Mycoplasma pulmonis Inhibits Electrogenic Ion Transport across Murine Tracheal Epithelial Cell Monolayers

PubMed Central

Lambert, Linda C.; Trummell, Hoa Q.; Singh, Ashvani; Cassell, Gail H.; Bridges, Robert J.

1998-01-01

Murine chronic respiratory disease is characterized by persistent colonization of tracheal and bronchial epithelial cell surfaces by Mycoplasma pulmonis, submucosal and intraluminal immune and inflammatory cells, and altered airway activity. To determine the direct effect of M. pulmonis upon transepithelial ion transport in the absence of immune and inflammatory cell responses, primary mouse tracheal epithelial cell monolayers (MTEs) were apically infected and assayed in Ussing chambers. M. pulmonis-infected MTEs, but not those infected with a nonmurine mycoplasma, demonstrated reductions in amiloride-sensitive Na+ absorption, cyclic AMP, and cholinergic-stimulated Cl− secretion and transepithelial resistance. These effects were shown to require interaction of viable organisms with the apical surface of the monolayer and to be dependent upon organism number and duration of infection. Altered transport due to M. pulmonis was not merely a result of epithelial cell death as evidenced by the following: (i) active transport of Na+ and Cl−, albeit at reduced rates; (ii) normal cell morphology, including intact tight junctions, as demonstrated by electron microscopy; (iii) maintenance of a mean transepithelial resistance of 440 Ω/cm2; and (iv) lack of leakage of fluid from the basolateral to the apical surface of the monolayer. Alteration in epithelial ion transport in vitro is consistent with impaired pulmonary clearance and altered airway function in M. pulmonis-infected animals. Furthermore, the ability of M. pulmonis to alter transport without killing the host cell may explain its successful parasitism and long-term persistence in the host. Further study of the MTE-M. pulmonis model should elucidate the molecular mechanisms which mediate this reduction in transepithelial ion transport. PMID:9423868

Effects of long-acting beta adrenergic agonists on vocal fold ion transport.

PubMed

Sivasankar, Mahalakshmi; Blazer-Yost, Bonnie

2009-03-01

Inhaled medications prescribed for the hypersensitive airway typically combine corticosteroids and long-acting beta2 adrenergic agonists (LABAs). The phonatory side effects of these combination treatments are widely recognized. However, there is limited understanding of the physiological changes induced by these medications that underlie the phonatory side effects. The objective of this study was to investigate the distinct effects of corticosteroids and LABAs on vocal fold mucosal physiology. Understanding the physiological changes to the vocal folds after corticosteroid and LABA treatments is necessary to prevent the prevalent vocal decrement associated with these medications. Experimental in vitro design with treatment and control groups. Native porcine vocal fold mucosae (N = 38) were exposed to corticosteroid or LABA treatments. Ion transport was measured continuously at baseline and after treatment. To quantify the nature of ion transport, vocal folds were also treated with chloride and sodium channel inhibitors. Corticosteroid treatment did not alter ion transport. Conversely, exposure to LABAs significantly increased ion transport. This increase in ion transport was transient, observed immediately after treatment in all tissue and associated with increased chloride secretion. The distinct effects of corticosteroids and LABAs on vocal fold physiology have not been examined to date. This study demonstrates that short-term treatment with LABAs, but not corticosteroids, significantly increases ion transport. These findings suggest that one underlying physiological mechanism for phonatory changes associated with inhaled treatments may be related to acute alterations in vocal fold ion transport and surface hydration.

Regulation of human airway surface liquid.

PubMed

Widdicombe, J H; Widdicombe, J G

1995-01-01

Human airways are lined with a film of liquid from 5-100 microns in depth, consisting of a periciliary sol around and a mucous gel above the cilia. Microscopical studies have shown the sol to be invariably the same depth as the length of the cilia, and we discuss possible reasons for this. The composition and sources of the airway surface liquid are also described. In addition the forces regulating its volume are analyzed. Several airway diseases are characterised by dramatic changes in the volume and composition of airway liquid. We review recent research suggesting that the accumulation of airway mucous secretions in cystic fibrosis is caused by alterations in active transport of ions and water across both the surface and gland epithelia.

Chronic Hypoxemia in Children With Congenital Heart Defect Impairs Airway Epithelial Sodium Transport.

PubMed

Kaskinen, Anu K; Helve, Otto; Andersson, Sture; Kirjavainen, Turkka; Martelius, Laura; Mattila, Ilkka P; Rautiainen, Paula; Pitkänen, Olli M

2016-01-01

Ambient hypoxia impairs the airway epithelial Na transport, which is crucial in lung edema reabsorption. Whether chronic systemic hypoxemia affects airway Na transport has remained largely unknown. We have therefore investigated whether chronic systemic hypoxemia in children with congenital heart defect affects airway epithelial Na transport, Na transporter-gene expression, and short-term lung edema accumulation. Prospective, observational study. Tertiary care medical center responsible for nationwide pediatric cardiac surgery. Ninety-nine children with congenital heart defect or acquired heart disease (age range, 6 d to 14.8 yr) were divided into three groups based on their level of preoperative systemic hypoxemia: 1) normoxemic patients (SpO2% ≥ 95%; n = 44), 2) patients with cyanotic congenital heart defect and moderate hypoxemia (SpO2 86-94%; n = 16), and 3) patients with cyanotic congenital heart defect and profound systemic hypoxemia (SpO2 ≤ 85%; n = 39). Nasal transepithelial potential difference served as a surrogate measure for epithelial Na transport of the respiratory tract. Profoundly hypoxemic patients had 29% lower basal nasal transepithelial potential difference (p = 0.02) and 55% lower amiloride-sensitive nasal transepithelial potential difference (p = 0.0003) than normoxemic patients. In profoundly hypoxemic patients, nasal epithelial messenger RNA expressions of two airway Na transporters (amiloride-sensitive epithelial Na channel and β1- Na-K-ATPase) were not attenuated, but instead α1-Na-K-ATPase messenger RNA levels were higher (p = 0.03) than in the normoxemic patients, indicating that posttranscriptional factors may impair airway Na transport. The chest radiograph lung edema score increased after congenital cardiac surgery in profoundly hypoxemic patients (p = 0.0004) but not in patients with normoxemia or moderate hypoxemia. The impaired airway epithelial amiloride-sensitive Na transport activity in profoundly hypoxemic children with

Mathematical model reveals role of nucleotide signaling in airway surface liquid homeostasis and its dysregulation in cystic fibrosis

PubMed Central

Sandefur, Conner I.; Boucher, Richard C.; Elston, Timothy C.

2017-01-01

Mucociliary clearance is composed of three components (i.e., mucin secretion, airway surface hydration, and ciliary-activity) which function coordinately to clear inhaled microbes and other foreign particles from airway surfaces. Airway surface hydration is maintained by water fluxes driven predominantly by active chloride and sodium ion transport. The ion channels that mediate electrogenic ion transport are regulated by extracellular purinergic signals that signal through G protein-coupled receptors. These purinoreceptors and the signaling pathways they activate have been identified as possible therapeutic targets for treating lung disease. A systems-level description of airway surface liquid (ASL) homeostasis could accelerate development of such therapies. Accordingly, we developed a mathematical model to describe the dynamic coupling of ion and water transport to extracellular purinergic signaling. We trained our model from steady-state and time-dependent experimental measurements made using normal and cystic fibrosis (CF) cultured human airway epithelium. To reproduce CF conditions, reduced chloride secretion, increased potassium secretion, and increased sodium absorption were required. The model accurately predicted ASL height under basal normal and CF conditions and the collapse of surface hydration due to the accelerated nucleotide metabolism associated with CF exacerbations. Finally, the model predicted a therapeutic strategy to deliver nucleotide receptor agonists to effectively rehydrate the ASL of CF airways. PMID:28808008

Comparison of vectorial ion transport in primary murine airway and human sinonasal air-liquid interface cultures, models for studies of cystic fibrosis, and other airway diseases.

PubMed

Zhang, Shaoyan; Fortenberry, James A; Cohen, Noam A; Sorscher, Eric J; Woodworth, Bradford A

2009-01-01

The purpose of this study was to compare vectorial ion transport within murine trachea, murine nasal septa, and human sinonasal cultured epithelium. Our hypothesis is that murine septal epithelium, rather than trachea, will more closely mimic the electrophysiology properties of human sinonasal epithelium. Epithelium from murine trachea, murine septa, and human sinonasal tissue were cultured at an air-liquid interface to confluence and full differentiation. A limited number of homozygous dF508 epithelia were also cultured. Monolayers were mounted in modified Ussing chambers to investigate pharmacologic manipulation of ion transport. The change in forskolin-stimulated current (delta-I(SC), expressed as micro-A/cm(2)) in murine septal (n = 19; 16.84 +/- 2.09) and human sinonasal (n = 18; 12.15 +/- 1.93) cultures was significantly increased over murine tracheal cultures (n = 15; 6.75 +/- 1.35; p = 0.035 and 0.0005, respectively). Forskolin-stimulated I(SC) was inhibited by the specific cystic fibrosis transmembrane regulator (CFTR) inhibitor INH-172 (5 microM). No forskolin-stimulated I(SC) was shown in cultures of dF508 homozygous murine septal epithelium (n = 3). Murine septal I(SC) was largely inhibited by amiloride (12.03 +/- 0.66), whereas human sinonasal cultures had a very limited response (0.70 +/- 0.47; p < 0.0001). The contribution of CFTR to stimulated chloride current as measured by INH-172 was highly significantly different between all groups (murine septa, 19.51 +/- 1.28; human sinonasal, 11.12 +/- 1.58; murine trachea, 4.85 +/- 0.49; p < 0.0001). Human sinonasal and murine septal epithelial cultures represent a useful model for studying CFTR activity and may provide significant advantages over lower airway tissues for investigating upper and lower respiratory pathophysiology.

Acid-Sensing Ion Channel 1a Contributes to Airway Hyperreactivity in Mice

PubMed Central

Reznikov, Leah R.; Meyerholz, David K.; Adam, Ryan J.; Abou Alaiwa, Mahmoud; Jaffer, Omar; Michalski, Andrew S.; Powers, Linda S.; Price, Margaret P.; Stoltz, David A.; Welsh, Michael J.

2016-01-01

Neurons innervating the airways contribute to airway hyperreactivity (AHR), a hallmark feature of asthma. Several observations suggested that acid-sensing ion channels (ASICs), neuronal cation channels activated by protons, might contribute to AHR. For example, ASICs are found in vagal sensory neurons that innervate airways, and asthmatic airways can become acidic. Moreover, airway acidification activates ASIC currents and depolarizes neurons innervating airways. We found ASIC1a protein in vagal ganglia neurons, but not airway epithelium or smooth muscle. We induced AHR by sensitizing mice to ovalbumin and found that ASIC1a-/- mice failed to exhibit AHR despite a robust inflammatory response. Loss of ASIC1a also decreased bronchoalveolar lavage fluid levels of substance P, a sensory neuropeptide secreted from vagal sensory neurons that contributes to AHR. These findings suggest that ASIC1a is an important mediator of AHR and raise the possibility that inhibiting ASIC channels might be beneficial in asthma. PMID:27820848

Epithelial organic cation transporters ensure pH-dependent drug absorption in the airway.

PubMed

Horvath, Gabor; Schmid, Nathalie; Fragoso, Miryam A; Schmid, Andreas; Conner, Gregory E; Salathe, Matthias; Wanner, Adam

2007-01-01

Most inhaled beta(2)-adrenergic agonist and anticholinergic bronchodilators have low lipid solubility because of their transient or permanent positive net charge at physiologic pH. Airway absorption of these cationic drugs is incompletely understood. We examined carrier-mediated mechanisms of cationic drug uptake by human airway epithelia. Airway tissues and epithelial cells, obtained from lung donors without preexisting lung disease, were evaluated for organic cation transporter expression by quantitative RT-PCR and immunofluorescence. For in vitro functional studies on primary airway epithelial cells, uptake of the cationic fluorophore 4-[4-(dimethylamino)-styryl]-N-methylpyridinium (ASP+) was characterized. Quantitative RT-PCR analysis demonstrated high mRNA levels for two polyspecific organic cation/carnitine transporters, OCTN1 and OCTN2, in human airway epithelia. Immunofluorescence of human airway sections confirmed OCTN1/2 protein expression, with a predominant localization to the apical portion of epithelial cells. Primary airway epithelial cells showed a carrier-mediated, temperature-sensitive and saturable uptake of ASP(+). Seventy-five to eighty percent of ASP(+) uptake was inhibited by L-carnitine, an OCTN2-carried zwitterion. The uptake was pH dependent, with approximately 3-fold lower rates at acidic (pH 5.7) than at alkaline (pH 8.2) extracellular pH. Albuterol and formoterol inhibited ASP(+) uptake, suggesting that all these molecules are carried by the same transport mechanism. These findings demonstrate the existence and functional role of a pH-dependent organic cation uptake machinery, namely OCTN1 and OCTN2, in human airway epithelia. We suggest that epithelial OCTN1/2 are involved in the delivery of inhaled cationic bronchodilators to the airway tissue.

Transport and deposition of cohesive pharmaceutical powders in human airway

NASA Astrophysics Data System (ADS)

Wang, Yuan; Chu, Kaiwei; Yu, Aibing

2017-06-01

Pharmaceutical powders used in inhalation therapy are in the size range of 1-5 microns and are usually cohesive. Understanding the cohesive behaviour of pharmaceutical powders during their transportation in human airway is significant in optimising aerosol drug delivery and targeting. In this study, the transport and deposition of cohesive pharmaceutical powders in a human airway model is simulated by a well-established numerical model which combines computational fluid dynamics (CFD) and discrete element method (DEM). The van der Waals force, as the dominant cohesive force, is simulated and its influence on particle transport and deposition behaviour is discussed. It is observed that even for dilute particle flow, the local particle concentration in the oral to trachea region can be high and particle aggregation happens due to the van der Waals force of attraction. It is concluded that the deposition mechanism for cohesive pharmaceutical powders, on one hand, is dominated by particle inertial impaction, as proven by previous studies; on the other hand, is significantly affected by particle aggregation induced by van der Waals force. To maximum respiratory drug delivery efficiency, efforts should be made to avoid pharmaceutical powder aggregation in human oral-to-trachea airway.

Uptake and transport of B12-conjugated nanoparticles in airway epithelium☆

PubMed Central

Fowler, Robyn; Vllasaliu, Driton; Falcone, Franco H.; Garnett, Martin; Smith, Bryan; Horsley, Helen; Alexander, Cameron; Stolnik, Snow

2013-01-01

Non-invasive delivery of biotherapeutics, as an attractive alternative to injections, could potentially be achieved through the mucosal surfaces, utilizing nanoscale therapeutic carriers. However, nanoparticles do not readily cross the mucosal barriers, with the epithelium presenting a major barrier to their translocation. The transcytotic pathway of vitamin B12 has previously been shown to ‘ferry’ B12-decorated nanoparticles across intestinal epithelial (Caco-2) cells. However, such studies have not been reported for the airway epithelium. Furthermore, the presence in the airways of the cell machinery responsible for transepithelial trafficking of B12 is not widely reported. Using a combination of molecular biology and immunostaining techniques, our work demonstrates that the bronchial cell line, Calu-3, expresses the B12-intrinsic factor receptor, the transcobalamin II receptor and the transcobalamin II carrier protein. Importantly, the work showed that sub-200 nm model nanoparticles chemically conjugated to B12 were internalised and transported across the Calu-3 cell layers, with B12 conjugation not only enhancing cell uptake and transepithelial transport, but also influencing intracellular trafficking. Our work therefore demonstrates that the B12 endocytotic apparatus is not only present in this airway model, but also transports ligand-conjugated nanoparticles across polarised epithelial cells, indicating potential for B12-mediated delivery of nanoscale carriers of biotherapeutics across the airways. PMID:24008152

Investigation of mucus transport in an idealized lung airway model using multiphase CFD analysis

NASA Astrophysics Data System (ADS)

Rajendran, Rahul; Banerjee, Arindam

2015-11-01

Mucus, a Bingham fluid is transported in the pulmonary airways by consistent beating of the cilia and exhibits a wide range of physical properties in response to the core air flow and various pathological conditions. A better understanding of the interfacial instability is required as it plays a crucial role in gas transport, mixing, mucus clearance and drug delivery. In the current study, mucus is modelled as a Newtonian fluid and the two phase gas-liquid flow in the airways is investigated using an inhomogeneous Eulerian-Eulerian approach. The complex interface between the phases is tracked using the conventional VOF (Volume of Fluid) method. Results from our CFD simulations which are performed in idealized single and double bifurcation geometries will be presented and the influence of airflow rate, mucus layer thickness, mucus viscosity, airway geometry (branching & diameter) and surface tension on mucus flow behavior will be discussed. Mean mucus layer thickness, pressure drop due to momentum transfer & increased airway resistance, mucus transport speed and the flow morphology will be compared to existing experimental and theoretical data.

Numerical investigation of diesel exhaust particle transport and deposition in the CT-scan based lung airway

NASA Astrophysics Data System (ADS)

Islam, Mohammad S.; Saha, Suvash C.; Sauret, Emilie; Gu, Y. T.; Molla, Md Mamun

2017-06-01

Diesel exhaust particulates matter (DEPM) is a compound mixture of gasses and fine particles that contain more than 40 toxic air pollutants including benzene, formaldehyde, and nitrogen oxides. Exposure of DEPM to human lung airway during respiratory inhalation causes severe health hazards like diverse pulmonary diseases. This paper studies the DEPM transport and deposition in upper three generations of the realistic lung airways. A 3-D digital airway bifurcation model is constructed from the computerized tomography (CT) scan data of a healthy adult man. The Euler-Lagrange approach is used to solve the continuum and disperse phases of the calculation. Local averaged Navier-Stokes equations are solved to calculate the transport of the continuum phase. Lagrangian based Discrete Phase Model (DPM) is used to investigate the particle transport and deposition in the current anatomical model. The effects of size specific monodispersed particles on deposition are extensively investigated during different breathing pattern. The numerical results illustrate that particle diameter and breathing pattern have a substantial impact on particles transport and deposition in the tracheobronchial airways. The present realistic bifurcation model also depicts a new deposition hot spot which could advance the understanding of the therapeutic drug delivery system to the specific position of the respiratory airways.

Composition of nasal airway surface liquid in cystic fibrosis and other airway diseases determined by X-ray microanalysis.

PubMed

Vanthanouvong, V; Kozlova, I; Johannesson, M; Nääs, E; Nordvall, S L; Dragomir, A; Roomans, G M

2006-04-01

The ionic composition of the airway surface liquid (ASL) in healthy individuals and in patients with cystic fibrosis (CF) has been debated. Ion transport properties of the upper airway epithelium are similar to those of the lower airways and it is easier to collect nasal ASL from the nose. ASL was collected with ion exchange beads, and the elemental composition of nasal fluid was determined by X-ray microanalysis in healthy subjects, CF patients, CF heterozygotes, patients with rhinitis, and with primary ciliary dyskinesia (PCD). In healthy subjects, the ionic concentrations were approximately isotonic. In CF patients, CF heterozygotes, rhinitis, and PCD patients, [Na] and [Cl] were significantly higher compared when compared with those in controls. [K] was significantly higher in CF and PCD patients compared with that in controls. Severely affected CF patients had higher ionic concentrations in their nasal ASL than in patients with mild or moderate symptoms. Female CF patients had higher levels of Na, Cl, and K than male patients. As higher salt concentrations in the ASL are also found in other patients with airway diseases involving chronic inflammation, it appears likely that inflammation-induced epithelial damage is important in determining the ionic composition of the ASL. Copyright (c) 2006 Wiley-Liss, Inc.

Ion channel-transporter interactions

PubMed Central

Neverisky, Daniel L.; Abbott, Geoffrey W.

2016-01-01

All living cells require membrane proteins that act as conduits for the regulated transport of ions, solutes and other small molecules across the cell membrane. Ion channels provide a pore that permits often rapid, highly selective, and tightly regulated movement of ions down their electrochemical gradient. In contrast, active transporters can move moieties up their electrochemical gradient. The secondary active transporters (such as SLC superfamily solute transporters) achieve this by coupling uphill movement of the substrate to downhill movement of another ion, such as sodium. The primary active transporters (including H+/K+-ATPases and Na+/K+-ATPases) utilize ATP hydrolysis as an energy source to power uphill transport. It is well known that proteins in each of these classes work in concert with members of the other classes to ensure, for example, ion homeostasis, ion secretion, and restoration of ion balance following action potentials. More recently, evidence is emerging of direct physical interaction between true ion channels, and some primary or secondary active transporters. Here, we review the first known members of this new class of macromolecular complexes that we term “chansporters”, explore their biological roles, and discuss the pathophysiological consequences of their disruption. We compare functional and/or physical interactions between the ubiquitous KCNQ1 potassium channel and various active transporters, and examine other newly discovered chansporter complexes that suggest we may be seeing the tip of the iceberg in a newly emerging signaling modality. PMID:27098917

Secondary ion collection and transport system for ion microprobe

DOEpatents

Ward, James W.; Schlanger, Herbert; McNulty, Jr., Hugh; Parker, Norman W.

1985-01-01

A secondary ion collection and transport system, for use with an ion microprobe, which is very compact and occupies only a small working distance, thereby enabling the primary ion beam to have a short focal length and high resolution. Ions sputtered from the target surface by the primary beam's impact are collected between two arcuate members having radii of curvature and applied voltages that cause only ions within a specified energy band to be collected. The collected ions are accelerated and focused in a transport section consisting of a plurality of spaced conductive members which are coaxial with and distributed along the desired ion path. Relatively high voltages are applied to alternate transport sections to produce accelerating electric fields sufficient to transport the ions through the section to an ion mass analyzer, while lower voltages are applied to the other transport sections to focus the ions and bring their velocity to a level compatible with the analyzing apparatus.

Ion transport in pigmentation.

PubMed

Bellono, Nicholas W; Oancea, Elena V

2014-12-01

Skin melanocytes and ocular pigment cells contain specialized organelles called melanosomes, which are responsible for the synthesis of melanin, the major pigment in mammals. Defects in the complex mechanisms involved in melanin synthesis and regulation result in vision and pigmentation deficits, impaired development of the visual system, and increased susceptibility to skin and eye cancers. Ion transport across cellular membranes is critical for many biological processes, including pigmentation, but the molecular mechanisms by which it regulates melanin synthesis, storage, and transfer are not understood. In this review we first discuss ion channels and transporters that function at the plasma membrane of melanocytes; in the second part we consider ion transport across the membrane of intracellular organelles, with emphasis on melanosomes. We discuss recently characterized lysosomal and endosomal ion channels and transporters associated with pigmentation phenotypes. We then review the evidence for melanosomal channels and transporters critical for pigmentation, discussing potential molecular mechanisms mediating their function. The studies investigating ion transport in pigmentation physiology open new avenues for future research and could reveal novel molecular mechanisms underlying melanogenesis.

Ion transport in pigmentation

PubMed Central

Bellono, Nicholas W.; Oancea, Elena V.

2014-01-01

Skin melanocytes and ocular pigment cells contain specialized organelles called melanosomes, which are responsible for the synthesis of melanin, the major pigment in mammals. Defects in the complex mechanisms involved in melanin synthesis and regulation result in vision and pigmentation deficits, impaired development of the visual system,, and increased susceptibility to skin and eye cancers. Ion transport across cellular membranes is critical for many biological processes, including pigmentation, but the molecular mechanisms by which it regulates melanin synthesis, storage, and transfer are not understood. In this review we first discuss ion channels and transporters that function at the plasma membrane of melanocytes; in the second part we consider ion transport across the membrane of intracellular organelles, with emphasis on melanosomes. We discuss recently characterized lysosomal and endosomal ion channels and transporters associated with pigmentation phenotypes. We then review the evidence for melanosomal channels and transporters critical for pigmentation, discussing potential molecular mechanisms mediating their function. The studies investigating ion transport in pigmentation physiology open new avenues for future research and could reveal novel molecular mechanisms underlying melanogenesis. PMID:25034214

Second-messenger regulation of sodium transport in mammalian airway epithelia.

PubMed Central

Graham, A; Steel, D M; Alton, E W; Geddes, D M

1992-01-01

1. Sodium absorption is the dominant ion transport process in conducting airways and is a major factor regulating the composition of airway surface liquid. However, little is known about the control of airway sodium transport by intracellular regulatory pathways. 2. In sheep tracheae and human bronchi mounted in Ussing chambers under short circuit conditions, the sodium current can be isolated by pretreating tissues with acetazolamide (100 microM) to inhibit bicarbonate secretion, bumetanide (100 microM) to inhibit chloride secretion and phloridzin (200 microM) to inhibit sodium-glucose cotransport. This sodium current consists of amiloride-sensitive (57%) and amiloride-insensitive (43%) components. 3. The regulation of the isolated sodium current by three second messenger pathways was studied using the calcium ionophore A23187 to elevate intracellular calcium, a combination of forskolin and the phosphodiesterase inhibitor zardaverine to elevate intracellular cyclic AMP, and the phorbol ester 12,13-phorbol dibutyrate (PDB) to stimulate protein kinase C. 4. In sheep trachea, A23187 produces a dose-related inhibition of the sodium current with maximal effect (38% of ISC) at 10 microM and IC50 1 microM. This response affects both the amiloride-sensitive and insensitive components of the sodium current and is not altered by prior stimulation of protein kinase C or elevation of intracellular cyclic AMP. In human bronchi, A23187 (10 microM) produced a significantly greater inhibition of ISC (68%), a response which was unaffected by prior treatment with PDB or forskolin-zardaverine. 5. In sheep trachea, stimulation of protein kinase C with PDB produced a dose-related inhibition of ISC maximal (56% of ISC) at 50 nM (IC50 7 nM). This response was abolished by amiloride (100 microM) pretreatment suggesting a selective effect on the amiloride-sensitive component of the sodium current. The response was not altered by prior elevation of intracellular calcium or cyclic AMP. PDB

Luminal cholinergic signalling in airway lining fluid: a novel mechanism for activating chloride secretion via Ca2+-dependent Cl− and K+ channels

PubMed Central

Hollenhorst, Monika I; Lips, Katrin S; Wolff, Miriam; Wess, Jürgen; Gerbig, Stefanie; Takats, Zoltan; Kummer, Wolfgang; Fronius, Martin

2012-01-01

BACKGROUND AND PURPOSE Recent studies detected the expression of proteins involved in cholinergic metabolism in airway epithelial cells, although the function of this non-neuronal cholinergic system is not known in detail. Thus, this study focused on the effect of luminal ACh as a regulator of transepithelial ion transport in epithelial cells. EXPERIMENTAL APPROACH RT-PCR experiments were performed using mouse tracheal epithelial cells for ChAT and organic cation transporter (OCT) transcripts. Components of tracheal airway lining fluid were analysed with desorption electrospray ionization (DESI) MS. Effects of nicotine on mouse tracheal epithelial ion transport were examined with Ussing-chamber experiments. KEY RESULTS Transcripts encoding ChAT and OCT1–3 were detected in mouse tracheal epithelial cells. The DESI experiments identified ACh in the airway lining fluid. Luminal ACh induced an immediate, dose-dependent increase in the transepithelial ion current (EC50: 23.3 µM), characterized by a transient peak and sustained plateau current. This response was not affected by the Na+-channel inhibitor amiloride. The Cl−-channel inhibitor niflumic acid or the K+-channel blocker Ba2+ attenuated the ACh effect. The calcium ionophore A23187 mimicked the ACh effect. Luminal nicotine or muscarine increased the ion current. Experiments with receptor gene-deficient animals revealed the participation of muscarinic receptor subtypes M1 and M3. CONCLUSIONS AND IMPLICATIONS The presence of luminal ACh and activation of transepithelial ion currents by luminal ACh receptors identifies a novel non-neuronal cholinergic pathway in the airway lining fluid. This pathway could represent a novel drug target in the airways. PMID:22300281

Influence of short distance transportation on tracheal bacterial content and lower airway cytology in horses.

PubMed

Allano, Marion; Labrecque, Olivia; Rodriguez Batista, Edisleidy; Beauchamp, Guy; Bédard, Christian; Lavoie, Jean-Pierre; Leclere, Mathilde

2016-08-01

The aim of this study was to determine the effects of short distance transportation on airway mucus, cytology and bacterial culture to identify potential biases in the diagnosis of airway diseases in referral centres. Eight healthy adult horses were studied using a prospective cross-over design. Mucus scores, tracheal wash (cytology, bacterial culture) and bronchoalveolar lavage fluid (BALF; cytology) were obtained while stabled and following 2.5 h transportation (with and without hay). Neutrophil counts, percentages and BALF neutrophilia frequency increased following transport without hay (P <0.05). No effect was observed on tracheal cytology and bacterial count (P > 0.05). BALF neutrophilia could develop solely as a result of transportation or due to interactions between repeated transports, ambient temperature, head position or other environmental factors. Copyright © 2016 Elsevier Ltd. All rights reserved.

Airway surface liquid homeostasis in cystic fibrosis: pathophysiology and therapeutic targets.

PubMed

Haq, Iram J; Gray, Michael A; Garnett, James P; Ward, Christopher; Brodlie, Malcolm

2016-03-01

Cystic fibrosis (CF) is a life-limiting disease characterised by recurrent respiratory infections, inflammation and lung damage. The volume and composition of the airway surface liquid (ASL) are important in maintaining ciliary function, mucociliary clearance and antimicrobial properties of the airway. In CF, these homeostatic mechanisms are impaired, leading to a dehydrated and acidic ASL. ASL volume depletion in CF is secondary to defective anion transport by the abnormal cystic fibrosis transmembrane conductance regulator protein (CFTR). Abnormal CFTR mediated bicarbonate transport creates an unfavourable, acidic environment, which impairs antimicrobial function and alters mucus properties and clearance. These disease mechanisms create a disordered airway milieu, consisting of thick mucopurulent secretions and chronic bacterial infection. In addition to CFTR, there are additional ion channels and transporters in the apical airway epithelium that play a role in maintaining ASL homeostasis. These include the epithelial sodium channel (ENaC), the solute carrier 26A (SLC26A) family of anion exchangers, and calcium-activated chloride channels. In this review we discuss how the ASL is abnormal in CF and how targeting these alternative channels and transporters could provide an attractive therapeutic strategy to correct the underlying ASL abnormalities evident in CF. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

Ion Move Brownian Dynamics (IMBD)--simulations of ion transport.

PubMed

Kurczynska, Monika; Kotulska, Malgorzata

2014-01-01

Comparison of the computed characteristics and physiological measurement of ion transport through transmembrane proteins could be a useful method to assess the quality of protein structures. Simulations of ion transport should be detailed but also timeefficient. The most accurate method could be Molecular Dynamics (MD), which is very time-consuming, hence is not used for this purpose. The model which includes ion-ion interactions and reduces the simulation time by excluding water, protein and lipid molecules is Brownian Dynamics (BD). In this paper a new computer program for BD simulation of the ion transport is presented. We evaluate two methods for calculating the pore accessibility (round and irregular shape) and two representations of ion sizes (van der Waals diameter and one voxel). Ion Move Brownian Dynamics (IMBD) was tested with two nanopores: alpha-hemolysin and potassium channel KcsA. In both cases during the simulation an ion passed through the pore in less than 32 ns. Although two types of ions were in solution (potassium and chloride), only ions which agreed with the selectivity properties of the channels passed through the pores. IMBD is a new tool for the ion transport modelling, which can be used in the simulations of wide and narrow pores.

Role of Aquaporin Water Channels in Airway Fluid Transport, Humidification, and Surface Liquid Hydration

PubMed Central

Song, Yuanlin; Jayaraman, Sujatha; Yang, Baoxue; Matthay, Michael A.; Verkman, A.S.

2001-01-01

Several aquaporin-type water channels are expressed in mammalian airways and lung: AQP1 in microvascular endothelia, AQP3 in upper airway epithelia, AQP4 in upper and lower airway epithelia, and AQP5 in alveolar epithelia. Novel quantitative methods were developed to compare airway fluid transport–related functions in wild-type mice and knockout mice deficient in these aquaporins. Lower airway humidification, measured from the moisture content of expired air during mechanical ventilation with dry air through a tracheotomy, was 54–56% efficient in wild-type mice, and reduced by only 3–4% in AQP1/AQP5 or AQP3/AQP4 double knockout mice. Upper airway humidification, measured from the moisture gained by dry air passed through the upper airways in mice breathing through a tracheotomy, decreased from 91 to 50% with increasing ventilation from 20 to 220 ml/min, and reduced by 3–5% in AQP3/AQP4 knockout mice. The depth and salt concentration of the airway surface liquid in trachea was measured in vivo using fluorescent probes and confocal and ratio imaging microscopy. Airway surface liquid depth was 45 ± 5 μm and [Na+] was 115 ± 4 mM in wild-type mice, and not significantly different in AQP3/AQP4 knockout mice. Osmotic water permeability in upper airways, measured by an in vivo instillation/sample method, was reduced by ∼40% by AQP3/AQP4 deletion. In doing these measurements, we discovered a novel amiloride-sensitive isosmolar fluid absorption process in upper airways (13% in 5 min) that was not affected by aquaporin deletion. These results establish the fluid transporting properties of mouse airways, and indicate that aquaporins play at most a minor role in airway humidification, ASL hydration, and isosmolar fluid absorption. PMID:11382807

Transepithelial Ion Transport is Suppressed in Hypoxic Sinonasal Epithelium

PubMed Central

Blount, Angela; Zhang, Shaoyan; Chestnut, Michael; Hixon, Brian; Skinner, Daniel; Sorscher, Eric J.; Woodworth, Bradford A.

2011-01-01

Objectives/Hypothesis Sinonasal respiratory epithelial mucociliary clearance (MCC) is dependent on the transepithelial transport of ions such as Cl−. The objectives of the present study were to investigate the role of oxygen restriction in 1) Cl− transport across primary sinonasal epithelial monolayers, 2) expression of the apical Cl− channels CFTR and TMEM16A, and 3) the pathogenesis of chronic rhinosinusitis (CRS). Study Design In vitro investigation. Methods Murine nasal septal epithelial (MNSE, wild type) and human sinonasal epithelial (HSNE) cultures were incubated under hypoxic conditions (1% O2, 5% CO2). Cultures were mounted in Ussing chambers for ion transport measurements. CFTR and TMEM16A expression were measured using quantitative RT-PCR. Results The change in short-circuit current (ΔISC (µA/cm2) attributable to CFTR (forskolin-stimulated) was significantly decreased due to a 12 hour hypoxia exposure in both MNSE (13.55+/− 0.46 vs. 19.23+/−0.18) and HSNE (19.55+/−0.56 vs. 25.49+/−1.48 (control); p<0.05. TMEM16A (UTP-stimulated transport) was inhibited by 48 hours of hypoxic exposure in MNSE (15.92+/−2.87 vs. 51.44+/−3.71(control) p<0.05] and by 12 hours of hypoxic exposure in HSNE (16.75+/−0.68 vs. 24.15+/−1.35 (control). Quantitative RT-PCR (reported as relative mRNA levels+/−S.D.) demonstrated significant reductions in both CFTR and TMEM16A mRNA expression in MNSE and HSNE due to airway epithelial hypoxia. Conclusions Sinonasal epithelial CFTR and TMEM16A-mediated Cl− transport and mRNA expression were robustly decreased in an oxygen restricted environment. The findings in the present study indicate persistent hypoxia may lead to acquired defects in sinonasal Cl− transport in a fashion likely to confer mucociliary dysfunction in CRS. Level of Evidence 1b PMID:22024847

TRANSPORT AND DEPOSITION OF NANO-SIZE PARTICLES IN THE UPPER HUMAN RESPIRATORY AIRWAYS

EPA Science Inventory

TRANSPORT AND DEPOSITION OF NANO-SIZE PARTICLES IN THE UPPER HUMAN RESPIRATORY AIRWAYS. Zhe Zhang*, Huawei Shi, Clement Kleinstreuer, Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, NC 27695-7910; Chong S. Kim, National Health and En...

Effect of Mucin and Bicarbonate Ion on Corrosion Behavior of AZ31 Magnesium Alloy for Airway Stents.

PubMed

Jang, Yongseok; Owuor, Daniel; Waterman, Jenora T; White, Leon; Collins, Boyce; Sankar, Jagannathan; Gilbert, Thomas W; Yun, Yeoheung

2014-08-15

The biodegradable ability of magnesium alloys is an attractive feature for tracheal stents since they can be absorbed by the body through gradual degradation after healing of the airway structure, which can reduce the risk of inflammation caused by long-term implantation and prevent the repetitive surgery for removal of existing stent. In this study, the effects of bicarbonate ion (HCO₃ - ) and mucin in Gamble's solution on the corrosion behavior of AZ31 magnesium alloy were investigated, using immersion and electrochemical tests to systematically identify the biodegradation kinetics of magnesium alloy under in vitro environment, mimicking the epithelial mucus surfaces in a trachea for development of biodegradable airway stents. Analysis of corrosion products after immersion test was performed using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). Electrochemical impedance spectroscopy (EIS) was used to identify the effects of bicarbonate ions and mucin on the corrosion behavior of AZ31 magnesium alloys with the temporal change of corrosion resistance. The results show that the increase of the bicarbonate ions in Gamble's solution accelerates the dissolution of AZ31 magnesium alloy, while the addition of mucin retards the corrosion. The experimental data in this work is intended to be used as foundational knowledge to predict the corrosion behavior of AZ31 magnesium alloy in the airway environment while providing degradation information for future in vivo studies.

Computational modeling of ion transport through nanopores.

PubMed

Modi, Niraj; Winterhalter, Mathias; Kleinekathöfer, Ulrich

2012-10-21

Nanoscale pores are ubiquitous in biological systems while artificial nanopores are being fabricated for an increasing number of applications. Biological pores are responsible for the transport of various ions and substrates between the different compartments of biological systems separated by membranes while artificial pores are aimed at emulating such transport properties. As an experimental method, electrophysiology has proven to be an important nano-analytical tool for the study of substrate transport through nanopores utilizing ion current measurements as a probe for the detection. Independent of the pore type, i.e., biological or synthetic, and objective of the study, i.e., to model cellular processes of ion transport or electrophysiological experiments, it has become increasingly important to understand the dynamics of ions in nanoscale confinements. To this end, numerical simulations have established themselves as an indispensable tool to decipher ion transport processes through biological as well as artificial nanopores. This article provides an overview of different theoretical and computational methods to study ion transport in general and to calculate ion conductance in particular. Potential new improvements in the existing methods and their applications are highlighted wherever applicable. Moreover, representative examples are given describing the ion transport through biological and synthetic nanopores as well as the high selectivity of ion channels. Special emphasis is placed on the usage of molecular dynamics simulations which already have demonstrated their potential to unravel ion transport properties at an atomic level.

Changes in ion transport in inflammatory disease.

PubMed

Eisenhut, Michael

2006-03-29

Ion transport is essential for maintenance of transmembranous and transcellular electric potential, fluid transport and cellular volume. Disturbance of ion transport has been associated with cellular dysfunction, intra and extracellular edema and abnormalities of epithelial surface liquid volume. There is increasing evidence that conditions characterized by an intense local or systemic inflammatory response are associated with abnormal ion transport. This abnormal ion transport has been involved in the pathogenesis of conditions like hypovolemia due to fluid losses, hyponatremia and hypokalemia in diarrhoeal diseases, electrolyte abnormalities in pyelonephritis of early infancy, septicemia induced pulmonary edema, and in hypersecretion and edema induced by inflammatory reactions of the mucosa of the upper respiratory tract. Components of membranous ion transport systems, which have been shown to undergo a change in function during an inflammatory response include the sodium potassium ATPase, the epithelial sodium channel, the Cystic Fibrosis Transmembrane Conductance Regulator and calcium activated chloride channels and the sodium potassium chloride co-transporter. Inflammatory mediators, which influence ion transport are tumor necrosis factor, gamma interferon, interleukins, transforming growth factor, leukotrienes and bradykinin. They trigger the release of specific messengers like prostaglandins, nitric oxide and histamine which alter ion transport system function through specific receptors, intracellular second messengers and protein kinases. This review summarizes data on in vivo measurements of changes in ion transport in acute inflammatory conditions and in vitro studies, which have explored the underlying mechanisms. Potential interventions directed at a correction of the observed abnormalities are discussed.

Changes in ion transport in inflammatory disease

PubMed Central

Eisenhut, Michael

2006-01-01

Ion transport is essential for maintenance of transmembranous and transcellular electric potential, fluid transport and cellular volume. Disturbance of ion transport has been associated with cellular dysfunction, intra and extracellular edema and abnormalities of epithelial surface liquid volume. There is increasing evidence that conditions characterized by an intense local or systemic inflammatory response are associated with abnormal ion transport. This abnormal ion transport has been involved in the pathogenesis of conditions like hypovolemia due to fluid losses, hyponatremia and hypokalemia in diarrhoeal diseases, electrolyte abnormalites in pyelonephritis of early infancy, septicemia induced pulmonary edema, and in hypersecretion and edema induced by inflammatory reactions of the mucosa of the upper respiratory tract. Components of membranous ion transport systems, which have been shown to undergo a change in function during an inflammatory response include the sodium potassium ATPase, the epithelial sodium channel, the Cystic Fibrosis Transmembrane Conductance Regulator and calcium activated chloride channels and the sodium potassium chloride co-transporter. Inflammatory mediators, which influence ion transport are tumor necrosis factor, gamma interferon, interleukins, transforming growth factor, leukotrienes and bradykinin. They trigger the release of specific messengers like prostaglandins, nitric oxide and histamine which alter ion transport system function through specific receptors, intracellular second messengers and protein kinases. This review summarizes data on in vivo measurements of changes in ion transport in acute inflammatory conditions and in vitro studies, which have explored the underlying mechanisms. Potential interventions directed at a correction of the observed abnormalities are discussed. PMID:16571116

Pathophysiology of avian intestinal ion transport.

PubMed

Nighot, Meghali; Nighot, Prashant

2018-06-01

The gut has great importance for the commercial success of poultry production. Numerous ion transporters, exchangers, and channels are present on both the apical and the basolateral membrane of intestinal epithelial cells, and their differential expression along the crypt-villus axis within the various intestinal segments ensures efficient intestinal absorption and effective barrier function. Recent studies have shown that intensive production systems, microbial exposure, and nutritional management significantly affect intestinal physiology and intestinal ion transport. Dysregulation of normal intestinal ion transport is manifested as diarrhoea, malabsorption, and intestinal inflammation resulting into poor production efficiency. This review discusses the basic mechanisms involved in avian intestinal ion transport and the impact of development during growth, nutritional and environmental alterations, and intestinal microbial infections on it. The effect of intestinal microbial infections on avian intestinal ion transport depends on factors such as host immunity, pathogen virulence, and the mucosal organisation of the particular intestinal segment.

Effect of Mucin and Bicarbonate Ion on Corrosion Behavior of AZ31 Magnesium Alloy for Airway Stents

PubMed Central

Jang, Yongseok; Owuor, Daniel; Waterman, Jenora T.; White, Leon; Collins, Boyce; Sankar, Jagannathan; Gilbert, Thomas W.; Yun, Yeoheung

2014-01-01

The biodegradable ability of magnesium alloys is an attractive feature for tracheal stents since they can be absorbed by the body through gradual degradation after healing of the airway structure, which can reduce the risk of inflammation caused by long-term implantation and prevent the repetitive surgery for removal of existing stent. In this study, the effects of bicarbonate ion (HCO3−) and mucin in Gamble’s solution on the corrosion behavior of AZ31 magnesium alloy were investigated, using immersion and electrochemical tests to systematically identify the biodegradation kinetics of magnesium alloy under in vitro environment, mimicking the epithelial mucus surfaces in a trachea for development of biodegradable airway stents. Analysis of corrosion products after immersion test was performed using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). Electrochemical impedance spectroscopy (EIS) was used to identify the effects of bicarbonate ions and mucin on the corrosion behavior of AZ31 magnesium alloys with the temporal change of corrosion resistance. The results show that the increase of the bicarbonate ions in Gamble’s solution accelerates the dissolution of AZ31 magnesium alloy, while the addition of mucin retards the corrosion. The experimental data in this work is intended to be used as foundational knowledge to predict the corrosion behavior of AZ31 magnesium alloy in the airway environment while providing degradation information for future in vivo studies. PMID:28788166

Difficult airway simulator intubation success rates using Commission on Accreditation of Medical Transport systems training standards.

PubMed

Thomas, Frank; Rhoades, Carol; Carpenter, Judi; Holleran, Renee; Handrahan, Diana

2011-01-01

This study was undertaken to evaluate difficult airway simulator intubation success rates using Commission on Accreditation of Medical Transport Systems (CAMTS) initial and maintenance intubation training standards on transport-RN novice intubators over a 1-year period. Twelve transport nurses were blinded to and randomly assigned five or six of 64 different difficult airway simulator scenarios. Intubation success rates were measured 1 month before training, 1 month after training, and 1 year later, following CAMTS initial and maintenance intubation standards. Outcome measurements included first attempt intubation rate, overall intubation success rate, number of attempts to intubation, time per attempt, time to intubation, and time between attempts. During the study, participants received no additional training or opportunities to intubate. First-attempt intubation rates significantly improved (P 5 .022) from 19% 1 month before training to 36% 1 month after training, but did not significantly change (P > .999) 1 year later following CAMTS maintenance standards (34%). Mean cumulative success rates did not significantly improve after four attempts or after 3.5 minutes. The overall mean time per attempt and time between attempts declined with subsequent intubation attempts. Using initial and maintenance CAMTS standards, simulator difficult airway intubation success rates are low in novice intubators. Our results suggest that one intubation/quarter may be enough to maintain difficult airway intubation success rates. Training significantly improves intubation rates. Little advantage occurs in intubation rates after four attempts or 3.5 minutes. Copyright © 2011 Air Medical Journal Associates. Published by Elsevier Inc. All rights reserved.

Ion transport by primary cultures of canine tracheal epithelium: methodology, morphology, and electrophysiology.

PubMed

Welsh, M J

1985-01-01

Canine tracheal epithelial cells were isolated by enzymatic and mechanical dispersion and cultured on permeable supports. The cells formed confluent monolayers and retained most of the morphologic characteristics of the intact epithelium, including apical microvilli, apical tight junctions, and a moderately interdigitated lateral intercellular space. The cells also retained the functional properties of the epithelium. The monolayer responded to addition of isoproterenol with the characteristic changes in cellular electrical properties expected for stimulation of C1 secretion: isoproterenol increased transepithelial voltage, depolarized apical membrane voltage, and decreased both transepithelial resistance and the ratio of apical-to-basolateral membrane resistance. Examination of the cellular response to ion substitutions and inhibitors of C1 secretion indicate that the cultured monolayers retain the same cellular mechanisms of ion transport as the intact epithelium. Thus, primary cultures of tracheal epithelium may provide a useful preparation for future studies of the mechanism and regulation of C1 secretion by airway epithelia.

CFD Simulation and Experimental Validation of Fluid Flow and Particle Transport in a Model of Alveolated Airways

PubMed Central

Ma, Baoshun; Ruwet, Vincent; Corieri, Patricia; Theunissen, Raf; Riethmuller, Michel; Darquenne, Chantal

2009-01-01

Accurate modeling of air flow and aerosol transport in the alveolated airways is essential for quantitative predictions of pulmonary aerosol deposition. However, experimental validation of such modeling studies has been scarce. The objective of this study is to validate CFD predictions of flow field and particle trajectory with experiments within a scaled-up model of alveolated airways. Steady flow (Re = 0.13) of silicone oil was captured by particle image velocimetry (PIV), and the trajectories of 0.5 mm and 1.2 mm spherical iron beads (representing 0.7 to 14.6 μm aerosol in vivo) were obtained by particle tracking velocimetry (PTV). At twelve selected cross sections, the velocity profiles obtained by CFD matched well with those by PIV (within 1.7% on average). The CFD predicted trajectories also matched well with PTV experiments. These results showed that air flow and aerosol transport in models of human alveolated airways can be simulated by CFD techniques with reasonable accuracy. PMID:20161301

CFD Simulation and Experimental Validation of Fluid Flow and Particle Transport in a Model of Alveolated Airways.

PubMed

Ma, Baoshun; Ruwet, Vincent; Corieri, Patricia; Theunissen, Raf; Riethmuller, Michel; Darquenne, Chantal

2009-05-01

Accurate modeling of air flow and aerosol transport in the alveolated airways is essential for quantitative predictions of pulmonary aerosol deposition. However, experimental validation of such modeling studies has been scarce. The objective of this study is to validate CFD predictions of flow field and particle trajectory with experiments within a scaled-up model of alveolated airways. Steady flow (Re = 0.13) of silicone oil was captured by particle image velocimetry (PIV), and the trajectories of 0.5 mm and 1.2 mm spherical iron beads (representing 0.7 to 14.6 mum aerosol in vivo) were obtained by particle tracking velocimetry (PTV). At twelve selected cross sections, the velocity profiles obtained by CFD matched well with those by PIV (within 1.7% on average). The CFD predicted trajectories also matched well with PTV experiments. These results showed that air flow and aerosol transport in models of human alveolated airways can be simulated by CFD techniques with reasonable accuracy.

Defective postsecretory maturation of MUC5B mucin in cystic fibrosis airways

PubMed Central

Abdullah, Lubna H.; Evans, Jessica R.; Wang, T. Tiffany; Ford, Amina A.; Makhov, Alexander M.; Nguyen, Kristine; Coakley, Raymond D.; Griffith, Jack D.; Davis, C. William; Ballard, Stephen T.

2017-01-01

In cystic fibrosis (CF), airway mucus becomes thick and viscous, and its clearance from the airways is impaired. The gel-forming mucins undergo an ordered “unpacking/maturation” process after granular release that requires an optimum postsecretory environment, including hydration and pH. We hypothesized that this unpacking process is compromised in the CF lung due to abnormal transepithelial fluid transport that reduces airway surface hydration and alters ionic composition. Using human tracheobronchial epithelial cells derived from non-CF and CF donors and mucus samples from human subjects and domestic pigs, we investigated the process of postsecretory mucin unfolding/maturation, how these processes are defective in CF airways, and the probable mechanism underlying defective unfolding. First, we found that mucins released into a normal lung environment transform from a compact granular form to a linear form. Second, we demonstrated that this maturation process is defective in the CF airway environment. Finally, we demonstrated that independent of HCO3− and pH levels, airway surface dehydration was the major determinant of this abnormal unfolding process. This defective unfolding/maturation process after granular release suggests that the CF extracellular environment is ion/water depleted and likely contributes to abnormal mucus properties in CF airways prior to infection and inflammation. PMID:28352653

Emergency airway management in critically injured patients: a survey of U.S. aero-medical transport programs.

PubMed

James, Dorsha N; Voskresensky, Igor V; Jack, Meg; Cotton, Bryan A

2009-06-01

Pre-hospital airway management represents the intervention most likely to impact outcomes in critically injured patients. As such, airway management issues dominate quality improvement (QI) reviews of aero-medical programs. The purpose of this study was to evaluate current practice patterns of airway management in trauma among U.S. aero-medical service (AMS) programs. The Association of Air Medical Services (AAMS) Resource Guide from 2005 to 2006 was utilized to identify the e-mail addresses of all directors of U.S. aero-medical transport programs. Program directors from 182 U.S. aero-medical programs were asked to participate in an anonymous, web-based survey of emergency airway management protocols and practices. Non-responders to the initial request were contacted a second time by e-mail. 89 programs responded. 98.9% have rapid sequence intubation (RSI) protocols. 90% use succinylcholine, 70% use long-acting neuromuscular blockers (NMB) within their RSI protocol. 77% have protocols for mandatory in-flight sedation but only 13% have similar protocols for maintenance paralytics. 60% administer long-acting NMB immediately after RSI, 13% after confirmation of neurological activity. Given clinical scenarios, however, 97% administer long-acting NMB to patients with scene and in-flight Glasgow Coma Scale (GCS) of 3, even for brief transport times. The majority of AMS programs have well defined RSI and in-flight sedation protocols, while protocols for in-flight NMB are uncommon. Despite this, nearly all programs administer long-acting NMB following RSI, irrespective of GCS or flight time. Given the impact of in-flight NMB on initial assessment, early intervention, and injury severity scoring, a critical appraisal of current AMS airway management practices appears warranted.

Imaging elemental distribution and ion transport in cultured cells with ion microscopy.

PubMed

Chandra, S; Morrison, G H

1985-06-28

Both elemental distribution and ion transport in cultured cells have been imaged by ion microscopy. Morphological and chemical information was obtained with a spatial resolution of approximately 0.5 micron for sodium, potassium, calcium, and magnesium in freeze-fixed, cryofractured, and freeze-dried normal rat kidney cells and Chinese hamster ovary cells. Ion transport was successfully demonstrated by imaging Na+-K+ fluxes after the inhibition of Na+- and K+ -dependent adenosine triphosphatase with ouabain. This method allows measurements of elemental (isotopic) distribution to be related to cell morphology, thereby providing the means for studying ion distribution and ion transport under different physiological, pathological, and toxicological conditions in cell culture systems.

In Vivo Airway Surface Liquid Cl− Analysis with Solid-State Electrodes

PubMed Central

Caldwell, Ray A.; Grubb, Barbara R.; Tarran, Robert; Boucher, Richard C.; Knowles, Michael R.; Barker, Pierre M.

2002-01-01

The pathogenesis of cystic fibrosis (CF) airways disease remains controversial. Hypotheses that link mutations in CFTR and defects in ion transport to CF lung disease predict that alterations in airway surface liquid (ASL) isotonic volume, or ion composition, are critically important. ASL [Cl−] is pivotal in discriminating between these hypotheses, but there is no consensus on this value given the difficulty in measuring [Cl−] in the “thin” ASL (∼30 μm) in vivo. Consequently, a miniaturized solid-state electrode with a shallow depth of immersion was constructed to measure ASL [Cl−] in vivo. In initial experiments, the electrode measured [Cl−] in physiologic salt solutions, small volume (7.6 μl) test solutions, and in in vitro cell culture models, with ≥93% accuracy. Based on discrepancies in reported values and/or absence of data, ASL Cl− measurements were made in the following airway regions and species. First, ASL [Cl−] was measured in normal human nasal cavity and averaged 117.3 ± 11.2 mM (n = 6). Second, ASL [Cl−] measured in large airway (tracheobronchial) regions were as follows: rabbit trachea and bronchus = 114.3 ± 1.8 mM; (n = 6) and 126.9 ± 1.7 mM; (n = 3), respectively; mouse trachea = 112.8 ± 4.2 mM (n = 13); and monkey bronchus = 112.3 ± 10.9 mM (n = 3). Third, Cl− measurements were made in small (1–2 mm) diameter airways of the rabbit (108.3 ± 7.1 mM, n = 5) and monkey (128.5 ± 6.8 mM, n = 3). The measured [Cl−], in excess of 100 mM throughout all airway regions tested in multiple species, is consistent with the isotonic volume hypothesis to describe ASL physiology. PMID:11773234

Regulation of ion transport by microRNAs.

PubMed

Elvira-Matelot, Emilie; Jeunemaitre, Xavier; Hadchouel, Juliette

2011-09-01

This review aims to describe the recent findings obtained on the regulation of ion transport by microRNAs in physiological and pathological situations in different organs and organisms. The number of ion channels or transporters can be regulated by increasing or decreasing the transcription and/or translation of the corresponding genes. In this context, a new class of regulators of gene expression has emerged as an important modulator of ion transport. microRNAs are short noncoding RNAs which inhibit gene expression by enhancing the degradation or inhibiting the translation of their targets. Most of the studies published so far describe their roles during embryonic development and tumorigenesis. However, recent studies have started to unravel how microRNA-mediated modulation of ion transport could contribute not only to the development of pathological states, such as heart disease, but also to the osmotic regulation of various organisms. The contribution of microRNAs to the regulation of ion transport has only begun to be unraveled, mostly in cardiomyocytes. Only a few studies have focused on the kidney but they strongly suggest that microRNAs could play an important role in the regulation of renal ion transport in response to variation in daily food intake.

