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Sample records for active na transport

  1. Ionic dependence of active Na-K transport: "clamping" of cellular Na+ with monensin.

    PubMed

    Haber, R S; Pressley, T A; Loeb, J N; Ismail-Beigi, F

    1987-07-01

    The Na+ ionophore monensin was used to study the Na+- and K+-dependence of ouabain-inhibitable 86Rb+ uptake in ARL 15 cells, a rat liver cell line. Graded concentrations of monensin rapidly induced incremental elevations of cellular Na+ that were stable for up to 2 h. In experiments in which cellular Na+ was thus "clamped" at various levels, the activation curve for ouabain-inhibitable 86Rb+ uptake as a function of intracellular Na+ was found to be steepest near basal Na+ levels (Hill coefficient approximately equal to 2.4), indicating that these cells can respond to relatively large changes in passive Na+ entry by increasing the race of Na-K pump function with only minimal increases in cellular Na+. Exposure of cells to monensin also permitted examination of the extracellular-K+ dependence of ouabain-inhibitable 86Rb+ uptake in the presence of saturating intracellular Na+ and yielded a Hill coefficient of approximately 1.5. The rate of ATP hydrolysis calculated from measurements of the maximal rate of ouabain-inhibitable 86Rb+ uptake in intact cells was similar to the enzymatic Vmax of the Na+-K+-ATPase in cell lysates, suggesting that the Na+-K+-ATPase activity in these broken-cell preparations closely reflects the functional transport capacity of the Na-K pump.

  2. Prolactin increases hepatic Na+/taurocholate co-transport activity and messenger RNA post partum.

    PubMed Central

    Ganguly, T C; Liu, Y; Hyde, J F; Hagenbuch, B; Meier, P J; Vore, M

    1994-01-01

    We have shown that Na+/taurocholate co-transport activity is decreased in pregnancy, but rebounds post partum relative to non-pregnant controls, and that activity can be increased by treatment with ovine prolactin [Ganguly, Hyde and Vore (1993) J. Pharmacol. Exp. Ther. 267, 82-87]. To determine the basis for these effects, Na+/taurocholate co-transport was determined in purified basolateral liver plasma-membrane (bLPM) vesicles and compared with steady-state mRNA levels encoding the Na+/taurocholate-co-transporting polypeptide (Ntcp) in non-pregnant controls, pregnant rats (19-20 days pregnant), rats post partum (48 h post partum) and rats post partum treated with bromocriptine to inhibit prolactin secretion. Na+/taurocholate co-transport activity (nmol/5 s per mg of protein) in bLPM was decreased from 10.4 +/- 1.8 in non-pregnant controls to 7.9 +/- 0.6 in bLPM in pregnant rats, but rebounded to 17.5 +/- 1.3 post partum; treatment of rats post partum with bromocriptine to inhibit prolactin secretion decreased activity to 14.1 +/- 0.9. Northern and slot-blot analyses revealed similar changes in mRNA for Ntcp, so that a positive correlation was observed between Na+/taurocholate co-transport activity and Ntcp mRNA. Furthermore, treatment of ovariectomized rats with ovine prolactin increased Ntcp mRNA 10-fold compared with solvent-treated controls, consistent with the 2-fold increase in Vmax, for Na+/taurocholate co-transport in isolated hepatocytes. These data are the first to demonstrate endogenous physiological regulation by prolactin of Ntcp mRNA in parallel with Na+/taurocholate co-transport activity. Images Figure 2 PMID:7945260

  3. Evidence for active maternal-fetal transport of Na+ across the placenta of the anaesthetized rat.

    PubMed

    Stulc, J; Stulcová, B; Sibley, C P

    1993-10-01

    1. In order to investigate mechanisms of Na+ transfer, the unidirectional maternal-fetal clearance (Kmf) of 22Na+ and of 51Cr-EDTA (a marker of paracellular diffusion) was measured across the intact or umbilically or dually perfused placenta of the anaesthetized rat. 2. The Kmf of 22Na+ in the intact preparation (18.5 +/- 2.7 microliters min-1, mean +/- S.D., n = 105 placentas) exceeded that of 51Cr-EDTA in the same experiments (1.4 +/- 0.3 microliters min-1) by more than ten times, whereas the difference in their diffusion coefficients in water was only 2-fold. In the perfused preparations the difference in the Kmf values was 6-fold. 3. Assuming that a simple model of paracellular diffusion through wide pores was one component of transfer, the Kmf of 51Cr-EDTA and the diffusion coefficients were used to calculate a component of 22Na+ clearance (Kmf,residual) and of Na+ flux (Jmf,residual) across the perfused placentas which could not be accounted for by transfer through the paracellular route. 4. Kmf,residual of 22Na+ across the dually perfused placenta was significantly lower when temperature was reduced, the temperature quotient (Q10) of the transfer being about 2. Kmf,residual was also significantly lower when 0.1 mM ouabain was perfused on the fetal side. Jmf,residual exhibited saturation kinetics characterized by an apparent Michaelis constant (Km) of 90 mM. Kmf,residual was not influenced by 0.5 mM frusemide, 0.5 mM amiloride or by 0.5 mM hydrochlorothiazide administered to the maternal side. It was significantly increased by 1 mM alanine on the maternal side suggesting that the coupled transfer of Na+ and amino acids may contribute significantly to the maternal-fetal flux of Na+. 5. These observations suggest that most (80%) of the maternal-fetal flux of Na+ across the rat placenta is effected by active transcellular transport. This transport involves passive entry of Na+ into the trophoblast from the maternal side by a largely unknown saturable mechanism

  4. Salt Stress in Thellungiella halophila Activates Na+ Transport Mechanisms Required for Salinity Tolerance1

    PubMed Central

    Vera-Estrella, Rosario; Barkla, Bronwyn J.; García-Ramírez, Liliana; Pantoja, Omar

    2005-01-01

    Salinity is considered one of the major limiting factors for plant growth and agricultural productivity. We are using salt cress (Thellungiella halophila) to identify biochemical mechanisms that enable plants to grow in saline conditions. Under salt stress, the major site of Na+ accumulation occurred in old leaves, followed by young leaves and taproots, with the least accumulation occurring in lateral roots. Salt treatment increased both the H+ transport and hydrolytic activity of salt cress tonoplast (TP) and plasma membrane (PM) H+-ATPases from leaves and roots. TP Na+/H+ exchange was greatly stimulated by growth of the plants in NaCl, both in leaves and roots. Expression of the PM H+-ATPase isoform AHA3, the Na+ transporter HKT1, and the Na+/H+ exchanger SOS1 were examined in PMs isolated from control and salt-treated salt cress roots and leaves. An increased expression of SOS1, but no changes in levels of AHA3 and HKT1, was observed. NHX1 was only detected in PM fractions of roots, and a salt-induced increase in protein expression was observed. Analysis of the levels of expression of vacuolar H+-translocating ATPase subunits showed no major changes in protein expression of subunits VHA-A or VHA-B with salt treatment; however, VHA-E showed an increased expression in leaf tissue, but not in roots, when the plants were treated with NaCl. Salt cress plants were able to distribute and store Na+ by a very strict control of ion movement across both the TP and PM. PMID:16244148

  5. Hypotonic stimulation of the Na+ active transport in frog skeletal muscle: role of the cytoskeleton

    PubMed Central

    Venosa, R A

    2003-01-01

    Hypotonicity produces a marked activation of the Na+ pump in frog sartorius muscle. The increase in net Na+ efflux under hypotonic conditions occurs despite the reductions in [Na+]i that are due to fibre swelling and Na+ loss. The pump density (ouabain binding) increases not only upon reduction of the medium osmotic pressure (π) from its normal value (π= 1) to one-half (π= 0.5), but also in muscles that are returned to π= 1 after equilibration in π= 2 medium. The equilibration in π= 2 medium does not affect pump density. Ouabain-binding increments cannot be ascribed to a rise in the Na+–K+ exchange rate of a fixed number of pumps: they also occurred in the continued presence of a saturating concentration of ouabain (50 μm). Under those conditions, the π= 1 →π= 0.5 transfer produced a 43 % increase in pump sites, while the π= 2 →π= 1 transfer induced a rise of 46 %. Actinomycin D did not alter the stimulation of Na+ extrusion elicited by hypotonicity, suggesting that de novo synthesis of pumps was not involved in the increase of the apparent number of pump sites. Disruption of microtubules by colchicine (100 μm) and intermediate filaments by acrylamide (4 mm) did not alter the hypotonic effect. Likewise, genistein (100 μm), a specific inhibitor of tyrosine kinase, did not affect significantly the hypotonic response. Microfilament-disrupting agents like cytochalasin B (5 μm) and latrunculin B (10 μm) reduced the increase in Na+ efflux induced by π= 1 →π= 0.5 transfer by about 35 % and 72 %, respectively. Latrunculin B reduced the increases in pump density generated by π= 1 →π= 0.5 and π= 2 →π= 1 transfers by about 79 % and 91 %, respectively. The results suggest that the membrane stretch due to hypotonic fibre volume increase would promote a microfilament-mediated insertion of submembranous spare Na+ pumps in the sarcolemma and, consequently, the rise in active Na+ transport. PMID:12598593

  6. Facilitation by intracellular carbonic anhydrase of Na+–HCO3− co-transport but not Na+/H+ exchange activity in the mammalian ventricular myocyte

    PubMed Central

    Villafuerte, Francisco C; Swietach, Pawel; Youm, Jae-Boum; Ford, Kerrie; Cardenas, Rosa; Supuran, Claudiu T; Cobden, Philip M; Rohling, Mala; Vaughan-Jones, Richard D

    2014-01-01

    Carbonic anhydrase enzymes (CAs) catalyse the reversible hydration of CO2 to H+ and HCO3− ions. This catalysis is proposed to be harnessed by acid/base transporters, to facilitate their transmembrane flux activity, either through direct protein–protein binding (a ‘transport metabolon’) or local functional interaction. Flux facilitation has previously been investigated by heterologous co-expression of relevant proteins in host cell lines/oocytes. Here, we examine the influence of intrinsic CA activity on membrane HCO3− or H+ transport via the native acid-extruding proteins, Na+–HCO3− cotransport (NBC) and Na+/H+ exchange (NHE), expressed in enzymically isolated mammalian ventricular myocytes. Effects of intracellular and extracellular (exofacial) CA (CAi and CAe) are distinguished using membrane-permeant and –impermeant pharmacological CA inhibitors, while measuring transporter activity in the intact cell using pH and Na+ fluorophores. We find that NBC, but not NHE flux is enhanced by catalytic CA activity, with facilitation being confined to CAi activity alone. Results are quantitatively consistent with a model where CAi catalyses local H+ ion delivery to the NBC protein, assisting the subsequent (uncatalysed) protonation and removal of imported HCO3− ions. In well-superfused myocytes, exofacial CA activity is superfluous, most likely because extracellular CO2/HCO3− buffer is clamped at equilibrium. The CAi insensitivity of NHE flux suggests that, in the native cell, intrinsic mobile buffer-shuttles supply sufficient intracellular H+ ions to this transporter, while intrinsic buffer access to NBC proteins is restricted. Our results demonstrate a selective CA facilitation of acid/base transporters in the ventricular myocyte, implying a specific role for the intracellular enzyme in HCO3− transport, and hence pHi regulation in the heart. PMID:24297849

  7. Facilitation by intracellular carbonic anhydrase of Na+ -HCO3- co-transport but not Na+ / H+ exchange activity in the mammalian ventricular myocyte.

    PubMed

    Villafuerte, Francisco C; Swietach, Pawel; Youm, Jae-Boum; Ford, Kerrie; Cardenas, Rosa; Supuran, Claudiu T; Cobden, Philip M; Rohling, Mala; Vaughan-Jones, Richard D

    2014-03-01

    Carbonic anhydrase enzymes (CAs) catalyse the reversible hydration of CO2 to H+ and HCO3- ions. This catalysis is proposed to be harnessed by acid/base transporters, to facilitate their transmembrane flux activity, either through direct protein-protein binding (a 'transport metabolon') or local functional interaction. Flux facilitation has previously been investigated by heterologous co-expression of relevant proteins in host cell lines/oocytes. Here, we examine the influence of intrinsic CA activity on membrane HCO3- or H+ transport via the native acid-extruding proteins, Na+ -HCO3- cotransport (NBC) and Na+ / H+ exchange (NHE), expressed in enzymically isolated mammalian ventricular myocytes. Effects of intracellular and extracellular (exofacial) CA (CAi and CAe) are distinguished using membrane-permeant and -impermeant pharmacological CA inhibitors, while measuring transporter activity in the intact cell using pH and Na+ fluorophores. We find that NBC, but not NHE flux is enhanced by catalytic CA activity, with facilitation being confined to CAi activity alone. Results are quantitatively consistent with a model where CAi catalyses local H+ ion delivery to the NBC protein, assisting the subsequent (uncatalysed) protonation and removal of imported HCO3- ions. In well-superfused myocytes, exofacial CA activity is superfluous, most likely because extracellular CO2/HCO3- buffer is clamped at equilibrium. The CAi insensitivity of NHE flux suggests that, in the native cell, intrinsic mobile buffer-shuttles supply sufficient intracellular H+ ions to this transporter, while intrinsic buffer access to NBC proteins is restricted. Our results demonstrate a selective CA facilitation of acid/base transporters in the ventricular myocyte, implying a specific role for the intracellular enzyme in HCO3- transport, and hence pHi regulation in the heart.

  8. Stimulation of Na{sup +}/K{sup +} ATPase activity and Na{sup +} coupled glucose transport by {beta}-catenin

    SciTech Connect

    Sopjani, Mentor; Alesutan, Ioana; Wilmes, Jan; Dermaku-Sopjani, Miribane; Lam, Rebecca S.; Jakupi, Muharrem; Foeller, Michael; Lang, Florian

    2010-11-19

    Research highlights: {yields} The oncogenic transcription factor {beta}-catenin stimulates the Na{sup +}/K{sup +}-ATPase. {yields} {beta}-Catenin stimulates SGLT1 dependent Na{sup +}, glucose cotransport. {yields} The effects are independent of transcription. {yields} {beta}-Catenin sensitive transport may contribute to properties of proliferating cells. -- Abstract: {beta}-Catenin is a multifunctional protein stimulating as oncogenic transcription factor several genes important for cell proliferation. {beta}-Catenin-regulated genes include the serum- and glucocorticoid-inducible kinase SGK1, which is known to stimulate a variety of transport systems. The present study explored the possibility that {beta}-catenin influences membrane transport. To this end, {beta}-catenin was expressed in Xenopus oocytes with or without SGLT1 and electrogenic transport determined by dual electrode voltage clamp. As a result, expression of {beta}-catenin significantly enhanced the ouabain-sensitive current of the endogeneous Na{sup +}/K{sup +}-ATPase. Inhibition of vesicle trafficking by brefeldin A revealed that the stimulatory effect of {beta}-catenin on the endogenous Na{sup +}/K{sup +}-ATPase was not due to enhanced stability of the pump protein in the cell membrane. Expression of {beta}-catenin further enhanced glucose-induced current (Ig) in SGLT1-expressing oocytes. In the absence of SGLT1 Ig was negligible irrespective of {beta}-catenin expression. The stimulating effect of {beta}-catenin on both Na{sup +}/K{sup +} ATPase and SGLT1 activity was observed even in the presence of actinomycin D, an inhibitor of transcription. The experiments disclose a completely novel function of {beta}-catenin, i.e. the regulation of transport.

  9. Activity of NA(+)/H(+) exchangers alters aquaporin-mediated water transport in human placenta.

    PubMed

    Dietrich, Valeria; Damiano, Alicia E

    2015-12-01

    The intracellular pH (pHi) of syncytiotrophoblasts is regulated, in part, by Na(+)/H(+) exchanger (NHE)-1, NHE-2, and NHE-3. Failures in pHi homeostasis could alter critical cellular functions such as water transport and cell volume. Here, we evaluated whether alterations in syncytiotrophoblast pHi could modify water uptake mediated by aquaporins (AQPs) and the contribution of NHEs to this mechanism. We showed that changes in syncytiotrophoblast pHi did not affect water uptake in the presence of functional NHEs. However, inhibition of NHEs alters transcellular water transport mediated by AQPs in acidosis. These results suggest an interaction between placental AQPs and NHEs in the regulation of water uptake during acidotic states.

  10. A segment of gamma ENaC mediates elastase activation of Na+ transport.

    PubMed

    Adebamiro, Adedotun; Cheng, Yi; Rao, U Subrahmanyeswara; Danahay, Henry; Bridges, Robert J

    2007-12-01

    The epithelial Na(+) channel (ENaC) that mediates regulated Na(+) reabsorption by epithelial cells in the kidney and lungs can be activated by endogenous proteases such as channel activating protease 1 and exogenous proteases such as trypsin and neutrophil elastase (NE). The mechanism by which exogenous proteases activate the channel is unknown. To test the hypothesis that residues on ENaC mediate protease-dependent channel activation wild-type and mutant ENaC were stably expressed in the FRT epithelial cell line using a tripromoter human ENaC construct, and protease-induced short-circuit current activation was measured in aprotinin-treated cells. The amiloride-sensitive short circuit current (I(Na)) was stimulated by aldosterone (1.5-fold) and dexamethasone (8-fold). Dexamethasone-treated cells were used for all subsequent studies. The serum protease inhibitor aprotinin decreased baseline I(Na) by approximately 50% and I(Na) could be restored to baseline control values by the exogenous addition of trypsin, NE, and porcine pancreatic elastase (PE) but not by thrombin. All protease experiments were thus performed after exposure to aprotinin. Because NE recognition of substrates occurs with a preference for binding valines at the active site, several valines in the extracellular loops of alpha and gamma ENaC were sequentially substituted with glycines. This scan yielded two valine residues in gamma ENaC at positions 182 and 193 that resulted in inhibited responses to NE when simultaneously changed to other amino acids. The mutations resulted in decreased rates of activation and decreased activated steady-state current levels. There was an approximately 20-fold difference in activation efficiency of NE against wild-type ENaC compared to a mutant with glycine substitutions at positions 182 and 193. However, the mutants remain susceptible to activation by trypsin and the related elastase, PE. Alanine is the preferred P(1) position residue for PE and substitution of

  11. Nutrient transport in the small intestine: Na+,K+-ATPase expression and activity in the small intestine of the chicken as influenced by dietary sodium.

    PubMed

    Gal-Garber, O; Mabjeesh, S J; Sklan, D; Uni, Z

    2003-07-01

    The Na+-K+-ATPase, localized in the basolateral membrane of enterocytes plays a major role in nutrient transport in the small intestine by transferring K+ ions into and Na+ out of the cell. Within the enterocyte, homeostasis is maintained by active exclusion of Na from the cell by the Na+,K+-adenosine triphosphatase (ATPase) or sodium pump. Because much of the intestinal nutrient transport is by Na cotransporters, Na+,K+-ATPase may be used to evaluate nutrient uptake. In this study, nutrient transport was evaluated by determining expression and activity of Na+-K+-ATPase in the jejunum of chicks fed diets with different concentrations of Na. Expression of the chicken Na+-K+-ATPase gene was examined following isolation of an 1,140 bp cDNA fragment of the alpha-subunit using a reverse transcription (RT)-PCR reaction with specific primers. This fragment was sequenced and showed 95 to 98% homology with the mammalian alpha-subunit of the Na+-K+-ATPase genes. This cDNA fragment was used as a specific probe in Northern blot hybridization for determination of expression in the chicken jejunum. Expression of mRNA of Na+-K+-ATPase was enhanced at low dietary Na but was unchanged at high dietary Na concentrations. In contrast, activity of the enzyme was low with low dietary Na and unchanged at high dietary Na. The Vmax of the Na+-K+-ATPase was unchanged, but affinity was altered by dietary Na concentrations. Thus, determination of expression and activity of intestinal Na+-K+-ATPase allows clearer understanding of changes in intestinal uptake due to dietary Na.

  12. Na+ recirculation and isosmotic transport.

    PubMed

    Larsen, E H; Møbjerg, N

    2006-01-01

    The Na(+) recirculation theory for solute-coupled fluid absorption is an expansion of the local osmosis concept introduced by Curran and analyzed by Diamond & Bossert. Based on studies on small intestine the theory assumes that the observed recirculation of Na(+) serves regulation of the osmolarity of the absorbate. Mathematical modeling reproducing bioelectric and hydrosmotic properties of small intestine and proximal tubule, respectively, predicts a significant range of observations such as isosmotic transport, hyposmotic transport, solvent drag, anomalous solvent drag, the residual hydraulic permeability in proximal tubule of AQP1 (-/-) mice, and the inverse relationship between hydraulic permeability and the concentration difference needed to reverse transepithelial water flow. The model reproduces the volume responses of cells and lateral intercellular space (lis) following replacement of luminal NaCl by sucrose as well as the linear dependence of volume absorption on luminal NaCl concentration. Analysis of solvent drag on Na(+) in tight junctions provides explanation for the surprisingly high metabolic efficiency of Na(+) reabsorption. The model predicts and explains low metabolic efficiency in diluted external baths. Hyperosmolarity of lis is governed by the hydraulic permeability of the apical plasma membrane and tight junction with 6-7 mOsm in small intestine and < or = 1 mOsm in proximal tubule. Truly isosmotic transport demands a Na(+) recirculation of 50-70% in small intestine but might be barely measurable in proximal tubule. The model fails to reproduce a certain type of observations: The reduced volume absorption at transepithelial osmotic equilibrium in AQP1 knockout mice, and the stimulated water absorption by gallbladder in diluted external solutions. Thus, it indicates cellular regulation of apical Na(+) uptake, which is not included in the mathematical treatment. PMID:17206513

  13. Na+ recirculation and isosmotic transport.

    PubMed

    Larsen, E H; Møbjerg, N

    2006-01-01

    The Na(+) recirculation theory for solute-coupled fluid absorption is an expansion of the local osmosis concept introduced by Curran and analyzed by Diamond & Bossert. Based on studies on small intestine the theory assumes that the observed recirculation of Na(+) serves regulation of the osmolarity of the absorbate. Mathematical modeling reproducing bioelectric and hydrosmotic properties of small intestine and proximal tubule, respectively, predicts a significant range of observations such as isosmotic transport, hyposmotic transport, solvent drag, anomalous solvent drag, the residual hydraulic permeability in proximal tubule of AQP1 (-/-) mice, and the inverse relationship between hydraulic permeability and the concentration difference needed to reverse transepithelial water flow. The model reproduces the volume responses of cells and lateral intercellular space (lis) following replacement of luminal NaCl by sucrose as well as the linear dependence of volume absorption on luminal NaCl concentration. Analysis of solvent drag on Na(+) in tight junctions provides explanation for the surprisingly high metabolic efficiency of Na(+) reabsorption. The model predicts and explains low metabolic efficiency in diluted external baths. Hyperosmolarity of lis is governed by the hydraulic permeability of the apical plasma membrane and tight junction with 6-7 mOsm in small intestine and < or = 1 mOsm in proximal tubule. Truly isosmotic transport demands a Na(+) recirculation of 50-70% in small intestine but might be barely measurable in proximal tubule. The model fails to reproduce a certain type of observations: The reduced volume absorption at transepithelial osmotic equilibrium in AQP1 knockout mice, and the stimulated water absorption by gallbladder in diluted external solutions. Thus, it indicates cellular regulation of apical Na(+) uptake, which is not included in the mathematical treatment.

