bluuebunny/crossref_metadata_2025 huggingface dataset:
Characteristics of Mucosal Intermediate Conductance K+ (KCNN4) Channels in rat intestinal epithelial IEC18 cells
Authors: Rajendran Vazhaikkurichi M , Wonderlin William F
Published: June 2021

Although KCNN4‐like proteins are present in both mucosal and serosal membranes, patch clamp studies have characterized KCNN4 channels only in the serosal membranes of intestinal epithelial cells. Patch clamp recordings made from inside out patches excised from the exposed surface of IEC18 monolayer grown on permeable supports were used to characterize mucosal KCNN4 channels. The bath solution contained (in mM) 140 K‐gluconate, 1 Ca‐acetate, 2.5 Mg‐acetate, 10 glucose and 10 HEPES‐Tris (pH 7.2). The pipette solution was of similar composition, but with free [Ca2+] buffered to 50 nM with EGTA. Apamin and Iberiotoxin were added to the pipette solution to block SK and maxiK K+ currents, respectively. In symmetric K+, the single channel currents were inwardly rectifying with a slope conductance at negative potentials of about 38 pS. Substitution of Na+ for K+ in the bath shifted the reversal potential to more negative potentials indicating that the current was selective for K+ over Na+. The currents were completely inhibited by 1 μM clotrimazol added to the bath. We conclude from the physiological and pharmacological properties of this current that an intermediate conductance, Ca2+‐activated K+ current is present in IEC18 cells. Furthermore, the presence of this current in patches excised from the exposed surface of a monolayer leads us to surmise that this current is present in the mucosal membranes.
EGF and its related growth factors mediate sodium transport in mpkCCDc14 cells via ErbB2 (neu/HER‐2) receptor
Authors: Zheleznova Nadezhda N , Levchenko Vladislav , Pavlov Tengis S , Vandewalle Alain , Wilson Patricia D , Staruschenko Alexander
Published: June 2021

Amiloride‐sensitive sodium entry, via the epithelial sodium channel (ENaC), is the rate‐limiting step for Na+ absorption. Epidermal growth factor (EGF) is involved in the regulation of Na+ transport and ENaC activity. However it is still controversial exactly how EGF regulates ENaC and Na+ absorption. The aim of the present study was to characterize the EGF regulation of Na+ transport in mpkCCDc14 cells. EGF dose dependently regulates basal transepithelial Na+ transport in two phases: an acute phase (< 4 hrs) and a chronic phase (> 8 hrs). Similar effects were observed with TGF‐α, HB‐EGF and amphiregulin. Inhibition of MEK1/2 by PD98059 or U0126 increased acute effects and disrupted chronic effects of EGF on Na+ reabsorption. Inhibition of PI3‐kinase with LY294002 abolished acute effect of EGF. As assessed by Western blotting, ErbB2 is the most predominant member of the ErbB family detected in mpkCCDc14 cells. Immunohistochemistry analysis revealed localization of ErbB2 in the CCD in rat kidneys. Both acute and long term effects of EGF were abolished when cells were treated with tyrphostin AG‐825, a selective inhibitor of the ErbB2 receptor. Thus, we conclude that EGF and its related growth factors are important for maintaining transepithelial Na+ transport and that EGF biphasically modulates sodium transport in mpkCCDc14 cells via the ErbB2 receptor.

Supported by AHA and ASN.
Activation of the epithelial Na channel (ENaC) in the collecting duct by vasopressin contributes to water reabsorption
Authors: Bugaj Vladislav , Pochynyuk Oleh , Stockand James D
Published: June 2021

We used patch clamp electrophysiology on isolated, split‐open murine collecting ducts (CD) to test the hypothesis that regulation of ENaC activity is a physiologically important effect of vasopressin. Surprisingly, this has not been tested directly before. We ask whether vasopressin affects ENaC activity distinguishing between acute and chronic effects, as well as, parsing the cellular signaling pathway and molecular mechanism of regulation. In addition, we quantified possible synergistic regulation of ENaC by vasopressin and aldosterone associating this with a requirement for distal nephron Na+ reabsorption during water conservation versus maintenance of Na+ balance. We find that vasopressin significantly increases ENaC activity within 2–3 minutes by increasing open probability (Po). This activation was dependent on adenylyl cyclase (AC) and PKA. Water restriction (18–24 hrs.) and pre‐treatment of isolated CD with vasopressin (~30 min.) resulted in a similar increase in Po. In addition, this also increased the number (N) of active ENaC in the apical membrane. Similar to Po, increases in N were sensitive to inhibitors of AC. Stressing animals with water and salt restriction separately and jointly revealed an important effect of vasopressin: Conservation of water and Na+ each independently increased ENaC activity and jointly had a synergistic effect on channel activity. These results demonstrate a quantitatively important action of vasopressin on ENaC suggesting that distal nephron Na+ reabsorption mediated by this channel contributes to maintenance of water reabsorption. In addition, our results support that the combined actions of vasopressin and aldosterone are required to achieve maximally activated ENaC.
Mapping an inhibitory peptide binding site to construct a molecular model of the alpha subunit of the epithelial sodium channel
Authors: Kashlan Ossama B. , Boyd Cary R. , Argyropoulos Christos , Okumora Sora , Hughey Rebecca P. , Grabe Michael , Kleyman Thomas R.
Published: June 2021

The epithelial Na+ channel (ENaC) facilitates transepithelial Na+ transport in several tissues to regulate extracellular fluid volume and airway surface liquid volume. The channel is assembled from three homologous subunits with the bulk of each protein's mass found in the extracellular domains. We previously showed that two of these subunits are cleaved at multiple sites, resulting in channel activation due to the release of inhibitory tracts. Synthetic peptides based on these tracts inhibit the channel. We sought to define the binding site for the alpha‐subunit derived peptide by systematically mutating large stretches of ENaC and assaying for channel inhibition. Here we present molecular models constructed using distance based restraints derived from our data in conjunction with restraints derived from the closely related protein acid sensing ion channel 1. Our data show that the inhibitory peptide binds to the so‐called finger and thumb domains of ENaC. Our models suggest that the interface between the thumb and finger domains is critical to the control of channel gating.
Bronchial Epithelial Dysfunction In Asthma: Similarities To Metabolic Syndrome
Authors: Agrawal Anurag , Ahmad Tanvir , Mabalirajan Ulanganathan , Joseph Duraisamy Arul , Ghosh Balaram
Published: June 2021

Objective

Obesity and metabolic syndrome are epidemiologically associated with incident and prevalent asthma. To understand its mechanisms, we determined whether bronchial epithelial dysfunction in asthma is associated with metabolic stress.