Faster Heavy Ion Transport for HZETRN

NASA Technical Reports Server (NTRS)

Slaba, Tony C.

2013-01-01

The deterministic particle transport code HZETRN was developed to enable fast and accurate space radiation transport through materials. As more complex transport solutions are implemented for neutrons, light ions (Z < 2), mesons, and leptons, it is important to maintain overall computational efficiency. In this work, the heavy ion (Z > 2) transport algorithm in HZETRN is reviewed, and a simple modification is shown to provide an approximate 5x decrease in execution time for galactic cosmic ray transport. Convergence tests and other comparisons are carried out to verify that numerical accuracy is maintained in the new algorithm.

Numerical Simulation of Ion Transport in a Nano-Electrospray Ion Source at Atmospheric Pressure

NASA Astrophysics Data System (ADS)

Wang, Wei; Bajic, Steve; John, Benzi; Emerson, David R.

2018-03-01

Understanding ion transport properties from the ion source to the mass spectrometer (MS) is essential for optimizing device performance. Numerical simulation helps in understanding of ion transport properties and, furthermore, facilitates instrument design. In contrast to previously reported numerical studies, ion transport simulations in a continuous injection mode whilst considering realistic space-charge effects have been carried out. The flow field was solved using Reynolds-averaged Navier-Stokes (RANS) equations, and a particle-in-cell (PIC) method was applied to solve a time-dependent electric field with local charge density. A series of ion transport simulations were carried out at different cone gas flow rates, ion source currents, and capillary voltages. A force evaluation analysis reveals that the electric force, the drag force, and the Brownian force are the three dominant forces acting on the ions. Both the experimental and simulation results indicate that cone gas flow rates of ≤250 slph (standard liter per hour) are important for high ion transmission efficiency, as higher cone gas flow rates reduce the ion signal significantly. The simulation results also show that the ion transmission efficiency reduces exponentially with an increased ion source current. Additionally, the ion loss due to space-charge effects has been found to be predominant at a higher ion source current, a lower capillary voltage, and a stronger cone gas counterflow. The interaction of the ion driving force, ion opposing force, and ion dispersion is discussed to illustrate ion transport mechanism in the ion source at atmospheric pressure. [Figure not available: see fulltext.

Numerical Simulation of Ion Transport in a Nano-Electrospray Ion Source at Atmospheric Pressure.

PubMed

Wang, Wei; Bajic, Steve; John, Benzi; Emerson, David R

2018-03-01

Understanding ion transport properties from the ion source to the mass spectrometer (MS) is essential for optimizing device performance. Numerical simulation helps in understanding of ion transport properties and, furthermore, facilitates instrument design. In contrast to previously reported numerical studies, ion transport simulations in a continuous injection mode whilst considering realistic space-charge effects have been carried out. The flow field was solved using Reynolds-averaged Navier-Stokes (RANS) equations, and a particle-in-cell (PIC) method was applied to solve a time-dependent electric field with local charge density. A series of ion transport simulations were carried out at different cone gas flow rates, ion source currents, and capillary voltages. A force evaluation analysis reveals that the electric force, the drag force, and the Brownian force are the three dominant forces acting on the ions. Both the experimental and simulation results indicate that cone gas flow rates of ≤250 slph (standard liter per hour) are important for high ion transmission efficiency, as higher cone gas flow rates reduce the ion signal significantly. The simulation results also show that the ion transmission efficiency reduces exponentially with an increased ion source current. Additionally, the ion loss due to space-charge effects has been found to be predominant at a higher ion source current, a lower capillary voltage, and a stronger cone gas counterflow. The interaction of the ion driving force, ion opposing force, and ion dispersion is discussed to illustrate ion transport mechanism in the ion source at atmospheric pressure. Graphical Abstract.

Ion transport in a pH-regulated nanopore.

PubMed

Yeh, Li-Hsien; Zhang, Mingkan; Qian, Shizhi

2013-08-06

Fundamental understanding of ion transport phenomena in nanopores is crucial for designing the next-generation nanofluidic devices. Due to surface reactions of dissociable functional groups on the nanopore wall, the surface charge density highly depends upon the proton concentration on the nanopore wall, which in turn affects the electrokinetic transport of ions, fluid, and particles within the nanopore. Electrokinetic ion transport in a pH-regulated nanopore, taking into account both multiple ionic species and charge regulation on the nanopore wall, is theoretically investigated for the first time. The model is verified by the experimental data of nanopore conductance available in the literature. The results demonstrate that the spatial distribution of the surface charge density at the nanopore wall and the resulting ion transport phenomena, such as ion concentration polarization (ICP), ion selectivity, and conductance, are significantly affected by the background solution properties, such as the pH and salt concentration.

Pharmacological treatment of the ion transport defect in cystic fibrosis.

PubMed

Roomans, G M

2001-01-01

Cystic fibrosis (CF) is a lethal monogenetic disease characterised by impaired water and ion transport over epithelia. The lung pathology is fatal and causes death in 95% of CF patients. The genetic basis of the disease is a mutation in the cystic fibrosis transmembrane conductance regulator (CFTR), a cAMP-regulated chloride channel. The most common mutation, DeltaF508, results in a protein that cannot properly be folded in the endoplasmic reticulum, is destroyed and hence does not reach the apical cell membrane. This paper will discuss those pharmacological approaches that are directed at correcting the defect in ion transport. At present, no clinically effective drug is available, although research has defined areas in which progress might be made. These are the following: (1) the drug 4-phenylbutyrate (4PBA) increases the expression of DeltaF508-CFTR in the cell membrane, probably by breaking the association between DeltaF508-CFTR and a chaperone; (2) a number of xanthines, in particular 8-cyclopentyl-1, 3-dipropylxanthine (CPX), are effective in activating CFTR, presumably by direct binding and also possibly by correcting the trafficking defect; (3) the isoflavone genistein can activate both wild-type and mutant CFTR, probably through direct binding to the channel; (4) purinergic agonists (ATP and UTP) can stimulate chloride secretion via a Ca(2+)-dependent chloride channel and in this way compensate for the defect in CFTR, but stable analogues will be required before this type of treatment has clinical significance; (5) treatment with inhaled amiloride may correct the excessive absorption of Na(+) ions and water by airway epithelial cells that appears connected to the defect in CFTR; although clinical tests have not been very successful so far, amiloride analogues with a longer half-life may give better results. The role of CFTR in bicarbonate secretion has not yet been established with certainty, but correction of the defect in bicarbonate secretion may be

Dextran Sulfate Sodium-Induced Colonic Histopathology, but not Altered Epithelial Ion Transport, Is Reduced by Inhibition of Phosphodiesterase Activity

PubMed Central

Diaz-Granados, Natalia; Howe, Kathryn; Lu, Jun; McKay, Derek M.

2000-01-01

Inhibition of phosphodiesterase (PDE) activity is beneficial in models of arthritis and airway inflammation. Here we assessed the ability of PDE inhibitors to modulate colitis by exposing mice to 4% (w/v) dextran sulfate sodium (DSS) drinking water for 5 days with or without rolipram, an inhibitor of PDE type 4, or the nonselective PDE inhibitor, pentoxifylline (both at 5 mg/kg, i.p., twice daily). Controls received saline, vehicle, or drug only. Colonic histology, myeloperoxidase (MPO) and tumor necrosis factor-α (TNF-α) levels, and epithelial ion transport (baseline and stimulated by electrical nerve stimulation, carbachol, and forskolin) were examined. DSS-treated mice displayed a variable diarrhea, significant histopathology in the mid-distal colon, elevated MPO activity, and reduced (>50%) responses to all three pro-secretory stimuli. Treatment with rolipram, and to a lesser extent pentoxifylline, significantly reduced the severity of the colonic histopathology and MPO levels. Neither PDE inhibitor had any affect on the diminished ion transport events caused by DSS-induced colitis. However, although stimulated ion transport events were still reduced 3 days after DSS treatment, colonic segments from DSS + rolipram-treated mice displayed enhanced recovery in their secretory responsiveness, particularly to carbachol. These findings indicate that specific PDE4 inhibition can significantly reduce the tissue damage that accompanies colitis and enhance recovery of normal colonic function. PMID:10854237

Reversible ion transportation switch by a ligand-gated synthetic supramolecular ion channel.

PubMed

Muraoka, Takahiro; Endo, Takahiro; Tabata, Kazuhito V; Noji, Hiroyuki; Nagatoishi, Satoru; Tsumoto, Kouhei; Li, Rui; Kinbara, Kazushi

2014-11-05

Inspired by the regulation of cellular activities found in the ion channel proteins, here we developed membrane-embedded synthetic chiral receptors 1 and 2 with different terminal structures, where receptor 1 has hydrophobic triisopropylsilyl (TIPS) groups and receptor 2 has hydrophilic hydroxy groups. The receptors have ligand-binding units that interact with cationic amphiphiles such as 2-phenethylamine (PA). Conductance study revealed that the receptors hardly show ion transportation at the ligand-free state. After ligand binding involving a conformational change, receptor 1 bearing TIPS termini displays a significant current enhancement due to ion transportation. The current substantially diminishes upon addition of β-cyclodextrin (βCD) that scavenges the ligand from the receptor. Importantly, the receptor again turns into the conductive state by the second addition of PA, and the activation/deactivation of the ion transportation can be repeated. In contrast, receptor 2 bearing the hydroxy terminal groups hardly exhibits ion transportation, suggesting the importance of terminal TIPS groups of 1 that likely anchor the receptor in the membrane.

SLC26A9-mediated chloride secretion prevents mucus obstruction in airway inflammation

PubMed Central

Anagnostopoulou, Pinelopi; Riederer, Brigitte; Duerr, Julia; Michel, Sven; Binia, Aristea; Agrawal, Raman; Liu, Xuemei; Kalitzki, Katrin; Xiao, Fang; Chen, Mingmin; Schatterny, Jolanthe; Hartmann, Dorothee; Thum, Thomas; Kabesch, Michael; Soleimani, Manoocher; Seidler, Ursula; Mall, Marcus A.

2012-01-01

Asthma is a chronic condition with unknown pathogenesis, and recent evidence suggests that enhanced airway epithelial chloride (Cl–) secretion plays a role in the disease. However, the molecular mechanism underlying Cl– secretion and its relevance in asthma pathophysiology remain unknown. To determine the role of the solute carrier family 26, member 9 (SLC26A9) Cl– channel in asthma, we induced Th2-mediated inflammation via IL-13 treatment in wild-type and Slc26a9-deficient mice and compared the effects on airway ion transport, morphology, and mucus content. We found that IL-13 treatment increased Cl– secretion in the airways of wild-type but not Slc26a9-deficient mice. While IL-13–induced mucus overproduction was similar in both strains, treated Slc26a9-deficient mice exhibited airway mucus obstruction, which did not occur in wild-type controls. In a study involving healthy children and asthmatics, a polymorphism in the 3′ UTR of SLC26A9 that reduced protein expression in vitro was associated with asthma. Our data demonstrate that the SLC26A9 Cl– channel is activated in airway inflammation and suggest that SLC26A9-mediated Cl– secretion is essential for preventing airway obstruction in allergic airway disease. These results indicate that SLC26A9 may serve as a therapeutic target for airway diseases associated with mucus plugging. PMID:22945630

78 FR 19024 - Lithium Ion Batteries in Transportation Public Forum

Federal Register 2010, 2011, 2012, 2013, 2014

2013-03-28

... NATIONAL TRANSPORTATION SAFETY BOARD Lithium Ion Batteries in Transportation Public Forum On... forum titled, ``Lithium Ion Batteries in Transportation.'' The forum will begin at 9:00 a.m. on both... battery design, development, and use; Lithium ion battery regulations and standards; and Lithium ion...

Supramolecular gating of ion transport in nanochannels.

PubMed

Kumar, B V V S Pavan; Rao, K Venkata; Sampath, S; George, Subi J; Eswaramoorthy, Muthusamy

2014-11-24

Several covalent strategies towards surface charge-reversal in nanochannels have been reported with the purpose of manipulating ion transport. However, covalent routes lack dynamism, modularity and post-synthetic flexibility, and hence restrict their applicability in different environments. Here, we introduce a facile non-covalent approach towards charge-reversal in nanochannels (<10 nm) using strong charge-transfer interactions between dicationic viologen (acceptor) and trianionic pyranine (donor). The polarity of ion transport was switched from anion selective to ambipolar to cation selective by controlling the extent of viologen bound to the pyranine. We could also regulate the ion transport with respect to pH by selecting a donor with pH-responsive functional groups. The modularity of this approach further allows facile integration of various functional groups capable of responding to stimuli such as light and temperature to modulate the transport of ions as well as molecules. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Substrate Profile and Metal-ion Selectivity of Human Divalent Metal-ion Transporter-1*

PubMed Central

Illing, Anthony C.; Shawki, Ali; Cunningham, Christopher L.; Mackenzie, Bryan

2012-01-01

Divalent metal-ion transporter-1 (DMT1) is a H+-coupled metal-ion transporter that plays essential roles in iron homeostasis. DMT1 exhibits reactivity (based on evoked currents) with a broad range of metal ions; however, direct measurement of transport is lacking for many of its potential substrates. We performed a comprehensive substrate-profile analysis for human DMT1 expressed in RNA-injected Xenopus oocytes by using radiotracer assays and the continuous measurement of transport by fluorescence with the metal-sensitive PhenGreen SK fluorophore. We provide validation for the use of PhenGreen SK fluorescence quenching as a reporter of cellular metal-ion uptake. We determined metal-ion selectivity under fixed conditions using the voltage clamp. Radiotracer and continuous measurement of transport by fluorescence assays revealed that DMT1 mediates the transport of several metal ions that were ranked in selectivity by using the ratio Imax/K0.5 (determined from evoked currents at −70 mV): Cd2+ > Fe2+ > Co2+, Mn2+ ≫ Zn2+, Ni2+, VO2+. DMT1 expression did not stimulate the transport of Cr2+, Cr3+, Cu+, Cu2+, Fe3+, Ga3+, Hg2+, or VO+. 55Fe2+ transport was competitively inhibited by Co2+ and Mn2+. Zn2+ only weakly inhibited 55Fe2+ transport. Our data reveal that DMT1 selects Fe2+ over its other physiological substrates and provides a basis for predicting the contribution of DMT1 to intestinal, nasal, and pulmonary absorption of metal ions and their cellular uptake in other tissues. Whereas DMT1 is a likely route of entry for the toxic heavy metal cadmium, and may serve the metabolism of cobalt, manganese, and vanadium, we predict that DMT1 should contribute little if at all to the absorption or uptake of zinc. The conclusion in previous reports that copper is a substrate of DMT1 is not supported. PMID:22736759

Electro- and Magneto-Modulated Ion Transport through Graphene Oxide Membranes

PubMed Central

Sun, Pengzhan; Zheng, Feng; Wang, Kunlin; Zhong, Minlin; Wu, Dehai; Zhu, Hongwei

2014-01-01

The control of ion trans-membrane transport through graphene oxide (GO) membranes is achieved by electric and magnetic fields. Electric field can either increase or decrease the ion transport through GO membranes depending on its direction, and magnetic field can enhance the ion penetration monotonically. When electric field is applied across GO membrane, excellent control of ion fluidic flows can be done. With the magnetic field, the effective anchoring of ions is demonstrated but the modulation of the ion flowing directions does not occur. The mechanism of the electro- and magneto-modulated ion trans-membrane transport is investigated, indicating that the electric fields dominate the ion migration process while the magnetic fields tune the structure of nanocapillaries within GO membranes. Results also show that the ion selectivity of GO membranes can be tuned with the electric fields while the transport of ions can be enhanced synchronously with the magnetic fields. These excellent properties make GO membranes promising in areas such as field-induced mass transport control and membrane separation. PMID:25347969

Liners for ion transport membrane systems

DOEpatents

Carolan, Michael Francis; Miller, Christopher Francis

2010-08-10

Ion transport membrane system comprising (a) a pressure vessel comprising an interior, an exterior, an inlet, an inlet conduit, an outlet, and an outlet conduit; (b) a plurality of planar ion transport membrane modules disposed in the interior of the pressure vessel and arranged in series, each membrane module comprising mixed metal oxide ceramic material and having an interior region and an exterior region, wherein the inlet and the outlet of the pressure vessel are in flow communication with exterior regions of the membrane modules; (c) a gas manifold having an interior surface wherein the gas manifold is in flow communication with the interior region of each of the planar ion transport membrane modules and with the exterior of the pressure vessel; and (d) a liner disposed within any of the inlet conduit, the outlet conduit, and the interior surface of the gas manifold.

Nondiffusive transport regimes for suprathermal ions in turbulent plasmas

NASA Astrophysics Data System (ADS)

Bovet, A.; Fasoli, A.; Ricci, P.; Furno, I.; Gustafson, K.

2015-04-01

The understanding of the transport of suprathermal ions in the presence of turbulence is important for fusion plasmas in the burning regime that will characterize reactors, and for space plasmas to understand the physics of particle acceleration. Here, three-dimensional measurements of a suprathermal ion beam in the toroidal plasma device TORPEX are presented. These measurements demonstrate, in a turbulent plasma, the existence of subdiffusive and superdiffusive transport of suprathermal ions, depending on their energy. This result stems from the unprecedented combination of uniquely resolved measurements and first-principles numerical simulations that reveal the mechanisms responsible for the nondiffusive transport. The transport regime is determined by the interaction of the suprathermal ion orbits with the turbulent plasma dynamics, and is strongly affected by the ratio of the suprathermal ion energy to the background plasma temperature.

Airway epithelial wounds in rhesus monkey generate ionic currents that guide cell migration to promote healing

PubMed Central

Sun, Yao-Hui; Reid, Brian; Fontaine, Justin H.; Miller, Lisa A.; Hyde, Dallas M.; Mogilner, Alex

2011-01-01

Damage to the respiratory epithelium is one of the most critical steps to many life-threatening diseases, such as acute respiratory distress syndrome and chronic obstructive pulmonary disease. The mechanisms underlying repair of the damaged epithelium have not yet been fully elucidated. Here we provide experimental evidence suggesting a novel mechanism for wound repair: endogenous electric currents. It is known that the airway epithelium maintains a voltage difference referred to as the transepithelial potential. Using a noninvasive vibrating probe, we demonstrate that wounds in the epithelium of trachea from rhesus monkeys generate significant outward electric currents. A small slit wound produced an outward current (1.59 μA/cm2), which could be enhanced (nearly doubled) by the ion transport stimulator aminophylline. In addition, inhibiting cystic fibrosis transmembrane conductance regulator (CFTR) with CFTR(Inh)-172 significantly reduced wound currents (0.17 μA/cm2), implicating an important role of ion transporters in wound induced electric potentials. Time-lapse video microscopy showed that applied electric fields (EFs) induced robust directional migration of primary tracheobronchial epithelial cells from rhesus monkeys, towards the cathode, with a threshold of <23 mV/mm. Reversal of the field polarity induced cell migration towards the new cathode. We further demonstrate that application of an EF promoted wound healing in a monolayer wound healing assay. Our results suggest that endogenous electric currents at sites of tracheal epithelial injury may direct cell migration, which could benefit restitution of damaged airway mucosa. Manipulation of ion transport may lead to novel therapeutic approaches to repair damaged respiratory epithelium. PMID:21719726

Altered ion transport in normal human bronchial epithelial cells following exposure to chemically distinct metal welding fume particles.

PubMed

Fedan, Jeffrey S; Thompson, Janet A; Meighan, Terence G; Zeidler-Erdely, Patti C; Antonini, James M

2017-07-01

Welding fume inhalation causes pulmonary toxicity, including susceptibility to infection. We hypothesized that airway epithelial ion transport is a target of fume toxicity, and investigated the effects of fume particulates from manual metal arc-stainless steel (MMA-SS) and gas metal arc-mild steel (GMA-MS) on ion transport in normal human bronchial epithelium (NHBE) cultured in air-interface. MMA-SS particles, more soluble than GMA-MS particles, contain Cr, Ni, Fe and Mn; GMA-MS particles contain Fe and Mn. MMA-SS or GMA-MS particles (0.0167-166.7μg/cm 2 ) were applied apically to NHBEs. After 18h transepithelial potential difference (V t ), resistance (R t ), and short circuit current (I sc ) were measured. Particle effects on Na + and Cl¯ channels and the Na + ,K + ,2Cl¯-cotransporter were evaluated using amiloride (apical), 5-nitro-2-[(3-phenylpropyl)amino]benzoic acid (NPPB, apical), and bumetanide (basolateral), respectively. MMA-SS (0.0167-16.7μg/cm 2 ) increased basal V t . Only 16.7μg/cm 2 GMA-MS increased basal V t significantly. MMA-SS or GMA-MS exposure potentiated I sc responses (decreases) to amiloride and bumetanide, while not affecting those to NPPB, GMA-MS to a lesser degree than MMA-SS. Variable effects on R t were observed in response to amiloride, and bumetanide. Generally, MMA-SS was more potent in altering responses to amiloride and bumetanide than GMA-MS. Hyperpolarization occurred in the absence of LDH release, but decreases in V t , R t , and I sc at higher fume particulate doses accompanied LDH release, to a greater extent for MMA-SS. Thus, Na + transport and Na + ,K + ,2Cl¯-cotransport are affected by fume exposure; MMA-MS is more potent than GMA-MS. Enhanced Na + absorption and decreased airway surface liquid could compromise defenses against infection. Published by Elsevier Inc.

Benchmarking of Heavy Ion Transport Codes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Remec, Igor; Ronningen, Reginald M.; Heilbronn, Lawrence

Accurate prediction of radiation fields generated by heavy ion interactions is important in medical applications, space missions, and in designing and operation of rare isotope research facilities. In recent years, several well-established computer codes in widespread use for particle and radiation transport calculations have been equipped with the capability to simulate heavy ion transport and interactions. To assess and validate these capabilities, we performed simulations of a series of benchmark-quality heavy ion experiments with the computer codes FLUKA, MARS15, MCNPX, and PHITS. We focus on the comparisons of secondary neutron production. Results are encouraging; however, further improvements in models andmore » codes and additional benchmarking are required.« less

Cholinergic regulation of epithelial ion transport in the mammalian intestine

PubMed Central

Hirota, C L; McKay, D M

2006-01-01

Acetylcholine (ACh) is critical in controlling epithelial ion transport and hence water movements for gut hydration. Here we review the mechanism of cholinergic control of epithelial ion transport across the mammalian intestine. The cholinergic nervous system affects basal ion flux and can evoke increased active ion transport events. Most studies rely on measuring increases in short-circuit current (ISC = active ion transport) evoked by adding ACh or cholinomimetics to intestinal tissue mounted in Ussing chambers. Despite subtle species and gut regional differences, most data indicate that, under normal circumstances, the effect of ACh on intestinal ion transport is mainly an increase in Cl- secretion due to interaction with epithelial M3 muscarinic ACh receptors (mAChRs) and, to a lesser extent, neuronal M1 mAChRs; however, AChR pharmacology has been plagued by a lack of good receptor subtype-selective compounds. Mice lacking M3 mAChRs display intact cholinergically-mediated intestinal ion transport, suggesting a possible compensatory mechanism. Inflamed tissues often display perturbations in the enteric cholinergic system and reduced intestinal ion transport responses to cholinomimetics. The mechanism(s) underlying this hyporesponsiveness are not fully defined. Inflammation-evoked loss of mAChR-mediated control of epithelial ion transport in the mouse reveals a role for neuronal nicotinic AChRs, representing a hitherto unappreciated braking system to limit ACh-evoked Cl- secretion. We suggest that: i) pharmacological analyses should be supported by the use of more selective compounds and supplemented with molecular biology techniques targeting specific ACh receptors and signalling molecules, and ii) assessment of ion transport in normal tissue must be complemented with investigations of tissues from patients or animals with intestinal disease to reveal control mechanisms that may go undetected by focusing on healthy tissue only. PMID:16981004

Hypercapnia modulates cAMP signalling and cystic fibrosis transmembrane conductance regulator‐dependent anion and fluid secretion in airway epithelia

PubMed Central

Turner, Mark J.; Saint‐Criq, Vinciane; Patel, Waseema; Ibrahim, Salam H.; Verdon, Bernard; Ward, Christopher; Garnett, James P.; Tarran, Robert; Cann, Martin J.

2015-01-01

Key points Raised arterial blood CO2 (hypercapnia) is a feature of many lung diseases.CO2 has been shown to act as a cell signalling molecule in human cells, notably by influencing the levels of cell signalling second messengers: cAMP and Ca2+.Hypercapnia reduced cAMP‐stimulated cystic fibrosis transmembrane conductance regulator‐dependent anion and fluid transport in Calu‐3 cells and primary human airway epithelia but did not affect cAMP‐regulated HCO3 − transport via pendrin or Na+/HCO3 − cotransporters.These results further support the role of CO2 as a cell signalling molecule and suggests CO2‐induced reductions in airway anion and fluid transport may impair innate defence mechanisms of the lungs. Abstract Hypercapnia is clinically defined as an arterial blood partial pressure of CO2 of above 40 mmHg and is a feature of chronic lung disease. In previous studies we have demonstrated that hypercapnia modulates agonist‐stimulated cAMP levels through effects on transmembrane adenylyl cyclase activity. In the airways, cAMP is known to regulate cystic fibrosis transmembrane conductance regulator (CFTR)‐mediated anion and fluid secretion, which contributes to airway surface liquid homeostasis. The aim of the current work was to investigate if hypercapnia could modulate cAMP‐regulated ion and fluid transport in human airway epithelial cells. We found that acute exposure to hypercapnia significantly reduced forskolin‐stimulated elevations in intracellular cAMP as well as both adenosine‐ and forskolin‐stimulated increases in CFTR‐dependent transepithelial short‐circuit current, in polarised cultures of Calu‐3 human airway cells. This CO2‐induced reduction in anion secretion was not due to a decrease in HCO3 − transport given that neither a change in CFTR‐dependent HCO3 − efflux nor Na+/HCO3 − cotransporter‐dependent HCO3 − influx were CO2‐sensitive. Hypercapnia also reduced the volume of forskolin‐stimulated fluid

High-Fidelity Preservation of Quantum Information During Trapped-Ion Transport

NASA Astrophysics Data System (ADS)

Kaufmann, Peter; Gloger, Timm F.; Kaufmann, Delia; Johanning, Michael; Wunderlich, Christof

2018-01-01

A promising scheme for building scalable quantum simulators and computers is the synthesis of a scalable system using interconnected subsystems. A prerequisite for this approach is the ability to faithfully transfer quantum information between subsystems. With trapped atomic ions, this can be realized by transporting ions with quantum information encoded into their internal states. Here, we measure with high precision the fidelity of quantum information encoded into hyperfine states of a Yb171 + ion during ion transport in a microstructured Paul trap. Ramsey spectroscopy of the ion's internal state is interleaved with up to 4000 transport operations over a distance of 280 μ m each taking 12.8 μ s . We obtain a state fidelity of 99.9994 (-7+6) % per ion transport.

Ion transport controlled by nanoparticle-functionalized membranes.

PubMed

Barry, Edward; McBride, Sean P; Jaeger, Heinrich M; Lin, Xiao-Min

2014-12-17

From proton exchange membranes in fuel cells to ion channels in biological membranes, the well-specified control of ionic interactions in confined geometries profoundly influences the transport and selectivity of porous materials. Here we outline a versatile new approach to control a membrane's electrostatic interactions with ions by depositing ligand-coated nanoparticles around the pore entrances. Leveraging the flexibility and control by which ligated nanoparticles can be synthesized, we demonstrate how ligand terminal groups such as methyl, carboxyl and amine can be used to tune the membrane charge density and control ion transport. Further functionality, exploiting the ligands as binding sites, is demonstrated for sulfonate groups resulting in an enhancement of the membrane charge density. We then extend these results to smaller dimensions by systematically varying the underlying pore diameter. As a whole, these results outline a previously unexplored method for the nanoparticle functionalization of membranes using ligated nanoparticles to control ion transport.

Ion transport controlled by nanoparticle-functionalized membranes

NASA Astrophysics Data System (ADS)

Barry, Edward; McBride, Sean P.; Jaeger, Heinrich M.; Lin, Xiao-Min

2014-12-01

From proton exchange membranes in fuel cells to ion channels in biological membranes, the well-specified control of ionic interactions in confined geometries profoundly influences the transport and selectivity of porous materials. Here we outline a versatile new approach to control a membrane’s electrostatic interactions with ions by depositing ligand-coated nanoparticles around the pore entrances. Leveraging the flexibility and control by which ligated nanoparticles can be synthesized, we demonstrate how ligand terminal groups such as methyl, carboxyl and amine can be used to tune the membrane charge density and control ion transport. Further functionality, exploiting the ligands as binding sites, is demonstrated for sulfonate groups resulting in an enhancement of the membrane charge density. We then extend these results to smaller dimensions by systematically varying the underlying pore diameter. As a whole, these results outline a previously unexplored method for the nanoparticle functionalization of membranes using ligated nanoparticles to control ion transport.

Turbulent Transport of Fast Ions in the Large Plasma Device (LAPD)

NASA Astrophysics Data System (ADS)

Zhou, Shu; Heidbrink, William; McWilliams, Roger; Boehmer, Heinrich; Carter, Troy; Popovich, Pavel; Tripathi, Shreekrishna; Vincena, Steve; Jenko, Frank

2010-11-01

Due to gyroradius averaging and drift-orbit averaging, the transport of fast ions by microturbulence is often smaller than for thermal ions. In this experiment, Strong drift wave turbulence is observed in LAPD on gradients produced by a plate obstacle. Energetic lithium ions orbit through the turbulent region. Scans with a collimated analyzer and with probes give detailed profiles of the fast ion spatial distribution and of the fluctuating fields. The fast-ion transport decreases rapidly with increasing fast-ion gyroradius. Unlike the diffusive transport caused by Coulomb collisions, in this case the turbulent transport is non-diffusive. Analysis and simulation suggest that the fast ions interact ballistically with stationary two-dimensional electrostatic turbulence. The energy dependence of the transport is well explained by gyro-averaging theory. In new experiments, different sources and obstacles alter the drift-wave turbulence to modify the nature of the transport.

Fast Lithium-Ion Transportation in Crystalline Polymer Electrolytes.

PubMed

Fu, Xiao-Bin; Yang, Guang; Wu, Jin-Ze; Wang, Jia-Chen; Chen, Qun; Yao, Ye-Feng

2018-01-05

Fast lithium-ion transportation is found in the crystalline polymer electrolytes, α-CD-PEO n /Li + (n=12, 40), prepared by self-assembly of α-cyclodextrin (CD), polyethylene oxide (PEO) and Li + salts. A detailed solid-state NMR study combined with the X-ray diffraction technique reveals the unique structural features of the samples, that is, a) the tunnel structure formed by the assembled CDs, providing the ordered long-range pathway for Li + ion transportation; b) the all-trans conformational sequence of the PEO chains in the tunnels, attenuating significantly the coordination between Li + and the EO segments. The origin of the fast lithium-ion transportation has been attributed to these unique structural features. This work demonstrates the first example in solid polymer electrolytes (SPEs) for "creating" fast ion transportation through material design and will find potential applications in the design of new ionconducting SPE materials. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Transport of ions using RF Carpets in Helium Gas

NASA Astrophysics Data System (ADS)

Lambert, Keenan; Kelly, James; Brodeur, Maxime

2017-09-01

Radio-Frequency (RF) carpet are critical components of large volume gas cells used to thermalize radioactive ion beams produced at in-flight facilities. RF carpets are formed by a series of co-centric conductive rings on which an alternating potential (in the radio-frequency range) is applied with opposite polarity on adjacent rings. This results in a strong repelling force that keep the ions a certain distance from the carpet. The transport of ions using RF carpet is accomplished using either a potential gradient applied on the individual all strips or traveling wave (using the so-called `ion surfing method'). A test setup has been constructed at the University of Notre Dame to perform studies on the repelling of ions using RF carpets. This test setup has recently been improved by the addiction of circuitry elements allowing the transport of ions using the ion surfing method. The developed circuitry, together with transport results for various ion beam currents, electric force applied on the ions, and traveling wave amplitude and speed will be presented

Metrology and Transport of Multiply Charged Ions

NASA Astrophysics Data System (ADS)

Kulkarni, Dhruva

The transport and interaction of singly- and multiply-charged ions with matter has been studied. The experiments were performed in an ultra-high vacuum environment. The low- and hyperthermal-energy ion beamline was used as a source of singly charged ions, while the CUEBIT facility was used as a source of multiply charged ions. The kinetic energy of the ion beam obtained from the CUEBIT is offset from the nominal value expected from the applied electrostatic potentials. These offsets were studied by measuring the kinetic energy of the beam using a retarding field analyzer (RFA). The offset was attributed to the space charge of the electron beam that is used to create the multiply charged ions. The charge density of the electron beam was varied by changing operational parameters of the electron beam, namely the electron beam current and the energy of the electron beam. Ion beams of Ar4+ and Ar8+ were extracted from the source and the offsets observed in the kinetic energy were related to the variation in the space charge potential of the electron beam. Measurements of these offsets, ranging from 100 eV/Q to 300 eV/Q, are significant and important for experiments that aim to utilize the potential energy of slow multiply charged ions. The transport of ions using capillaries has been studied to investigate the viability of ion-guiding as a means for a novel ion delivery mechanism. Results on transport through large bore capillaries (macrocapillaries) that probe both the geometric and ionguided mechanisms are presented. The angle- and position-dependent transport properties were found to depend on the material of the capillary (specifically, whether metal or insulator) and the geometry of the capillary. Rb+ ions at a kinetic energy of 1 keV were transmitted through metal and glass capillaries that were a few centimeters in length and a few millimeters in diameter. Oscillations were observed in the capillaries made of glass which were absent in the metal capillaries

Research of transport and deposition of aerosol in human airway replica

NASA Astrophysics Data System (ADS)

Lizal, Frantisek; Jedelsky, Jan; Elcner, Jakub; Durdina, Lukas; Halasova, Tereza; Mravec, Filip; Jicha, Miroslav

2012-04-01

Growing concern about knowledge of aerosol transport in human lungs is caused by great potential of use of inhaled pharmaceuticals. Second substantial motive for the research is an effort to minimize adverse effects of particular matter emitted by traffic and industry on human health. We created model geometry of human lungs to 7th generation of branching. This model geometry was used for fabrication of two physical models. The first one is made from thin walled transparent silicone and it allows a measurement of velocity and size of aerosol particles by Phase Doppler Anemometry (PDA). The second one is fabricated by stereolithographic method and it is designed for aerosol deposition measurements. We provided a series of measurements of aerosol transport in the transparent model and we ascertained remarkable phenomena linked with lung flow. The results are presented in brief. To gather how this phenomena affects aerosol deposition in human lungs we used the second model and we developed a technique for deposition fraction and deposition efficiency assessment. The results confirmed that non-symmetric and complicated shape of human airways essentially affects transport and deposition of aerosol. The research will now focus on deeper insight in aerosol deposition.

Chamber transport for heavy ion fusion

NASA Astrophysics Data System (ADS)

Olson, Craig L.

2014-01-01

A brief review is given of research on chamber transport for HIF (heavy ion fusion) dating from the first HIF Workshop in 1976 to the present. Chamber transport modes are categorized into ballistic transport modes and channel-like modes. Four major HIF reactor studies are summarized (HIBALL-II, HYLIFE-II, Prometheus-H, OSIRIS), with emphasis on the chamber transport environment. In general, many beams are used to provide the required symmetry and to permit focusing to the required small spots. Target parameters are then discussed, with a summary of the individual heavy ion beam parameters required for HIF. The beam parameters are then classified as to their line charge density and perveance, with special emphasis on the perveance limits for radial space charge spreading, for the space charge limiting current, and for the magnetic (Alfven) limiting current. The major experiments on ballistic transport (SFFE, Sabre beamlets, GAMBLE II, NTX, NDCX) are summarized, with specific reference to the axial electron trapping limit for charge neutralization. The major experiments on channel-like transport (GAMBLE II channel, GAMBLE II self-pinch, LBNL channels, GSI channels) are discussed. The status of current research on HIF chamber transport is summarized, and the value of future NDCX-II transport experiments for the future of HIF is noted.

Ion transport regulation by prostaglandins in mouse macrophages.

PubMed

Braquet, P; Diez, J; Garay, R

1985-01-01

Although the prostaglandins PGE1, PGE2 and PGF2 alpha had no effect on ion transport in isolated human erythrocytes, they modulated ion transport in isolated mouse macrophages, apparently through the mediation of cAMP, by inhibiting the NA+, K+ cotransport system, stimulating the Na+, K+ pump, and stimulating the Na+: Ca++ exchange mechanism.

Free Energy Wells and Barriers to Ion Transport Across Membranes

NASA Astrophysics Data System (ADS)

Rempe, Susan

2014-03-01

The flow of ions across cellular membranes is essential to many biological processes. Ion transport is also important in synthetic materials used as battery electrolytes. Transport often involves specific ions and fast conduction. To achieve those properties, ion conduction pathways must solvate specific ions by just the ``right amount.'' The right amount of solvation avoids ion traps due to deep free energy wells, and avoids ion block due to high free energy barriers. Ion channel proteins in cellular membranes demonstrate this subtle balance in solvation of specific ions. Using ab initio molecular simulations, we have interrogated the link between binding site structure and ion solvation free energies in biological ion binding sites. Our results emphasize the surprisingly important role of the environment that surrounds ion-binding sites for fast transport of specific ions. We acknowledge support from Sandia's LDRD program. Sandia National Labs is a multi-program laboratory operated by Sandia Corp., a wholly owned subsidiary of Lockheed Martin Corp., for the US DOE's NNSA under contract DE-AC04-94AL85000.

A model of ion transport processes along and across the neuronal membrane.

PubMed

Xiang, Z X; Liu, G Z; Tang, C X; Yan, L X

2017-01-01

In this study, we provide a foundational model of ion transport processes in the intracellular and extracellular compartments of neurons at the nanoscale. There are two different kinds of ionic transport processes: (i) ionic transport across the neuronal membrane (trans-membrane), and (ii) ionic transport along both the intracellular and extracellular surfaces of the membrane. Brownian dynamics simulations are used to give a description of ionic trans-membrane transport. Electro-diffusion is used to model ion transport along the membrane surface, and the two transport processes can be linked analytically. In our model, we found that the interactions between ions and ion channels result in high-frequency ionic oscillations during trans-membrane transport. In ion transport along the membrane, high-frequency ionic oscillations may be evoked on both the intracellular and extracellular surfaces of the plasma membrane. The electric field caused by Coulomb interactions between the ions is found to be the most likely origin of those ionic oscillations.

Trimodal Control of Ion-Transport Activity on Cyclo-oligo-(1→6)-β-D-glucosamine-Based Artificial Ion-Transport Systems.

PubMed

Roy, Arundhati; Saha, Tanmoy; Gening, Marina L; Titov, Denis V; Gerbst, Alexey G; Tsvetkov, Yury E; Nifantiev, Nikolay E; Talukdar, Pinaki

2015-11-23

Cyclo-oligo-(1→6)-β-D-glucosamines functionalized with hydrophobic tails are reported as a new class of transmembrane ion-transport system. These macrocycles with hydrophilic cavities were introduced as an alternative to cyclodextrins, which are supramolecular systems with hydrophobic cavities. The transport activities of these glycoconjugates were manipulated by altering the oligomericity of the macrocycles, as well as the length and number of attached tails. Hydrophobic tails of 3 different sizes were synthesized and coupled with each glucosamine scaffold through the amide linkage to obtain 18 derivatives. The ion-transport activity increased from di- to tetrameric glucosamine macrocycles, but decreased further when flexible pentameric glucosamine was introduced. The ion-transport activity also increased with increasing length of attached linkers. For a fixed length of linkers, the transport activity decreased when the number of such tails was reduced. All glycoconjugates displayed a uniform anion-selectivity sequence: Cl(-) >Br(-) >I(-) . From theoretical studies, hydrogen bonding between the macrocycle backbone and the anion bridged through water molecules was observed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Analysis of the theory of high energy ion transport

NASA Technical Reports Server (NTRS)

Wilson, J. W.

1977-01-01

Procedures for the approximation of the transport of high-energy ions are discussed on the basis of available data on ion nuclear reactions. A straightahead approximation appears appropriate for space applications. The assumption that the secondary-ion-fragment velocity is equal to that of the fragmenting nucleus is inferior to straightahead theory but is of sufficient accuracy if the primary ions display a broad energy spectrum. An iterative scheme for the solution of the inhomogenous integral transport equations holds promise for practical calculation. A model calculation shows that multiple charged ion fragments penetrate to greater depths in comparison with the free path of a primary heavy ion.

Asymmetric ion transport through ion-channel-mimetic solid-state nanopores.

PubMed

Guo, Wei; Tian, Ye; Jiang, Lei

2013-12-17

Both scientists and engineers are interested in the design and fabrication of synthetic nanofluidic architectures that mimic the gating functions of biological ion channels. The effort to build such structures requires interdisciplinary efforts at the intersection of chemistry, materials science, and nanotechnology. Biological ion channels and synthetic nanofluidic devices have some structural and chemical similarities, and therefore, they share some common features in regulating the traverse ionic flow. In the past decade, researchers have identified two asymmetric ion transport phenomena in synthetic nanofluidic structures, the rectified ionic current and the net diffusion current. The rectified ionic current is a diode-like current-voltage response that occurs when switching the voltage bias. This phenomenon indicates a preferential direction of transport in the nanofluidic system. The net diffusion current occurs as a direct product of charge selectivity and is generated from the asymmetric diffusion through charged nanofluidic channels. These new ion transport phenomena and the elaborate structures that occur in biology have inspired us to build functional nanofluidic devices for both fundamental research and practical applications. In this Account, we review our recent progress in the design and fabrication of biomimetic solid-state nanofluidic devices with asymmetric ion transport behavior. We demonstrate the origin of the rectified ionic current and the net diffusion current. We also identify several influential factors and discuss how to build these asymmetric features into nanofluidic systems by controlling (1) nanopore geometry, (2) surface charge distribution, (3) chemical composition, (4) channel wall wettability, (5) environmental pH, (6) electrolyte concentration gradient, and (7) ion mobility. In the case of the first four features, we build these asymmetric features directly into the nanofluidic structures. With the final three, we construct

Two-Dimensional Porous Carbon: Synthesis and Ion-Transport Properties.

PubMed

Zheng, Xiaoyu; Luo, Jiayan; Lv, Wei; Wang, Da-Wei; Yang, Quan-Hong

2015-09-23

Their chemical stability, high specific surface area, and electric conductivity enable porous carbon materials to be the most commonly used electrode materials for electrochemical capacitors (also known as supercapacitors). To further increase the energy and power density, engineering of the pore structures with a higher electrochemical accessible surface area, faster ion-transport path and a more-robust interface with the electrolyte is widely investigated. Compared with traditional porous carbons, two-dimensional (2D) porous carbon sheets with an interlinked hierarchical porous structure are a good candidate for supercapacitors due to their advantages in high aspect ratio for electrode packing and electron transport, hierarchical pore structures for ion transport, and short ion-transport length. Recent progress on the synthesis of 2D porous carbons is reported here, along with the improved electrochemical behavior due to enhanced ion transport. Challenges for the controlled preparation of 2D porous carbons with desired properties are also discussed; these require precise tuning of the hierarchical structure and a clarification of the formation mechanisms. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Using fluorometry and ion-sensitive microelectrodes to study the functional expression of heterologously-expressed ion channels and transporters in Xenopus oocytes

PubMed Central

Musa-Aziz, Raif; Boron, Walter F.; Parker, Mark D.

2010-01-01

The Xenopus laevis oocyte is a model system for the electrophysiological study of exogenous ion transporters. Three main reasons make the oocyte suitable for this purpose: (a) it has a large cell size (~1 mm diameter), (b) it has an established capacity to produce—from microinjected mRNAs or cRNAs—exogenous ion transporters with close-to-physiological post-translational modifications and actions, and (c) its membranes contain endogenous ion-transport activities which are usually smaller in magnitude than the activities of exogenously-expressed ion transporters. The expression of ion-transporters as green-fluorescent-protein fusions allows the fluorometric assay of transporter yield in living oocytes. Monitoring of transporter-mediated movement of ions such as Cl−, H+ (and hence base equivalents like OH−1 and HCO3−), K+, and Na+ is achieved by positioning the tips of ion-sensitive microelectrodes inside the oocyte and/or at the surface of the oocyte plasma membrane. The use of ion-sensitive electrodes is critical for studying net ion-movements mediated by electroneutral transporters. The combined use of fluorometry and electrophysiology expedites transporter study by allowing measurement of transporter yield prior to electrophysiological study and correlation of relative transporter yield with transport rates. PMID:20051266

Salinity tolerance in plants. Quantitative approach to ion transport starting from halophytes and stepping to genetic and protein engineering for manipulating ion fluxes.

PubMed

Volkov, Vadim

2015-01-01

Ion transport is the fundamental factor determining salinity tolerance in plants. The Review starts from differences in ion transport between salt tolerant halophytes and salt-sensitive plants with an emphasis on transport of potassium and sodium via plasma membranes. The comparison provides introductory information for increasing salinity tolerance. Effects of salt stress on ion transport properties of membranes show huge opportunities for manipulating ion fluxes. Further steps require knowledge about mechanisms of ion transport and individual genes of ion transport proteins. Initially, the Review describes methods to measure ion fluxes, the independent set of techniques ensures robust and reliable basement for quantitative approach. The Review briefly summarizes current data concerning Na(+) and K(+) concentrations in cells, refers to primary thermodynamics of ion transport and gives special attention to individual ion channels and transporters. Simplified scheme of a plant cell with known transport systems at the plasma membrane and tonoplast helps to imagine the complexity of ion transport and allows choosing specific transporters for modulating ion transport. The complexity is enhanced by the influence of cell size and cell wall on ion transport. Special attention is given to ion transporters and to potassium and sodium transport by HKT, HAK, NHX, and SOS1 proteins. Comparison between non-selective cation channels and ion transporters reveals potential importance of ion transporters and the balance between the two pathways of ion transport. Further on the Review describes in detail several successful attempts to overexpress or knockout ion transporters for changing salinity tolerance. Future perspectives are questioned with more attention given to promising candidate ion channels and transporters for altered expression. Potential direction of increasing salinity tolerance by modifying ion channels and transporters using single point mutations is discussed and

Salinity tolerance in plants. Quantitative approach to ion transport starting from halophytes and stepping to genetic and protein engineering for manipulating ion fluxes

PubMed Central

Volkov, Vadim

2015-01-01

Ion transport is the fundamental factor determining salinity tolerance in plants. The Review starts from differences in ion transport between salt tolerant halophytes and salt-sensitive plants with an emphasis on transport of potassium and sodium via plasma membranes. The comparison provides introductory information for increasing salinity tolerance. Effects of salt stress on ion transport properties of membranes show huge opportunities for manipulating ion fluxes. Further steps require knowledge about mechanisms of ion transport and individual genes of ion transport proteins. Initially, the Review describes methods to measure ion fluxes, the independent set of techniques ensures robust and reliable basement for quantitative approach. The Review briefly summarizes current data concerning Na+ and K+ concentrations in cells, refers to primary thermodynamics of ion transport and gives special attention to individual ion channels and transporters. Simplified scheme of a plant cell with known transport systems at the plasma membrane and tonoplast helps to imagine the complexity of ion transport and allows choosing specific transporters for modulating ion transport. The complexity is enhanced by the influence of cell size and cell wall on ion transport. Special attention is given to ion transporters and to potassium and sodium transport by HKT, HAK, NHX, and SOS1 proteins. Comparison between non-selective cation channels and ion transporters reveals potential importance of ion transporters and the balance between the two pathways of ion transport. Further on the Review describes in detail several successful attempts to overexpress or knockout ion transporters for changing salinity tolerance. Future perspectives are questioned with more attention given to promising candidate ion channels and transporters for altered expression. Potential direction of increasing salinity tolerance by modifying ion channels and transporters using single point mutations is discussed and

Hydrogen peroxide scavenger, catalase, alleviates ion transport dysfunction in murine colitis.

PubMed

Barrett, Kim E; McCole, Declan F

2016-11-01

Reactive oxygen species (ROS) such as hydrogen peroxide (H 2 O 2 ) contribute to epithelial damage and ion transport dysfunction (key events in inflammatory diarrhoea) in inflammatory bowel disease (IBD). The aim of this study was to identify if H 2 O 2 mediates suppression of colonic ion transport function in the murine dextran sulfate sodium (DSS) colitis model by using the H 2 O 2 degrading enzyme, catalase. Colitis was induced by administering DSS (4%) in drinking water for 5 days followed by 3 days on normal H 2 O. Mice were administered either pegylated catalase or saline at day -1, 0 and +1 of DSS treatment. Ion transport responses to the Ca 2+ -dependent agonist, carbachol (CCh), or the cAMP-dependent agonist, forskolin, were measured across distal colonic mucosa mounted in Ussing chambers. Parameters of DSS-induced inflammation (loss in body weight, decreased colon length, altered stool consistency), were only partially alleviated by catalase while histology was only minimally improved. However, catalase significantly reversed the DSS-induced reduction in baseline ion transport as well as colonic I sc responses to CCh. However, ion transport responses to forskolin were not significantly restored. Catalase also reduced activation of ERK MAP kinase in the setting of colitis, and increased expression of the Na + -K + -2Cl - cotransporter, NKCC1, consistent with restoration of ion transport function. Ex vivo treatment of inflamed colonic mucosae with catalase also partially restored ion transport function. Therefore, catalase partially prevents, and rescues, the loss of ion transport properties in DSS colitis even in the setting of unresolved tissue inflammation. These findings indicate a prominent role for ROS in ion transport dysfunction in colitis and may suggest novel strategies for the treatment of inflammatory diarrhoea. © 2016 John Wiley & Sons Australia, Ltd.

Ion transport membrane module and vessel system

DOEpatents

Stein, VanEric Edward; Carolan, Michael Francis; Chen, Christopher M.; Armstrong, Phillip Andrew; Wahle, Harold W.; Ohrn, Theodore R.; Kneidel, Kurt E.; Rackers, Keith Gerard; Blake, James Erik; Nataraj, Shankar; van Doorn, Rene Hendrik Elias; Wilson, Merrill Anderson

2007-02-20

An ion transport membrane system comprising (a) a pressure vessel having an interior, an exterior, an inlet, and an outlet; (b) a plurality of planar ion transport membrane modules disposed in the interior of the pressure vessel and arranged in series, each membrane module comprising mixed metal oxide ceramic material and having an interior region and an exterior region, wherein any inlet and any outlet of the pressure vessel are in flow communication with exterior regions of the membrane modules; and (c) one or more gas manifolds in flow communication with interior regions of the membrane modules and with the exterior of the pressure vessel. The ion transport membrane system may be utilized in a gas separation device to recover oxygen from an oxygen-containing gas or as an oxidation reactor to oxidize compounds in a feed gas stream by oxygen permeated through the mixed metal oxide ceramic material of the membrane modules.

Ion transport membrane module and vessel system

DOEpatents

Stein, VanEric Edward [Allentown, PA; Carolan, Michael Francis [Allentown, PA; Chen, Christopher M [Allentown, PA; Armstrong, Phillip Andrew [Orefield, PA; Wahle, Harold W [North Canton, OH; Ohrn, Theodore R [Alliance, OH; Kneidel, Kurt E [Alliance, OH; Rackers, Keith Gerard [Louisville, OH; Blake, James Erik [Uniontown, OH; Nataraj, Shankar [Allentown, PA; Van Doorn, Rene Hendrik Elias; Wilson, Merrill Anderson [West Jordan, UT

2012-02-14

An ion transport membrane system comprising (a) a pressure vessel having an interior, an exterior, an inlet, and an outlet; (b) a plurality of planar ion transport membrane modules disposed in the interior of the pressure vessel and arranged in series, each membrane module comprising mixed metal oxide ceramic material and having an interior region and an exterior region, wherein any inlet and any outlet of the pressure vessel are in flow communication with exterior regions of the membrane modules; and (c) one or more gas manifolds in flow communication with interior regions of the membrane modules and with the exterior of the pressure vessel. The ion transport membrane system may be utilized in a gas separation device to recover oxygen from an oxygen-containing gas or as an oxidation reactor to oxidize compounds in a feed gas stream by oxygen permeated through the mixed metal oxide ceramic material of the membrane modules.

Ion transport membrane module and vessel system

DOEpatents

Stein, VanEric Edward [Allentown, PA; Carolan, Michael Francis [Allentown, PA; Chen, Christopher M [Allentown, PA; Armstrong, Phillip Andrew [Orefield, PA; Wahle, Harold W [North Canton, OH; Ohrn, Theodore R [Alliance, OH; Kneidel, Kurt E [Alliance, OH; Rackers, Keith Gerard [Louisville, OH; Blake, James Erik [Uniontown, OH; Nataraj, Shankar [Allentown, PA; van Doorn, Rene Hendrik Elias; Wilson, Merrill Anderson [West Jordan, UT

2008-02-26

An ion transport membrane system comprising (a) a pressure vessel having an interior, an exterior, an inlet, and an outlet; (b) a plurality of planar ion transport membrane modules disposed in the interior of the pressure vessel and arranged in series, each membrane module comprising mixed metal oxide ceramic material and having an interior region and an exterior region, wherein any inlet and any outlet of the pressure vessel are in flow communication with exterior regions of the membrane modules; and (c) one or more gas manifolds in flow communication with interior regions of the membrane modules and with the exterior of the pressure vessel.The ion transport membrane system may be utilized in a gas separation device to recover oxygen from an oxygen-containing gas or as an oxidation reactor to oxidize compounds in a feed gas stream by oxygen permeated through the mixed metal oxide ceramic material of the membrane modules.

Multi-species ion transport in ICF relevant conditions

NASA Astrophysics Data System (ADS)

Vold, Erik; Kagan, Grigory; Simakov, Andrei; Molvig, Kim; Yin, Lin; Albright, Brian

2017-10-01

Classical transport theory based on Chapman-Enskog methods provides self consistent approximations for kinetic fluxes of mass, heat and momentum for each ion species in a multi-ion plasma characterized with a small Knudsen number. A numerical method for solving the classic forms of multi-ion transport, self-consistently including heat and species mass fluxes relative to the center of mass, is given in [Kagan-Baalrud, arXiv '16] and similar transport coefficients result from recent derivations [Simakov-Molvig, PoP, '16]. We have implemented a combination of these methods in a standalone test code and in xRage, an adaptive-mesh radiation hydrodynamics code, at LANL. Transport mixing is examined between a DT fuel and a CH capsule shell in ICF conditions. The four ion species develop individual self-similar density profiles under the assumption of P-T equilibrium in 1D and show interesting early time transient pressure and center of mass velocity behavior when P-T equilibrium is not enforced. Some 2D results are explored to better understand the transport mix in combination with convective flow driven by macroscopic fluid instabilities at the fuel-capsule interface. Early transient and some 2D behaviors from the fluid transport are compared to kinetic code results. Work performed under the auspices of the U.S. DOE by the LANS, LLC, Los Alamos National Laboratory under Contract No. DE-AC52-06NA25396. Funding provided by the Advanced Simulation and Computing (ASC) Program.

The importance of dehydration in determining ion transport in narrow pores.

PubMed

Richards, Laura A; Schäfer, Andrea I; Richards, Bryce S; Corry, Ben

2012-06-11

The transport of hydrated ions through narrow pores is important for a number of processes such as the desalination and filtration of water and the conductance of ions through biological channels. Here, molecular dynamics simulations are used to systematically examine the transport of anionic drinking water contaminants (fluoride, chloride, nitrate, and nitrite) through pores ranging in effective radius from 2.8 to 6.5 Å to elucidate the role of hydration in excluding these species during nanofiltration. Bulk hydration properties (hydrated size and coordination number) are determined for comparison with the situations inside the pores. Free energy profiles for ion transport through the pores show energy barriers depend on pore size, ion type, and membrane surface charge and that the selectivity sequence can change depending on the pore size. Ion coordination numbers along the trajectory showed that partial dehydration of the transported ion is the main contribution to the energy barriers. Ion transport is greatly hindered when the effective pore radius is smaller than the hydrated radius, as the ion has to lose some associated water molecules to enter the pore. Small energy barriers are still observed when pore sizes are larger than the hydrated radius due to re-orientation of the hydration shell or the loss of more distant water. These results demonstrate the importance of ion dehydration in transport through narrow pores, which increases the current level of mechanistic understanding of membrane-based desalination and transport in biological channels. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Human Airway Epithelial Basal Cell Transcriptome

PubMed Central

Wang, Rui; Zwick, Rachel K.; Ferris, Barbara; Witover, Bradley; Salit, Jacqueline; Crystal, Ronald G.