  14. Role of N-linked oligosaccharides in the transport activity of the Na+/H+ antiporter in rat renal brush-border membrane

    SciTech Connect

    Yusufi, A.N.; Szczepanska-Konkel, M.; Dousa, T.P.

    1988-09-25

    The role of N-linked oligosaccharide side chains in the biogenesis and function of Na+-coupled transporters in renal luminal brush-border membrane (BBM) is not known. We examined the question of how in vivo inhibition by alkaloid swainsonine of alpha-mannosidase, a key enzyme in processing of glycoproteins in the Golgi apparatus, affects Na+/H+ antiport and Na+/Pi symport as well as activities of other transporters and enzymes in rat renal BBM. Administration of swainsonine to thyroparathyroidectomized rats, control or treated with 3,5,3'-triiodothyronine, markedly decreased the rate of Na+/H+ antiport, but had no effect on the rate of Na+/Pi symport across renal BBM vesicles (BBMV). Moreover, administration of swainsonine did not change activities of Na+ gradient, ((extravesicular Na+) greater than (intravesicular Na+))-dependent transport of D-glucose, L-proline, or the amiloride-insensitive 22Na+ uptake by BBMV; the activities of the BBM enzymes alkaline phosphatase, gamma-glutamyltransferase, or leucine aminopeptidase in BBMV were also not changed. The in vitro enzymatic deglycosylation of BBM by incubating freshly isolated BBMV with bacterial endoglycosidase F also resulted in a decreased rate of Na+/H+ antiport, but not Na+-coupled symports of Pi, L-proline, and D-glucose, or the activities of the BBM enzymes were not significantly affected. Similar incubation with endoglycosidase H was without effect on any of these parameters. Both the modification of BBMV glycoproteins by administration fo swainsonine in vivo as well as the in vitro incubation of BBMV with endoglycosidase F resulted in a decrease of the apparent Vmax of Na+/H+ antiport, but did not change the apparent Km of this antiporter for extravesicular Na+ and did not increase H+ conductance of BBM.

  15. In vivo stimulation of AMP-activated protein kinase enhanced tubuloglomerular feedback but reduced tubular sodium transport during high dietary NaCl intake.

    PubMed

    Huang, Dan Yang; Gao, Huanhuan; Boini, Krishna M; Osswald, Hartmut; Nürnberg, Bernd; Lang, Florian

    2010-06-01

    AMP-activated protein kinase (AMPK) is expressed in the apical membrane of cortical thick ascending limb, distal, and collecting tubules as well as macula densa cells of the kidneys. AMPK is an active modulator of epithelial Na(+) channels, Na(+)-2Cl(-)-K(+) cotransporter, and the ATP-dependent potassium channel. The present experiments explored whether AMPK participates in the regulation of tubuloglomerular feedback (TGF) and renal tubular sodium handling. To this end, renal clearance and micropuncture experiments were performed in anesthetized rats. Under normal NaCl diet, neither TGF response nor renal fluid and sodium excretion were altered by pharmacological activation of AMPK in vivo. However, under high NaCl diet, the TGF response was significantly enhanced after intravenous or intratubular application of the AMPK activator AICAR. Moreover, AICAR application significantly increased fractional delivery of fluid and sodium to the end of the proximal tubule. High dietary NaCl intake increased the renal transcript levels encoding the AMPK-alpha1 subunit, while it decreased the expression of AMPK-beta1 and AMPK-gamma2 subunits. Immunoblots revealed that high dietary NaCl intake reduced renal expression of activated AMPK by about three times compared to normal NaCl diet whereas additional AICAR application increased AMPK activity. Our results suggest that AMPK regulates tubuloglomerular balance as well as tubular transport upon change of renal work load.

  16. Gasotransmitters: novel regulators of epithelial na(+) transport?

    PubMed

    Althaus, Mike

    2012-01-01

    The vectorial transport of Na(+) across epithelia is crucial for the maintenance of Na(+) and water homeostasis in organs such as the kidneys, lung, or intestine. Dysregulated Na(+) transport processes are associated with various human diseases such as hypertension, the salt-wasting syndrome pseudohypoaldosteronism type 1, pulmonary edema, cystic fibrosis, or intestinal disorders, which indicate that a precise regulation of epithelial Na(+) transport is essential. Novel regulatory signaling molecules are gasotransmitters. There are currently three known gasotransmitters: nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H(2)S). These molecules are endogenously produced in mammalian cells by specific enzymes and have been shown to regulate various physiological processes. There is a growing body of evidence which indicates that gasotransmitters may also regulate Na(+) transport across epithelia. This review will summarize the available data concerning NO, CO, and H(2)S dependent regulation of epithelial Na(+) transport processes and will discuss whether or not these mediators can be considered as true physiological regulators of epithelial Na(+) transport biology.

  17. Pyrophosphate-fueled Na+ and H+ transport in prokaryotes.

    PubMed

    Baykov, Alexander A; Malinen, Anssi M; Luoto, Heidi H; Lahti, Reijo

    2013-06-01

    In its early history, life appeared to depend on pyrophosphate rather than ATP as the source of energy. Ancient membrane pyrophosphatases that couple pyrophosphate hydrolysis to active H(+) transport across biological membranes (H(+)-pyrophosphatases) have long been known in prokaryotes, plants, and protists. Recent studies have identified two evolutionarily related and widespread prokaryotic relics that can pump Na(+) (Na(+)-pyrophosphatase) or both Na(+) and H(+) (Na(+),H(+)-pyrophosphatase). Both these transporters require Na(+) for pyrophosphate hydrolysis and are further activated by K(+). The determination of the three-dimensional structures of H(+)- and Na(+)-pyrophosphatases has been another recent breakthrough in the studies of these cation pumps. Structural and functional studies have highlighted the major determinants of the cation specificities of membrane pyrophosphatases and their potential use in constructing transgenic stress-resistant organisms.

  18. A single mutation converts bacterial Na(+) -transporting rhodopsin into an H(+) transporter.

    PubMed

    Mamedov, Mahir D; Mamedov, Adalyat M; Bertsova, Yulia V; Bogachev, Alexander V

    2016-09-01

    Na(+) -rhodopsins are light-driven pumps used by marine bacteria to extrude Na(+) ions from the cytoplasm. We show here that replacement of Gln123 on the cytoplasmic side of the ion-conductance channel with aspartate or glutamate confers H(+) transport activity to the Na(+) -rhodopsin from Dokdonia sp. PRO95. The Q123E variant could transport H(+) out of Escherichia coli cells in a medium containing 100 mm Na(+) and SCN(-) as the penetrating anion. The rates of the photocycle steps of this variant were only marginally dependent on Na(+) , and the major electrogenic steps were the decays of the K and O intermediates. PMID:27447358

  19. Characteristics and pharmacological regulation of epithelial Na+ channel (ENaC) and epithelial Na+ transport.

    PubMed

    Marunaka, Yoshinori

    2014-01-01

    Epithelial Na(+) transport participates in control of various body functions and conditions: e.g., homeostasis of body fluid content influencing blood pressure, control of amounts of fluids covering the apical surface of alveolar epithelial cells at appropriate levels for normal gas exchange, and prevention of bacterial/viral infection. Epithelial Na(+) transport via the transcellular pathway is mediated by the entry step of Na(+) across the apical membrane via Epithelial Na(+) Channel (ENaC) located at the apical membrane, and the extrusion step of Na(+) across the basolateral membrane via the Na(+),K(+)-ATPase located at the basolateral membrane. The rate-limiting step of the epithelial Na(+) transport via the transcellular pathway is generally recognized to be the entry step of Na(+) across the apical membrane via ENaC. Thus, up-/down-regulation of ENaC essentially participates in regulatory systems of blood pressure and normal gas exchange. Amount of ENaC-mediated Na(+) transport is determined by the number of ENaCs located at the apical membrane, activity (open probability) of individual ENaC located at the apical membrane, single channel conductance of ENaC located at the apical membrane, and driving force for the Na(+) entry via ENaCs across the apical membrane. In the present review article, I discuss the characteristics of ENaC and how these factors are regulated.

  20. Membrane Na+-pyrophosphatases can transport protons at low sodium concentrations.

    PubMed

    Luoto, Heidi H; Nordbo, Erika; Baykov, Alexander A; Lahti, Reijo; Malinen, Anssi M

    2013-12-01

    Membrane-bound Na(+)-pyrophosphatase (Na(+)-PPase), working in parallel with the corresponding ATP-energized pumps, catalyzes active Na(+) transport in bacteria and archaea. Each ~75-kDa subunit of homodimeric Na(+)-PPase forms an unusual funnel-like structure with a catalytic site in the cytoplasmic part and a hydrophilic gated channel in the membrane. Here, we show that at subphysiological Na(+) concentrations (<5 mM), the Na(+)-PPases of Chlorobium limicola, four other bacteria, and one archaeon additionally exhibit an H(+)-pumping activity in inverted membrane vesicles prepared from recombinant Escherichia coli strains. H(+) accumulation in vesicles was measured with fluorescent pH indicators. At pH 6.2-8.2, H(+) transport activity was high at 0.1 mM Na(+) but decreased progressively with increasing Na(+) concentrations until virtually disappearing at 5 mM Na(+). In contrast, (22)Na(+) transport activity changed little over a Na(+) concentration range of 0.05-10 mM. Conservative substitutions of gate Glu(242) and nearby Ser(243) and Asn(677) residues reduced the catalytic and transport functions of the enzyme but did not affect the Na(+) dependence of H(+) transport, whereas a Lys(681) substitution abolished H(+) (but not Na(+)) transport. All four substitutions markedly decreased PPase affinity for the activating Na(+) ion. These results are interpreted in terms of a model that assumes the presence of two Na(+)-binding sites in the channel: one associated with the gate and controlling all enzyme activities and the other located at a distance and controlling only H(+) transport activity. The inherent H(+) transport activity of Na(+)-PPase provides a rationale for its easy evolution toward specific H(+) transport.

  1. Na+-independent phosphate transport in Caco2BBE cells

    PubMed Central

    Candeal, Eduardo; Caldas, Yupanqui A.; Guillén, Natalia; Levi, Moshe

    2014-01-01

    Pi transport in epithelia has both Na+-dependent and Na+-independent components, but so far only Na+-dependent transporters have been characterized in detail and molecularly identified. Consequently, in the present study, we initiated the characterization and analysis of intestinal Na+-independent Pi transport using an in vitro model, Caco2BBE cells. Only Na+-independent Pi uptake was observed in these cells, and Pi uptake was dramatically increased when cells were incubated in high-Pi DMEM (4 mM) from 1 day to several days. No response to low-Pi medium was observed. The increased Pi transport was mainly caused by Vmax changes, and it was prevented by actinomycin D and cycloheximide. Pi transport in cells grown in 1 mM Pi (basal DMEM) decreased at pH > 7.5, and it was inhibited with proton ionophores. Pi transport in cells incubated with 4 mM Pi increased with alkaline pH, suggesting a preference for divalent phosphate. Pi uptake in cells in 1 mM Pi was completely inhibited only by Pi and partially inhibited by phosphonoformate, oxalate, DIDS, SITS, SO42−, HCO3−, and arsenate. This inhibition pattern suggests that more than one Pi transporter is active in cells maintained with 1 mM Pi. Phosphate transport from cells maintained at 4 mM Pi was only partially inhibited by phosphonoformate, oxalate, and arsenate. Attempts to identify the responsible transporters showed that multifunctional anion exchangers of the Slc26 family as well as members of Slc17, Slc20, and Slc37 and the Pi exporter xenotropic and polytropic retrovirus receptor 1 are not involved. PMID:25298422

  2. Na+-independent phosphate transport in Caco2BBE cells.

    PubMed

    Candeal, Eduardo; Caldas, Yupanqui A; Guillén, Natalia; Levi, Moshe; Sorribas, Víctor

    2014-12-15

    Pi transport in epithelia has both Na(+)-dependent and Na(+)-independent components, but so far only Na(+)-dependent transporters have been characterized in detail and molecularly identified. Consequently, in the present study, we initiated the characterization and analysis of intestinal Na(+)-independent Pi transport using an in vitro model, Caco2BBE cells. Only Na(+)-independent Pi uptake was observed in these cells, and Pi uptake was dramatically increased when cells were incubated in high-Pi DMEM (4 mM) from 1 day to several days. No response to low-Pi medium was observed. The increased Pi transport was mainly caused by Vmax changes, and it was prevented by actinomycin D and cycloheximide. Pi transport in cells grown in 1 mM Pi (basal DMEM) decreased at pH > 7.5, and it was inhibited with proton ionophores. Pi transport in cells incubated with 4 mM Pi increased with alkaline pH, suggesting a preference for divalent phosphate. Pi uptake in cells in 1 mM Pi was completely inhibited only by Pi and partially inhibited by phosphonoformate, oxalate, DIDS, SITS, SO4 (2-), HCO3 (-), and arsenate. This inhibition pattern suggests that more than one Pi transporter is active in cells maintained with 1 mM Pi. Phosphate transport from cells maintained at 4 mM Pi was only partially inhibited by phosphonoformate, oxalate, and arsenate. Attempts to identify the responsible transporters showed that multifunctional anion exchangers of the Slc26 family as well as members of Slc17, Slc20, and Slc37 and the Pi exporter xenotropic and polytropic retrovirus receptor 1 are not involved.

  3. [Na+/H+- and Na+/Na+-countertransport in human, rabbit, and rat erythrocytes: evidence for the existence of two independent ion-transporting systems].

    PubMed

    Orlov, S N; Kuznetsov, S R; Kolosova, I A; Makarov, V L

    1994-05-01

    The activity and regulatory features of the Na+/H(+)- and Na+/Na(+)-exchange were studied in human, rabbit and rat red blood cells. No basal activity of the Na+/H(+)-exchange (the amyloride-inhibited component of the 22Na+ influx) in erythrocytes of these species was observed. The rate of 22Na+ influx increased rapidly when the experiments were carried out on acid-loaded cells in an alkaline (pH0 = 8.0) incubation medium (delta mu H(+)-induced Na+/H(+)-exchange). The ratio of delta mu H(+)-induced Na+/H(+)-exchange activities in human, rabbit and rat red blood cells was 1.0 : 1.1 : 2.3, respectively, whereas that of the Na+/Na(+)-exchange activities (the phloretin-inhibited component of the 22Na+ influx) in erythrocytes of these species was 1.0 : 4.6 : 0.2. The osmotic shrinkage of rat and rabbit erythrocytes led to the stimulation of the Na+/H(+)- (but not Na+/Na+) exchange. Amyloride (1 mM) inhibited the shrinkage-induced 22Na+ entry as well as the delta mu H(+)-induced 22Na+ entry--by 95 and 10-20%, respectively. Heat treatment (10 min, 49-51 degrees C), disturbing the membrane cytoskeleton suppressed both the shrinkage-induced activation and the delta mu H(+)-induced activation of the Na+/H(+)-exchange. The data obtained indicate that the both transport systems are mediated by two distinct transport carriers. It may be suggested that the delta mu H(+)-induced Na+/H(+)-exchange, on the one hand, and the shrinkage-induced Na+/H(+)-exchange, on the other, are mediated by two different Na+/H(+)-exchanger subtypes. PMID:8043690

  4. Na+ transport by rabbit urinary bladder, a tight epithelium.

    PubMed

    Lewis, S A; Diamond, J M

    1976-08-27

    By in vitro experiments on rabbit bladder, we reassessed the traditional view that mammalian urinary bladder lacks ion transport mechanisms. Since the ratio of actual-to-nominal membrane area in folded epithelia is variable and hard to estimate, we normalized membrane properties to apical membrane capacitance rather than to nominal area (probably 1 muF approximately 1 cm2 actual area). A new mounting technique that virtually eliminates edge damage yielded resistances up to 78,000 omega muF for rabbit bladder, and resistances for amphibian skin and bladder much higher than those usually reported. This technique made it possible to observe a transport-related conductance pathway, and a close correlation between transepithelial conductance (G) and short-circuit current (Isc) in these tight epithelia. G and Isc were increased by mucosal (Na+) [Isc approximately 0 when (Na+) approximately 0], aldosterone, serosal (HCO-3) and high mucosal (H+); were decreased by amiloride, mucosal (Ca++), ouabain, metabolic inhibitors and serosal (H+); and were unaffected by (Cl-) and little affected by antidiuretic hormone (ADH). Physiological variation in the rabbits' dietary Na+ intake caused variations in bladder G and Isc similar to those caused by the expected in vivo changes in aldosterone levels. The relation between G and Isc was the same whether defined by diet changes, natural variation among individual rabbits, or most of the above agents. A method was developed for separately resolving conductances of junctions, basolateral cell membrane, and apical cell membrane from this G--Isc relation. Net Na+ flux equalled Isc. Net Cl- flux was zero on short circuit and equalled only 25% of net Na+ flux in open circuit. Bladder membrane fragments contained a Na+-K+-activated, ouabain-inhibited ATPase. The physiological significance of Na+ absorption against steep gradients in rabbit bladder may be to maintain kidney-generated ion gradients during bladder storage of urine, especially

  5. Evidence for NHE3-mediated Na transport in sheep and bovine forestomach.

    PubMed

    Rabbani, Imtiaz; Siegling-Vlitakis, Christiane; Noci, Bardhyl; Martens, Holger

    2011-08-01

    Na absorption across the cornified, multilayered, and squamous rumen epithelium is mediated by electrogenic amiloride-insensitive transport and by electroneutral Na transport. High concentrations of amiloride (>100 μM) inhibit Na transport, indicating Na(+)/H(+) exchange (NHE) activity. The underlying NHE isoform for transepithelial Na absorption was characterized by mucosal application of the specific inhibitor HOE642 for NHE1 and S3226 for NHE3 in Ussing chamber studies with isolated epithelia from bovine and sheep forestomach. S3226 (1 μM; NHE3 inhibitor) abolished electroneutral Na transport under control conditions and also the short-chain fatty acid-induced increase of Na transport via NHE. However, HOE642 (30 μM; NHE1 inhibitor) did not change Na transport rates. NHE3 was immunohistochemically localized in membranes of the upper layers toward the lumen. Expression of NHE1 and NHE3 has been previously demonstrated by RT-PCR, and earlier experiments with isolated rumen epithelial cells have shown the activity of both NHE1 and NHE3. Obviously, both isoforms are involved in the regulation of intracellular pH, pH(i). However, transepithelial Na transport is only mediated by apical uptake via NHE3 in connection with extrusion of Na by the basolaterally located Na-K-ATPase. The missing involvement of NHE1 in transepithelial Na transport suggests that the proposed "job sharing" in epithelia between these two isoforms probably also applies to forestomach epithelia: NHE3 for transepithelial transport and NHE1 for, among others, pH(i) and volume regulation. PMID:21613579

  6. EPAct Transportation Regulatory Activities

    SciTech Connect

    2011-11-21

    The U.S. Department of Energy's (DOE) Vehicle Technologies Program manages several transportation regulatory activities established by the Energy Policy Act of 1992 (EPAct), as amended by the Energy Conservation Reauthorization Act of 1998, EPAct 2005, and the Energy Independence and Security Act of 2007 (EISA).

  7. Effects of insulin and epinephrine on Na/sup +/-K/sup +/ and glucose transport in soleus muscle

    SciTech Connect

    Clausen, T.; Flatman, J.A.

    1987-04-01

    To identify possible cause-effect relationships between changes in active Na/sup +/-K/sup +/ transport, resting membrane potential, and glucose transport, the effects of insulin and epinephrine were compared in rat soleus muscle. Epinephrine, which produced twice as large a hyperpolarization as insulin, induced only a modest increase in /sup 14/C-labeled sugar transport. Ouabain, at a concentration (10/sup -3/ M) sufficient to block active Na/sup +/-K/sup +/ transport and the hyperpolarization induced by the two hormones, did not interfere with sugar transport stimulation. After Na/sup +/ loading in K/sup +/-free buffer, the return to K/sup +/-containing standard buffer caused marked stimulation of active /sup 22/Na/sup +/-/sup 42/K/sup +/ transport, twice the hyperpolarization produced by insulin but no change in sugar transport. The insulin-induced activation of the /sup 22/Na/sup +/-/sup 42/K/sup +/ pump leads to decreased intracellular /sup 22/Na/sup +/ concentration and hyperpolarization, but none of these events can account for the concomitant activation of the glucose transport system. The stimulating effect of insulin on active Na/sup +/-K/sup +/ transport was not suppressed by amiloride, indicating that in intact skeletal muscle it is not elicited by a primary increase in Na/sup +/ influx via the Na/sup +//H/sup +/-exchange system.