Methods

We investigated the occurrence of oxidative stress, disordered arginine and nitric oxide metabolism, mitochondrial health and epithelial injury in lungs of mice with allergic airway inflammation. We further determined whether strategies known to be effective against similar dysfunction in metabolic syndrome, i.e. L‐arginine supplementation or statin therapy, are efficacious in the asthma model.

Results

Increased levels of asymmetric dimethyl arginine (ADMA), an endogenous arginine analog that uncouples NOS, were found in asthmatic lungs. This was positively correlated with oxo‐nitrative stress, mitochondrial dysfunction, and epithelial injury. Treatment with either L‐arginine or simvastatin was able to restore normal ADMA and nitric oxide metabolism. This was associated with reduction of oxo‐nitrative stress, improved mitochondrial health, as well as attenuation of bronchial airway injury, remodeling, and hyperresponsiveness.

Conclusion

Asthmatic airways show patterns of metabolic stress similar to vascular dysfunction in metabolic syndrome, and respond to treatment with L‐arginine or simvastatin.
Acute and selective activation of pulmonary neuroepithelial bodies by mild hypo‐osmotic stimuli
Authors: Lembrechts Robrecht , Brouns Inge , Schnorbusch Kathy , Pintelon Isabel , Timmermans Jean‐Pierre , Adriaensen Dirk
Published: June 2021

Neuroepithelial bodies (NEBs) are morphologically well‐defined airway receptors composed of densely innervated groups of neuroendocrine cells. Besides other functions, NEBs have been proposed as transducers of mechanical changes in the airways. So far, however, physiological data are lacking. Hypo‐osmotic solutions cause cell swelling that will likely increase pressure in the tight junction sealed airway epithelium and more specifically in the NEB microenvironment. This study aimed at finding out whether NEBs are sensitive to hypo‐osmotic stimuli.

Mouse lung vibratome slices were used for confocal live cell imaging of pulmonary NEBs. Short term (30s) perfusion with a hypo‐osmotic solution (230 mOsm) of lung slices loaded with the Ca2+ indicator Fluo‐4 showed a fast reversible Ca2+ rise in NEB cells, dependent on extracellular Ca2+, and a typical delayed activation of the shielding Clara‐like cells. All other airway epithelial cells, which in contrast to NEBs abundantly express hypo‐osmosensitive TRP channels, appeared to show a Ca2+ rise only at osmolarities lower than 200 mOsm, suggesting different signalling mechanisms.

The first physiological evidence is provided for direct activation of NEBs by mild acute hypo‐osmotic stress that potentially mimics mechanical stimulation.

Support: IWT fellowship SB/81162 (R.L); FWO grant G.0081.08 (D.A.); UA grants GOA BOF 2007 (D.A.) and KP BOF 2006 (I.B.)
ATP promotes Plasma Membrane Wound Repair by a P2Y2R dependent Mechanism
Authors: Belete Hewan A , Hubmayr Rolf D
Published: June 2021

Cell wounding and repair are important drivers of the innate immune response of ventilator‐injured lungs. Cells repair plasma membrane (PM) wounds by several mechanisms including non‐secretory exocytosis and it is therefore not surprising that extra‐cellular ATP, a secretagogue, enhances PM repair. Neither the responsible purinergic receptor sub‐type nor the downstream signaling pathways have been identified.

Expression of P2Y2R in A549 cells was validated by immunocytochemistry and immunoblot experiments using anti‐P2Y2R (Chemicon). Confluent A549 cells were incubated with the P2Y2 antagonist Suramin (400μM), ATP (50ìM) or ATP hydrolase Apyrase (20U/ml) and stretched by 30% at 8 cycles/min for 5 min. 2 min later, the cells were labeled with Propidium Iodide (PI; 4μl/ml), trypsinized and subjected to flow cytometry. PI + cells were considered wounded and necrotic. Pretreatment of A549 cells with Suramin showed a significantly higher fraction of PI + cells compared to controls (47 ± 9 % vs 22 ± 5%, p<0.05), while the addition of extracellular ATP appeared to promote PM wound repair (6± 1%, p<0.01). In contrast, pretreatment with apyrase did not significantly alter the number of necrotic cells (26 ± 6%)

Our results suggest that ATP promotes PM wound repair by a P2Y2R dependent mechanism. The Apyrase data raises the possibility that ATP metabolites may also modulate PM repair.

