groups for 8 wks: SHAM, OVX, OVX‐Ex, or OVX+E2. Visceral fat mass (VF) was significantly higher in OVX and OVX‐Ex compared to other groups, as were serum glycerol and free fatty acids indicating increased lipolytic action, which was a result of increased ATGL activation and reduced perilipin expression in VF. The increased lipolysis resulted in ectopic lipid deposition in skeletal muscle (SM), which was associated with increased FAT/CD36 expression in the OVX compared to the SHAM, but exercise or E2 attenuated the increase. Metabolic profiling of SM found OVX animals exhibit lower levels of short chain acyl‐cartinine species compared to SHAM, which was prevented by exercise or E2. Citrate levels were elevated in all OVX mice compared to SHAM animals, with minimal differences in other organic acids. Finally, decreased expression of critical proteins in the electron transport chain was detected in OVX compared to all other groups. Reductions in ovarian function resulted in significant alterations in regulatory mechanisms in multiple tissues that contribute to the metabolic syndrome in post‐menopausal females.
Electrical pulse stimulation induces contraction and oxidative modification of proteins in cultured C2C12 myotubes
Authors: Zachwieja Jeffrey J , Gimi Khursheed , Mohammed Safi
Published: June 2021

Skeletal muscle cells produce free radicals which are believed necessary for effective muscle contraction. However, when a heightened free radical generation creates a redox imbalance, oxidative modification of contractile proteins may contribute to fatigue. We have pursued a cell culture model that allows us to quantify oxidative modification of contractile proteins. C2C12 myoblasts were grown to 90% confluence and differentiated into mature myotubes. Western blot analysis for myosin heavy chain (MHC) protein indicated expression by day five and maintenance of protein levels through day eight of differentiation. Electrical pulse stimulation (EPS) of myotubes on day five of differentiation produced visible, repetitive contraction of cells. A pulse frequency of 0.5 hz and duration of 24 ms for 90 minutes resulted in a 3.65 ± 0.74 fold increase in oxidative modification of MHC protein (six independent experiments). Oxidative modification of MHC protein was tempered (42 ± 15% of EPS alone) when cells were pre‐ and co‐incubated (during EPS) with 1mM Trolox (five independent experiments). This in vitro model shows promise for quantifying contraction induced oxidative modification of proteins in mature C2C12 myotubes. Further, this model could be used to develop knowledge of which nutritional antioxidants might prevent a redox imbalance in contracting skeletal muscle and thereby delay the onset of fatigue.
Consecutive trimix diving is associated with high incidence of gas bubbles arterialization
Authors: Ljubkovic Marko , Marinovic Jasna , Obad Ante , Breskovic Toni , Brubakk Alf O , Gaustad Svein Erik , Dujic Zeljko
Published: June 2021

SCUBA diving is often associated with generation of venous gas bubbles (VGB) that occur during ascent and are eliminated in lungs. Some conditions, such as patent foramen ovale (PFO), bear the risk for arterialization of VGB. However, these events are rather rare in air diving protocols that adhere to standardized diving tables. The aim of this study was to examine whether VGB arterialization can be found at rest following consecutive dives with trimix (mixture of oxygen, helium and nitrogen), which is increasingly being used among divers. Seven male divers performed three dives in consecutive days with diving depths ranging from 63–65 m. VGB were monitored by ultrasound for 90 minutes after surfacing and graded on a scale from 0–5. These profiles produced a significant number of VGB. Furthermore, the arterialization of VGB was detected in 5/7 divers (71%) and in 8/21 dives (38%), with only one subject having detected PFO. Additionally, mean pulmonary artery pressure was significantly increased after each dive. The arterialized bubbles did not evoke any symptoms (or decompression sickness) in any subject. These data indicate that even conservative trimix diving is associated with high incidence of gas bubbles arterialization which, although acutely asymptomatic, requires caution and investigation of potential long term consequences.