  8. Na+ Transport in Cardiac Myocytes; Implications for Excitation-Contraction Coupling

    PubMed Central

    Bers, Donald M.; Despa, Sanda

    2009-01-01

    Intracellular Na+ concentration ([Na+]i) is very important in modulating the contractile and electrical activity of the heart. Upon electrical excitation of the myocardium, voltage-dependent Na+ channels open, triggering the upstroke of the action potential (AP). During the AP, Ca2+ enters the myocytes via L-type Ca2+ channels. This triggers Ca2+ release from the sarcoplasmic reticulum (SR) and thus activates contraction. Relaxation occurs when cytosolic Ca2+ declines, mainly due to re-uptake into the SR via SR Ca2+-ATPase and extrusion from the cell via the Na+/Ca2+ exchanger (NCX). NCX extrudes one Ca2+ ion in exchange for three Na+ ions and its activity is critically regulated by [Na+]i. Thus, via NCX, [Na+]i is centrally involved in the regulation of intracellular [Ca2+] and contractility. Na+ brought in by Na+ channels, NCX and other Na+ entry pathways is extruded by the Na+/K+ pump (NKA) to keep [Na+]i low. NKA is regulated by phospholemman, a small sarcolemmal protein that associates with NKA. Unphosphorylated phospholemman inhibits NKA by decreasing the pump affinity for internal Na+ and this inhibition is relieved upon phosphorylation. Here we discuss the main characteristics of the Na+ transport pathways in cardiac myocytes and their physiological and pathophysiological relevance. PMID:19243007

  9. Expression of apical Na(+)-L-glutamine co-transport activity, B(0)-system neutral amino acid co-transporter (B(0)AT1) and angiotensin-converting enzyme 2 along the jejunal crypt-villus axis in young pigs fed a liquid formula

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Gut apical amino acid (AA) transport activity is high at birth and during suckling, thus being essential to maintain luminal nutrient-dependent mucosal growth through providing AA as essential metabolic fuel, substrates and nutrient stimuli for cellular growth. Because system-B(0) Na(+)-neutral AA c...

  10. Regulators of Slc4 bicarbonate transporter activity

    PubMed Central

    Thornell, Ian M.; Bevensee, Mark O.

    2015-01-01

    The Slc4 family of transporters is comprised of anion exchangers (AE1-4), Na+-coupled bicarbonate transporters (NCBTs) including electrogenic Na/bicarbonate cotransporters (NBCe1 and NBCe2), electroneutral Na/bicarbonate cotransporters (NBCn1 and NBCn2), and the electroneutral Na-driven Cl-bicarbonate exchanger (NDCBE), as well as a borate transporter (BTR1). These transporters regulate intracellular pH (pHi) and contribute to steady-state pHi, but are also involved in other physiological processes including CO2 carriage by red blood cells and solute secretion/reabsorption across epithelia. Acid-base transporters function as either acid extruders or acid loaders, with the Slc4 proteins moving HCO−3 either into or out of cells. According to results from both molecular and functional studies, multiple Slc4 proteins and/or associated splice variants with similar expected effects on pHi are often found in the same tissue or cell. Such apparent redundancy is likely to be physiologically important. In addition to regulating pHi, a HCO−3 transporter contributes to a cell's ability to fine tune the intracellular regulation of the cotransported/exchanged ion(s) (e.g., Na+ or Cl−). In addition, functionally similar transporters or splice variants with different regulatory profiles will optimize pH physiology and solute transport under various conditions or within subcellular domains. Such optimization will depend on activated signaling pathways and transporter expression profiles. In this review, we will summarize and discuss both well-known and more recently identified regulators of the Slc4 proteins. Some of these regulators include traditional second messengers, lipids, binding proteins, autoregulatory domains, and less conventional regulators. The material presented will provide insight into the diversity and physiological significance of multiple members within the Slc4 gene family. PMID:26124722

  11. Molecular events involved in up-regulating human Na+-independent neutral amino acid transporter LAT1 during T-cell activation.

    PubMed

    Nii, T; Segawa, H; Taketani, Y; Tani, Y; Ohkido, M; Kishida, S; Ito, M; Endou, H; Kanai, Y; Takeda, E; Miyamoto Ki

    2001-09-15

    We investigated the regulation of system-L amino acid transporter (LAT1) during T-cell activation. In quiescent T-cells, L-leucine transport is mediated mainly by the system-L amino acid transport system and is increased significantly during T-cell activation by PMA and ionomycin. In quiescent T-cells, the LAT1 protein was heterocomplexed with 4F2 heavy chain (4F2hc) in the plasma membrane. During T-cell activation, the amounts of 4F2hc and LAT1 heterocomplex were significantly elevated compared with those in quiescent T-cells. In addition, by Northern-blot analysis, these increments were found to be due to elevated levels of LAT1 and 4F2hc mRNA. Transient expression of constructs comprising various LAT1 gene promoter fragments, which contained all three of the GC boxes, was sufficient for promoting luciferase expression in Jurkat T-cells, but the promoter of the LAT1 gene did not respond to PMA and ionomycin. Similar observations were observed in the human 4F2hc gene promoter. In nuclear run-on assay, the LAT1 and 4F2hc genes were actively transcribed even in quiescent T-cells, but the low levels of both transcripts were shown to be the result of a block to transcription elongation within the exon 1 intron 1 regions. These findings indicated that a removal of the block to mRNA elongation stimulates the induction of system-L amino acid transporter gene transcripts (LAT1 and 4F2hc) in activated T-cells. PMID:11535130

  12. The gasotransmitter hydrogen sulphide decreases Na+ transport across pulmonary epithelial cells

    PubMed Central

    Althaus, M; Urness, KD; Clauss, WG; Baines, DL; Fronius, M

    2012-01-01

    BACKGROUND AND PURPOSE The transepithelial absorption of Na+ in the lungs is crucial for the maintenance of the volume and composition of epithelial lining fluid. The regulation of Na+ transport is essential, because hypo- or hyperabsorption of Na+ is associated with lung diseases such as pulmonary oedema or cystic fibrosis. This study investigated the effects of the gaseous signalling molecule hydrogen sulphide (H2S) on Na+ absorption across pulmonary epithelial cells. EXPERIMENTAL APPROACH Ion transport processes were electrophysiologically assessed in Ussing chambers on H441 cells grown on permeable supports at air/liquid interface and on native tracheal preparations of pigs and mice. The effects of H2S were further investigated on Na+ channels expressed in Xenopus oocytes and Na+/K+-ATPase activity in vitro. Membrane abundance of Na+/K+-ATPase was determined by surface biotinylation and Western blot. Cellular ATP concentrations were measured colorimetrically, and cytosolic Ca2+ concentrations were measured with Fura-2. KEY RESULTS H2S rapidly and reversibly inhibited Na+ transport in all the models employed. H2S had no effect on Na+ channels, whereas it decreased Na+/K+-ATPase currents. H2S did not affect the membrane abundance of Na+/K+-ATPase, its metabolic or calcium-dependent regulation, or its direct activity. However, H2S inhibited basolateral calcium-dependent K+ channels, which consequently decreased Na+ absorption by H441 monolayers. CONCLUSIONS AND IMPLICATIONS H2S impairs pulmonary transepithelial Na+ absorption, mainly by inhibiting basolateral Ca2+-dependent K+ channels. These data suggest that the H2S signalling system might represent a novel pharmacological target for modifying pulmonary transepithelial Na+ transport. PMID:22352810

  13. Cation transport mechanisms in Mycoplasma mycoides var. Capri cells. The nature of the link between K+ and Na+ transport

    PubMed Central

    Benyoucef, Mohammed; Rigaud, Jean-Louis; Leblanc, Gérard

    1982-01-01

    We have studied the links between the mechanisms of Na+, K+ and H+ movements in glycolysing Mycoplasma mycoides var. Capri cells. In the light of the results reported in the preceding paper [Benyoucef, Rigaud & Leblanc (1982) Biochem. J. 208, 529–538], we investigated certain properties of the membrane-bound ATPase of Mycoplasma cells, with special reference to its ionic requirements and sensitivity to specific inhibitors. Our findings show, first, that, although Na+ stimulated ATPase activity, K+ did not affect it, and, secondly, that NN′-dicyclocarboidi-imide and 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole (NBD) were potent inhibitors of the basal ATPase activity, which was unaffected by vanadate and ouabain. We also investigated the movements of Na+ and H+ under the experimental conditions applied to the study of the K+ uptake reported in the preceding paper, and found that when `Na+-loaded cells' previously equilibrated with 22Na+ were diluted in a sodium-free medium, addition of glucose induced a rapid efflux of 22Na+. This energy-dependent efflux was independent of the presence of KCl in the medium. Studies of the changes in internal pH by 9-aminoacridine fluorescence or [14C]methylamine distribution indicated that the movement of Na+ was coupled to that of protons moving in the opposite direction, a finding that supports the presence of an Na+/H+ antiport. When Na+-loaded cells are diluted in an Na+-rich medium the Na+/H+ antiport is still active, but cannot decrease the intracellular Na+ concentration. Under such conditions, net 22Na+ extrusion is specifically dependent on the presence of K+ in the medium. The present results and those derived from the study of K+ accumulation (the preceding paper) can be rationalized by assuming that Mycoplasma mycoides var. Capri cells contain two transport systems for Na+ extrusion: an Na+/H+ antiport and an ATP-consuming Na+/K+-exchange system. PMID:6219666

  14. Na+-dependent and Na+-independent betaine transport across the apical membrane of rat renal epithelium.

    PubMed

    Cano, Mercedes; Calonge, María L; Ilundáin, Anunciación A

    2015-10-01

    The low renal excretion of betaine indicates that the kidney efficiently reabsorbs the betaine filtered by the glomeruli but the mechanisms involved in such a process have been scarcely investigated. We have detected concentrative and non-concentrative betaine transport activity in brush-border membrane vesicles (BBMV) from rat renal cortex and medulla. The concentrative system is the Sodium/Imino-acid Transporter 1 (SIT1) because it is Na+- and Cl--dependent, electrogenic and is inhibited by an anti-SIT1 antibody. Its apparent affinity constant for betaine, Kt, is 1.1±0.5 mM and its maximal transport velocity, Vmax, 0.5±0.1 nmol betaine/mg protein/s. Inhibitors of the Na+/Cl-/betaine uptake are L-proline (75%) and cold betaine, L-carnitine and choline (40-60%). Neither creatine, TEA, taurine, β-alanine, GABA nor glycine significantly inhibited Na+/Cl-/betaine uptake. The non-concentrative betaine transport system is Na+- and H+-independent, electroneutral, with a Kt for betaine of 47±7 μM and a Vmax of 7.8±1 pmol betaine/mg protein/s. Its transport activity is nearly abolished by betaine, followed by L-carnitine (70-80%) and proline (40-50%), but a difference from the Na+/Cl-/betaine transport is that it is inhibited by TEA (approx. 50%) and unaffected by choline. The underlying carrier functions as an antiporter linking betaine entry into the BBMV with the efflux of either L-carnitine or betaine, an exchange unaffected by the anti-SIT1 antibody. As far as we know this is the first work reporting that betaine crosses the apical membrane of rat renal epithelium by SIT1 and by a Na+- and H+-independent transport system.

  15. The role of Ca(2+) and Na (+) membrane transport in brook trout (Salvelinus fontinalis) spermatozoa motility.

    PubMed

    Bondarenko, Olga; Dzyuba, Borys; Cosson, Jacky; Rodina, Marek; Linhart, Otomar

    2014-10-01

    The role of environmental ion composition and osmolality in Ca(2+) signaled activation was assessed in spermatozoa of brook trout Salvelinus fontinalis. Milt from ten mature males was obtained by abdominal massage. Spermatozoa motility was evaluated in 0, 100, and 300 mOsm/kg NaCl or sucrose solutions, buffered by 10 mM Tris-HCl pH 8.5. For investigation of spermatozoa reaction to external Ca(2+) concentration, 2 mM ethylene glycol tetraacetic acid (EGTA) was added to the activation media as a calcium ions chelator. For investigation of the effect of external Na(+) concentration in conditions of low external Ca(2+), 100 µM amiloride was added to the EGTA-containing solutions as a Na(+) transport blocker. Low motility was observed in sucrose (Na(+) free) solutions containing 2 mM EGTA but not in Na(+) solutions containing 2 mM EGTA. Addition of amiloride led to significantly increased motility (P < 0.05) compared with sucrose (Na(+) free) solutions containing 2 mM EGTA. We conclude that Na(+) transport in Ca(2+)-free solutions plays a regulatory role in brook trout spermatozoa activation. The influence of competitive Na(+) and Ca(2+) transport on the control of spermatozoa activation requires further study with respect to its application for improvement of artificial activation and storage media. PMID:24718964

  16. INTEX-NA: Intercontinental Chemical Transport Experiment - North America

    NASA Technical Reports Server (NTRS)

    Singh, Hanwant B.; Jacob, D.; Pfister, L.; Hipskind, R. Stephen (Technical Monitor)

    2002-01-01

    INTEX-NA is an integrated atmospheric chemistry field experiment to be performed over North America using the NASA DC-8 and P-3B aircraft as its primary platforms. It seeks to understand the exchange of chemicals and aerosols between continents and the global troposphere. The constituents of interest are ozone and its precursors (hydrocarbons, NOX and HOX), aerosols, and the major greenhouse gases (CO2, CH4, N2O). INTEX-NA will provide the observational database needed to quantify inflow, outflow, and transformations of chemicals over North America. INTEX-NA is to be performed in two phases. Phase A will take place during the period of May-August 2004 and Phase B during March-June 2006. Phase A is in summer when photochemistry is most intense and climatic issues involving aerosols and carbon cycle are most pressing, and Phase B is in spring when Asian transport to North America is at its peak. INTEX-NA will coordinate its activities with concurrent measurement programs including satellites (e. g. Terra, Aura, Envisat), field activities undertaken by the North American Carbon Program (NACP), and other U.S. and international partners. However, it is being designed as a 'stand alone' mission such that its successful execution is not contingent on other programs. Synthesis of the ensemble of observation from surface, airborne, and space platforms, with the help of global/regional models is an important It is anticipated that approximately 175 flight hours for each of the aircraft (DC-8 and P-3B) will be required for each Phase. Principal operational sites are tentatively selected to be Bangor, ME; Wallops Island, VA; Seattle, WA; Rhinelander, WI; Lancaster, CA; and New Orleans, LA. These coastal and continental sites can support large missions and are suitable for INTEX-NA objectives. The experiment will be supported by forecasts from meteorological and chemical models, satellite observations, surface networks, and enhanced O3,-sonde releases. In addition to

  17. Na+ transport in Acetabularia bypasses conductance of plasmalemma.

    PubMed

    Amtmann, A; Gradmann, D

    1994-04-01

    Na(+)-selective microelectrodes with the sensor ETH 227 have been used to measure the cytoplasmic Na+ concentration, [Na+]c, in Acetabularia. In the steady-state, [Na+]c is about 60 mM (external 460 mM). Steps in external Na+ concentration, [Na+]o, cause biexponential relaxations of [Na+]c which have formally been described by a serial three-compartment model (outside<==>compartment 1<==>compartment 2). From the initial slopes (some mMsec-1) net uptake and release of about 3 mumolm-2sec-1 Na+ are determined. Surprisingly, but consistent with previous tracer flux measurements (Mummert, H., Gradmann, D. 1991. J. Membrane Biol, 124:255-263), these Na+ fluxes are not accompanied by corresponding changes of the transplasmalemma voltage. [Na+]c is neither affected by the membrane voltage, nor by electrochemical gradients of H+ or Cl- across the plasmalemma, nor by cytoplasmic ATP. The results suggest a powerful vesicular transport system for ions which bypasses the conductance of the plasmalemma. In addition, transient increases of [Na+]c have been observed to take place facultatively during action potentials. The exponential distribution of the amplitudes of these transients (many small and few large peaks) points to local events in the more ore less close vicinity of the Na+ recording electrode. These events are suggested to consist of disruption of endoplasmic vesicles due to a loss of pressure in the cytoplasm.

  18. Transport of Na and Cl across the epithelium of ruminant forestomachs: rumen and omasum. A review.

    PubMed

    Martens, H; Gäbel, G

    1988-01-01

    Rumen: 1. It is generally accepted that sodium and chloride is transported across the rumen epithelium of ruminants in the mucosal-serosal direction by an active transport mechanism. In all in vitro studies the short circuit current, Isc, was significantly lower than the net transport of sodium, JNanet. It was concluded that most of the sodium is transported by an electrically silent mechanism. A Na, Cl cotransport and/or a double exchange system Na/H and Cl/HCO3 was proposed. 2. Recent in vitro studies in our laboratory revealed that the Na/H exchange inhibitor amiloride (1 mmol/l) reduced JNanet by 70%. The Na/K/2Cl-cotransport inhibitor bumetanide or furosemide (1 mmol/l) had no effect. 3. Replacement of permeable anions led to an inhibition of JNanet by 87%. However, under these experimental conditions Isc and JNanet were not significantly different. The remaining small electrogen transport of sodium was not influenced by mucosal amiloride. 4. It is concluded that two transport systems are operating in the ruminal epithelium: a Na/H exchange system which accounts for 80-90% of JNanet and an electrogen Na transport which is not sensitive against amiloride. Omasum: 1. The data concerning the transport of sodium and chloride in the omasum are very limited. In vivo measurements of flow rates demonstrated that sodium is absorbed by the omasum (40-60% of inflow in bull calves, 10-20% in sheep) and chloride is secreted. 2. In vitro studies with isolated preparation of sheep omasum epithelium demonstrated a net transport of Na and Cl in the mucosal-serosal direction. JNanet is completely abolished by ouabain (0.1 mmol/1) and JClnet by replacement of Na.

  19. Insulin and phorbol ester stimulate conductive Na/sup +/ transport through a common pathway

    SciTech Connect

    Civan, M.M.; Peterson-Yantorno, K.; O'Brien, T.G.

    1988-02-01

    Insulin stimulates Na/sup +/ transport across frog skin, toad urinary bladder, and the distal renal nephron. This stimulation reflects an increase in apical membrane Na/sup +/ permeability and a stimulation of the basolateral membrane Na,K-exchange pump. Considerable indirect evidence has suggested that the apical natriferic effect of insulin is mediated by activation of protein kinase C. However, no direct information has been available documenting that insulin and protein kinase C indeed share a common pathway in stimulating Na/sup +/ transport across frog skin. In the present work, the authors have studied the interaction of insulin and phorbol 12-myristate 13-acetate (PMA), a documented activator of protein kinase C. Preincubation of skins with 1,2-dioctanoylglycerol, another activator of protein kinase C, increases baseline Na/sup +/ transport and reduces the subsequent natriferic response to PMA. Preincubation with PMA markedly reduces the subsequent natriferic action of insulin. This effect does not appear to primarily reflect PMA-induced internalization of insulin receptors. The insulin receptors are localized on the basolateral surface of frog skin, but the application of PMA to this surface is much less effective than mucosal treatment in reducing the response to insulin. The current results provide documentation that insulin and protein kinase C share a common pathway in stimulating Na/sup +/ transport across frog skin. The data are consistent with the concept that the natriferic effect of insulin on frog skin is, at least in part, mediated by activation of protein kinase C.

  20. Expression of apical Na(+)-L-glutamine co-transport activity, B(0)-system neutral amino acid co-transporter (B(0)AT1) and angiotensin-converting enzyme 2 along the jejunal crypt-villus axis in young pigs fed a liquid formula.

    PubMed

    Yang, Chengbo; Yang, Xiaojian; Lackeyram, Dale; Rideout, Todd C; Wang, Zirong; Stoll, Barbara; Yin, Yulong; Burrin, Douglas G; Fan, Ming Z

    2016-06-01

    Gut apical amino acid (AA) transport activity is high at birth and during suckling, thus being essential to maintain luminal nutrient-dependent mucosal growth through providing AA as essential metabolic fuel, substrates and nutrient stimuli for cellular growth. Because system-B(0) Na(+)-neutral AA co-transporter (B(0)AT1, encoded by the SLC6A19 gene) plays a dominant role for apical uptake of large neutral AA including L-Gln, we hypothesized that high apical Na(+)-Gln co-transport activity, and B(0)AT1 (SLC6A19) in co-expression with angiotensin-converting enzyme 2 (ACE2) were expressed along the entire small intestinal crypt-villus axis in young animals via unique control mechanisms. Kinetics of Na(+)-Gln co-transport activity in the apical membrane vesicles, prepared from epithelial cells sequentially isolated along the jejunal crypt-villus axis from liquid formula-fed young pigs, were measured with the membrane potential being clamped to zero using thiocyanate. Apical maximal Na(+)-Gln co-transport activity was much higher (p < 0.05) in the upper villus cells than in the middle villus (by 29 %) and the crypt (by 30 %) cells, whereas Na(+)-Gln co-transport affinity was lower (p < 0.05) in the upper villus cells than in the middle villus and the crypt cells. The B(0)AT1 (SLC6A19) mRNA abundance was lower (p < 0.05) in the crypt (by 40-47 %) than in the villus cells. There were no significant differences in B(0)AT1 and ACE2 protein abundances on the apical membrane among the upper villus, the middle villus and the crypt cells. Our study suggests that piglet fast growth is associated with very high intestinal apical Na(+)-neutral AA uptake activities via abundantly co-expressing B(0)AT1 and ACE2 proteins in the apical membrane and by transcribing the B(0)AT1 (SLC6A19) gene in the epithelia along the entire crypt-villus axis. PMID:26984322

  1. HCO3(-)-coupled Na+ influx is a major determinant of Na+ turnover and Na+/K+ pump activity in rat hepatocytes

    SciTech Connect

    Fitz, J.G.; Lidofsky, S.D.; Weisiger, R.A.; Xie, M.H.; Cochran, M.; Grotmol, T.; Scharschmidt, B.F. )

    1991-05-01

    Recent studies in hepatocytes indicate that Na(+)-coupled HCO3- transport contributes importantly to regulation of intracellular pH and membrane HCO3- transport. However, the direction of net coupled Na+ and HCO3- movement and the effect of HCO3- on Na+ turnover and Na+/K+ pump activity are not known. In these studies, the effect of HCO3- on Na+ influx and turnover were measured in primary rat hepatocyte cultures with 22Na+, and (Na+)i was measured in single hepatocytes using the Na(+)-sensitive fluorochrome SBFI. Na+/K+ pump activity was measured in intact perfused rat liver and hepatocyte monolayers as Na(+)-dependent or ouabain-suppressible 86Rb uptake, and was measured in single hepatocytes as the effect of transient pump inhibition by removal of extracellular K+ on membrane potential difference (PD) and (Na+)i. In hepatocyte monolayers, HCO3- increased 22Na+ entry and turnover rates by 50-65%, without measurably altering 22Na+ pool size or cell volume, and HCO3- also increased Na+/K+ pump activity by 70%. In single cells, exposure to HCO3- produced an abrupt and sustained rise in (Na+)i from approximately 8 to 12 mM. Na+/K+ pump activity assessed in single cells by PD excursions during transient K+ removal increased congruent to 2.5-fold in the presence of HCO3-, and the rise in (Na+)i produced by inhibition of the Na+/K+ pump was similarly increased congruent to 2.5-fold in the presence of HCO3-. In intact perfused rat liver, HCO3- increased both Na+/K+ pump activity and O2 consumption. These findings indicate that, in hepatocytes, net coupled Na+ and HCO3- movement is inward and represents a major determinant of Na+ influx and Na+/K+ pump activity. About half of hepatic Na+/K+ pump activity appears dedicated to recycling Na+ entering in conjunction with HCO3- to maintain (Na+)i within the physiologic range.