Support HL63178
Damage‐associated molecular pattern markers are triggered by pulmonary nanotube exposure
Authors: Herndon Betty L , Patel Aalok , Quinn Tim , Nalvarte‐Kostoryz Elisabet , Fibuch Eugene
Published: June 2021

Nanoparticle exposure by accidental inhalation is increasing due to broad use in consumer and industrial products. We demonstrated a rapid eosinophilia following acute pulmonary exposure to long single wall carbon nanotubes (SWCNT). With the hypothesis that SWCNT are creating damage‐associated molecular patterns (DAMPs) in response to pulmonary exposure, 15 rats were intratracheally given either 50 μL surfactant containing 500 μg/mL SWCNT or surfactant. Sterility was determined by limulus lysate assay. Bronchoalveolar lavage (BAL), serum and tissue were harvested acutely (0.5 – 24 hr) or subchronically (1–4 wk). DAMP‐related proteins (high mobility box protein‐1 HMGB1 and heat shock protein‐70 HSP70), a receptor (RAGE), and TNFα were measured. BAL DAMP molecules and TNFα were elevated acutely vs subchronically (p=0.02) with HMGB1 and TNFα peaking at 30 min (34.7 and 36.7 pg/mL respectively, 4 times the surfactant controls). A robust lung tissue eosinophilia, 20 cells per field at 400x, was also seen at 30 min. RAGE receptors were widely upregulated in tissue as determined by immunostaining, strong at 24 hours. At 1–4 weeks granulomas were seen around particle clusters visible by light microscopy, and DAMP molecules and TNFα decreased in BAL to ~1/3 the acute titers. All markers increased again at 4 weeks, suggesting macrophage necrosis and secondary SWCNT release.

Funding: St. Luke's Foundation, Kansas City
Diesel Particulate Matter Induces Receptor for Advanced Glycation End‐Products (RAGE) Expression in Alveolar Epithelial Cells and Mediates an Inflammatory Response
Authors: Wasley Karisa M , Allison Camille H , Reynolds Paul R
Published: June 2021

Receptors for advanced glycation end‐products (RAGE) are members of an immunoglobin superfamily of cell‐surface receptors expressed in alveolar type I (ATI) epithelial cells. RAGE has also been implicated in mechanisms of sustained pulmonary inflammation. In the present study, we test the hypothesis that diesel particulate matter (DPM) up‐regulates RAGE in rat ATI‐like R3/1 cells and induces an inflammatory response. Using real time RT‐PCR and immunoblotting, we demonstrate that RAGE mRNA and protein are up‐regulated in R3/1 cells exposed to DPM. Immunostaining and reporter gene assays revealed increased nuclear translocation and activity of NF‐kB in DPM‐exposed R3/1 cells when compared to cells transfected with small interfering RNA for RAGE (siRAGE) prior to DPM exposure. Lastly, ELISA revealed that two inflammatory cytokines, MCP‐1 and Il‐8, were significantly decreased in DPM‐exposed R3/1 cells that incorporated siRAGE when compared to cells without siRAGE. These data offer novel insights into potential mechanisms whereby RAGE influences pulmonary inflammation exacerbated by DPM exposure. Further research may demonstrate that molecules involved in RAGE signaling are potential targets in the successful pharmacological treatment of inflammatory lung diseases. Supported by the Flight Attendants Medical Research Institute (FAMRI, PRR) and BYU MEG Award (PRR).
The PI 3‐kinase/Akt pathway plays a role in the trafficking of the surfactant protein‐A (SP‐A) receptor P63 (CKAP4) to the cell surface of type II pneumocytes
Authors: Bates Sandra R. , Tao Jian‐Qin , Feinstein Sheldon I. , Zhang Li , Fisher Aron B. , Kazi Altaf S.
Published: June 2021

P63 (CKAP4), a 63 kDa type II transmembrane protein, is an SP‐A receptor on type II pneumocytes. An antibody to P63 previously has been shown to block both the specific binding of SP‐A to pneumocytes and the ability of SP‐A to regulate surfactant secretion. In the current work, the P63 antibody blocked the ability of SP‐A to stimulate surfactant uptake by pneumocytes. P63 is located on both the plasma membrane (PM) and the endoplasmic reticulum (ER). Cyclic AMP exposure resulted in enrichment of P63 on the cell surface as shown by stimulation of SP‐A binding; enhanced association of labeled P63 antibody with type II cells; and promotion of SP‐A‐mediated liposome uptake, all of which were inhibited by competing P63 antibody. Treatment of type II cells with LY294002, an inhibitor of the phosphatidylinositol‐3‐kinase (PI3‐kinase) signaling pathway, prevented the SP‐A‐induced PM enrichment of P63. Exposure of pneumocytes to SP‐A or cAMP activated Akt (protein kinase B). Blocking either PI3‐kinase or Akt with inhibitors prevented SP‐A‐mediated lipid turnover. The data demonstrate an important role for the PI3‐kinase/Akt signaling pathway in the intracellular trafficking of P63. The results add further evidence that P63 is critical for SP‐A receptor‐mediated interactions with type II pneumocytes and the resultant regulation of surfactant turnover. [HL 19737]
Transepithelial Ion Transport Properties of Human Native Small Airways
Authors: Shamsuddin A K M , Quinton Paul M
Published: June 2021

Small airways are the crucial target in the pathogenesis of cystic fibrosis and other airway diseases. Characterization of transepithelial ion transport properties of small airways have been limited by their relative inaccessibility, mainly in native human tissue. We used our recently introduced micro‐Ussing chamber (area=1 mm2) to obtain the first measurements of ion transport properties of human native small airways specimens (<2 mm i.d.). Spontaneous open circuit transepithelial potentials (Vt), conductance (Gt) and equivalent short circuit current were measured. In presence of Cl− gradient Vt hyperpolarized and Gt decreased significantly. In symmetric NaCl, activating Cl− conductance with cAMP mediators (Fsk/IBMX) and purinergic agonist (UTP) evoked distinctly opposite effects on Vt, depolarizing and hyperpolarizing, respectively. Luminal amiloride depolarized Vt and decreased Gt significantly. Results suggest that human small airway epithelia express very high constitutively active Cl− conductance that support both secretory as well as absorptive functions. Small airways may consist of separate populations of secretory and absorptive cells that recycle airway surface fluids locally to maintain appropriate airway hydration and hygiene.