2011-01-01

Background The human airway epithelium consists of 4 major cell types: ciliated, secretory, columnar and basal cells. During natural turnover and in response to injury, the airway basal cells function as stem/progenitor cells for the other airway cell types. The objective of this study is to better understand human airway epithelial basal cell biology by defining the gene expression signature of this cell population. Methodology/Principal Findings Bronchial brushing was used to obtain airway epithelium from healthy nonsmokers. Microarrays were used to assess the transcriptome of basal cells purified from the airway epithelium in comparison to the transcriptome of the differentiated airway epithelium. This analysis identified the “human airway basal cell signature” as 1,161 unique genes with >5-fold higher expression level in basal cells compared to differentiated epithelium. The basal cell signature was suppressed when the basal cells differentiated into a ciliated airway epithelium in vitro. The basal cell signature displayed overlap with genes expressed in basal-like cells from other human tissues and with that of murine airway basal cells. Consistent with self-modulation as well as signaling to other airway cell types, the human airway basal cell signature was characterized by genes encoding extracellular matrix components, growth factors and growth factor receptors, including genes related to the EGF and VEGF pathways. Interestingly, while the basal cell signature overlaps that of basal-like cells of other organs, the human airway basal cell signature has features not previously associated with this cell type, including a unique pattern of genes encoding extracellular matrix components, G protein-coupled receptors, neuroactive ligands and receptors, and ion channels. Conclusion/Significance The human airway epithelial basal cell signature identified in the present study provides novel insights into the molecular phenotype and biology of the stem

Composite oxygen ion transport element

DOEpatents

Chen, Jack C [Getzville, NY; Besecker, Charles J [Batavia, IL; Chen, Hancun [Williamsville, NY; Robinson, Earil T [Mentor, OH

2007-06-12

A composite oxygen ion transport element that has a layered structure formed by a dense layer to transport oxygen ions and electrons and a porous support layer to provide mechanical support. The dense layer can be formed of a mixture of a mixed conductor, an ionic conductor, and a metal. The porous support layer can be fabricated from an oxide dispersion strengthened metal, a metal-reinforced intermetallic alloy, a boron-doped Mo.sub.5Si.sub.3-based intermetallic alloy or combinations thereof. The support layer can be provided with a network of non-interconnected pores and each of said pores communicates between opposite surfaces of said support layer. Such a support layer can be advantageously employed to reduce diffusion resistance in any type of element, including those using a different material makeup than that outlined above.

Bio-inspired smart single asymmetric hourglass nanochannels for continuous shape and ion transport control.

PubMed

Zhang, Huacheng; Hou, Xu; Yang, Zhe; Yan, Dadong; Li, Lin; Tian, Ye; Wang, Huanting; Jiang, Lei

2015-02-18

Inspired by biological asymmetric ion channels, new shape-tunable and pH-responsive asymmetric hourglass single nanochannel systems demonstrate unique ion-transport properties. It is found that the change in shape and pH cooperatively control the ion transport within the nanochannel ranging from asymmetric shape with asymmetric ion transport, to asymmetric shape with symmetric ion transport and symmetric shape with symmetric ion transport. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Functional activity of L-carnitine transporters in human airway epithelial cells.

PubMed

Ingoglia, Filippo; Visigalli, Rossana; Rotoli, Bianca Maria; Barilli, Amelia; Riccardi, Benedetta; Puccini, Paola; Dall'Asta, Valeria

2016-02-01

Carnitine plays a physiologically important role in the β-oxidation of fatty acids, facilitating the transport of long-chain fatty acids across the inner mitochondrial membrane. Distribution of carnitine within the body tissues is mainly performed by novel organic cation transporter (OCTN) family, including the isoforms OCTN1 (SLC22A4) and OCTN2 (SLC22A5) expressed in human. We performed here a characterization of carnitine transport in human airway epithelial cells A549, Calu-3, NCl-H441, and BEAS-2B, by means of an integrated approach combining data of mRNA/protein expression with the kinetic and inhibition analyses of L-[(3)H]carnitine transport. Carnitine uptake was strictly Na(+)-dependent in all cell models. In A549 and BEAS-2B cells, carnitine uptake was mediated by one high-affinity component (Km<2 μM) identifiable with OCTN2. In both these cell models, indeed, carnitine uptake was maximally inhibited by betaine and strongly reduced by SLC22A5/OCTN2 silencing. Conversely, Calu-3 and NCl-H441 exhibited both a high (Km~20 μM) and a low affinity (Km>1 mM) transport component. While the high affinity component is identifiable with OCTN2, the low affinity uptake is mediated by ATB(0,+), a Na(+), and Cl(-)-coupled transport system for neutral and cationic amino acids, as demonstrated by the inhibition by leucine and arginine, as well as by SLC6A14/ATB(0,+) silencing. The presence of this transporter leads to a massive accumulation of carnitine inside the cells and may be of peculiar relevance in pathologic conditions of carnitine deficiency, such as those associated to OCTN2 defects. Copyright © 2015 Elsevier B.V. All rights reserved.

Increased apical Na+ permeability in cystic fibrosis is supported by a quantitative model of epithelial ion transport

PubMed Central

O’Donoghue, Donal L; Dua, Vivek; Moss, Guy W J; Vergani, Paola

2013-01-01

Cystic fibrosis (CF) is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, which encodes an anion channel. In the human lung CFTR loss causes abnormal ion transport across airway epithelial cells. As a result CF individuals produce thick mucus, suffer persistent bacterial infections and have a much reduced life expectancy. Trans-epithelial potential difference (Vt) measurements are routinely carried out on nasal epithelia of CF patients in the clinic. CF epithelia exhibit a hyperpolarised basal Vt and a larger Vt change in response to amiloride (a blocker of the epithelial Na+ channel, ENaC). Are these altered bioelectric properties solely a result of electrical coupling between the ENaC and CFTR currents, or are they due to an increased ENaC permeability associated with CFTR loss? To examine these issues we have developed a quantitative mathematical model of human nasal epithelial ion transport. We find that while the loss of CFTR permeability hyperpolarises Vt and also increases amiloride-sensitive Vt, these effects are too small to account for the magnitude of change observed in CF epithelia. Instead, a parallel increase in ENaC permeability is required to adequately fit observed experimental data. Our study provides quantitative predictions for the complex relationships between ionic permeabilities and nasal Vt, giving insights into the physiology of CF disease that have important implications for CF therapy. PMID:23732645

Imaging ion and molecular transport at subcellular resolution by secondary ion mass spectrometry

NASA Astrophysics Data System (ADS)

Chandra, Subhash; Morrison, George H.

1995-05-01

The transport of K+, Na+, and Ca2+ were imaged in individual cells with a Cameca IMS-3f ion microscope. Strict cryogenic frozen freeze-dry sample preparations were employed. Ion redistribution artifacts in conventional chemical preparations are discussed. Cryogenically prepared freeze-fractured freeze-dried cultured cells allowed the three-dimensional ion microscopic imaging of elements. As smaller structures in calcium images can be resolved with the 0.5 [mu]m spatial resolution, correlative techniques are needed to confirm their identity. The potentials of reflected light microscopy, scanning electron microscopy and laser scanning confocal microscopy are discussed for microfeature recognition in freeze-fractured freeze-dried cells. The feasibility of using frozen freeze-dried cells for imaging molecular transport at subcellular resolution was tested. Ion microscopy successfully imaged the transport of the isotopically tagged (13C, 15N) amino acid, -arginine. The labeled amino acid was imaged at mass 28 with a Cs+ primary ion beam as the 28(13C15N)- species. After a 4 h exposure of LLC-PK1 kidney cells to 4 mM labeled arginine, the amino acid was localized throughout the cell with a preferential incorporation into the nucleus and nucleolus. An example is also shown of the ion microscopic imaging of sodium borocaptate, an experimental therapeutic drug for brain tumors, in cryogenically prepared frozen freeze-dried Swiss 3T3 cells.

Mitochondrial Ion Channels/Transporters as Sensors and Regulators of Cellular Redox Signaling

PubMed Central

Ryu, Shin-Young; Jhun, Bong Sook; Hurst, Stephen

2014-01-01

Abstract Significance: Mitochondrial ion channels/transporters and the electron transport chain (ETC) serve as key sensors and regulators for cellular redox signaling, the production of reactive oxygen species (ROS) and nitrogen species (RNS) in mitochondria, and balancing cell survival and death. Although the functional and pharmacological characteristics of mitochondrial ion transport mechanisms have been extensively studied for several decades, the majority of the molecular identities that are responsible for these channels/transporters have remained a mystery until very recently. Recent Advances: Recent breakthrough studies uncovered the molecular identities of the diverse array of major mitochondrial ion channels/transporters, including the mitochondrial Ca2+ uniporter pore, mitochondrial permeability transition pore, and mitochondrial ATP-sensitive K+ channel. This new information enables us to form detailed molecular and functional characterizations of mitochondrial ion channels/transporters and their roles in mitochondrial redox signaling. Critical Issues: Redox-mediated post-translational modifications of mitochondrial ion channels/transporters and ETC serve as key mechanisms for the spatiotemporal control of mitochondrial ROS/RNS generation. Future Directions: Identification of detailed molecular mechanisms for redox-mediated regulation of mitochondrial ion channels will enable us to find novel therapeutic targets for many diseases that are associated with cellular redox signaling and mitochondrial ion channels/transporters. Antioxid. Redox Signal. 21, 987–1006. PMID:24180309

Differentiation of human bronchial epithelial cells: role of hydrocortisone in development of ion transport pathways involved in mucociliary clearance.

PubMed

Zaidman, Nathan A; Panoskaltsis-Mortari, Angela; O'Grady, Scott M

2016-08-01

Glucocorticoids strongly influence the mucosal-defense functions performed by the bronchial epithelium, and inhaled corticosteroids are critical in the treatment of patients with inflammatory airway diseases such as asthma, chronic obstructive pulmonary disease, and cystic fibrosis. A common pathology associated with these diseases is reduced mucociliary clearance, a defense mechanism involving the coordinated transport of salt, water, and mucus by the bronchial epithelium, ultimately leading to retention of pathogens and particles in the airways and to further disease progression. In the present study we investigated the role of hydrocortisone (HC) in differentiation and development of the ion transport phenotype of normal human bronchial epithelial cells under air-liquid interface conditions. Normal human bronchial epithelial cells differentiated in the absence of HC (HC0) showed significantly less benzamil-sensitive short-circuit current than controls, as well as a reduced response after stimulation with the selective β2-adrenergic receptor agonist salbutamol. Apical membrane localization of epithelial Na(+) channel α-subunits was similarly reduced in HC0 cells compared with controls, supporting a role of HC in the trafficking and density of Na(+) channels in the plasma membrane. Additionally, glucocorticoid exposure during differentiation regulated the transcription of cystic fibrosis transmembrane conductance regulator and β2-adrenergic receptor mRNAs and appeared to be necessary for the expression of cystic fibrosis transmembrane conductance regulator-dependent anion secretion in response to β2-agonists. HC had no significant effect on surface cell differentiation but did modulate the expression of mucin mRNAs. These findings indicate that glucocorticoids support mucosal defense by regulating critical transport pathways essential for effective mucociliary clearance. Copyright © 2016 the American Physiological Society.

Single-ion, transportable optical atomic clocks

NASA Astrophysics Data System (ADS)

Delehaye, Marion; Lacroûte, Clément

2018-03-01

For the past 15 years, tremendous progress within the fields of laser stabilization, optical frequency combs and atom cooling and trapping have allowed the realization of optical atomic clocks with unrivaled performances. These instruments can perform frequency comparisons with fractional uncertainties well below ?, finding applications in fundamental physics tests, relativistic geodesy and time and frequency metrology. Even though most optical clocks are currently laboratory setups, several proposals for using these clocks for field measurements or within an optical clock network have been published, and most of time and frequency metrology institutes have started to develop transportable optical clocks. For the purpose of this special issue, we chose to focus on trapped-ion optical clocks. Even though their short-term fractional frequency stability is impaired by a lower signal-to-noise ratio, they offer a high potential for compactness: trapped ions demand low optical powers and simple loading schemes, and can be trapped in small vacuum chambers. We review recent advances on the clock key components, including ion trap and ultra-stable optical cavity, as well as existing projects and experiments which draw the picture of what future transportable, single-ion optical clocks may resemble.

Development of an airway mucus defect in the cystic fibrosis rat

PubMed Central

Birket, Susan E.; Davis, Joy M.; Fernandez, Courtney M.; Tuggle, Katherine L.; Oden, Ashley M.; Chu, Kengyeh K.; Tearney, Guillermo J.; Fanucchi, Michelle V.; Sorscher, Eric J.

2018-01-01

The mechanisms underlying the development and natural progression of the airway mucus defect in cystic fibrosis (CF) remain largely unclear. New animal models of CF, coupled with imaging using micro-optical coherence tomography, can lead to insights regarding these questions. The Cftr–/– (KO) rat allows for longitudinal examination of the development and progression of airway mucus abnormalities. The KO rat exhibits decreased periciliary depth, hyperacidic pH, and increased mucus solid content percentage; however, the transport rates and viscoelastic properties of the mucus are unaffected until the KO rat ages. Airway submucosal gland hypertrophy develops in the KO rat by 6 months of age. Only then does it induce increased mucus viscosity, collapse of the periciliary layer, and delayed mucociliary transport; stimulation of gland secretion potentiates this evolution. These findings could be reversed by bicarbonate repletion but not pH correction without counterion donation. These studies demonstrate that abnormal surface epithelium in CF does not cause delayed mucus transport in the absence of functional gland secretions. Furthermore, abnormal bicarbonate transport represents a specific target for restoring mucus clearance, independent of effects on periciliary collapse. Thus, mature airway secretions are required to manifest the CF defect primed by airway dehydration and bicarbonate deficiency. PMID:29321377

Brownian Dynamics Simulations of Ion Transport through the VDAC

PubMed Central

Lee, Kyu Il; Rui, Huan; Pastor, Richard W.; Im, Wonpil

2011-01-01

It is important to gain a physical understanding of ion transport through the voltage-dependent anion channel (VDAC) because this channel provides primary permeation pathways for metabolites and electrolytes between the cytosol and mitochondria. We performed grand canonical Monte Carlo/Brownian dynamics (GCMC/BD) simulations to explore the ion transport properties of human VDAC isoform 1 (hVDAC1; PDB:2K4T) embedded in an implicit membrane. When the MD-derived, space-dependent diffusion constant was used in the GCMC/BD simulations, the current-voltage characteristics and ion number profiles inside the pore showed excellent agreement with those calculated from all-atom molecular-dynamics (MD) simulations, thereby validating the GCMC/BD approach. Of the 20 NMR models of hVDAC1 currently available, the third one (NMR03) best reproduces both experimental single-channel conductance and ion selectivity (i.e., the reversal potential). In addition, detailed analyses of the ion trajectories, one-dimensional multi-ion potential of mean force, and protein charge distribution reveal that electrostatic interactions play an important role in the channel structure and ion transport relationship. Finally, the GCMC/BD simulations of various mutants based on NMR03 show good agreement with experimental ion selectivity. The difference in ion selectivity between the wild-type and the mutants is the result of altered potential of mean force profiles that are dominated by the electrostatic interactions. PMID:21281575

Roles of ion transport in control of cell motility.

PubMed

Stock, Christian; Ludwig, Florian T; Hanley, Peter J; Schwab, Albrecht

2013-01-01

Cell motility is an essential feature of life. It is essential for reproduction, propagation, embryonic development, and healing processes such as wound closure and a successful immune defense. If out of control, cell motility can become life-threatening as, for example, in metastasis or autoimmune diseases. Regardless of whether ciliary/flagellar or amoeboid movement, controlled motility always requires a concerted action of ion channels and transporters, cytoskeletal elements, and signaling cascades. Ion transport across the plasma membrane contributes to cell motility by affecting the membrane potential and voltage-sensitive ion channels, by inducing local volume changes with the help of aquaporins and by modulating cytosolic Ca(2+) and H(+) concentrations. Voltage-sensitive ion channels serve as voltage detectors in electric fields thus enabling galvanotaxis; local swelling facilitates the outgrowth of protrusions at the leading edge while local shrinkage accompanies the retraction of the cell rear; the cytosolic Ca(2+) concentration exerts its main effect on cytoskeletal dynamics via motor proteins such as myosin or dynein; and both, the intracellular and the extracellular H(+) concentration modulate cell migration and adhesion by tuning the activity of enzymes and signaling molecules in the cytosol as well as the activation state of adhesion molecules at the cell surface. In addition to the actual process of ion transport, both, channels and transporters contribute to cell migration by being part of focal adhesion complexes and/or physically interacting with components of the cytoskeleton. The present article provides an overview of how the numerous ion-transport mechanisms contribute to the various modes of cell motility.

Difficult airway response team: a novel quality improvement program for managing hospital-wide airway emergencies.

PubMed

Mark, Lynette J; Herzer, Kurt R; Cover, Renee; Pandian, Vinciya; Bhatti, Nasir I; Berkow, Lauren C; Haut, Elliott R; Hillel, Alexander T; Miller, Christina R; Feller-Kopman, David J; Schiavi, Adam J; Xie, Yanjun J; Lim, Christine; Holzmueller, Christine; Ahmad, Mueen; Thomas, Pradeep; Flint, Paul W; Mirski, Marek A

2015-07-01

-three patients (6%) required emergent surgical airways. Sixty-two patients (17%) were stabilized and transported to the operating room for definitive airway management. There were no airway management-related deaths, sentinel events, or malpractice claims in adult patients managed by DART. Five in situ simulations conducted in the first program year improved DART's teamwork, communication, and response times and increased the functionality of the difficult airway carts. Over the 5-year period, we conducted 18 airway courses, through which >200 providers were trained. DART is a comprehensive program for improving difficult airway management. Future studies will examine the comparative effectiveness of the DART program and evaluate how DART has impacted patient outcomes, operational efficiency, and costs of care.

Difficult Airway Response Team: A Novel Quality Improvement Program for Managing Hospital-Wide Airway Emergencies

PubMed Central

Mark, Lynette J.; Herzer, Kurt R.; Cover, Renee; Pandian, Vinciya; Bhatti, Nasir I.; Berkow, Lauren C.; Haut, Elliott R.; Hillel, Alexander T.; Miller, Christina R.; Feller-Kopman, David J.; Schiavi, Adam J.; Xie, Yanjun J.; Lim, Christine; Holzmueller, Christine; Ahmad, Mueen; Thomas, Pradeep; Flint, Paul W.; Mirski, Marek A.

2015-01-01

or current tracheostomy. Twenty-three patients (6%) required emergent surgical airways. Sixty-two patients (17%) were stabilized and transported to the operating room for definitive airway management. There were no airway management-related deaths, sentinel events, or malpractice claims in adult patients managed by DART. Five in situ simulations conducted in the first program year improved DART's teamwork, communication, and response times and increased the functionality of the difficult airway carts. Over the 5-year period, we conducted 18 airway courses, through which more than 200 providers were trained. Conclusions DART is a comprehensive program for improving difficult airway management. Future studies will examine the comparative effectiveness of the DART program and evaluate how DART has impacted patient outcomes, operational efficiency, and costs of care. PMID:26086513

Lateral charge transport from heavy-ion tracks in integrated circuit chips

NASA Technical Reports Server (NTRS)

Zoutendyk, J. A.; Schwartz, H. R.; Nevill, L. R.

1988-01-01

A 256K DRAM has been used to study the lateral transport of charge (electron-hole pairs) induced by direct ionization from heavy-ion tracks in an IC. The qualitative charge transport has been simulated using a two-dimensional numerical code in cylindrical coordinates. The experimental bit-map data clearly show the manifestation of lateral charge transport in the creation of adjacent multiple-bit errors from a single heavy-ion track. The heavy-ion data further demonstrate the occurrence of multiple-bit errors from single ion tracks with sufficient stopping power. The qualitative numerical simulation results suggest that electric-field-funnel-aided (drift) collection accounts for single error generated by an ion passing through a charge-collecting junction, while multiple errors from a single ion track are due to lateral diffusion of ion-generated charge.

Cellular distribution and function of ion channels involved in transport processes in rat tracheal epithelium.

PubMed

Hahn, Anne; Faulhaber, Johannes; Srisawang, Lalita; Stortz, Andreas; Salomon, Johanna J; Mall, Marcus A; Frings, Stephan; Möhrlen, Frank

2017-06-01

Transport of water and electrolytes in airway epithelia involves chloride-selective ion channels, which are controlled either by cytosolic Ca 2+ or by cAMP The contributions of the two pathways to chloride transport differ among vertebrate species. Because rats are becoming more important as animal model for cystic fibrosis, we have examined how Ca 2+ - dependent and cAMP- dependent Cl - secretion is organized in the rat tracheal epithelium. We examined the expression of the Ca 2+ -gated Cl - channel anoctamin 1 (ANO1), the cystic fibrosis transmembrane conductance regulator (CFTR) Cl - channel, the epithelial Na + channel ENaC, and the water channel aquaporin 5 (AQP5) in rat tracheal epithelium. The contribution of ANO1 channels to nucleotide-stimulated Cl - secretion was determined using the channel blocker Ani9 in short-circuit current recordings obtained from primary cultures of rat tracheal epithelial cells in Ussing chambers. We found that ANO1, CFTR and AQP5 proteins were expressed in nonciliated cells of the tracheal epithelium, whereas ENaC was expressed in ciliated cells. Among nonciliated cells, ANO1 occurred together with CFTR and Muc5b and, in addition, in a different cell type without CFTR and Muc5b. Bioelectrical studies with the ANO1-blocker Ani9 indicated that ANO1 mediated the secretory response to the nucleotide uridine-5'-triphosphate. Our data demonstrate that, in rat tracheal epithelium, Cl - secretion and Na + absorption are routed through different cell types, and that ANO1 channels form the molecular basis of Ca 2+ -dependent Cl - secretion in this tissue. These characteristic features of Cl - -dependent secretion reveal similarities and distinct differences to secretory processes in human airways. © 2017 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.

Cyclic Adenosine Monophosphate Regulation of Ion Transport in Porcine Vocal Fold Mucosae

PubMed Central

Sivasankar, Mahalakshmi; Nofziger, Charity; Blazer-Yost, Bonnie

2012-01-01

Objectives/Hypothesis Cyclic adenosine monophosphate (cAMP) is an important biological molecule that regulates ion transport and inflammatory responses in epithelial tissue. The present study examined whether the adenylyl cyclase activator, forskolin, would increase cAMP concentration in porcine vocal fold mucosa and whether the effects of increased cAMP would be manifested as a functional increase in transepithelial ion transport. Additionally, changes in cAMP concentrations following exposure to an inflammatory mediator, tumor necrosis factor-α (TNFα) were investigated. Study Design In vitro experimental design with matched treatment and control groups. Methods Porcine vocal fold mucosae (N = 30) and tracheal mucosae (N = 20) were exposed to forskolin, TNFα, or vehicle (dimethyl sulfoxide) treatment. cAMP concentrations were determined with enzyme-linked immunosorbent assay. Ion transport was measured using electrophysiological techniques. Results Thirty minute exposure to forskolin significantly increased cAMP concentration and ion transport in porcine vocal fold and tracheal mucosae. However, 30-minute and 2-hour exposure to TNFα did not significantly alter cAMP concentration. Conclusions We demonstrate that forskolin-sensitive adenylyl cyclase is present in vocal fold mucosa, and further, that the product, cAMP increases vocal fold ion transport. The results presented here contribute to our understanding of the intracellular mechanisms underlying vocal fold ion transport. As ion transport is important for maintaining superficial vocal fold hydration, data demonstrating forskolin-stimulated ion transport in vocal fold mucosa suggest opportunities for developing pharmacological treatments that increase surface hydration. PMID:18596479

Multivalent Ion Transport in Polymers via Metal-Ligand Coordination

NASA Astrophysics Data System (ADS)

Sanoja, Gabriel; Schauser, Nicole; Evans, Christopher; Majumdar, Shubhaditya; Segalman, Rachel

Elucidating design rules for multivalent ion conducting polymers is critical for developing novel high-performance materials for electrochemical devices. Herein, we molecularly engineer multivalent ion conducting polymers based on metal-ligand interactions and illustrate that both segmental dynamics and ion coordination kinetics are essential for ion transport through polymers. We present a novel statistical copolymer, poly(ethylene oxide-stat-imidazole glycidyl ether) (i.e., PEO-stat-PIGE), that synergistically combines the structural hierarchy of PEO with the Lewis basicity of tethered imidazole ligands (xIGE = 0.17) required to coordinate a series of transition metal salts containing bis(trifluoromethylsulfonyl)imide anions. Complexes of PEO-stat-PIGE with salts exhibit a nanostructure in which ion-enriched regions alternate with ion-deficient regions, and an ionic conductivity above 10-5 S/cm. Novel normalization schemes that account for ion solvation kinetics are presented to attain a universal scaling relationship for multivalent ion transport in polymers via metal-ligand coordination. AFOSR MURI program under FA9550-12-1.

A New Poisson-Nernst-Planck Model with Ion-Water Interactions for Charge Transport in Ion Channels.

PubMed

Chen, Duan

2016-08-01

In this work, we propose a new Poisson-Nernst-Planck (PNP) model with ion-water interactions for biological charge transport in ion channels. Due to narrow geometries of these membrane proteins, ion-water interaction is critical for both dielectric property of water molecules in channel pore and transport dynamics of mobile ions. We model the ion-water interaction energy based on realistic experimental observations in an efficient mean-field approach. Variation of a total energy functional of the biological system yields a new PNP-type continuum model. Numerical simulations show that the proposed model with ion-water interaction energy has the new features that quantitatively describe dielectric properties of water molecules in narrow pores and are possible to model the selectivity of some ion channels.

The Hydrogen Peroxide Scavenger, Catalase, Alleviates Ion Transport Dysfunction in Murine Colitis

PubMed Central

Barrett, Kim E.; McCole, Declan F.

2016-01-01

Reactive oxygen species (ROS) such as hydrogen peroxide (H2O2) contribute to epithelial damage and ion transport dysfunction (key events in inflammatory diarrhea) in inflammatory bowel disease (IBD). The aim of this study was to identify if H2O2 mediates suppression of colonic ion transport function in the murine dextran sulfate sodium (DSS) colitis model by using the H2O2 degrading enzyme, catalase. Colitis was induced by administering DSS (4%) in drinking water for 5 days followed by 3 days on normal H2O. Mice were administered either pegylated-catalase or saline at day −1, 0 and +1 of DSS treatment. Ion transport responses to the Ca2+-dependent agonist, carbachol (CCh), or the cAMP-dependent agonist, forskolin, were measured across distal colonic mucosa mounted in Ussing chambers. Parameters of DSS-induced inflammation (loss in body weight, decreased colon length, altered stool consistency), were only partially alleviated by catalase while histology was only minimally improved. However, catalase significantly reversed the DSS-induced reduction in baseline ion transport as well as colonic Isc responses to CCh. However, ion transport responses to forskolin were not significantly restored. Catalase also reduced activation of ERK MAP kinase in the setting of colitis, and increased expression of the Na+-K+-2Cl− cotransporter, NKCC1, consistent with restoration of ion transport function. Ex vivo treatment of inflamed colonic mucosae with catalase also partially restored ion transport function. Therefore, catalase partially prevents, and rescues, the loss of ion transport properties in DSS colitis even in the setting of unresolved tissue inflammation. These findings indicate a prominent role for ROS in ion transport dysfunction in colitis and may suggest novel strategies for the treatment of inflammatory diarrhea. PMID:27543846

Transport of Zn(OH)4(-2) ions across a polyolefin microporous membrane

NASA Astrophysics Data System (ADS)

Krejci, Ivan; Vanysek, Peter; Trojanek, Antonin

1993-04-01

Transport of ZN(OH)4(2-) ions through modified microporous polypropylene membranes (Celgard 3401, 350140) was studied using polarography and conductometry. Soluble Nafion as an ion exchange modifying agent was applied to the membrane by several techniques. The influence of Nafion and a surfactant on transport of zinc ions through the membrane was studied. A relationship between membrane impedance and the rate of Zn(OH)4(2-) transport was found. The found correlation between conductivity, ion permeability and Nafion coverage suggests a suitable technique of membrane preparation to obtain desired zinc ion barrier properties.

Computer Simulations of Ion Transport in Polymer Electrolyte Membranes.

PubMed

Mogurampelly, Santosh; Borodin, Oleg; Ganesan, Venkat

2016-06-07

Understanding the mechanisms and optimizing ion transport in polymer membranes have been the subject of active research for more than three decades. We present an overview of the progress and challenges involved with the modeling and simulation aspects of the ion transport properties of polymer membranes. We are concerned mainly with atomistic and coarser level simulation studies and discuss some salient work in the context of pure binary and single ion conducting polymer electrolytes, polymer nanocomposites, block copolymers, and ionic liquid-based hybrid electrolytes. We conclude with an outlook highlighting future directions.

Metachronal waves in epithelium cilia to transport bronchial mucus in airways

NASA Astrophysics Data System (ADS)

Favier, Julien; Sylvain, Chateau; D'Ortona, Umberto; Poncet, Sébastien

2017-11-01

Metachronal waves of beating cilia are an efficient mechanism to transport mucus in human airways. The numerical results we will present will shed new light on the understanding of chronic respiratory diseases, such as Asthma of COPD. A coupled lattice Boltzmann - Immersed Boundary is used to simulate the multiphase environment in which the cilia are immersed: a periciliary layer and the mucus layer. A purely hydrodynamical feedback of the fluids is taken into account, and a coupling parameter α is introduced, allowing the tuning of both the direction of the wave propagation, and the strength of the fluid feedback. The cilia, initially set in a random state, quickly synchronize with their immediate neighbors giving birth to metachronal waves. A comparative study of both antipleptic and sympleptic waves is performed by imposing the metachrony. Antiplectic waves are found to be the most efficient to transport and mix fluids compared to other random or synchronised cilia motions. The numerical results will be discussed and compared to experimental and clinical results obtained by collaborators, to progress on the understanding of the inner mechanisms of chronic respiratory diseases.

Neutral dynamics and ion energy transport in MST plasma

NASA Astrophysics Data System (ADS)

Xing, Zichuan; Nornberg, Mark; den Hartog, Daniel; Kumar, Santosh; Anderson, Jay

2015-11-01

Neutral dynamics can have a significant effect on ion energy transport through charge exchange collisions. Whereas previously charge exchange was considered a direct loss mechanism in MST plasmas, new analysis indicates that significant thermal charge exchange neutrals are reionized. Further, the temperatures of the neutral species in the core of the plasma are suspected to be much higher than room temperature, which has a large effect on ion energy losses due to charge exchange. The DEGAS2 Monte Carlo simulation code is applied to the MST reversed field pinch experiment to estimate the density and temperature profile of the neutral species. The result is then used to further examine the effect of the neutral species on ion energy transport in improved confinement plasmas. This enables the development of a model that accounts for collisional equilibration between species, classical convective and conductive energy transport, and energy loss due to charge exchange collisions. The goal is to quantify classical, stochastic, and anomalous ion heating and transport in RFP plasmas. Work supported by the US DOE. DEGAS2 is provided by PPPL and STRAHL is provided by Ralph Dux of the Max-Planck-Institut fur Plasmaphysik.

Ion Transport across Biological Membranes by Carborane-Capped Gold Nanoparticles.

PubMed

Grzelczak, Marcin P; Danks, Stephen P; Klipp, Robert C; Belic, Domagoj; Zaulet, Adnana; Kunstmann-Olsen, Casper; Bradley, Dan F; Tsukuda, Tatsuya; Viñas, Clara; Teixidor, Francesc; Abramson, Jonathan J; Brust, Mathias

2017-12-26

Carborane-capped gold nanoparticles (Au/carborane NPs, 2-3 nm) can act as artificial ion transporters across biological membranes. The particles themselves are large hydrophobic anions that have the ability to disperse in aqueous media and to partition over both sides of a phospholipid bilayer membrane. Their presence therefore causes a membrane potential that is determined by the relative concentrations of particles on each side of the membrane according to the Nernst equation. The particles tend to adsorb to both sides of the membrane and can flip across if changes in membrane potential require their repartitioning. Such changes can be made either with a potentiostat in an electrochemical cell or by competition with another partitioning ion, for example, potassium in the presence of its specific transporter valinomycin. Carborane-capped gold nanoparticles have a ligand shell full of voids, which stem from the packing of near spherical ligands on a near spherical metal core. These voids are normally filled with sodium or potassium ions, and the charge is overcompensated by excess electrons in the metal core. The anionic particles are therefore able to take up and release a certain payload of cations and to adjust their net charge accordingly. It is demonstrated by potential-dependent fluorescence spectroscopy that polarized phospholipid membranes of vesicles can be depolarized by ion transport mediated by the particles. It is also shown that the particles act as alkali-ion-specific transporters across free-standing membranes under potentiostatic control. Magnesium ions are not transported.

Ion Transport via Structural Relaxations in Polymerized Ionic Liquids

NASA Astrophysics Data System (ADS)

Ganesan, Venkat; Mogurampelly, Santosh

We study the mechanisms underlying ion transport in poly(1-butyl-3-vinylimidazolium-hexafluorophosphate) polymer electrolytes. We consider polymer electrolytes of varying polymerized ionic liquid to ionic liquid (polyIL:IL) ratios and use atomistic molecular dynamics (MD) simulations to probe the dynamical and structural characteristics of the electrolyte. Our results reveal that anion diffusion along polymer backbone occurs primarily viathe formation and breaking of ion-pairs involving threepolymerized cationic monomers of twodifferent polymer chains. Moreover, we observe that the ionic diffusivities exhibit a direct correlation with the structural relaxation times of the ion-pairs and hydrogen bonds (H-bonds). These results provide new insights into the mechanisms underlying ion transport in polymerized ionic liquid electrolytes.

Toluene diisocyanate caused electrophysiological disturbances in the upper airways wall.

PubMed

Piskorska, Elzbieta; Hołyńska-Iwan, Iga; Kaczorowski, Piotr; Soczywko-Ciudzińska, Julita; Wiciński, Michał; Lampka, Magdalena; Smuszkiewicz, Piotr; Tyrakowski, Tomasz

2009-01-01

Toluene diisocyanate (TDI) due to its widespread use in industry is one of the most common and well-known causes of occupational asthma and Reactive Airways Dysfunction Syndrome (RADS). In this study the impact of TDI on the electrophysiological properties of the airways wall, particularly on the mechanisms of absorption of sodium ions and chloride ions secretion was evaluated. Isolated rabbit tracheal wall (from outbred stock animals) was mounted in an apparatus for electrophysiological experiments by means of Ussing method and was mechanically stimulated by the jet flux of specified fluid directed onto the mucosal surface of the tissue from a peristaltic pump. The measured parameters were: transepithelial potential difference under control conditions (PD, mV), after mechanical stimulation (dPD or physiological reaction of hyperpolarization, mV) and electric resistance (R, Omega cm2). When TDI (0.035 mM) was added to stimulation fluid, only the immediate reaction was identified and when it was added to incubation fluid and other experimental fluids, the late (post-incubation) reaction was determined. The experiments involving the inhibition of Na+ by amiloride and Cl- by bumetanide were also performed. A series of functional tests for 72 pieces of tracheal wall from 36 animals were performed. It has been shown that short-term exposure to TDI significantly changed the course of reactions to mechanical stimulation. Also after incubation in the presence of TDI, the reactions to mechanical stimulation were changed in relation to control conditions. The immediate reaction of the isolated rabbit tracheal wall after exposure to TDI depends on the duration of exposure and on the physiological condition of the tissue in respect of sodium and chloride ion transport.

Breathtaking TRP Channels: TRPA1 and TRPV1 in Airway Chemosensation and Reflex Control

PubMed Central

Bessac, Bret F.; Jordt, Sven-Eric

2009-01-01

New studies have revealed an essential role for TRPA1, a sensory neuronal TRP ion channel, in airway chemosensation and inflammation. TRPA1 is activated by chlorine, reactive oxygen species and noxious constituents of smoke and smog, initiating irritation and airway reflex responses. Together with TRPV1, the capsaicin receptor, TRPA1 may contribute to chemical hypersensitivity, chronic cough and airway inflammation in asthma, COPD and reactive airway dysfunction syndrome. PMID:19074743

Measurements of Turbulent Transport of Fast Ions in the LAPD

NASA Astrophysics Data System (ADS)

Zhang, Y.; Boehmer, H.; Heidbrink, W. W.; McWilliams, R.; Zhao, L.; Carter, T.; Leneman, D.; Vincena, S.

2004-11-01

Understanding the spatial transport induced by fluctuations is important to the confinement of magnetized plasmas. The paradox of fast ions being much better confined than thermal ions, i.e. the effective diffusion coefficient of fast ions being much smaller than that of thermal ions, has been observed experimentally [1], explained theoretically [2], and analyzed by simulations [3]. Gyroradius averaging and drift averaging are two predicted effects that are responsible for reduced fast-ion transport. Our goal is to quantitatively confirm these effects and make further exploration by measuring fast-ion transport as a function of gyroradius in the LArge Plasma Device (LAPD) plasma with well-characterized background fluctuations. A 3D gridded analyzer is used to measure the spatial profile of the beam produced by an ion gun launching 500 eV Argon ions [4]. Strong drift wave fluctuations are generated by inserting a disk into the center of the plasma. First results will be presented. [1] W. Heidbrink, G. Sadler, Nucl. Fusion, Vol. 34, p. 535 (1994); [2] P. C. Efthimion et al., Plasma Phys. and Cont. Nucl. Fusion Res., Vol. 1, p. 307 (1988); [3] G. Manfredi, R. Dendy, Phys. Rev. Lett. 76, p. 4360 (1996); [4] H. Boehmer et al. , Rev. Sci. Instrum. , Vol. 75, p. 1013 (2002)

Engineering Heteromaterials to Control Lithium Ion Transport Pathways

DOE PAGES

Liu, Yang; Vishniakou, Siarhei; Yoo, Jinkyoung; ...

2015-12-21

Safe and efficient operation of lithium ion batteries requires precisely directed flow of lithium ions and electrons to control the first directional volume changes in anode and cathode materials. Understanding and controlling the lithium ion transport in battery electrodes becomes crucial to the design of high performance and durable batteries. Some recent work revealed that the chemical potential barriers encountered at the surfaces of heteromaterials play an important role in directing lithium ion transport at nanoscale. We utilize in situ transmission electron microscopy to demonstrate that we can switch lithiation pathways from radial to axial to grain-by-grain lithiation through themore » systematic creation of heteromaterial combinations in the Si-Ge nanowire system. Furthermore, our systematic studies show that engineered materials at nanoscale can overcome the intrinsic orientation-dependent lithiation, and open new pathways to aid in the development of compact, safe, and efficient batteries.« less

Engineering Heteromaterials to Control Lithium Ion Transport Pathways

PubMed Central

Liu, Yang; Vishniakou, Siarhei; Yoo, Jinkyoung; Dayeh, Shadi A.

2015-01-01

Safe and efficient operation of lithium ion batteries requires precisely directed flow of lithium ions and electrons to control the first directional volume changes in anode and cathode materials. Understanding and controlling the lithium ion transport in battery electrodes becomes crucial to the design of high performance and durable batteries. Recent work revealed that the chemical potential barriers encountered at the surfaces of heteromaterials play an important role in directing lithium ion transport at nanoscale. Here, we utilize in situ transmission electron microscopy to demonstrate that we can switch lithiation pathways from radial to axial to grain-by-grain lithiation through the systematic creation of heteromaterial combinations in the Si-Ge nanowire system. Our systematic studies show that engineered materials at nanoscale can overcome the intrinsic orientation-dependent lithiation, and open new pathways to aid in the development of compact, safe, and efficient batteries. PMID:26686655

Nonperturbative methods in HZE ion transport

NASA Technical Reports Server (NTRS)

Wilson, John W.; Badavi, Francis F.; Costen, Robert C.; Shinn, Judy L.

1993-01-01

A nonperturbative analytic solution of the high charge and energy (HZE) Green's function is used to implement a computer code for laboratory ion beam transport. The code is established to operate on the Langley Research Center nuclear fragmentation model used in engineering applications. Computational procedures are established to generate linear energy transfer (LET) distributions for a specified ion beam and target for comparison with experimental measurements. The code is highly efficient and compares well with the perturbation approximations.

Ion transport in the microporous titanosilicate ETS-10.

PubMed

Wei, Ta-Chen; Hillhouse, Hugh W

2006-07-20

Impedance spectroscopy was used to investigate ion transport in the microporous crystalline framework titanosilicate ETS-10 in the frequency range from 1 Hz to 10 MHz. These data were compared to measured data from the microporous aluminosilicate zeolite X. Na-ETS-10 was found to have a lower activation energy for ion conduction than that of NaX, 58.5 kJ/mol compared to 66.8 kJ/mol. However, the dc conductivity and ion hopping rate for Na-ETS-10 were also lower than NaX. This was found to be due to the smaller entropy contribution in Na-ETS-10 because of its high cation site occupancy. This was verified by ion exchanging Na(+) with Cu(2+) in both microporous frameworks. This exchange decreases the cation site occupancy and reduces correlation effects. The exchanged Cu-ETS-10 was found to have both lower activation energy and higher ionic conductivity than CuX. Zeolite X has the highest ion conductivity among the zeolites, and thus the data shown here indicate that ETS-10 has more facile transport of higher valence cations which may be important for ion-exchange, environmental remediation of radionucleotides, and nanofabrication.

Ion transport in sub-5-nm graphene nanopores.

PubMed

Suk, Myung E; Aluru, N R

2014-02-28

Graphene nanopore is a promising device for single molecule sensing, including DNA bases, as its single atom thickness provides high spatial resolution. To attain high sensitivity, the size of the molecule should be comparable to the pore diameter. However, when the pore diameter approaches the size of the molecule, ion properties and dynamics may deviate from the bulk values and continuum analysis may not be accurate. In this paper, we investigate the static and dynamic properties of ions with and without an external voltage drop in sub-5-nm graphene nanopores using molecular dynamics simulations. Ion concentration in graphene nanopores sharply drops from the bulk concentration when the pore radius is smaller than 0.9 nm. Ion mobility in the pore is also smaller than bulk ion mobility due to the layered liquid structure in the pore-axial direction. Our results show that a continuum analysis can be appropriate when the pore radius is larger than 0.9 nm if pore conductivity is properly defined. Since many applications of graphene nanopores, such as DNA and protein sensing, involve ion transport, the results presented here will be useful not only in understanding the behavior of ion transport but also in designing bio-molecular sensors.

Ion-Transport Design for High-Performance Na+-Based Electrochromics.

PubMed

Li, Ran; Li, Kerui; Wang, Gang; Li, Lei; Zhang, Qiangqiang; Yan, Jinhui; Chen, Yao; Zhang, Qinghong; Hou, Chengyi; Li, Yaogang; Wang, Hongzhi

2018-04-24

Sodium ion (Na + )-based electrochemical systems have been extensively investigated in batteries and supercapacitors and also can be quality candidates for electrochromic (EC) devices. However, poor diffusion kinetics and severe EC performance degradation occur during the intercalation/deintercalation processes because the ionic radii of Na + are larger than those of conventional intercalation ions. Here, through intentional design of ion-transport channels in metal-organic frameworks (MOFs), Na + serves as an efficient intercalation ion for incorporation into a nanostructured electrode with a high diffusion coefficient of approximately 10 -8 cm 2 s -1 . As a result, the well-designed MOF-based EC device demonstrates desirable Na + EC performance, including fast switching speed, multicolor switching, and high stability. A smart "quick response code" display is fabricated using a mask-free laser writing method for application in the "Internet of Things". In addition, the concept of ion transport pathway design can be widely adopted for fabricating high-performance ion intercalation materials and devices for consumer electronics.

Transport of Light Ions in Matter

NASA Technical Reports Server (NTRS)

Wilson, J. W.; Cucinotta, F. A.; Tai, H.; Shinn, J. L.; Chun, S. Y.; Tripathi, R. K.; Sihver, L.

1998-01-01

A recent set of light ion experiments are analyzed using the Green's function method of solving the Boltzmann equation for ions of high charge and energy (the GRNTRN transport code) and the NUCFRG2 fragmentation database generator code. Although the NUCFRG2 code reasonably represents the fragmentation of heavy ions, the effects of light ion fragmentation requires a more detailed nuclear model including shell structure and short range correlations appearing as tightly bound clusters in the light ion nucleus. The most recent NTJCFRG2 code is augmented with a quasielastic alpha knockout model and semiempirical adjustments (up to 30 percent in charge removal) in the fragmentation process allowing reasonable agreement with the experiments to be obtained. A final resolution of the appropriate cross sections must await the full development of a coupled channel reaction model in which shell structure and clustering can be accurately evaluated.

Ion Transport across Biological Membranes by Carborane-Capped Gold Nanoparticles

PubMed Central

2017-01-01

Carborane-capped gold nanoparticles (Au/carborane NPs, 2–3 nm) can act as artificial ion transporters across biological membranes. The particles themselves are large hydrophobic anions that have the ability to disperse in aqueous media and to partition over both sides of a phospholipid bilayer membrane. Their presence therefore causes a membrane potential that is determined by the relative concentrations of particles on each side of the membrane according to the Nernst equation. The particles tend to adsorb to both sides of the membrane and can flip across if changes in membrane potential require their repartitioning. Such changes can be made either with a potentiostat in an electrochemical cell or by competition with another partitioning ion, for example, potassium in the presence of its specific transporter valinomycin. Carborane-capped gold nanoparticles have a ligand shell full of voids, which stem from the packing of near spherical ligands on a near spherical metal core. These voids are normally filled with sodium or potassium ions, and the charge is overcompensated by excess electrons in the metal core. The anionic particles are therefore able to take up and release a certain payload of cations and to adjust their net charge accordingly. It is demonstrated by potential-dependent fluorescence spectroscopy that polarized phospholipid membranes of vesicles can be depolarized by ion transport mediated by the particles. It is also shown that the particles act as alkali-ion-specific transporters across free-standing membranes under potentiostatic control. Magnesium ions are not transported. PMID:29161496

Fluid breakup in carbon nanotubes: An explanation of ultrafast ion transport

NASA Astrophysics Data System (ADS)

Gao, Xiang; Zhao, Tianshou; Li, Zhigang

2017-09-01

Ultrafast ion transport in carbon nanotubes (CNTs) has been experimentally observed, but the underlying mechanism is unknown. In this work, we investigate ion transport in CNTs through molecular dynamics (MD) simulations. It is found that the flow in CNTs undergoes a transition from the passage of a continuous liquid chain to the transport of isolated ion-water clusters as the CNT length or the external electric filed strength is increased. The breakup of the liquid chain in CNTs greatly reduces the resistance caused by the hydrogen bonds of water and significantly enhances the ionic mobility, which explains the two-order-magnitude enhancement of ionic conductance in CNTs reported in the literature. A theoretical criterion for fluid breakup is proposed, which agrees well with MD results. The fluid breakup phenomenon provides new insights into enhancing ion transport in nanoconfinements.

Ion transport in complex layered graphene-based membranes with tuneable interlayer spacing.

PubMed

Cheng, Chi; Jiang, Gengping; Garvey, Christopher J; Wang, Yuanyuan; Simon, George P; Liu, Jefferson Z; Li, Dan

2016-02-01

Investigation of the transport properties of ions confined in nanoporous carbon is generally difficult because of the stochastic nature and distribution of multiscale complex and imperfect pore structures within the bulk material. We demonstrate a combined approach of experiment and simulation to describe the structure of complex layered graphene-based membranes, which allows their use as a unique porous platform to gain unprecedented insights into nanoconfined transport phenomena across the entire sub-10-nm scales. By correlation of experimental results with simulation of concentration-driven ion diffusion through the cascading layered graphene structure with sub-10-nm tuneable interlayer spacing, we are able to construct a robust, representative structural model that allows the establishment of a quantitative relationship among the nanoconfined ion transport properties in relation to the complex nanoporous structure of the layered membrane. This correlation reveals the remarkable effect of the structural imperfections of the membranes on ion transport and particularly the scaling behaviors of both diffusive and electrokinetic ion transport in graphene-based cascading nanochannels as a function of channel size from 10 nm down to subnanometer. Our analysis shows that the range of ion transport effects previously observed in simple one-dimensional nanofluidic systems will translate themselves into bulk, complex nanoslit porous systems in a very different manner, and the complex cascading porous circuities can enable new transport phenomena that are unattainable in simple fluidic systems.

Decoupled Ion Transport in a Protein-Based Solid Ion Conductor.

PubMed

Fu, Xuewei; Jewel, Yead; Wang, Yu; Liu, Jin; Zhong, Wei-Hong

2016-11-03

Simultaneous achievement of good electrochemical and mechanical properties is crucial for practical applications of solid ion conductors. Conventional polymer conductors suffer from low conductivity, low transference number, and deteriorated mechanical properties with the enhancement of conductivity, resulting from the coupling between ion transport and polymer movement. Here we present a successful fabrication and fundamental understanding of a high performance soy protein-based solid conductor. The conductor shows ionic conductivity of ∼10 -5 S/cm, transference number of 0.94, and modulus of 1 GPa at room temperature, and still remains flexible and easily processable. Molecular simulations indicate that this is due to appropriate manipulation of the protein structures for effective exploitation of protein functional groups. A decoupled transport mechanism, which is able to explain all results, is proposed. The new insights can be utilized to provide guidelines for design, optimization, and fabrication of high performance biosolid conductors.

Alteration of corneal epithelial ion transport by sympathectomy.

PubMed

Klyce, S D; Beuerman, R W; Crosson, C E

1985-04-01

The cornea is dually innervated, receiving afferent nerves from the trigeminal ganglion and efferent nerves from the superior cervical ganglion. This study examines the specific effects of superior cervical ganglionectomy (SCGX) on the in vitro ion transport characteristics of the rabbit corneal epithelium. Two weeks after SCGX, epithelial Cl--dependent transport and total ionic conductance were increased in comparison to values obtained in paired control eyes. This increased transport level appeared to be independent of membrane receptor activity as demonstrated by lack of responsiveness to alpha-adrenergic, beta-adrenergic, serotonergic, dopaminergic, nicotinic cholinergic, or muscarinic cholinergic blockade. Nevertheless, SCGX produced a supersensitivity to epinephrine-stimulated transport as measured by the responsiveness of the ion transport current. Furthermore, SCGX abolished the responsiveness of the epithelium to serotonin. On the basis of these and earlier findings, the authors conclude that corneal sympathetic innervation influences membrane and receptor properties. Autonomic neurotrophic effects in the corneal epithelium include suppression of apical membrane Cl- permeability and of beta-adrenoreceptor sensitivity to biogenic amines. It is proposed that the corneal serotonergic receptors that activate Cl- transport lie on the sympathetic nerve terminals and stimulate this transport process by causing the neural release of a catecholamine.

Excess surface area in bioelectrochemical systems causes ion transport limitations.

PubMed

Harrington, Timothy D; Babauta, Jerome T; Davenport, Emily K; Renslow, Ryan S; Beyenal, Haluk

2015-05-01

We investigated ion transport limitations on 3D graphite felt electrodes by growing Geobacter sulfurreducens biofilms with advection to eliminate external mass transfer limitations. We characterized ion transport limitations by: (i) showing that serially increasing NaCl concentration up to 200 mM increased current linearly up to a total of +273% vs. 0 mM NaCl under advective conditions; (ii) growing the biofilm with a starting concentration of 200 mM NaCl, which led to a maximum current increase of 400% vs. current generation without NaCl, and (iii) showing that un-colonized surface area remained even after steady-state current was reached. After accounting for iR effects, we confirmed that the excess surface area existed despite a non-zero overpotential. The fact that the biofilm was constrained from colonizing and producing further current under these conditions confirmed the biofilms under study here were ion transport-limited. Our work demonstrates that the use of high surface area electrodes may not increase current density when the system design allows ion transport limitations to become dominant. © 2014 Wiley Periodicals, Inc.

Self-pinched transport for ion-driven inertial confinement fusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Welch, D.R.; Olson, C.L.

Efficient transport of intense ion beams is necessary for ion-driven inertial confinement fusion (ICF). The self-pinched transport scheme involves the focusing of an ion beam to a radius of about 1 cm or less. At this radius, using the beam`s self-magnetic field for confinement, the ion beam propagates through the reactor chamber to an ICF target. A promising regime for self-pinched transport involves the injection of a high current beam into an initially neutral gas at about 200 mTorr less. A simple equilibrium theory of a beam with a temporally pinching radial envelope predicts that large confining magnetic fields aremore » possible with net currents of more than 50% of the beam current. The magnitude of these fields is strongly dependent on the rate of ionization of the given ion species. The authors have simulated ion-beam propagation, using the hybrid code IPROP, which self-consistently calculates the gas breakdown and electromagnetic fields. In agreement, with the theory, a propagation window of 20-200 mTorr of argon is calculated for a 50 kA, 5 MeV proton beam similar to the parameters of the SABRE accelerator at Sandia National Laboratories. The authors present simulations of the focusing and propagation of the SABRE beam, with the purpose of designing a self-pinch experiment.« less

Altered ion transport in normal human bronchial epithelial cells following exposure to chemically distinct metal welding fume particles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fedan, Jeffrey S., E-mail: jsf2@cdc.gov; Thompson,

Welding fume inhalation causes pulmonary toxicity, including susceptibility to infection. We hypothesized that airway epithelial ion transport is a target of fume toxicity, and investigated the effects of fume particulates from manual metal arc-stainless steel (MMA-SS) and gas metal arc-mild steel (GMA-MS) on ion transport in normal human bronchial epithelium (NHBE) cultured in air-interface. MMA-SS particles, more soluble than GMA-MS particles, contain Cr, Ni, Fe and Mn; GMA-MS particles contain Fe and Mn. MMA-SS or GMA-MS particles (0.0167–166.7 μg/cm{sup 2}) were applied apically to NHBEs. After 18 h transepithelial potential difference (V{sub t}), resistance (R{sub t}), and short circuit currentmore » (I{sub sc}) were measured. Particle effects on Na{sup +} and Cl¯ channels and the Na{sup +},K{sup +},2Cl¯-cotransporter were evaluated using amiloride (apical), 5-nitro-2-[(3-phenylpropyl)amino]benzoic acid (NPPB, apical), and bumetanide (basolateral), respectively. MMA-SS (0.0167–16.7 μg/cm{sup 2}) increased basal V{sub t}. Only 16.7 μg/cm{sup 2} GMA-MS increased basal V{sub t} significantly. MMA-SS or GMA-MS exposure potentiated I{sub sc} responses (decreases) to amiloride and bumetanide, while not affecting those to NPPB, GMA-MS to a lesser degree than MMA-SS. Variable effects on R{sub t} were observed in response to amiloride, and bumetanide. Generally, MMA-SS was more potent in altering responses to amiloride and bumetanide than GMA-MS. Hyperpolarization occurred in the absence of LDH release, but decreases in V{sub t}, R{sub t}, and I{sub sc} at higher fume particulate doses accompanied LDH release, to a greater extent for MMA-SS. Thus, Na{sup +} transport and Na{sup +},K{sup +},2Cl¯-cotransport are affected by fume exposure; MMA-MS is more potent than GMA-MS. Enhanced Na{sup +} absorption and decreased airway surface liquid could compromise defenses against infection. - Highlights: • Welding fume particle toxicity was investigated in human

MR imaging of apparent 3He gas transport in narrow pipes and rodent airways

NASA Astrophysics Data System (ADS)

Minard, Kevin R.; Jacob, Richard E.; Laicher, Gernot; Einstein, Daniel R.; Kuprat, Andrew P.; Corley, Richard A.