  2. Evolutionarily divergent, Na+-regulated H+-transporting membrane-bound pyrophosphatases.

    PubMed

    Luoto, Heidi H; Nordbo, Erika; Malinen, Anssi M; Baykov, Alexander A; Lahti, Reijo

    2015-04-15

    Membrane-bound pyrophosphatase (mPPases) of various types consume pyrophosphate (PPi) to drive active H+ or Na+ transport across membranes. H+-transporting PPases are divided into phylogenetically distinct K+-independent and K+-dependent subfamilies. In the present study, we describe a group of 46 bacterial proteins and one archaeal protein that are only distantly related to known mPPases (23%-34% sequence identity). Despite this evolutionary divergence, these proteins contain the full set of 12 polar residues that interact with PPi, the nucleophilic water and five cofactor Mg2+ ions found in 'canonical' mPPases. They also contain a specific lysine residue that confers K+ independence on canonical mPPases. Two of the proteins (from Chlorobium limicola and Cellulomonas fimi) were expressed in Escherichia coli and shown to catalyse Mg2+-dependent PPi hydrolysis coupled with electrogenic H+, but not Na+ transport, in inverted membrane vesicles. Unique features of the new H+-PPases include their inhibition by Na+ and inhibition or activation, depending on PPi concentration, by K+ ions. Kinetic analyses of PPi hydrolysis over wide ranges of cofactor (Mg2+) and substrate (Mg2-PPi) concentrations indicated that the alkali cations displace Mg2+ from the enzyme, thereby arresting substrate conversion. These data define the new proteins as a novel subfamily of H+-transporting mPPases that partly retained the Na+ and K+ regulation patterns of their precursor Na+-transporting mPPases.

  3. Evolutionarily divergent, Na+-regulated H+-transporting membrane-bound pyrophosphatases.

    PubMed

    Luoto, Heidi H; Nordbo, Erika; Malinen, Anssi M; Baykov, Alexander A; Lahti, Reijo

    2015-04-15

    Membrane-bound pyrophosphatase (mPPases) of various types consume pyrophosphate (PPi) to drive active H+ or Na+ transport across membranes. H+-transporting PPases are divided into phylogenetically distinct K+-independent and K+-dependent subfamilies. In the present study, we describe a group of 46 bacterial proteins and one archaeal protein that are only distantly related to known mPPases (23%-34% sequence identity). Despite this evolutionary divergence, these proteins contain the full set of 12 polar residues that interact with PPi, the nucleophilic water and five cofactor Mg2+ ions found in 'canonical' mPPases. They also contain a specific lysine residue that confers K+ independence on canonical mPPases. Two of the proteins (from Chlorobium limicola and Cellulomonas fimi) were expressed in Escherichia coli and shown to catalyse Mg2+-dependent PPi hydrolysis coupled with electrogenic H+, but not Na+ transport, in inverted membrane vesicles. Unique features of the new H+-PPases include their inhibition by Na+ and inhibition or activation, depending on PPi concentration, by K+ ions. Kinetic analyses of PPi hydrolysis over wide ranges of cofactor (Mg2+) and substrate (Mg2-PPi) concentrations indicated that the alkali cations displace Mg2+ from the enzyme, thereby arresting substrate conversion. These data define the new proteins as a novel subfamily of H+-transporting mPPases that partly retained the Na+ and K+ regulation patterns of their precursor Na+-transporting mPPases. PMID:25662511

  4. Diffusive transport through compacted Na- and Ca-bentonite

    NASA Astrophysics Data System (ADS)

    Choi, J.-W.; Oscarson, D. W.

    1996-04-01

    The effect of exchangeable cation — Na + and Ca 2+ — on the diffusive transport of I -, Sr 2+ and 3H (as HTO) in compacted bentonite was examined using a through-diffusion method. Total intrinsic diffusion coefficients, Di, were determined from the steady-state flux of the diffusants through the clays, and apparent diffusion coefficients, Da, were obtained from the time lag technique. The clays were compacted to a dry bulk density of 1.3 Mg/m 3, and Na-bentonite was saturated with a solution of 100 mol NaCl/m3 and Ca-bentonite with one of 50 mol CaCl 2/m 3. The Di values for all diffusants are 2 to 6 times higher in the Ca- than Na-clay. We attribute this to the larger quasicrystal, or particle, size of Ca- compared to Na-bentonite. Hence, Ca-bentonite has a greater proportion of relatively large pores; this was confirmed by Hg intrusion porosimetry. This means the diffusion pathways in Ca-bentonite are less tortuous than those in Na-bentonite. Moreover, in some cases the effective porosity, or the porosity available for diffusive transport, may be greater in Ca-bentonite. The D a values are inversely proportional to the distribution coefficients of the diffusants with the clays.

  5. Laboratory Exercise on Active Transport.

    ERIC Educational Resources Information Center

    Stalheim-Smith, Ann; Fitch, Greg K.

    1985-01-01

    Describes a laboratory exercise which demonstrates qualitatively the specificity of the transport mechanism, including a consideration of the competitive inhibition, and the role of adenosine triphosphate (ATP) in active transport. The exercise, which can be completed in two to three hours by groups of four students, consistently produces reliable…

  6. Differential regulation of Na+ transporters along nephron during ANG II-dependent hypertension: distal stimulation counteracted by proximal inhibition.

    PubMed

    Nguyen, Mien T X; Lee, Donna H; Delpire, Eric; McDonough, Alicia A

    2013-08-15

    During angiotensin II (ANG II)-dependent hypertension, ANG II stimulates, while hypertension inhibits, Na(+) transporter activity to balance Na(+) output to input. This study tests the hypothesis that ANG II infusion activates Na(+) transporters in the distal nephron while inhibiting transporters along the proximal nephron. Male Sprague-Dawley rats were infused with ANG II (400 ng·kg(-1)·min(-1)) or vehicle for 2 wk. Kidneys were dissected (cortex vs. medulla) or fixed for immunohistochemistry (IHC). ANG II increased mean arterial pressure by 40 mmHg, urine Na(+) by 1.67-fold, and urine volume by 3-fold, evidence for hypertension and pressure natriuresis. Na(+) transporters' abundance and activation [assessed by phosphorylation (-P) or proteolytic cleavage] were measured by immunoblot. During ANG II infusion Na(+)/H(+) exchanger 3 (NHE3) abundance decreased in both cortex and medulla; Na-K-2Cl cotransporter 2 (NKCC2) decreased in medullary thick ascending loop of Henle (TALH) and increased, along with NKCC2-P, in cortical TALH; Na-Cl cotransporter (NCC) and NCC-P increased in the distal convoluted tubule; and epithelial Na(+) channel subunits and their cleaved forms were increased in both cortex and medulla. Like NKCC2, STE20/SPS1-related proline alanine-rich kinase (SPAK) and SPAK-P were decreased in medulla and increased in cortex. By IHC, during ANG II NHE3 remained localized to proximal tubule microvilli at lower abundance, and the differential regulation of NKCC2 and NKCC2-P in cortex versus medulla was evident. In summary, ANG II infusion increases Na(+) transporter abundance and activation from cortical TALH to medullary collecting duct while the hypertension drives a natriuresis response evident as decreased Na(+) transporter abundance and activation from proximal tubule through medullary TALH. PMID:23720346

  7. Sodium transport is modulated by p38 kinase-dependent cross-talk between ENaC and Na,K-ATPase in collecting duct principal cells.

    PubMed

    Wang, Yu-Bao; Leroy, Valérie; Maunsbach, Arvid B; Doucet, Alain; Hasler, Udo; Dizin, Eva; Ernandez, Thomas; de Seigneux, Sophie; Martin, Pierre-Yves; Féraille, Eric

    2014-02-01

    In relation to dietary Na(+) intake and aldosterone levels, collecting duct principal cells are exposed to large variations in Na(+) transport. In these cells, Na(+) crosses the apical membrane via epithelial Na(+) channels (ENaC) and is extruded into the interstitium by Na,K-ATPase. The activity of ENaC and Na,K-ATPase must be highly coordinated to accommodate variations in Na(+) transport and minimize fluctuations in intracellular Na(+) concentration. We hypothesized that, independent of hormonal stimulus, cross-talk between ENaC and Na,K-ATPase coordinates Na(+) transport across apical and basolateral membranes. By varying Na(+) intake in aldosterone-clamped rats and overexpressing γ-ENaC or modulating apical Na(+) availability in cultured mouse collecting duct cells, enhanced apical Na(+) entry invariably led to increased basolateral Na,K-ATPase expression and activity. In cultured collecting duct cells, enhanced apical Na(+) entry increased the basolateral cell surface expression of Na,K-ATPase by inhibiting p38 kinase-mediated endocytosis of Na,K-ATPase. Our results reveal a new role for p38 kinase in mediating cross-talk between apical Na(+) entry via ENaC and its basolateral exit via Na,K-ATPase, which may allow principal cells to maintain intracellular Na(+) concentrations within narrow limits.

  8. Sodium Ion Transport Mechanisms in Antiperovskite Electrolytes Na3OBr and Na4OI2: An in Situ Neutron Diffraction Study.

    PubMed

    Zhu, Jinlong; Wang, Yonggang; Li, Shuai; Howard, John W; Neuefeind, Jörg; Ren, Yang; Wang, Hui; Liang, Chengdu; Yang, Wenge; Zou, Ruqiang; Jin, Changqing; Zhao, Yusheng

    2016-06-20

    Na-rich antiperovskites are recently developed solid electrolytes with enhanced sodium ionic conductivity and show promising functionality as a novel solid electrolyte in an all solid-state battery. In this work, the sodium ionic transport pathways of the parent compound Na3OBr, as well as the modified layered antiperovskite Na4OI2, were studied and compared through temperature-dependent neutron diffraction combined with the maximum entropy method. In the cubic Na3OBr antiperovskite, the nuclear density distribution maps at 500 K indicate that sodium ions hop within and among oxygen octahedra, and Br(-) ions are not involved. In the tetragonal Na4OI2 antiperovskite, Na ions, which connect octahedra in the ab plane, have the lowest activation energy barrier. The transport of sodium ions along the c axis is assisted by I(-) ions. PMID:27251879

  9. Activated transport in AMTEC electrodes

    NASA Astrophysics Data System (ADS)

    Williams, R. M.; Jeffries-Nakamura, B.; Ryan, M. A.; Underwood, M. L.; Oconnor, D.; Kikkert, S.

    1992-08-01

    Transport of alkali metal atoms through porous cathodes of alkali metal thermal-to-electric converter (AMTEC) cells is responsible for significant, reducible losses in the electrical performance of these cells. Experimental evidence for activated transport of metal atoms at grain surfaces and boundaries within some AMTEC electrodes has been derived from temperature dependent studies as well as from analysis of the detailed frequency dependence of ac impedance results for other electrodes, including thin, mature molybdenum electrodes which exhibit transport dominated by free molecular flow of sodium gas at low frequencies or dc conditions. Activated surface transport will almost always exist in parallel with free molecular flow transport, and the process of alkali atom adsorption/desorption from the electrode surface will invariably be part of the transport process, and possibly a dominant part in some cases. Little can be learned about the detailed mass transport process from the ac impedance or current voltage curves of an electrode at one set of operating parameters, because the transport process includes a number of important physical parameters that are not all uniquely determined by one experiment. The temperature dependence of the diffusion coefficient of the alkali metal through the electrode in several cases provides an activation energy and pre-exponential, but at least two activated processes may be operative, and the activation parameters should be expected to depend on the alkali metal activity gradient that the electrode experiences. In the case of Pt/W/Mn electrodes operated for 2500 hours, limiting currents varied with electrode thickness, and the activation parameters could be assigned primarily to the surface/grain boundary diffusion process.

  10. Glucocorticoids and renal Na+ transport: implications for hypertension and salt sensitivity

    PubMed Central

    Hunter, Robert W; Ivy, Jessica R; Bailey, Matthew A

    2014-01-01

    The clinical manifestations of glucocorticoid excess include central obesity, hyperglycaemia, dyslipidaemia, electrolyte abnormalities and hypertension. A century on from Cushing's original case study, these cardinal features are prevalent in industrialized nations. Hypertension is the major modifiable risk factor for cardiovascular and renal disease and reflects underlying abnormalities of Na+ homeostasis. Aldosterone is a master regulator of renal Na+ transport but here we argue that glucocorticoids are also influential, particularly during moderate excess. The hypothalamic–pituitary–adrenal axis can affect renal Na+ homeostasis on multiple levels, systemically by increasing mineralocorticoid synthesis and locally by actions on both the mineralocorticoid and glucocorticoid receptors, both of which are expressed in the kidney. The kidney also expresses both of the 11β-hydroxysteroid dehydrogenase (11βHSD) enzymes. The intrarenal generation of active glucocorticoid by 11βHSD1 stimulates Na+ reabsorption; failure to downregulate the enzyme during adaption to high dietary salt causes salt-sensitive hypertension. The deactivation of glucocorticoid by 11βHSD2 underpins the regulatory dominance for Na+ transport of mineralocorticoids and defines the ‘aldosterone-sensitive distal nephron’. In summary, glucocorticoids can stimulate renal transport processes conventionally attributed to the renin–angiotensin–aldosterone system. Importantly, Na+ and volume homeostasis do not exert negative feedback on the hypothalamic–pituitary–adrenal axis. These actions are therefore clinically relevant and may contribute to the pathogenesis of hypertension in conditions associated with elevated glucocorticoid levels, such as the metabolic syndrome and chronic stress. PMID:24535442

  11. Characterization of the endogenous carnitine transport and expression of a rat renal Na(+)-dependent carnitine transport system in Xenopus laevis oocytes.

    PubMed Central

    Berardi, S; Hagenbuch, B; Carafoli, E; Krähenbühl, S

    1995-01-01

    L-Carnitine transport was characterized in Xenopus laevis oocytes before and after injection of mRNA isolated from rat renal cortex. Non-injected oocytes revealed endogenous Na(+)-dependent transport of L-carnitine. After injection of 15 ng of rat kidney mRNA, the Na(+)-dependent L-carnitine transport increased 2-3-fold, reaching maximal activity after 5-6 days. The expressed carnitine transport was maximal at pH 7.5, whereas the endogenous transport showed no clear maximum between pH 6.0 and 8.5. Kinetic analysis revealed apparent Km values for L-carnitine of 66 microM for the endogenous and 149 microM for the expressed transport. Trimethyl-lysine and D-carnitine inhibited both the endogenous and the expressed transport. In contrast, L-acetylcarnitine, L-isovalerylcarnitine, L-palmitoylcarnitine and butyrobetaine inhibited predominantly the expressed transport, whereas glycinebetaine had no inhibitory effect on either transport system. Size-fractionated rat renal-cortex mRNA (median size 2 kb) induced a 3-fold higher L-carnitine transport than did unfractionated mRNA. These studies demonstrate that Xenopus laevis oocytes exhibit Na(+)-dependent L-carnitine transport and provide the basis for expression-cloning of a rat renal Na(+)-dependent L-carnitine transport system. PMID:7626001

  12. Na+/K+-ATPase: Activity and inhibition

    NASA Astrophysics Data System (ADS)

    Čolović, M.; Krstić, D.; Krinulović, K.; Momić, T.; Savić, J.; Vujačić, A.; Vasić, V.

    2009-09-01

    The aim of the study was to give an overview of the mechanism of inhibition of Na+/K+-ATPase activity induced by some specific and non specific inhibitors. For this purpose, the effects of some ouabain like compounds (digoxin, gitoxin), noble metals complexes ([PtCl2DMSO2], [AuCl4]-, [PdCl4]2-, [PdCl(dien)]+, [PdCl(Me4dien)]+), transition metal ions (Cu2+, Zn2+, Fe2+, Co2+), and heavy metal ions (Hg2+, Pb2+, Cd2+) on the activity of Na+/K+-ATPase from rat synaptic plasma membranes (SPM), porcine cerebral cortex and human erythrocytes were discussed.

  13. Sodium and proton effects on inward proton transport through Na/K pumps.

    PubMed

    Mitchell, Travis J; Zugarramurdi, Camila; Olivera, J Fernando; Gatto, Craig; Artigas, Pablo

    2014-06-17

    The Na/K pump hydrolyzes ATP to export three intracellular Na (Nai) as it imports two extracellular K (Ko) across animal plasma membranes. Within the protein, two ion-binding sites (sites I and II) can reciprocally bind Na or K, but a third site (site III) exclusively binds Na in a voltage-dependent fashion. In the absence of Nao and Ko, the pump passively imports protons, generating an inward current (IH). To elucidate the mechanisms of IH, we used voltage-clamp techniques to investigate the [H]o, [Na]o, and voltage dependence of IH in Na/K pumps from ventricular myocytes and in ouabain-resistant pumps expressed in Xenopus oocytes. Lowering pHo revealed that Ho both activates IH (in a voltage-dependent manner) and inhibits it (in a voltage-independent manner) by binding to different sites. Nao effects depend on pHo; at pHo where no Ho inhibition is observed, Nao inhibits IH at all concentrations, but when applied at pHo that inhibits pump-mediated current, low [Na]o activates IH and high [Na]o inhibits it. Our results demonstrate that IH is a property inherent to Na/K pumps, not linked to the oocyte expression environment, explains differences in the characteristics of IH previously reported in the literature, and supports a model in which 1), protons leak through site III; 2), binding of two Na or two protons to sites I and II inhibits proton transport; and 3), pumps with mixed Na/proton occupancy of sites I and II remain permeable to protons.

  14. Sodium and proton effects on inward proton transport through Na/K pumps.

    PubMed

    Mitchell, Travis J; Zugarramurdi, Camila; Olivera, J Fernando; Gatto, Craig; Artigas, Pablo

    2014-06-17

    The Na/K pump hydrolyzes ATP to export three intracellular Na (Nai) as it imports two extracellular K (Ko) across animal plasma membranes. Within the protein, two ion-binding sites (sites I and II) can reciprocally bind Na or K, but a third site (site III) exclusively binds Na in a voltage-dependent fashion. In the absence of Nao and Ko, the pump passively imports protons, generating an inward current (IH). To elucidate the mechanisms of IH, we used voltage-clamp techniques to investigate the [H]o, [Na]o, and voltage dependence of IH in Na/K pumps from ventricular myocytes and in ouabain-resistant pumps expressed in Xenopus oocytes. Lowering pHo revealed that Ho both activates IH (in a voltage-dependent manner) and inhibits it (in a voltage-independent manner) by binding to different sites. Nao effects depend on pHo; at pHo where no Ho inhibition is observed, Nao inhibits IH at all concentrations, but when applied at pHo that inhibits pump-mediated current, low [Na]o activates IH and high [Na]o inhibits it. Our results demonstrate that IH is a property inherent to Na/K pumps, not linked to the oocyte expression environment, explains differences in the characteristics of IH previously reported in the literature, and supports a model in which 1), protons leak through site III; 2), binding of two Na or two protons to sites I and II inhibits proton transport; and 3), pumps with mixed Na/proton occupancy of sites I and II remain permeable to protons. PMID:24940773

  15. Interaction of α-Lipoic Acid with the Human Na+/Multivitamin Transporter (hSMVT)*

    PubMed Central

    Zehnpfennig, Britta; Wiriyasermkul, Pattama; Carlson, David A.; Quick, Matthias

    2015-01-01

    The human Na+/multivitamin transporter (hSMVT) has been suggested to transport α-lipoic acid (LA), a potent antioxidant and anti-inflammatory agent used in therapeutic applications, e.g. in the treatment of diabetic neuropathy and Alzheimer disease. However, the molecular basis of the cellular delivery of LA and in particular the stereospecificity of the transport process are not well understood. Here, we expressed recombinant hSMVT in Pichia pastoris and used affinity chromatography to purify the detergent-solubilized protein followed by reconstitution of hSMVT in lipid bilayers. Using a combined approach encompassing radiolabeled LA transport and equilibrium binding studies in conjunction with the stabilized R-(+)- and S-(−)-enantiomers and the R,S-(+/−) racemic mixture of LA or lipoamide, we identified the biologically active form of LA, R-LA, to be the physiological substrate of hSMVT. Interaction of R-LA with hSMVT is strictly dependent on Na+. Under equilibrium conditions, hSMVT can simultaneously bind ∼2 molecules of R-LA in a biphasic binding isotherm with dissociation constants (Kd) of 0.9 and 7.4 μm. Transport of R-LA in the oocyte and reconstituted system is exclusively dependent on Na+ and exhibits an affinity of ∼3 μm. Measuring transport with known amounts of protein in proteoliposomes containing hSMVT in outside-out orientation yielded a catalytic turnover number (kcat) of about 1 s−1, a value that is well in agreement with other Na+-coupled transporters. Our data suggest that hSMVT-mediated transport is highly specific for R-LA at our tested concentration range, a finding with wide ramifications for the use of LA in therapeutic applications. PMID:25971966

  16. Brain Na+, K+-ATPase Activity In Aging and Disease

    PubMed Central

    de Lores Arnaiz, Georgina Rodríguez; Ordieres, María Graciela López

    2014-01-01

    Na+/K+ pump or sodium- and potassium-activated adenosine 5’-triphosphatase (Na+, K+-ATPase), its enzymatic version, is a crucial protein responsible for the electrochemical gradient across the cell membranes. It is an ion transporter, which in addition to exchange cations, is the ligand for cardenolides. This enzyme regulates the entry of K+ with the exit of Na+ from cells, being the responsible for Na+/K+ equilibrium maintenance through neuronal membranes. This transport system couples the hydrolysis of one molecule of ATP to exchange three sodium ions for two potassium ions, thus maintaining the normal gradient of these cations in animal cells. Oxidative metabolism is very active in brain, where large amounts of chemical energy as ATP molecules are consumed, mostly required for the maintenance of the ionic gradients that underlie resting and action potentials which are involved in nerve impulse propagation, neurotransmitter release and cation homeostasis. Protein phosphorylation is a key process in biological regulation. At nervous system level, protein phosphorylation is the major molecular mechanism through which the function of neural proteins is modulted in response to extracellular signals, including the response to neurotransmitter stimuli. It is the major mechanism of neural plasticity, including memory processing. The phosphorylation of Na+, K+-ATPase catalytic subunit inhibits enzyme activity whereas the inhibition of protein kinase C restores the enzyme activity. The dephosphorylation of neuronal Na+, K+-ATPase is mediated by calcineurin, a serine / threonine phosphatase. The latter enzyme is involved in a wide range of cellular responses to Ca2+ mobilizing signals, in the regulation of neuronal excitability by controlling the activity of ion channels, in the release of neurotransmitters and hormones, as well as in synaptic plasticity and gene transcription. In the present article evidence showing Na+, K+-ATPase involvement in signaling pathways

  17. Effects of cadmium on Na+ transport in the isolated skin of the toad Pleurodema thaul.

    PubMed

    Suwalsky, M; Norris, B; Cárdenas, H

    2005-12-01

    Cadmium ions applied to either (outer or inner) surface of the isolated toad skin dose-dependently increased the short-circuit current (SCC), the potential difference (V) and the active sodium conductance (G(Na)) in the concentration range 0.07-0.50mM. Maximal stimulatory effect was over 30% with an EC(50) of about 0.1mM. The effect of the highest concentration used (0.75mM) decreased considerably, and when it was applied to the inner surface (10 experiments), induced between 30% and 40% inhibition of the electric parameters in four experiments. Pretreatment with amiloride inverted the stimulatory effect of externally applied Cd(2+), suggesting competitive action on the apical Na(+) channel. The effect of noradrenaline (NA) was increased after outer application of Cd(2+) and decreased after inner application of the metal: the latter effect might be due to cadmium inhibition of the activity of Na(+),K(+)-ATPase. On the other hand, pretreatment with amiloride was followed by partial although transient reversal of its effects by serosal Cd(2+), which might be explained by action of cadmium on cytoplasmic lysine residues concerned with Na(+) channel gating. The amiloride test showed that the increment of the electric parameters was due principally to stimulation of the driving potential for Na(+) (V-E(Na(+))) and that inhibition was accompanied by a reduction in the V-E(Na(+)) and by a significant decrease in skin resistance indicating possible disruption of membrane or cell integrity. These data are in favor of the possibility that externally applied Cd(2+) activates toad skin ion transport, partly by increasing apical sodium conductance and also by stimulating the V-E(Na(+)), and that internally applied Cd(2+), with easier access to membrane and cellular constituents, may inhibit the sodium pump. PMID:16266750

  18. Splice cassette II of Na+,HCO3(-) cotransporter NBCn1 (slc4a7) interacts with calcineurin A: implications for transporter activity and intracellular pH control during rat artery contractions.