Supported by the Nancy Olmsted Trust, NIH (R01‐HL084042) and American Lung Association California.
Homoserine Lactone Stimulates CFTR‐Dependent Cl− Secretion in Human Airway Epithelial Cells: Roles for Ca2+ and cAMP
Authors: Machen Terry E , Schwarzer Christian , Wong Steven , Shi James , Matthes Elizabeth , Hofer Aldebaran , Illek Beate
Published: June 2021

When cystic fibrosis (CF) patients become colonized with P. aeruginosa, the bacteria secrete quorum‐sensing molecules, including N‐(3‐oxo‐dodecanoyl)‐S‐homoserine lactone (3O‐C12) to regulate bacterial gene expression. 10–50 μM 3O‐C12 increased Cl− secretion (ICl, transepithelial electrophysiology) in CFTR‐expressing airway epithelial cell lines (50% of ICl stimulated by forskolin], but not in a CF line. Thus, 3O‐C12‐stimulated ICl required CFTR. 3O‐C12 increased cytosolic [Ca2+] (Cai, fura‐2 imaging) similarly in Ca2+‐containing and Ca2+‐free solutions. 3O‐C12 had small effects to increase ICl and Cai in the presence of thapsigargin (inhibits Ca2+‐ATPase and releases ER Ca2+). 3O‐C12 increased cAMP (Epac H30 FRET imaging) to a level 25% of maximal stimulation with forskolin + isobutylmethylxanthine (IBMX, phosphodiesterase inhibitor). 3O‐C12‐stimulated ICl was inhibited by cAMP antagonist RpBrcAMPS and increased by IBMX. It is concluded that 3O‐C12 stimulation of ICl requires release of Ca2+ from the ER and, importantly, increases in cAMP. In CF, 3O‐C12‐triggered increases of both Cai and cAMP will not increase Cl− and fluid secretion by airway epithelia but will instead cause effects (mucus secretion, apoptosis) that increase bacterial retention or persistence in the airways.
Neonatal mice lacking serotonin neurons have high mortality that is worsened on exposure to hypoxia and hypercapnia.
Authors: Cerpa Veronica E , Flynn Rachel , Jamison Rachel , Richerson George B
Published: June 2021

Lmx1bf/f/p mice, which selectively lack central serotonin (5‐HT) neurons, have respiratory abnormalities, high mortality and growth retardation in the perinatal period. Here we studied the effects on mortality and growth rate of raising neonatal WT and Lmx1bf/f/p mice from ages P0‐P21 in environments containing 21% O2, 10% O2, 10% O2 & 5% CO2 or 50% O2. Lmx1bf/f/p mice had lower growth rate compared to WT in the same gas condition. Interestingly, WT mice raised in hypoxia grew at a rate equivalent to Lmx1bf/f/p mice raised in normoxia, whereas hypoxia further reduced growth of Lmx1bf/f/p mice. ANOVA revealed a significant effect of age (p < 0.001) and gas conditions (p < 0.001). Moreover, there was high perinatal mortality of Lmx1bf/f/p mice in normoxia that was worsened by hypoxia and improved by hyperoxia. The expected Mendelian ratio of the two genotypes (KO/WT) at the time litters were discovered should have been 1, but it was 0.48 in normoxia, 0.29 in hypoxia, 0.55 in hypoxic‐hypercapnia and 1.54 in hyperoxia. Kaplan‐Meier curves showed continued excess mortality in Lmx1bf/f/p mice for the first 3 postnatal days. Postnatal mortality was also worsened with hypoxia and improved with hyperoxia. Our results indicate that a defect in the 5‐HT system creates heightened vulnerability to hypoxia in neonatal mice, which could be related to the ventilatory abnormalities and vulnerability to exogenous stressors of SIDS infants.
Modulatory Effect of Fentanyl on Bronchopulmonary C‐fiber (PCF)‐mediated Ventilatory (VE) Responses Is Age‐dependent in Anesthetized Rats
Authors: Zhuang Jianguo , Zhang Zhenxiong , Zhang Cancan , Xu Fadi
Published: June 2021

In adult rats, opioids administered into the pulmonary circulation produces an apnea and given systemically turns the phenylbiguanide (PBG)‐evoked rapid shallow breaths (RSBs) to an apnea by stimulating and facilitating PCFs, respectively. Fentanyl, an opioid μ‐receptor agonist, clinically has a lesser inhibitory effect on ventilation in children (< 3 years old) than in adults (Barker, Pediatric Anesthesia 2007). Thus, we tested if the modulatory effect of opioids on the PCF‐mediated VE responses in rats were age‐dependent. VE responses to a right atrial bolus injection of PBG (before and after systemic administration of fentanyl) or fentanyl were recorded in anesthetized rat pups (3 week‐old) and adults. We found that: 1) PBG (5 μg/kg) evoked 5–10 RSBs in adults, but caused no change or 2–3 rapid breaths in pups; 2) systemic fentanyl (6 μg/kg, iv) reduced VE more greatly in adults (60%) than pups (27%, P < 0.01) and switched the PBG‐induced RSB to an apnea in adults, but failed to alter the PBG effects on VE in pups; 3) right atrial injection of fentanyl (2 μg/kg) alone produced an apnea in adults but not in pups; and 4) the VE responses to right atrial injection of PBG or fentanyl were eliminated by bilateral vagotomy. Our data suggest that the PCF‐mediated RSBs and inspiratory inhibition in response to PBG and fentanyl are age‐dependent in rats, indicating a plasticity of PCFs as development. (ALA RT‐83131‐N).
Inspiratory neural network complexity of unusual gasping patterns in urethane‐anesthetized neonatal rats
Authors: Salay Lindsey D , Reid Inefta M , Solomon Irene C
Published: June 2021