2008-10-01

High sensitivity makes hyperpolarized 3He an attractive signal source for visualizing gas flow with magnetic resonance (MR) imaging. Its rapid Brownian motion, however, can blur observed flow lamina and alter measured diffusion rates when excited nuclei traverse shear-induced velocity gradients during data acquisition. Here, both effects are described analytically, and predicted values for measured transport during laminar flow through a straight, 3.2-mm diameter pipe are validated using two-dimensional (2D) constant-time images of different binary gas mixtures. Results show explicitly how measured transport in narrow conduits is characterized by apparent values that depend on underlying gas dynamics and imaging time. In ventilated rats, this is found to obscure acquired airflow images. Nevertheless, flow splitting at airway branches is still evident and use of 3D vector flow mapping is shown to reveal surprising detail that highlights the correlation between gas dynamics and lung structure.

A synthetic ion transporter that disrupts autophagy and induces apoptosis by perturbing cellular chloride concentrations

NASA Astrophysics Data System (ADS)

Busschaert, Nathalie; Park, Seong-Hyun; Baek, Kyung-Hwa; Choi, Yoon Pyo; Park, Jinhong; Howe, Ethan N. W.; Hiscock, Jennifer R.; Karagiannidis, Louise E.; Marques, Igor; Félix, Vítor; Namkung, Wan; Sessler, Jonathan L.; Gale, Philip A.; Shin, Injae

2017-07-01

Perturbations in cellular chloride concentrations can affect cellular pH and autophagy and lead to the onset of apoptosis. With this in mind, synthetic ion transporters have been used to disturb cellular ion homeostasis and thereby induce cell death; however, it is not clear whether synthetic ion transporters can also be used to disrupt autophagy. Here, we show that squaramide-based ion transporters enhance the transport of chloride anions in liposomal models and promote sodium chloride influx into the cytosol. Liposomal and cellular transport activity of the squaramides is shown to correlate with cell death activity, which is attributed to caspase-dependent apoptosis. One ion transporter was also shown to cause additional changes in lysosomal pH, which leads to impairment of lysosomal enzyme activity and disruption of autophagic processes. This disruption is independent of the initiation of apoptosis by the ion transporter. This study provides the first experimental evidence that synthetic ion transporters can disrupt both autophagy and induce apoptosis.

AEROSOL TRANSPORT AND DEPOSITION IN SEQUENTIALLY BIFURCATING AIRWAYS

EPA Science Inventory

Deposition patterns and efficiencies of a dilute suspension of inhaled particles in three-dimensional double bifurcating airway models for both in-plane and 90 deg out-of-plane configurations have been numerically simulated assuming steady, laminar, constant-property air flow wit...

Electron/Ion Transport Enhancer in High Capacity Li-Ion Battery Anodes

DOE PAGES

Kwon, Yo Han; Minnici, Krysten; Huie, Matthew M.; ...

2016-08-30

In this paper, magnetite (Fe 3O 4) was used as a model high capacity metal oxide active material to demonstrate advantages derived from consideration of both electron and ion transport in the design of composite battery electrodes. The conjugated polymer, poly[3-(potassium-4-butanoate) thiophene] (PPBT), was introduced as a binder component, while polyethylene glycol (PEG) was coated onto the surface of Fe 3O 4 nanoparticles. The introduction of PEG reduced aggregate size, enabled effective dispersion of the active materials and facilitated ionic conduction. As a binder for the composite electrode, PPBT underwent electrochemical doping which enabled the formation of effective electrical bridgesmore » between the carbon and Fe 3O 4 components, allowing for more efficient electron transport. Additionally, the PPBT carboxylic moieties effect a porous structure, and stable electrode performance. Finally, the methodical consideration of both enhanced electron and ion transport by introducing a carboxylated PPBT binder and PEG surface treatment leads to effectively reduced electrode resistance, which improved cycle life performance and rate capabilities.« less

Regional differences in rat conjunctival ion transport activities

PubMed Central

Yu, Dongfang; Thelin, William R.; Rogers, Troy D.; Stutts, M. Jackson; Randell, Scott H.; Grubb, Barbara R.

2012-01-01

Active ion transport and coupled osmotic water flow are essential to maintain ocular surface health. We investigated regional differences in the ion transport activities of the rat conjunctivas and compared these activities with those of cornea and lacrimal gland. The epithelial sodium channel (ENaC), sodium/glucose cotransporter 1 (Slc5a1), transmembrane protein 16 (Tmem16a, b, f, and g), cystic fibrosis transmembrane conductance regulator (Cftr), and mucin (Muc4, 5ac, and 5b) mRNA expression was characterized by RT-PCR. ENaC proteins were measured by Western blot. Prespecified regions (palpebral, fornical, and bulbar) of freshly isolated conjunctival tissues and cell cultures were studied electrophysiologically with Ussing chambers. The transepithelial electrical potential difference (PD) of the ocular surface was also measured in vivo. The effect of amiloride and UTP on the tear volume was evaluated in lacrimal gland excised rats. All selected genes were detected but with different expression patterns. We detected αENaC protein in all tissues, βENaC in palpebral and fornical conjunctiva, and γENaC in all tissues except lacrimal glands. Electrophysiological studies of conjunctival tissues and cell cultures identified functional ENaC, SLC5A1, CFTR, and TMEM16. Fornical conjunctiva exhibited the most active ion transport under basal conditions amongst conjunctival regions. PD measurements confirmed functional ENaC-mediated Na+ transport on the ocular surface. Amiloride and UTP increased tear volume in lacrimal gland excised rats. This study demonstrated that the different regions of the conjunctiva exhibited a spectrum of ion transport activities. Understanding the specific functions of distinct regions of the conjunctiva may foster a better understanding of the physiology maintaining hydration of the ocular surface. PMID:22814399

Regional differences in rat conjunctival ion transport activities.

PubMed

Yu, Dongfang; Thelin, William R; Rogers, Troy D; Stutts, M Jackson; Randell, Scott H; Grubb, Barbara R; Boucher, Richard C

2012-10-01

Active ion transport and coupled osmotic water flow are essential to maintain ocular surface health. We investigated regional differences in the ion transport activities of the rat conjunctivas and compared these activities with those of cornea and lacrimal gland. The epithelial sodium channel (ENaC), sodium/glucose cotransporter 1 (Slc5a1), transmembrane protein 16 (Tmem16a, b, f, and g), cystic fibrosis transmembrane conductance regulator (Cftr), and mucin (Muc4, 5ac, and 5b) mRNA expression was characterized by RT-PCR. ENaC proteins were measured by Western blot. Prespecified regions (palpebral, fornical, and bulbar) of freshly isolated conjunctival tissues and cell cultures were studied electrophysiologically with Ussing chambers. The transepithelial electrical potential difference (PD) of the ocular surface was also measured in vivo. The effect of amiloride and UTP on the tear volume was evaluated in lacrimal gland excised rats. All selected genes were detected but with different expression patterns. We detected αENaC protein in all tissues, βENaC in palpebral and fornical conjunctiva, and γENaC in all tissues except lacrimal glands. Electrophysiological studies of conjunctival tissues and cell cultures identified functional ENaC, SLC5A1, CFTR, and TMEM16. Fornical conjunctiva exhibited the most active ion transport under basal conditions amongst conjunctival regions. PD measurements confirmed functional ENaC-mediated Na(+) transport on the ocular surface. Amiloride and UTP increased tear volume in lacrimal gland excised rats. This study demonstrated that the different regions of the conjunctiva exhibited a spectrum of ion transport activities. Understanding the specific functions of distinct regions of the conjunctiva may foster a better understanding of the physiology maintaining hydration of the ocular surface.

Quantitative description of ion transport via plasma membrane of yeast and small cells.

PubMed

Volkov, Vadim

2015-01-01

Modeling of ion transport via plasma membrane needs identification and quantitative understanding of the involved processes. Brief characterization of main ion transport systems of a yeast cell (Pma1, Ena1, TOK1, Nha1, Trk1, Trk2, non-selective cation conductance) and determining the exact number of molecules of each transporter per a typical cell allow us to predict the corresponding ion flows. In this review a comparison of ion transport in small yeast cell and several animal cell types is provided. The importance of cell volume to surface ratio is emphasized. The role of cell wall and lipid rafts is discussed in respect to required increase in spatial and temporary resolution of measurements. Conclusions are formulated to describe specific features of ion transport in a yeast cell. Potential directions of future research are outlined based on the assumptions.

Quantitative description of ion transport via plasma membrane of yeast and small cells

PubMed Central

Volkov, Vadim

2015-01-01

Modeling of ion transport via plasma membrane needs identification and quantitative understanding of the involved processes. Brief characterization of main ion transport systems of a yeast cell (Pma1, Ena1, TOK1, Nha1, Trk1, Trk2, non-selective cation conductance) and determining the exact number of molecules of each transporter per a typical cell allow us to predict the corresponding ion flows. In this review a comparison of ion transport in small yeast cell and several animal cell types is provided. The importance of cell volume to surface ratio is emphasized. The role of cell wall and lipid rafts is discussed in respect to required increase in spatial and temporary resolution of measurements. Conclusions are formulated to describe specific features of ion transport in a yeast cell. Potential directions of future research are outlined based on the assumptions. PMID:26113853

Nano and Mesoscale Ion and Water Transport in Perfluorosulfonic AcidMembranes

DTIC Science & Technology

2017-10-01

Nano- and Mesoscale Ion and Water Transport in Perfluorosulfonic-Acid Membranes A. R. Crothers a,b , C. J. Radke a,b , A. Z. Weber a a...Berkeley, CA 94720, USA Water and aqueous cations transport along multiple length scales in perfluorosulfonic-acid membranes. Molecular interactions...as a function of hydration. A resistor network upscales the nanoscale properties to predict effective membrane ion and water transport and their

Functions of Ion Transport Peptide and Ion Transport Peptide-Like in the Red Flour Beetle Tribolium castaneum

USDA-ARS?s Scientific Manuscript database

Ion transport peptide (ITP) and ITP-like (ITPL) are highly conserved neuropeptides in insects and crustaceans. We investigated the alternatively spliced variants of ITP/ITPL in Tribolium castaneum to understand their functions. We identified three alternatively spliced transcripts named itp, itpl-...

Ion transport in complex layered graphene-based membranes with tuneable interlayer spacing

PubMed Central

Cheng, Chi; Jiang, Gengping; Garvey, Christopher J.; Wang, Yuanyuan; Simon, George P.; Liu, Jefferson Z.; Li, Dan

2016-01-01

Investigation of the transport properties of ions confined in nanoporous carbon is generally difficult because of the stochastic nature and distribution of multiscale complex and imperfect pore structures within the bulk material. We demonstrate a combined approach of experiment and simulation to describe the structure of complex layered graphene-based membranes, which allows their use as a unique porous platform to gain unprecedented insights into nanoconfined transport phenomena across the entire sub–10-nm scales. By correlation of experimental results with simulation of concentration-driven ion diffusion through the cascading layered graphene structure with sub–10-nm tuneable interlayer spacing, we are able to construct a robust, representative structural model that allows the establishment of a quantitative relationship among the nanoconfined ion transport properties in relation to the complex nanoporous structure of the layered membrane. This correlation reveals the remarkable effect of the structural imperfections of the membranes on ion transport and particularly the scaling behaviors of both diffusive and electrokinetic ion transport in graphene-based cascading nanochannels as a function of channel size from 10 nm down to subnanometer. Our analysis shows that the range of ion transport effects previously observed in simple one-dimensional nanofluidic systems will translate themselves into bulk, complex nanoslit porous systems in a very different manner, and the complex cascading porous circuities can enable new transport phenomena that are unattainable in simple fluidic systems. PMID:26933689

Mechanisms involved in the transport of mercuric ions in target tissues

PubMed Central

Bridges, Christy C.; Zalups, Rudolfs K.

2016-01-01

Mercury exists in the environment in various forms, all of which pose a risk to human health. Despite guidelines regulating the industrial release of mercury into the environment, humans continue to be exposed regularly to various forms of this metal via inhalation or ingestion. Following exposure, mercuric ions are taken up by and accumulate in numerous organs, including brain, intestine, kidney, liver, and placenta. In order to understand the toxicological effects of exposure to mercury, a thorough understanding of the mechanisms that facilitate entry of mercuric ions into target cells must first be obtained. A number of mechanisms for the transport of mercuric ions into target cells and organs have been proposed in recent years. However, the ability of these mechanisms to transport mercuric ions and the regulatory features of these carriers have not been characterized completely. The purpose of this review is to summarize the current findings related to the mechanisms that may be involved in the transport of inorganic and organic forms of mercury in target tissues and organs. This review will describe mechanisms known to be involved in the transport of mercury and will also propose additional mechanisms that may potentially be involved in the transport of mercuric ions into target cells. PMID:27422290

A Green's function method for high charge and energy ion transport.

PubMed

Chun, S Y; Khandelwal, G S; Wilson, J W

1996-02-01

A heavy-ion transport code using Green's function methods is developed. The low-order perturbation terms exhibiting the greatest energy variation are used as dominant energy-dependent terms, and the higher order collision terms are evaluated using nonperturbative methods. The recently revised NUCFRG database is used to evaluate the solution for comparison with experimental data for 625A MeV 20Ne and 517A MeV 40Ar ion beams. Improved agreements with the attenuation characteristics for neon ions are found, and reasonable agreement is obtained for the transport of argon ions in water.

Parallel Transport Quantum Logic Gates with Trapped Ions.

PubMed

de Clercq, Ludwig E; Lo, Hsiang-Yu; Marinelli, Matteo; Nadlinger, David; Oswald, Robin; Negnevitsky, Vlad; Kienzler, Daniel; Keitch, Ben; Home, Jonathan P

2016-02-26

We demonstrate single-qubit operations by transporting a beryllium ion with a controlled velocity through a stationary laser beam. We use these to perform coherent sequences of quantum operations, and to perform parallel quantum logic gates on two ions in different processing zones of a multiplexed ion trap chip using a single recycled laser beam. For the latter, we demonstrate individually addressed single-qubit gates by local control of the speed of each ion. The fidelities we observe are consistent with operations performed using standard methods involving static ions and pulsed laser fields. This work therefore provides a path to scalable ion trap quantum computing with reduced requirements on the optical control complexity.

Vocal fold ion transport and mucin expression following acrolein exposure

PubMed Central

Levendoski, Elizabeth Erickson; Sivasankar, M. Preeti

2014-01-01

The vocal fold epithelium is exposed to inhaled particulates including pollutants during breathing in everyday environments. Yet, our understanding of the effects of pollutants on vocal fold epithelial function is extremely limited. The objective of this study was to investigate the effect of the pollutant acrolein on two vocal fold epithelial mechanisms: ion transport and mucin synthesis. These mechanisms were chosen as each plays a critical role in vocal defense and in maintaining surface hydration which is necessary for optimal voice production. Healthy, native porcine vocal folds (N=85) were excised and exposed to an acrolein or sham challenge. A 60 minute acrolein, but not sham challenge significantly reduced ion transport and inhibited cyclic adenosine monophosphate-dependent increases in ion transport. Decreases in ion transport were associated with reduced sodium absorption. Within the same timeline, no significant acrolein-induced changes in mucin gene or protein expression were observed. These results improve our understanding of the effects of acrolein on key vocal fold epithelial functions and inform the development of future investigations that seek to elucidate the impact of a wide range of pollutant exposures on vocal fold health. PMID:24648011

Benchmarking of Neutron Production of Heavy-Ion Transport Codes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Remec, Igor; Ronningen, Reginald M.; Heilbronn, Lawrence

Accurate prediction of radiation fields generated by heavy ion interactions is important in medical applications, space missions, and in design and operation of rare isotope research facilities. In recent years, several well-established computer codes in widespread use for particle and radiation transport calculations have been equipped with the capability to simulate heavy ion transport and interactions. To assess and validate these capabilities, we performed simulations of a series of benchmark-quality heavy ion experiments with the computer codes FLUKA, MARS15, MCNPX, and PHITS. We focus on the comparisons of secondary neutron production. Results are encouraging; however, further improvements in models andmore » codes and additional benchmarking are required.« less

Progress in Ion Transport Membranes for Gas Separation Applications

NASA Astrophysics Data System (ADS)

Bose, Arun C.; Stiegel, Gary J.; Armstrong, Phillip A.; Halper, Barry J.; (Ted) Foster, E. P.

This chapter describes the evolution and advances of ion transport membranes for gas separation applications, especially separation of oxygen from air. In partnership with the US Department of Energy (DOE), Air Products and Chemicals, Inc. (Air Products) successfully developed a novel class of mixed ion-electron conducting materials and membrane architecture. These novel materials are referred to as ion transport membranes (ITM). Generically, ITMs consist of modified perovskite and brownmillerite oxide solid electrolytes and provide high oxygen anion and electron conduction typically at high temperatures driven by an oxygen potential gradient without the need for external power. The partial pressure ratio across the ITM layer creates the driving force for oxygen separation.

Ion sampling and transport in Inductively Coupled Plasma Mass Spectrometry

NASA Astrophysics Data System (ADS)

Farnsworth, Paul B.; Spencer, Ross L.

2017-08-01

Quantitative accuracy and high sensitivity in inductively coupled plasma mass spectrometry (ICP-MS) depend on consistent and efficient extraction and transport of analyte ions from an inductively coupled plasma to a mass analyzer, where they are sorted and detected. In this review we examine the fundamental physical processes that control ion sampling and transport in ICP-MS and compare the results of theory and computerized models with experimental efforts to characterize the flow of ions through plasma mass spectrometers' vacuum interfaces. We trace the flow of ions from their generation in the plasma, into the sampling cone, through the supersonic expansion in the first vacuum stage, through the skimmer, and into the ion optics that deliver the ions to the mass analyzer. At each stage we consider idealized behavior and departures from ideal behavior that affect the performance of ICP-MS as an analytical tool.

The extracellular microenvironment explains variations in passive drug transport across different airway epithelial cell types.

PubMed

Min, Kyoung Ah; Talattof, Arjang; Tsume, Yasuhiro; Stringer, Kathleen A; Yu, Jing-Yu; Lim, Dong Hyun; Rosania, Gus R

2013-08-01

We sought to identify key variables in cellular architecture and physiology that might explain observed differences in the passive transport properties of small molecule drugs across different airway epithelial cell types. Propranolol (PR) was selected as a weakly basic, model compound to compare the transport properties of primary (NHBE) vs. tumor-derived (Calu-3) cells. Differentiated on Transwell™ inserts, the architecture of pure vs. mixed cell co-cultures was studied with confocal microscopy followed by quantitative morphometric analysis. Cellular pharmacokinetic modeling was used to identify parameters that differentially affect PR uptake and transport across these two cell types. Pure Calu-3 and NHBE cells possessed different structural and functional properties. Nevertheless, mixed Calu-3 and NHBE cell co-cultures differentiated as stable cell monolayers. After measuring the total mass of PR, the fractional areas covered by Calu-3 and NHBE cells allowed deconvoluting the transport properties of each cell type. Based on the apparent thickness of the unstirred, cell surface aqueous layer, local differences in the extracellular microenvironment explained the measured variations in passive PR uptake and permeation between Calu-3 and NHBE cells. Mixed cell co-cultures can be used to compare the local effects of the extracellular microenvironment on drug uptake and transport across two epithelial cell types.

The Extracellular Microenvironment Explains Variations in Passive Drug Transport across Different Airway Epithelial Cell Types

PubMed Central

Min, Kyoung Ah; Talattof, Arjang; Tsume, Yasuhiro; Stringer, Kathleen A.; Yu, Jing-yu; Lim, Dong Hyun; Rosania, Gus R.

2013-01-01

Purpose We sought to identify key variables in cellular architecture and physiology that might explain observed differences in the passive transport properties of small molecule drugs across different airway epithelial cell types. Methods Propranolol (PR) was selected as a weakly basic, model compound to compare the transport properties of primary (NHBE) vs. tumor-derived (Calu-3) cells. Differentiated on Transwell™ inserts, the architecture of pure vs. mixed cell co-cultures was studied with confocal microscopy followed by quantitative morphometric analysis. Cellular pharmacokinetic modeling was used to identify parameters that differentially affect PR uptake and transport across these two cell types. Results Pure Calu-3 and NHBE cells possessed different structural and functional properties. Nevertheless, mixed Calu-3 and NHBE cell co-cultures differentiated as stable cell monolayers. After measuring the total mass of PR, the fractional areas covered by Calu-3 and NHBE cells allowed deconvoluting the transport properties of each cell type. Based on the apparent thickness of the unstirred, cell surface aqueous layer, local differences in extracellular microenvironment explained the measured variations in passive PR uptake and permeation between Calu-3 and NHBE cells. Conclusion Mixed cell co-cultures can be used to compare the local effects of the extracellular microenvironment on drug uptake and transport across two epithelial cell types. PMID:23708857

Crystal structure of a SLC11 (NRAMP) transporter reveals the basis for transition-metal ion transport.

PubMed

Ehrnstorfer, Ines A; Geertsma, Eric R; Pardon, Els; Steyaert, Jan; Dutzler, Raimund

2014-11-01

Members of the SLC11 (NRAMP) family transport iron and other transition-metal ions across cellular membranes. These membrane proteins are present in all kingdoms of life with a high degree of sequence conservation. To gain insight into the determinants of ion selectivity, we have determined the crystal structure of Staphylococcus capitis DMT (ScaDMT), a close prokaryotic homolog of the family. ScaDMT shows a familiar architecture that was previously identified in the amino acid permease LeuT. The protein adopts an inward-facing conformation with a substrate-binding site located in the center of the transporter. This site is composed of conserved residues, which coordinate Mn2+, Fe2+ and Cd2+ but not Ca2+. Mutations of interacting residues affect ion binding and transport in both ScaDMT and human DMT1. Our study thus reveals a conserved mechanism for transition-metal ion selectivity within the SLC11 family.

A multi-ion generalized transport model of the polar wind

NASA Technical Reports Server (NTRS)

Demars, H. G.; Schunk, R. W.

1994-01-01

The higher-order generalizations of the equations of standard hydrodynamics, known collectively as generalized transport theories, have been used since the early 1980s to describe the terrestrial polar wind. Inherent in the structure of generalized transport theories is the ability to describe not only interparticle collisions but also certain non-Maxwellian processes, such as heat flow and viscous stress, that are characteristic of any plasma flow that is not collision dominated. Because the polar wind exhibits a transition from collision-dominated to collisionless flow, generalized transport theories possess advantages for polar wind modeling not shared by either collision-dominated models (such as standard hydrodynamics) or collisionless models (such as those based on solving the collisionless Boltzmann equation). In general, previous polar wind models have used generalized transport equations to describe electrons and only one species of ion (H(+)). If other ion species were included in the models at all, it was in a simplified or semiempirical manner. The model described in this paper is the first polar wind model that uses a generalized transport theory (bi-Maxwellian-based 16-moment theory) to describe all of the species, both major and minor, in the polar wind plasma. In the model, electrons and three ion species (H(+), He(+), O(+)) are assumed to be major and several ion species are assumed to be minor (NO(+), Fe(+), O(++)). For all species, a complete 16-moment transport formulation is used, so that profiles of density, drift velocity, parallel and perpendicular temperatures, and the field-aligned parallel and perpendicular energy flows are obtained. In the results presented here, emphasis is placed on describing those constituents of the polar wind that have received little attention in past studies. In particular, characteristic solutions are presented for supersonic H(+) outflow and for both supersonic and subsonic outflows of the major ion He

Transport and Mixing Induced by Beating Cilia in Human Airways

PubMed Central

Chateau, Sylvain; D'Ortona, Umberto; Poncet, Sébastien; Favier, Julien

2018-01-01

The fluid transport and mixing induced by beating cilia, present in the bronchial airways, are studied using a coupled lattice Boltzmann—Immersed Boundary solver. This solver allows the simulation of both single and multi-component fluid flows around moving solid boundaries. The cilia are modeled by a set of Lagrangian points, and Immersed Boundary forces are computed onto these points in order to ensure the no-slip velocity conditions between the cilia and the fluids. The cilia are immersed in a two-layer environment: the periciliary layer (PCL) and the mucus above it. The motion of the cilia is prescribed, as well as the phase lag between two cilia in order to obtain a typical collective motion of cilia, known as metachronal waves. The results obtained from a parametric study show that antiplectic metachronal waves are the most efficient regarding the fluid transport. A specific value of phase lag, which generates the larger mucus transport, is identified. The mixing is studied using several populations of tracers initially seeded into the pericilary liquid, in the mucus just above the PCL-mucus interface, and in the mucus far away from the interface. We observe that each zone exhibits different chaotic mixing properties. The larger mixing is obtained in the PCL layer where only a few beating cycles of the cilia are required to obtain a full mixing, while above the interface, the mixing is weaker and takes more time. Almost no mixing is observed within the mucus, and almost all the tracers do not penetrate the PCL layer. Lyapunov exponents are also computed for specific locations to assess how the mixing is performed locally. Two time scales are introduced to allow a comparison between mixing induced by fluid advection and by molecular diffusion. These results are relevant in the context of respiratory flows to investigate the transport of drugs for patients suffering from chronic respiratory diseases. PMID:29559920

Transport and Mixing Induced by Beating Cilia in Human Airways.

PubMed

Chateau, Sylvain; D'Ortona, Umberto; Poncet, Sébastien; Favier, Julien

2018-01-01

The fluid transport and mixing induced by beating cilia, present in the bronchial airways, are studied using a coupled lattice Boltzmann-Immersed Boundary solver. This solver allows the simulation of both single and multi-component fluid flows around moving solid boundaries. The cilia are modeled by a set of Lagrangian points, and Immersed Boundary forces are computed onto these points in order to ensure the no-slip velocity conditions between the cilia and the fluids. The cilia are immersed in a two-layer environment: the periciliary layer (PCL) and the mucus above it. The motion of the cilia is prescribed, as well as the phase lag between two cilia in order to obtain a typical collective motion of cilia, known as metachronal waves. The results obtained from a parametric study show that antiplectic metachronal waves are the most efficient regarding the fluid transport. A specific value of phase lag, which generates the larger mucus transport, is identified. The mixing is studied using several populations of tracers initially seeded into the pericilary liquid, in the mucus just above the PCL-mucus interface, and in the mucus far away from the interface. We observe that each zone exhibits different chaotic mixing properties. The larger mixing is obtained in the PCL layer where only a few beating cycles of the cilia are required to obtain a full mixing, while above the interface, the mixing is weaker and takes more time. Almost no mixing is observed within the mucus, and almost all the tracers do not penetrate the PCL layer. Lyapunov exponents are also computed for specific locations to assess how the mixing is performed locally. Two time scales are introduced to allow a comparison between mixing induced by fluid advection and by molecular diffusion. These results are relevant in the context of respiratory flows to investigate the transport of drugs for patients suffering from chronic respiratory diseases.

Validation of Heavy Ion Transport Capabilities in PHITS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ronningen, Reginald M.

The performance of the Monte Carlo code system PHITS is validated for heavy ion transport capabilities by performing simulations and comparing results against experimental data from heavy ion reactions of benchmark quality. These data are from measurements of secondary neutron production cross sections in reactions of Xe at 400 MeV/u with lithium and lead targets, measurements of neutrons outside of thick concrete and iron shields, and measurements of isotope yields produced in the fragmentation of a 140 MeV/u 48Ca beam on a beryllium target and on a tantalum target. A practical example that tests magnetic field capabilities is shown formore » a simulated 48Ca beam at 500 MeV/u striking a lithium target to produce the rare isotope 44Si, with ion transport through a fragmentation-reaction magnetic pre-separator. The results of this study show that PHITS performs reliably for the simulation of radiation fields that is necessary for designing safe, reliable and cost effective future high-powered heavy-ion accelerators in rare isotope beam facilities.« less

An improved Green's function for ion beam transport

NASA Technical Reports Server (NTRS)

Tweed, J.; Wilson, J. W.; Tripathi, R. K.

2004-01-01

Ion beam transport theory allows testing of material transmission properties in the laboratory environment generated by particle accelerators. This is a necessary step in materials development and evaluation for space use. The approximations used in solving the Boltzmann transport equation for the space setting are often not sufficient for laboratory work and those issues are the main emphasis of the present work. In consequence, an analytic solution of the linear Boltzmann equation is pursued in the form of a Green's function allowing flexibility in application to a broad range of boundary value problems. It has been established that simple solutions can be found for high charge and energy (HZE) ions by ignoring nuclear energy downshifts and dispersion. Such solutions were found to be supported by experimental evidence with HZE ion beams when multiple scattering was added. Lacking from the prior solutions were range and energy straggling and energy downshift with dispersion associated with nuclear events. Recently, we have found global solutions including these effects providing a broader class of HZE ion solutions. c2004 COSPAR. Published by Elsevier Ltd. All rights reserved.

Pyrethroid stimulation of ion transport across frog skin.

PubMed

Cassano, Giuseppe; Bellantuono, Vito; Ardizzone, Concetta; Lippe, Claudio

2003-06-01

Pyrethroids are grouped into two classes (types I and II) because of the absence or presence of an alpha-cyano substituent and the production of a different intoxication syndrome in rodents. In this study, we investigated the effect of pyrethroids on the ion transport across frog skin (Rana esculenta). The short-circuit current value (estimate of ion transport) was increased by each of the eight pyrethroids tested, with the following order of potency: lambda-cyhalothrin > deltamethrin > alpha-cypermethrin = beta-cyfluthrin > bioallethrin > permethrin > bioresmethrin > phenothrin. The first four compounds are type II pyrethroids. Therefore, ion transport is stimulated more by type II pyrethroids than by type I. Experiments performed in the presence of amiloride support the conclusion that pyrethroids mainly increase Na+ absorption and to a lesser extent Cl- secretion. In these experiments, no systematic difference between type I and II pyrethroids was found. Finally, the stimulation by pyrethroids was inhibited by indomethacin and W7 (inhibitors of cyclooxygenases and the Ca2+/calmodulin system, respectively). These observations suggest that pyrethroids do not directly affect the epithelial Na+ channel (ENaC) but indirectly influence an intracellular event involved in ENaC modulation and linked to the Ca2+ signaling cascade.

Living with a leaky skin: upregulation of ion transport proteins during sloughing.

PubMed

Wu, Nicholas C; Cramp, Rebecca L; Franklin, Craig E

2017-06-01

Amphibian skin is a multifunctional organ providing protection from the external environment and facilitating the physiological exchange of gases, water and salts with the environment. In order to maintain these functions, the outer layer of skin is regularly replaced in a process called sloughing. During sloughing, the outermost layer of the skin is removed in its entirety, which has the potential to interfere with skin permeability and ion transport, disrupting homeostasis. In this study, we measured, in vivo , the effects of sloughing on the cutaneous efflux of ions in toads Rhinella marina kept in freshwater conditions. We also measured transepithelial potential, cutaneous resistance, active ion transport and the distribution, abundance and gene expression of the key ion transport proteins sodium-potassium ATPase (NKA) and epithelial sodium channel (ENaC) during sloughing. We hypothesised that the increase in transepithelial efflux of ions during sloughing is a consequence of increased permeability and/or a reduction in the abundance or expression of cutaneous ion transport proteins, resulting in disruption of internal ion homeostasis. There was a significant increase in sodium and chloride efflux during sloughing in R. marina However, although in vitro skin resistance decreased after sloughing, active sodium transport increased commensurate with an increase in NKA and ENaC protein abundance in the skin. These changes in skin function associated with sloughing did not affect the maintenance of internal electrolyte homeostasis. These results suggest that during sloughing, amphibians actively maintain internal homeostasis by increasing cutaneous rates of ion uptake. © 2017. Published by The Company of Biologists Ltd.

Metal ion transport quantified by ICP-MS in intact cells

PubMed Central

Figueroa, Julio A. Landero; Stiner, Cory A.; Radzyukevich, Tatiana L.; Heiny, Judith A.

2016-01-01

The use of ICP-MS to measure metal ion content in biological tissues offers a highly sensitive means to study metal-dependent physiological processes. Here we describe the application of ICP-MS to measure membrane transport of Rb and K ions by the Na,K-ATPase in mouse skeletal muscles and human red blood cells. The ICP-MS method provides greater precision and statistical power than possible with conventional tracer flux methods. The method is widely applicable to studies of other metal ion transporters and metal-dependent processes in a range of cell types and conditions. PMID:26838181

Metal ion transport quantified by ICP-MS in intact cells.

PubMed

Figueroa, Julio A Landero; Stiner, Cory A; Radzyukevich, Tatiana L; Heiny, Judith A

2016-02-03

The use of ICP-MS to measure metal ion content in biological tissues offers a highly sensitive means to study metal-dependent physiological processes. Here we describe the application of ICP-MS to measure membrane transport of Rb and K ions by the Na,K-ATPase in mouse skeletal muscles and human red blood cells. The ICP-MS method provides greater precision and statistical power than possible with conventional tracer flux methods. The method is widely applicable to studies of other metal ion transporters and metal-dependent processes in a range of cell types and conditions.

Effect of airway acidosis and alkalosis on airway vascular smooth muscle responsiveness to albuterol.

PubMed

Cancado, Jose E; Mendes, Eliana S; Arana, Johana; Horvath, Gabor; Monzon, Maria E; Salathe, Matthias; Wanner, Adam

2015-04-02

In vitro and animal experiments have shown that the transport and signaling of β2-adrenergic agonists are pH-sensitive. Inhaled albuterol, a hydrophilic β2-adrenergic agonist, is widely used for the treatment of obstructive airway diseases. Acute exacerbations of obstructive airway diseases can be associated with changes in ventilation leading to either respiratory acidosis or alkalosis thereby affecting albuterol responsiveness in the airway. The purpose of this study was to determine if airway pH has an effect on albuterol-induced vasodilation in the airway. Ten healthy volunteers performed the following respiratory maneuvers: quiet breathing, hypocapnic hyperventilation, hypercapnic hyperventilation, and eucapnic hyperventilation (to dissociate the effect of pH from the effect of ventilation). During these breathing maneuvers, exhaled breath condensate (EBC) pH and airway blood flow response to inhaled albuterol (ΔQ̇aw) were assessed. Mean ± SE EBC pH (units) and ΔQ̇aw (μl.min(-1).mL(-1)) were 6.4 ± 0.1 and 16.8 ± 1.9 during quiet breathing, 6.3 ± 0.1 and 14.5 ± 2.4 during eucapnic hyperventilation, 6.6 ± 0.2 and -0.2 ± 1.8 during hypocapnic hyperventilation (p = 0.02 and <0.01 vs. quiet breathing), and 5.9 ± 0.1 and 2.0 ± 1.5 during hypercapnic hyperventilation (p = 0.02 and <0.02 vs quiet breathing). Albuterol responsiveness in the airway as assessed by ΔQ̇aw is pH sensitive. The breathing maneuver associated with decreased and increased EBC pH both resulted in a decreased responsiveness independent of the level of ventilation. These findings suggest an attenuated response to hydrophilic β2-adrenergic agonists during airway disease exacerbations associated with changes in pH. Registered at clinicaltrials.gov: NCT01216748 .

Role for ion transport in porcine vocal fold epithelial defense to acid challenge.

PubMed

Erickson-Levendoski, Elizabeth; Sivasankar, M Preeti

2012-02-01

The vocal fold epithelium is routinely exposed to gastric contents, including acid and pepsin, during laryngopharyngeal reflux events. The epithelium may possess intrinsic defenses to reflux. The first objective of the current study was to examine whether vocal fold epithelial ion transport is one potential mechanism of defense to gastric contents. The second objective was to determine whether ion transport in response to gastric contents is associated with the secretion of bicarbonate. Prospective design in excised porcine larynges. Laboratory. Porcine vocal folds (N = 56) were exposed on the luminal surface to acid, pepsin, or sham challenges. Ion transport at baseline and following challenge exposure was measured using electrophysiological techniques. To examine specific ion transport mechanisms, vocal folds were pretreated with either a sodium channel blocker or bicarbonate channel blocker. Within 60 seconds of acid but not pepsin exposure, there was a significant increase in ion transport. This rapid increase in ion transport was transient and related to bicarbonate secretion. The current data suggest that porcine vocal folds immediately increase bicarbonate secretion following exposure to acid. Bicarbonate secretion may act to neutralize acid. These findings contribute to the identification of the mechanisms underlying vocal fold defense to reflux and offer implications for the development of treatments for reflux-induced vocal fold injury.

Transport of secondary electrons and reactive species in ion tracks

NASA Astrophysics Data System (ADS)

Surdutovich, Eugene; Solov'yov, Andrey V.

2015-08-01

The transport of reactive species brought about by ions traversing tissue-like medium is analysed analytically. Secondary electrons ejected by ions are capable of ionizing other molecules; the transport of these generations of electrons is studied using the random walk approximation until these electrons remain ballistic. Then, the distribution of solvated electrons produced as a result of interaction of low-energy electrons with water molecules is obtained. The radial distribution of energy loss by ions and secondary electrons to the medium yields the initial radial dose distribution, which can be used as initial conditions for the predicted shock waves. The formation, diffusion, and chemical evolution of hydroxyl radicals in liquid water are studied as well. COST Action Nano-IBCT: Nano-scale Processes Behind Ion-Beam Cancer Therapy.

Ion transport restriction in mechanically strained separator membranes

NASA Astrophysics Data System (ADS)

Cannarella, John; Arnold, Craig B.

2013-03-01

We use AC impedance methods to investigate the effect of mechanical deformation on ion transport in commercial separator membranes and lithium-ion cells as a whole. A Bruggeman type power law relationship is found to provide an accurate correlation between porosity and tortuosity of deformed separators, which allows the impedance of a separator membrane to be predicted as a function of deformation. By using mechanical compression to vary the porosity of the separator membranes during impedance measurements it is possible to determine both the α and γ parameters from the modified Bruggeman relation for individual separator membranes. From impedance testing of compressed pouch cells it is found that separator deformation accounts for the majority of the transport restrictions arising from compressive stress in a lithium-ion cell. Finally, a charge state dependent increase in the impedance associated with charge transfer is observed with increasing cell compression.

Ion heat transport in improved confinement MST plasmas

NASA Astrophysics Data System (ADS)

Xing, Zichuan; Nornberg, Mark; den Hartog, Daniel J.; Kumar, Santhosh; Anderson, Jay K.

2016-10-01

Ion power balance in improved confinement (PPCD) plasmas in MST is dominated by electron collisional heating balanced by charge exchange transport. Neoclassical effects on ions in the RFP are inherently small and PPCD plasmas have reduced turbulence and stochasticity. Thus PPCD plasmas provide a good starting point for a transport model developed to account for collisional equilibration between species, classical conductive energy transport, and energy loss due to charge exchange collisions. This model also allows a possible noncollisional anomalous term to be isolated for study, and correlations between residual magnetic fluctuations during PPCD plasmas and anomalous heating and transport will be investigated. Recent modeling with DEGAS2 Monte Carlo neutral simulation suggests higher core neutral temperature than previously estimated with more simplistic assumptions. However, the working model does not fully account for the electron density increase in the core during PPCD, which is higher than expected from classical particle transport, and neutral and impurity ionization. Other possible mechanisms are considered and analyzed, including more complex impurity charge-state balance and pinch effects. Work supported by the US DOE. DEGAS2 is provided by PPPL.

Benchmarking of neutron production of heavy-ion transport codes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Remec, I.; Ronningen, R. M.; Heilbronn, L.

Document available in abstract form only, full text of document follows: Accurate prediction of radiation fields generated by heavy ion interactions is important in medical applications, space missions, and in design and operation of rare isotope research facilities. In recent years, several well-established computer codes in widespread use for particle and radiation transport calculations have been equipped with the capability to simulate heavy ion transport and interactions. To assess and validate these capabilities, we performed simulations of a series of benchmark-quality heavy ion experiments with the computer codes FLUKA, MARS15, MCNPX, and PHITS. We focus on the comparisons of secondarymore » neutron production. Results are encouraging; however, further improvements in models and codes and additional benchmarking are required. (authors)« less

AMP-activated protein kinase (AMPK)-dependent and -independent pathways regulate hypoxic inhibition of transepithelial Na+ transport across human airway epithelial cells.

PubMed

Tan, C D; Smolenski, R T; Harhun, M I; Patel, H K; Ahmed, S G; Wanisch, K; Yáñez-Muñoz, R J; Baines, D L

2012-09-01

Pulmonary transepithelial Na(+) transport is reduced by hypoxia, but in the airway the regulatory mechanisms remain unclear. We investigated the role of AMPK and ROS in the hypoxic regulation of apical amiloride-sensitive Na(+) channels and basolateral Na(+) K(+) ATPase activity. H441 human airway epithelial cells were used to examine the effects of hypoxia on Na(+) transport, AMP : ATP ratio and AMPK activity. Lentiviral constructs were used to modify cellular AMPK abundance and activity; pharmacological agents were used to modify cellular ROS. AMPK was activated by exposure to 3% or 0.2% O(2) for 60 min in cells grown in submerged culture or when fluid (0.1 mL·cm(-2) ) was added to the apical surface of cells grown at the air-liquid interface. Only 0.2% O(2) activated AMPK in cells grown at the air-liquid interface. AMPK activation was associated with elevation of cellular AMP:ATP ratio and activity of the upstream kinase LKB1. Hypoxia inhibited basolateral ouabain-sensitive I(sc) (I(ouabain) ) and apical amiloride-sensitive Na(+) conductance (G(Na+) ). Modification of AMPK activity prevented the effect of hypoxia on I(ouabain) (Na(+) K(+) ATPase) but not apical G(Na+) . Scavenging of superoxide and inhibition of NADPH oxidase prevented the effect of hypoxia on apical G(Na+) (epithelial Na(+) channels). Hypoxia activates AMPK-dependent and -independent pathways in airway epithelial cells. Importantly, these pathways differentially regulate apical Na(+) channels and basolateral Na(+) K(+) ATPase activity to decrease transepithelial Na(+) transport. Luminal fluid potentiated the effect of hypoxia and activated AMPK, which could have important consequences in lung disease conditions. © 2012 The Authors. British Journal of Pharmacology © 2012 The British Pharmacological Society.

New Insights into the Compositional Dependence of Li-Ion Transport in Polymer-Ceramic Composite Electrolytes.

PubMed

Zheng, Jin; Hu, Yan-Yan

2018-01-31

Composite electrolytes are widely studied for their potential in realizing improved ionic conductivity and electrochemical stability. Understanding the complex mechanisms of ion transport within composites is critical for effectively designing high-performance solid electrolytes. This study examines the compositional dependence of the three determining factors for ionic conductivity, including ion mobility, ion transport pathways, and active ion concentration. The results show that with increase in the fraction of ceramic Li 7 La 3 Zr 2 O 12 (LLZO) phase in the LLZO-poly(ethylene oxide) composites, ion mobility decreases, ion transport pathways transit from polymer to ceramic routes, and the active ion concentration increases. These changes in ion mobility, transport pathways, and concentration collectively explain the observed trend of ionic conductivity in composite electrolytes. Liquid additives alter ion transport pathways and increase ion mobility, thus enhancing ionic conductivity significantly. It is also found that a higher content of LLZO leads to improved electrochemical stability of composite electrolytes. This study provides insight into the recurring observations of compositional dependence of ionic conductivity in current composite electrolytes and pinpoints the intrinsic limitations of composite electrolytes in achieving fast ion conduction.

Phenomenology of anomalous chiral transports in heavy-ion collisions

NASA Astrophysics Data System (ADS)

Huang, Xu-Guang

2018-01-01

High-energy Heavy-ion collisions can generate extremely hot quark-gluon matter and also extremely strong magnetic fields and fluid vorticity. Once coupled to chiral anomaly, the magnetic fields and fluid vorticity can induce a variety of novel transport phenomena, including the chiral magnetic effect, chiral vortical effect, etc. Some of them require the environmental violation of parity and thus provide a means to test the possible parity violation in hot strongly interacting matter. We will discuss the underlying mechanism and implications of these anomalous chiral transports in heavy-ion collisions.

Unraveling the mechanism of selective ion transport in hydrophobic subnanometer channels

PubMed Central

Li, Hui; Francisco, Joseph S.; Zeng, Xiao Cheng

2015-01-01

Recently reported synthetic organic nanopore (SONP) can mimic a key feature of natural ion channels, i.e., selective ion transport. However, the physical mechanism underlying the K+/Na+ selectivity for the SONPs is dramatically different from that of natural ion channels. To achieve a better understanding of the selective ion transport in hydrophobic subnanometer channels in general and SONPs in particular, we perform a series of ab initio molecular dynamics simulations to investigate the diffusivity of aqua Na+ and K+ ions in two prototype hydrophobic nanochannels: (i) an SONP with radius of 3.2 Å, and (ii) single-walled carbon nanotubes (CNTs) with radii of 3–5 Å (these radii are comparable to those of the biological potassium K+ channels). We find that the hydration shell of aqua Na+ ion is smaller than that of aqua K+ ion but notably more structured and less yielding. The aqua ions do not lower the diffusivity of water molecules in CNTs, but in SONP the diffusivity of aqua ions (Na+ in particular) is strongly suppressed due to the rugged inner surface. Moreover, the aqua Na+ ion requires higher formation energy than aqua K+ ion in the hydrophobic nanochannels. As such, we find that the ion (K+ vs. Na+) selectivity of the (8, 8) CNT is ∼20× higher than that of SONP. Hence, the (8, 8) CNT is likely the most efficient artificial K+ channel due in part to its special interior environment in which Na+ can be fully solvated, whereas K+ cannot. This work provides deeper insights into the physical chemistry behind selective ion transport in nanochannels. PMID:26283377

Unraveling the mechanism of selective ion transport in hydrophobic subnanometer channels.

PubMed

Li, Hui; Francisco, Joseph S; Zeng, Xiao Cheng

2015-09-01

Recently reported synthetic organic nanopore (SONP) can mimic a key feature of natural ion channels, i.e., selective ion transport. However, the physical mechanism underlying the K(+)/Na(+) selectivity for the SONPs is dramatically different from that of natural ion channels. To achieve a better understanding of the selective ion transport in hydrophobic subnanometer channels in general and SONPs in particular, we perform a series of ab initio molecular dynamics simulations to investigate the diffusivity of aqua Na(+) and K(+) ions in two prototype hydrophobic nanochannels: (i) an SONP with radius of 3.2 Å, and (ii) single-walled carbon nanotubes (CNTs) with radii of 3-5 Å (these radii are comparable to those of the biological potassium K(+) channels). We find that the hydration shell of aqua Na(+) ion is smaller than that of aqua K(+) ion but notably more structured and less yielding. The aqua ions do not lower the diffusivity of water molecules in CNTs, but in SONP the diffusivity of aqua ions (Na(+) in particular) is strongly suppressed due to the rugged inner surface. Moreover, the aqua Na(+) ion requires higher formation energy than aqua K(+) ion in the hydrophobic nanochannels. As such, we find that the ion (K(+) vs. Na(+)) selectivity of the (8, 8) CNT is ∼20× higher than that of SONP. Hence, the (8, 8) CNT is likely the most efficient artificial K(+) channel due in part to its special interior environment in which Na(+) can be fully solvated, whereas K(+) cannot. This work provides deeper insights into the physical chemistry behind selective ion transport in nanochannels.

Influence of inhalation anesthetics on ion transport across a planar bilayer lipid membrane.

PubMed

Hichiri, Kei; Shirai, Osamu; Kano, Kenji

2012-01-01

Ion transport from one aqueous phase (W1) to another (W2) across a planar bilayer lipid membrane (BLM) in the presence of inhalation anesthetics was electrochemically investigated. In the absence of inhalation anesthetics in the BLM system, no ion transport current flowed between W1 and W2 across the BLM. When inhalation anesthetics such as halothane, chloroform, diethyl ether and trichloroethylene were added to the two aqueous phases or the BLM, the ion transport current quite clearly appeared. When the ratio of the concentration of KCl or NaCl in W1 to that in W2 was varied, the zero current potential across the BLM was shifted. By considering the magnitude of the potential shift, we concluded that the ion transport current can be predominantly ascribed to the transport of Cl(-) across the BLM. Since the dielectric constants of these anesthetics are larger than that of the inner hydrophobic domain of the BLM, the concentration of hydrophilic electrolyte ions in the BLM increases with the increase in the dielectric constant of the inner hydrophobic domain caused by addition of these anesthetics. These situations lead to an increase in the ion permeability coefficient.

77 FR 59391 - Delta Air Lines, Inc., Continental Airlines, Inc., JetBlue Airways Corporation, United Air Lines...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-09-27

... lawfulness of the rates charged by the Respondent for transportation of jet or aviation turbine fuel on its..., Inc., Continental Airlines, Inc., JetBlue Airways Corporation, United Air Lines, Inc., US Airways, Inc... Airlines, Inc., JetBlue Airways Corporation, United Air Lines, Inc., and US Airways, Inc. (collectively...

Transportation behavior of alkali ions through a cell membrane ion channel. A quantum chemical description of a simplified isolated model.

PubMed

Billes, Ferenc; Mohammed-Ziegler, Ildikó; Mikosch, Hans

2012-08-01

Quantum chemical model calculations were carried out for modeling the ion transport through an isolated ion channel of a cell membrane. An isolated part of a natural ion channel was modeled. The model channel was a calixarene derivative, hydrated sodium and potassium ions were the models of the transported ion. The electrostatic potential of the channel and the energy of the channel-ion system were calculated as a function of the alkali ion position. Both attractive and repulsive ion-channel interactions were found. The calculations - namely the dependence of the system energy and the atomic charges of the water molecules with respect to the position of the alkali ion in the channel - revealed the molecular-structural background of the potassium selectivity of this artificial ion channel. It was concluded that the studied ion channel mimics real biological ion channel quite well.

Thermal plasma and fast ion transport in electrostatic turbulence in the large plasma devicea)

NASA Astrophysics Data System (ADS)

Zhou, Shu; Heidbrink, W. W.; Boehmer, H.; McWilliams, R.; Carter, T. A.; Vincena, S.; Tripathi, S. K. P.; Van Compernolle, B.

2012-05-01

The transport of thermal plasma and fast ions in electrostatic microturbulence is studied. Strong density and potential fluctuations (δn /n˜δφ/kTe ˜ 0.5, f ˜ 5-50 kHz) are observed in the large plasma device (LAPD) [W. Gekelman, H. Pfister, Z. Lucky et al., Rev. Sci. Instrum. 62, 2875 (1991)] in density gradient regions produced by obstacles with slab or cylindrical geometry. Wave characteristics and the associated plasma transport are modified by driving sheared E × B drift through biasing the obstacle and by modification of the axial magnetic fields (Bz) and the plasma species. Cross-field plasma transport is suppressed with small bias and large Bz and is enhanced with large bias and small Bz. The transition in thermal plasma confinement is well explained by the cross-phase between density and potential fluctuations. Large gyroradius lithium fast ion beam (ρfast/ρs ˜ 10) orbits through the turbulent region. Scans with a collimated analyzer give detailed profiles of the fast ion spatial-temporal distribution. Fast-ion transport decreases rapidly with increasing fast-ion energy and gyroradius. Background waves with different scale lengths also alter the fast ion transport. Experimental results agree well with gyro-averaging theory. When the fast ion interacts with the wave for most of a wave period, a transition from super-diffusive to sub-diffusive transport is observed, as predicted by diffusion theory. Besides turbulent-wave-induced fast-ion transport, the static radial electric field (Er) from biasing the obstacle leads to drift of the fast-ion beam centroid. The drift and broadening of the beam due to static Er are evaluated both analytically and numerically. Simulation results indicate that the Er induced transport is predominately convective.

Characterization of Rat Meibomian Gland Ion and Fluid Transport

PubMed Central

Yu, Dongfang; Davis, Richard M.; Aita, Megumi; Burns, Kimberlie A.; Clapp, Phillip W.; Gilmore, Rodney C.; Chua, Michael; O'Neal, Wanda K.; Schlegel, Richard; Randell, Scott H.; C. Boucher, Richard

2016-01-01

Purpose We establish novel primary rat meibomian gland (MG) cell culture systems and explore the ion transport activities of the rat MG. Methods Freshly excised rat MG tissues were characterized as follows: (1) mRNA expression of selected epithelial ion channels/transporters were measured by RT-PCR, (2) localization of epithelial sodium channel (ENaC) mRNAs was performed by in situ hybridization, and (3) protein expression and localization of βENaC, the Na+/K+/Cl− cotransporter (NKCC), and the Na+/K+ ATPase were evaluated by immunofluorescence. Primary isolated rat MG cells were cocultured with 3T3 feeder cells and a Rho-associated kinase (ROCK) inhibitor (Y-27632) for expansion. Passaged rat MG cells were cultured as planar sheets under air-liquid interface (ALI) conditions for gene expression and electrophysiologic studies. Passaged rat MG cells also were cultured in matrigel matrices to form spheroids, which were examined ultrastructurally by transmission electron microscopy (TEM) and functionally using swelling assays. Results Expression of multiple ion channel/transporter genes was detected in rat MG tissues. β-ENaC mRNA and protein were localized more to MG peripheral acinar cells than central acinar cells or ductular epithelial cells. Electrophysiologic studies of rat MG cell planar cultures demonstrated functional sodium, chloride, and potassium channels, and cotransporters activities. Transmission electron microscopic analyses of rat MG spheroids revealed highly differentiated MG cells with abundant lysosomal lamellar bodies. Rat MG spheroids culture-based measurements demonstrated active volume regulation by ion channels. Conclusions This study demonstrates the presence and function of ion channels and volume transport by rat MG. Two novel primary MG cell culture models that may be useful for MG research were established. PMID:27127933

Membrane ion transport in non-excitable tissues.

PubMed Central

Nehrke, Keith

2014-01-01

The facilitated movement of ions across cell membranes can be characterized as occurring through active (ATP-dependent), secondary active (coupled), or passive transport processes. Each of these processes is mediated by a diverse group of membrane proteins. Over the past fifteen years, studies of membrane transport in C. elegans have benefited from the fact that worms are anatomically simple, easily and economically cultured, and genetically tractable. These experimental advantages have been instrumental in defining how membrane transport processes contribute to whole organism physiology. The focus of this review is to survey the recent advances in our understanding of membrane transport that have arisen from integrative physiological approaches in the nematode C. elegans. PMID:25536490

Microsecond Simulations of DNA and Ion Transport in Nanopores with Novel Ion-Ion and Ion-Nucleotides Effective Potentials

PubMed Central

De Biase, Pablo M.; Markosyan, Suren; Noskov, Sergei

2014-01-01

We developed a novel scheme based on the Grand-Canonical Monte-Carlo/Brownian Dynamics (GCMC/BD) simulations and have extended it to studies of ion currents across three nanopores with the potential for ssDNA sequencing: solid-state nanopore Si3N4, α-hemolysin, and E111N/M113Y/K147N mutant. To describe nucleotide-specific ion dynamics compatible with ssDNA coarse-grained model, we used the Inverse Monte-Carlo protocol, which maps the relevant ion-nucleotide distribution functions from an all-atom MD simulations. Combined with the previously developed simulation platform for Brownian Dynamic (BD) simulations of ion transport, it allows for microsecond- and millisecond-long simulations of ssDNA dynamics in nanopore with a conductance computation accuracy that equals or exceeds that of all-atom MD simulations. In spite of the simplifications, the protocol produces results that agree with the results of previous studies on ion conductance across open channels and provide direct correlations with experimentally measured blockade currents and ion conductances that have been estimated from all-atom MD simulations. PMID:24738152

Role for Ion Transport in Porcine Vocal Fold Epithelial Defense to Acid Challenge

PubMed Central

Erickson-Levendoski, Elizabeth; Sivasankar, M. Preeti

2012-01-01

Objective The vocal fold epithelium is routinely exposed to gastric contents, including acid and pepsin, during laryngopharyngeal reflux events. The epithelium may possess intrinsic defenses to reflux. The first objective of the current study was to examine whether vocal fold epithelial ion transport is one potential mechanism of defense to gastric contents. The second objective was to determine whether ion transport in response to gastric contents is associated with the secretion of bicarbonate. Study Design Prospective design in excised porcine larynges. Setting Laboratory. Subjects and Methods Porcine vocal folds (N = 56) were exposed on the luminal surface to acid, pepsin, or sham challenges. Ion transport at baseline and following challenge exposure was measured using electrophysiological techniques. To examine specific ion transport mechanisms, vocal folds were pretreated with either a sodium channel blocker or bicarbonate channel blocker. Results Within 60 seconds of acid but not pepsin exposure, there was a significant increase in ion transport. This rapid increase in ion transport was transient and related to bicarbonate secretion. Conclusion The current data suggest that porcine vocal folds immediately increase bicarbonate secretion following exposure to acid. Bicarbonate secretion may act to neutralize acid. These findings contribute to the identification of the mechanisms underlying vocal fold defense to reflux and offer implications for the development of treatments for reflux-induced vocal fold injury. PMID:22086905

Light-induced modification of plant plasma membrane ion transport.