    PubMed

    Danielsen, Andreas A; Parker, Mark D; Lee, Soojung; Boron, Walter F; Aalkjaer, Christian; Boedtkjer, Ebbe

    2013-03-22

    Activation of Na(+),HCO3(-) cotransport in vascular smooth muscle cells (VSMCs) contributes to intracellular pH (pH(i)) control during artery contraction, but the signaling pathways involved have been unknown. We investigated whether physical and functional interactions between the Na(+),HCO3(-) cotransporter NBCn1 (slc4a7) and the Ca(2+)/calmodulin-activated serine/threonine phosphatase calcineurin exist and play a role for pHi control in VSMCs. Using a yeast two-hybrid screen, we found that splice cassette II from the N terminus of NBCn1 interacts with calcineurin Aβ. When cassette II was truncated or mutated to disrupt the putative calcineurin binding motif PTVVIH, the interaction was abolished. Native NBCn1 and calcineurin Aβ co-immunoprecipitated from A7r5 rat VSMCs. A peptide (acetyl-DDIPTVVIH-amide), which mimics the putative calcineurin binding motif, inhibited the co-immunoprecipitation whereas a mutated peptide (acetyl-DDIATAVAA-amide) did not. Na(+),HCO3(-) cotransport activity was investigated in VSMCs of mesenteric arteries after an NH4(+) prepulse. During depolarization with 50 mM extracellular K(+) to raise intracellular [Ca(2+)], Na(+),HCO3(-) cotransport activity was inhibited 20-30% by calcineurin inhibitors (FK506 and cyclosporine A). FK506 did not affect Na(+),HCO3(-) cotransport activity in VSMCs when cytosolic [Ca(2+)] was lowered by buffering, nor did it disrupt binding between NBCn1 and calcineurin Aβ. FK506 augmented the intracellular acidification of VSMCs during norepinephrine-induced artery contractions. No physical or functional interactions between calcineurin Aβ and the Na(+)/H(+) exchanger NHE1 were observed in VSMCs. In conclusion, we demonstrate a physical interaction between calcineurin Aβ and cassette II of NBCn1. Intracellular Ca(2+) activates Na(+),HCO3(-) cotransport activity in VSMCs in a calcineurin-dependent manner which is important for protection against intracellular acidification.

  19. Intracellular Cl- as a signaling ion that potently regulates Na+/HCO3- transporters.

    PubMed

    Shcheynikov, Nikolay; Son, Aran; Hong, Jeong Hee; Yamazaki, Osamu; Ohana, Ehud; Kurtz, Ira; Shin, Dong Min; Muallem, Shmuel

    2015-01-20

    Cl(-) is a major anion in mammalian cells involved in transport processes that determines the intracellular activity of many ions and plasma membrane potential. Surprisingly, a role of intracellular Cl(-) (Cl(-) in) as a signaling ion has not been previously evaluated. Here we report that Cl(-) in functions as a regulator of cellular Na(+) and HCO3 (-) concentrations and transepithelial transport through modulating the activity of several electrogenic Na(+)-HCO3 (-) transporters. We describe the molecular mechanism(s) of this regulation by physiological Cl(-) in concentrations highlighting the role of GXXXP motifs in Cl(-) sensing. Regulation of the ubiquitous Na(+)-HCO3(-) co-transport (NBC)e1-B is mediated by two GXXXP-containing sites; regulation of NBCe2-C is dependent on a single GXXXP motif; and regulation of NBCe1-A depends on a cryptic GXXXP motif. In the basal state NBCe1-B is inhibited by high Cl(-) in interacting at a low affinity GXXXP-containing site. IP3 receptor binding protein released with IP3 (IRBIT) activation of NBCe1-B unmasks a second high affinity Cl(-) in interacting GXXXP-dependent site. By contrast, NBCe2-C, which does not interact with IRBIT, has a single high affinity N-terminal GXXP-containing Cl(-) in interacting site. NBCe1-A is unaffected by Cl(-) in between 5 and 140 mM. However, deletion of NBCe1-A residues 29-41 unmasks a cryptic GXXXP-containing site homologous with the NBCe1-B low affinity site that is involved in inhibition of NBCe1-A by Cl(-) in. These findings reveal a cellular Cl(-) in sensing mechanism that plays an important role in the regulation of Na(+) and HCO3 (-) transport, with critical implications for the role of Cl(-) in cellular ion homeostasis and epithelial fluid and electrolyte secretion.

  20. Serine protease activation of near-silent epithelial Na+ channels.

    PubMed

    Caldwell, Ray A; Boucher, Richard C; Stutts, M Jackson

    2004-01-01

    The regulation of epithelial Na+ channel (ENaC) function is critical for normal salt and water balance. This regulation is achieved through cell surface insertion/retrieval of channels, by changes in channel open probability (Po), or through a combination of these processes. Epithelium-derived serine proteases, including channel activating protease (CAP) and prostasin, regulate epithelial Na+ transport, but the molecular mechanism is unknown. We tested the hypothesis that extracellular serine proteases activate a near-silent ENaC population resident in the plasma membrane. Single-channel events were recorded in outside-out patches from fibroblasts (NIH/3T3) stably expressing rat alpha-, beta-, and gamma-subunits (rENaC), before and during exposure to trypsin, a serine protease homologous to CAP and prostasin. Under baseline conditions, near-silent patches were defined as having rENaC activity (NPo) < 0.03, where N is the number of channels. Within 1-5 min of 3 microg/ml bath trypsin superfusion, NPo increased approximately 66-fold (n = 7). In patches observed to contain a single functional channel, trypsin increased Po from 0.02 +/- 0.01 to 0.57 +/- 0.03 (n = 3, mean +/- SE), resulting from the combination of an increased channel open time and decreased channel closed time. Catalytic activity was required for activation of near-silent ENaC. Channel conductance and the Na+/Li+ current ratio with trypsin were similar to control values. Modulation of ENaC Po by endogenous epithelial serine proteases is a potentially important regulator of epithelial Na+ transport, distinct from the regulation achieved by hormone-induced plasma membrane insertion of channels. PMID:12967915

  1. Slc26A9 - anion exchanger, channel and Na+ transporter

    PubMed Central

    Chang, Min-Hwang; Plata, Consuelo; Zandi-Nejad, Kambiz; Sinđić, Aleksandra; Sussman, Caroline R.; Mercado, Adriana; Broumand, Vadjista; Raghuram, Viswanathan; Mount, David B.; Romero, Michael F.

    2009-01-01

    The SLC26 gene family encodes anion transporters with diverse functional attributes: (a) anion exchanger, (b) anion sensor and (c) anion conductance (likely channel). We have cloned and studied Slc26a9, a paralog expressed mostly in lung and stomach. Immunohistochemistry shows that Slc26a9 is present at apical and intracellular membranes of lung and stomach epithelia. Using expression in Xenopus laevis oocytes and ion-sensitive microelectrodes, we discovered that Slc26a9 has a novel function not found in any other Slc26 proteins – cation coupling. Intracellular pH and voltage measurements show that Slc26a9 is a nCl--HCO3- exchanger, suggesting roles in gastric HCl secretion or pulmonary HCO3- secretion; Na+ electrodes and uptakes reveal that Slc26a9 has a cation-dependence. Single channel measurements indicate that Slc26a9 displays discrete open and close states. These experiments show that Slc26a9 has three discrete physiological modes: nCl--HCO3- exchanger, Cl- channel, and Na+-anion cotransporter. Thus, the Slc26a9 transporter-channel is uniquely suited for dynamic and tissue-specific physiology or regulation in epithelial tissues. PMID:19365592

  2. Na+/H+ Exchange Activity in the Plasma Membrane of Arabidopsis1

    PubMed Central

    Qiu, Quan-Sheng; Barkla, Bronwyn J.; Vera-Estrella, Rosario; Zhu, Jian-Kang; Schumaker, Karen S.

    2003-01-01

    In plants, Na+/H+ exchangers in the plasma membrane are critical for growth in high levels of salt, removing toxic Na+ from the cytoplasm by transport out of the cell. The molecular identity of a plasma membrane Na+/H+ exchanger in Arabidopsis (SOS1) has recently been determined. In this study, immunological analysis provided evidence that SOS1 localizes to the plasma membrane of leaves and roots. To characterize the transport activity of this protein, purified plasma membrane vesicles were isolated from leaves of Arabidopsis. Na+/H+ exchange activity, monitored as the ability of Na to dissipate an established pH gradient, was absent in plants grown without salt. However, exchange activity was induced when plants were grown in 250 mm NaCl and increased with prolonged salt exposure up to 8 d. H+-coupled exchange was specific for Na, because chloride salts of other monovalent cations did not dissipate the pH gradient. Na+/H+ exchange activity was dependent on Na (substrate) concentration, and kinetic analysis indicated that the affinity (apparent Km) of the transporter for Na+ is 22.8 mm. Data from two experimental approaches supports electroneutral exchange (one Na+ exchanged for one proton): (a) no change in membrane potential was measured during the exchange reaction, and (b) Na+/H+ exchange was unaffected by the presence or absence of a membrane potential. Results from this research provide a framework for future studies into the regulation of the plant plasma membrane Na+/H+ exchanger and its relative contribution to the maintenance of cellular Na+ homeostasis during plant growth in salt. PMID:12805632

  3. Scanning ion-selective electrode technique and X-ray microanalysis provide direct evidence of contrasting Na+ transport ability from root to shoot in salt-sensitive cucumber and salt-tolerant pumpkin under NaCl stress.

    PubMed

    Lei, Bo; Huang, Yuan; Sun, Jingyu; Xie, Junjun; Niu, Mengliang; Liu, Zhixiong; Fan, Molin; Bie, Zhilong

    2014-12-01

    Grafting onto salt-tolerant pumpkin rootstock can increase cucumber salt tolerance. Previous studies have suggested that this can be attributed to pumpkin roots with higher capacity to limit the transport of Na(+) to the shoot than cucumber roots. However, the mechanism remains unclear. This study investigated the transport of Na(+) in salt-tolerant pumpkin and salt-sensitive cucumber plants under high (200 mM) or moderate (90 mM) NaCl stress. Scanning ion-selective electrode technique showed that pumpkin roots exhibited a higher capacity to extrude Na(+), and a correspondingly increased H(+) influx under 200 or 90 mM NaCl stress. The 200 mM NaCl induced Na(+)/H(+) exchange in the root was inhibited by amiloride (a Na(+)/H(+) antiporter inhibitor) or vanadate [a plasma membrane (PM) H(+) -ATPase inhibitor], indicating that Na(+) exclusion in salt stressed pumpkin and cucumber roots was the result of an active Na(+)/H(+) antiporter across the PM, and the Na(+)/H(+) antiporter system in salt stressed pumpkin roots was sufficient to exclude Na(+) X-ray microanalysis showed higher Na(+) in the cortex, but lower Na(+) in the stele of pumpkin roots than that in cucumber roots under 90 mM NaCl stress, suggesting that the highly vacuolated root cortical cells of pumpkin roots could sequester more Na(+), limit the radial transport of Na(+) to the stele and thus restrict the transport of Na(+) to the shoot. These results provide direct evidence for pumpkin roots with higher capacity to limit the transport of Na(+) to the shoot than cucumber roots.

  4. Development of Na/sup +/-dependent hexose transport in cultured renal epithelial cells (LLC-PK/sub 1/)

    SciTech Connect

    Weiss, E.R.; Amsler, K.; Dawson, W.D.; Cook, J.S.

    1984-01-01

    A number of factors were explored to analyze how they interact to yield the increasing transport capacity in differentiating cell populations. These factors include the number of functional transporters in the population, the distribution of these transporters among the individual cells, the Na/sup +/ chemical gradient, the transmembrane potential, the pathways and activities of these pathways for efflux of glucoside, and cell-cell coupling between accumulating and non-accumulating cells. 35 references, 9 figures, 2 tables. (ACR)

  5. Ethanol effects on active and passive Na+ flux in toad bladder.

    PubMed

    Amaranath, L; Anton, A H

    1977-11-01

    Ethanol, like other anesthetics, has been reported to interfere with active Na+ transport in living membranes. In an attempt to elucidate the mechanism by which ethanol exerts this action, we tested in the toad bladder membrane: 1) the effect of ethanol on active Na+ transport, 2) the interaction of ethanol with vasopressin on Na+ transport, and 3) the effect of ethanol on passive Na+ flux. We found that, a) 1-500 microgram/ml of ethanol stimulated, and 10,000 microgram/ml depressed active Na+ transport; b) the combined effect of stimulating concentrations of ethanol and vasopressin, although suggestive of a positive interaction, might have arisen by chance (p = 0.08); c) depressant concentrations of ethanol failed to suppress the stimulation by vasopressin; and d) passive Na+ flux in bladders treated with ouabain and ethacrynic acid was not affected by ethanol (1-100 microgram/ml). These results indicate that ethanol in concentrations ranging from 1 to 10,000 microgram/ml does not block ATP/ATPase Na+ pump but apparently exerts a dose-dependent, stimulant-depressant effect on Na+ channels in the membrane.

  6. Sodium arsenite affects Na+ transport in the isolated skin of the toad Pleurodema thaul.

    PubMed

    Suwalsky, Mario; Rivera, Cecilia; Norris, Beryl; Cárdenas, Hernán

    2007-01-01

    Arsenic, applied as sodium arsenite (As(III)) to either inner or outer surfaces of the isolated toad skin, dose-dependently decreased the short-circuit current (Isc), potential difference (PD) and sodium conductance (G(Na)) in the concentration range 1-1000 microM, with effects often lasting over 3 h. Maximal inhibitory effect was over 90% with an IC(50) of about 34 microM. Applied during amiloride block, As(III) did not change this effect. However, an increase in electric parameters was noted during the initial 30 min in 22 experiments, indicating a possible translocation of cytosolic protein kinase C (PKC) to the membrane within 15 min, thus stimulating sodium transport; this is followed by a progressive inhibition of kinase activity. Comparative effects of amiloride (8 microM), As(III) (100 microM, outer surface) and noradrenaline (NA, 10 microM, inner surface) showed a significant increase in the stimulatory effect of NA on the electric parameters, which could be the result of arsenite clustering of cell surface receptors and activation of ensuing cellular signal transduction pathways. Ouabain 5 microM, followed by As(III) 100 microM, also stimulated the skin response to NA (10 microM), although the duration of the two phases of the response was markedly shortened. The exact mechanism is still in doubt: however, As(III) increases cerebral metabolites of NA and ouabain can increase NA efflux from tissue slices. The amiloride test, performed with As(III) in the outer surface, confirmed significant decrease in all the parameters: the driving force (E(Na)), sodium conductance (G(Na)), and importantly, shunt conductance (G(sh)), due to the known fact that arsenic inhibits gap junctional intercellular communication. PMID:17055342

  7. Signal focusing through active transport.

    PubMed

    Godec, Aljaž; Metzler, Ralf

    2015-07-01

    The accuracy of molecular signaling in biological cells and novel diagnostic devices is ultimately limited by the counting noise floor imposed by the thermal diffusion. Motivated by the fact that messenger RNA and vesicle-engulfed signaling molecules transiently bind to molecular motors and are actively transported in biological cells, we show here that the random active delivery of signaling particles to within a typical diffusion distance to the receptor generically reduces the correlation time of the counting noise. Considering a variety of signaling particle sizes from mRNA to vesicles and cell sizes from prokaryotic to eukaryotic cells, we show that the conditions for active focusing-faster and more precise signaling-are indeed compatible with observations in living cells. Our results improve the understanding of molecular cellular signaling and novel diagnostic devices.

  8. Signal focusing through active transport

    NASA Astrophysics Data System (ADS)

    Godec, Aljaž; Metzler, Ralf

    2015-07-01

    The accuracy of molecular signaling in biological cells and novel diagnostic devices is ultimately limited by the counting noise floor imposed by the thermal diffusion. Motivated by the fact that messenger RNA and vesicle-engulfed signaling molecules transiently bind to molecular motors and are actively transported in biological cells, we show here that the random active delivery of signaling particles to within a typical diffusion distance to the receptor generically reduces the correlation time of the counting noise. Considering a variety of signaling particle sizes from mRNA to vesicles and cell sizes from prokaryotic to eukaryotic cells, we show that the conditions for active focusing—faster and more precise signaling—are indeed compatible with observations in living cells. Our results improve the understanding of molecular cellular signaling and novel diagnostic devices.

  9. Position of the Third Na+ Site in the Aspartate Transporter GltPh and the Human Glutamate Transporter, EAAT1

    PubMed Central

    Bastug, Turgut; Heinzelmann, Germano; Kuyucak, Serdar; Salim, Marietta; Vandenberg, Robert J.; Ryan, Renae M.

    2012-01-01

    Glutamate transport via the human excitatory amino acid transporters is coupled to the co-transport of three Na+ ions, one H+ and the counter-transport of one K+ ion. Transport by an archaeal homologue of the human glutamate transporters, GltPh, whose three dimensional structure is known is also coupled to three Na+ ions but only two Na+ ion binding sites have been observed in the crystal structure of GltPh. In order to fully utilize the GltPh structure in functional studies of the human glutamate transporters, it is essential to understand the transport mechanism of GltPh and accurately determine the number and location of Na+ ions coupled to transport. Several sites have been proposed for the binding of a third Na+ ion from electrostatic calculations and molecular dynamics simulations. In this study, we have performed detailed free energy simulations for GltPh and reveal a new site for the third Na+ ion involving the side chains of Threonine 92, Serine 93, Asparagine 310, Aspartate 312, and the backbone of Tyrosine 89. We have also studied the transport properties of alanine mutants of the coordinating residues Threonine 92 and Serine 93 in GltPh, and the corresponding residues in a human glutamate transporter, EAAT1. The mutant transporters have reduced affinity for Na+ compared to their wild type counterparts. These results confirm that Threonine 92 and Serine 93 are involved in the coordination of the third Na+ ion in GltPh and EAAT1. PMID:22427946

  10. Flow-induced prostaglandin E2 release regulates Na and K transport in the collecting duct.

    PubMed

    Flores, Daniel; Liu, Yu; Liu, Wen; Satlin, Lisa M; Rohatgi, Rajeev

    2012-09-01

    Fluid shear stress (FSS) is a critical regulator of cation transport in the collecting duct (CD). High-dietary sodium (Na) consumption increases urine flow, Na excretion, and prostaglandin E(2) (PGE(2)) excretion. We hypothesize that increases in FSS elicited by increasing tubular flow rate induce the release of PGE(2) from renal epithelial cells into the extracellular compartment and regulate ion transport. Media retrieved from CD cells exposed to physiologic levels of FSS reveal several fold higher concentration of PGE(2) compared with static controls. Treatment of CD cells with either cyclooxygenase-1 (COX-1) or COX-2 inhibitors during exposure to FSS limited the increase in PGE(2) concentration to an equal extent, suggesting COX-1 and COX-2 contribute equally to FSS-induced PGE(2) release. Cytosolic phospholipase A2 (cPLA2), the principal enzyme that generates the COX substrate arachidonic acid, is regulated by mitogen-activated protein-kinase-dependent phosphorylation and intracellular Ca(2+) concentration ([Ca(2+)](i)), both signaling processes, of which, are activated by FSS. Inhibition of the ERK and p38 pathways reduced PGE(2) release by 53.3 ± 8.4 and 32.6 ± 11.3%, respectively, while antagonizing the JNK pathway had no effect. In addition, chelation of [Ca(2+)](i) limited the FSS-mediated increase in PGE(2) concentration by 47.5 ± 7.5% of that observed in untreated sheared cells. Sheared cells expressed greater phospho-cPLA2 protein abundance than static cells; however, COX-2 protein expression was unaffected (P = 0.064) by FSS. In microperfused CDs, COX inhibition enhanced flow-stimulated Na reabsorption and abolished flow-stimulated potassium (K) secretion, but did not affect ion transport at a slow flow rate, implicating that high tubular flow activates autocrine/paracrine PGE(2) release and, in turn, regulates flow-stimulated cation transport. In conclusion, FSS activates cPLA2 to generate PGE(2) that regulates flow-mediated Na and K transport in

  11. Hepatic taurine transport: a Na/sup +/-dependent carrier on the basolateral plasma membrane

    SciTech Connect

    Bucuvalas, J.C.; Goodrich, A.L.; Suchy, F.J.