Gasping is an autoresuscitative mechanism in response to anoxia, and unusual gasp patterns (i.e., two or three closely spaced successive gasps termed ‘doublet’ and ‘triplet’ gasps) have been observed in infants with sudden infant death syndrome (SIDS) and non‐SIDS conditions during agonal respiration. Previously, we identified doublet and triplet gasps in spontaneously breathing urethane‐anesthetized P0‐P12 neonatal rats in response to an anoxic challenge, and characterized the timing features associated with these bursts. Here, we evaluated the complexity of the central inspiratory neural network underlying these unusual gasping patterns using approximate entropy (ApEn) analysis. For these analyses, the neonatal rats were divided into two groups based on the marked difference in the number of doublet gasps. In P0‐P6 rats (n=12), ApEn decreased from baseline (BL) when compared to singlet (from 0.318±0.008 to 0.279±0.003; P<0.01), but not doublet or triplet gasps. In contrast, in P7‐P12 rats (n=7), ApEn decreased from BL when compared to singlet (from 0.355±0.009 to 0.242±0.004; P<0.01), doublet (P<0.01), and triplet gasps (P<0.01). These data suggest that while the central inspiratory neural network underlying singlet gasps may be unaffected by developmental age, the network underlying unusual gasping patterns appears to be differentially influenced by maturation.

Supported by HL63175, NS049310
Insight on the development of neuroventilatory GABA‐mediated inhibition in bullfrog tadpoles
Authors: Cartagena Carla M , Brundage Cord M , Taylor Barbara E
Published: June 2021

GABA is a main inhibitory neurotransmitter in the adult vertebrate CNS. In mammals, activation of GABA‐A receptors transitions from depolarization to hyperpolarization early in development; GABA acting via GABA‐A receptors matures from an excitatory to an inhibitory neurotransmitter. In bullfrogs this transition was previously associated with late metamorphosis. To identify precisely the timing of this development, we quantified neuroventilatory responses to GABA (0.1 mM) in tadpoles across all metamorphic stages. Neuroventilatory responses to GABA were evaluated via whole‐nerve recordings from isolated brainstems. Throughout development GABA elicited a marked neuroventilatory depression. The results were confirmed at higher GABA concentrations (0.25 & 0.5 mM). Our data suggest that GABAergic inhibition develops earlier than previously reported for bullfrogs. Alternatively, the GABA‐A receptor‐mediated excitation associated with early development could be masked by signaling through GABA‐B receptors, which are consistently inhibitory and play a greater role in GABAergic signaling in early tadpole development. To resolve this issue, studies using receptor‐specific agonists are underway.
Effects of anesthetic state on properties of fast inspiratory rhythms in bilateral phrenic discharges of currarized adult rats
Authors: Cohen Morton I. , Ono Kenichi , Granata Antonio R.
Published: June 2021

In both cat and rat, fast rhythms during inspiration are seen in bilateral phrenic nerve discharges. These oscillations have been classified into two types: (a) high‐frequency (HFO), present in both autospectra and in cross‐spectra (coherences) of a signal pair; (b) medium frequency (MFO), present only in autospectra of a signal pair. To analyze these effects in rats, we recorded from bilateral phrenic discharges in two types of curarized rat preparation (male Sprague‐Dawley, 280–350 gm): 1) Urethane‐anesthetized (1.8 gm/kg). In 18 rats, the opposite phrenic nerves had similar autospectral dominant peaks (distribution: 55 mean + 13 SD Hz); but there was no significant coherence between opposite phrenic discharges at this dominant frequency. 2) Supracollicularly decerebrated. In 3 rats, phrenic discharges exhibited fast rhythms (HFO, high‐frequency oscillations, range 132 –170 Hz) that were seen in the autospectra of activities on opposite sides with very similar peak frequency and which also had a significant coherence peak at the dominant frequency. The lack of significant bilateral coherence peaks under anesthesia indicates that there is a tendency to reduce the interactions between inspiratory neurons that are involved in HFO generation and suggests that such interactions are weaker between neurons on opposite sides than between neurons on the same side.(Supported by N.I.H. Grant NS‐043940.)
Respiratory rhythm and pattern after ibotenic acid (A) injections into the pontine respiratory group (PRG) of awake goats
Authors: Bonis Josh , Neumueller Suzanne , Krause Katie , Kiner Tom , Smith Alex , Marshall Brooke , Baogang Qian , Pan Lawrence , Forster Hubert
Published: June 2021

We tested the hypothesis that IA injections into the PRG would disrupt eupneic respiratory rhythm and pattern. Cannula were bilaterally implanted in adult goats into either the lateral (LPBN, n = 4) or medial (MPBN, n = 4) parabrachial nuclei, or the Kölliker‐Fuse nucleus (KFN, n = 4). After recovery from surgery, 1 or 10μl injections of IA were made bilaterally through the implanted cannula during the awake state. Over the first 5 hours after the 10 μl injections, pulmonary ventilation was increased (P<0.05) in LPBN goats, there were no effects (P > 0.05) in MPBN goats, and there was a biphasic response (P < 0.05) in KFN goats. This biphasic response consisted of a tachypneic hyperpnea for 30 minutes followed by a prolonged hypopnea and hypoventilation with marked apneas and apneusis‐like breathing patterns. While awake and during NREM sleep 10–15 hours after the 1 μl and 10 μl injections respectively, there were above control number of apneas and augmented breaths in all groups. However, there were no incidences of terminal apneas. Breathing rhythm and pattern were normal 22 hours after the injections. Subsequent histological analysis showed <10%, 27%, and 62% reduction in number of neurons in the LPBN, MPBN and KFN goats, respectively. The data do not provide evidence that any of the lesioned sites are obligatory for respiratory rhythm generation, but suggest that the KFN contributes to eupneic pattern generation.
Dose‐dependent depression of preBotzinger Complex (pBC) region neurons by local application of the 5HT1A receptor agonist 8OH‐DPAT
Authors: Radocaj Tomislav , Mustapic Sanda , Stucke Astrid G. , Stuth Eckehard A. , Zuperku Edward J.
Published: June 2021