PubMed

Marten, I; Deeken, R; Hedrich, R; Roelfsema, M R G

2010-09-01

Light is not only the driving force for electron and ion transport in the thylakoid membrane, but also regulates ion transport in various other membranes of plant cells. Light-dependent changes in ion transport at the plasma membrane and associated membrane potential changes have been studied intensively over the last century. These studies, with various species and cell types, revealed that apart from regulation by chloroplasts, plasma membrane transport can be controlled by phytochromes, phototropins or channel rhodopsins. In this review, we compare light-dependent plasma membrane responses of unicellular algae (Eremosphaera and Chlamydomonas), with those of a multicellular alga (Chara), liverworts (Conocephalum), mosses (Physcomitrella) and several angiosperm cell types. Light-dependent plasma membrane responses of Eremosphaera and Chara are characterised by the dominant role of K(+) channels during membrane potential changes. In most other species, the Ca(2+)-dependent activation of plasma membrane anion channels represents a general light-triggered event. Cell type-specific responses are likely to have evolved by modification of this general response or through the development of additional light-dependent signalling pathways. Future research to elucidate these light-activated signalling chains is likely to benefit from the recent identification of S-type anion channel genes and proteins capable of regulating these channels.

Ionotropic and metabotropic receptor mediated airway sensory nerve activation.

PubMed

Lee, Min-Goo; Kollarik, Marian; Chuaychoo, Benjamas; Undem, Bradley J

2004-01-01

There are several receptors capable of inducing activating generator potentials in cough-associated afferent terminals in the airways. The chemical receptors leading to generator potentials can be subclassified into ionotropic and metabotropic types. An ionotropic receptor has an agonist-binding domain, and also serves directly as an ion channel that is opened upon binding of the agonist. Examples of ionotropic receptors found in airway sensory nerve terminals include receptors for serotonin (5-HT3 receptors), ATP (P2X receptors), acetylcholine (nicotinic receptors), receptors for capsaicin and related vanilloids (TRPV1 receptors), and acid receptors (acid sensing ion channels). Afferent nerve terminals can also be depolarized via activation of metabotropic or G-protein coupled receptors (GPCRs). Among the GPCRs that can lead to activation of airway afferent fibers include bradykinin B2 and adenosine A1 receptors. The signaling events leading to GPCR-mediated membrane depolarization are more complex than that seen with ionotropic receptors. The GPCR-mediated effects are thought to occur through classical second messenger systems such as activation of phospholipase C. This may lead to membrane depolarization through interaction with specific ionotropic receptors (such as TRPV1) and/or various types of calcium activated channels.

Transport implementation of the Bernstein-Vazirani algorithm with ion qubits

NASA Astrophysics Data System (ADS)

Fallek, S. D.; Herold, C. D.; McMahon, B. J.; Maller, K. M.; Brown, K. R.; Amini, J. M.

2016-08-01

Using trapped ion quantum bits in a scalable microfabricated surface trap, we perform the Bernstein-Vazirani algorithm. Our architecture takes advantage of the ion transport capabilities of such a trap. The algorithm is demonstrated using two- and three-ion chains. For three ions, an improvement is achieved compared to a classical system using the same number of oracle queries. For two ions and one query, we correctly determine an unknown bit string with probability 97.6(8)%. For three ions, we succeed with probability 80.9(3)%.

Mechanosensitive ATP Release Maintains Proper Mucus Hydration of Airways

PubMed Central

Button, Brian; Okada, Seiko F.; Frederick, Charles Brandon; Thelin, William R.; Boucher, Richard C.

2013-01-01

The clearance of mucus from the airways protects the lungs from inhaled noxious and infectious materials. Proper hydration of the mucus layer enables efficient mucus clearance through beating of cilia on airway epithelial cells, and reduced clearance of excessively concentrated mucus occurs in patients with chronic obstructive pulmonary disease and cystic fibrosis. Key steps in the mucus transport process are airway epithelia sensing and responding to changes in mucus hydration. We reported that extracellular adenosine triphosphate (ATP) and adenosine were important luminal auto-crine and paracrine signals that regulated the hydration of the surface of human airway epithelial cultures through their action on apical membrane purinoceptors. Mucus hydration in human airway epithelial cultures was sensed by an interaction between cilia and the overlying mucus layer: Changes in mechanical strain, proportional to mucus hydration, regulated ATP release rates, adjusting fluid secretion to optimize mucus layer hydration. This system provided a feedback mechanism by which airways maintained mucus hydration in an optimum range for cilia propulsion. Understanding how airway epithelia can sense and respond to changes in mucus properties helps us to understand how the mucus clearance system protects the airways in health and how it fails in lung diseases such as cystic fibrosis. PMID:23757023

Stormtime transport of ring current and radiation belt ions

NASA Technical Reports Server (NTRS)

Chen, Margaret W.; Schulz, Michael; Lyons, L. R.; Gorney, David J.

1993-01-01

This is an investigation of stormtime particle transport that leads to formation of the ring current. Our method is to trace the guiding-center motion of representative ions (having selected first adiabatic invariants mu) in response to model substorm-associated impulses in the convection electric field. We compare our simulation results qualitatively with existing analytically tractable idealizations of particle transport (direct convective access and radial diffusion) in order to assess the limits of validity of these approximations. For mu approximately less than 10 MeV/G (E approximately less than 10 keV at L equivalent to 3) the ion drift period on the final (ring-current) drift shell of interest (L equivalent to 3) exceeds the duration of the main phase of our model storm, and we find that the transport of ions to this drift shell is appropriately idealized as direct convective access, typically from open drift paths. Ion transport to a final closed drift path from an open (plasma-sheet) drift trajectory is possible for those portions of that drift path that lie outside the mean stormtime separatrix between closed and open drift trajectories, For mu approximately 10-25 MeV/G (110 keV approximately less than E approximately less than 280 keV at L equivalent to 3) the drift period at L equivalent to 3 is comparable to the postulated 3-hr duration of the storm, and the mode of transport is transitional between direct convective access and transport that resembles radial diffusion. (This particle population is transitional between the ring current and radiation belt). For mu approximately greater than 25 MeV/G (radiation-belt ions having E approximately greater than 280 keV at L equivalent to 3) the ion drift period is considerably shorter than the main phase of a typical storm, and ions gain access to the ring-current region essentially via radial diffusion. By computing the mean and mean-square cumulative changes in 1/L among (in this case) 12 representative

Functional characterization of the organic cation transporters (OCTs) in human airway pulmonary epithelial cells.

PubMed

Ingoglia, Filippo; Visigalli, Rossana; Rotoli, Bianca Maria; Barilli, Amelia; Riccardi, Benedetta; Puccini, Paola; Dall'Asta, Valeria

2015-07-01

Organic cation transporters (OCT1-3) mediate the transport of organic cations including inhaled drugs across the cell membrane, although their role in lung epithelium hasn't been well understood yet. We address here the expression and functional activity of OCT1-3 in human airway epithelial cells A549, Calu-3 and NCl-H441. Kinetic and inhibition analyses, employing [(3)H]1-methyl-4-phenylpyridinium (MPP+) as substrate, and the compounds quinidine, prostaglandine E2 (PGE2) and corticosterone as preferential inhibitors of OCT1, OCT2, and OCT3, respectively, have been performed. A549 cells present a robust MPP+ uptake mediated by one high-affinity component (Km~50μM) which is identifiable with OCT3. Corticosterone, indeed, completely inhibits MPP+ transport, while quinidine and PGE2 are inactive and SLC22A3/OCT3 silencing with siRNA markedly lowers MPP+ uptake. Conversely, Calu-3 exhibits both a high (Km<20μM) and a low affinity (Km>0.6mM) transport components, referable to OCT3 and OCT1, respectively, as demonstrated by the inhibition analysis performed at proper substrate concentrations and confirmed by the use of specific siRNA. These transporters are active also when cells are grown under air-liquid interface (ALI) conditions. Only a very modest saturable MPP+ uptake is measurable in NCl-H441 cells and the inhibitory effect of quinidine points to OCT1 as the subtype functionally involved in this model. Finally, the characterization of MPP+ transport in human bronchial BEAS-2B cells suggests that OCT1 and OCT3 are operative. These findings could help to identify in vitro models to be employed for studies concerning the specific involvement of each transporter in drug transportation. Copyright © 2015 Elsevier B.V. All rights reserved.

Ultrafast selective transport of alkali metal ions in metal organic frameworks with subnanometer pores

PubMed Central

Zhang, Huacheng; Hou, Jue; Hu, Yaoxin; Wang, Peiyao; Ou, Ranwen; Jiang, Lei; Liu, Jefferson Zhe; Freeman, Benny D.; Hill, Anita J.; Wang, Huanting

2018-01-01

Porous membranes with ultrafast ion permeation and high ion selectivity are highly desirable for efficient mineral separation, water purification, and energy conversion, but it is still a huge challenge to efficiently separate monatomic ions of the same valence and similar sizes using synthetic membranes. We report metal organic framework (MOF) membranes, including ZIF-8 and UiO-66 membranes with uniform subnanometer pores consisting of angstrom-sized windows and nanometer-sized cavities for ultrafast selective transport of alkali metal ions. The angstrom-sized windows acted as ion selectivity filters for selection of alkali metal ions, whereas the nanometer-sized cavities functioned as ion conductive pores for ultrafast ion transport. The ZIF-8 and UiO-66 membranes showed a LiCl/RbCl selectivity of ~4.6 and ~1.8, respectively, which are much greater than the LiCl/RbCl selectivity of 0.6 to 0.8 measured in traditional porous membranes. Molecular dynamics simulations suggested that ultrafast and selective ion transport in ZIF-8 was associated with partial dehydration effects. This study reveals ultrafast and selective transport of monovalent ions in subnanometer MOF pores and opens up a new avenue to develop unique MOF platforms for efficient ion separations in the future. PMID:29487910

Ultrafast selective transport of alkali metal ions in metal organic frameworks with subnanometer pores.

PubMed

Zhang, Huacheng; Hou, Jue; Hu, Yaoxin; Wang, Peiyao; Ou, Ranwen; Jiang, Lei; Liu, Jefferson Zhe; Freeman, Benny D; Hill, Anita J; Wang, Huanting

2018-02-01

Porous membranes with ultrafast ion permeation and high ion selectivity are highly desirable for efficient mineral separation, water purification, and energy conversion, but it is still a huge challenge to efficiently separate monatomic ions of the same valence and similar sizes using synthetic membranes. We report metal organic framework (MOF) membranes, including ZIF-8 and UiO-66 membranes with uniform subnanometer pores consisting of angstrom-sized windows and nanometer-sized cavities for ultrafast selective transport of alkali metal ions. The angstrom-sized windows acted as ion selectivity filters for selection of alkali metal ions, whereas the nanometer-sized cavities functioned as ion conductive pores for ultrafast ion transport. The ZIF-8 and UiO-66 membranes showed a LiCl/RbCl selectivity of ~4.6 and ~1.8, respectively, which are much greater than the LiCl/RbCl selectivity of 0.6 to 0.8 measured in traditional porous membranes. Molecular dynamics simulations suggested that ultrafast and selective ion transport in ZIF-8 was associated with partial dehydration effects. This study reveals ultrafast and selective transport of monovalent ions in subnanometer MOF pores and opens up a new avenue to develop unique MOF platforms for efficient ion separations in the future.

Passive continuous positive airway pressure ventilation during cardiopulmonary resuscitation: a randomized cross-over manikin simulation study.

PubMed

Winkler, Bernd E; Muellenbach, Ralf M; Wurmb, Thomas; Struck, Manuel F; Roewer, Norbert; Kranke, Peter

2017-02-01

While controlled ventilation is most frequently used during cardiopulmonary resuscitation (CPR), the application of continuous positive airway pressure (CPAP) and passive ventilation of the lung synchronously with chest compressions and decompressions might represent a promising alternative approach. One benefit of CPAP during CPR is the reduction of peak airway pressures and therefore a potential enhancement in haemodynamics. We therefore evaluated the tidal volumes and airway pressures achieved during CPAP-CPR. During CPR with the LUCAS™ 2 compression device, a manikin model was passively ventilated at CPAP levels of 5, 10, 20 and 30 hPa with the Boussignac tracheal tube and the ventilators Evita ® V500, Medumat ® Transport, Oxylator ® EMX, Oxylog ® 2000, Oxylog ® 3000, Primus ® and Servo ® -i as well as the Wenoll ® diver rescue system. Tidal volumes and airway pressures during CPAP-CPR were recorded and analyzed. Tidal volumes during CPAP-CPR were higher than during compression-only CPR without positive airway pressure. The passively generated tidal volumes increased with increasing CPAP levels and were significantly influenced by the ventilators used. During ventilation at 20 hPa CPAP via a tracheal tube, the mean tidal volumes ranged from 125 ml (Medumat ® ) to 309 ml (Wenoll ® ) and the peak airway pressures from 23 hPa (Primus ® ) to 49 hPa (Oxylog ® 3000). Transport ventilators generated lower tidal volumes than intensive care ventilators or closed-circuit systems. Peak airway pressures during CPAP-CPR were lower than those during controlled ventilation CPR reported in literature. High peak airway pressures are known to limit the applicability of ventilation via facemask or via supraglottic airway devices and may adversely affect haemodynamics. Hence, the application of ventilators generating high tidal volumes with low peak airway pressures appears desirable during CPAP-CPR. The limited CPAP-CPR capabilities of transport ventilators in

Decreased expression of monocarboxylate transporter 1 and 4 in the branching airway epithelium of nitrofen-induced congenital diaphragmatic hernia.

PubMed

Takahashi, Toshiaki; Friedmacher, Florian; Zimmer, Julia; Puri, Prem

2016-06-01

Monocarboxylate transporters (MCTs) are crucial for the maintenance of intracellular pH homeostasis in developing fetal lungs. MCT1/4 is strongly expressed by epithelial airway cells throughout lung branching morphogenesis. Functional inhibition of MCT1/4 in fetal rat lung explants has been shown to result in airway defects similar to pulmonary hypoplasia (PH) in congenital diaphragmatic hernia (CDH). We hypothesized that pulmonary expression of MCT1/4 is decreased during lung branching morphogenesis in the nitrofen model of CDH-associated PH. Timed-pregnant rats received nitrofen or vehicle on gestational day 9 (D9). Fetuses were harvested on D15, D18, and D21, and divided into control and nitrofen-exposed group. Pulmonary gene expression levels of MCT1/4 were analyzed by qRT-PCR. Immunofluorescence staining for MCT1/4 was combined with E-cadherin in order to evaluate protein expression in branching airway tissue. Relative mRNA levels of MCT1/4 were significantly reduced in lungs of nitrofen-exposed fetuses on D15, D18, and D21 compared to controls. Confocal laser scanning microscopy confirmed markedly decreased immunofluorescence of MCT1/4 in distal bronchial and primitive alveolar epithelium of nitrofen-exposed fetuses on D15, D18, and D21 compared to controls. Decreased expression of MCT1/4 in distal airway epithelium may disrupt lung branching morphogenesis and thus contribute to the development of PH in the nitrofen-induced CDH model. Copyright © 2016 Elsevier Inc. All rights reserved.

Role of adrenal hormones in regulating distal nephron structure and ion transport.

PubMed

Stanton, B A

1985-08-01

Mineralocorticoid levels are an important determinant of membrane area and ion transport in the renal initial (ICT) and cortical (CCT) collecting tubules. Adrenalectomy leads to a dramatic and specific decrease in basolateral membrane area of principal (P) cells and depresses sodium reabsorption and potassium secretion. Although aldosterone replacement for 10 days restores basolateral membrane area and ATPase activity to control levels and dramatically elevates ion transport, glucocorticoids have no effect on basolateral membrane area, ion transport, or ATPase. It is suggested that the aldosterone-induced amplification of membrane area occurs as a mechanism whereby cells increase the number of ATPase pumps in the basolateral membrane. An acute (of 2-3 h) increase in aldosterone, but not dexamethasone, also stimulates potassium transport by the ICT. Future studies will have to establish whether the acute stimulation of transport by aldosterone involves a change in basolateral membrane area. It is concluded that mineralocorticoids, but not glucocorticoids, regulate sodium and potassium transport by P cells of the ICT and CCT, in part, by determining the number of ATPase pumps available for transport.

Ionizing radiation, ion transports, and radioresistance of cancer cells

PubMed Central

Huber, Stephan M.; Butz, Lena; Stegen, Benjamin; Klumpp, Dominik; Braun, Norbert; Ruth, Peter; Eckert, Franziska

2013-01-01

The standard treatment of many tumor entities comprises fractionated radiation therapy which applies ionizing radiation to the tumor-bearing target volume. Ionizing radiation causes double-strand breaks in the DNA backbone that result in cell death if the number of DNA double-strand breaks exceeds the DNA repair capacity of the tumor cell. Ionizing radiation reportedly does not only act on the DNA in the nucleus but also on the plasma membrane. In particular, ionizing radiation-induced modifications of ion channels and transporters have been reported. Importantly, these altered transports seem to contribute to the survival of the irradiated tumor cells. The present review article summarizes our current knowledge on the underlying mechanisms and introduces strategies to radiosensitize tumor cells by targeting plasma membrane ion transports. PMID:23966948

Visualization of lithium-ion transport and phase evolution within and between manganese oxide nanorods.

PubMed

Xu, Feng; Wu, Lijun; Meng, Qingping; Kaltak, Merzuk; Huang, Jianping; Durham, Jessica L; Fernandez-Serra, Marivi; Sun, Litao; Marschilok, Amy C; Takeuchi, Esther S; Takeuchi, Kenneth J; Hybertsen, Mark S; Zhu, Yimei

2017-05-24

Multiple lithium-ion transport pathways and local phase changes upon lithiation in silver hollandite are revealed via in situ microscopy including electron diffraction, imaging and spectroscopy, coupled with density functional theory and phase field calculations. We report unexpected inter-nanorod lithium-ion transport, where the reaction fronts and kinetics are maintained within the neighbouring nanorod. Notably, this is the first time-resolved visualization of lithium-ion transport within and between individual nanorods, where the impact of oxygen deficiencies is delineated. Initially, fast lithium-ion transport is observed along the long axis with small net volume change, resulting in two lithiated silver hollandite phases distinguishable by orthorhombic distortion. Subsequently, a slower reaction front is observed, with formation of polyphase lithiated silver hollandite and face-centred-cubic silver metal with substantial volume expansion. These results indicate lithium-ion transport is not confined within a single nanorod and may provide a paradigm shift for one-dimensional tunnelled materials, particularly towards achieving high-rate capability.

AMP-activated protein kinase (AMPK)–dependent and –independent pathways regulate hypoxic inhibition of transepithelial Na+ transport across human airway epithelial cells

PubMed Central

Tan, CD; Smolenski, RT; Harhun, MI; Patel, HK; Ahmed, SG; Wanisch, K; Yáñez-Muñoz, RJ; Baines, DL

2012-01-01

BACKGROUND AND PURPOSE Pulmonary transepithelial Na+ transport is reduced by hypoxia, but in the airway the regulatory mechanisms remain unclear. We investigated the role of AMPK and ROS in the hypoxic regulation of apical amiloride-sensitive Na+ channels and basolateral Na+K+ ATPase activity. EXPERIMENTAL APPROACH H441 human airway epithelial cells were used to examine the effects of hypoxia on Na+ transport, AMP : ATP ratio and AMPK activity. Lentiviral constructs were used to modify cellular AMPK abundance and activity; pharmacological agents were used to modify cellular ROS. KEY RESULTS AMPK was activated by exposure to 3% or 0.2% O2 for 60 min in cells grown in submerged culture or when fluid (0.1 mL·cm−2) was added to the apical surface of cells grown at the air–liquid interface. Only 0.2% O2 activated AMPK in cells grown at the air–liquid interface. AMPK activation was associated with elevation of cellular AMP : ATP ratio and activity of the upstream kinase LKB1. Hypoxia inhibited basolateral ouabain-sensitive Isc (Iouabain) and apical amiloride-sensitive Na+ conductance (GNa+). Modification of AMPK activity prevented the effect of hypoxia on Iouabain (Na+K+ ATPase) but not apical GNa+. Scavenging of superoxide and inhibition of NADPH oxidase prevented the effect of hypoxia on apical GNa+ (epithelial Na+ channels). CONCLUSIONS AND IMPLICATIONS Hypoxia activates AMPK-dependent and -independent pathways in airway epithelial cells. Importantly, these pathways differentially regulate apical Na+ channels and basolateral Na+K+ ATPase activity to decrease transepithelial Na+ transport. Luminal fluid potentiated the effect of hypoxia and activated AMPK, which could have important consequences in lung disease conditions. PMID:22509822

Observation of Critical-Gradient Behavior in Alfvén-Eigenmode-Induced Fast-Ion Transport.

PubMed

Collins, C S; Heidbrink, W W; Austin, M E; Kramer, G J; Pace, D C; Petty, C C; Stagner, L; Van Zeeland, M A; White, R B; Zhu, Y B

2016-03-04

Experiments in the DIII-D tokamak show that fast-ion transport suddenly becomes stiff above a critical threshold in the presence of many overlapping small-amplitude Alfvén eigenmodes (AEs). The threshold is phase-space dependent and occurs when particle orbits become stochastic due to resonances with AEs. Above threshold, equilibrium fast-ion density profiles are unchanged despite increased drive, and intermittent fast-ion losses are observed. Fast-ion Dα spectroscopy indicates radially localized transport of the copassing population at radii that correspond to the location of midcore AEs. The observation of stiff fast-ion transport suggests that reduced models can be used to effectively predict alpha profiles, beam ion profiles, and losses to aid in the design of optimized scenarios for future burning plasma devices.

Ion transport mechanisms in lamellar phases of salt-doped PS-PEO block copolymer electrolytes.

PubMed

Sethuraman, Vaidyanathan; Mogurampelly, Santosh; Ganesan, Venkat

2017-11-01

We use a multiscale simulation strategy to elucidate, at an atomistic level, the mechanisms underlying ion transport in the lamellar phase of polystyrene-polyethylene oxide (PS-PEO) block copolymer (BCP) electrolytes doped with LiPF 6 salts. Explicitly, we compare the results obtained for ion transport in the microphase separated block copolymer melts to those for salt-doped PEO homopolymer melts. In addition, we also present results for dynamics of the ions individually in the PEO and PS domains of the BCP melt, and locally as a function of the distance from the lamellar interfaces. When compared to the PEO homopolymer melt, ions were found to exhibit slower dynamics in both the block copolymer (overall) and in the PEO phase of the BCP melt. Such results are shown to arise from the effects of slower polymer segmental dynamics in the BCP melt and the coordination characteristics of the ions. Polymer backbone-ion residence times analyzed as a function of distance from the interface indicate that ions have a larger residence time near the interface compared to that near the bulk of lamella, and demonstrates the influence of the glassy PS blocks and microphase segregation on the ion transport properties. Ion transport mechanisms in BCP melts reveal that there exist five distinct mechanisms for ion transport along the backbone of the chain and exhibit qualitative differences from the behavior in homopolymer melts. We also present results as a function of salt concentration which show that the mean-squared displacements of the ions decrease with increasing salt concentration, and that the ion residence times near the polymer backbone increase with increasing salt concentration.

Cellular and Molecular Biology of Airway Mucins

PubMed Central

Lillehoj, Erik P.; Kato, Kosuke; Lu, Wenju; Kim, Kwang C.

2017-01-01

Airway mucus constitutes a thin layer of airway surface liquid with component macromolecules that covers the luminal surface of the respiratory tract. The major function of mucus is to protect the lungs through mucociliary clearance of inhaled foreign particles and noxious chemicals. Mucus is comprised of water, ions, mucin glycoproteins, and a variety of other macromolecules, some of which possess anti-microbial, anti-protease, and anti-oxidant activities. Mucins comprise the major protein component of mucus and exist as secreted and cell-associated glycoproteins. Secreted, gel-forming mucins are mainly responsible for the viscoelastic property of mucus, which is crucial for effective mucociliary clearance. Cell-associated mucins shield the epithelial surface from pathogens through their extracellular domains and regulate intracellular signaling through their cytoplasmic regions. However, neither the exact structures of mucin glycoproteins, nor the manner through which their expression is regulated, are completely understood. This chapter reviews what is currently known about the cellular and molecular properties of airway mucins. PMID:23445810

The Development and Validation of an In Vitro Airway Model to Assess Realistic Airway Deposition and Drug Permeation Behavior of Orally Inhaled Products Across Synthetic Membranes.

PubMed

Huynh, Bao K; Traini, Daniela; Farkas, Dale R; Longest, P Worth; Hindle, Michael; Young, Paul M

2018-04-01

Current in vitro approaches to assess lung deposition, dissolution, and cellular transport behavior of orally inhaled products (OIPs) have relied on compendial impactors to collect drug particles that are likely to deposit in the airway; however, the main drawback with this approach is that these impactors do not reflect the airway and may not necessarily represent drug deposition behavior in vivo. The aim of this article is to describe the development and method validation of a novel hybrid in vitro approach to assess drug deposition and permeation behavior in a more representative airway model. The medium-sized Virginia Commonwealth University (VCU) mouth-throat (MT) and tracheal-bronchial (TB) realistic upper airway models were used in this study as representative models of the upper airway. The TB model was modified to accommodate two Snapwell ® inserts above the first TB airway bifurcation region to collect deposited nebulized ciprofloxacin-hydrochloride (CIP-HCL) droplets as a model drug aerosol system. Permeation characteristics of deposited nebulized CIP-HCL droplets were assessed across different synthetic membranes using the Snapwell test system. The Snapwell test system demonstrated reproducible and discriminatory drug permeation profiles for already dissolved and nebulized CIP-HCL droplets through a range of synthetic permeable membranes under different test conditions. The rate and extent of drug permeation depended on the permeable membrane material used, presence of a stirrer in the receptor compartment, and, most importantly, the drug collection method. This novel hybrid in vitro approach, which incorporates a modified version of a realistic upper airway model, coupled with the Snapwell test system holds great potential to evaluate postairway deposition characteristics, such as drug permeation and particle dissolution behavior of OIPs. Future studies will expand this approach using a cell culture-based setup instead of synthetic membranes, within a

Transport of calcium ions through a bulk membrane by use of a dynamic combinatorial library.

PubMed

Saggiomo, Vittorio; Lüning, Ulrich

2009-07-07

In a bulk membrane transport experiment, a dynamic combinatorial library (DCL) has been used to transport calcium ions; the calcium ions amplify the formation of a macrocyclic carrier which results in transport.

76 FR 65769 - Application of Friendship Airways, Inc. d/b/a Yellow Air Taxi for Commuter Authority

Federal Register 2010, 2011, 2012, 2013, 2014

2011-10-24

... DEPARTMENT OF TRANSPORTATION Office of the Secretary Application of Friendship Airways, Inc. d/b/a Yellow Air Taxi for Commuter Authority AGENCY: Department of Transportation. ACTION: Notice of Order to... issued to Friendship Airways, Inc. d/b/a Yellow Air Taxi and deny its application to resume commuter...

Computationally efficient analysis of particle transport and deposition in a human whole-lung-airway model. Part I: Theory and model validation.

PubMed

Kolanjiyil, Arun V; Kleinstreuer, Clement

2016-12-01

Computational predictions of aerosol transport and deposition in the human respiratory tract can assist in evaluating detrimental or therapeutic health effects when inhaling toxic particles or administering drugs. However, the sheer complexity of the human lung, featuring a total of 16 million tubular airways, prohibits detailed computer simulations of the fluid-particle dynamics for the entire respiratory system. Thus, in order to obtain useful and efficient particle deposition results, an alternative modeling approach is necessary where the whole-lung geometry is approximated and physiological boundary conditions are implemented to simulate breathing. In Part I, the present new whole-lung-airway model (WLAM) represents the actual lung geometry via a basic 3-D mouth-to-trachea configuration while all subsequent airways are lumped together, i.e., reduced to an exponentially expanding 1-D conduit. The diameter for each generation of the 1-D extension can be obtained on a subject-specific basis from the calculated total volume which represents each generation of the individual. The alveolar volume was added based on the approximate number of alveoli per generation. A wall-displacement boundary condition was applied at the bottom surface of the first-generation WLAM, so that any breathing pattern due to the negative alveolar pressure can be reproduced. Specifically, different inhalation/exhalation scenarios (rest, exercise, etc.) were implemented by controlling the wall/mesh displacements to simulate realistic breathing cycles in the WLAM. Total and regional particle deposition results agree with experimental lung deposition results. The outcomes provide critical insight to and quantitative results of aerosol deposition in human whole-lung airways with modest computational resources. Hence, the WLAM can be used in analyzing human exposure to toxic particulate matter or it can assist in estimating pharmacological effects of administered drug-aerosols. As a practical

Inositol trisphosphate modification of ion transport in rough endoplasmic reticulum.

PubMed

Muallem, S; Schoeffield, M; Pandol, S; Sachs, G

1985-07-01

The ion transport properties of the rough endoplasmic reticulum (RER) from liver have been defined by using measurements of active and potential gradient-driven transport. The Ca2+ pump is shown to be electrogenic, and both ATP and potential difference is able to drive vanadate-inhibitable Ca2+ uptake into the RER. ATP-dependent Ca2+ transport into the RER depends on the presence of tetraethylammonium-sensitive cation conductance and a furosemide-inhibited cation/chloride cotransport pathway. Inositol trisphosphate does not affect either of the monovalent ion translocation systems but activates a Ca2+ conductance in the RER, allowing efflux of RER Ca2+ stores into the cytosol in exchange for K+ uptake.

Inositol trisphosphate modification of ion transport in rough endoplasmic reticulum.

PubMed Central

Muallem, S; Schoeffield, M; Pandol, S; Sachs, G

1985-01-01

The ion transport properties of the rough endoplasmic reticulum (RER) from liver have been defined by using measurements of active and potential gradient-driven transport. The Ca2+ pump is shown to be electrogenic, and both ATP and potential difference is able to drive vanadate-inhibitable Ca2+ uptake into the RER. ATP-dependent Ca2+ transport into the RER depends on the presence of tetraethylammonium-sensitive cation conductance and a furosemide-inhibited cation/chloride cotransport pathway. Inositol trisphosphate does not affect either of the monovalent ion translocation systems but activates a Ca2+ conductance in the RER, allowing efflux of RER Ca2+ stores into the cytosol in exchange for K+ uptake. PMID:3874400

An axisymmetric single-path model for gas transport in the conducting airways.

PubMed

Madasu, Srinath; Borhan, All; Ultman, James S

2006-02-01

In conventional one-dimensional single-path models, radially averaged concentration is calculated as a function of time and longitudinal position in the lungs, and coupled convection and diffusion are accounted for with a dispersion coefficient. The axisymmetric single-path model developed in this paper is a two-dimensional model that incorporates convective-diffusion processes in a more fundamental manner by simultaneously solving the Navier-Stokes and continuity equations with the convection-diffusion equation. A single airway path was represented by a series of straight tube segments interconnected by leaky transition regions that provide for flow loss at the airway bifurcations. As a sample application, the model equations were solved by a finite element method to predict the unsteady state dispersion of an inhaled pulse of inert gas along an airway path having dimensions consistent with Weibel's symmetric airway geometry. Assuming steady, incompressible, and laminar flow, a finite element analysis was used to solve for the axisymmetric pressure, velocity and concentration fields. The dispersion calculated from these numerical solutions exhibited good qualitative agreement with the experimental values, but quantitatively was in error by 20%-30% due to the assumption of axial symmetry and the inability of the model to capture the complex recirculatory flows near bifurcations.

The Transport of Ions Across Plant Cell Membranes.

ERIC Educational Resources Information Center

Baker, D. A.

1981-01-01

Presented is one of a series of articles designed to help science teachers keep current on ideas in specific areas of biology. This article provides information about ion transport in plant cells. (PB)

An Improved Green's Function for Ion Beam Transport

NASA Technical Reports Server (NTRS)

Tweed, J.; Wilson, J. W.; Tripathi, R. K.

2003-01-01

Ion beam transport theory allows testing of material transmission properties in the laboratory environment generated by particle accelerators. This is a necessary step in materials development and evaluation for space use. The approximations used in solving the Boltzmann transport equation for the space setting are often not sufficient for laboratory work and those issues are the main emphasis of the present work. In consequence, an analytic solution of the linear Boltzmann equation is pursued in the form of a Green's function allowing flexibility in application to a broad range of boundary value problems. It has been established that simple solutions can be found for the high charge and energy (HZE) by ignoring nuclear energy downshifts and dispersion. Such solutions were found to be supported by experimental evidence with HZE ion beams when multiple scattering was added. Lacking from the prior solutions were range and energy straggling and energy downshift with dispersion associated with nuclear events. Recently, we have found global solutions including these effects providing a broader class of HZE ion solutions.

Airflow and Particle Transport Through Human Airways: A Systematic Review

NASA Astrophysics Data System (ADS)

Kharat, S. B.; Deoghare, A. B.; Pandey, K. M.

2017-08-01

This paper describes review of the relevant literature about two phase analysis of air and particle flow through human airways. An emphasis of the review is placed on elaborating the steps involved in two phase analysis, which are Geometric modelling methods and Mathematical models. The first two parts describes various approaches that are followed for constructing an Airway model upon which analysis are conducted. Broad two categories of geometric modelling viz. Simplified modelling and Accurate modelling using medical scans are discussed briefly. Ease and limitations of simplified models, then examples of CT based models are discussed. In later part of the review different mathematical models implemented by researchers for analysis are briefed. Mathematical models used for Air and Particle phases are elaborated separately.

Variable stoichiometry in active ion transport: theoretical analysis of physiological consequences.

PubMed Central

Johnson, E A; Tanford, C; Reynolds, J A

1985-01-01

Active ion transport systems with fixed stoichiometry are subject to a thermodynamic limit on the ion concentration gradients that they can generate and maintain, and their net rates of transport must inevitably decrease as this limit is approached. The capability to vary stoichiometry might thus be physiologically advantageous: a shift to lower stoichiometry (fewer ions pumped per reaction cycle) at increasing thermodynamic load could increase the limit on the supportable concentration gradient and could accelerate the rate of transport under high-load conditions. Here we present a theoretical and numerical analysis of this possibility, using the sarcoplasmic reticulum ATP-driven Ca pump as the example. It is easy to introduce alternate pathways into the reaction cycle for this system to shift the stoichiometry (Ca2+/ATP) from the normal value of 2:1 to 1:1, but it cannot be done without simultaneous generation of a pathway for uncoupled leak of Ca2+ across the membrane. This counteracts the advantageous effect of the change in transport stoichiometry and a physiologically useful rate acceleration cannot be obtained. This result is likely to be generally applicable to most active transport systems. PMID:3860866

Variable stoichiometry in active ion transport: theoretical analysis of physiological consequences.

PubMed

Johnson, E A; Tanford, C; Reynolds, J A

1985-08-01

Active ion transport systems with fixed stoichiometry are subject to a thermodynamic limit on the ion concentration gradients that they can generate and maintain, and their net rates of transport must inevitably decrease as this limit is approached. The capability to vary stoichiometry might thus be physiologically advantageous: a shift to lower stoichiometry (fewer ions pumped per reaction cycle) at increasing thermodynamic load could increase the limit on the supportable concentration gradient and could accelerate the rate of transport under high-load conditions. Here we present a theoretical and numerical analysis of this possibility, using the sarcoplasmic reticulum ATP-driven Ca pump as the example. It is easy to introduce alternate pathways into the reaction cycle for this system to shift the stoichiometry (Ca2+/ATP) from the normal value of 2:1 to 1:1, but it cannot be done without simultaneous generation of a pathway for uncoupled leak of Ca2+ across the membrane. This counteracts the advantageous effect of the change in transport stoichiometry and a physiologically useful rate acceleration cannot be obtained. This result is likely to be generally applicable to most active transport systems.

Visualization of lithium-ion transport and phase evolution within and between manganese oxide nanorods

DOE PAGES

Xu, Feng; Wu, Lijun; Meng, Qingping; ...

2017-05-24

Multiple lithium-ion transport pathways and local phase changes upon lithiation in silver hollandite are revealed via in situ microscopy including electron diffraction, imaging and spectroscopy, coupled with density functional theory and phase field calculations. Here, we report unexpected inter-nanorod lithium-ion transport, where the reaction fronts and kinetics are maintained within the neighbouring nanorod. Notably, this is the first time-resolved visualization of lithium-ion transport within and between individual nanorods, where the impact of oxygen deficiencies is delineated. Initially, fast lithium-ion transport is observed along the long axis with small net volume change, resulting in two lithiated silver hollandite phases distinguishable bymore » orthorhombic distortion. As a result, a slower reaction front is observed, with formation of polyphase lithiated silver hollandite and face-centred-cubic silver metal with substantial volume expansion. Our results indicate lithium-ion transport is not confined within a single nanorod and may provide a paradigm shift for one-dimensional tunnelled materials, particularly towards achieving high-rate capability.« less

Visualization of lithium-ion transport and phase evolution within and between manganese oxide nanorods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Feng; Wu, Lijun; Meng, Qingping

Multiple lithium-ion transport pathways and local phase changes upon lithiation in silver hollandite are revealed via in situ microscopy including electron diffraction, imaging and spectroscopy, coupled with density functional theory and phase field calculations. Here, we report unexpected inter-nanorod lithium-ion transport, where the reaction fronts and kinetics are maintained within the neighbouring nanorod. Notably, this is the first time-resolved visualization of lithium-ion transport within and between individual nanorods, where the impact of oxygen deficiencies is delineated. Initially, fast lithium-ion transport is observed along the long axis with small net volume change, resulting in two lithiated silver hollandite phases distinguishable bymore » orthorhombic distortion. As a result, a slower reaction front is observed, with formation of polyphase lithiated silver hollandite and face-centred-cubic silver metal with substantial volume expansion. Our results indicate lithium-ion transport is not confined within a single nanorod and may provide a paradigm shift for one-dimensional tunnelled materials, particularly towards achieving high-rate capability.« less

Randomised comparison of the effectiveness of the laryngeal mask airway supreme, i-gel and current practice in the initial airway management of prehospital cardiac arrest (REVIVE-Airways): a feasibility study research protocol.

PubMed

Benger, Jonathan Richard; Voss, Sarah; Coates, David; Greenwood, Rosemary; Nolan, Jerry; Rawstorne, Steven; Rhys, Megan; Thomas, Matthew

2013-01-01

Effective cardiopulmonary resuscitation with appropriate airway management improves outcomes following out-of-hospital cardiac arrest (OHCA). Historically, tracheal intubation has been accepted as the optimal form of OHCA airway management in the UK. The Joint Royal Colleges Ambulance Liaison Committee recently concluded that newer supraglottic airway devices (SADs) are safe and effective devices for hospital procedures and that their use in OHCA should be investigated. This study will address an identified gap in current knowledge by assessing whether it is feasible to use a cluster randomised design to compare SADs with current practice, and also to each other, during OHCA. The primary objective of this study is to assess the feasibility of a cluster randomised trial to compare the ventilation success of two newer SADs: the i-gel and the laryngeal mask airway supreme to usual practice during the initial airway management of OHCA. The secondary objectives are to collect data on ventilation success, further airway interventions required, loss of a previously established airway during transport, airway management on arrival at hospital (or termination of the resuscitation attempt), initial resuscitation success, survival to intensive care admission, survival to hospital discharge and patient outcome at 3 months. Ambulance paramedics will be randomly allocated to one of the three methods of airway management. Adults in medical OHCA attended by a trial paramedic will be eligible for the study. Approval for the study has been obtained from a National Health Service Research Ethics Committee with authority to review proposals for trials of a medical device in incapacitated adults. The results will be made publicly available on an open access website, and we will publish the findings in appropriate journals and present them at national and international conferences relevant to the subject field. ISRCTN: 18528625.

Randomised comparison of the effectiveness of the laryngeal mask airway supreme, i-gel and current practice in the initial airway management of prehospital cardiac arrest (REVIVE-Airways): a feasibility study research protocol

PubMed Central

Benger, Jonathan Richard; Voss, Sarah; Coates, David; Greenwood, Rosemary; Nolan, Jerry; Rawstorne, Steven; Rhys, Megan; Thomas, Matthew

2013-01-01

Introduction Effective cardiopulmonary resuscitation with appropriate airway management improves outcomes following out-of-hospital cardiac arrest (OHCA). Historically, tracheal intubation has been accepted as the optimal form of OHCA airway management in the UK. The Joint Royal Colleges Ambulance Liaison Committee recently concluded that newer supraglottic airway devices (SADs) are safe and effective devices for hospital procedures and that their use in OHCA should be investigated. This study will address an identified gap in current knowledge by assessing whether it is feasible to use a cluster randomised design to compare SADs with current practice, and also to each other, during OHCA. Methods and analysis The primary objective of this study is to assess the feasibility of a cluster randomised trial to compare the ventilation success of two newer SADs: the i-gel and the laryngeal mask airway supreme to usual practice during the initial airway management of OHCA. The secondary objectives are to collect data on ventilation success, further airway interventions required, loss of a previously established airway during transport, airway management on arrival at hospital (or termination of the resuscitation attempt), initial resuscitation success, survival to intensive care admission, survival to hospital discharge and patient outcome at 3 months. Ambulance paramedics will be randomly allocated to one of the three methods of airway management. Adults in medical OHCA attended by a trial paramedic will be eligible for the study. Ethics and dissemination Approval for the study has been obtained from a National Health Service Research Ethics Committee with authority to review proposals for trials of a medical device in incapacitated adults. The results will be made publicly available on an open access website, and we will publish the findings in appropriate journals and present them at national and international conferences relevant to the subject field. Trial

The role of airway mucus in pulmonary toxicology.

PubMed Central

Samet, J M; Cheng, P W

1994-01-01

Airway mucus is a complex airway secretion whose primary function as part of the mucociliary transport mechanism is to to serve as renewable and transportable barrier against inhaled particulates and toxic agents. The rheologic properties necessary for this function are imparted by glycoproteins, or mucins. Some respiratory disease states, e.g., asthma, cystic fibrosis, and bronchitis, are characterized by quantitative and qualitative changes in mucus biosynthesis that contribute to pulmonary pathology. Similar alterations in various aspects of mucin biochemistry and biophysics, leading to mucus hypersecretion and altered mucus rheology, result from inhalation of certain air pollutants, such as ozone, sulfur dioxide, nitrogen dioxide, and cigarette smoke. The consequences of these pollutant-induced alterations in mucus biology are discussed in the context of pulmonary pathophysiology and toxicology. PMID:7925190

In situ measurement of airway surface liquid [K+] using a ratioable K+-sensitive fluorescent dye.

PubMed

Namkung, Wan; Song, Yuanlin; Mills, Aaron D; Padmawar, Prashant; Finkbeiner, Walter E; Verkman, A S

2009-06-05

The airway surface liquid (ASL) is the thin fluid layer lining airway surface epithelial cells, whose volume and composition are tightly regulated and may be abnormal in cystic fibrosis (CF). We synthesized a two-color fluorescent dextran to measure ASL [K(+)], TAC-Lime-dextran-TMR, consisting of a green-fluorescing triazacryptand K(+) ionophore-Bodipy conjugate, coupled to dextran, together with a red fluorescing tetramethylrhodamine reference chromophore. TAC-Lime-dextran-TMR fluorescence was K(+)-selective, increasing >4-fold with increasing [K(+)] from 0 to 40 mm. In well differentiated human airway epithelial cells, ASL [K(+)] was 20.8 +/- 0.3 mm and decreased by inhibition of the Na(+)/K(+) pump (ouabain), ENaC (amiloride), CF transmembrane conductance regulator (CFTR(inh)-172), or K(+) channels (TEA or XE991). ASL [K(+)] was increased by forskolin but not affected by Na(+)/K(+)/2Cl(-) cotransporter inhibition (bumetanide). Functional and expression studies indicated the involvement of [K(+)] channels KCNQ1, KCNQ3, and KCNQ5 as determinants of ASL [K(+)]. [K(+)] in CF cultures was similar to that in non-CF cultures, suggesting that abnormal ASL [K(+)] is not a factor in CF lung disease. In intact airways, ASL [K(+)] was also well above extracellular [K(+)]: 22 +/- 1 mm in pig trachea ex vivo and 16 +/- 1 mm in mouse trachea in vivo. Our results provide the first noninvasive measurements of [K(+)] in the ASL and indicate the involvement of apical and basolateral membrane ion transporters in maintaining a high ASL [K(+)].

Promotion of Water Channels for Enhanced Ion Transport in 14 nm Diameter Carbon Nanotubes.

PubMed

Sheng, Jiadong; Zhu, Qi; Zeng, Xian; Yang, Zhaohui; Zhang, Xiaohua

2017-03-29

Ion transport plays an important role in solar-to-electricity conversion, drug delivery, and a variety of biological processes. Carbon nanotube (CNT) is a promising material as an ion transporter in the applications of the mimicking of natural ion channels, desalination, and energy harvesting. Here, we demonstrate a unique, enhanced ion transport through a vertically aligned multiwall CNT membrane after the application of an electric potential across CNT membranes. Interestingly, electrowetting arising from the application of an electric potential is critical for the enhancement of overall ion transport rate through CNT membranes. The wettability of a liquid with high surface tension on the interior channel walls of CNTs increases during an electric potential treatment and promotes the formation of water channels in CNTs. The formation of water channels in CNTs induces an increase in overall ion diffusion through CNT membranes. This phenomenon is also related to a decrease in the charge transfer resistance of CNTs (R ct ) after an electric potential is applied. Correspondingly, the enhanced ion flow rate gives rise to an enhancement in the capacitive performance of CNT based membranes. Our observations might have profound impact on the development of CNT based energy storage devices as well as artificial ion channels.

History-dependent ion transport through conical nanopipettes and the implications in energy conversion dynamics at nanoscale interfaces.

PubMed

Li, Yan; Wang, Dengchao; Kvetny, Maksim M; Brown, Warren; Liu, Juan; Wang, Gangli

2015-01-01

The dynamics of ion transport at nanostructured substrate-solution interfaces play vital roles in high-density energy conversion, stochastic chemical sensing and biosensing, membrane separation, nanofluidics and fundamental nanoelectrochemistry. Further advancements in these applications require a fundamental understanding of ion transport at nanoscale interfaces. The understanding of the dynamic or transient transport, and the key physical process involved, is limited, which contrasts sharply with widely studied steady-state ion transport features at atomic and nanometer scale interfaces. Here we report striking time-dependent ion transport characteristics at nanoscale interfaces in current-potential ( I - V ) measurements and theoretical analyses. First, a unique non-zero I - V cross-point and pinched I - V curves are established as signatures to characterize the dynamics of ion transport through individual conical nanopipettes. Second, ion transport against a concentration gradient is regulated by applied and surface electrical fields. The concept of ion pumping or separation is demonstrated via the selective ion transport against concentration gradients through individual nanopipettes. Third, this dynamic ion transport process under a predefined salinity gradient is discussed in the context of nanoscale energy conversion in supercapacitor type charging-discharging, as well as chemical and electrical energy conversion. The analysis of the emerging current-potential features establishes the urgently needed physical foundation for energy conversion employing ordered nanostructures. The elucidated mechanism and established methodology can be generalized into broadly-defined nanoporous materials and devices for improved energy, separation and sensing applications.

History-dependent ion transport through conical nanopipettes and the implications in energy conversion dynamics at nanoscale interfaces

DOE PAGES

Li, Yan; Wang, Dengchao; Kvetny, Maksim M.; ...

2014-08-20

The dynamics of ion transport at nanostructured substrate–solution interfaces play vital roles in high-density energy conversion, stochastic chemical sensing and biosensing, membrane separation, nanofluidics and fundamental nanoelectrochemistry. Advancements in these applications require a fundamental understanding of ion transport at nanoscale interfaces. The understanding of the dynamic or transient transport, and the key physical process involved, is limited, which contrasts sharply with widely studied steady-state ion transport features at atomic and nanometer scale interfaces. Here we report striking time-dependent ion transport characteristics at nanoscale interfaces in current–potential (I–V) measurements and theoretical analyses. First, a unique non-zero I–V cross-point and pinched I–Vmore » curves are established as signatures to characterize the dynamics of ion transport through individual conical nanopipettes. Moreoever, ion transport against a concentration gradient is regulated by applied and surface electrical fields. The concept of ion pumping or separation is demonstrated via the selective ion transport against concentration gradients through individual nanopipettes. Third, this dynamic ion transport process under a predefined salinity gradient is discussed in the context of nanoscale energy conversion in supercapacitor type charging–discharging, as well as chemical and electrical energy conversion. Our analysis of the emerging current–potential features establishes the urgently needed physical foundation for energy conversion employing ordered nanostructures. The elucidated mechanism and established methodology can be generalized into broadly-defined nanoporous materials and devices for improved energy, separation and sensing applications.« less

Guanine-based amphiphiles: synthesis, ion transport properties and biological activity.

PubMed

Musumeci, Domenica; Irace, Carlo; Santamaria, Rita; Milano, Domenico; Tecilla, Paolo; Montesarchio, Daniela

2015-03-01

Novel amphiphilic guanine derivatives, here named Gua1 and Gua2, have been prepared through few, simple and efficient synthetic steps. In ion transport experiments through phospholipid bilayers, carried out to evaluate their ability to mediate H(+) transport, Gua2 showed high activity. When this compound was investigated for ion-selective transport activities, no major differences were observed in the behaviour with cations while, in the case of anions, selective activity was observed in the series I(-)>Br(-)>Cl(-)>F(-). The bioactivity of these guanine analogues has been evaluated on a panel of human tumour and non-tumour cell lines in preliminary in vitro cytotoxicity assays, showing a relevant antiproliferative profile for Gua2. Copyright © 2014 Elsevier Ltd. All rights reserved.

Fast Ion and Thermal Plasma Transport in Turbulent Waves in the Large Plasma Device (LAPD)

NASA Astrophysics Data System (ADS)

Zhou, Shu

2011-10-01

The transport of fast ions and thermal plasmas in electrostatic microturbulence is studied. Strong density and potential fluctuations (δn / n ~ δϕ / kTe ~ 0 . 5 , f ~5-50 kHz) are observed in the LAPD in density gradient regions produced by obstacles with slab or cylindrical geometry. Wave characteristics and the associated plasma transport are modified by driving sheared E ×B drift through biasing the obstacle, and by modification of the axial magnetic fields (Bz) and the plasma species. Cross-field plasma transport is suppressed with small bias and large Bz, and is enhanced with large bias and small Bz. Suppressed cross-field thermal transport coincides with a 180° phase shift between the density and potential fluctuations in the radial direction, while the enhanced thermal transport is associated with modes having low mode number (m = 1) and long radial correlation length. Large gyroradius lithium ions (ρfast /ρs ~ 10) orbit through the turbulent region. Scans with a collimated analyzer and with Langmuir probes give detailed profiles of the fast ion spatial-temporal distribution and of the fluctuating fields. Fast-ion transport decreases rapidly with increasing fast-ion gyroradius. Background waves with different scale lengths also alter the fast ion transport: Beam diffusion is smaller in waves with smaller structures (higher mode number); also, coherent waves with long correlation length cause less beam diffusion than turbulent waves. Experimental results agree well with gyro-averaging theory. When the fast ion interacts with the wave for most of a wave period, a transition from super-diffusive to sub-diffusive transport is observed, as predicted by diffusion theory. A Monte Carlo trajectory-following code simulates the interaction of the fast ions with the measured turbulent fields. Good agreement between observation and modeling is observed. Work funded by DOE and NSF and performed at the Basic Plasma Science Facility.

Interplay of Transport and Morphology in Nanostructured Ion-Containing Polymers

NASA Astrophysics Data System (ADS)

Park, Moon Jeong

The global energy crisis and an increase in environmental pollution in the recent years have drawn the attention of the scientific community to develop innovative ways to improve energy storage and find more efficient methods of transporting the energy. Polymers containing charged species that show high ionic conductivity and good mechanical integrity are the essential components of these energy storage and transport systems. In this talk, first, I will present a fundamental understanding of the thermodynamics and transport in ion-containing block copolymers with a focus on the structure-property relationships. Tailoring the intermolecular interactions between the polymer matrix and the embedded charges appeared to be vital for controlling the transport properties. Particularly, the achievement of well-defined self-assembled morphologies with three-dimensional symmetries has proven to facilitate fast ion transport by constructing less tortuous ion-conducting pathways. Examples of attained morphologies include disorder, lamellae, gyroid, Fddd, hexagonal cylinder, body-centered cubic, face-centered cubic, and A15 phases. Second, various strategies for accessing high cation transference number as well as improved ionic conductivity from ionic-containing polymers are enclosed; (1) the inclusion of terminal ionic units as a new means to control the nanoscale morphologies and the transport efficiency of block copolymer electrolytes and (2) the addition of zwitterions that offered a polar medium close to water, and accordingly increased the charge density and ionic conductivity. The obtained knowledge on polymer electrolytes could be used in a wide range of emerging nanotechnologies such as fuel cells, lithium batteries, and electro-active actuators.

Studies on Molecular and Ion Transport in Silicalite Membranes and Applications as Ion Separator for Redox Flow Battery

NASA Astrophysics Data System (ADS)

Yang, Ruidong

Microporous zeolite membranes have been widely studied for molecular separations based on size exclusion or preferential adsorption-diffusion mechanisms. The MFI-type zeolite membranes were also demonstrated for brine water desalination by molecular sieving effect. In this research, the pure silica MFI-type zeolite (i.e. silicalite) membrane has been for the first time demonstrated for selective permeation of hydrated proton (i.e. H3O+) in acidic electrolyte solutions. The silicalite membrane allows for permeation of H 3O+ ions, but is inaccessible to the large hydrated multivalent vanadium ions due to steric effect. The silicalite membrane has been further demonstrated as an effective ion separator in the all-vanadium redox flow battery (RFB).The silicalite is nonionic and its proton conductivity relies on the electric field-driven H3O+ transport through the sub nanometer-sized pores under the RFB operation conditions. The silicalite membrane displayed a significantly reduced self-discharge rate because of its high proton-to-vanadium ion transport selectivity. However, the nonionic nature of the silicalite membrane and very small diffusion channel size render low proton conductivity and is therefore inefficient as ion exchange membranes (IEMs) for practical applications. The proton transport efficiency may be improved by reducing the membrane thickness. However, the zeolite thin films are extremely fragile and must be supported on mechanically strong and rigid porous substrates. In this work, silicalite-Nafion composite membranes were synthesized to achieve a colloidal silicalite skin on the Nafion thin film base. The "colloidal zeolite-ionic polymer" layered composite membrane combines the advantages of high proton-selectivity of the zeolite layer and the mechanical flexibility and low proton transport resistance of the ionic polymer membrane. The composite membrane exhibited higher proton/vanadium ion separation selectivity and lower electrical resistance than

Synthesis and ion transport characterization of hot-pressed Ag+ ion conducting glass-polymer electrolytes

NASA Astrophysics Data System (ADS)

Chandra, A.