    1987-09-01

    Highly purified rat basolateral liver plasma membrane vesicles were used examine the mechanism and the driving forces for hepatic uptake of the ..beta..-amino acid, taurine. An inwardly directed 100 mM NaCl gradient stimulated the initial rate of taurine uptake and energized a transient twofold accumulation of taurine above equilibrium (overshoot). In contrast, uptake was slower and no overshoot was detected in the presence of a KCl gradient. A negative intravesicular electrical potential generated by the presence of permeant anions or an outwardly directed K/sup +/ gradient with valinomycin increased Na/sup +/-stimulated taurine uptake. External Cl/sup -/ stimulated Na/sup +/-dependent taurine uptake independent of effects on the transmembrane electrical potential difference. Na/sup +/-dependent taurine uptake showed a sigmoidal dependence on extravesicular Na/sup +/ concentration, suggesting multiple Na/sup +/ ions are involved in the translocation of each taurine molecule. Na/sup +/-dependent taurine uptake demonstrated Michaelis-Menten kinetics with a maximum velocity of 0.537 nmol x mg protein/sup -1/ x min/sup -1/ and an apparent K/sub m/ of 174 ..mu..M. (/sup 3/H)taurine uptake was inhibited by the presence of excess unlabeled taurine, ..beta..-alanine, or hypotaurine but not by L-glutamine or L-alanine. In summary, using basolateral liver plasma membrane vesicles, the authors have shown that hepatic uptake of taurine occurs by a carrier-mediated, secondary active transport process specific for ..beta..-amino acids. Uptake is electrogenic, stimulated by external Cl/sup -/, and requires multiple Na/sup +/ ions for the translocation of each taurine molecule.

  12. Lack of effect of peritubular protein on passive NaCl transport in the rabbit proximal tubule.

    PubMed Central

    Berry, C A

    1983-01-01

    The effect of peritubular protein removal on passive NaCl transport was examined in the isolated rabbit proximal convoluted tubule (PCT). Three modes of passive NaCl transport were tested: (a) paracellular backflux of NaCl, (b) convective flow of NaCl through junctional complexes, and (c) anion gradient-dependent NaCl transport. The effect of peritubular protein removal on the paracellular permeability to NaCl was examined using transepithelial specific resistance. Eight PCT were perfused with ultrafiltrate (UF) and bathed in either serum or UF. Transepithelial specific resistance averaged 14.5 +/- 1.9 in the presence and 13.7 +/- 1.7 omega cm2 in the absence of peritubular protein. The effect of peritubular protein removal on the convective flow of a NaCl solution across functional complexes was examined in the absence of active transport by using colloid osmotic pressure (COP) gradients. 12 PCT were perfused with simple salt solutions in Donnan equilibrium with and without protein at 20 degrees C. A COP gradient of 60.1 and -60.1 mmHg drove only 0.06 and -0.23 nl/min, respectively. These values are approximately 10% of the value predicted for an effect of peritubular protein on NaCl solution flow (1.98 nl/min) and are approximately equal to the value predicted for pure water equilibration for the small osmotic pressure difference between solutions in Donnan equilibrium (0.17-0.18 nl/min). The effect of peritubular protein removal on the passive absorption of NaCl driven by anion concentration gradients was examined in seven PCT perfused with a high chloride solution simulating late proximal tubular fluid and bathed in either serum or UF at 20 degrees C. Volume absorption averaged 0.34 +/- 0.20 in the presence and 0.39 +/- 0.20 nl/mm min in the absence of peritubular protein. In conclusion, peritubular protein removal did not significantly affect any of the three distinct modes of passive NaCl transport tested. The lack of effect of peritubular protein removal on

  13. Determinants of substrate and cation transport in the human Na+/dicarboxylate cotransporter NaDC3.

    PubMed

    Schlessinger, Avner; Sun, Nina N; Colas, Claire; Pajor, Ana M

    2014-06-13

    Metabolic intermediates, such as succinate and citrate, regulate important processes ranging from energy metabolism to fatty acid synthesis. Cytosolic concentrations of these metabolites are controlled, in part, by members of the SLC13 gene family. The molecular mechanism underlying Na(+)-coupled di- and tricarboxylate transport by this family is understood poorly. The human Na(+)/dicarboxylate cotransporter NaDC3 (SLC13A3) is found in various tissues, including the kidney, liver, and brain. In addition to citric acid cycle intermediates such as α-ketoglutarate and succinate, NaDC3 transports other compounds into cells, including N-acetyl aspartate, mercaptosuccinate, and glutathione, in keeping with its dual roles in cell nutrition and detoxification. In this study, we construct a homology structural model of NaDC3 on the basis of the structure of the Vibrio cholerae homolog vcINDY. Our computations are followed by experimental testing of the predicted NaDC3 structure and mode of interaction with various substrates. The results of this study show that the substrate and cation binding domains of NaDC3 are composed of residues in the opposing hairpin loops and unwound portions of adjacent helices. Furthermore, these results provide a possible explanation for the differential substrate specificity among dicarboxylate transporters that underpin their diverse biological roles in metabolism and detoxification. The structural model of NaDC3 provides a framework for understanding substrate selectivity and the Na(+)-coupled anion transport mechanism by the human SLC13 family and other key solute carrier transporters.

  14. Transport of K+ by Na(+)-Ca2+, K+ exchanger in isolated rods of lizard retina.

    PubMed Central

    Rispoli, G; Navangione, A; Vellani, V

    1995-01-01

    Transport of K+ by the photoreceptor Na(+)-Ca2+, K+ exchanger was investigated in isolated rod outer segments (OS) by recording membrane current under whole-cell voltage-clamp conditions. Known amounts of K+ were imported in the OS through the Ca(2+)-activated K+ channels while perfusing with high extracellular concentration of K+, [K+]o. These channels were detected in the recordings from the OS, which probably retained a small portion of the rest of the cell. The activation of forward exchange (Na+ imported per Ca2+ and K+ extruded) by intracellular K+, Ki+, was described by first-order kinetics with a Michaelis constant, Kapp(Ki+), of about 2 mM and a maximal current, Imax, of about -60 pA. [Na+]i larger than 100 mM had little effect on Kapp(Ki+) and Imax, indicating that Nai+ did not compete with Ki+ for exchange sites under physiological conditions, and that Na+ release at the exchanger intracellular side was not a rate-limiting step for the exchange process. Exchanger stoichiometry resulted in one K+ ion extruded per one positive charge imported. Exchange current was detected only if Ca2+ and K+ were present on the same membrane side, and Na+ was simultaneously present on the opposite side. Nonelectrogenic modes of ion exchange were tested taking advantage of the hindered diffusion found for Cai2+ and Ki+. Experiments were carried out so that the occurrence of a putative nonelectrogenic ion exchange, supposedly induced by the preapplication of certain extracellular ion(s), would have resulted in the transient presence of both Cai2+ and Ki+. The lack of electrogenic forward exchange in a subsequent switch to high Nao+, excluded the presence of previous nonelectrogenic transport. Images FIGURE 1 PMID:7669912

  15. Characteristics of injury and recovery of net NO3- transport of barley seedlings from treatments of NaCl

    NASA Technical Reports Server (NTRS)

    Klobus, G.; Ward, M. R.; Huffaker, R. C.

    1988-01-01

    The nature of the injury and recovery of nitrate uptake (net uptake) from NaCl stress in young barley (Hordeum vulgare L, var CM 72) seedlings was investigated. Nitrate uptake was inhibited rapidly by NaCl, within 1 minute after exposure to 200 millimolar NaCl. The duration of exposure to saline conditions determined the time of recovery of NO3- uptake from NaCl stress. Recovery was dependent on the presence of NO3- and was inhibited by cycloheximide, 6-methylpurine, and cerulenin, respective inhibitors of protein, RNA, and sterol/fatty acid synthesis. These inhibitors also prevented the induction of the NO3- uptake system in uninduced seedlings. Uninduced seedlings exhibited endogenous NO3- transport activity that appeared to be constitutive. This constitutive activity was also inhibited by NaCl. Recovery of constitutive NO3- uptake did not require the presence of NO3-.

  16. Identification of a 3rd Na+ Binding Site of the Glycine Transporter, GlyT2

    PubMed Central

    Subramanian, Nandhitha; Scopelitti, Amanda J.; Carland, Jane E.; Ryan, Renae M.; O’Mara, Megan L.; Vandenberg, Robert J.

    2016-01-01

    The Na+/Cl- dependent glycine transporters GlyT1 and GlyT2 regulate synaptic glycine concentrations. Glycine transport by GlyT2 is coupled to the co-transport of three Na+ ions, whereas transport by GlyT1 is coupled to the co-transport of only two Na+ ions. These differences in ion-flux coupling determine their respective concentrating capacities and have a direct bearing on their functional roles in synaptic transmission. The crystal structures of the closely related bacterial Na+-dependent leucine transporter, LeuTAa, and the Drosophila dopamine transporter, dDAT, have allowed prediction of two Na+ binding sites in GlyT2, but the physical location of the third Na+ site in GlyT2 is unknown. A bacterial betaine transporter, BetP, has also been crystallized and shows structural similarity to LeuTAa. Although betaine transport by BetP is coupled to the co-transport of two Na+ ions, the first Na+ site is not conserved between BetP and LeuTAa, the so called Na1' site. We hypothesized that the third Na+ binding site (Na3 site) of GlyT2 corresponds to the BetP Na1' binding site. To identify the Na3 binding site of GlyT2, we performed molecular dynamics (MD) simulations. Surprisingly, a Na+ placed at the location consistent with the Na1' site of BetP spontaneously dissociated from its initial location and bound instead to a novel Na3 site. Using a combination of MD simulations of a comparative model of GlyT2 together with an analysis of the functional properties of wild type and mutant GlyTs we have identified an electrostatically favorable novel third Na+ binding site in GlyT2 formed by Trp263 and Met276 in TM3, Ala481 in TM6 and Glu648 in TM10. PMID:27337045

  17. Intestinal ammonia transport in freshwater and seawater acclimated rainbow trout (Oncorhynchus mykiss): evidence for a Na+ coupled uptake mechanism.

    PubMed

    Rubino, Julian G; Zimmer, Alex M; Wood, Chris M

    2015-05-01

    In vitro gut sac experiments were performed on freshwater and 60% seawater acclimated trout (Oncorhynchus mykiss) under treatments designed to discern possible mechanisms of intestinal ammonia transport. Seawater acclimation increased ammonia flux rate into the serosal saline (Jsamm) in the anterior intestine, however it did not alter Jsamm in the mid- or posterior intestine suggesting similar mechanisms of ammonia handling in freshwater and seawater fish. Both fluid transport rate (FTR) and Jsamm were inhibited in response to basolateral ouabain treatment, suggesting a linkage of ammonia uptake to active transport, possibly coupled to fluid transport processes via solvent drag. Furthermore, decreases in FTR and Jsamm caused by low Na(+) treatment indicated a Na(+) linked transport mechanism. Mucosal bumetanide (10(-4) M) had no impact on FTR, yet decreased Jsamm in the anterior and mid-intestine, suggesting NH4(+) substitution for K(+) on an apical NKCC, and at least a partial uncoupling of ammonia transport from fluid transport. Additional treatments (amiloride, 5-(N-ethyl-N-isopropyl)amiloride (EIPA), phenamil, bafilomycin, 4',6-diamidino-2-phenylindole (DAPI), high sodium) intended to disrupt alternative routes of Na(+) uptake yielded no change in FTR or Jsamm, suggesting the absence of direct competition between Na(+) and ammonia for transport. Finally, [(14)C]methylamine permeability (PMA) measurements indicated the likely presence of an intestinal Rh-mediated ammonia transport system, as increasing NH4Cl (0, 1, 5 mmol l(-1)) concentrations reduced PMA, suggesting competition for transport through Rh proteins. Overall, the data presented in this paper provide some of the first insights into mechanisms of teleost intestinal ammonia transport.

  18. Transport of H(+), Na(+) and K(+) across the posterior midgut of blood-fed mosquitoes (Aedes aegypti).

    PubMed

    Pacey, Evan K; O'Donnell, Michael J

    2014-02-01

    Following ingestion of a blood meal, the adult female mosquito undergoes a massive diuresis during which Na(+), Cl(-) and water are secreted at high rates by the Malpighian tubules. In the hours following completion of diuresis, digestion of the K(+)-rich blood cells provides a source of energy as well as amino acids for proteins in the developing eggs. Although the transport of inorganic ions by the Malpighian tubules of blood-fed mosquitoes has been extensively characterized, relatively little is known of the epithelial transport mechanisms responsible for movement of Na(+), H(+), and K(+) across the posterior midgut. In this paper we have used the Scanning Ion-selective Electrode Technique (SIET) to measure the basal (unstimulated) rates of transport of K(+), Na(+) and H(+) across the isolated posterior midgut at intervals after the blood meal. We have also measured luminal concentrations of Na(+) and K(+) and the transepithelial electrical potential at the same time points and have calculated the electrochemical potentials for Na(+), K(+) and H(+) across the midgut. SIET measurements reveal absorption (lumen to bath) of Na(+) and H(+) and secretion of K(+) for the first 2h after blood-feeding. By 24h after the meal, absorption of Na(+) and H(+) remains active while there is an electrochemical gradient favouring absorption of K(+). Inhibition by ouabain and Ba(2+) suggest a role for the Na(+)/K(+)-ATPase and K(+) channels in absorption of Na(+) and K(+), respectively. Inhibition of H(+) absorption by acetazolamide implicates carbonic anhydrase in transepithelial H(+) transport.

  19. Thermodynamic and Transport Properties of H2O + NaCl from Polarizable Force Fields.

    PubMed

    Jiang, Hao; Mester, Zoltan; Moultos, Othonas A; Economou, Ioannis G; Panagiotopoulos, Athanassios Z

    2015-08-11

    Molecular dynamics and Monte Carlo simulations were performed to obtain thermodynamic and transport properties of the binary H2O + NaCl system using the polarizable force fields of Kiss and Baranyai ( J. Chem. Phys. 2013 , 138 , 204507 and 2014 , 141 , 114501 ). In particular, liquid densities, electrolyte and crystal chemical potentials of NaCl, salt solubilities, mean ionic activity coefficients, vapor pressures, vapor-liquid interfacial tensions, and viscosities were obtained as functions of temperature, pressure, and salt concentration. We compared the performance of the polarizable force fields against fixed-point-charge (nonpolarizable) models. Most of the properties of interest are better represented by the polarizable models, which also remain physically realistic at elevated temperatures. PMID:26574461

  20. Distribution of organic anion transporters NaDC3 and OAT1-3 along the human nephron.

    PubMed

    Breljak, Davorka; Ljubojević, Marija; Hagos, Yohannes; Micek, Vedran; Balen Eror, Daniela; Vrhovac Madunić, Ivana; Brzica, Hrvoje; Karaica, Dean; Radović, Nikola; Kraus, Ognjen; Anzai, Naohiko; Koepsell, Hermann; Burckhardt, Gerhard; Burckhardt, Birgitta C; Sabolić, Ivan

    2016-07-01

    The initial step in renal secretion of organic anions (OAs) is mediated by transporters in the basolateral membrane (BLM). Contributors to this process are primary active Na(+)-K(+)-ATPase (EC 3.6.3.9), secondary active Na(+)-dicarboxylate cotransporter 3 (NaDC3/SLC13A3), and tertiary active OA transporters (OATs) OAT1/SLC22A6, OAT2/SLC22A7, and OAT3/SLC22A8. In human kidneys, we analyzed the localization of these transporters by immunochemical methods in tissue cryosections and isolated membranes. The specificity of antibodies was validated with human embryonic kidney-293 cells stably transfected with functional OATs. Na(+)-K(+)-ATPase was immunolocalized to the BLM along the entire human nephron. NaDC3-related immunostaining was detected in the BLM of proximal tubules and in the BLM and/or luminal membrane of principal cells in connecting segments and collecting ducts. The thin and thick ascending limbs, macula densa, and distal tubules exhibited no reactivity with the anti-NaDC3 antibody. OAT1-OAT3-related immunostaining in human kidneys was detected only in the BLM of cortical proximal tubules; all three OATs were stained more intensely in S1/S2 segments compared with S3 segment in medullary rays, whereas the S3 segment in the outer stripe remained unstained. Expression of NaDC3, OAT1, OAT2, and OAT3 proteins exhibited considerable interindividual variability in both male and female kidneys, and sex differences in their expression could not be detected. Our experiments provide a side-by-side comparison of basolateral transporters cooperating in renal OA secretion in the human kidney. PMID:27053689

  1. Functional characterization of a Na(+)-coupled dicarboxylate transporter from Bacillus licheniformis.

    PubMed

    Strickler, Melodie A; Hall, Jason A; Gaiko, Olga; Pajor, Ana M

    2009-12-01

    The Na(+)-coupled dicarboxylate transporter, SdcL, from Bacillus licheniformis is a member of the divalent anion/Na(+) symporter (DASS) family that includes the bacterial Na(+)/dicarboxylate cotransporter SdcS (from Staphyloccocus aureus) and the mammalian Na(+)/dicarboxylate cotransporters, NaDC1 and NaDC3. The transport properties of SdcL produced in Escherichia coli are similar to those of its prokaryotic and eukaryotic counterparts, involving the Na(+)-dependent transport of dicarboxylates such as succinate or malate across the cytoplasmic membrane with a K(m) of approximately 6 microM. SdcL may also transport aspartate, alpha-ketoglutarate and oxaloacetate with low affinity. The cotransport of Na(+) and dicarboxylate by SdcL has an apparent stoichiometry of 2:1, and a K(0.5) for Na(+) of 0.9 mM. Our findings represent the characterization of another prokaryotic protein of the DASS family with transport properties similar to its eukaryotic counterparts, but with a broader substrate specificity than other prokaryotic DASS family members. The broader range of substrates carried by SdcL may provide insight into domains of the protein that allow a more flexible or larger substrate binding pocket.

  2. Transepithelial glucose transport and Na+/K+ homeostasis in enterocytes: an integrative model.

    PubMed

    Thorsen, Kristian; Drengstig, Tormod; Ruoff, Peter

    2014-08-15

    The uptake of glucose and the nutrient coupled transcellular sodium traffic across epithelial cells in the small intestine has been an ongoing topic in physiological research for over half a century. Driving the uptake of nutrients like glucose, enterocytes must have regulatory mechanisms that respond to the considerable changes in the inflow of sodium during absorption. The Na-K-ATPase membrane protein plays a major role in this regulation. We propose the hypothesis that the amount of active Na-K-ATPase in enterocytes is directly regulated by the concentration of intracellular Na(+) and that this regulation together with a regulation of basolateral K permeability by intracellular ATP gives the enterocyte the ability to maintain ionic Na(+)/K(+) homeostasis. To explore these regulatory mechanisms, we present a mathematical model of the sodium coupled uptake of glucose in epithelial enterocytes. Our model integrates knowledge about individual transporter proteins including apical SGLT1, basolateral Na-K-ATPase, and GLUT2, together with diffusion and membrane potentials. The intracellular concentrations of glucose, sodium, potassium, and chloride are modeled by nonlinear differential equations, and molecular flows are calculated based on experimental kinetic data from the literature, including substrate saturation, product inhibition, and modulation by membrane potential. Simulation results of the model without the addition of regulatory mechanisms fit well with published short-term observations, including cell depolarization and increased concentration of intracellular glucose and sodium during increased concentration of luminal glucose/sodium. Adding regulatory mechanisms for regulation of Na-K-ATPase and K permeability to the model show that our hypothesis predicts observed long-term ionic homeostasis.

  3. Fluid dilution and efficiency of Na(+) transport in a mathematical model of a thick ascending limb cell.

    PubMed

    Nieves-González, Aniel; Clausen, Chris; Marcano, Mariano; Layton, Anita T; Layton, Harold E; Moore, Leon C

    2013-03-15

    Thick ascending limb (TAL) cells are capable of reducing tubular fluid Na(+) concentration to as low as ~25 mM, and yet they are thought to transport Na(+) efficiently owing to passive paracellular Na(+) absorption. Transport efficiency in the TAL is of particular importance in the outer medulla where O(2) availability is limited by low blood flow. We used a mathematical model of a TAL cell to estimate the efficiency of Na(+) transport and to examine how tubular dilution and cell volume regulation influence transport efficiency. The TAL cell model represents 13 major solutes and the associated transporters and channels; model equations are based on mass conservation and electroneutrality constraints. We analyzed TAL transport in cells with conditions relevant to the inner stripe of the outer medulla, the cortico-medullary junction, and the distal cortical TAL. At each location Na(+) transport efficiency was computed as functions of changes in luminal NaCl concentration ([NaCl]), [K(+)], [NH(4)(+)], junctional Na(+) permeability, and apical K(+) permeability. Na(+) transport efficiency was calculated as the ratio of total net Na(+) transport to transcellular Na(+) transport. Transport efficiency is predicted to be highest at the cortico-medullary boundary where the transepithelial Na(+) gradient is the smallest. Transport efficiency is lowest in the cortex where luminal [NaCl] approaches static head.

  4. Thyroid thermogenesis. Relationships between Na+-dependent respiration and Na+ + K+-adenosine triphosphatase activity in rat skeletal muscle.