IV administration of 8OH‐DPAT increases breathing rate and has been used to counteract opioid‐induced depression. The mechanism by which 8OH‐DPAT produces its effect is unclear. This study determined the dose‐dependent effects of 8OH‐DPAT on single pBC neurons. Multi‐barrel micropipettes were used to record pBC neuronal activity and picoeject 8OH‐DPAT (1, 10, & 100 microM) in decerebrate, vagotomized, paralyzed and ventilated dogs during isocapnic hyperoxia. Picoejection of artificial CSF had no effect on peak and time‐averaged discharge frequencies (Fn), while 1 microM 8OH‐DPAT depressed peak and average Fn of I neurons by ~36% but had no effect on E neurons. Both I and E neurons were similarly depressed at 10 and 100 microM, with a maximum depression of ~42 % at 100 microM. Unilateral 8OH‐DPAT (200 microM, 100 nl) microinjections in 1 mm increments from the obex to 7mm rostral within the ventral respiratory column had no effect on the phrenic neurogram (PNG), while IV 8OH‐DPAT (~20 mcg/kg iv) decreased TI and TE to 67.1±4.5% and 62.3±7.2%, respectively with no change in peak PNG. These data suggest that pBC region 5HT1A receptors may not be responsive to the nanoM concentrations achieved with IV administration. Therefore exogenous biogenic amines may produce their effects on the breathing pattern at locations outside the VRC and pBC in dogs. Supported by VA Med. Res. and NIH GM059234 funds.
Is there diurnal variation with the vestibulosympathetic reflex?
Authors: Cook Jonathan S , Chin‐Sang Stephanie A , Sauder Charity L , Ray Chester A
Published: June 2021

We previously observed that exogenous melatonin (3 mg) attenuates the vestibulosympathetic reflex (VSR) in humans (Cook and Ray, Clin Auton Res 19:303, 2009). Because melatonin exhibits a circadian rhythm in humans by increasing at night, it was hypothesized that the VSR would be attenuated at night compared to day. Melatonin typically increases 8–10 times over daytime concentrations during the late evening hours. To test this hypothesis, arterial blood pressure, heart rate, calf blood flow and muscle sympathetic nerve activity (MSNA) were measured in 9 healthy subjects (28 ± 1 yr; 5 male, 4 female) at rest and during head‐down rotation (HDR). Each subject was tested around noon and 10–12 hr later that evening (day: 11:34 ± 13 min, night: 22:10 ± 5 min). Subjects were instructed not to sleep between the two testing sessions. During the day, HDR elicited an increase of Δ 3 ± 1 bursts/min (P < 0.05) from baseline with a significant decrease in calf blood flow (Δ 26 ± 7%; P < 0.05). HDR did not elicit changes in heart rate and arterial blood pressure. Contrary to our hypothesis, MSNA and cardiovascular responses to HDR were not significantly altered at night compared to day (Δ 3 ± 1 bursts/min, Δ 25 ± 6%, for MSNA and calf blood flow, respectively). These findings indicate that there is no diurnal variation in the VSR in humans. Moreover, endogenous increases in melatonin do not appear to modulate the VSR.

NIH HL077670, NASA Space Fellowship
An alternative method to the traditional NASA hindlimb suspension model in mice
Authors: Ferreira J Andries , Crissey Jacqueline M , Brown Marybeth
Published: June 2021

Animal models are used to induce atrophy and to evaluate interventions. The Morey‐Holton hindlimb unloading (HU) method is widely accepted.

PURPOSE

Evaluate an alternative to the Morey‐Holton HU technique in mice.

METHODS

Forty adult female mice were HU for 14 days with (n=24) or without (n=16) recovery. Ambulatory controls (n=49) were used for comparison. A thin stainless steel wire was passed through the intervertebral disc spaces between the 5th and 7th sacral vertebrae and shaped into a ring from which the mice were suspended. The vertebral location was selected to appropriately balance the animal's body weight but not interfere with defecation. Success of this novel hindlimb unloading technique was assessed by percent body weight lost during suspension, soleus atrophy and adrenal mass.

RESULTS

Body mass of the mice prior to HU (24.8 ± 3.8g) was not significantly different immediately after HU (23.8 ± 2.8g), or after 3 days recovery (24.7 ± 2.5g. Soleus mass declined (−35.6%) with HU (p<0.001. Adrenal gland weights did not significantly

CONCLUSION

The new method allows for ease of tail examination during suspension; decreases the likelihood of cyanotic, inflamed, and/or necrotic tails frequently observed with tail‐taping; and of mice chewing the traction tape (and becoming unsuspended). This tail‐ring method also ensures rapid recovery following HU. Support HD058834, MU Life Sciences Fellowship.
The University of California at Santa Barbara Institute of Environmental Stress (IES) marathon field studies of 1973–75
Authors: Maron Michael B.
Published: June 2021

In 1973, the IES, under the direction of Steven M. Horvath, began a series of field studies of marathon runners competing in the Santa Barbara Marathon. As a graduate student of Horvath's, these studies became my doctoral dissertation. The rationale for studying runners under race conditions was based on my belief that runners push themselves much harder when competing than in the lab. Horvath's ready support of the studies likely had its roots in his own graduate training at the Harvard Fatigue Lab, a lab well known for its field studies of workers laboring in extreme environments. This presentation describes the studies of 1973–75, focusing on how the measurements were made. In 1973, blood chemistry and plasma volume shifts were studied in 6 runners before and for 3 days after the race. This was the first modern study to systematically examine the recovery process. In 1974, VO2 was measured every 3 mi in 2 runners during the race. In 1975, rectal and 5 skin temperatures were determined in the same 2 runners every 1.4 mi of the race. The latter 2 studies were the first to make such measurements under race conditions. The IES marathon studies were significant, because they 1) demonstrated the possibility of making measurements during competition without disrupting performance, 2) enhanced our understanding of human exercise capacity under competitive conditions, and 3) provided new insight into the post‐race recovery process.
Peer Review and Oversight of Aero Medical Research During World War II in America: the Committee on Aviation Medicine and its Sub‐committees
Authors: Dean Jay B.
Published: June 2021