2013-07-01

Synthesis and ion transport characterization of a new Ag+ ion conducting glass-polymer electrolyte (GPE) films: (1- x) PEO: x [0.8(0.75AgI:0.25AgCl):0.2(Ag2O:V2O5)], where 0 < x < 50 wt%, are reported. The composition: 70PEO: 30[0.8(0.75AgI:0.25AgCl):0.2(Ag2O:V2O5)] with conductivity ( σ) 7.7 × 10-7 Ω-1 cm-1 is identified as highest conducting composition referred to as the optimum conducting composition (OCC). Approximately two and half orders of conductivity enhancement have been achieved in OCC from that of the pure polymer poly(ethylene oxide). The glass-polymer complexation is confirmed by the XRD, FTIR, DSC and TGA techniques. The ion transport behavior has been reported on the basis of experimental measurements on some basic ionic parameters. A solid state polymeric battery has been fabricated by using GPE OCC as an electrolyte and their important cell parameters have been also calculated from the discharge profiles.

Regulation of lysosomal ion homeostasis by channels and transporters.

PubMed

Xiong, Jian; Zhu, Michael X

2016-08-01

Lysosomes are the major organelles that carry out degradation functions. They integrate and digest materials compartmentalized by endocytosis, phagocytosis or autophagy. In addition to more than 60 hydrolases residing in the lysosomes, there are also ion channels and transporters that mediate the flux or transport of H(+), Ca(2+), Na(+), K(+), and Cl(-) across the lysosomal membranes. Defects in ionic exchange can lead to abnormal lysosome morphology, defective vesicle trafficking, impaired autophagy, and diseases such as neurodegeneration and lysosomal storage disorders. The latter are characterized by incomplete lysosomal digestion and accumulation of toxic materials inside enlarged intracellular vacuoles. In addition to degradation, recent studies have revealed the roles of lysosomes in metabolic pathways through kinases such as mechanistic target of rapamycin (mTOR) and transcriptional regulation through calcium signaling molecules such as transcription factor EB (TFEB) and calcineurin. Owing to the development of new approaches including genetically encoded fluorescence probes and whole endolysosomal patch clamp recording techniques, studies on lysosomal ion channels have made remarkable progress in recent years. In this review, we will focus on the current knowledge of lysosome-resident ion channels and transporters, discuss their roles in maintaining lysosomal function, and evaluate how their dysfunction can result in disease.

Ion and metabolite transport in the chloroplast of algae: lessons from land plants.

PubMed

Marchand, Justine; Heydarizadeh, Parisa; Schoefs, Benoît; Spetea, Cornelia

2018-06-01

Chloroplasts are endosymbiotic organelles and play crucial roles in energy supply and metabolism of eukaryotic photosynthetic organisms (algae and land plants). They harbor channels and transporters in the envelope and thylakoid membranes, mediating the exchange of ions and metabolites with the cytosol and the chloroplast stroma and between the different chloroplast subcompartments. In secondarily evolved algae, three or four envelope membranes surround the chloroplast, making more complex the exchange of ions and metabolites. Despite the importance of transport proteins for the optimal functioning of the chloroplast in algae, and that many land plant homologues have been predicted, experimental evidence and molecular characterization are missing in most cases. Here, we provide an overview of the current knowledge about ion and metabolite transport in the chloroplast from algae. The main aspects reviewed are localization and activity of the transport proteins from algae and/or of homologues from other organisms including land plants. Most chloroplast transporters were identified in the green alga Chlamydomonas reinhardtii, reside in the envelope and participate in carbon acquisition and metabolism. Only a few identified algal transporters are located in the thylakoid membrane and play role in ion transport. The presence of genes for putative transporters in green algae, red algae, diatoms, glaucophytes and cryptophytes is discussed, and roles in the chloroplast are suggested. A deep knowledge in this field is required because algae represent a potential source of biomass and valuable metabolites for industry, medicine and agriculture.

Structure-Functional Basis of Ion Transport in Sodium–Calcium Exchanger (NCX) Proteins

PubMed Central

Giladi, Moshe; Shor, Reut; Lisnyansky, Michal; Khananshvili, Daniel

2016-01-01

The membrane-bound sodium–calcium exchanger (NCX) proteins shape Ca2+ homeostasis in many cell types, thus participating in a wide range of physiological and pathological processes. Determination of the crystal structure of an archaeal NCX (NCX_Mj) paved the way for a thorough and systematic investigation of ion transport mechanisms in NCX proteins. Here, we review the data gathered from the X-ray crystallography, molecular dynamics simulations, hydrogen–deuterium exchange mass-spectrometry (HDX-MS), and ion-flux analyses of mutants. Strikingly, the apo NCX_Mj protein exhibits characteristic patterns in the local backbone dynamics at particular helix segments, thereby possessing characteristic HDX profiles, suggesting structure-dynamic preorganization (geometric arrangements of catalytic residues before the transition state) of conserved α1 and α2 repeats at ion-coordinating residues involved in transport activities. Moreover, dynamic preorganization of local structural entities in the apo protein predefines the status of ion-occlusion and transition states, even though Na+ or Ca2+ binding modifies the preceding backbone dynamics nearby functionally important residues. Future challenges include resolving the structural-dynamic determinants governing the ion selectivity, functional asymmetry and ion-induced alternating access. Taking into account the structural similarities of NCX_Mj with the other proteins belonging to the Ca2+/cation exchanger superfamily, the recent findings can significantly improve our understanding of ion transport mechanisms in NCX and similar proteins. PMID:27879668

Structure-Functional Basis of Ion Transport in Sodium-Calcium Exchanger (NCX) Proteins.

PubMed

Giladi, Moshe; Shor, Reut; Lisnyansky, Michal; Khananshvili, Daniel

2016-11-22

The membrane-bound sodium-calcium exchanger (NCX) proteins shape Ca 2+ homeostasis in many cell types, thus participating in a wide range of physiological and pathological processes. Determination of the crystal structure of an archaeal NCX (NCX_Mj) paved the way for a thorough and systematic investigation of ion transport mechanisms in NCX proteins. Here, we review the data gathered from the X-ray crystallography, molecular dynamics simulations, hydrogen-deuterium exchange mass-spectrometry (HDX-MS), and ion-flux analyses of mutants. Strikingly, the apo NCX_Mj protein exhibits characteristic patterns in the local backbone dynamics at particular helix segments, thereby possessing characteristic HDX profiles, suggesting structure-dynamic preorganization (geometric arrangements of catalytic residues before the transition state) of conserved α₁ and α₂ repeats at ion-coordinating residues involved in transport activities. Moreover, dynamic preorganization of local structural entities in the apo protein predefines the status of ion-occlusion and transition states, even though Na⁺ or Ca 2+ binding modifies the preceding backbone dynamics nearby functionally important residues. Future challenges include resolving the structural-dynamic determinants governing the ion selectivity, functional asymmetry and ion-induced alternating access. Taking into account the structural similarities of NCX_Mj with the other proteins belonging to the Ca 2+ /cation exchanger superfamily, the recent findings can significantly improve our understanding of ion transport mechanisms in NCX and similar proteins.

Theory of ion transport with fast acid-base equilibrations in bioelectrochemical systems.

PubMed

Dykstra, J E; Biesheuvel, P M; Bruning, H; Ter Heijne, A

2014-07-01

Bioelectrochemical systems recover valuable components and energy in the form of hydrogen or electricity from aqueous organic streams. We derive a one-dimensional steady-state model for ion transport in a bioelectrochemical system, with the ions subject to diffusional and electrical forces. Since most of the ionic species can undergo acid-base reactions, ion transport is combined in our model with infinitely fast ion acid-base equilibrations. The model describes the current-induced ammonia evaporation and recovery at the cathode side of a bioelectrochemical system that runs on an organic stream containing ammonium ions. We identify that the rate of ammonia evaporation depends not only on the current but also on the flow rate of gas in the cathode chamber, the diffusion of ammonia from the cathode back into the anode chamber, through the ion exchange membrane placed in between, and the membrane charge density.

Mutation of EpCAM leads to intestinal barrier and ion transport dysfunction.

PubMed

Kozan, Philip A; McGeough, Matthew D; Peña, Carla A; Mueller, James L; Barrett, Kim E; Marchelletta, Ronald R; Sivagnanam, Mamata

2015-05-01

Congenital tufting enteropathy (CTE) is a devastating diarrheal disease seen in infancy that is typically associated with villous changes and the appearance of epithelial tufts. We previously found mutations in epithelial cell adhesion molecule (EpCAM) to be causative in CTE. We developed a knock-down cell model of CTE through transfection of an EpCAM shRNA construct into T84 colonic epithelial cells to elucidate the in vitro role of EpCAM in barrier function and ion transport. Cells with EpCAM deficiency exhibited decreased electrical resistance, increased permeability, and decreased ion transport. Based on mutations in CTE patients, an in vivo mouse model was developed, with tamoxifen-inducible deletion of exon 4 in Epcam resulting in mutant protein with decreased expression. Tamoxifen treatment of Epcam (Δ4/Δ4) mice resulted in pathological features of villous atrophy and epithelial tufts, similar to those in human CTE patients, within 4 days post induction. Epcam (Δ4/Δ4) mice also showed decreased expression of tight junctional proteins, increased permeability, and decreased ion transport in the intestines. Taken together, these findings reveal mechanisms that may underlie disease in CTE. Knock-down EpCAM cell model of congenital tufting enteropathy was developed. In vivo inducible mouse model was developed resulting in mutant EpCAM protein. Cells with EpCAM deficiency demonstrated barrier and ion transport dysfunction. Tamoxifen-treated Epcam (Δ4/Δ4) mice demonstrated pathological features. Epcam (Δ4/Δ4) mice showed improper barrier function and ion transport.

Inhibition of airway surface fluid absorption by cholinergic stimulation

PubMed Central

Joo, Nam Soo; Krouse, Mauri E.; Choi, Jae Young; Cho, Hyung-Ju; Wine, Jeffrey J.

2016-01-01

In upper airways airway surface liquid (ASL) depth and clearance rates are both increased by fluid secretion. Secretion is opposed by fluid absorption, mainly via the epithelial sodium channel, ENaC. In static systems, increased fluid depth activates ENaC and decreased depth inhibits it, suggesting that secretion indirectly activates ENaC to reduce ASL depth. We propose an alternate mechanism in which cholinergic input, which causes copious airway gland secretion, also inhibits ENaC-mediated absorption. The conjoint action accelerates clearance, and the increased transport of mucus out of the airways restores ASL depth while cleansing the airways. We were intrigued by early reports of cholinergic inhibition of absorption by airways in some species. To reinvestigate this phenomenon, we studied inward short-circuit currents (Isc) in tracheal mucosa from human, sheep, pig, ferret, and rabbit and in two types of cultured cells. Basal Isc was inhibited 20–70% by the ENaC inhibitor, benzamil. Long-lasting inhibition of ENaC-dependent Isc was also produced by basolateral carbachol in all preparations except rabbit and the H441 cell line. Atropine inhibition produced a slow recovery or prevented inhibition if added before carbachol. The mechanism for inhibition was not determined and is most likely multi-factorial. However, its physiological significance is expected to be increased mucus clearance rates in cholinergically stimulated airways. PMID:26846701

Origins and Transport of Ions during Magnetospheric Substorms

NASA Technical Reports Server (NTRS)

Ashour-Abdalla, Maha; El-Alaoui, Mostafa; Peroomian, Vahe; Raeder, Joachim; Walker, Ray J.; Frank, L. A.; Paterson, W. R.

1999-01-01

We investigate the origins and the transport of ions observed in the near-Earth plasma sheet during the growth and expansion phases of a magnetospheric substorm that occurred on November 24, 1996. Ions observed at Geotail were traced backward in time in time-dependent magnetic and electric fields to determine their origins and the acceleration mechanisms responsible for their energization. Results from this investigation indicate that, during the growth phase of the substorm, most of the ions reaching Geotail had origins in the low latitude boundary layer (LLBL) and had alread@, entered the magnetosphere when the growth phase began. Late in the growth phase and in the expansion phase a higher proportion of the ions reaching Geotail had their origin in the plasma mantle. Indeed, during the expansion phase more than 90% of the ions seen by Geotail were from the mantle. The ions were accelerated enroute to the spacecraft; however, most of the ions' energy gain was achieved by non-adiabatic acceleration while crossing the equatorial current sheet just prior to their detection by Geotail. In general, the plasma mantle from both southern and northern hemispheres supplied non-adiabatic ions to Geotail, whereas the LLBL supplied mostly adiabatic ions to the distributions measured by the spacecraft.

Understanding ion and solvent transport in anion exchange membranes under humidified conditions

NASA Astrophysics Data System (ADS)

Sarode, Himanshu

Anion exchange membranes (AEM) have been studied for more than a decade for potential applications in low temperature fuel cells and other electrochemical devices. They offer the advantage of faster reaction kinetics under alkaline conditions and ability to perform without costly platinum catalyst. Inherently slow diffusion of hydroxide ions compared to protons is a primary reason for synthesizing and studying the ion transport properties in AEMs. The aim of this thesis is to understand ion transport in novel AEMs using Pulse Gradient stimulated Spin Echo Nuclear Magnetic Resonance technique (PGSE NMR), water uptake, ionic conductivity, Small Angle X-ray Scattering (SAXS) etc. All experiments were performed under humidified conditions (80--95% relative humidity) and fuel cell operating temperatures of 30--90°C. In this work, the NMR tube design was modified for humidifying the entire NMR tube evenly from our previous design. We have developed a new protocol for replacing caustic hydroxide with harmless fluoride or bicarbonate ions for 19F and 13 C NMR diffusion experiments. After performing these NMR experiments, we have obtained in-depth understanding of the morphology linked ion transport in AEMs. We have obtained the highest fluoride self-diffusion coefficient of > 1 x 10-5 cm2/sec ( 55°C) for ETFE-g-PVBTMA membrane which is a result of low tortuosity of 1 obtained for the membrane. This faster fluoride transport combined with low tortuosity of the membrane resulted in > 100mS/cm hydroxide conductivity for the membrane. Polycyclooctene (PCOE) based triblock copolymers are also studied for in-depth understanding of molecular weight, IEC, mechanical and transport properties. Effect of melting temperature of PCOE has favorable effect on increasing ion conductivity and lowering activation energy. Mechanical properties of these types of membranes were studied showing detrimental effect of water plasticization which results in unsuitable mechanical properties

The contribution of airway smooth muscle to airway narrowing and airway hyperresponsiveness in disease.

PubMed

Martin, J G; Duguet, A; Eidelman, D H

2000-08-01

Airway hyperresponsiveness (AHR), the exaggerated response to constrictor agonists in asthmatic subjects, is incompletely understood. Changes in either the quantity or properties of airway smooth muscle (ASM) are possible explanations for AHR. Morphometric analyses demonstrate structural changes in asthmatic airways, including subepithelial fibrosis, gland hyperplasia/hypertrophy, neovascularization and an increase in ASM mass. Mathematical modelling of airway narrowing suggests that, of all the changes in structure, the increase in ASM mass is the most probable cause of AHR. An increase in ASM mass in the large airways is more closely associated with a greater likelihood of dying from asthma than increases in ASM mass in other locations within the airway tree. ASM contraction is opposed by the elastic recoil of the lungs and airways, which appears to limit the degree of bronchoconstriction in vivo. The cyclical nature of tidal breathing applies stresses to the airway wall that enhance the bronchodilating influence of the lung tissues on the contracting ASM, in all probability by disrupting cross-bridges. However, the increase in ASM mass in asthma may overcome the limitation resulting from the impedances to ASM shortening imposed by the lung parenchyma and airway wall tissues. Additionally, ASM with the capacity to shorten rapidly may achieve shorter lengths and cause a greater degree of bronchoconstriction when stimulated to contract than slower ASM. Changes in ASM properties are induced by the process of sensitization and allergen-exposure such as enhancement of phospholipase C activity and inositol phosphate turnover, and increases in myosin light chain kinase activity. Whether changes in ASM mass or biochemical/biomechanical properties form the basis for asthma remains to be determined.

Neutron Transport Models and Methods for HZETRN and Coupling to Low Energy Light Ion Transport

NASA Technical Reports Server (NTRS)

Blattnig, S.R.; Slaba, T.C.; Heinbockel, J.H.

2008-01-01

Exposure estimates inside space vehicles, surface habitats, and high altitude aircraft exposed to space radiation are highly influenced by secondary neutron production. The deterministic transport code HZETRN has been identified as a reliable and efficient tool for such studies, but improvements to the underlying transport models and numerical methods are still necessary. In this paper, the forward-backward (FB) and directionally coupled forward-backward (DC) neutron transport models are derived, numerical methods for the FB model are reviewed, and a computationally efficient numerical solution is presented for the DC model. Both models are compared to the Monte Carlo codes HETCHEDS and FLUKA, and the DC model is shown to agree closely with the Monte Carlo results. Finally, it is found in the development of either model that the decoupling of low energy neutrons from the light ion (A<4) transport procedure adversely affects low energy light ion fluence spectra and exposure quantities. A first order correction is presented to resolve the problem, and it is shown to be both accurate and efficient.

Feed gas contaminant removal in ion transport membrane systems

DOEpatents

Underwood, Richard Paul [Allentown, PA; Makitka, III, Alexander; Carolan, Michael Francis [Allentown, PA

2012-04-03

An oxygen ion transport membrane process wherein a heated oxygen-containing gas having one or more contaminants is contacted with a reactive solid material to remove the one or more contaminants. The reactive solid material is provided as a deposit on a support. The one or more contaminant compounds in the heated oxygen-containing gas react with the reactive solid material. The contaminant-depleted oxygen-containing gas is contacted with a membrane, and oxygen is transported through the membrane to provide transported oxygen.

Airway-parenchymal interdependence

PubMed Central

Paré, Peter D; Mitzner, Wayne

2015-01-01

In this manuscript we discuss the interaction of the lung parenchyma and the airways as well as the physiological and pathophysiological significance of this interaction. These two components of the respiratory organ can be thought of as two independent elastic structures but in fact the mechanical properties of one influence the behavior of the other. Traditionally the interaction has focused on the effects of the lung on the airways but there is good evidence that the opposite is also true, i.e., that the mechanical properties of the airways influence the elastic properties of the parenchyma. The interplay between components of the respiratory system including the airways, parenchyma and vasculature is often referred to as “interdependence.” This interdependence transmits the elastic recoil of the lung to create an effective pressure that dilates the airways as transpulmonary pressure and lung volume increase. By using a continuum mechanics analysis of the lung parenchyma, it is possible to predict the effective pressure between the airways and parenchyma, and these predictions can be empirically evaluated. Normal airway caliber is maintained by this pressure in the adventitial interstitium of the airway, and it counteracts airway compression during forced expiration as well as the ability of airway smooth muscle to narrow airways. Interdependence has physiological and pathophysiological significance. Weakening of the forces of interdependence contributes to airway dysfunction and gas exchange impairment in acute and chronic airway diseases including asthma and emphysema. PMID:23723029

Debris buster is a Drosophila scavenger receptor essential for airway physiology.

PubMed

Wingen, Almut; Carrera, Pilar; Ekaterini Psathaki, Olympia; Voelzmann, André; Paululat, Achim; Hoch, Michael

2017-10-01

Scavenger receptors class B (SR-B) are multifunctional transmembrane proteins, which in vertebrates participate in lipid transport, pathogen clearance, lysosomal delivery and intracellular sorting. Drosophila has 14 SR-B members whose functions are still largely unknown. Here, we reveal a novel role for the SR-B family member Debris buster (Dsb) in Drosophila airway physiology. Larvae lacking dsb show yeast avoidance behavior, hypoxia, and severe growth defects associated with impaired elongation and integrity along the airways. Furthermore, in dsb mutant embryos, the barrier function of the posterior spiracles, which are critical for gas exchange, is not properly established and liquid clearance is locally impaired at the spiracular lumen. We found that Dsb is specifically expressed in a group of distal epithelial cells of the posterior spiracle organ and not throughout the entire airways. Furthermore, tissue-specific knockdown and rescue experiments demonstrate that Dsb function in the airways is only required in the posterior spiracles. Dsb localizes in intracellular vesicles, and a subset of these associate with lysosomes. However, we found that depletion of proteins involved in vesicular transport to the apical membrane, but not in lysosomal function, causes dsb-like airway elongation defects. We propose a model in which Dsb sorts components of the apical extracellular matrix which are essential for airway physiology. Since SR-B LIMP2-deficient mice show reduced expression of several apical plasma membrane proteins, sorting of proteins to the apical membrane is likely an evolutionary conserved function of Dsb and LIMP2. Our data provide insights into a spatially confined function of the SR-B Dsb in intracellular trafficking critical for the physiology of the whole tubular airway network. Copyright © 2017 Elsevier Inc. All rights reserved.

SERCA2 Regulates Non-CF and CF Airway Epithelial Cell Response to Ozone

PubMed Central

Ahmad, Shama; Nichols, David P.; Strand, Matthew; Rancourt, Raymond C.; Randell, Scott H.; White, Carl W.; Ahmad, Aftab

2011-01-01

Calcium mobilization can regulate a wide range of essential functions of respiratory epithelium, including ion transport, ciliary beat frequency, and secretion of mucus, all of which are modified in cystic fibrosis (CF). SERCA2, an important controller of calcium signaling, is deficient in CF epithelium. We conducted this study to determine whether SERCA2 deficiency can modulate airway epithelial responses to environmental oxidants such as ozone. This could contribute to the pathogenesis of pulmonary exacerbations, which are important and frequent clinical events in CF. To address this, we used air-liquid interface (ALI) cultures of non-CF and CF cell lines, as well as differentiated cultures of cells derived from non-CF and CF patients. We found that ozone exposure caused enhanced membrane damage, mitochondrial dysfunction and apoptotic cell death in CF airway epithelial cell lines relative to non-CF. Ozone exposure caused increased proinflammatory cytokine production in CF airway epithelial cell lines. Elevated proinflammatory cytokine production also was observed in shRNA-mediated SERCA2 knockdown cells. Overexpression of SERCA2 reversed ozone-induced proinflammatory cytokine production. Ozone-induced proinflammatory cytokine production was NF-κB- dependent. In a stable NF-κB reporter cell line, SERCA2 inhibition and knockdown both upregulated cytomix-induced NF-κB activity, indicating importance of SERCA2 in modulating NF-κB activity. In this system, increased NF-κB activity was also accompanied by increased IL-8 production. Ozone also induced NF-κB activity and IL-8 release, an effect that was greater in SERCA2-silenced NF-κB-reporter cells. SERCA2 overexpression reversed cytomix-induced increased IL-8 release and total nuclear p65 in CFTR-deficient (16HBE-AS) cells. These studies suggest that SERCA2 is an important regulator of the proinflammatory response of airway epithelial cells and could be a potential therapeutic target. PMID:22096575

Ion transport and selectivity in biomimetic nanopores with pH-tunable zwitterionic polyelectrolyte brushes.

PubMed

Zeng, Zhenping; Yeh, Li-Hsien; Zhang, Mingkan; Qian, Shizhi

2015-10-28

Inspired by nature, functionalized nanopores with biomimetic structures have attracted growing interests in using them as novel platforms for applications of regulating ion and nanoparticle transport. To improve these emerging applications, we study theoretically for the first time the ion transport and selectivity in short nanopores functionalized with pH tunable, zwitterionic polyelectrolyte (PE) brushes. In addition to background salt ions, the study takes into account the presence of H(+) and OH(-) ions along with the chemistry reactions between functional groups on PE chains and protons. Due to ion concentration polarization, the charge density of PE layers is not homogeneously distributed and depends significantly on the background salt concentration, pH, grafting density of PE chains, and applied voltage bias, thereby resulting in many interesting and unexpected ion transport phenomena in the nanopore. For example, the ion selectivity of the biomimetic nanopore can be regulated from anion-selective (cation-selective) to cation-selective (anion-selective) by diminishing (raising) the solution pH when a sufficiently small grafting density of PE chains, large voltage bias, and low background salt concentration are applied.

A Green's function method for heavy ion beam transport

NASA Technical Reports Server (NTRS)

Shinn, J. L.; Wilson, J. W.; Schimmerling, W.; Shavers, M. R.; Miller, J.; Benton, E. V.; Frank, A. L.; Badavi, F. F.

1995-01-01

The use of Green's function has played a fundamental role in transport calculations for high-charge high-energy (HZE) ions. Two recent developments have greatly advanced the practical aspects of implementation of these methods. The first was the formulation of a closed-form solution as a multiple fragmentation perturbation series. The second was the effective summation of the closed-form solution through nonperturbative techniques. The nonperturbative methods have been recently extended to an inhomogeneous, two-layer transport media to simulate the lead scattering foil present in the Lawrence Berkeley Laboratories (LBL) biomedical beam line used for cancer therapy. Such inhomogeneous codes are necessary for astronaut shielding in space. The transport codes utilize the Langley Research Center atomic and nuclear database. Transport code and database evaluation are performed by comparison with experiments performed at the LBL Bevalac facility using 670 A MeV 20Ne and 600 A MeV 56Fe ion beams. The comparison with a time-of-flight and delta E detector measurement for the 20Ne beam and the plastic nuclear track detectors for 56Fe show agreement up to 35%-40% in water and aluminium targets, respectively.

Electrogenic transport and K+ ion channel expression by the human endolymphatic sac epithelium

PubMed Central

Kim, Sung Huhn; Kim, Bo Gyung; Kim, Jin Young; Roh, Kyung Jin; Suh, Michelle J.; Jung, JinSei; Moon, In Seok; Moon, Sung K.; Choi, Jae Young

2015-01-01

The endolymphatic sac (ES) is a cystic organ that is a part of the inner ear and is connected to the cochlea and vestibule. The ES is thought to be involved in inner ear ion homeostasis and fluid volume regulation for the maintenance of hearing and balance function. Many ion channels, transporters, and exchangers have been identified in the ES luminal epithelium, mainly in animal studies, but there has been no functional study investigating ion transport using human ES tissue. We designed the first functional experiments on electrogenic transport in human ES and investigated the contribution of K+ channels in the electrogenic transport, which has been rarely identified, even in animal studies, using electrophysiological/pharmacological and molecular biological methods. As a result, we identified functional and molecular evidence for the essential participation of K+ channels in the electrogenic transport of human ES epithelium. The identified K+ channels involved in the electrogenic transport were KCNN2, KCNJ14, KCNK2, and KCNK6, and the K+ transports via those channels are thought to play an important role in the maintenance of the unique ionic milieu of the inner ear fluid. PMID:26655723

Airway Surface Dehydration Aggravates Cigarette Smoke-Induced Hallmarks of COPD in Mice.

PubMed

Seys, Leen J M; Verhamme, Fien M; Dupont, Lisa L; Desauter, Elke; Duerr, Julia; Seyhan Agircan, Ayca; Conickx, Griet; Joos, Guy F; Brusselle, Guy G; Mall, Marcus A; Bracke, Ken R

2015-01-01

Airway surface dehydration, caused by an imbalance between secretion and absorption of ions and fluid across the epithelium and/or increased epithelial mucin secretion, impairs mucociliary clearance. Recent evidence suggests that this mechanism may be implicated in chronic obstructive pulmonary disease (COPD). However, the role of airway surface dehydration in the pathogenesis of cigarette smoke (CS)-induced COPD remains unknown. We aimed to investigate in vivo the effect of airway surface dehydration on several CS-induced hallmarks of COPD in mice with airway-specific overexpression of the β-subunit of the epithelial Na⁺ channel (βENaC). βENaC-Tg mice and wild-type (WT) littermates were exposed to air or CS for 4 or 8 weeks. Pathological hallmarks of COPD, including goblet cell metaplasia, mucin expression, pulmonary inflammation, lymphoid follicles, emphysema and airway wall remodelling were determined and lung function was measured. Airway surface dehydration in βENaC-Tg mice aggravated CS-induced airway inflammation, mucin expression and destruction of alveolar walls and accelerated the formation of pulmonary lymphoid follicles. Moreover, lung function measurements demonstrated an increased compliance and total lung capacity and a lower resistance and hysteresis in βENaC-Tg mice, compared to WT mice. CS exposure further altered lung function measurements. We conclude that airway surface dehydration is a risk factor that aggravates CS-induced hallmarks of COPD.

RENAL TUBULAR TRANSPORT OF INORGANIC DIVALENT IONS BY THE AGLOMERULAR MARINE TELEOST, LOPHIUS AMERICANUS

PubMed Central

Berglund, Fredrik; Forster, Roy P.

1958-01-01

A characterization was attempted of the mechanisms involved in the tubular transport of inorganic divalent ions by the aglomerular kidney of Lophius, attention being paid particularly to the possible existence of transport maxima (Tm) and to competition for transport among related substances undergoing tubular excretion. Excretory rates of divalent ions in non-treated fish during standard laboratory conditions paralleled spontaneous changes in urine flow. Tm rates of excretion were reached for magnesium, sulfate, and thiosulfate with corresponding plasma levels of 2 to 5, 5 to 17, and 4 to 12 µM/ml. respectively. Elevation of magnesium chloride levels in plasma markedly depressed calcium excretion; sodium thiosulfate similarly depressed sulfate excretion. Experimental observations suggest the existence of a transport system for divalent cations separate from another for divalent anions. Within each transport system the ion with the higher excretion rate depressed competitively transfer of the other ion. Neither system was influenced by probenecid (benemid) in doses which markedly depressed the simultaneous excretion rate of p-aminohippuric acid. PMID:13491814

Visualization and quantification of transmembrane ion transport into giant unilamellar vesicles.

PubMed

Valkenier, Hennie; López Mora, Néstor; Kros, Alexander; Davis, Anthony P

2015-02-09

Transmembrane ion transporters (ionophores) are widely investigated as supramolecular agents with potential for biological activity. Tests are usually performed in synthetic membranes that are assembled into large unilamellar vesicles (LUVs). However transport must be followed through bulk properties of the vesicle suspension, because LUVs are too small for individual study. An alternative approach is described whereby ion transport can be revealed and quantified through direct observation. The method employs giant unilamellar vesicles (GUVs), which are 20-60 μm in diameter and readily imaged by light microscopy. This allows characterization of individual GUVs containing transporter molecules, followed by studies of transport through fluorescence emission from encapsulated indicators. The method provides new levels of certainty and relevance, given that the GUVs are similar in size to living cells. It has been demonstrated using a highly active anion carrier, and should aid the development of compounds for treating channelopathies such as cystic fibrosis. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ion age transport: developing devices beyond electronics

NASA Astrophysics Data System (ADS)

Demming, Anna

2014-03-01

There is more to current devices than conventional electronics. Increasingly research into the controlled movement of ions and molecules is enabling a range of new technologies. For example, as Weihua Guan, Sylvia Xin Li and Mark Reed at Yale University explain, 'It offers a unique opportunity to integrate wet ionics with dry electronics seamlessly'. In this issue they provide an overview of voltage-gated ion and molecule transport in engineered nanochannels. They cover the theory governing these systems and fabrication techniques, as well as applications, including biological and chemical analysis, and energy conversion [1]. Studying the movement of particles in nanochannels is not new. The transport of materials in rock pores led Klinkenberg to describe an analogy between diffusion and electrical conductivity in porous rocks back in 1951 [2]. And already in 1940, Harold Abramson and Manuel Gorin noted that 'When an electric current is applied across the living human skin, the skin may be considered to act like a system of pores through which transfer of substances like ragweed pollen extract may be achieved both by electrophoretic and by diffusion phenomena' [3]. Transport in living systems through pore structures on a much smaller scale has attracted a great deal of research in recent years as well. The selective transport of ions and small organic molecules across the cell membrane facilitates a number of functions including communication between cells, nerve conduction and signal transmission. Understanding these processes may benefit a wide range of potential applications such as selective separation, biochemical sensing, and controlled release and drug delivery processes. In Germany researchers have successfully demonstrated controlled ionic transport through nanopores functionalized with amine-terminated polymer brushes [4]. The polymer nanobrushes swell and shrink in response to changes in temperature, thus opening and closing the nanopore passage to ionic

Trefoil factor-2 reverses airway remodeling changes in allergic airways disease.

PubMed

Royce, Simon G; Lim, Clarice; Muljadi, Ruth C; Samuel, Chrishan S; Ververis, Katherine; Karagiannis, Tom C; Giraud, Andrew S; Tang, Mimi L K

2013-01-01

Trefoil factor 2 (TFF2) is a small peptide with an important role in mucosal repair. TFF2 is up-regulated in asthma, suggesting a role in asthma pathogenesis. Given its known biological role in promoting epithelial repair, TFF2 might be expected to exert a protective function in limiting the progression of airway remodeling in asthma. The contribution of TFF2 to airway remodeling in asthma was investigated by examining the expression of TFF2 in the airway and lung, and evaluating the effects of recombinant TFF2 treatment on established airway remodeling in a murine model of chronic allergic airways disease (AAD). BALB/c mice were sensitized and challenged with ovalbumin (OVA) or saline for 9 weeks, whereas mice with established OVA-induced AAD were treated with TFF2 or vehicle control (intranasally for 14 d). Effects on airway remodeling, airway inflammation, and airway hyperresponsiveness were then assessed, whereas TFF2 expression was determined by immunohistochemistry. TFF2 expression was significantly increased in the airways of mice with AAD, compared with expression levels in control mice. TFF2 treatment resulted in reduced epithelial thickening, subepithelial collagen deposition, goblet-cell metaplasia, bronchial epithelium apoptosis, and airway hyperresponsiveness (all P < 0.05, versus vehicle control), but TFF2 treatment did not influence airway inflammation. The increased expression of endogenous TFF2 in response to chronic allergic inflammation is insufficient to prevent the progression of airway inflammation and remodeling in a murine model of chronic AAD. However, exogenous TFF2 treatment is effective in reversing aspects of established airway remodeling. TFF2 has potential as a novel treatment for airway remodeling in asthma.

Enamel: Molecular identity of its transepithelial ion transport system.

PubMed

Lacruz, Rodrigo S

2017-07-01

Enamel is the most calcified tissue in vertebrates. It differs from bone in a number of characteristics including its origin from ectodermal epithelium, lack of remodeling capacity by the enamel forming cells, and absence of collagen. The enamel-forming cells known as ameloblasts, choreograph first the synthesis of a unique protein-rich matrix, followed by the mineralization of this matrix into a tissue that is ∼95% mineral. To do this, ameloblasts arrange the coordinated movement of ions across a cell barrier while removing matrix proteins and monitoring extracellular pH using a variety of buffering systems to enable the growth of carbonated apatite crystals. Although our knowledge of these processes and the molecular identity of the proteins involved in transepithelial ion transport has increased in the last decade, it remains limited compared to other cells. Here we present an overview of the evolution and development of enamel, its differences with bone, and describe the ion transport systems associated with ameloblasts. Copyright © 2017 The Author. Published by Elsevier Ltd.. All rights reserved.

Sodium ion-dependent amino acid transport in membrane vesicles of Bacillus stearothermophilus.

PubMed Central

Heyne, R I; de Vrij, W; Crielaard, W; Konings, W N

1991-01-01

Amino acid transport in membrane vesicles of Bacillus stearothermophilus was studied. A relatively high concentration of sodium ions is needed for uptake of L-alanine (Kt = 1.0 mM) and L-leucine (Kt = 0.4 mM). In contrast, the Na(+)-H(+)-L-glutamate transport system has a high affinity for sodium ions (Kt less than 5.5 microM). Lithium ions, but no other cations tested, can replace sodium ions in neutral amino acid transport. The stimulatory effect of monensin on the steady-state accumulation level of these amino acids and the absence of transport in the presence of nonactin indicate that these amino acids are translocated by a Na+ symport mechanism. This is confirmed by the observation that an artificial delta psi and delta mu Na+/F but not a delta pH can act as a driving force for uptake. The transport system for L-alanine is rather specific. L-Serine, but not L-glycine or other amino acids tested, was found to be a competitive inhibitor of L-alanine uptake. On the other hand, the transport carrier for L-leucine also translocates the amino acids L-isoleucine and L-valine. The initial rates of L-glutamate and L-alanine uptake are strongly dependent on the medium pH. The uptake rates of both amino acids are highest at low external pH (5.5 to 6.0) and decline with increasing pH. The pH allosterically affects the L-glutamate and L-alanine transport systems. The maximal rate of L-glutamate uptake (Vmax) is independent of the external pH between pH 5.5 and 8.5, whereas the affinity constant (Kt) increases with increasing pH. A specific transport system for the basic amino acids L-lysine and L-arginine in the membrane vesicles has also been observed. Transport of these amino acids occurs most likely by a uniport mechanism. PMID:1670936

Transport of Helium Pickup Ions within the Focusing Cone: Reconciling STEREO Observations with IBEX

NASA Astrophysics Data System (ADS)

Quinn, P. R.; Schwadron, N. A.; Möbius, E.

2016-06-01

Recent observations of the pickup helium focusing cone by STEREO/Plasma and Suprathermal Ion Composition indicate an inflow longitude of the interstellar wind that differs from the observations of IBEX by 1\\buildrel{\\circ}\\over{.} 8+/- 2\\buildrel{\\circ}\\over{.} 4. It has been under debate whether the transport of helium pickup ions with an anisotropic velocity distribution is the cause of this difference. If so, the roughly field-aligned pickup ion streaming relative to the solar wind should create a shift in the pickup ion density relative to the focusing cone. A large pickup ion streaming depends on the size of the mean free path. Therefore, the observed longitudinal shift in the pickup ion density relative to the neutral focusing cone may carry fundamental information about the mean free path experienced by pickup ions inside 1 au. We test this hypothesis using the Energetic Particle Radiation Environment Module (EPREM) model by simulating the transport of helium pickup ions within the focusing cone finding a mean free path of {λ }\\parallel =0.19+0.29(-0.19) au. We calculate the average azimuthal velocity of pickup ions and find that the anisotropic distribution reaches ˜8% of the solar wind speed. Lastly, we isolate transport effects within EPREM, finding that pitch-angle scattering, adiabatic focusing, perpendicular diffusion, and particle drift contribute to shifting the focusing cone 20.00%, 69.43%, 10.56%, and \\lt 0.01 % , respectively. Thus we show with the EPREM model that the transport of pickup ions does indeed shift the peak of the focusing cone relative to the progenitor neutral atoms and this shift provides fundamental information on the scattering of pickup ions inside 1 au.

Ion Binding Energies Determining Functional Transport of ClC Proteins

NASA Astrophysics Data System (ADS)

Yu, Tao; Guo, Xu; Zou, Xian-Wu; Sang, Jian-Ping

2014-06-01

The ClC-type proteins, a large family of chloride transport proteins ubiquitously expressed in biological organisms, have been extensively studied for decades. Biological function of ClC proteins can be reflected by analyzing the binding situation of Cl- ions. We investigate ion binding properties of ClC-ec1 protein with the atomic molecular dynamics simulation approach. The calculated electrostatic binding energy results indicate that Cl- at the central binding site Scen has more binding stability than the internal binding site Sint. Quantitative comparison between the latest experimental heat release data isothermal titration calorimetry (ITC) and our calculated results demonstrates that chloride ions prefer to bind at Scen than Sint in the wild-type ClC-ec1 structure and prefer to bind at Sext and Scen than Sint in mutant E148A/E148Q structures. Even though the chloride ions make less contribution to heat release when binding to Sint and are relatively unstable in the Cl- pathway, they are still part contributors for the Cl- functional transport. This work provides a guide rule to estimate the importance of Cl- at the binding sites and how chloride ions have influences on the function of ClC proteins.

HOL1 mutations confer novel ion transport in Saccharomyces cerevisiae.

PubMed Central

Gaber, R F; Kielland-Brandt, M C; Fink, G R

1990-01-01

Saccharomyces cerevisiae histidine auxotrophs are unable to use L-histidinol as a source of histidine even when they have a functional histidinol dehydrogenase. Mutations in the hol1 gene permit growth of His- cells on histidinol by enhancing the ability of cells to take up histidinol from the medium. Second-site mutations linked to HOL1-1 further increase histidinol uptake. HOL1 double mutants and, to a lesser extent, HOL1-1 single mutants show hypersensitivity to specific cations added to the growth medium, including Na+, Li+, Cs+, Be2+, guanidinium ion, and histidinol, but not K+, Rb+, Ca2+, or Mg2+. The Na(+)-hypersensitive phenotype is correlated with increased uptake and accumulation of this ion. The HOL1-1-101 gene was cloned and used to generate a viable haploid strain containing a hol1 deletion mutation (hol1 delta). The uptake of cations, the dominance of the mutant alleles, and the relative inability of hol1 delta cells to take up histidinol or Na+ suggest that hol1 encodes an ion transporter. The novel pattern of ion transport conferred by HOL1-1 and HOL1-1-101 mutants may be explained by reduced selectivity for the permeant ions. Images PMID:2405251

Ion transport its regulation in the endolymphatic sac: suggestions for clinical aspects of Meniere's disease.

PubMed

Mori, Nozomu; Miyashita, Takenori; Inamoto, Ryuhei; Matsubara, Ai; Mori, Terushige; Akiyama, Kosuke; Hoshikawa, Hiroshi

2017-04-01

Ion transport and its regulation in the endolymphatic sac (ES) are reviewed on the basis of recent lines of evidence. The morphological and physiological findings demonstrate that epithelial cells in the intermediate portion of the ES are more functional in ion transport than those in the other portions. Several ion channels, ion transporters, ion exchangers, and so on have been reported to be present in epithelial cells of ES intermediate portion. An imaging study has shown that mitochondria-rich cells in the ES intermediate portion have a higher activity of Na + , K + -ATPase and a higher Na + permeability than other type of cells, implying that molecules related to Na + transport, such as epithelial sodium channel (ENaC), Na + -K + -2Cl - cotransporter 2 (NKCC2) and thiazide-sensitive Na + -Cl - cotransporter (NCC), may be present in mitochondria-rich cells. Accumulated lines of evidence suggests that Na + transport is most important in the ES, and that mitochondria-rich cells play crucial roles in Na + transport in the ES. Several lines of evidence support the hypothesis that aldosterone may regulate Na + transport in ES, resulting in endolymph volume regulation. The presence of molecules related to acid/base transport, such as H + -ATPase, Na + -H + exchanger (NHE), pendrin (SLC26A4), Cl - -HCO 3 - exchanger (SLC4A2), and carbonic anhydrase in ES epithelial cells, suggests that acid/base transport is another important one in the ES. Recent basic and clinical studies suggest that aldosterone may be involved in the effect of salt-reduced diet treatment in Meniere's disease.

Initial Binding of Ions to the Interhelical Loops of Divalent Ion Transporter CorA: Replica Exchange Molecular Dynamics Simulation Study

PubMed Central

Zhang, Tong; Mu, Yuguang

2012-01-01

Crystal structures of Thermotoga maritima magnesium transporter CorA, reported in 2006, revealed its homo-pentameric constructions. However, the structure of the highly conserved extracellular interhelical loops remains unsolved, due to its high flexibility. We have explored the configurations of the loops through extensive replica exchange molecular dynamics simulations in explicit solvent model with the presence of either Co(III) Hexamine ions or Mg2+ ions. We found that there are multiple binding sites available on the interhelical loops in which the negatively charged residues, E316 and E320, are located notably close to the positively charged ions during the simulations. Our simulations resolved the distinct binding patterns of the two kinds of ions: Co(III) Hexamine ions were found to bind stronger with the loop than Mg2+ ions with binding free energy −7.3 kJ/mol lower, which is nicely consistent with the previous data. Our study provides an atomic basis description of the initial binding process of Mg2+ ions on the extracellular interhelical loops of CorA and the detailed inhibition mechanism of Co(III) Hexamine ions on CorA ions transportation. PMID:22952795

A parallel finite element simulator for ion transport through three-dimensional ion channel systems.

PubMed

Tu, Bin; Chen, Minxin; Xie, Yan; Zhang, Linbo; Eisenberg, Bob; Lu, Benzhuo

2013-09-15

A parallel finite element simulator, ichannel, is developed for ion transport through three-dimensional ion channel systems that consist of protein and membrane. The coordinates of heavy atoms of the protein are taken from the Protein Data Bank and the membrane is represented as a slab. The simulator contains two components: a parallel adaptive finite element solver for a set of Poisson-Nernst-Planck (PNP) equations that describe the electrodiffusion process of ion transport, and a mesh generation tool chain for ion channel systems, which is an essential component for the finite element computations. The finite element method has advantages in modeling irregular geometries and complex boundary conditions. We have built a tool chain to get the surface and volume mesh for ion channel systems, which consists of a set of mesh generation tools. The adaptive finite element solver in our simulator is implemented using the parallel adaptive finite element package Parallel Hierarchical Grid (PHG) developed by one of the authors, which provides the capability of doing large scale parallel computations with high parallel efficiency and the flexibility of choosing high order elements to achieve high order accuracy. The simulator is applied to a real transmembrane protein, the gramicidin A (gA) channel protein, to calculate the electrostatic potential, ion concentrations and I - V curve, with which both primitive and transformed PNP equations are studied and their numerical performances are compared. To further validate the method, we also apply the simulator to two other ion channel systems, the voltage dependent anion channel (VDAC) and α-Hemolysin (α-HL). The simulation results agree well with Brownian dynamics (BD) simulation results and experimental results. Moreover, because ionic finite size effects can be included in PNP model now, we also perform simulations using a size-modified PNP (SMPNP) model on VDAC and α-HL. It is shown that the size effects in SMPNP can

(In)validity of the constant field and constant currents assumptions in theories of ion transport.

PubMed Central

Syganow, A; von Kitzing, E

1999-01-01

Constant electric fields and constant ion currents are often considered in theories of ion transport. Therefore, it is important to understand the validity of these helpful concepts. The constant field assumption requires that the charge density of permeant ions and flexible polar groups is virtually voltage independent. We present analytic relations that indicate the conditions under which the constant field approximation applies. Barrier models are frequently fitted to experimental current-voltage curves to describe ion transport. These models are based on three fundamental characteristics: a constant electric field, negligible concerted motions of ions inside the channel (an ion can enter only an empty site), and concentration-independent energy profiles. An analysis of those fundamental assumptions of barrier models shows that those approximations require large barriers because the electrostatic interaction is strong and has a long range. In the constant currents assumption, the current of each permeating ion species is considered to be constant throughout the channel; thus ion pairing is explicitly ignored. In inhomogeneous steady-state systems, the association rate constant determines the strength of ion pairing. Among permeable ions, however, the ion association rate constants are not small, according to modern diffusion-limited reaction rate theories. A mathematical formulation of a constant currents condition indicates that ion pairing very likely has an effect but does not dominate ion transport. PMID:9929480

Quasi-equilibrium analysis of the ion-pair mediated membrane transport of low-permeability drugs.

PubMed

Miller, Jonathan M; Dahan, Arik; Gupta, Deepak; Varghese, Sheeba; Amidon, Gordon L

2009-07-01

The aim of this research was to gain a mechanistic understanding of ion-pair mediated membrane transport of low-permeability drugs. Quasi-equilibrium mass transport analyses were developed to describe the ion-pair mediated octanol-buffer partitioning and hydrophobic membrane permeation of the model basic drug phenformin. Three lipophilic counterions were employed: p-toluenesulfonic acid, 2-naphthalenesulfonic acid, and 1-hydroxy-2-naphthoic acid (HNAP). Association constants and intrinsic octanol-buffer partition coefficients (Log P(AB)) of the ion-pairs were obtained by fitting a transport model to double reciprocal plots of apparent octanol-buffer distribution coefficients versus counterion concentration. All three counterions enhanced the lipophilicity of phenformin, with HNAP providing the greatest increase in Log P(AB), 3.7 units over phenformin alone. HNAP also enhanced the apparent membrane permeability of phenformin, 27-fold in the PAMPA model, and 4.9-fold across Caco-2 cell monolayers. As predicted from a quasi-equilibrium analysis of ion-pair mediated membrane transport, an order of magnitude increase in phenformin flux was observed per log increase in counterion concentration, such that log-log plots of phenformin flux versus HNAP concentration gave linear relationships. These results provide increased understanding of the underlying mechanisms of ion-pair mediated membrane transport, emphasizing the potential of this approach to enable oral delivery of low-permeability drugs.

Endocrine regulation of airway contractility is overlooked.

PubMed

Bossé, Ynuk

2014-08-01

Asthma is a prevalent respiratory disorder triggered by a variety of inhaled environmental factors, such as allergens, viruses, and pollutants. Asthma is characterized by an elevated activation of the smooth muscle surrounding the airways, as well as a propensity of the airways to narrow excessively in response to a spasmogen (i.e. contractile agonist), a feature called airway hyperresponsiveness. The level of airway smooth muscle (ASM) activation is putatively controlled by mediators released in its vicinity. In asthma, many mediators that affect ASM contractility originate from inflammatory cells that are mobilized into the airways, such as eosinophils. However, mounting evidence indicates that mediators released by remote organs can also influence the level of activation of ASM, as well as its level of responsiveness to spasmogens and relaxant agonists. These remote mediators are transported through circulating blood to act either directly on ASM or indirectly via the nervous system by tuning the level of cholinergic activation of ASM. Indeed, mediators generated from diverse organs, including the adrenals, pancreas, adipose tissue, gonads, heart, intestines, and stomach, affect the contractility of ASM. Together, these results suggest that, apart from a paracrine mode of regulation, ASM is subjected to an endocrine mode of regulation. The results also imply that defects in organs other than the lungs can contribute to asthma symptoms and severity. In this review, I suggest that the endocrine mode of regulation of ASM contractility is overlooked. © 2014 Society for Endocrinology.

Effect of guaifenesin on mucin production, rheology, and mucociliary transport in differentiated human airway epithelial cells.

PubMed

Seagrave, JeanClare; Albrecht, Helmut; Park, Yong Sung; Rubin, Bruce; Solomon, Gail; Kim, K Chul

2011-12-01

Guaifenesin is widely used to alleviate symptoms of excessive mucus accumulation in the respiratory tract. However, its mechanism of action is poorly understood. The authors hypothesized that guaifenesin improves mucociliary clearance in humans by reducing mucin release, by decreasing mucus viscoelasticity, and by increasing mucociliary transport. To test these hypotheses, human differentiated airway epithelial cells, cultured at an air-liquid interface, were treated with clinically relevant concentrations of guaifenesin by addition to the basolateral medium. To evaluate the effect on mucin secretion, the authors used an anzyme-linked immunosorbent assay (ELISA) to measure the amounts of MUC5AC protein in apical surface fluid and cell lysates. To measure mucociliary transportability, additional cultures were treated for 1 or 6 hours with guaifenesin, and the movement of cell debris was measured from video data. Further, the authors measured mucus dynamic viscoelasticity using a micro cone and plate rheometer with nondestructive creep transformation. Guaifenesin suppressed mucin production in a dose-dependent manner at clinically relevant concentrations. The reduced mucin production was associated with increased mucociliary transport and decreased viscoelasticity of the mucus. Viability of the cultures was not significantly affected. These results suggest that guaifenesin could improve mucociliary clearance in humans by reducing the release and/or production of mucins, thereby altering mucus rheology.

Bradykinin regulates human colonic ion transport in vitro

PubMed Central

Baird, A W; Skelly, M M; O'Donoghue, D P; Barrett, K E; Keely, S J

2008-01-01

Background and purpose: Kinins are acknowledged as important regulators of intestinal function during inflammation; however, their effects on human intestinal ion transport have not been reported. Here, we used muscle-stripped human colonic tissue and cultured T84-cell monolayers to study bradykinin (BK) actions on human intestinal ion transport. Experimental approach: Ion transport was measured as changes in short-circuit current (Isc) across colonic epithelia mounted in Ussing chambers. Key results: In intact tissue, there was a distinct polarity to BK-elicited Isc responses. Whereas basolateral BK stimulated sustained responses (EC50=0.5±0.1 μM), those to apical BK were more rapid and transient (EC50=4.1±1.2 nM). In T84 cells, responses to both apical and basolateral BK were similar to those seen upon apical addition to intact tissues. Cross-desensitization between apical and basolateral domains was not observed. BK-induced responses were largely due to Cl− secretion as shown by their sensitivity to bumetanide and removal of Cl− from the bathing solution. Studies using selective agonists and antagonists indicate responses to BK are mediated by B2 receptors. Finally, responses to basolateral BK in intact tissues were inhibited by tetrodotoxin (1 μM), atropine (1 μM), capsaicin (100 μM) and piroxicam (10 μM). BK-stimulated prostaglandin (PG)E2 release from colonic tissue. Conclusions: BK stimulates human colonic Cl− secretion by activation of apical and basolateral B2 receptors. Responses to apical BK reflect a direct action on epithelial cells, whereas those to basolateral BK are amplified by stimulation of enteric nerves and PG synthesis. PMID:18604228

Stormtime ring current and radiation belt ion transport: Simulations and interpretations

NASA Technical Reports Server (NTRS)

Lyons, Larry R.; Gorney, David J.; Chen, Margaret W.; Schulz, Michael

1995-01-01

We use a dynamical guiding-center model to investigate the stormtime transport of ring current and radiation-belt ions. We trace the motion of representative ions' guiding centers in response to model substorm-associated impulses in the convection electric field for a range of ion energies. Our simple magnetospheric model allows us to compare our numerical results quantitatively with analytical descriptions of particle transport, (e.g., with the quasilinear theory of radial diffusion). We find that 10-145-keV ions gain access to L approximately 3, where they can form the stormtime ring current, mainly from outside the (trapping) region in which particles execute closed drift paths. Conversely, the transport of higher-energy ions (approximately greater than 145 keV at L approximately 3) turns out to resemble radial diffusion. The quasilinear diffusion coefficient calculated for our model storm does not vary smoothly with particle energy, since our impulses occur at specific (although randomly determined) times. Despite the spectral irregularity, quasilinear theory provides a surprisingly accurate description of the transport process for approximately greater than 145-keV ions, even for the case of an individual storm. For 4 different realizations of our model storm, the geometric mean discrepancies between diffusion coefficients D(sup sim, sub LL) obtained from the simulations and the quasilinear diffusion coefficient D(sup ql, sub LL) amount to factors of 2.3, 2.3, 1.5, and 3.0, respectively. We have found that these discrepancies between D(sup sim, sub LL) and D(sup ql, sub LL) can be reduced slightly by invoking drift-resonance broadening to smooth out the sharp minima and maxima in D(sup ql, sub LL). The mean of the remaining discrepancies between D(sup sim, sub LL) and D(sup ql, sub LL) for the 4 different storms then amount to factors of 1.9, 2.1, 1.5, and 2.7, respectively. We find even better agreement when we reduce the impulse amplitudes systematically in

Electric Field-Controlled Ion Transport In TiO2 Nanochannel.

PubMed

Li, Dan; Jing, Wenheng; Li, Shuaiqiang; Shen, Hao; Xing, Weihong

2015-06-03

On the basis of biological ion channels, we constructed TiO2 membranes with rigid channels of 2.3 nm to mimic biomembranes with flexible channels; an external electric field was employed to regulate ion transport in the confined channels at a high ionic strength in the absence of electrical double layer overlap. Results show that transport rates for both Na+ and Mg2+ were decreased irrespective of the direction of the electric field. Furthermore, a voltage-gated selective ion channel was formed, the Mg2+ channel closed at -2 V, and a reversed relative electric field gradient was at the same order of the concentration gradient, whereas the Na+ with smaller Stokes radius and lower valence was less sensitive to the electric field and thus preferentially occupied and passed the channel. Thus, when an external electric field is applied, membranes with larger nanochannels have promising applications in selective separation of mixture salts at a high concentration.

Sugar-activated ion transport in canine lingual epithelium. Implications for sugar taste transduction

PubMed Central

1988-01-01

There is good evidence indicating that ion-transport pathways in the apical regions of lingual epithelial cells, including taste bud cells, may play a role in salt taste reception. In this article, we present evidence that, in the case of the dog, there also exists a sugar- activated ion-transport pathway that is linked to sugar taste transduction. Evidence was drawn from two parallel lines of experiments: (a) ion-transport studies on the isolated canine lingual epithelium, and (b) recordings from the canine chorda tympani. The results in vitro showed that both mono- and disaccharides in the mucosal bath stimulate a dose-dependent increase in the short-circuit current over the concentration range coincident with mammalian sugar taste responses. Transepithelial current evoked by glucose, fructose, or sucrose in either 30 mM NaCl or in Krebs-Henseleit buffer (K-H) was partially blocked by amiloride. Among current carriers activated by saccharides, the current response was greater with Na than with K. Ion flux measurements in K-H during stimulation with 3-O-methylglucose showed that the sugar-evoked current was due to an increase in the Na influx. Ouabain or amiloride reduced the sugar-evoked Na influx without effect on sugar transport as measured with tritiated 3-O-methylglucose. Amiloride inhibited the canine chorda tympani response to 0.5 M NaCl by 70-80% and the response to 0.5 M KCl by approximately 40%. This agreed with the percent inhibition by amiloride of the short-circuit current supported in vitro by NaCl and KCl. Amiloride also partially inhibited the chorda tympani responses to sucrose and to fructose. The results indicate that in the dog: (a) the ion transporter subserving Na taste also subserves part of the response to K, and (b) a sugar-activated, Na- preferring ion-transport system is one mechanism mediating sugar taste transduction. Results in the literature indicate a similar sweet taste mechanism for humans. PMID:3171536

Ion transport in broad bean leaf mesophyll under saline conditions.