Supported by the Croatian Ministry of Science and Unity through Knowledge Fund.
Cross‐sectional Analysis of Cardiometabolic Phenotypes in Men of Varying Body Composition and Training Status
Authors: Lee Mary M , Croymans Daniel M , Krell Shannon L , Harris Ryan A , Roberts Christian K
Published: June 2021

Studies indicate that being overweight per se does not necessarily equate to being metabolically unhealthy. Utilizing a cross sectional design, we are investigating cardiometabolic differences between young men of differing body composition and training status. 9 lean trained (LT, BMI <25 kg/m2, 4+ d/wk resistance training) and 15 overweight untrained (OU, BMI>27 kg/m2) subjects were assessed for waist circumference (WC), body composition by DXA, 1‐repetition maximum (1‐RM) strength, physical activity by questionnaire (PAQ), blood pressure, carotid‐femoral pulse wave velocity (cfPWV), augmentation index (AIx), aortic pressure, and sub‐endocardial viability ratio (SEVR). LT subjects had lower WC and trunk/total fat mass (p<0.0001), but no difference in lean body mass (LBM) compared to OU. OU subjects exhibited trends for higher systolic (p=0.10), diastolic (p=0.03) and aortic (p=0.09) pressure, and lower SEVR (p=0.02). No differences in AIx or cfPWV were noted between groups. PAQ confirmed that LT subjects were more physically active than OU subjects (p<0.0001). LT subjects exhibited significantly greater 1‐RM strength for bench press/seated row (p<0.03), but not leg press (p=0.7). These data indicate select phenotypes vary between men exhibiting different body composition and training status. Whether improved metabolic health is dependent on fitness, rather than BMI or LBM requires further study.
Limb position affects magnitude of reactive hyperemia
Authors: Clifford Philip S , Jasperse Jeffrey L , Shoemaker J Kevin
Published: June 2021

Several studies have reported a greater blood flow response to contractions when the limb is in the dependent compared to the independent position. These results have been interpreted as evidence for a skeletal muscle pump contribution to exercise hyperemia. An alternative explanation is that there are positional differences in myogenic tone and that a given stimulus has a greater effect when the myogenic tone is enhanced. We hypothesized that the magnitude of reactive hyperemia would be greater with the limb in the dependent position. Ten healthy volunteers of both sexes participated in the study. Brachial blood flow was measured by Doppler ultrasound and blood pressure measured by Finapres. The subjects lay supine with one arm supported in two different positions – above and below the heart. Reactive hyperemia was produced by occlusion of the arterial inflow with a blood pressure cuff inflated to 200mmHg for varying durations − 0.5 min, 1 min, 2 min, 5 min in randomized order.

The peak increases in blood flow were 77±11,178±24, 291±25, 398±33 ml/min above the heart and 96±19, 279±62, 550±60, and 711±69 ml/min below the heart (p<0.01). These results show that a standard stimulus (reactive hyperemia) elicits different responses depending on limb position. Furthermore, the results suggest the need to reevaluate studies employing positional changes to examine muscle pump influences on exercise hyperemia.
Retinal and choroidal blood flow responses to dynamic and static exercise in humans
Authors: Ikemura Tsukasa , Someya Nami , Hayashi Naoyuki
Published: June 2021

Retinal and choroidal blood flows may be important to maintaining the visual function during exercise because eyesight is impaired when they are reduced. We examined the responses of the retinal and choroidal blood flows to incremental cycling and static hand griping. The retinal and choroidal blood flows and the heart rate (HR) were measured in nine subjects during a resting baseline and exercise. Retinal blood flow was measured for 4 s twice a minute by using laser speckle flowmetry. The intensity of cycling exercise was increased by 30 w every 3 minutes. Blood flow data obtained during the cycling exercise were categorized according to HR (light, <100 bpm; moderate, 100–120 bpm; and heavy, >120 bpm). The retinal and choroidal blood flow increased with increasing exercise intensity of cycling exercise by 16±8, 32±13, and 40±19 % (mean±SE) from the resting baseline during light, moderate, and heavy exercise, respectively. Hand‐grip exercise at 30 % MVC for 2 minutes increased the retinal and choroidal blood flows from the resting baseline by 20±5 %. These findings suggest that the retinal and choroidal blood flows are increased by dynamic and static exercise. (Grant of Yamaha Motor Foundation)
Effect of 3, 6, and 12 wks Voluntary Exercise on Renal Endothelial Enzymes
Authors: Moningka Natasha , Ahlgren Joslyn , Hayward Linda , Baylis Chris
Published: June 2021