In anticipation of America's entry into WWII (8 Dec. 1941), a Committee on Aviation Medicine (CAM) was established in the fall of 1940 and charged with identifying the i) important physiological problems unique to flight and any ii) pre‐existing research facilities that could be used for hypobaric studies of animals and humans. iii) Most importantly, members of the CAM needed to identify physiologists who could adapt their research programs to the largely unexplored field of aviation medicine. Chaired by E.F. DuBois, the CAM oversaw a total of 37 research projects at 22 academic institutions during WWII, all funded by the Office of Scientific Research and Development. Members of the CAM's subcommittees were recruited largely from the ranks of the APS. Six major sub‐committees (1‐Acceleration, 2‐Oxygen & Anoxia, 3‐Decompression Sickness, 4‐Visual Problems, 5‐Clothing, and 6‐Motion Sickness) reviewed the scientific merit and progress of each project, and rendered decisions for either continuance or termination. The CAM and its performers worked closely with the major military centers of the Allies’ air forces (USAAF, USN, RAF, RCAF, RAAF) and America's aircraft industries to develop the protective flight gear and procedures for waging high altitude warfare in WWII.
Idiosyncratic Control of the Center of Mass in Expert Climbers
Authors: Zampagni Maria L. , Brigadoi Sabrina , Ivanenko Yuri P.
Published: June 2021

We studied posture and movement coordination adopted by expert climbers. The investigation of such expertise might be of particular interest to gain understanding about the mechanisms underlying the biomechanical control of vertical quadrupedal locomotion. A novel custom setup was developed to analyze the dynamic distribution of vertical reaction forces under the feet and the motion of the center of body mass (COM) during vertical climbing in nine Elite Climbers (EC) and nine control subjects. Two adaptive features were found in EC. First, unexpectedly they tended to maintain larger COM distances from the wall relative to controls subjects, during both the static and dynamic phases of vertical body motion. Second, while the control subjects tended to restrain the lateral motion of the COM, all EC demonstrated systematic COM oscillations associated with significant alternating dynamic redistribution of the body weight between the limbs during the double support phase. The latter phenomenon likely reflects an adopted basic climbing strategy in experts. The results will be discussed in the context of the biomechanical control of vertical quadrupedal locomotion. Furthermore, a convergence of the optimal solution towards a more diagonal climbing strategy in EC may shed light on the origin of the diagonal gait in primates and early hominids habituated to quadrupedal vertical locomotion.
Effect of High Intensity Interval Training (HIIT) on Substrate Utilization
Authors: Roberson Daniel W , Astorino Todd A , Allen Ryan P , Trost Emily , Jurancich Matthew
Published: June 2021

High‐intensity interval training (HIIT) provides a powerful stimulus that elicits similar physiological changes, such as increased VO2max and fat utilization, as traditional endurance training. However, the majority of studies employing this training regimen have used sedentary subjects, so it is unknown if it is still effective in active individuals.

PURPOSE

The primary aim of the study was to examine the effect of HIIT on substrate utilization in recreationally active men and women.

METHODS

Ten men and women (mean age and physical activity equal to 25.7 ± 5.18 yr and 7.0 ± 2.8 h/wk, respectively) completed HIIT consisting of 6 d of training (4 – 6 Wingate tests per day) over 3 wk. They regularly participated in cardiovascular exercise, resistance training, and/or sports, yet none were athletes. VO2max was measured pre‐ and post‐HIIT on the cycle ergometer. Via indirect calorimetry, substrate utilization was evaluated pre‐ and post‐training during 30 min of cycle ergometry, consisting of three 10 min bouts at 50, 60, and 70 % maximal workload (Wmax). Respiratory Exchange Ratio (RER) was used to assess substrate utilization, with gas exchange data averaged every five minutes. Subjects came to the laboratory after a minimum 3 h fast. Data were analyzed using a two‐way ANOVA with repeated measures.

RESULTS

VO2max was increased by 6 % with HIIT. There was a significant effect (p < 0.05) of HIIT on substrate utilization across time. For example, at 25 minutes of exercise, RER post‐training was equal to 0.96 ± .04 versus 0.99 ± .05 at baseline, indicating a 10 % increase in fat utilization.

CONCLUSION

Data from this preliminary study reveal that HIIT significantly alters (p < 0.05) RER, in the form of increased fat utilization, in active men and women.
Equivalent Increases in Bone Mineral Density Despite Differences in Training Volume In Growing Rats
Authors: Shdo Suzie M , Cunningham Ryan M , Pierce Richard A , Lee Lucy C , Ahles Cammie P , Jaque S Victoria , Sumida Ken D
Published: June 2021