    PubMed Central

    Asano, Y; Liberman, U A; Edelman, I S

    1976-01-01

    The effect of thyroid status on QO2, QO2 (t) and NaK-ATPase activity was examined in rat skeletal muscle. QO2(t) (i.e. Na+-transport-dependent respiration) was estimated with ouabain or Na+-free media supplemented with K+. In contrast to the effects of ouabain on ion composition, intracellular K+ was maintained at about 125 meq/liter, and intracellular Na+ was almost nil in the Na+-free media. The estimates of QO2(t) were independent of the considerable differences in tissue ion concentrations. The increase in QO2(t) account for 47% of the increase in QO2 in the transition from the hypothyroid to the euthyroid state and 84% of the increase in the transition from the euthyroid to the hyperthyroid state. Surgical thyroidectomy lowered NaK-ATPase activity of the microsomal fraction (expressed per milligram protein) 32%; injections of triodothyronine (T3) increased this activity 75% in initially hypothyroid rats and 26% in initially euthyroid rats. Thyroidectomy was attended by significant falls in serum Ca and Pi concentrations. Administration of T3 resulted in further declines in serum Ca and marked increases in serum Ps concentrations. Similar effects were seen in 131I-treated rats, but the magnitude of the declines in serum Ca were less. The effects of T3 on QO2, QO2(t), and NaK-ATPase activity of skeletal muscle were indistinguishable in the 131I-ablated and surgically thyroidectomized rats. In thyroidectomized or euthyroid rats given repeated doses of T3, QO2(t) and NaA-ATPase activity increased proportionately. In thyroidectomized rats injected with single doses of T3, either 10, 50, or 250 mug/100 g body wt, QO2(t) increased linearly with NaK-ATPase activity. The kinetics of the NaK-ATPase activity was assessed with an ATP-generating system. T3 elicited a significant increase in Vmax with no change in Km for ATP. PMID:130385

  5. Increased vacuolar Na(+)/H(+) exchange activity in Salicornia bigelovii Torr. in response to NaCl.

    PubMed

    Parks, Graham E; Dietrich, Margaret A; Schumaker, Karen S

    2002-05-01

    Shoots of the halophyte Salicornia bigelovii are larger and more succulent when grown in highly saline environments. This increased growth and water uptake has been correlated with a large and specific cellular accumulation of sodium. In glycophytes, sensitivity to salt has been associated with an inability to remove sodium ions effectively from the cytoplasm in order to protect salt-sensitive metabolic processes. Therefore, in Salicornia bigelovii efficient vacuolar sequestration of sodium may be part of the mechanism underlying salt tolerance. The ability to compartmentalize sodium may result from a stimulation of the proton pumps that provide the driving force for increased sodium transport into the vacuole via a Na(+)/H(+) exchanger. In current studies, increased vacuolar pyrophosphatase activity (hydrolysis of inorganic pyrophosphate and proton translocation) and protein accumulation were observed in Salicornia bigelovii grown in high concentrations of NaCl. Based on sodium-induced dissipation of a pyrophosphate-dependent pH gradient in vacuolar membrane vesicles, a Na(+)/H(+) exchange activity was identified and characterized. This activity is sodium concentration-dependent, specific for sodium and lithium, sensitive to methyl-isobutyl amiloride, and independent of an electrical potential. Vacuolar Na(+)/H(+) exchange activity varied as a function of plant growth in salt. The affinity of the transporter for Na(+) is almost three times higher in plants grown in high levels of salt (K(m)=3.8 and 11.5 mM for plants grown in high and low salt, respectively) suggesting a role for exchange activity in the salt adaptation of Salicornia bigelovii. PMID:11971917

  6. Transepithelial Na+ transport and the intracellular fluids: a computer study.

    PubMed

    Civan, M M; Bookman, R J

    1982-01-01

    Computer simulations of tight epithelia under three experimental conditions have been carried out, using the rheogenic nonlinear model of Lew, Ferreira and Moura (Proc. Roy. Soc. London. B 206:53-83, 1979) based largely on the formulation of Koefoed-Johnsen and Ussing (Acta Physiol. Scand. 42: 298-308. 1958). First, analysis of the transition between the short-circuited and open-circuited states has indicated that (i) apical Cl- permeability is a critical parameter requiring experimental definition in order to analyze cell volume regulation, and (ii) contrary to certain experimental reports, intracellular Na+ concentration (ccNa) is expected to be a strong function of transepithelial clamping voltage. Second, analysis of the effects of lowering serosal K+ concentration (csK) indicates that the basic model cannot simulate several well-documented observations; these defects can be overcome, at least qualitatively, by modifying the model to take account of the negative feedback interaction likely to exist between the apical Na+ permeability and ccNa. Third, analysis of the strongly supports the concept that osmotically induced permeability changes in the apical intercellular junctions play a physiological role in conserving the body's stores of NaCl. The analyses also demonstrate that the importance of Na+ entry across the basolateral membrane is strongly dependent upon transepithelial potential, cmNa and csK; under certain conditions, net Na+ entry could be appreciably greater across the basolateral than across the apical membrane.

  7. Renal brush-border Na/sup +/-H/sup +/ exchange activity in the aging rat

    SciTech Connect

    Kinsella, J.L.; Sacktor, B.

    1987-04-01

    Amiloride-sensitive Na/sup +/-H/sup +/ exchange activity in brush-border membrane vesicles isolated from male rat proximal tubules was decreased in the senescent rat (24 mo) compared with the young adult (6 mo). There was no significant loss in Na/sup +/-H/sup +/ exchange activity in the kidneys of animals between 6 and 18 mo of age. Amiloride-insensitive /sup 22/Na/sup +/ uptake and the rate of pH gradient dissipation were not altered during aging. The decrease in sodium-dependent (/sup 32/P) phosphate transport preceded the decline in Na/sup +/-H/sup +/ exchange activity by at least 6 mo. Sodium-dependent D-(/sup 3/H) glucose transport was not significantly altered during aging. Thus various renal plasma membrane transport functions were affected differently in the aging rat. The decrease in Na/sup +/-H/sup +/ exchange activity during aging contrasted with the increase in exchange activity reported previously in acute ablation models of chronic renal failure.

  8. Transport aircraft flying qualities activities

    NASA Technical Reports Server (NTRS)

    Moul, M. T.

    1981-01-01

    The optimal control model for pilot vehicle systems was used to develop a methodology for predicting pilot ratings for commercial transports. The method was tested by applying it to a family of transport configurations for which subjective pilot ratings were obtained. Specific attention is given to the development of the simulator program and procedures so as to yield objective and subjective performance data useful for a critical evaluation of the analytical method.

  9. Expression of the rabbit intestinal N2 Na+/nucleoside transporter in Xenopus laevis oocytes.

    PubMed Central

    Jarvis, S M; Griffith, D A

    1991-01-01

    Polyadenylated [poly(A)+] mRNA isolated from rabbit small-intestinal mucosa was injected into Xenopus laevis oocytes, and expression of the N2 Na+/nucleoside co-transporter was assayed by measuring Na(+)-dependent thymidine uptake. Expression of Na(+)-dependent thymidine uptake steadily increased after mRNA injection and was on average increased 11-fold by day 6 over background. Na(+)-dependent thymidine uptake was saturable (apparent Km approximately 30 microM at 22 degrees C) and inhibited by uridine and cytidine, but not by guanosine and inosine. These properties of the expressed thymidine transport strongly suggest that the epithelial N2 Na+/nucleoside co-transporter can be expressed in X. laevis oocytes. PMID:1898349

  10. The Na(+) transporter, TaHKT1;5-D, limits shoot Na(+) accumulation in bread wheat.

    PubMed

    Byrt, Caitlin Siobhan; Xu, Bo; Krishnan, Mahima; Lightfoot, Damien James; Athman, Asmini; Jacobs, Andrew Keith; Watson-Haigh, Nathan S; Plett, Darren; Munns, Rana; Tester, Mark; Gilliham, Matthew

    2014-11-01

    Bread wheat (Triticum aestivum L.) has a major salt tolerance locus, Kna1, responsible for the maintenance of a high cytosolic K(+) /Na(+) ratio in the leaves of salt stressed plants. The Kna1 locus encompasses a large DNA fragment, the distal 14% of chromosome 4DL. Limited recombination has been observed at this locus making it difficult to map genetically and identify the causal gene. Here, we decipher the function of TaHKT1;5-D, a candidate gene underlying the Kna1 locus. Transport studies using the heterologous expression systems Saccharomyces cerevisiae and Xenopus laevis oocytes indicated that TaHKT1;5-D is a Na(+) -selective transporter. Transient expression in Arabidopsis thaliana mesophyll protoplasts and in situ polymerase chain reaction indicated that TaHKT1;5-D is localised on the plasma membrane in the wheat root stele. RNA interference-induced silencing decreased the expression of TaHKT1;5-D in transgenic bread wheat lines which led to an increase in the Na(+) concentration in the leaves. This indicates that TaHKT1;5-D retrieves Na(+) from the xylem vessels in the root and has an important role in restricting the transport of Na(+) from the root to the leaves in bread wheat. Thus, TaHKT1;5-D confers the essential salinity tolerance mechanism in bread wheat associated with the Kna1 locus via shoot Na(+) exclusion and is critical in maintaining a high K(+) /Na(+) ratio in the leaves. These findings show there is potential to increase the salinity tolerance of bread wheat by manipulation of HKT1;5 genes. PMID:25158883

  11. The Na(+) transporter, TaHKT1;5-D, limits shoot Na(+) accumulation in bread wheat.

    PubMed

    Byrt, Caitlin Siobhan; Xu, Bo; Krishnan, Mahima; Lightfoot, Damien James; Athman, Asmini; Jacobs, Andrew Keith; Watson-Haigh, Nathan S; Plett, Darren; Munns, Rana; Tester, Mark; Gilliham, Matthew

    2014-11-01

    Bread wheat (Triticum aestivum L.) has a major salt tolerance locus, Kna1, responsible for the maintenance of a high cytosolic K(+) /Na(+) ratio in the leaves of salt stressed plants. The Kna1 locus encompasses a large DNA fragment, the distal 14% of chromosome 4DL. Limited recombination has been observed at this locus making it difficult to map genetically and identify the causal gene. Here, we decipher the function of TaHKT1;5-D, a candidate gene underlying the Kna1 locus. Transport studies using the heterologous expression systems Saccharomyces cerevisiae and Xenopus laevis oocytes indicated that TaHKT1;5-D is a Na(+) -selective transporter. Transient expression in Arabidopsis thaliana mesophyll protoplasts and in situ polymerase chain reaction indicated that TaHKT1;5-D is localised on the plasma membrane in the wheat root stele. RNA interference-induced silencing decreased the expression of TaHKT1;5-D in transgenic bread wheat lines which led to an increase in the Na(+) concentration in the leaves. This indicates that TaHKT1;5-D retrieves Na(+) from the xylem vessels in the root and has an important role in restricting the transport of Na(+) from the root to the leaves in bread wheat. Thus, TaHKT1;5-D confers the essential salinity tolerance mechanism in bread wheat associated with the Kna1 locus via shoot Na(+) exclusion and is critical in maintaining a high K(+) /Na(+) ratio in the leaves. These findings show there is potential to increase the salinity tolerance of bread wheat by manipulation of HKT1;5 genes.

  12. A Barley Efflux Transporter Operates in a Na+-Dependent Manner, as Revealed by a Multidisciplinary Platform.

    PubMed

    Nagarajan, Yagnesh; Rongala, Jay; Luang, Sukanya; Singh, Abhishek; Shadiac, Nadim; Hayes, Julie; Sutton, Tim; Gilliham, Matthew; Tyerman, Stephen D; McPhee, Gordon; Voelcker, Nicolas H; Mertens, Haydyn D T; Kirby, Nigel M; Lee, Jung-Goo; Yingling, Yaroslava G; Hrmova, Maria

    2016-01-01

    Plant growth and survival depend upon the activity of membrane transporters that control the movement and distribution of solutes into, around, and out of plants. Although many plant transporters are known, their intrinsic properties make them difficult to study. In barley (Hordeum vulgare), the root anion-permeable transporter Bot1 plays a key role in tolerance to high soil boron, facilitating the efflux of borate from cells. However, its three-dimensional structure is unavailable and the molecular basis of its permeation function is unknown. Using an integrative platform of computational, biophysical, and biochemical tools as well as molecular biology, electrophysiology, and bioinformatics, we provide insight into the origin of transport function of Bot1. An atomistic model, supported by atomic force microscopy measurements, reveals that the protein folds into 13 transmembrane-spanning and five cytoplasmic α-helices. We predict a trimeric assembly of Bot1 and the presence of a Na(+) ion binding site, located in the proximity of a pore that conducts anions. Patch-clamp electrophysiology of Bot1 detects Na(+)-dependent polyvalent anion transport in a Nernstian manner with channel-like characteristics. Using alanine scanning, molecular dynamics simulations, and transport measurements, we show that conductance by Bot1 is abolished by removal of the Na(+) ion binding site. Our data enhance the understanding of the permeation functions of Bot1. PMID:26672067

  13. A Barley Efflux Transporter Operates in a Na+-Dependent Manner, as Revealed by a Multidisciplinary Platform[OPEN

    PubMed Central

    Nagarajan, Yagnesh; Rongala, Jay; Luang, Sukanya; Shadiac, Nadim; Sutton, Tim; Tyerman, Stephen D.; McPhee, Gordon; Voelcker, Nicolas H.; Lee, Jung-Goo

    2016-01-01

    Plant growth and survival depend upon the activity of membrane transporters that control the movement and distribution of solutes into, around, and out of plants. Although many plant transporters are known, their intrinsic properties make them difficult to study. In barley (Hordeum vulgare), the root anion-permeable transporter Bot1 plays a key role in tolerance to high soil boron, facilitating the efflux of borate from cells. However, its three-dimensional structure is unavailable and the molecular basis of its permeation function is unknown. Using an integrative platform of computational, biophysical, and biochemical tools as well as molecular biology, electrophysiology, and bioinformatics, we provide insight into the origin of transport function of Bot1. An atomistic model, supported by atomic force microscopy measurements, reveals that the protein folds into 13 transmembrane-spanning and five cytoplasmic α-helices. We predict a trimeric assembly of Bot1 and the presence of a Na+ ion binding site, located in the proximity of a pore that conducts anions. Patch-clamp electrophysiology of Bot1 detects Na+-dependent polyvalent anion transport in a Nernstian manner with channel-like characteristics. Using alanine scanning, molecular dynamics simulations, and transport measurements, we show that conductance by Bot1 is abolished by removal of the Na+ ion binding site. Our data enhance the understanding of the permeation functions of Bot1. PMID:26672067

  14. Na+ transport across rumen epithelium of hay-fed sheep is acutely stimulated by the peptide IGF-1 in vitro.

    PubMed

    Shen, Zanming; Martens, Holger; Schweigel-Röntgen, Monika

    2012-04-01

    An energy-rich diet leads to enhanced ruminal Na(+) absorption, which is associated with elevated plasma insulin-like growth factor 1 (IGF-1) levels and an increased number of IGF-1 receptors in rumen papillae. This study examined the in vitro effect of IGF-1 on Na(+) transport across the rumen epithelium of hay-fed sheep, in which the IGF-1 concentration in plasma is lower than in concentrate-fed animals. At concentrations ranging from 20 to 100 μg l(-1), serosal LR3-IGF-1, a recombinant analogue of IGF-1, rapidly (within 30 min) stimulated the mucosal-to-serosal Na(+) flux (J(ms)Na) and consequently the net Na(+) flux (J(net)Na). Compared with controls, J(net)Na increased by about 60% (P < 0.05) following the serosal application of LR3-IGF-1 (20 μg l(-1)). The IGF-1-induced increment of J(ms)Na and J(net)Na was inhibited by mucosal amiloride (1 mmol l(-1)). Neither IGF-1 nor amiloride altered tissue conductance or the short-circuit current of the isolated rumen epithelium. These data support the assumption that the stimulating effect of serosally applied IGF-1 on Na(+) transport across the rumen epithelium is mediated by Na(+)-H(+) exchange (NHE). A further study was performed with cultured rumen epithelial cells and a fluorescent probe (BCECF) to estimate the rate of pH(i) recovery after acid loading. The pH(i) of isolated rumen epithelial cells was 6.43 ± 0.15 after butyrate loading and recovered by 0.26 ± 0.02 pH units (15 min)(-1). Application of LR3-IGF-1 (20 μg l(-1)) significantly increased the rate of pH(i) recovery to 0.33 ± 0.02 pH units (15 min)(-1). Amiloride administration reduced the recovery rate in both control and IGF-1-stimulated cells. These results show, for the first time, that an acute effect of IGF-1 on Na(+) absorption across rumen epithelium results from increased NHE activity. Insulin-like growth factor 1 is thus important for the fast functional adaptation of ruminal Na(+) transport via NHE.

  15. Uptake and Loss of Na+, Rb+, and Cs+ in Relation to an Active Mechanism for Extrusion of Na+ in Scenedesmus 1

    PubMed Central

    Kylin, Anders

    1966-01-01

    The mechanism for extrusion of Na+ from Scenedesmus cells is characterized physiologically. It is stimulated by phosphate but oxygen is not necessary. Rb+ and Cs+ may also be extruded, but in the presence of Na+ they cannot compete for the sites on the inside of the transport system. When Na+ is extruded, Rb+ and, by inference, K+ seems to be transported as counter ion from the outside, and sodium ions compete only weakly for this external site. The parallelism between these findings and the Na+-K+-activated adenosine triphosphatases known from animal tissues is pointed out. With low additions of phosphate, the extrusion mechanism can keep the cells practically free from Na+. Increasing the concentrations of external phosphate stimulates uptake more than extrusion, and a net uptake occurs. As for Rb+ and Cs+, they are taken up in the absence of external phosphate, but additions of P will greatly enhance the amounts absorbed. Two different ways of uptake are indicated. PMID:5932402

  16. Protection of plasma membrane K+ transport by the salt overly sensitive1 Na+-H+ antiporter during salinity stress.

    PubMed

    Qi, Zhi; Spalding, Edgar P

    2004-09-01

    Physicochemical similarities between K(+) and Na(+) result in interactions between their homeostatic mechanisms. The physiological interactions between these two ions was investigated by examining aspects of K(+) nutrition in the Arabidopsis salt overly sensitive (sos) mutants, and salt sensitivity in the K(+) transport mutants akt1 (Arabidopsis K(+) transporter) and skor (shaker-like K(+) outward-rectifying channel). The K(+)-uptake ability (membrane permeability) of the sos mutant root cells measured electrophysiologically was normal in control conditions. Also, growth rates of these mutants in Na(+)-free media displayed wild-type K(+) dependence. However, mild salt stress (50 mm NaCl) strongly inhibited root-cell K(+) permeability and growth rate in K(+)-limiting conditions of sos1 but not wild-type plants. Increasing K(+) availability partially rescued the sos1 growth phenotype. Therefore, it appears that in the presence of Na(+), the SOS1 Na(+)-H(+) antiporter is necessary for protecting the K(+) permeability on which growth depends. The hypothesis that the elevated cytoplasmic Na(+) levels predicted to result from loss of SOS1 function impaired the K(+) permeability was tested by introducing 10 mm NaCl into the cytoplasm of a patch-clamped wild-type root cell. Complete loss of AKT1 K(+) channel activity ensued. AKT1 is apparently a target of salt stress in sos1 plants, resulting in poor growth due to impaired K(+) uptake. Complementary studies showed that akt1 seedlings were salt sensitive during early seedling development, but skor seedlings were normal. Thus, the effect of Na(+) on K(+) transport is probably more important at the uptake stage than at the xylem loading stage.