Exercise (EX) markedly reduces renal blood flow (RBF) which could also reduce the shear stress induction of the nitric oxide (NO) generating enzyme, endothelial NO synthase (eNOS), and the antioxidant, extracellular superoxide dismutase (EC SOD). The duration of EX training may also play a role. Therefore, we investigated the impact of EX duration on eNOS and EC SOD abundance in the kidney cortex (KC). Male Sprague Dawley rats were given 24 hr access to voluntary wheel running for 3, 6, or 12 wks, or remained sedentary (SED). Running activity was low intensity and comparable during the first 3 wks for all groups in that there was a steady increase in avg. total distance run from week 1, 2, and 3 (representative activities: 0.9±0.31, 2.1±0.68, and 4.0±1.3 km/day, respectively), and remained ~3–5 km/day over the next 9 wks. KC abundance of eNOS and EC SOD were unchanged with 3 wks EX, but significantly decreased by 6 and 12 wks (Table; *p<0.05 vs. SED). The duration/intensity of EX is important since during the first 3 wks of voluntary EX, where running activity was increasing, there were no changes in KC eNOS or EC SOD. By 4 wks, running reached a maximum value and plateaued (~5 km/day), and by 6 and 12 wks there were significant reductions in KC eNOS and EC SOD. The falls in eNOS and EC SOD are predictable based on the presumed reductions in RBF. Our data suggest that the duration of EX plays a critical role in dictating the kidney's response of eNOS and EC SOD abundance to EX. Further study is required to determine the long term impact of EX on kidney function and structure in health and disease.

KC eNOS
KC EC SOD

n
Arbitrary Units
Arbitrary Units

3 wk

SED
3
1.2±0.2
3.2±0.9

EX
3
1.2±1.1
6.7±3.7

6 wk

SED
8
25±1.7
21±3.2

EX
12
18±2.8*
17±5.3*

12 wk

SED
6
64±2.6
13±1.0

EX
6
56±2.2*
8.0±0.7*
Effects of Exercise Training on Biomarkers of Endothelial Function and Inflammation in Coronary Artery Disease Patients
Authors: Ribeiro Fernando , Alves Alberto J , Teixeira Madalena , Miranda Fátima , Duarte José A , Oliveira José
Published: June 2021

Purpose

to assess the effects of exercise training on biomarkers of endothelial function and inflammation.

Methods

47 patients after acute myocardial infarction were randomized to an exercise‐training group (ETG) receiving an 8‐week aerobic exercise programme (3× per week) or to a control group (CG) receiving usual care. At baseline and after 8 weeks the circulating levels of soluble intercellular adhesion molecule‐1 (sICAM‐1) and vascular cell adhesion molecule‐1 (sVCAM‐1), C‐reactive protein (CRP), interleukin (IL)‐6 and ‐10 were assessed.

Results

ETG increased the circulating levels of IL‐10. Conversely, CG did not change the inflammatory biomarkers, but increased the endothelial dysfunction (Table 1).

Changes in the inflammatory and endothelial function biomarkers [median (percentile 25th–75th)]

ETG
CG

Baseline
Final
Baseline
Final

CRP (mg/L)
1.1 (0.5–2.2)
1.4 (0.5–2.4)
0.9 (0.5–1.7)
0.9 (0.7–1.9)

IL‐6 (pg/mL)
2.5 (1.6–3.2)
3.13 (2.1–5.0)
3.6 (1.7–6.5)
3.5 (2.8–4.7)