The purpose of this study was to determine if there was an exercise threshold in stimulating an elevation in bone mineral density (BMD), via resistance training, during the growth period in male rats. 27 male rats were randomly divided into Control (Con, n=9), 3 ladder climb resistance trained group (3LC, n=9), and 6 ladder climb resistance trained group (6LC, n=9). The 3LC and 6LC groups were conditioned to climb a vertical ladder with weights appended to their tail 3 days/wk for a total of 6 wks where the 6LC group performed significantly more work compared to the 3LC group. After 6 wks, left tibial BMD (in g/cm2) was significantly greater for 3LC (0.225 ± 0.002) and 6LC (0.234 ± 0.003) compared to Con (0.202 ± 0.004). Further, bone strength (force to failure in Newtons) was significantly greater for 3LC (132.7 ± 4.6) and 6LC (130.0 ± 7.6) compared to Con (102.0 ± 3.4). Serum osteocalcin (OC in ng/ml, a marker for osteoblast activity) was significantly greater for 3LC (50.5 ± 3.4) and 6LC (41.7 ± 2.6) compared to Con (25.0 ± 3.4). There was no significant difference in BMD, bone strength, or OC between 3LC and 6LC. The results indicate that both resistance training programs were equally effective in elevating BMD and bone strength in growing rats. These data suggest that during growth, there is a stimulation threshold where more work per exercise session is ineffective in promoting additional bone formation.
Cortisol response to an acute bout of static stretching
Authors: Fuller Scott Eric , Stewart Laura K
Published: June 2021

Purpose

This study aimed to determine whether a single bout of static stretching affected salivary cortisol levels.

Methods

University students (n=22) were recruited to participate in the study. Participants were randomly assigned to a control group (n=9), or a stretching group (n=13). The stretching group underwent a series of five partner‐assisted stretches of the major muscle groups of the lower limb. Controls were subjected to a mock stretch in which the lower limb was moved by an investigator to a joint angle short of the point of discomfort. Before and immediately after stretching, saliva samples were collected by free expectoration for a duration of five minutes into a centrifuge tube. Saliva samples were then frozen at −80° C for later analysis by direct ELISA with a commercially available kit (ALPCO Diagnostics).

Results

Statistical analysis by 2‐way ANOVA with repeated measures revealed that the differences in pre‐ versus post‐stretch cortisol levels between the two groups were not significant (F = .01357, p = .9086). There was also no significant difference in mean salivary cortisol concentrations between the two groups in the pre‐ versus post‐stretch conditions (F= .19892, p = .6609).

Conclusion

The data in the present study indicates that an acute bout of stretching does not induce significant changes in salivary cortisol concentrations.
The influence of physical exertion on rapid decision making in athletes versus non‐athletes
Authors: Orf Ryan Shane , Wickenhauser Keith , Warncke Jason , Miller Therese , Potterfield April
Published: June 2021

This experiment was performed in order to test the effects of physical exertion on rapid decision making in athletes and non‐athletes. Forty subjects were involved in this experiment (twenty student‐athletes and twenty student non‐athletes, with each gender equally represented). Subjects strapped on a wireless heart rate belt, watch and were asked to mount the Ergomedic 828E in order to administer the test and monitor specific heart rate intervals. A keyboard was attached to the Ergomedic 828E and a computer screen was set up directly in front of it. Using My Brain Trainer, subjects took choice reaction time tests involving the choice of either a red or green light on a stop light. The test was administered six times to each subject at heart rate intervals of rest, 90 bpm, 110 bpm, 130 bpm, 150 bpm, and 170 bpm. Varying pedaling frequency and/or resistance was used in order to increase heart rates to desired levels. Statistical data show that as physical exertion increased (heart rate intervals) athletes reaction times became faster while non‐athletes reaction times became slower. These results indicate that athletes perform much better at high exertion levels than non‐athletes..
The Effects of Expiratory Muscle Strength Training (EMST) in Elite College Swimmers
Authors: Bernhardt Vipa , Nedrud Stacey M , Troy Gregg , Davenport Paul W
Published: June 2021

Swimming challenges the respiratory system due to increased hydrostatic pressure and resistance to breathing. We investigated the effects of 4 weeks EMST on maximum expiratory pressure (MEP) generating capacity of highly conditioned athletes. Varsity swimmers of the University of Florida were recruited and randomized to either EMST or air flow training (AFT) protocols. EMST was performed using pressure threshold trainers. The pressure load was set to 70–75% of the swimmer's MEP. Each week the pressure load was increased about 15%. AFT was conducted using peak flow meters and subjects were instructed to target a specific expiratory flow rate which was also increased each week about 15%. EMST and AFT were performed for 5 sets of 5 breaths with 1–2 min rest in between sets, 5 days per week for 4 weeks. MEP was measured pre‐ and post‐training. Pre‐training MEP values in all subjects were similar to non‐athletes. The increase in post‐training MEP values for EMST were significantly greater than AFT. The results demonstrate that: a) the expiratory muscle pressure generating capacity can be significantly increased in highly conditioned athletes and b) EMST is more effective in increasing MEP then AFT.
Does Supplemental Creatine Decrease Rehabilitation Time In Young Adults With Immobilization Related Injuries?
Authors: Corn Matthew Alvin , Kallail Donald , Bullock Chad , Payne Darin , Raynes Edilberto
Published: June 2021

There is a paucity of research on using oral supplements to shorten rehabilitation times. Creatine monohydrate is a dietary supplement ingested orally in powder or tablet form, which has been used heavily by athletes and recreational enthusiasts over the last ten years in an effort to improve strength gains and reduce recovery times. We hypothesize using supplemental creatine as an adjunct to physical therapy interventions will decrease rehabilitation times by improving strength gains and decreasing adverse effects of immobilization. A systematic review of literature was conducted based on the scale provided by the Oxford Centre of Evidence‐based Medicine. The literature reviewed focused on beneficial effects of creatine, physiological pathways within the muscle cell, pharmacokinetics, pharmacodynamics, and potential health risks of creatine use. Based on the evidence gathered, we determined that creatine is effective during glycolysis for energy production, and also in the recovery period after high intensity exercise by reducing lactic acid production, sparing glycogen, promoting myogenic transcription and maintaining a stable environment for protein synthesis. We concluded that creatine might be beneficial as an adjunct to traditional physical therapy interventions in decreasing rehabilitation time.