PubMed

Percey, William J; Shabala, Lana; Breadmore, Michael C; Guijt, Rosanne M; Bose, Jayakumar; Shabala, Sergey

2014-10-01

Salt stress reduces the ability of mesophyll tissue to respond to light. Potassium outward rectifying channels are responsible for 84 % of Na (+) induced potassium efflux from mesophyll cells. Modulation in ion transport of broad bean (Vicia faba L.) mesophyll to light under increased apoplastic salinity stress was investigated using vibrating ion-selective microelectrodes (the MIFE technique). Increased apoplastic Na(+) significantly affected mesophyll cells ability to respond to light by modulating ion transport across their membranes. Elevated apoplastic Na(+) also induced a significant K(+) efflux from mesophyll tissue. This efflux was mediated predominately by potassium outward rectifying channels (84 %) and the remainder of the efflux was through non-selective cation channels. NaCl treatment resulted in a reduction in photosystem II efficiency in a dose- and time-dependent manner. In particular, reductions in Fv'/Fm' were linked to K(+) homeostasis in the mesophyll tissue. Increased apoplastic Na(+) concentrations induced vanadate-sensitive net H(+) efflux, presumably mediated by the plasma membrane H(+)-ATPase. It is concluded that the observed pump's activation is essential for the maintenance of membrane potential and ion homeostasis in the cytoplasm of mesophyll under salt stress.

Modulation and Functional Role of the Orientations of the N- and P-Domains of Cu+ -Transporting ATPase along the Ion Transport Cycle.

PubMed

Meng, Dan; Bruschweiler-Li, Lei; Zhang, Fengli; Brüschweiler, Rafael

2015-08-18

Ion transport of different P-type ATPases is regulated similarly through the interplay of multiple protein domains. In the presence of ATP, binding of a cation to the ion binding site in the transmembrane helices leads to the phosphorylation of the P-domain, allowing ion transfer across the membrane. The details of the mechanism, however, are not clear. Here, we report the modulation of the orientation between the N- and P-domains of Cu(+)-transporting ATPase along the ion transport cycle using high-resolution nuclear magnetic resonance spectroscopy in solution. On the basis of residual dipolar coupling measurements, it is found that the interdomain orientation (relative openness) of the N- and P-domains is distinctly modulated depending on the specific state of the N- and P-domains along the ion translocation cycle. The two domains' relative position in the apo state is semiopen, whereas it becomes closed upon binding of ATP to the N-domain. After phosphorylation of the P-domain and the release of ADP, the opening, however, becomes the widest among all the states. We reason such wide opening resulting from the departure of ADP prepares the N- and P-domains to accommodate the A-domain for interaction and, hence, promote ion transport and allow dephosphorylation of the P-domain. Such wide interdomain opening is abolished when an Asn to Asp mutation is introduced into the conserved DXXK motif located in the hinge region of the N- and P-domains of Cu(+)-ATPase, suggesting the indispensible role of the N- and P-interdomain orientation during ion transportation. Our results shed new light on the structural and mechanistic details of P-type ATPase function at large.

Membrane Assembly and Ion Transport Ability of a Fluorinated Nanopore

PubMed Central

Godbout, Raphaël; Légaré, Sébastien; Auger, Maud; Carpentier, Claudia; Otis, François; Auger, Michèle; Lagüe, Patrick; Voyer, Normand

2016-01-01

A novel 21-residue peptide incorporating six fluorinated amino acids was prepared. It was designed to fold into an amphiphilic alpha helical structure of nanoscale length with one hydrophobic face and one fluorinated face. The formation of a fluorous interface serves as the main vector for the formation of a superstructure in a bilayer membrane. Fluorescence assays showed this ion channel's ability to facilitate the translocation of alkali metal ions through a phospholipid membrane, with selectivity for sodium ions. Computational studies showed that a tetramer structure is the most probable and stable supramolecular assembly for the active ion channel structure. The results illustrate the possibility of exploiting multiple Fδ-:M+ interactions for ion transport and using fluorous interfaces to create functional nanostructures. PMID:27835700

Membrane Assembly and Ion Transport Ability of a Fluorinated Nanopore.

PubMed

Godbout, Raphaël; Légaré, Sébastien; Auger, Maud; Carpentier, Claudia; Otis, François; Auger, Michèle; Lagüe, Patrick; Voyer, Normand

2016-01-01

A novel 21-residue peptide incorporating six fluorinated amino acids was prepared. It was designed to fold into an amphiphilic alpha helical structure of nanoscale length with one hydrophobic face and one fluorinated face. The formation of a fluorous interface serves as the main vector for the formation of a superstructure in a bilayer membrane. Fluorescence assays showed this ion channel's ability to facilitate the translocation of alkali metal ions through a phospholipid membrane, with selectivity for sodium ions. Computational studies showed that a tetramer structure is the most probable and stable supramolecular assembly for the active ion channel structure. The results illustrate the possibility of exploiting multiple Fδ-:M+ interactions for ion transport and using fluorous interfaces to create functional nanostructures.

Radial transport of high-energy oxygen ions into the deep inner magnetosphere observed by Van Allen Probes

NASA Astrophysics Data System (ADS)

Mitani, K.; Seki, K.; Keika, K.; Gkioulidou, M.; Lanzerotti, L. J.; Mitchell, D. G.; Kletzing, C.

2017-12-01

It is known that proton is main contributor of the ring current and oxygen ions can make significant contribution during major magnetic storms. Ions are supplied to the ring current by radial transport from the plasma sheet. Convective transport of lower-energy protons and diffusive transport of higher-energy protons were reported to contribute to the storm-time and quiet-time ring current respectively [e.g., Gkioulidou et al., 2016]. However, supply mechanisms of the oxygen ions are not clear. To characterize the supply of oxygen ions to the ring current during magnetic storms, we studied the properties of energetic proton and oxygen ion phase space densities (PSDs) for specific magnetic moment (μ) during the April 23-25, 2013, geomagnetic storm observed by the Van Allen Probes mission. We here report on radial transport of high-energy (μ ≥ 0.5 keV/nT) oxygen ions into the deep inner magnetosphere during the late main phase of the magnetic storm. Since protons show little change during this period, this oxygen radial transport is inferred to cause the development of the late main phase. Enhancement of poloidal magnetic fluctuations is simultaneously observed. We estimated azimuthal mode number ≤5 by using cross wavelet analysis with ground-based observation of IMAGE ground magnetometers. The fluctuations can resonate with drift and bounce motions of the oxygen ions. The results suggest that combination of the drift and drift-bounce resonances is responsible for the radial transport of high-energy oxygen ions into the deep inner magnetosphere. We also report on the radial transport of the high-energy oxygen ions into the deep inner magnetosphere during other magnetic storms.

Ionotropic and metabotropic proton-sensing receptors involved in airway inflammation in allergic asthma.

PubMed

Aoki, Haruka; Mogi, Chihiro; Okajima, Fumikazu

2014-01-01

An acidic microenvironment has been shown to evoke a variety of airway responses, including cough, bronchoconstriction, airway hyperresponsiveness (AHR), infiltration of inflammatory cells in the lung, and stimulation of mucus hyperproduction. Except for the participation of transient receptor potential vanilloid-1 (TRPV1) and acid-sensing ion channels (ASICs) in severe acidic pH (of less than 6.0)-induced cough and bronchoconstriction through sensory neurons, the molecular mechanisms underlying extracellular acidic pH-induced actions in the airways have not been fully understood. Recent studies have revealed that ovarian cancer G protein-coupled receptor 1 (OGR1)-family G protein-coupled receptors, which sense pH of more than 6.0, are expressed in structural cells, such as airway smooth muscle cells and epithelial cells, and in inflammatory and immune cells, such as eosinophils and dendritic cells. They function in a variety of airway responses related to the pathophysiology of inflammatory diseases, including allergic asthma. In the present review, we discuss the roles of ionotropic TRPV1 and ASICs and metabotropic OGR1-family G protein-coupled receptors in the airway inflammation and AHR in asthma and respiratory diseases.

Study of negative ion transport phenomena in a plasma source

NASA Astrophysics Data System (ADS)

Riz, D.; Paméla, J.

1996-07-01

NIETZSCHE (Negative Ions Extraction and Transport ZSimulation Code for HydrogEn species) is a negative ion (NI) transport code developed at Cadarache. This code calculates NI trajectories using a 3D Monte-Carlo technique, taking into account the main destruction processes, as well as elastic collisions (H-/H+) and charge exchanges (H-/H0). It determines the extraction probability of a NI created at a given position. According to the simulations, we have seen that in the case of volume production, only NI produced close to the plasma grid (PG) can be extracted. Concerning the surface production, we have studied how NI produced on the PG and accelerated by the plasma sheath backward into the source could be extracted. We demonstrate that elastic collisions and charge exchanges play an important role, which in some conditions dominates the magnetic filter effect, which acts as a magnetic mirror. NI transport in various conditions will be discussed: volume/surface production, high/low plasmas density, tent filter/transverse filter.

Automated airway evaluation system for multi-slice computed tomography using airway lumen diameter, airway wall thickness and broncho-arterial ratio

NASA Astrophysics Data System (ADS)

Odry, Benjamin L.; Kiraly, Atilla P.; Novak, Carol L.; Naidich, David P.; Lerallut, Jean-Francois

2006-03-01

Pulmonary diseases such as bronchiectasis, asthma, and emphysema are characterized by abnormalities in airway dimensions. Multi-slice computed tomography (MSCT) has become one of the primary means to depict these abnormalities, as the availability of high-resolution near-isotropic data makes it possible to evaluate airways at oblique angles to the scanner plane. However, currently, clinical evaluation of airways is typically limited to subjective visual inspection only: systematic evaluation of the airways to take advantage of high-resolution data has not proved practical without automation. We present an automated method to quantitatively evaluate airway lumen diameter, wall thickness and broncho-arterial ratios. In addition, our method provides 3D visualization of these values, graphically illustrating the location and extent of disease. Our algorithm begins by automatic airway segmentation to extract paths to the distal airways, and to create a map of airway diameters. Normally, airway diameters decrease as paths progress distally; failure to taper indicates abnormal dilatation. Our approach monitors airway lumen diameters along each airway path in order to detect abnormal profiles, allowing even subtle degrees of pathologic dilatation to be identified. Our method also systematically computes the broncho-arterial ratio at every terminal branch of the tree model, as a ratio above 1 indicates potentially abnormal bronchial dilatation. Finally, the airway wall thickness is computed at corresponding locations. These measurements are used to highlight abnormal branches for closer inspection, and can be summed to compute a quantitative global score for the entire airway tree, allowing reproducible longitudinal assessment of disease severity. Preliminary tests on patients diagnosed with bronchiectasis demonstrated rapid identification of lack of tapering, which also was confirmed by corresponding demonstration of elevated broncho-arterial ratios.

Transportation programs : challenges facing the department of transportation and congress.

DOT National Transportation Integrated Search

2009-03-01

A safe, efficient, and convenient : transportation system is integral to : the health of our economy and : quality of life. Our nations vast : transportation system of airways, : railways, roads, transit systems, : and waterways has served this : ...

Azithromycin ameliorates airway remodeling via inhibiting airway epithelium apoptosis.

PubMed

Liu, Yuanqi; Pu, Yue; Li, Diandian; Zhou, Liming; Wan, Lihong

2017-02-01

Azithromycin can benefit treating allergic airway inflammation and remodeling. In the present study, we hypothesized that azithromycin alleviated airway epithelium injury through inhibiting airway epithelium apoptosis via down regulation of caspase-3 and Bax/Bcl2 ratio in vivo and in vitro. Ovalbumin induced rat asthma model and TGF-β1-induced BEAS-2B cell apoptosis model were established, respectively. In vivo experiments, airway epithelium was stained with hematoxylin and eosin (HE) and periodic acid-Schiff (PAS) to histologically evaluate the airway inflammation and remodeling. Airway epithelium apoptotic index (AI) was further analyzed by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL), while expression of apoptosis related gene (Bax, Bcl2, Caspase-3) in lungs were measured by qRT-PCR and western blotting, respectively. In vitro experiments, apoptosis were evaluated by Flow cytometry (FCM) and TUNEL. Above apoptosis related gene were also measured by qRT-PCR and western blotting. Compared with the OVA group, azithromycin significantly reduced the inflammation score, peribronchial smooth muscle layer thickness, epithelial thickening and goblet cell metaplasia (P<0.05), and effectively suppressed AI of airway epithelium (P<0.05). Moreover, the increasing mRNA and protein expressions of Caspase-3 and Bax/Bcl-2 ratio in lung tissue were all significantly decreased in azithromycin-treated rats (P<0.05). In vitro, azithromycin significantly suppressed TGF-β1-induced BEAS-2B cells apoptosis (P<0.05) and reversed TGF-β1 elevated Caspase-3 mRNA level and Bax/Bcl-2 ratio (P<0.05). Azithromycin is an attractive treatment option for reducing airway epithelial cell apoptosis by improving the imbalance of Bax/Bcl-2 ratio and inhibiting Caspase-3 level in airway epithelium. Copyright © 2016 Elsevier Inc. All rights reserved.

Mechanism of unassisted ion transport across membrane bilayers

NASA Technical Reports Server (NTRS)

Wilson, M. A.; Pohorille, A.

1996-01-01

To establish how charged species move from water to the nonpolar membrane interior and to determine the energetic and structural effects accompanying this process, we performed molecular dynamics simulations of the transport of Na+ and Cl- across a lipid bilayer located between two water lamellae. The total length of molecular dynamics trajectories generated for each ion was 10 ns. Our simulations demonstrate that permeation of ions into the membrane is accompanied by the formation of deep, asymmetric thinning defects in the bilayer, whereby polar lipid head groups and water penetrate the nonpolar membrane interior. Once the ion crosses the midplane of the bilayer the deformation "switches sides"; the initial defect slowly relaxes, and a defect forms in the outgoing side of the bilayer. As a result, the ion remains well solvated during the process; the total number of oxygen atoms from water and lipid head groups in the first solvation shell remains constant. A similar membrane deformation is formed when the ion is instantaneously inserted into the interior of the bilayer. The formation of defects considerably lowers the free energy barrier to transfer of the ion across the bilayer and, consequently, increases the permeabilities of the membrane to ions, compared to the rigid, planar structure, by approximately 14 orders of magnitude. Our results have implications for drug delivery using liposomes and peptide insertion into membranes.

Bioinspired ion-transport properties of solid-state single nanochannels and their applications in sensing.

PubMed

Tian, Ye; Wen, Liping; Hou, Xu; Hou, Guanglei; Jiang, Lei

2012-07-16

Biological ion channels are able to control ion-transport processes precisely because of their intriguing properties, such as selectivity, rectification, and gating. Learning from nature, scientists have developed a promising system--solid-state single nanochannels--to mimic biological ion-transport properties. These nanochannels have many impressive properties, such as excess surface charge, making them selective; the ability to be produced or modified asymmetrically, endowing them with rectification; and chemical reactivity of the inner surface, imparting them with desired gating properties. Based on these unique characteristics, solid-state single nanochannels have been explored in various applications, such as sensing. In this context, we summarize recent developments of bioinspired solid-state single nanochannels with ion-transport properties that resemble their biological counterparts, including selectivity, rectification, and gating; their applications in sensing are also introduced briefly. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The influence of self-assembling supramolecular structures on the passive membrane transport of ion-paired molecules.

PubMed

Benaouda, F; Brown, M B; Shah, B; Martin, G P; Jones, S A

2012-12-15

Weak ion-ion interactions, such as those associated with ion-pair formation, are difficult to isolate and characterise in the liquid state, but they have the potential to alter significantly the physicochemical behaviour of molecules in solution. The aim of this work was to gain a better understanding of how ion-ion interactions influenced passive membrane transport. The test system was composed of propylene (PG) glycol, water and diclofenac diethylamine (DDEA). Infrared spectroscopy was employed to determine the nature of the DDEA ion-pair interactions and the drug-vehicle association. Passive transport was assessed using homogeneous synthetic membranes. Solution-state analysis demonstrated that the ion-pair was unperturbed by vehicle composition changes, but the solvent-DDEA interactions were modified. DDEA-PG/water hydrogen bonding influenced the ion-pair solubility (X(dev)) and the solvent interactions slowed transport rate in PG-rich vehicles (0.84±0.05 μg cm(-2) h(-1), at ln(X(dev))=0.57). In water-rich co-solvents, the presence of strong water structuring facilitated a significant increase (p<0.05) in transmembrane penetration rate (e.g. 4.33±0.92 μg cm(-2) h(-1), at ln(X(dev))=-0.13). The data demonstrates that weak ion-ion interactions can result in the embedding of polar entities within a stable solvent complex and spontaneous supramolecular assembly should be considered when interpreting transmembrane transport processes of ionic molecules. Copyright © 2012 Elsevier B.V. All rights reserved.

Regulation of transepithelial ion transport in the rat late distal colon by the sympathetic nervous system.

PubMed

Zhang, X; Li, Y; Zhang, X; Duan, Z; Zhu, J

2015-01-01

The colorectum (late distal colon) is innervated by the sympathetic nervous system, and many colorectal diseases are related to disorders of the sympathetic nervous system. The sympathetic regulation of colorectal ion transport is rarely reported. The present study aims to investigate the effect of norepinephrine (NE) in the normal and catecholamine-depleted condition to clarify the regulation of the sympathetic adrenergic system in ion transport in the rat colorectum. NE-induced ion transport in the rats colorectum was measured by short-circuit current (I(sc)) recording; the expression of beta-adrenoceptors and NE transporter (NET) were quantified by real-time PCR, and western blotting. When the endogenous catecholamine was depleted by reserpine, the baseline I(sc) in the colorectum was increased significantly comparing to controls. NE evoked downward deltaI(sc) in colorectum of treated rats was 1.8-fold of controls. The expression of beta(2)-adrenoceptor protein in the colorectal mucosa was greater than the control, though the mRNA level was reduced. However, NET expression was significantly lower in catecholamine-depleted rats compared to the controls. In conclusion, the sympathetic nervous system plays an important role in regulating basal ion transport in the colorectum. Disorders of sympathetic neurotransmitters result in abnormal ion transport, beta-adrenoceptor and NET are involved in the process.

Inflammation Promotes Airway Epithelial ATP Release via Calcium-Dependent Vesicular Pathways

PubMed Central

Okada, Seiko F.; Ribeiro, Carla M. P.; Sesma, Juliana I.; Seminario-Vidal, Lucia; Abdullah, Lubna H.; van Heusden, Catharina; Lazarowski, Eduardo R.

2013-01-01

ATP in airway surface liquid (ASL) controls mucociliary clearance functions via the activation of airway epithelial purinergic receptors. However, abnormally elevated ATP levels have been reported in inflamed airways, suggesting that excessive ATP in ASL contributes to airway inflammation. Despite these observations, little is known about the mechanisms of ATP accumulation in the ASL covering inflamed airways. In this study, links between cystic fibrosis (CF)–associated airway inflammation and airway epithelial ATP release were investigated. Primary human bronchial epithelial (HBE) cells isolated from CF lungs exhibited enhanced IL-8 secretion after 6 to 11 days, but not 28 to 35 days, in culture, compared with normal HBE cells. Hypotonic cell swelling–promoted ATP release was increased in 6- to 11-day-old CF HBE cells compared with non-CF HBE cells, but returned to normal values after 28 to 35 days in culture. The exposure of non-CF HBE cells to airway secretions isolated from CF lungs, namely, sterile supernatants of mucopurulent material (SMM), also caused enhanced IL-8 secretion and increased ATP release. The SMM-induced increase in ATP release was sensitive to Ca2+ chelation and vesicle trafficking/exocytosis inhibitors, but not to pannexin inhibition. Transcript levels of the vesicular nucleotide transporter, but not pannexin 1, were up-regulated after SMM exposure. SMM-treated cultures displayed increased basal mucin secretion, but mucin secretion was not enhanced in response to hypotonic challenge after the exposure of cells to either vehicle or SMM. We propose that CF airway inflammation up-regulates the capacity of airway epithelia to release ATP via Ca2+-dependent vesicular mechanisms not associated with mucin granule secretion. PMID:23763446

Accessing the bottleneck in all-solid state batteries, lithium-ion transport over the solid-electrolyte-electrode interface.

PubMed

Yu, Chuang; Ganapathy, Swapna; Eck, Ernst R H van; Wang, Heng; Basak, Shibabrata; Li, Zhaolong; Wagemaker, Marnix

2017-10-20

Solid-state batteries potentially offer increased lithium-ion battery energy density and safety as required for large-scale production of electrical vehicles. One of the key challenges toward high-performance solid-state batteries is the large impedance posed by the electrode-electrolyte interface. However, direct assessment of the lithium-ion transport across realistic electrode-electrolyte interfaces is tedious. Here we report two-dimensional lithium-ion exchange NMR accessing the spontaneous lithium-ion transport, providing insight on the influence of electrode preparation and battery cycling on the lithium-ion transport over the interface between an argyrodite solid-electrolyte and a sulfide electrode. Interfacial conductivity is shown to depend strongly on the preparation method and demonstrated to drop dramatically after a few electrochemical (dis)charge cycles due to both losses in interfacial contact and increased diffusional barriers. The reported exchange NMR facilitates non-invasive and selective measurement of lithium-ion interfacial transport, providing insight that can guide the electrolyte-electrode interface design for future all-solid-state batteries.

Computationally efficient analysis of particle transport and deposition in a human whole-lung-airway model. Part II: Dry powder inhaler application.

PubMed

Kolanjiyil, Arun V; Kleinstreuer, Clement; Sadikot, Ruxana T

2017-05-01

Pulmonary drug delivery is becoming a favored route for administering drugs to treat both lung and systemic diseases. Examples of lung diseases include asthma, cystic fibrosis and chronic obstructive pulmonary disease (COPD) as well as respiratory distress syndrome (ARDS) and pulmonary fibrosis. Special respiratory drugs are administered to the lungs, using an appropriate inhaler device. Next to the pressurized metered-dose inhaler (pMDI), the dry powder inhaler (DPI) is a frequently used device because of the good drug stability and a minimal need for patient coordination. Specific DPI-designs and operations greatly affect drug-aerosol formation and hence local lung deposition. Simulating the fluid-particle dynamics after use of a DPI allows for the assessment of drug-aerosol deposition and can also assist in improving the device configuration and operation. In Part I of this study a first-generation whole lung-airway model (WLAM) was introduced and discussed to analyze particle transport and deposition in a human respiratory tract model. In the present Part II the drug-aerosols are assumed to be injected into the lung airways from a DPI mouth-piece, forming the mouth-inlet. The total as well as regional particle depositions in the WLAM, as inhaled from a DPI, were successfully compared with experimental data sets reported in the open literature. The validated modeling methodology was then employed to study the delivery of curcumin aerosols into lung airways using a commercial DPI. Curcumin has been implicated to possess high therapeutic potential as an antioxidant, anti-inflammatory and anti-cancer agent. However, efficacy of curcumin treatment is limited because of the low bioavailability of curcumin when ingested. Hence, alternative drug administration techniques, e.g., using inhalable curcumin-aerosols, are under investigation. Based on the present results, it can be concluded that use of a DPI leads to low lung deposition efficiencies because large amounts of

Protective effects of valproic acid against airway hyperresponsiveness and airway remodeling in a mouse model of allergic airways disease.

PubMed

Royce, Simon G; Dang, William; Ververis, Katherine; De Sampayo, Nishika; El-Osta, Assam; Tang, Mimi L K; Karagiannis, Tom C

2011-12-01

Airway remodeling and airway hyperresponsiveness are major aspects of asthma pathology that are not targeted optimally by existing anti-inflammatory drugs. Histone deacetylase inhibitors have a wide range of effects that may potentially abrogate aspects of remodeling. One such histone deacetylase inhibitor is valproic acid (2-propylvaleric acid). Valproic acid is used clinically as an anti-epileptic drug and is a potent inhibitor of class I histone deacetylases but also inhibits class II histone deacetylases. We used valproic acid as a molecular model of histone deacetylase inhibition in vivo in chronic allergic airways disease mice with airway remodeling and airway hyperresponsiveness. Wild-type Balb/c mice with allergic airways disease were treated with valproic acid or vehicle control. Airway inflammation was assessed by bronchoalveolar lavage fluid cell counts and examination of lung tissue sections. Remodeling was assessed by morphometric analysis of histochemically stained slides and lung function was assessed by invasive plethysmography measurement of airway resistance. Valproic acid treatment did not affect inflammation parameters; however, valproic acid treatment resulted in reduced epithelial thickness as compared to vehicle treated mice (p < 0.01), reduced subepithelial collagen deposition (p < 0.05) and attenuated airway hyperresponsiveness (p < 0.05 and p < 0.01 for the two highest doses of methacholine, respectively). These findings show that treatment with valproic acid can reduce structural airway remodeling changes and hyperresponsiveness, providing further evidence for the potential use of histone deacetylase inhibitors for the treatment of asthma.

Structural and mechanistic basis of proton-coupled metal ion transport in the SLC11/NRAMP family

PubMed Central

Ehrnstorfer, Ines A.; Manatschal, Cristina; Arnold, Fabian M.; Laederach, Juerg; Dutzler, Raimund

2017-01-01

Secondary active transporters of the SLC11/NRAMP family catalyse the uptake of iron and manganese into cells. These proteins are highly conserved across all kingdoms of life and thus likely share a common transport mechanism. Here we describe the structural and functional properties of the prokaryotic SLC11 transporter EcoDMT. Its crystal structure reveals a previously unknown outward-facing state of the protein family. In proteoliposomes EcoDMT mediates proton-coupled uptake of manganese at low micromolar concentrations. Mutants of residues in the transition-metal ion-binding site severely affect transport, whereas a mutation of a conserved histidine located near this site results in metal ion transport that appears uncoupled to proton transport. Combined with previous results, our study defines the conformational changes underlying transition-metal ion transport in the SLC11 family and it provides molecular insight to its coupling to protons. PMID:28059071

Airway stents

PubMed Central

Keyes, Colleen

2018-01-01

Stents and tubes to maintain the patency of the airways are commonly used for malignant obstruction and are occasionally employed in benign disease. Malignant airway obstruction usually results from direct involvement of bronchogenic carcinoma, or by extension of carcinomas occurring in the esophagus or the thyroid. External compression from lymph nodes or metastatic disease from other organs can also cause central airway obstruction. Most malignant airway lesions are surgically inoperable due to advanced disease stage and require multimodality palliation, including stent placement. As with any other medical device, stents have significantly evolved over the last 50 years and deserve an in-depth understanding of their true capabilities and complications. Not every silicone stent is created equal and the same holds for metallic stents. Herein, we present an overview of the topic as well as some of the more practical and controversial issues surrounding airway stents. We also try to dispel the myths surrounding stent removal and their supposed use only in central airways. At the end, we come to the long-held conclusion that stents should not be used as first line treatment of choice, but after ruling out the possibility of curative surgical resection or repair. PMID:29707506

Inhibiting Inducible Nitric Oxide Synthase in Enteric Glia Restores Electrogenic Ion Transport in Mice with Colitis

PubMed Central

MacEachern, Sarah J.; Patel, Bhavik A.; Keenan, Catherine M.; Dicay, Michael; Chapman, Kevin; McCafferty, Donna-Marie; Savidge, Tor C.; Beck, Paul L.; MacNaughton, Wallace K.; Sharkey, Keith A.

2015-01-01

Background & Aims Disturbances in the control of ion transport lead to epithelial barrier dysfunction in patients with colitis. Enteric glia regulate intestinal barrier function and colonic ion transport. However, it is not clear whether enteric glia are involved in the epithelial hypo-responsiveness. We investigated enteric glial regulation of ion transport in mice with trinitrobenzene sulphonic acid- or dextran sodium sulfate-induced colitis and in Il10−/− mice. Methods Electrically-evoked ion transport was measured in full-thickness segments of colon from CD1 and Il10−/− mice with or without colitis in Ussing chambers. Nitric oxide (NO) production was assessed using amperometry. Bacterial translocation was investigated in the liver, spleen and blood of mice. Results Electrical stimulation of the colon evoked a tetrodotoxin-sensitive chloride secretion. In mice with colitis, ion transport almost completely disappeared. Inhibiting inducible NO synthase (NOS2), but not neuronal NOS (NOS1), partially restored the evoked secretory response. Blocking glial function with fluoroacetate, which is not a NOS2 inhibitor, also partially restored ion transport. Combined NOS2 inhibition and fluoroacetate administration fully restored secretion. Epithelial responsiveness to vasoactive intestinal peptide was increased after enteric glial function was blocked in mice with colitis. In colons of mice without colitis, NO was produced in the myenteric plexus almost completely via NOS1. NO production was increased in mice with colitis, compared to mice without colitis; a substantial proportion of NOS2 was blocked by fluoroacetate administration. Inhibition of enteric glial function in vivo reduced the severity of trinitrobenzene sulphonic acid -induced colitis and associated bacterial translocation. Conclusions Increased production of NOS2 in enteric glia contributes to the dysregulation of intestinal ion transport in mice with colitis. Blocking enteric glial function in these

Inhibiting Inducible Nitric Oxide Synthase in Enteric Glia Restores Electrogenic Ion Transport in Mice With Colitis.

PubMed

MacEachern, Sarah J; Patel, Bhavik A; Keenan, Catherine M; Dicay, Michael; Chapman, Kevin; McCafferty, Donna-Marie; Savidge, Tor C; Beck, Paul L; MacNaughton, Wallace K; Sharkey, Keith A

2015-08-01

Disturbances in the control of ion transport lead to epithelial barrier dysfunction in patients with colitis. Enteric glia regulate intestinal barrier function and colonic ion transport. However, it is not clear whether enteric glia are involved in epithelial hyporesponsiveness. We investigated enteric glial regulation of ion transport in mice with trinitrobenzene sulfonic acid- or dextran sodium sulfate-induced colitis and in Il10(-/-) mice. Electrically evoked ion transport was measured in full-thickness segments of colon from CD1 and Il10(-/-) mice with or without colitis in Ussing chambers. Nitric oxide (NO) production was assessed using amperometry. Bacterial translocation was investigated in the liver, spleen, and blood of mice. Electrical stimulation of the colon evoked a tetrodotoxin-sensitive chloride secretion. In mice with colitis, ion transport almost completely disappeared. Inhibiting inducible NO synthase (NOS2), but not neuronal NOS (NOS1), partially restored the evoked secretory response. Blocking glial function with fluoroacetate, which is not a NOS2 inhibitor, also partially restored ion transport. Combined NOS2 inhibition and fluoroacetate administration fully restored secretion. Epithelial responsiveness to vasoactive intestinal peptide was increased after enteric glial function was blocked in mice with colitis. In colons of mice without colitis, NO was produced in the myenteric plexus almost completely via NOS1. NO production was increased in mice with colitis, compared with mice without colitis; a substantial proportion of NOS2 was blocked by fluoroacetate administration. Inhibition of enteric glial function in vivo reduced the severity of trinitrobenzene sulfonic acid-induced colitis and associated bacterial translocation. Increased production of NOS2 in enteric glia contributes to the dysregulation of intestinal ion transport in mice with colitis. Blocking enteric glial function in these mice restores epithelial barrier function and reduces

Feed gas contaminant control in ion transport membrane systems

DOEpatents

Carolan, Michael Francis [Allentown, PA; Minford, Eric [Laurys Station, PA; Waldron, William Emil [Whitehall, PA

2009-07-07

Ion transport membrane oxidation system comprising an enclosure having an interior and an interior surface, inlet piping having an internal surface and adapted to introduce a heated feed gas into the interior of the enclosure, and outlet piping adapted to withdraw a product gas from the interior of the enclosure; one or more planar ion transport membrane modules disposed in the interior of the enclosure, each membrane module comprising mixed metal oxide material; and a preheater adapted to heat a feed gas to provide the heated feed gas to the inlet piping, wherein the preheater comprises an interior surface. Any of the interior surfaces of the enclosure, the inlet piping, and the preheater may be lined with a copper-containing metal lining. Alternatively, any of the interior surfaces of the inlet piping and the preheater may be lined with a copper-containing metal lining and the enclosure may comprise copper.

Local small airway epithelial injury induces global smooth muscle contraction and airway constriction.

PubMed

Zhou, Jian; Alvarez-Elizondo, Martha B; Botvinick, Elliot; George, Steven C

2012-02-01

Small airway epithelial cells form a continuous sheet lining the conducting airways, which serves many functions including a physical barrier to protect the underlying tissue. In asthma, injury to epithelial cells can occur during bronchoconstriction, which may exacerbate airway hyperreactivity. To investigate the role of epithelial cell rupture in airway constriction, laser ablation was used to precisely rupture individual airway epithelial cells of small airways (<300-μm diameter) in rat lung slices (∼250-μm thick). Laser ablation of single epithelial cells using a femtosecond laser reproducibly induced airway contraction to ∼70% of the original cross-sectional area within several seconds, and the contraction lasted for up to 40 s. The airway constriction could be mimicked by mechanical rupture of a single epithelial cell using a sharp glass micropipette but not with a blunt glass pipette. These results suggest that soluble mediators released from the wounded epithelial cell induce global airway contraction. To confirm this hypothesis, the lysate of primary human small airway epithelial cells stimulated a similar airway contraction. Laser ablation of single epithelial cells triggered a single instantaneous Ca(2+) wave in the epithelium, and multiple Ca(2+) waves in smooth muscle cells, which were delayed by several seconds. Removal of extracellular Ca(2+) or decreasing intracellular Ca(2+) both blocked laser-induced airway contraction. We conclude that local epithelial cell rupture induces rapid and global airway constriction through release of soluble mediators and subsequent Ca(2+)-dependent smooth muscle shortening.

Epithelial Sodium and Acid-Sensing Ion Channels

NASA Astrophysics Data System (ADS)

Kellenberger, Stephan

The epithelial Na+ channel (ENaC) and acid-sensing ion channels (ASICs) are non-voltage-gated Na+ channels that form their own subfamilies within the ENaC/degenerin ion channel family. ASICs are sensors of extracellular pH, and ENaC, whose main function is trans-epithelial Na+ transport, can sense extra- and intra-cellular Na+. In aldosterone-responsive epithelial cells of the kidney, ENaC plays a critical role in the control of sodium balance, blood volume and blood pressure. In airway epithelia, ENaC has a distinct role in controlling fluid reabsorption at the air-liquid interface, thereby determining the rate of mucociliary transport. In taste receptor cells of the tongue, ENaC is involved in salt taste sensation. ASICs have emerged as key sensors for extracellular protons in central and peripheral neurons. Although not all of their physiological and pathological functions are firmly established yet, there is good evidence for a role of ASICs in the brain in learning, expression of fear, and in neurodegeneration after ischaemic stroke. In sensory neurons, ASICs are involved in nociception and mechanosensation. ENaC and ASIC subunits share substantial sequence homology and the conservation of several functional domains. This chapter summarises our current understanding of the physiological functions and of the mechanisms of ion permeation, gating and regulation of ENaC and ASICs.

Atopic asthmatic immune phenotypes associated with airway microbiota and airway obstruction.

PubMed

Turturice, Benjamin A; McGee, Halvor S; Oliver, Brian; Baraket, Melissa; Nguyen, Brian T; Ascoli, Christian; Ranjan, Ravi; Rani, Asha; Perkins, David L; Finn, Patricia W

2017-01-01

Differences in asthma severity may be related to inflammation in the airways. The lower airway microbiota has been associated with clinical features such as airway obstruction, symptom control, and response to corticosteroids. To assess the relationship between local airway inflammation, severity of disease, and the lower airway microbiota in atopic asthmatics. A cohort of young adult, atopic asthmatics with intermittent or mild/moderate persistent symptoms (n = 13) were assessed via bronchoscopy, lavage, and spirometry. These individuals were compared to age matched non-asthmatic controls (n = 6) and to themselves after six weeks of treatment with fluticasone propionate (FP). Inflammation of the airways was assessed via a cytokine and chemokine panel. Lower airway microbiota composition was determined by metagenomic shotgun sequencing. Unsupervised clustering of cytokines and chemokines prior to treatment with FP identified two asthmatic phenotypes (AP), termed AP1 and AP2, with distinct bronchoalveolar lavage inflammatory profiles. AP2 was associated with more obstruction, compared to AP1. After treatment with FP reduced MIP-1β and TNF-α and increased IL-2 was observed. A module of highly correlated cytokines that include MIP-1β and TNF-α was identified that negatively correlated with pulmonary function. Independently, IL-2 was positively correlated with pulmonary function. The airway microbiome composition correlated with asthmatic phenotypes. AP2, prior to FP treatment, was enriched with Streptococcus pneumoniae. Unique associations between IL-2 or the cytokine module and the microbiota composition of the airways were observed in asthmatics subjects prior to treatment but not after or in controls. The underlying inflammation in atopic asthma is related to the composition of microbiota and is associated with severity of airway obstruction. Treatment with inhaled corticosteroids was associated with changes in the airway inflammatory response to microbiota.

Early vertebrate origin and diversification of small transmembrane regulators of cellular ion transport.

PubMed

Pirkmajer, Sergej; Kirchner, Henriette; Lundell, Leonidas S; Zelenin, Pavel V; Zierath, Juleen R; Makarova, Kira S; Wolf, Yuri I; Chibalin, Alexander V

2017-07-15

Small transmembrane proteins such as FXYDs, which interact with Na + ,K + -ATPase, and the micropeptides that interact with sarco/endoplasmic reticulum Ca 2+ -ATPase play fundamental roles in regulation of ion transport in vertebrates. Uncertain evolutionary origins and phylogenetic relationships among these regulators of ion transport have led to inconsistencies in their classification across vertebrate species, thus hampering comparative studies of their functions. We discovered the first FXYD homologue in sea lamprey, a basal jawless vertebrate, which suggests small transmembrane regulators of ion transport emerged early in the vertebrate lineage. We also identified 13 gene subfamilies of FXYDs and propose a revised, phylogeny-based FXYD classification that is consistent across vertebrate species. These findings provide an improved framework for investigating physiological and pathophysiological functions of small transmembrane regulators of ion transport. Small transmembrane proteins are important for regulation of cellular ion transport. The most prominent among these are members of the FXYD family (FXYD1-12), which regulate Na + ,K + -ATPase, and phospholamban, sarcolipin, myoregulin and DWORF, which regulate the sarco/endoplasmic reticulum Ca 2+ -ATPase (SERCA). FXYDs and regulators of SERCA are present in fishes, as well as terrestrial vertebrates; however, their evolutionary origins and phylogenetic relationships are obscure, thus hampering comparative physiological studies. Here we discovered that sea lamprey (Petromyzon marinus), a representative of extant jawless vertebrates (Cyclostomata), expresses an FXYD homologue, which strongly suggests that FXYDs predate the emergence of fishes and other jawed vertebrates (Gnathostomata). Using a combination of sequence-based phylogenetic analysis and conservation of local chromosome context, we determined that FXYDs markedly diversified in the lineages leading to cartilaginous fishes (Chondrichthyes) and bony

Effect of radial plasma transport at the magnetic throat on axial ion beam formation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Yunchao, E-mail: yunchao.zhang@anu.edu.au; Charles, Christine; Boswell, Rod

2016-08-15

Correlation between radial plasma transport and formation of an axial ion beam has been investigated in a helicon plasma reactor implemented with a convergent-divergent magnetic nozzle. The plasma discharge is sustained under a high magnetic field mode and a low magnetic field mode for which the electron energy probability function, the plasma density, the plasma potential, and the electron temperature are measured at the magnetic throat, and the two field modes show different radial parametric behaviors. Although an axial potential drop occurs in the plasma source for both field modes, an ion beam is only observed in the high fieldmore » mode while not in the low field mode. The transport of energetic ions is characterized downstream of the plasma source using the delimited ion current and nonlocal ion current. A decay of ion beam strength is also observed in the diffusion chamber.« less

Degrees of reality: airway anatomy of high-fidelity human patient simulators and airway trainers.

PubMed

Schebesta, Karl; Hüpfl, Michael; Rössler, Bernhard; Ringl, Helmut; Müller, Michael P; Kimberger, Oliver

2012-06-01

Human patient simulators and airway training manikins are widely used to train airway management skills to medical professionals. Furthermore, these patient simulators are employed as standardized "patients" to evaluate airway devices. However, little is known about how realistic these patient simulators and airway-training manikins really are. This trial aimed to evaluate the upper airway anatomy of four high-fidelity patient simulators and two airway trainers in comparison with actual patients by means of radiographic measurements. The volume of the pharyngeal airspace was the primary outcome parameter. Computed tomography scans of 20 adult trauma patients without head or neck injuries were compared with computed tomography scans of four high-fidelity patient simulators and two airway trainers. By using 14 predefined distances, two cross-sectional areas and three volume parameters of the upper airway, the manikins' similarity to a human patient was assessed. The pharyngeal airspace of all manikins differed significantly from the patients' pharyngeal airspace. The HPS Human Patient Simulator (METI®, Sarasota, FL) was the most realistic high-fidelity patient simulator (6/19 [32%] of all parameters were within the 95% CI of human airway measurements). The airway anatomy of four high-fidelity patient simulators and two airway trainers does not reflect the upper airway anatomy of actual patients. This finding may impact airway training and confound comparative airway device studies.

Modeling of ion transport through a porous separator in vanadium redox flow batteries

NASA Astrophysics Data System (ADS)

Zhou, X. L.; Zhao, T. S.; An, L.; Zeng, Y. K.; Wei, L.

2016-09-01

In this work, we develop a two-dimensional, transient model to investigate the mechanisms of ion-transport through a porous separator in VRFBs and their effects on battery performance. Commercial-available separators with pore sizes of around 45 nm are particularly investigated and effects of key separator design parameters and operation modes are explored. We reveal that: i) the transport mechanism of vanadium-ion crossover through available separators is predominated by convection; ii) reducing the pore size below 15 nm effectively minimizes the convection-driven vanadium-ion crossover, while further reduction in migration- and diffusion-driven vanadium-ion crossover can be achieved only when the pore size is reduced to the level close to the sizes of vanadium ions; and iii) operation modes that can affect the pressure at the separator/electrode interface, such as the electrolyte flow rate, exert a significant influence on the vanadium-ion crossover rate through the available separators, indicating that it is critically important to equalize the pressure on each half-cell of a power pack in practical applications.

Local small airway epithelial injury induces global smooth muscle contraction and airway constriction

PubMed Central

Zhou, Jian; Alvarez-Elizondo, Martha B.; Botvinick, Elliot

2012-01-01

Small airway epithelial cells form a continuous sheet lining the conducting airways, which serves many functions including a physical barrier to protect the underlying tissue. In asthma, injury to epithelial cells can occur during bronchoconstriction, which may exacerbate airway hyperreactivity. To investigate the role of epithelial cell rupture in airway constriction, laser ablation was used to precisely rupture individual airway epithelial cells of small airways (<300-μm diameter) in rat lung slices (∼250-μm thick). Laser ablation of single epithelial cells using a femtosecond laser reproducibly induced airway contraction to ∼70% of the original cross-sectional area within several seconds, and the contraction lasted for up to 40 s. The airway constriction could be mimicked by mechanical rupture of a single epithelial cell using a sharp glass micropipette but not with a blunt glass pipette. These results suggest that soluble mediators released from the wounded epithelial cell induce global airway contraction. To confirm this hypothesis, the lysate of primary human small airway epithelial cells stimulated a similar airway contraction. Laser ablation of single epithelial cells triggered a single instantaneous Ca2+ wave in the epithelium, and multiple Ca2+ waves in smooth muscle cells, which were delayed by several seconds. Removal of extracellular Ca2+ or decreasing intracellular Ca2+ both blocked laser-induced airway contraction. We conclude that local epithelial cell rupture induces rapid and global airway constriction through release of soluble mediators and subsequent Ca2+-dependent smooth muscle shortening. PMID:22114176

HZETRN: A heavy ion/nucleon transport code for space radiations

NASA Technical Reports Server (NTRS)

Wilson, John W.; Chun, Sang Y.; Badavi, Forooz F.; Townsend, Lawrence W.; Lamkin, Stanley L.

1991-01-01

The galactic heavy ion transport code (GCRTRN) and the nucleon transport code (BRYNTRN) are integrated into a code package (HZETRN). The code package is computer efficient and capable of operating in an engineering design environment for manned deep space mission studies. The nuclear data set used by the code is discussed including current limitations. Although the heavy ion nuclear cross sections are assumed constant, the nucleon-nuclear cross sections of BRYNTRN with full energy dependence are used. The relation of the final code to the Boltzmann equation is discussed in the context of simplifying assumptions. Error generation and propagation is discussed, and comparison is made with simplified analytic solutions to test numerical accuracy of the final results. A brief discussion of biological issues and their impact on fundamental developments in shielding technology is given.

[PLASMALEMMAL ION TRANSPORT IN POLLEN TUBES IS REGULATED BY HYDROGEN PEROXIDE].

PubMed

Maksimov, N M; Breygina, M A; Yermakov, I P

2015-01-01

Pollen tube growth is a key step in the life cycle of seed plants, which defines the success of sexual reproduction. One of the most important contributions to this process is made by ion transport through plasmalemma, which is tightly coordinated in time and space. Different classes of signaling molecules are involved in the regulation of transmembrane ion transport including reactive oxygen species as it has been recently demonstrated. Here, using subprotoplasts isolated from pollen tubes, we have demonstrated a connection between hydrogen peroxide, on one side, and two groups of targets on the plasma membrane, on the other side: nifedipine-sensitive Ca(2+)-permeable channels and transport systems controlling membrane potential. H2O2 interaction with these targets causes the increase in cytoplasmic Ca2+ concentration and plasmalemma hyperpolarization. One of the consequences of target modification was acceleration of cell wall regeneration.

Unravelling Li-Ion Transport from Picoseconds to Seconds: Bulk versus Interfaces in an Argyrodite Li6PS5Cl-Li2S All-Solid-State Li-Ion Battery.

PubMed

Yu, Chuang; Ganapathy, Swapna; de Klerk, Niek J J; Roslon, Irek; van Eck, Ernst R H; Kentgens, Arno P M; Wagemaker, Marnix

2016-09-07

One of the main challenges of all-solid-state Li-ion batteries is the restricted power density due to the poor Li-ion transport between the electrodes via the electrolyte. However, to establish what diffusional process is the bottleneck for Li-ion transport requires the ability to distinguish the various processes. The present work investigates the Li-ion diffusion in argyrodite Li6PS5Cl, a promising electrolyte based on its high Li-ion conductivity, using a combination of (7)Li NMR experiments and DFT based molecular dynamics simulations. This allows us to distinguish the local Li-ion mobility from the long-range Li-ion motional process, quantifying both and giving a coherent and consistent picture of the bulk diffusion in Li6PS5Cl. NMR exchange experiments are used to unambiguously characterize Li-ion transport over the solid electrolyte-electrode interface for the electrolyte-electrode combination Li6PS5Cl-Li2S, giving unprecedented and direct quantitative insight into the impact of the interface on Li-ion charge transport in all-solid-state batteries. The limited Li-ion transport over the Li6PS5Cl-Li2S interface, orders of magnitude smaller compared with that in the bulk Li6PS5Cl, appears to be the bottleneck for the performance of the Li6PS5Cl-Li2S battery, quantifying one of the major challenges toward improved performance of all-solid-state batteries.

Computation of Alfvèn eigenmode stability and saturation through a reduced fast ion transport model in the TRANSP tokamak transport code

NASA Astrophysics Data System (ADS)

Podestà, M.; Gorelenkova, M.; Gorelenkov, N. N.; White, R. B.

2017-09-01

Alfvénic instabilities (AEs) are well known as a potential cause of enhanced fast ion transport in fusion devices. Given a specific plasma scenario, quantitative predictions of (i) expected unstable AE spectrum and (ii) resulting fast ion transport are required to prevent or mitigate the AE-induced degradation in fusion performance. Reduced models are becoming an attractive tool to analyze existing scenarios as well as for scenario prediction in time-dependent simulations. In this work, a neutral beam heated NSTX discharge is used as reference to illustrate the potential of a reduced fast ion transport model, known as kick model, that has been recently implemented for interpretive and predictive analysis within the framework of the time-dependent tokamak transport code TRANSP. Predictive capabilities for AE stability and saturation amplitude are first assessed, based on given thermal plasma profiles only. Predictions are then compared to experimental results, and the interpretive capabilities of the model further discussed. Overall, the reduced model captures the main properties of the instabilities and associated effects on the fast ion population. Additional information from the actual experiment enables further tuning of the model’s parameters to achieve a close match with measurements.

Thermal Ion Transport on the Moon and the Formation of the Lunar Swirls

NASA Technical Reports Server (NTRS)

Keller, John W.; Killen, R. M.; Stubbs, T. J.; Farrell, W. M.; Halekas, J. S.

2011-01-01

The bright "swirl" features observed on the lunar surface are generally associated with crustal magnetic anomalies. Prominent explanations that invoke these fields include: magnetic shielding in the form of a mini-magnetosphere, which impedes space weathering by the solar wind; magnetically controlled dust transport; and cometary or asteroidal impacts, that could result in shock magnetization with concomitant formation of the swirls. Here we consider another possibility in which the ambient magnetic and electric fields can transport and channel secondary ions produced by micrometeorite or solar wind ion impacts. We use a simplified model of the fields, which incorporates a two-dipole magnetic field model for Reiner Gamma, and typical solar wind conditions. We will present preliminarily results suggesting that ions created over significant regions of the lunar surface can be transported under the influence of local and interplanetary electromagnetic fields to narrow areas ncar arcas of high crustal magnetic field strength. The flux of these focused ions may be of sufficient intensity to chemically process (or otherwise bleach) the surface leading to the formation of the high albedo component of the lunar swirls. The theory is appealing since through a lensing effect, it is possible that this flux is sufficient to overcome other space weathering processes which would otherwise tend to erase the features. Also, with relatively low energy ions, and consistent with the observed focusing, the ion gyro radii in the local magnetic fields is small enough to resolve the swirls.

Synopsis of the 48 annual meeting of the Lake Cumberland Biological Transport Group and the second biannual meeting of the Pendrin Consortium.

PubMed

Dossena, Silvia; Nofziger, Charity; Morabito, Rossana; Adragna, Norma C; Paulmichl, Markus

2013-01-01

Ion transporters are the molecular basis for ion homeostasis of the cell and the whole organism. The anion exchanger pendrin is only one of a number of examples where a complete or partial loss of function and/or deregulation of expression of ion transporters may lead or contribute to pathological conditions in humans. A complete understanding of the function of ion transporters in health and disease may pave the way for the identification of new and focused therapeutic approaches. Exchange of knowledge and connectivity between the experts in the feld of transport physiology is essential in facing these challenging tasks. The Lake Cumberland Biological Transport Group and the Pendrin Consortium are examples of scientific forums where investigators combine their efforts towards a better understanding of molecular pathophysiology of ion transport. This issue discusses the versatility of ion transporters involved in the regulation of cellular volume and other functions, such as the solute carrier (SLC) 12A gene family members SLC12A4-7, encoding the Na(+)-independent cation-chloride cotransporters commonly known as the K(+)-Cl(-) cotransporters KCC1-4, and the betaine/γ-aminobutyric acid transport system (BGT1, SLC6A12), just to name a few. The issue further addresses the pathophysiology of intestinal and respiratory epithelia and related therapeutic tools and techniques to investigate interactions between proteins and proteins and small compounds. Finally, the current knowledge and new findings on the expression, regulation and function of pendrin (SLC26A4) in the inner ear, kidney, airways and blood platelets are presented. © 2014 S. Karger AG, Basel.

Parasympathetic Control of Airway Submucosal Glands: Central Reflexes and the Airway Intrinsic Nervous System

PubMed Central

Wine, Jeffrey J.

2007-01-01

Airway submucosal glands produce the mucus that lines the upper airways to protect them against insults. This review summarizes evidence for two forms of gland secretion, and hypothesizes that each is mediated by different but partially overlapping neural pathways. Airway innate defense comprises low level gland secretion, mucociliary clearance and surveillance by airway-resident phagocytes to keep the airways sterile in spite of nearly continuous inhalation of low levels of pathogens. Gland secretion serving innate defense is hypothesized to be under the control of intrinsic (peripheral) airway neurons and local reflexes, and these may depend disproportionately on non-cholinergic mechanisms, with most secretion being produced by VIP and tachykinins. In the genetic disease cystic fibrosis, airway glands no longer secrete in response to VIP alone and fail to show the synergy between VIP, tachykinins and ACh that is observed in normal glands. The consequent crippling of the submucosal gland contribution to innate defense may be one reason that cystic fibrosis airways are infected by mucus-resident bacteria and fungi that are routinely cleared from normal airways. By contrast, the acute (emergency) airway defense reflex is centrally mediated by vagal pathways, is primarily cholinergic, and stimulates copious volumes of gland mucus in response to acute, intense challenges to the airways, such as those produced by very vigorous exercise or aspiration of foreign material. In cystic fibrosis, the acute airway defense reflex can still stimulate the glands to secrete large amounts of mucus, although its properties are altered. Importantly, treatments that recruit components of the acute reflex, such as inhalation of hypertonic saline, are beneficial in treating cystic fibrosis airway disease. The situation for recipients of lung transplants is the reverse; transplanted airways retain the airway intrinsic nervous system but lose centrally mediated reflexes. The consequences

Study of negative ion transport phenomena in a plasma source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Riz, D.; Pamela, J.

1996-07-01

NIETZSCHE (Negative Ions Extraction and Transport ZSimulation Code for HydrogEn species) is a negative ion (NI) transport code developed at Cadarache. This code calculates NI trajectories using a 3D Monte-Carlo technique, taking into account the main destruction processes, as well as elastic collisions (H{sup {minus}}/H{sup +}) and charge exchanges (H{sup {minus}}/H{sup 0}). It determines the extraction probability of a NI created at a given position. According to the simulations, we have seen that in the case of volume production, only NI produced close to the plasma grid (PG) can be extracted. Concerning the surface production, we have studied how NImore » produced on the PG and accelerated by the plasma sheath backward into the source could be extracted. We demonstrate that elastic collisions and charge exchanges play an important role, which in some conditions dominates the magnetic filter effect, which acts as a magnetic mirror. NI transport in various conditions will be discussed: volume/surface production, high/low plasmas density, tent filter/transverse filter. {copyright} {ital 1996 American Institute of Physics.}« less

Regulation of transepithelial ion transport by intracellular calcium ions.

PubMed

Cuthbert, A W

1985-01-01

A photodynamic effect of erythrosine B on the basolateral surface of rat colon epithelium under short circuit conditions is described. The resulting irreversible increase in short circuit current was the result of electrogenic chloride secretion. The effect was dependent upon oxygen and calcium ions, and is probably due to the generation of singlet oxygen which then permeabilises the membranes to calcium. Half maximal activation of secretion in permeabilised preparations occurred at an external calcium concentration of 1 microM. In tight sodium transporting epithelia increased Cai reduces SCC, possibly by a direct effect on apical sodium permeability. In toad urinary bladder SCC fell in response to conditions outlined above for rat colon.