IL‐10 (pg/mL)
5.8 (2.6–9.1)
6.36 (4.1–14.7)†
7.7 (4.4–17.2)
7.3 (2.9–10.2)

sICAM‐1 (ng/mL)
169 (143–209)
187 (154–201)
180 (147–219)
206 (169–242)†

sVCAM‐1 (ng/mL)
297 (223–377)
340 (269–418)
245 (179–304)
341 (231–424)†

Different from baseline, P<.05

Conclusions

Exercise‐training revealed an anti‐inflammatory effect, expressed by the IL‐10 increase, and counteracted the endothelial function deterioration.
Spina bifida, obesity and health: A case study
Authors: Vanderbom Kerri Ayame , Azevedo John L. , Taylor Anne , Anderson Tanja , Gorter Sandy
Published: June 2021

The purpose of the study was to assess the effects of exercise training on trained subjects with spina bifida (TSB) compared to untrained SB subjects (UTSB).

Peak power output (POpeak) and VO2peak were assessed using arm ergometry. Body composition was assessed using dual x‐ray absorptiometry. Glucose tolerance was determined using an oral glucose tolerance test (OGTT) after an overnight fast.

VO2peak was 33% greater in male TSB vs. UTSB (30.8 and 20.6 ml/kg/min in TSB and UTSB). Female TSB VO2peak was 43% higher in TSB compared to UTSB (24.9 and 14.2 ml/kg/min in TSB and UTSB). POpeak was 70W in the male TSB vs. 62W in the UTSB (12% increase). Female TSB, POmax was 19% greater than UTSB (60 and 48.9W). Body fat percentage was 26.6% and 36% in male TSB and UTSB. Body fat percentage was 29 and 49% in female TSB and UTSB. Fasting blood glucose in TSB was 89.5 mg/dl which is comparable to UTSB (Widman 2007).

We conclude that individuals with SB respond positively to exercise training as indicated by increased VO2peak, maximum power output, and decreased body fat percentage. Cardiovascular disease is the leading cause of death for people with spinal cord dysfunction. Additionally, metabolic dysfunction is abnormally prevalent in this population. Regular exercise should be emphasized in this population. Further research is needed. Results from this study should be taken with caution due to the small sample size.
Post‐exercise massage affects skeletal muscle gene expression
Authors: Crane Justin , Ogborn Daniel , Cupido Colleen , Melov Simon , Hubbard Alan , Tarnopolsky Mark
Published: June 2021

Massage therapy is commonly prescribed for individuals that suffer from chronic pain, inflammation, or musculoskeletal injury. Despite the widespread belief that massage augments muscle repair and reduces inflammation, there is little objective, scientific evidence to support its practice. Therefore, the purpose of this study was to evaluate the molecular effects of massage following a single unaccustomed bout of exercise. Eleven recreationally active, healthy males (age 22±1 yrs, VO2peak 46±2 ml·kg−1·min−1) volunteered to participate in this study. Each subject completed an exhaustive endurance cycling protocol. After 15 mins of recovery, one quadricep was randomly chosen for 10 mins of massage (MASS) and the contralateral leg served as a control (CON). Muscle biopsies were acquired from the vastus lateralis at rest, immediately following massage, and 2.5h after massage was administered. Histology revealed that exercise induced significant muscle damage from rest at 2.5h (P<0.05), however there was no effect of massage (P>0.05). No differences were seen between CON or MASS in the oxidative stress markers 4HNE or protein carbonyls at any timepoint (P>0.05). Gene microarray analysis displayed 4 genes that were differentially expressed (P<0.05) for MASS vs CON immediately following massage as well as 11 genes at 2.5h that relate to pathways of inflammation and cellular remodeling. In summary, these data provide evidence that massage stimulates molecular events that may justify its use in the remediation of muscle injury. (Supported by NSERC Canada).
Role of the PAG in the Exercise Pressor Reflex during Varying Intensity of Activity
Authors: Basnayake Shanika Deshani , Green Alexander L , Aziz Tipu Z , Paterson David J
Published: June 2021

Emerging evidence reports that the periaqueductal grey (PAG) in humans could be a major site for controlling the cardiovascular response to exercise. We previously hypothesised that the PAG is part of the subcortical neurocircuitry involved in the exercise pressor reflex. It is well known that as exercise intensity increases, the magnitude of the elevation of blood pressure from resting levels also increases. In order to identify whether the PAG has a role in controlling the magnitude of this increase, we assessed the spectral changes in local field potentials (LFPs) recorded from both the PAG and the thalamus in a patient who had undergone neurosurgery for the implantation of deep brain stimulating electrodes for the treatment of chronic pain. The patient was asked to perform light exercise (bicep curls), followed by arterial occlusion of the exercised limb in order to artificially stimulate the pressor response. The protocol was performed with a 2kg weight attached to the patient's wrist, and was then repeated with a 4kg weight. The PAG was compared to the thalamus i.e. the control area. The PAG showed significant increases in LFP power at frequencies from 4–12Hz (p<0.001) during occlusion following both 2kg exercise and 4kg exercise. However, in this case study, there did not appear to be a direct relationship between exercise intensity and neural activity. No change in thalamus activity was observed during occlusion.
Carotid chemoreceptor modulation of muscle blood flow during leg‐extension exercise in healthy humans
Authors: Stickland Michael K , Schulte Felix , Haykowsky Mark J , Paterson Ian , Ezekowitz Justin , McMurtry Michael Sean
Published: June 2021

Previously, we have shown that transient carotid chemoreceptor (CC) inhibition causes vasodilation in limb muscle in exercising dogs, and a reduction in muscle sympathetic nerve activity during handgrip exercise in humans. The purpose of the present investigation was to determine if CC inhibition causes an increase in exercising muscle blood flow during leg‐extension exercise in humans. Healthy subjects (N = 5) breathed hyperoxic gas (FIO2 = 1.0) for 2 minutes at rest and during submaximal one‐legged knee‐extension exercise. Femoral arterial blood flow data was obtained from continuous Doppler recordings at rest and during exercise. Leg‐extension exercise increased heart rate (64 vs. 87 beats · min−1), mean blood pressure (84 vs. 96 mmHg), muscle blood flow (0.37 vs. 1.60 L · min−1) and muscle conductance (4.75 vs. 16.82 units). Transient hyperoxia had no effect on muscle blood flow or conductance at rest. In contrast, during exercise both muscle blood flow and muscle conductance were increased with hyperoxia. The mean peak increase in muscle blood flow and conductance was 30 +/− 6% and 30 +/− 8%, respectively, above steady state normoxic values. Blood pressure was unchanged with hyperoxia at rest or during exercise. These preliminary findings suggest that the CC plays a role in muscle blood flow control during exercise in healthy humans.
Either PVN or RVLM injections of adeno‐associated virus‐siRNA to silence estrogen receptor β (ERβ) produces augmentation of aldosterone/NaCl‐induced hypertension in female rats
Authors: Xue Baojian , Beltz Terry G. , Johnson Ralph F. , Guo Fang , Hay Meredith , Johnson Alan Kim
Published: June 2021

Previous studies have shown that icv injections of recombinant adeno‐associated virus (AAV) carrying small interference (si) RNA to silence either ERα (AAV‐siRNA‐ERα) or ERβ (AAV‐siRNA‐ERβ) augments aldosterone (ALDO)‐induced hypertension (HT) in female rats. The present study investigated regional specificity of different ER subtypes in the protective actions of estrogen in the brain. Blood pressure was measured in female rats with the use of telemetry implants. ALDO (750 ng/h) was administered s.c. via osmotic pump and 1% NaCl was provided for drinking. At the same time, PVN or RVLM injections of AAV‐siRNA‐ERα, AAV‐siRNA‐ERβ or scrambled siRNA (AAV‐siRNA‐SCM) were used to knock down ERα and ERβ subtypes. Either PVN or RVLM injections of AAV‐siRNA‐ERβ augmented ALDO‐induced HT (Δ14.9±0.8 mmHg, n=4 and Δ15.4±2.7 mmHg, n=4, respectively). However, rats with PVN or RVLM injections of AAV‐siRNA‐ERα did not significantly increase blood pressure induced by ALDO (Δ9.8±0.7 mmHg, n=4 and Δ8.1±2.9, n=4, respectively) in comparison to AAV‐siRNA‐SCM rats (Δ6.2±1.8 mmHg, n=3 and Δ7.7±0.4 mmHg, n=3, respectively). These data indicate that both PVN and RVLM ERβ, but not ERα in these nuclei, contribute to the protective effects of estrogen against ALDO‐induced HT. The brain regions responsible for the protective effects of estrogen interaction with ERα in the development of ALDO‐induced HT still need to be determined.
Rostral ventrolateral medullary (RVLM) but not medullary lateral tegmental field (LTF) neurons are in the pathway mediating sympathoexcitatory (SE) responses elicited by activation of cardiac and splanchnic sympathetic afferents
Authors: Barman Susan M , Orer Hakan S
Published: June 2021