Recent Improvements of Particle and Heavy Ion Transport code System: PHITS

NASA Astrophysics Data System (ADS)

Sato, Tatsuhiko; Niita, Koji; Iwamoto, Yosuke; Hashimoto, Shintaro; Ogawa, Tatsuhiko; Furuta, Takuya; Abe, Shin-ichiro; Kai, Takeshi; Matsuda, Norihiro; Okumura, Keisuke; Kai, Tetsuya; Iwase, Hiroshi; Sihver, Lembit

2017-09-01

The Particle and Heavy Ion Transport code System, PHITS, has been developed under the collaboration of several research institutes in Japan and Europe. This system can simulate the transport of most particles with energy levels up to 1 TeV (per nucleon for ion) using different nuclear reaction models and data libraries. More than 2,500 registered researchers and technicians have used this system for various applications such as accelerator design, radiation shielding and protection, medical physics, and space- and geo-sciences. This paper summarizes the physics models and functions recently implemented in PHITS, between versions 2.52 and 2.88, especially those related to source generation useful for simulating brachytherapy and internal exposures of radioisotopes.

Triplin, a small molecule, reveals copper ion transport in ethylene signaling from ATX1 to RAN1

PubMed Central

Li, Wenbo; Ye, Yajin; Lu, Juan; Yeh, Kuo-Chen; Xiao, Youli; Li, Laigeng; Binder, Brad M.

2017-01-01

Copper ions play an important role in ethylene receptor biogenesis and proper function. The copper transporter RESPONSIVE-TO-ANTAGONIST1 (RAN1) is essential for copper ion transport in Arabidopsis thaliana. However it is still unclear how copper ions are delivered to RAN1 and how copper ions affect ethylene receptors. There is not a specific copper chelator which could be used to explore these questions. Here, by chemical genetics, we identified a novel small molecule, triplin, which could cause a triple response phenotype on dark-grown Arabidopsis seedlings through ethylene signaling pathway. ran1-1 and ran1-2 are hypersensitive to triplin. Adding copper ions in growth medium could partially restore the phenotype on plant caused by triplin. Mass spectrometry analysis showed that triplin could bind copper ion. Compared to the known chelators, triplin acts more specifically to copper ion and it suppresses the toxic effects of excess copper ions on plant root growth. We further showed that mutants of ANTIOXIDANT PROTEIN1 (ATX1) are hypersensitive to tiplin, but with less sensitivity comparing with the ones of ran1-1 and ran1-2. Our study provided genetic evidence for the first time that, copper ions necessary for ethylene receptor biogenesis and signaling are transported from ATX1 to RAN1. Considering that triplin could chelate copper ions in Arabidopsis, and copper ions are essential for plant and animal, we believe that, triplin not only could be useful for studying copper ion transport of plants, but also could be useful for copper metabolism study in animal and human. PMID:28388654

Triplin, a small molecule, reveals copper ion transport in ethylene signaling from ATX1 to RAN1.

PubMed

Li, Wenbo; Lacey, Randy F; Ye, Yajin; Lu, Juan; Yeh, Kuo-Chen; Xiao, Youli; Li, Laigeng; Wen, Chi-Kuang; Binder, Brad M; Zhao, Yang

2017-04-01

Copper ions play an important role in ethylene receptor biogenesis and proper function. The copper transporter RESPONSIVE-TO-ANTAGONIST1 (RAN1) is essential for copper ion transport in Arabidopsis thaliana. However it is still unclear how copper ions are delivered to RAN1 and how copper ions affect ethylene receptors. There is not a specific copper chelator which could be used to explore these questions. Here, by chemical genetics, we identified a novel small molecule, triplin, which could cause a triple response phenotype on dark-grown Arabidopsis seedlings through ethylene signaling pathway. ran1-1 and ran1-2 are hypersensitive to triplin. Adding copper ions in growth medium could partially restore the phenotype on plant caused by triplin. Mass spectrometry analysis showed that triplin could bind copper ion. Compared to the known chelators, triplin acts more specifically to copper ion and it suppresses the toxic effects of excess copper ions on plant root growth. We further showed that mutants of ANTIOXIDANT PROTEIN1 (ATX1) are hypersensitive to tiplin, but with less sensitivity comparing with the ones of ran1-1 and ran1-2. Our study provided genetic evidence for the first time that, copper ions necessary for ethylene receptor biogenesis and signaling are transported from ATX1 to RAN1. Considering that triplin could chelate copper ions in Arabidopsis, and copper ions are essential for plant and animal, we believe that, triplin not only could be useful for studying copper ion transport of plants, but also could be useful for copper metabolism study in animal and human.

Ventilation heterogeneity is a major determinant of airway hyperresponsiveness in asthma, independent of airway inflammation

PubMed Central

Downie, Sue R; Salome, Cheryl M; Verbanck, Sylvia; Thompson, Bruce; Berend, Norbert; King, Gregory G

2007-01-01

Background Airway hyperresponsiveness is the ability of airways to narrow excessively in response to inhaled stimuli and is a key feature of asthma. Airway inflammation and ventilation heterogeneity have been separately shown to be associated with airway hyperresponsiveness. A study was undertaken to establish whether ventilation heterogeneity is associated with airway hyperresponsiveness independently of airway inflammation in subjects with asthma and to determine the effect of inhaled corticosteroids on this relationship. Methods Airway inflammation was measured in 40 subjects with asthma by exhaled nitric oxide, ventilation heterogeneity by multiple breath nitrogen washout and airway hyperresponsiveness by methacholine challenge. In 18 of these subjects with uncontrolled symptoms, measurements were repeated after 3 months of treatment with inhaled beclomethasone dipropionate. Results At baseline, airway hyperresponsiveness was independently predicted by airway inflammation (partial r2 = 0.20, p<0.001) and ventilation heterogeneity (partial r2 = 0.39, p<0.001). Inhaled corticosteroid treatment decreased airway inflammation (p = 0.002), ventilation heterogeneity (p = 0.009) and airway hyperresponsiveness (p<0.001). After treatment, ventilation heterogeneity was the sole predictor of airway hyperresponsiveness (r2 = 0.64, p<0.001). Conclusions Baseline ventilation heterogeneity is a strong predictor of airway hyperresponsiveness, independent of airway inflammation in subjects with asthma. Its persistent relationship with airway hyperresponsiveness following anti‐inflammatory treatment suggests that it is an important independent determinant of airway hyperresponsiveness. Normalisation of ventilation heterogeneity is therefore a potential goal of treatment that may lead to improved long‐term outcomes. PMID:17311839

Imaging of mucus clearance in the airways of living spontaneously breathing mice by optical coherence microscopy (Conference Presentation)

NASA Astrophysics Data System (ADS)

Pieper, Mario; Schulz-Hildebrandt, Hinnerk; Hüttmann, Gereon; König, Peter

2016-03-01

Mucus transport is essential to remove inhaled particles and pathogens from the lung. Impaired removal of mucus often results in worsening of lung diseases. To understand the mechanisms of mucus transport and to monitor the impact of therapeutic strategies, it is essential to visualize airways and mucus in living animals without disturbing transport processes by intubation or surgically opening the airways. We developed a custom-built optical coherence microscope (OCM) providing a lateral and axial resolution of approximately 1.5 µm with a field of view of 2 mm at up to 150 images/s. Images of the intact trachea and its mucus transport were recorded in anesthetized spontaneously breathing mice. NaCl solution (0.9% and 7%) or Lipopolysaccharide were applied intranasally. OCM resolved detailed structure of the trachea and enabled measuring the airway surface liquid (ASL) thickness through the tracheal wall. Without stimulation, the amount of ASL was only a few µm above the epithelium and remained constant. After intranasal application of 30 µl saline at different concentrations, an early fast cough-like fluid removal with velocities higher than 1 mm/s was observed that removed a high amount of liquid. The ASL thickness increased transiently and quickly returned to levels before stimulation. In contrast to saline, application of Lipopolysaccharide induced substantial mucus release and an additional slow mucus transport by ciliary beating (around 100 µm/s) towards the larynx was observed. In conclusion, OCM is appropriate unique tool to study mechanisms of mucus transport in the airways and effects of therapeutic interventions in living animals.

Ion transport across the biological membrane by computational protein design

NASA Astrophysics Data System (ADS)

Grigoryan, Gevorg

The cellular membrane is impermeable to most of the chemicals the cell needs to take in or discard to survive. Therefore, transporters-a class of transmembrane proteins tasked with shuttling cargo chemicals in and out of the cell-are essential to all cellular life. From existing crystal structures, we know transporters to be complex machines, exquisitely tuned for specificity and controllability. But how could membrane-bound life have evolved if it needed such complex machines to exist first? To shed light onto this question, we considered the task of designing a transporter de novo. As our guiding principle, we took the ``alternating-access model''-a conceptual mechanism stating that transporters work by rocking between two conformations, each exposing the cargo-binding site to either the intra- or the extra-cellular environment. A computational design framework was developed to encode an anti-parallel four-helix bundle that rocked between two alternative states to orchestrate the movement of Zn(II) ions across the membrane. The ensemble nature of both states was accounted for using a free energy-based approach, and sequences were chosen based on predicted formation of the targeted topology in the membrane and bi-stability. A single sequence was prepared experimentally and shown to function as a Zn(II) transporter in lipid vesicles. Further, transport was specific to Zn(II) ions and several control peptides supported the underlying design principles. This included a mutant designed to retain all properties but with reduced rocking, which showed greatly depressed transport ability. These results suggest that early transporters could have evolved in the context of simple topologies, to be later tuned by evolution for improved properties and controllability. Our study also serves as an important advance in computational protein design, showing the feasibility of designing functional membrane proteins and of tuning conformational landscapes for desired function

Estimates of Ionospheric Transport and Ion Loss at Mars

NASA Astrophysics Data System (ADS)

Cravens, T. E.; Hamil, O.; Houston, S.; Bougher, S.; Ma, Y.; Brain, D.; Ledvina, S.

2017-10-01

Ion loss from the topside ionosphere of Mars associated with the solar wind interaction makes an important contribution to the loss of volatiles from this planet. Data from NASA's Mars Atmosphere and Volatile Evolution mission combined with theoretical modeling are now helping us to understand the processes involved in the ion loss process. Given the complexity of the solar wind interaction, motivation exists for considering a simple approach to this problem and for understanding how the loss rates might scale with solar wind conditions and solar extreme ultraviolet irradiance. This paper reviews the processes involved in the ionospheric dynamics. Simple analytical and semiempirical expressions for ion flow speeds and ion loss are derived. In agreement with more sophisticated models and with purely empirical studies, it is found that the oxygen loss rate from ion transport is about 5% (i.e., global O ion loss rate of Qion ≈ 4 × 1024 s-1) of the total oxygen loss rate. The ion loss is found to approximately scale as the square root of the solar ionizing photon flux and also as the square root of the solar wind dynamic pressure. Typical ion flow speeds are found to be about 1 km/s in the topside ionosphere near an altitude of 300 km on the dayside. Not surprisingly, the plasma flow speed is found to increase with altitude due to the decreasing ion-neutral collision frequency.

Inhibition of CD23-mediated IgE transcytosis suppresses the initiation and development of airway allergic inflammation

USDA-ARS?s Scientific Manuscript database

The epithelium lining the airway tract and allergen-specific IgE are considered essential controllers of inflammatory responses to allergens. The human IgE receptor, CD23 (Fc'RII), is capable of transporting IgE or IgE-allergen complexes across the polarized human airway epithelial cell (AEC) monola...

Ion transport in the zebrafish kidney from a human disease angle: possibilities, considerations, and future perspectives.

PubMed

Kersten, Simone; Arjona, Francisco J

2017-01-01

Unique experimental advantages, such as its embryonic/larval transparency, high-throughput nature, and ease of genetic modification, underpin the rapid emergence of the zebrafish (Danio rerio) as a preeminent model in biomedical research. Particularly in the field of nephrology, the zebrafish provides a promising model for studying the physiological implications of human solute transport processes along consecutive nephron segments. However, although the zebrafish might be considered a valuable model for numerous renal ion transport diseases and functional studies of many channels and transporters, not all human renal electrolyte transport mechanisms and human diseases can be modeled in the zebrafish. With this review, we explore the ontogeny of zebrafish renal ion transport, its nephron structure and function, and thereby demonstrate the clinical translational value of this model. By critical assessment of genomic and amino acid conservation of human proteins involved in renal ion handling (channels, transporters, and claudins), kidney and nephron segment conservation, and renal electrolyte transport physiology in the zebrafish, we provide researchers and nephrologists with an indication of the possibilities and considerations of the zebrafish as a model for human renal ion transport. Combined with advanced techniques envisioned for the future, implementation of the zebrafish might expand beyond unraveling pathophysiological mechanisms that underlie distinct genetic or environmentally, i.e., pharmacological and lifestyle, induced renal transport deficits. Specifically, the ease of drug administration and the exploitation of improved genetic approaches might argue for the adoption of the zebrafish as a model for preclinical personalized medicine for distinct renal diseases and renal electrolyte transport proteins. Copyright © 2017 the American Physiological Society.

Intestinal nerves and ion transport: stimuli, reflexes, and responses.

PubMed

Hubel, K A

1985-03-01

The effects of extrinsic and intrinsic nerves on ion and water transport by the intestine are considered and discussed in terms of their possible physiological function. Adrenergic nerves enter the small intestine via mesenteric nerves. Adrenergic tone is usually absent in tissues in vitro but is present in vivo. The nerves increase absorption in response to homeostatic changes associated with acute depletion of extracellular fluid. Cholinergic tone that reduces fluid absorption or causes secretion has been detected in the small intestine of humans, dogs, and cats and in the colon of humans. Extrinsic cholinergic fibers generally do not affect ion transport in small intestine but probably do so in colon. Whether peptides liberated in the mucosa affect enterocytes directly is not clear. Studies on humans and rabbits suggest that the role of substance P is minor. The physiological roles of vasoactive intestinal polypeptide (VIP) and somatostatin remain to be defined. Intraluminal factors also affect ion and water transport. Mucosal rubbing, distension, and cholera toxin cause fluid secretion; acid solutions in the duodenum cause alkaline secretion; these stimuli and hypertonic glucose liberate serotonin into the lumen, the mesenteric venous blood, or both. It has been proposed that the enterochromaffin cell is an epithelial sensory cell that responds to noxious stimuli within the lumen by liberating serotonin. The serotonin initiates a neural reflex through a nicotinic ganglion to liberate a secretagogue that acts on the enterocyte. The function of VIP in this proposed reflex is unclear. The variety of intraluminal stimuli that influence epithelial function implies that there is more than one type of epithelial sensory cell (or sensory mechanism). Prostaglandins may mediate the alkaline secretion caused by acid in the duodenum. There may be other effective substances. Although it has been known for years that intraluminal stimuli affect the coordination of smooth

Fast ion transport at a gas-metal interface

DOE PAGES

McDevitt, Christopher J.; Tang, Xian-Zhu; Guo, Zehua

2017-11-06

Fast ion transport and the resulting fusion yield reduction are computed at a gas-metal interface. The extent of fusion yield reduction is observed to depend sensitively on the charge state of the surrounding pusher material and the width of the atomically mixed region. These sensitivities suggest that idealized boundary conditions often implemented at the gas-pusher interface for the purpose of estimating fast ion loss will likely overestimate fusion reactivity reduction in several important limits. Additionally, the impact of a spatially complex material interface is investigated by considering a collection of droplets of the pusher material immersed in a DT plasma.more » It is found that for small Knudsen numbers, the extent of fusion yield reduction scales with the surface area of the material interface. As the Knudsen number is increased, but, the simple surface area scaling is broken, suggesting that hydrodynamic mix has a nontrivial impact on the extent of fast ion losses.« less

TRPA1 is a major oxidant sensor in murine airway sensory neurons

PubMed Central

Bessac, Bret F.; Sivula, Michael; von Hehn, Christian A.; Escalera, Jasmine; Cohn, Lauren; Jordt, Sven-Eric

2008-01-01

Sensory neurons in the airways are finely tuned to respond to reactive chemicals threatening airway function and integrity. Nasal trigeminal nerve endings are particularly sensitive to oxidants formed in polluted air and during oxidative stress as well as to chlorine, which is frequently released in industrial and domestic accidents. Oxidant activation of airway neurons induces respiratory depression, nasal obstruction, sneezing, cough, and pain. While normally protective, chemosensory airway reflexes can provoke severe complications in patients affected by inflammatory airway conditions like rhinitis and asthma. Here, we showed that both hypochlorite, the oxidizing mediator of chlorine, and hydrogen peroxide, a reactive oxygen species, activated Ca2+ influx and membrane currents in an oxidant-sensitive subpopulation of chemosensory neurons. These responses were absent in neurons from mice lacking TRPA1, an ion channel of the transient receptor potential (TRP) gene family. TRPA1 channels were strongly activated by hypochlorite and hydrogen peroxide in primary sensory neurons and heterologous cells. In tests of respiratory function, Trpa1–/– mice displayed profound deficiencies in hypochlorite- and hydrogen peroxide–induced respiratory depression as well as decreased oxidant-induced pain behavior. Our results indicate that TRPA1 is an oxidant sensor in sensory neurons, initiating neuronal excitation and subsequent physiological responses in vitro and in vivo. PMID:18398506

Modeling water vapor and heat transfer in the normal and the intubated airways.

PubMed

Tawhai, Merryn H; Hunter, Peter J

2004-04-01

Intubation of the artificially ventilated patient with an endotracheal tube bypasses the usual conditioning regions of the nose and mouth. In this situation any deficit in heat or moisture in the air is compensated for by evaporation and thermal transfer from the pulmonary airway walls. To study the dynamics of heat and water transport in the intubated airway, a coupled system of nonlinear equations is solved in airway models with symmetric geometry and anatomically based geometry. Radial distribution of heat, water vapor, and velocity in the airway are described by power-law equations. Solution of the time-dependent system of equations yields dynamic airstream and mucosal temperatures and air humidity. Comparison of model results with two independent experimental studies in the normal and intubated airway shows a close correlation over a wide range of minute ventilation. Using the anatomically based model a range of spatially distributed temperature paths is demonstrated, which highlights the model's ability to predict thermal behavior in airway regions currently inaccessible to measurement. Accurate representation of conducting airway geometry is shown to be necessary for simulating mouth-breathing at rates between 15 and 100 l x min(-1), but symmetric geometry is adequate for the low minute ventilation and warm inspired air conditions that are generally supplied to the intubated patient.

Parasympathetic control of airway submucosal glands: central reflexes and the airway intrinsic nervous system.

PubMed

Wine, Jeffrey J

2007-04-30

Airway submucosal glands produce the mucus that lines the upper airways to protect them against insults. This review summarizes evidence for two forms of gland secretion, and hypothesizes that each is mediated by different but partially overlapping neural pathways. Airway innate defense comprises low level gland secretion, mucociliary clearance and surveillance by airway-resident phagocytes to keep the airways sterile in spite of nearly continuous inhalation of low levels of pathogens. Gland secretion serving innate defense is hypothesized to be under the control of intrinsic (peripheral) airway neurons and local reflexes, and these may depend disproportionately on non-cholinergic mechanisms, with most secretion being produced by VIP and tachykinins. In the genetic disease cystic fibrosis, airway glands no longer secrete in response to VIP alone and fail to show the synergy between VIP, tachykinins and ACh that is observed in normal glands. The consequent crippling of the submucosal gland contribution to innate defense may be one reason that cystic fibrosis airways are infected by mucus-resident bacteria and fungi that are routinely cleared from normal airways. By contrast, the acute (emergency) airway defense reflex is centrally mediated by vagal pathways, is primarily cholinergic, and stimulates copious volumes of gland mucus in response to acute, intense challenges to the airways, such as those produced by very vigorous exercise or aspiration of foreign material. In cystic fibrosis, the acute airway defense reflex can still stimulate the glands to secrete large amounts of mucus, although its properties are altered. Importantly, treatments that recruit components of the acute reflex, such as inhalation of hypertonic saline, are beneficial in treating cystic fibrosis airway disease. The situation for recipients of lung transplants is the reverse; transplanted airways retain the airway intrinsic nervous system but lose centrally mediated reflexes. The consequences

Local Structure and Ion Transport in Glassy Poly(ethylene oxide styrene) Copolymers

NASA Astrophysics Data System (ADS)

Yang, Han-Chang; Mays, Jimmy; Sokolov, Alexei P.; Winey, Karen I.

2014-03-01

Polymer electrolytes have attracted attention for a wide variety of applications in energy production such as lithium-ion batteries and fuel cells. The concept of free volume provides important information about ion mobility and chain dynamics in the polymer matrix. Researchers have recently demonstrated that ion transport in glassy polymer can be improved by designing a system with high free volume. We have studied the effect of temperature and humidity on the intermolecular correlations of poly(ethylene oxide styrene-block-styrene) (PEOSt- b-St) block copolymer and poly(ethylene oxide styrene) (PEOSt) homopolymer using in situ multi-angle x-ray scattering across a wide range of scattering angles (q = 0.007-1.5 Å-1) . An increase in backbone-to-backbone distance is observed, indicating an increase in free volume between different polymer main chains. Structural characterization of the polymer segments will be discussed together with conductivity and dielectric results to better understand the ion transport mechanism in the local environment of the polymer system. Department of Chemistry, University of Tennessee.

Facilitated transport of small molecules and ions for energy-efficient membranes.

PubMed

Li, Yifan; Wang, Shaofei; He, Guangwei; Wu, Hong; Pan, Fusheng; Jiang, Zhongyi

2015-01-07

In nature, the biological membrane can selectively transport essential small molecules/ions through facilitated diffusion via carrier proteins. Intrigued by this phenomenon and principle, membrane researchers have successfully employed synthetic carriers and carrier-mediated reversible reactions to enhance the separation performance of synthetic membranes. However, the existing facilitated transport membranes as well as the relevant facilitated transport theories have scarcely been comprehensively reviewed in the literature. This tutorial review primarily covers the two aspects of facilitated transport theories: carrier-mediated transport mechanisms and facilitated transport chemistries, including the design and fabrication of facilitated transport membranes. The applications of facilitated transport membranes in energy-intensive membrane processes (gas separation, pervaporation, and proton exchange membrane fuel cells) have also been discussed. Hopefully, this review will provide guidelines for the future research and development of facilitated transport membranes with high energy efficiency.

Structure and Function of the Mucus Clearance System of the Lung

PubMed Central

Button, Brenda M.; Button, Brian

2013-01-01

In cystic fibrosis (CF), a defect in ion transport results in thick and dehydrated airway mucus, which is difficult to clear, making such patients prone to chronic inflammation and bacterial infections. Physiotherapy using a variety of airway clearance techniques (ACTs) represents a key treatment regime by helping clear the airways of thickened, adhered, mucus and, thus, reducing the impact of lung infections and improving lung function. This article aims to bridge the gap between our understanding of the physiological effects of mechanical stresses elicited by ACTs on airway epithelia and the reported effectiveness of ACTs in CF patients. In the first part of this review, the effects of mechanical stress on airway epithelia are discussed in relation to changes in ion transport and stimulation in airway surface layer hydration. The second half is devoted to detailing the most commonly used ACTs to stimulate the removal of mucus from the airways of patients with CF. PMID:23751214

Computation of Alfvèn eigenmode stability and saturation through a reduced fast ion transport model in the TRANSP tokamak transport code

DOE Office of Scientific and Technical Information (OSTI.GOV)

Podestà, M.; Gorelenkova, M.; Gorelenkov, N. N.

Alfvénic instabilities (AEs) are well known as a potential cause of enhanced fast ion transport in fusion devices. Given a specific plasma scenario, quantitative predictions of (i) expected unstable AE spectrum and (ii) resulting fast ion transport are required to prevent or mitigate the AE-induced degradation in fusion performance. Reduced models are becoming an attractive tool to analyze existing scenarios as well as for scenario prediction in time-dependent simulations. Here, in this work, a neutral beam heated NSTX discharge is used as reference to illustrate the potential of a reduced fast ion transport model, known as kick model, that hasmore » been recently implemented for interpretive and predictive analysis within the framework of the time-dependent tokamak transport code TRANSP. Predictive capabilities for AE stability and saturation amplitude are first assessed, based on given thermal plasma profiles only. Predictions are then compared to experimental results, and the interpretive capabilities of the model further discussed. Overall, the reduced model captures the main properties of the instabilities and associated effects on the fast ion population. Finally, additional information from the actual experiment enables further tuning of the model's parameters to achieve a close match with measurements.« less

Computation of Alfvèn eigenmode stability and saturation through a reduced fast ion transport model in the TRANSP tokamak transport code

DOE PAGES

Podestà, M.; Gorelenkova, M.; Gorelenkov, N. N.; ...

2017-07-20

Alfvénic instabilities (AEs) are well known as a potential cause of enhanced fast ion transport in fusion devices. Given a specific plasma scenario, quantitative predictions of (i) expected unstable AE spectrum and (ii) resulting fast ion transport are required to prevent or mitigate the AE-induced degradation in fusion performance. Reduced models are becoming an attractive tool to analyze existing scenarios as well as for scenario prediction in time-dependent simulations. Here, in this work, a neutral beam heated NSTX discharge is used as reference to illustrate the potential of a reduced fast ion transport model, known as kick model, that hasmore » been recently implemented for interpretive and predictive analysis within the framework of the time-dependent tokamak transport code TRANSP. Predictive capabilities for AE stability and saturation amplitude are first assessed, based on given thermal plasma profiles only. Predictions are then compared to experimental results, and the interpretive capabilities of the model further discussed. Overall, the reduced model captures the main properties of the instabilities and associated effects on the fast ion population. Finally, additional information from the actual experiment enables further tuning of the model's parameters to achieve a close match with measurements.« less

Impaired organic ion transport in proximal tubules of rats with Heymann nephritis.

PubMed

Park, E K; Hong, S K; Goldinger, J; Andres, G; Noble, B

1985-10-01

Organic ion transport across the basolateral membrane of proximal tubules was measured by means of the tissue slice technique in each of the four different stages of Heymann nephritis. Impairment of both organic anion and cation transport was detected early in Stage 2, and became more severe in Stage 3 of Heymann nephritis. The decreased transport function was associated with extensive damage to proximal tubule cells, including loss of brush border microvilli and basal infoldings. Despite these abnormalities of structure and function, oxygen consumption of proximal tubule cells remained essentially normal. Partial recovery of organic cation transport was noted late in Heymann nephritis (Stage 4). Recovery of the cation transport function was associated with a partial restoration of brush border microvilli and basal infoldings to proximal tubule cells. However, organic anion transport remained depressed throughout the entire course of disease. Impairment of organic ion transport in rats with Heymann nephritis appeared to result from damage to basolateral membrane transport elements rather than general deterioration of the metabolic machinery of proximal tubule cells. Decreased organic cation transport appeared to be the consequence of a reduction in the number of carrier sites, a phenomenon that could have resulted from decreased membrane surface area. However, the depression of organic anion transport was associated with decreased substrate affinity of the anion carrier, indicating that qualitative, rather than quantitative changes, were primarily responsible for that defect. Specific antibody-mediated damage to the anion transport elements in basolateral membranes of proximal tubules is postulated to occur in Heymann nephritis.

Toroidal ripple transport of beam ions in the mega-ampere spherical tokamak

DOE Office of Scientific and Technical Information (OSTI.GOV)

McClements, K. G.; Hole, M. J.

The transport of injected beam ions due to toroidal magnetic field ripple in the mega-ampere spherical tokamak (MAST) is quantified using a full orbit particle tracking code, with collisional slowing-down and pitch-angle scattering by electrons and bulk ions taken into account. It is shown that the level of ripple losses is generally rather low, although it depends sensitively on the major radius of the outer midplane plasma edge; for typical values of this parameter in MAST plasmas, the reduction in beam heating power due specifically to ripple transport is less than 1%, and the ripple contribution to beam ion diffusivitymore » is of the order of 0.1 m{sup 2} s{sup -1} or less. It is concluded that ripple effects make only a small contribution to anomalous transport rates that have been invoked to account for measured neutron rates and plasma stored energies in some MAST discharges. Delayed (non-prompt) losses are shown to occur close to the outer midplane, suggesting that banana-drift diffusion is the most likely cause of the ripple-induced losses.« less

Modeling of negative ion transport in a plasma source

NASA Astrophysics Data System (ADS)

Riz, David; Paméla, Jérôme

1998-08-01

A code called NIETZSCHE has been developed to simulate the negative ion transport in a plasma source, from their birth place to the extraction holes. The ion trajectory is calculated by numerically solving the 3-D motion equation, while the atomic processes of destruction, of elastic collision H-/H+ and of charge exchange H-/H0 are handled at each time step by a Monte-Carlo procedure. This code can be used to calculate the extraction probability of a negative ion produced at any location inside the source. Calculations performed with NIETZSCHE have allowed to explain, either quantitatively or qualitatively, several phenomena observed in negative ion sources, such as the isotopic H-/D- effect, and the influence of the plasma grid bias or of the magnetic filter on the negative ion extraction. The code has also shown that in the type of sources contemplated for ITER, which operate at large arc power densities (>1 W cm-3), negative ions can reach the extraction region provided if they are produced at a distance lower than 2 cm from the plasma grid in the case of «volume production» (dissociative attachment processes), or if they are produced at the plasma grid surface, in the vicinity of the extraction holes.

Ion transport membrane module and vessel system with directed internal gas flow

DOEpatents

Holmes, Michael Jerome; Ohrn, Theodore R.; Chen, Christopher Ming-Poh

2010-02-09

An ion transport membrane system comprising (a) a pressure vessel having an interior, an inlet adapted to introduce gas into the interior of the vessel, an outlet adapted to withdraw gas from the interior of the vessel, and an axis; (b) a plurality of planar ion transport membrane modules disposed in the interior of the pressure vessel and arranged in series, each membrane module comprising mixed metal oxide ceramic material and having an interior region and an exterior region; and (c) one or more gas flow control partitions disposed in the interior of the pressure vessel and adapted to change a direction of gas flow within the vessel.

A three-scale model for ionic solute transport in swelling clays incorporating ion-ion correlation effects

NASA Astrophysics Data System (ADS)

Le, Tien Dung; Moyne, Christian; Murad, Marcio A.

2015-01-01

A new three-scale model is proposed to describe the movement of ionic species of different valences in swelling clays characterized by three separate length scales (nano, micro, and macro) and two levels of porosity (nano- and micropores). At the finest (nano) scale the medium is treated as charged clay particles saturated by aqueous electrolyte solution containing monovalent and divalent ions forming the electrical double layer. A new constitutive law is constructed for the disjoining pressure based on the numerical resolution of non-local problem at the nanoscale which, in contrast to the Poisson-Boltzmann theory for point charge ions, is capable of capturing the short-range interactions between the ions due to their finite size. At the intermediate scale (microscale), the two-phase homogenized particle/electrolyte solution system is represented by swollen clay clusters (or aggregates) with the nanoscale disjoining pressure incorporated in a modified form of Terzaghi's effective principle. At the macroscale, the electro-chemical-mechanical couplings within clay clusters is homogenized with the ion transport in the bulk fluid lying in the micro pores. The resultant macroscopic picture is governed by a three-scale model wherein ion transport takes place in the bulk solution strongly coupled with the mechanics of the clay clusters which play the role of sources/sinks of mass to the bulk fluid associated with ion adsorption/desorption in the electrical double layer at the nanoscale. Within the context of the quasi-steady version of the multiscale model, wherein the electrolyte solution in the nanopores is assumed at instantaneous thermodynamic equilibrium with the bulk fluid in the micropores, we build-up numerically the ion-adsorption isotherms along with the constitutive law of the retardation coefficients of monovalent and divalent ions. In addition, the constitutive law for the macroscopic swelling pressure is reconstructed numerically showing patterns of

Lunar Ion Transport Near Magnetic Anomalies: Possible Implications for Swirl Formation

NASA Technical Reports Server (NTRS)

Keller, J. W.; Killen, R. M.; Stubbs, T. J.; Farrell, W. M.; Halekas, J. S.

2011-01-01

The bright swirling features on the lunar surface in areas around the Moon but most prominently at Reiner Gamma, have intrigued scientists for many years. After Apollo and later Lunar Prospector (LP} mapped the Lunar magnetic fields from orbit, it was observed that these features are generally associated with crustal magnetic anomalies. This led researchers to propose a number of explanations for the swirls that invoke these fields. Prominent among these include magnetic shielding in the form of a mini-magnetosphere which impedes space weathering by the solar wind, magnetically controlled dust transport, and cometary or asteroidal impacts that would result in shock magnetization with concomitant formation ofthe swirls. In this presentation, we will consider another possibility, that the ambient magnetic and electric fields can transport and channel secondary ions produced by micrometeorite or solar wind ion impacts. In this scenario, ions that are created in these impacts are under the influence of these fields and can drift for significant distances before encountering the magnetic anomalies when their trajectories are disrupted and concentrated onto nearby areas. These ions may then be responsible for chemical alteration of the surface leading either to a brightening effect or a disruption of space weathering processes. To test this hypothesis we have run ion trajectory simulations that show ions from regions about the magnetic anomalies can be channeled into very small areas near the anomalies and although questions remain as to nature of the mechanisms that could lead to brightening of the surface it appears that the channeling effect is consistent with the existence of the swirls.

Host-microbe interactions in distal airways: relevance to chronic airway diseases.

PubMed

Martin, Clémence; Burgel, Pierre-Régis; Lepage, Patricia; Andréjak, Claire; de Blic, Jacques; Bourdin, Arnaud; Brouard, Jacques; Chanez, Pascal; Dalphin, Jean-Charles; Deslée, Gaetan; Deschildre, Antoine; Gosset, Philippe; Touqui, Lhousseine; Dusser, Daniel

2015-03-01

This article is the summary of a workshop, which took place in November 2013, on the roles of microorganisms in chronic respiratory diseases. Until recently, it was assumed that lower airways were sterile in healthy individuals. However, it has long been acknowledged that microorganisms could be identified in distal airway secretions from patients with various respiratory diseases, including cystic fibrosis (CF) and non-CF bronchiectasis, chronic obstructive pulmonary disease, asthma and other chronic airway diseases (e.g. post-transplantation bronchiolitis obliterans). These microorganisms were sometimes considered as infectious agents that triggered host immune responses and contributed to disease onset and/or progression; alternatively, microorganisms were often considered as colonisers, which were considered unlikely to play roles in disease pathophysiology. These concepts were developed at a time when the identification of microorganisms relied on culture-based methods. Importantly, the majority of microorganisms cannot be cultured using conventional methods, and the use of novel culture-independent methods that rely on the identification of microorganism genomes has revealed that healthy distal airways display a complex flora called the airway microbiota. The present article reviews some aspects of current literature on host-microbe (mostly bacteria and viruses) interactions in healthy and diseased airways, with a special focus on distal airways. Copyright ©ERS 2015.

The New Perilaryngeal Airway (CobraPLA™)1 Is as Efficient as the Laryngeal Mask Airway (LMA™)2, But Provides Better Airway Sealing Pressures

PubMed Central

Akça, Ozan; Wadhwa, Anupama; Sengupta, Papiya; Durrani, Jaleel; Hanni, Keith; Wenke, Mary; Yücel, Yüksel; Lenhardt, Rainer; Doufas, Anthony G.; Sessler, Daniel I.

2006-01-01

The Laryngeal Mask Airway (LMA) is a frequently-used efficient airway device, yet it sometimes seals poorly, thus reducing the efficacy of positive-pressure ventilation. The Perilaryngeal Airway (CobraPLA) is a novel airway device with a larger pharyngeal cuff (when inflated). We tested the hypothesis that the CobraPLA was superior to LMA with regard to insertion time and airway sealing pressure and comparable to LMA in airway adequacy and recovery characteristics. After midazolam and fentanyl, 81 ASA I-II outpatients having elective surgery were randomized to receive an LMA or CobraPLA. Anesthesia was induced with propofol (2.5 mg/kg, IV), and the airway inserted. We measured 1) insertion time; 2) adequacy of the airway (no leak at 15-cm-H2O peak pressure or tidal volume of 5 ml/kg); 3) airway sealing pressure; 4) number of repositioning attempts; and 5) sealing quality (no leak at tidal volume of 8 ml/kg). At the end of surgery, gastric insufflation, postoperative sore throat, dysphonia, and dysphagia were evaluated. Data were compared with unpaired t-tests, chi-square tests, or Fisher’s Exact tests; P<0.05 was significant. Patient characteristics, insertion times, airway adequacy, number of repositioning attempts, and recovery were similar in each group. Airway sealing pressure was significantly greater with CobraPLA (23±6 cm H2O) than LMA (18±5 cm H2O, P<0.001). The CobraPLA has insertion characteristics similar to LMA, but better airway sealing capabilities. PMID:15281543

Brownian dynamics study of ion transport in the vestibule of membrane channels.

PubMed

Li, S C; Hoyles, M; Kuyucak, S; Chung, S H

1998-01-01

Brownian dynamics simulations have been carried out to study the transport of ions in a vestibular geometry, which offers a more realistic shape for membrane channels than cylindrical tubes. Specifically, we consider a torus-shaped channel, for which the analytical solution of Poisson's equation is possible. The system is composed of the toroidal channel, with length and radius of the constricted region of 80 A and 4 A, respectively, and two reservoirs containing 50 sodium ions and 50 chloride ions. The positions of each of these ions executing Brownian motion under the influence of a stochastic force and a systematic electric force are determined at discrete time steps of 50 fs for up to 2.5 ns. All of the systematic forces acting on an ion due to the other ions, an external electric field, fixed charges in the channel protein, and the image charges induced at the water-protein boundary are explicitly included in the calculations. We find that the repulsive dielectric force arising from the induced surface charges plays a dominant role in channel dynamics. It expels an ion from the vestibule when it is deliberately put in it. Even in the presence of an applied electric potential of 100 mV, an ion cannot overcome this repulsive force and permeate the channel. Only when dipoles of a favorable orientation are placed along the sides of the transmembrane segment can an ion traverse the channel under the influence of a membrane potential. When the strength of the dipoles is further increased, an ion becomes detained in a potential well, and the driving force provided by the applied field is not sufficient to drive the ion out of the well. The trajectory of an ion navigating across the channel mostly remains close to the central axis of the pore lumen. Finally, we discuss the implications of these findings for the transport of ions across the membrane.

Insights into the ion-coupling mechanism in the MATE transporter NorM-VC

NASA Astrophysics Data System (ADS)

Krah, Alexander; Zachariae, Ulrich

2017-08-01

Bacteria have developed a variety of different mechanisms to defend themselves from compounds that are toxic to them, such as antibiotics. One of these defence mechanisms is the expulsion of drugs or other noxious compounds by multidrug efflux pumps. Multidrug and toxic compound extrusion (MATE) transporters are efflux pumps that extrude metabolic waste and a variety of antibiotics out of the cell, using an ion gradient as energy source. They function via an alternating-access mechanism. When ions bind in the outward facing conformation, a large conformational change to the inward facing conformation is induced, from which the ion is released and the extruded chemical compound is bound. NorM proteins, which are usually coupled to a Na+ gradient, are members of the MATE family. However, for NorM-VC from Vibrio cholerae, it has been shown that this MATE transporter is additionally coupled to protons. How H+ and Na+ binding are coupled mechanistically to enable drug antiport is not well understood. In this study, we use molecular dynamics simulations to illuminate the sequence of ion binding events that enable efflux. Understanding this antiport mechanism is important to support the development of novel compounds that specifically inhibit the functional cycle of NorM transporters.

Airway surface mycosis in chronic TH2-associated airway disease.

PubMed

Porter, Paul C; Lim, Dae Jun; Maskatia, Zahida Khan; Mak, Garbo; Tsai, Chu-Lin; Citardi, Martin J; Fakhri, Samer; Shaw, Joanne L; Fothergil, Annette; Kheradmand, Farrah; Corry, David B; Luong, Amber

2014-08-01

Environmental fungi have been linked to TH2 cell-related airway inflammation and the TH2-associated chronic airway diseases asthma, chronic rhinosinusitis (CRS) with nasal polyps (CRSwNP), and allergic fungal rhinosinusitis (AFRS), but whether these organisms participate directly or indirectly in disease pathology remains unknown. To determine the frequency of fungus isolation and fungus-specific immunity in patients with TH2-associated and non-TH2-associated airway disease. Sinus lavage fluid and blood were collected from sinus surgery patients (n = 118) including patients with CRSwNP, patients with CRS without nasal polyps, patients with AFRS, and non-CRS/nonasthmatic control patients. Asthma status was determined from medical history. Sinus lavage fluids were cultured and directly examined for evidence of viable fungi. PBMCs were restimulated with fungal antigens in an enzyme-linked immunocell spot assay to determine total memory fungus-specific IL-4-secreting cells. These data were compared with fungus-specific IgE levels measured from plasma by ELISA. Filamentous fungi were significantly more commonly cultured in patients with TH2-associated airway disease (asthma, CRSwNP, or AFRS: n = 68) than in control patients with non-TH2-associated disease (n = 31): 74% vs 16%, respectively (P < .001). Both fungus-specific IL-4 enzyme-linked immunocell spot (n = 48) and specific IgE (n = 70) data correlated with TH2-associated diseases (sensitivity 73% and specificity 100% vs 50% and 77%, respectively). The frequent isolation of fungi growing directly within the airways accompanied by specific immunity to these organisms only in patients with TH2-associated chronic airway diseases suggests that fungi participate directly in the pathogenesis of these conditions. Efforts to eradicate airway fungi from the airways should be considered in selected patients. Copyright © 2014 American Academy of Allergy, Asthma & Immunology. Published by Mosby, Inc. All rights reserved.

Cystic Fibrosis Transmembrane Conductance Regulator in Sarcoplasmic Reticulum of Airway Smooth Muscle. Implications for Airway Contractility

PubMed Central

Cook, Daniel P.; Rector, Michael V.; Bouzek, Drake C.; Michalski, Andrew S.; Gansemer, Nicholas D.; Reznikov, Leah R.; Li, Xiaopeng; Stroik, Mallory R.; Ostedgaard, Lynda S.; Abou Alaiwa, Mahmoud H.; Thompson, Michael A.; Prakash, Y. S.; Krishnan, Ramaswamy; Meyerholz, David K.; Seow, Chun Y.

2016-01-01

Rationale: An asthma-like airway phenotype has been described in people with cystic fibrosis (CF). Whether these findings are directly caused by loss of CF transmembrane conductance regulator (CFTR) function or secondary to chronic airway infection and/or inflammation has been difficult to determine. Objectives: Airway contractility is primarily determined by airway smooth muscle. We tested the hypothesis that CFTR is expressed in airway smooth muscle and directly affects airway smooth muscle contractility. Methods: Newborn pigs, both wild type and with CF (before the onset of airway infection and inflammation), were used in this study. High-resolution immunofluorescence was used to identify the subcellular localization of CFTR in airway smooth muscle. Airway smooth muscle function was determined with tissue myography, intracellular calcium measurements, and regulatory myosin light chain phosphorylation status. Precision-cut lung slices were used to investigate the therapeutic potential of CFTR modulation on airway reactivity. Measurements and Main Results: We found that CFTR localizes to the sarcoplasmic reticulum compartment of airway smooth muscle and regulates airway smooth muscle tone. Loss of CFTR function led to delayed calcium reuptake following cholinergic stimulation and increased myosin light chain phosphorylation. CFTR potentiation with ivacaftor decreased airway reactivity in precision-cut lung slices following cholinergic stimulation. Conclusions: Loss of CFTR alters porcine airway smooth muscle function and may contribute to the airflow obstruction phenotype observed in human CF. Airway smooth muscle CFTR may represent a therapeutic target in CF and other diseases of airway narrowing. PMID:26488271

Collisionality dependence and ion species effects on heat transport in He and H plasma, and the role of ion scale turbulence in LHD

NASA Astrophysics Data System (ADS)

Tanaka, K.; Nagaoka, K.; Murakami, S.; Takahashi, H.; Osakabe, M.; Yokoyama, M.; Seki, R.; Michael, C. A.; Yamaguchi, H.; Suzuki, C.; Shimizu, A.; Tokuzawa, T.; Yoshinuma, M.; Akiyama, T.; Ida, K.; Yamada, I.; Yasuhara, R.; Funaba, H.; Kobayashi, T.; Yamada, H.; Du, X. D.; Vyacheslavov, L. N.; Mikkelsen, D. R.; Yun, G. S.; the LHD Experimental Group

2017-11-01

Surveys of the ion and electron heat transports of neutral beam (NB) heating plasma were carried out by power balance analysis in He and H rich plasma at LHD. Collisionality was scanned by changing density and heating power. The characteristics of the transport vary depending on collisionality. In low collisionality, with low density and high heating power, an ion internal transport barrier (ITB) was formed. The ion heat conductivity (χ i) is lower than electron heat conductivity (χ e) in the core region at ρ  <  0.7. On the other hand, in high collisionality, with high density and low heating power, χ i is higher than χ e across the entire range of plasma. These different confinement regimes are associated with different fluctuation characteristics. In ion ITB, fluctuation has a peak at ρ  =  0.7, and in normal confinement, fluctuation has a peak at ρ  =  1.0. The two confinement modes change gradually depending on the collisionality. Scans of concentration ratio between He and H were also performed. The ion confinement improvements were investigated using gyro-Bohm normalization, taking account of the effective mass and charge. The concentration ratio affected the normalized χ i only in the edge region (ρ ~ 1.0). This indicates ion species effects vary depending on collisionality. Turbulence was modulated by the fast ion loss instability. The modulation of turbulence is higher in H rich than in He rich plasma.

Apparatus, Method and Program Storage Device for Determining High-Energy Neutron/Ion Transport to a Target of Interest

NASA Technical Reports Server (NTRS)

Wilson, John W. (Inventor); Tripathi, Ram K. (Inventor); Cucinotta, Francis A. (Inventor); Badavi, Francis F. (Inventor)

2012-01-01

An apparatus, method and program storage device for determining high-energy neutron/ion transport to a target of interest. Boundaries are defined for calculation of a high-energy neutron/ion transport to a target of interest; the high-energy neutron/ion transport to the target of interest is calculated using numerical procedures selected to reduce local truncation error by including higher order terms and to allow absolute control of propagated error by ensuring truncation error is third order in step size, and using scaling procedures for flux coupling terms modified to improve computed results by adding a scaling factor to terms describing production of j-particles from collisions of k-particles; and the calculated high-energy neutron/ion transport is provided to modeling modules to control an effective radiation dose at the target of interest.

Transport and Deposition of Welding Fume Agglomerates in a Realistic Human Nasal Airway.

PubMed

Tian, Lin; Inthavong, Kiao; Lidén, Göran; Shang, Yidan; Tu, Jiyuan

2016-07-01

Welding fume is a complex mixture containing ultra-fine particles in the nanometer range. Rather than being in the form of a singular sphere, due to the high particle concentration, welding fume particles agglomerate into long straight chains, branches, or other forms of compact shapes. Understanding the transport and deposition of these nano-agglomerates in human respiratory systems is of great interest as welding fumes are a known health hazard. The neurotoxin manganese (Mn) is a common element in welding fumes. Particulate Mn, either as soluble salts or oxides, that has deposited on the olfactory mucosa in human nasal airway is transported along the olfactory nerve to the olfactory bulb within the brain. If this Mn is further transported to the basal ganglia of the brain, it could accumulate at the part of the brain that is the focal point of its neurotoxicity. Accounting for various dynamic shape factors due to particle agglomeration, the current computational study is focused on the exposure route, the deposition pattern, and the deposition efficiency of the inhaled welding fume particles in a realistic human nasal cavity. Particular attention is given to the deposition pattern and deposition efficiency of inhaled welding fume agglomerates in the nasal olfactory region. For particles in the nanoscale, molecular diffusion is the dominant transport mechanism. Therefore, Brownian diffusion, hydrodynamic drag, Saffman lift force, and gravitational force are included in the model study. The deposition efficiencies for single spherical particles, two kinds of agglomerates of primary particles, two-dimensional planar and straight chains, are investigated for a range of primary particle sizes and a range of number of primary particles per agglomerate. A small fraction of the inhaled welding fume agglomerates is deposited on the olfactory mucosa, approximately in the range 0.1-1%, and depends on particle size and morphology. The strong size dependence of the deposition

A Hierarchy of Transport Approximations for High Energy Heavy (HZE) Ions

NASA Technical Reports Server (NTRS)

Wilson, John W.; Lamkin, Stanley L.; Hamidullah, Farhat; Ganapol, Barry D.; Townsend, Lawrence W.

1989-01-01

The transport of high energy heavy (HZE) ions through bulk materials is studied neglecting energy dependence of the nuclear cross sections. A three term perturbation expansion appears to be adequate for most practical applications for which penetration depths are less than 30 g per sq cm of material. The differential energy flux is found for monoenergetic beams and for realistic ion beam spectral distributions. An approximate formalism is given to estimate higher-order terms.

Ion transport and softening in a polymerized ionic liquid

DOE PAGES

Kumar, Rajeev; Bocharova, Vera; Strelcov, Evgheni; ...

2014-11-13

Polymerized ionic liquids (PolyILs) are promising materials for various solid state electronic applications such as dye-sensitized solar cells, lithium batteries, actuators, field-effect transistors, light emitting electrochemical cells, and electrochromic devices. However, fundamental understanding of interconnection between ionic transport and mechanical properties in PolyILs is far from complete. In this paper, local charge transport and structural changes in films of a PolyIL are studied using an integrated experiment-theory based approach. Experimental data for the kinetics of charging and steady state current–voltage relations can be explained by taking into account the dissociation of ions under an applied electric field (known as themore » Wien effect). Onsager's theory of the Wien effect coupled with the Poisson–Nernst–Planck formalism for the charge transport is found to be in excellent agreement with the experimental results. The agreement between the theory and experiments allows us to predict structural properties of the PolyIL films. We have observed significant softening of the PolyIL films beyond certain threshold voltages and formation of holes under a scanning probe microscopy (SPM) tip, through which an electric field was applied. Finally, the observed softening is explained by the theory of depression in glass transition temperature resulting from enhanced dissociation of ions with an increase in applied electric field.« less

Airway smooth muscle in airway reactivity and remodeling: what have we learned?

PubMed Central

2013-01-01

It is now established that airway smooth muscle (ASM) has roles in determining airway structure and function, well beyond that as the major contractile element. Indeed, changes in ASM function are central to the manifestation of allergic, inflammatory, and fibrotic airway diseases in both children and adults, as well as to airway responses to local and environmental exposures. Emerging evidence points to novel signaling mechanisms within ASM cells of different species that serve to control diverse features, including 1) [Ca2+]i contractility and relaxation, 2) cell proliferation and apoptosis, 3) production and modulation of extracellular components, and 4) release of pro- vs. anti-inflammatory mediators and factors that regulate immunity as well as the function of other airway cell types, such as epithelium, fibroblasts, and nerves. These diverse effects of ASM “activity” result in modulation of bronchoconstriction vs. bronchodilation relevant to airway hyperresponsiveness, airway thickening, and fibrosis that influence compliance. This perspective highlights recent discoveries that reveal the central role of ASM in this regard and helps set the stage for future research toward understanding the pathways regulating ASM and, in turn, the influence of ASM on airway structure and function. Such exploration is key to development of novel therapeutic strategies that influence the pathophysiology of diseases such as asthma, chronic obstructive pulmonary disease, and pulmonary fibrosis. PMID:24142517

Ion Transport and Acceleration at Dipolarization Fronts: High-Resolution MHD/Test-Particle Simulations

NASA Astrophysics Data System (ADS)

Ukhorskiy, A. Y.; Sorathia, K.; Merkin, V. G.; Sitnov, M. I.; Mitchell, D. G.; Wiltberger, M. J.; Lyon, J.

2017-12-01

Much of plasma heating and transport from the magnetotail into the inner magnetosphere occurs in the form of mesoscale discrete injections associated with sharp dipolarizations of magnetic field (dipolarization fronts). In this study we investigate the mechanisms of ion acceleration at dipolarization fronts in a high-resolution global magnetospheric MHD model (LFM). We use large-scale three-dimensional test-particle simulations (CHIMP) to address the following science questions: 1) what are the characteristic scales of dipolarization regions that can stably trap ions? 2) what role does the trapping play in ion transport and acceleration? 3) how does it depend on particle energy and distance from Earth? 4) to what extent ion acceleration is adiabatic? High-resolution LFM was run using idealized solar wind conditions with fixed nominal values of density and velocity and a southward IMF component of -5 nT. To simulate ion interaction with dipolarization fronts, a large ensemble of test particles distributed in energy, pitch-angle, and gyrophase was initialized inside one of the LFM dipolarization channels in the magnetotail. Full Lorentz ion trajectories were then computed over the course of the front inward propagation from the distance of 17 to 6 Earth radii. A large fraction of ions with different initial energies stayed in phase with the front over the entire distance. The effect of magnetic trapping at different energies was elucidated with a correlation of the ion guiding center and the ExB drift velocities. The role of trapping in ion energization was quantified by comparing the partial pressure of ions that exhibit trapping to the pressure of all trapped ions.

Ion confinement and transport in a toroidal plasma with externally imposed radial electric fields

NASA Technical Reports Server (NTRS)

Roth, J. R.; Krawczonek, W. M.; Powers, E. J.; Kim, Y. C.; Hong, H. Y.

1979-01-01

Strong electric fields were imposed along the minor radius of the toroidal plasma by biasing it with electrodes maintained at kilovolt potentials. Coherent, low-frequency disturbances characteristic of various magnetohydrodynamic instabilities were absent in the high-density, well-confined regime. High, direct-current radial electric fields with magnitudes up to 135 volts per centimeter penetrated inward to at least one-half the plasma radius. When the electric field pointed radially toward, the ion transport was inward against a strong local density gradient; and the plasma density and confinement time were significantly enhanced. The radial transport along the electric field appeared to be consistent with fluctuation-induced transport. With negative electrode polarity the particle confinement was consistent with a balance of two processes: a radial infusion of ions, in those sectors of the plasma not containing electrodes, that resulted from the radially inward fields; and ion losses to the electrodes, each of the which acted as a sink and drew ions out of the plasma. A simple model of particle confinement was proposed in which the particle confinement time is proportional to the plasma volume. The scaling predicted by this model was consistent with experimental measurements.

Laryngeal mask airway for airway control during percutaneous dilatational tracheostomy.

PubMed

Pratt, T; Bromilow, J

2011-11-01

Percutaneous dilatational tracheostomy is a common bedside procedure in critical care for patients requiring prolonged mechanical ventilation. The traditional technique requires withdrawal of the endotracheal tube to a proximal position to facilitate tracheostomy insertion, but this carries the risk of inadvertent extubation and does not prevent cuff rupture. Use of a supraglottic airway such as the laryngeal mask airway may avoid these risks and could provide a safe alternative to the endotracheal tube. We present an appraisal of the literature to date. We found reasonable evidence to show improved ventilation and bronchoscopic visualisation with the laryngeal mask airway, but this has not been translated into improved outcome. There is currently insufficient evidence to draw conclusions about the safety of the laryngeal mask airway during percutaneous dilatational tracheostomy.

Modeling of negative ion transport in a plasma source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Riz, David; Departement de Recherches sur la Fusion Controelee CE Cadarache, 13108 St Paul lez Durance; Pamela, Jerome

1998-08-20

A code called NIETZSCHE has been developed to simulate the negative ion transport in a plasma source, from their birth place to the extraction holes. The ion trajectory is calculated by numerically solving the 3-D motion equation, while the atomic processes of destruction, of elastic collision H{sup -}/H{sup +} and of charge exchange H{sup -}/H{sup 0} are handled at each time step by a Monte-Carlo procedure. This code can be used to calculate the extraction probability of a negative ion produced at any location inside the source. Calculations performed with NIETZSCHE have allowed to explain, either quantitatively or qualitatively, severalmore » phenomena observed in negative ion sources, such as the isotopic H{sup -}/D{sup -} effect, and the influence of the plasma grid bias or of the magnetic filter on the negative ion extraction. The code has also shown that in the type of sources contemplated for ITER, which operate at large arc power densities (>1 W cm{sup -3}), negative ions can reach the extraction region provided if they are produced at a distance lower than 2 cm from the plasma grid in the case of 'volume production' (dissociative attachment processes), or if they are produced at the plasma grid surface, in the vicinity of the extraction holes.« less