The LTF is involved in mediating sympathetic responses to activation of baroreceptor, arterial chemoreceptor, and vagal afferents but not trigeminal or sciatic afferents (Orer et al, Am J Physiol 286: R451‐64, 2004). In the current study, we tested the hypothesis that the LTF is an element of the sympatho‐sympathetic reflex pathway. We studied the effects of blockade of NMDA or non‐NMDA receptors bilaterally in the LTF on the area under the curve of the computer‐averaged SE potential in the right inferior cardiac nerve elicited by trains of stimuli applied at 0.5 Hz to afferents in left inferior cardiac and splanchnic nerves (lCN, lSN) of Dial‐urethane anesthetized cats. SE responses to lCN stimulation were unchanged by microinjection of either D‐AP5 (101±5% of control; n = 5) or NBQX (98±8% of control; n = 5). Responses to lSN stimulation were similarly unaffected: 92 ± 4 (n = 6) and 90 ± 5 (n = 4) % of control after D‐AP5 and NBQX. Thus, LTF is not a part of these reflex pathways. However, microinjection of NBQX into RVLM significantly (P ≤ 0.05) reduced SE responses to stimulation of lCN (37± 11% of control; n = 6) and lSN (35 ± 11 % of control; n = 5). D‐AP5 microinjection into RVLM did not significantly effect SE responses to stimulation of lCN or lSN (79 ± 13 and 72 ± 17 % of control; n = 5 each). These data show that activation of non‐NMDA receptors in RVLM contribute to SE responses to activation of sympathetic afferents. (Supported by HL33266)
Increased intrinsic excitability of muscle vasoconstrictor sympathetic preganglionic neurones in neonatal spontaneously hypertensive rats
Authors: Paton Julian FR , Stalbovskiy Alexey O , Pickering Anthony E
Published: June 2021

Young, spontaneously hypertensive (SH) rats show an increased level of sympathetic activity that predates the development of hypertension (Simms et al 2009 J Physiol).

We have examined the properties of muscle vasoconstrictor sympathetic preganglionic neurones (MVC‐SPN) in neonatal SH and Wistar rats. Whole‐cell recordings were obtained from SPN (Wistar n=169, SH n=76; aged p9–14) in T3–4 segment of the working heart‐brainstem preparation.

SPN of SH rats showed a higher firing frequency (1.7 vs 3.0Hz) and smaller AHP amplitude. When analysed by functional subgroup it was apparent that these difference were secondary to changes in the excitability of MVC‐SPN. These showed significantly higher firing frequencies (2.2 vs 3.5Hz) with increased respiratory modulation. Additionally, the SH MVC‐SPN had shorter, smaller AHPs, lower input resistances and a weaker transient rectification (IA).

Voltage clamp analysis of spontaneous excitatory synaptic events in MVC‐SPN showed similar frequencies and amplitudes of EPSCs. There was a modest preponderance of large EPSCs in SH rats (>30pA, <0.3Hz) which alone did not account for the increased spike discharge.

In summary, the MVC SPN of neonatal SH rats are intrinsically more excitable. These changes occur prior to, and may play a causal role in, the development of hypertension.