  17. Nax loci affect SOS1-like Na+/H+ exchanger expression and activity in wheat

    PubMed Central

    Zhu, Min; Shabala, Lana; Cuin, Tracey A; Huang, Xin; Zhou, Meixue; Munns, Rana; Shabala, Sergey

    2016-01-01

    Salinity stress tolerance in durum wheat is strongly associated with a plant’s ability to control Na+ delivery to the shoot. Two loci, termed Nax1 and Nax2, were recently identified as being critical for this process and the sodium transporters HKT1;4 and HKT1;5 were identified as the respective candidate genes. These transporters retrieve Na+ from the xylem, thus limiting the rates of Na+ transport from the root to the shoot. In this work, we show that the Nax loci also affect activity and expression levels of the SOS1-like Na+/H+ exchanger in both root cortical and stelar tissues. Net Na+ efflux measured in isolated steles from salt-treated plants, using the non-invasive ion flux measuring MIFE technique, decreased in the sequence: Tamaroi (parental line)>Nax1=Nax2>Nax1:Nax2 lines. This efflux was sensitive to amiloride (a known inhibitor of the Na+/H+ exchanger) and was mirrored by net H+ flux changes. TdSOS1 relative transcript levels were 6–10-fold lower in Nax lines compared with Tamaroi. Thus, it appears that Nax loci confer two highly complementary mechanisms, both of which contribute towards reducing the xylem Na+ content. One enhances the retrieval of Na+ back into the root stele via HKT1;4 or HKT1;5, whilst the other reduces the rate of Na+ loading into the xylem via SOS1. It is suggested that such duality plays an important adaptive role with greater versatility for responding to a changing environment and controlling Na+ delivery to the shoot. PMID:26585227

  18. Identification of functionally distinct Na-HCO3 co-transporters in colon.

    PubMed

    Barmeyer, Christian; Ye, Jeff Huaqing; Soroka, Carol; Geibel, Peter; Hingsammer, Lukas M; Weitgasser, Laurence; Atway, Danny; Geibel, John P; Binder, Henry J; Rajendran, Vazhaikkurichi M

    2013-01-01

    Na-HCO3 cotransport (NBC) regulates intracellular pH (pHi) and HCO3 secretion in rat colon. NBC has been characterized as a 5,5'-diisothiocyanato-2-2'-stilbene (DIDS)-sensitive transporter in several tissues, while the colonic NBC is sensitive to both amiloride and DIDS. In addition, the colonic NBC has been identified as critical for pHi regulation as it is activated by intravesicular acid pH. Molecular studies have identified several characteristically distinct NBC isoforms [i.e. electrogenic (NBCe) and electroneutral (NBCn)] that exhibit tissue specific expression. This study was initiated to establish the molecular identity and specific function of NBC isoforms in rat colon. Northern blot and reverse transcriptase PCR (RT-PCR) analyses revealed that electrogenic NBCe1B or NBCe1C (NBCe1B/C) isoform is predominantly expressed in proximal colon, while electroneutral NBCn1C or NBCn1D (NBCn1C/D) is expressed in both proximal and distal colon. Functional analyses revealed that amiloride-insensitive, electrogenic, pH gradient-dependent NBC activity is present only in basolateral membranes of proximal colon. In contrast, amiloride-sensitive, electroneutral, [H(+)]-dependent NBC activity is present in both proximal and distal colon. Both electrogenic and electroneutral NBC activities are saturable processes with an apparent Km for Na of 7.3 and 4.3 mM, respectively; and are DIDS-sensitive with apparent Ki of 8.9 and 263.8 µM, respectively. In addition to Na-H exchanger isoform-1 (NHE1), pHi acidification is regulated by a HCO3-dependent mechanism that is HOE694-insensitive in colonic crypt glands. We conclude from these data that electroneutral, amiloride-sensitive NBC is encoded by NBCn1C/D and is present in both proximal and distal colon, while NBCe1B/C encodes electrogenic, amiloride-insensitive Na-HCO3 cotransport in proximal colon. We also conclude that NBCn1C/D regulates HCO3-dependent HOE694-insensitive Na-HCO3 cotransport and plays a critical role in p

  19. Modulation Effects of Curcumin on Erythrocyte Ion-Transporter Activity

    PubMed Central

    Singh, Prabhakar; Rizvi, Syed Ibrahim

    2015-01-01

    Curcumin ((1E,6E)-1,7-Bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione), the yellow biphenolic pigment isolated from turmeric (Curcuma longa), has various medicinal benefits through antioxidation, anti-inflammation, cardiovascular protection, immunomodulation, enhancing of the apoptotic process, and antiangiogenic property. We explored the effects of curcumin in vitro (10−5 M to 10−8 M) and in vivo (340 and 170 mg/kg b.w., oral) on Na+/K+ ATPase (NKA), Na+/H+ exchanger (NHE) activity, and membrane lipid hydroperoxides (ROOH) in control and experimental oxidative stress erythrocytes of Wistar rats. As a result, we found that curcumin potently modulated the membrane transporters activity with protecting membrane lipids against hydro-peroxidation in control as well as oxidatively challenged erythrocytes evidenced by stimulation of NKA, downregulation of NHE, and reduction of ROOH in the membrane. The observed results corroborate membrane transporters activity with susceptibility of erythrocyte membrane towards oxidative damage. Results explain the protective mechanism of curcumin against oxidative stress mediated impairment in ions-transporters activity and health beneficial effects. PMID:26421014

  20. The transport properties of activated carbon fibers

    SciTech Connect

    di Vittorio, S.L. . Dept. of Materials Science and Engineering); Dresselhaus, M.S. . Dept. of Electrical Engineering and Computer Science Massachusetts Inst. of Tech., Cambridge, MA . Dept. of Physics); Endo, M. . Dept. of Electrical Engineering); Issi, J-P.; Piraux, L.

    1990-07-01

    The transport properties of activated isotropic pitch-based carbon fibers with surface area 1000 m{sup 2}/g have been investigated. We report preliminary results on the electrical conductivity, the magnetoresistance, the thermal conductivity and the thermopower of these fibers as a function of temperature. Comparisons are made to transport properties of other disordered carbons. 19 refs., 4 figs.

  1. The Transport Properties of Activated Carbon Fibers

    DOE R&D Accomplishments Database

    di Vittorio, S. L.; Dresselhaus, M. S.; Endo, M.; Issi, J-P.; Piraux, L.

    1990-07-01

    The transport properties of activated isotropic pitch-based carbon fibers with surface area 1000 m{sup 2}/g have been investigated. We report preliminary results on the electrical conductivity, the magnetoresistance, the thermal conductivity and the thermopower of these fibers as a function of temperature. Comparisons are made to transport properties of other disordered carbons.

  2. Ouabain Regulates CFTR-Mediated Anion Secretion and Na,K-ATPase Transport in ADPKD Cells.

    PubMed

    Jansson, Kyle; Venugopal, Jessica; Sánchez, Gladis; Magenheimer, Brenda S; Reif, Gail A; Wallace, Darren P; Calvet, James P; Blanco, Gustavo

    2015-12-01

    Cyst enlargement in autosomal dominant polycystic kidney disease (ADPKD) requires the transepithelial secretion of fluid into the cyst lumen. We previously showed that physiological amounts of ouabain enhance cAMP-dependent fluid secretion and cyst growth of human ADPKD cyst epithelial cells in culture and formation of cyst-like dilations in metanephric kidneys from Pkd1 mutant mice. Here, we investigated the mechanisms by which ouabain promotes cAMP-dependent fluid secretion and cystogenesis. Ouabain (3 nM) enhanced cAMP-induced cyst-like dilations in embryonic kidneys from Pkd1 (m1Bei) mice, but had no effect on metanephroi from Pkd1 (m1Bei) mice that lack expression of the cystic fibrosis transmembrane conductance regulator (CFTR). Similarly, ouabain stimulation of cAMP-induced fluid secretion and in vitro cyst growth of ADPKD cells were abrogated by CFTR inhibition, showing that CFTR is required for ouabain effects on ADPKD fluid secretion. Moreover, ouabain directly enhanced the cAMP-dependent Cl(-) efflux mediated by CFTR in ADPKD monolayers. Ouabain increased the trafficking of CFTR to the plasma membrane and up-regulated the expression of the CFTR activator PDZK1. Finally, ouabain decreased plasma membrane expression and activity of the Na,K-ATPase in ADPKD cells. Altogether, these results show that ouabain enhances net fluid secretion and cyst formation by activating apical anion secretion via CFTR and decreasing basolateral Na(+) transport via Na,K-ATPase. These results provide new information on the mechanisms by which ouabain affects ADPKD cells and further highlight the importance of ouabain as a non-genomic stimulator of cystogenesis in ADPKD.

  3. Ouabain Regulates CFTR-Mediated Anion Secretion and Na,K-ATPase Transport in ADPKD Cells.

    PubMed

    Jansson, Kyle; Venugopal, Jessica; Sánchez, Gladis; Magenheimer, Brenda S; Reif, Gail A; Wallace, Darren P; Calvet, James P; Blanco, Gustavo

    2015-12-01

    Cyst enlargement in autosomal dominant polycystic kidney disease (ADPKD) requires the transepithelial secretion of fluid into the cyst lumen. We previously showed that physiological amounts of ouabain enhance cAMP-dependent fluid secretion and cyst growth of human ADPKD cyst epithelial cells in culture and formation of cyst-like dilations in metanephric kidneys from Pkd1 mutant mice. Here, we investigated the mechanisms by which ouabain promotes cAMP-dependent fluid secretion and cystogenesis. Ouabain (3 nM) enhanced cAMP-induced cyst-like dilations in embryonic kidneys from Pkd1 (m1Bei) mice, but had no effect on metanephroi from Pkd1 (m1Bei) mice that lack expression of the cystic fibrosis transmembrane conductance regulator (CFTR). Similarly, ouabain stimulation of cAMP-induced fluid secretion and in vitro cyst growth of ADPKD cells were abrogated by CFTR inhibition, showing that CFTR is required for ouabain effects on ADPKD fluid secretion. Moreover, ouabain directly enhanced the cAMP-dependent Cl(-) efflux mediated by CFTR in ADPKD monolayers. Ouabain increased the trafficking of CFTR to the plasma membrane and up-regulated the expression of the CFTR activator PDZK1. Finally, ouabain decreased plasma membrane expression and activity of the Na,K-ATPase in ADPKD cells. Altogether, these results show that ouabain enhances net fluid secretion and cyst formation by activating apical anion secretion via CFTR and decreasing basolateral Na(+) transport via Na,K-ATPase. These results provide new information on the mechanisms by which ouabain affects ADPKD cells and further highlight the importance of ouabain as a non-genomic stimulator of cystogenesis in ADPKD. PMID:26289599

  4. Extracellular Na+ levels regulate formation and activity of the NaX/alpha1-Na+/K+-ATPase complex in neuronal cells

    PubMed Central

    Berret, Emmanuelle; Smith, Pascal Y.; Henry, Mélaine; Soulet, Denis; Hébert, Sébastien S.; Toth, Katalin; Mouginot, Didier; Drolet, Guy

    2014-01-01

    MnPO neurons play a critical role in hydromineral homeostasis regulation by acting as sensors of extracellular sodium concentration ([Na+]out). The mechanism underlying Na+-sensing involves Na+-flow through the NaX channel, directly regulated by the Na+/K+-ATPase α1-isoform which controls Na+-influx by modulating channel permeability. Together, these two partners form a complex involved in the regulation of intracellular sodium ([Na+]in). Here we aim to determine whether environmental changes in Na+ could actively modulate the NaX/Na+/K+-ATPase complex activity. We investigated the complex activity using patch-clamp recordings from rat MnPO neurons and Neuro2a cells. When the rats were fed with a high-salt-diet, or the [Na+] in the culture medium was increased, the activity of the complex was up-regulated. In contrast, drop in environmental [Na+] decreased the activity of the complex. Interestingly under hypernatremic condition, the colocalization rate and protein level of both partners were up-regulated. Under hyponatremic condition, only NaX protein expression was increased and the level of NaX/Na+/K+-ATPase remained unaltered. This unbalance between NaX and Na+/K+-ATPase pump proportion would induce a bigger portion of Na+/K+-ATPase-control-free NaX channel. Thus, we suggest that hypernatremic environment increases NaX/Na+/K+-ATPase α1-isoform activity by increasing the number of both partners and their colocalization rate, whereas hyponatremic environment down-regulates complex activity via a decrease in the relative number of NaX channels controlled by the pump. PMID:25538563

  5. Evidence for neutral transcellular NaCl transport and neutral basolateral chloride exit in the rabbit proximal convoluted tubule.

    PubMed Central

    Baum, M; Berry, C A

    1984-01-01

    The electrical nature of active NaCl transport and the significance of a basolateral membrane chloride conductance were examined in isolated perfused rabbit proximal convoluted tubules (PCT). PCT were perfused with a high chloride solution that simulated late proximal tubular fluid and were bathed in an albumin solution that simulated rabbit serum in the control and recovery periods. The electrical nature of NaCl transport was examined by bathing the tubules in a high chloride albumin solution where there were no anion gradients. Volume reabsorption (Jv) during the control and recovery period was 0.56 and 0.51 nl/mm X min, respectively, and 0.45 nl/mm X min when the tubules were bathed in a high chloride bath. The transepithelial potential difference (PD) during the control and recovery periods averaged 2.3 mV, but decreased to 0.0 mV in the absence of anion gradients, which indicated that NaCl transport is electroneutral. Further evidence that NaCl transport is electroneutral was obtained by examining the effect of addition of 0.01 mM ouabain in PCT perfused and bathed with high chloride solutions. The Jv was 0.54 nl/mm X min in the control period and not statistically different from zero after inhibition of active transport. The PD was not different from zero in both periods. Two groups of studies examined the role of basolateral membrane Cl- conductance in NaCl transport. First, depolarizing the basolateral membrane with 2 mM bath Ba++ did not significantly affect Jv or PD. Second, the effect of the presumptive Cl- conductance inhibitor anthracene-9-CO2H was examined. Anthracene-9-CO2H did not significantly affect Jv or PD. In conclusion, these data show that NaCl transport in the PCT is electroneutral and transcellular and provide evidence against a significant role for basolateral membrane chloride conductance in the rabbit PCT. PMID:6736248

  6. Structural perspectives on secondary active transporters

    PubMed Central

    Boudker, Olga; Verdon, Grégory

    2010-01-01

    Secondary active transporters catalyze concentrative transport of substrates across lipid membranes by harnessing the energy of electrochemical ion gradients. These transporters bind their ligands on one side of the membrane, and undergo a global conformational change to release them on the other side of the membrane. Over the last few years, crystal structures have captured several bacterial secondary transporters in different states along their transport cycle, providing insight into possible molecular mechanisms. In this review, we will summarize recent findings focusing on the emerging structural and mechanistic similarities between evolutionary diverse transporters. We will also discuss the structural basis of substrate binding, ion coupling and inhibition viewed from the perspective of these similarities. PMID:20655602

  7. The endocannabinoid system in renal cells: regulation of Na+ transport by CB1 receptors through distinct cell signalling pathways

    PubMed Central

    Sampaio, L S; Taveira Da Silva, R; Lima, D; Sampaio, C L C; Iannotti, F A; Mazzarella, E; Di Marzo, V; Vieyra, A; Reis, R A M; Einicker-Lamas, M

    2015-01-01

    Background and Purpose The function of the endocannabinoid system (ECS) in renal tissue is not completely understood. Kidney function is closely related to ion reabsorption in the proximal tubule, the nephron segment responsible for the re-absorption of 70–80% of the filtrate. We studied the effect of compounds modulating the activity of cannabinoid (CB) receptors on the active re-absorption of Na+ in LLC-PK1 cells. Experimental Approach Changes in Na+/K+-ATPase activity were assessed after treatment with WIN55,212-2 (WIN), a non-selective lipid agonist, and haemopressin (HP), an inverse peptide agonist at CB1 receptors. Pharmacological tools were used to investigate the signalling pathways involved in the modulation of Na+ transport. Key Results In addition to CB1 and CB2 receptors and TRPV1 channels, the mRNAs encoding for enzymes of the ECS were also expressed in LLC-PK1. WIN (10−7 M) and HP (10−6 M) altered Na+ re-absorption in LLC-PK1 in a dual manner. They both acutely (after 1 min) increased Na+/K+-ATPase activity in a TRPV1 antagonist-sensitive way. WIN's stimulating effect persisted for 30 min, and this effect was partially blocked by a CB1 antagonist or a PKC inhibitor. In contrast, HP inhibited Na+/K+-ATPase after 30 min incubation, and this effect was attenuated by a CB1 antagonist or a PKA inhibitor. Conclusion and Implications The ECS is expressed in LLC-PK1 cells. Both CB1 receptors and TRPV1 channels regulate Na+/K+-ATPase activity in these cells, and are modulated by lipid and peptide CB1 receptor ligands, which act via different signalling pathways. PMID:25537261

  8. Development of Na/sup +/-dependent hexose transport in vitro

    SciTech Connect

    Cook, J.S.; Amsler, K.; Weiss, E.R.; Shaffer, C.

    1981-01-01

    The desriptions given here of experiments with LLC-PK/sub 1/ cell transport systems are more of a progress report than a definitive statement. The cells give great promise for exploring the differentiation of an important transport system, but a number of cell biological problems need resolution first. The kinetic analysis described suggests that the individual cells become fully, possibly terminally, differentiated and remain so. It is equally desirable to have a means of separating differentiated from undifferentiated cells, and to know the transport capacity of each. With these questions resolved, the use of modulators of the rate of differentiation, acceleration by inducers and inhibition by tumor promoters, gives obviously important experimental handles in exploring the underlying processes. The clones that have been derived so far add another dimension to the possibilities of this cell system, since the clones show different responses to the inducers and to TPA and these differences will be of value in sorting out mechanisms.

  9. Study on Na layer response to geomagnetic activities based on Odin/OSIRIS Na density data

    NASA Astrophysics Data System (ADS)

    Tsuda, Takuo; Nakamura, Takuji; Hedin, Jonas; Gumbel, Jorg; Hosokawa, Keisuke; Ejiri, Mitsumu K.; Nishiyama, Takanori; Takahashi, Toru

    2016-07-01

    The Na layer is normally distributed from 80 to 110 km, and the height range is corresponding to the ionospheric D and E region. In the polar region, the energetic particles precipitating from the magnetosphere can often penetrate into the E region and even into the D region. Thus, the influence of the energetic particles to the Na layer is one of interests in the aspect of the atmospheric composition change accompanied with the auroral activity. There are several previous studies in this issue. For example, recently, we have reported an initial result on a clear relationship between the electron density increase (due to the energetic particles) and the Na density decrease from observational data sets obtained by Na lidar, EISCAT VHF radar, and optical instruments at Tromsoe, Norway on 24-25 January 2012. However, all of the previous studies had been carried out based on case studies by ground-based lidar observations. In this study, we have performed, for the first time, statistical analysis using Na density data from 2004 to 2009 obtained with the Optical Spectrograph and InfraRed Imager System (OSIRIS) onboard Odin satellite. In the presentation, we will show relationship between the Na density and geomagnetic activities, and its latitudinal variation. Based on these results, the Na layer response to the energetic particles will be discussed.

  10. Characterization of the fetal glucose transporter in rabbit kidney. Comparison with the adult brush border electrogenic Na+-glucose symporter.

    PubMed Central

    Beck, J C; Lipkowitz, M S; Abramson, R G

    1988-01-01

    Glucose transport was characterized in rabbit renal brush border membrane vesicles (BBMV) of the fetus late in gestation. Highly purified, osmotically reactive fetal BBMV contained a glucose transporter that was qualitatively indistinguishable from that in the adult: both are concentrative, Na+ dependent, electrogenic, stereospecific, and sensitive to phlorizin. Although the apparent Km for glucose is similar in the fetus and adult, the Vmax is significantly higher in the adult. When the membrane potential was clamped with a protonophore, this difference diminished; however, Vmax remained significantly higher in adult BBMV. This postnatal increase in Vmax was paralleled by a similar increase in the number of phlorizin binding sites. These findings indicate that the maturational increase in glucose transport is, in part, consequent to a more favorable electrical potential for Na+-dependent glucose transport and, in part, the result of the insertion of new transporters. The homogenate activity of several brush border enzymes also demonstrated significant maturational increases. The magnitude of these changes was variable and enzyme dependent. These combined observations suggest that mature expression of membrane proteins (transporters and enzymes) occurs at different stages of development of renal proximal tubule cells. PMID:3403709

  11. Structures of a Na+-coupled, substrate-bound MATE multidrug transporter.

    PubMed

    Lu, Min; Symersky, Jindrich; Radchenko, Martha; Koide, Akiko; Guo, Yi; Nie, Rongxin; Koide, Shohei

    2013-02-01

    Multidrug transporters belonging to the multidrug and toxic compound extrusion (MATE) family expel dissimilar lipophilic and cationic drugs across cell membranes by dissipating a preexisting Na(+) or H(+) gradient. Despite its clinical relevance, the transport mechanism of MATE proteins remains poorly understood, largely owing to a lack of structural information on the substrate-bound transporter. Here we report crystal structures of a Na(+)-coupled MATE transporter NorM from Neisseria gonorrheae in complexes with three distinct translocation substrates (ethidium, rhodamine 6G, and tetraphenylphosphonium), as well as Cs(+) (a Na(+) congener), all captured in extracellular-facing and drug-bound states. The structures revealed a multidrug-binding cavity festooned with four negatively charged amino acids and surprisingly limited hydrophobic moieties, in stark contrast to the general belief that aromatic amino acids play a prominent role in multidrug recognition. Furthermore, we discovered an uncommon cation-π interaction in the Na(+)-binding site located outside the drug-binding cavity and validated the biological relevance of both the substrate- and cation-binding sites by conducting drug resistance and transport assays. Additionally, we uncovered potential rearrangement of at least two transmembrane helices upon Na(+)-induced drug export. Based on our structural and functional analyses, we suggest that Na(+) triggers multidrug extrusion by inducing protein conformational changes rather than by directly competing for the substrate-binding amino acids. This scenario is distinct from the canonical antiport mechanism, in which both substrate and counterion compete for a shared binding site in the transporter. Collectively, our findings provide an important step toward a detailed and mechanistic understanding of multidrug transport. PMID:23341609

  12. H2O2 and cytosolic Ca2+ signals triggered by the PM H-coupled transport system mediate K+/Na+ homeostasis in NaCl-stressed Populus euphratica cells.

    PubMed

    Sun, Jian; Wang, Mei-Juan; Ding, Ming-Quan; Deng, Shu-Rong; Liu, Mei-Qin; Lu, Cun-Fu; Zhou, Xiao-Yang; Shen, Xin; Zheng, Xiao-Jiang; Zhang, Zeng-Kai; Song, Jin; Hu, Zan-Min; Xu, Yue; Chen, Shao-Liang

    2010-06-01

    Using confocal microscopy, X-ray microanalysis and the scanning ion-selective electrode technique, we investigated the signalling of H(2)O(2), cytosolic Ca(2+) ([Ca(2+)](cyt)) and the PM H(+)-coupled transport system in K(+)/Na(+) homeostasis control in NaCl-stressed calluses of Populus euphratica. An obvious Na(+)/H(+) antiport was seen in salinized cells; however, NaCl stress caused a net K(+) efflux, because of the salt-induced membrane depolarization. H(2)O(2) levels, regulated upwards by salinity, contributed to ionic homeostasis, because H(2)O(2) restrictions by DPI or DMTU caused enhanced K(+) efflux and decreased Na(+)/H(+) antiport activity. NaCl induced a net Ca(2+) influx and a subsequent rise of [Ca(2+)](cyt), which is involved in H(2)O(2)-mediated K(+)/Na(+) homeostasis in salinized P. euphratica cells. When callus cells were pretreated with inhibitors of the Na(+)/H(+) antiport system, the NaCl-induced elevation of H(2)O(2) and [Ca(2+)](cyt) was correspondingly restricted, leading to a greater K(+) efflux and a more pronounced reduction in Na(+)/H(+) antiport activity. Results suggest that the PM H(+)-coupled transport system mediates H(+) translocation and triggers the stress signalling of H(2)O(2) and Ca(2+), which results in a K(+)/Na(+) homeostasis via mediations of K(+) channels and the Na(+)/H(+) antiport system in the PM of NaCl-stressed cells. Accordingly, a salt stress signalling pathway of P. euphratica cells is proposed. PMID:20082667

  13. Ratchet transport powered by chiral active particles

    PubMed Central

    Ai, Bao-quan

    2016-01-01

    We numerically investigate the ratchet transport of mixtures of active and passive particles in a transversal asymmetric channel. A big passive particle is immersed in a ‘sea’ of active particles. Due to the chirality of active particles, the longitudinal directed transport is induced by the transversal asymmetry. For the active particles, the chirality completely determines the direction of the ratchet transport, the counterclockwise and clockwise particles move to the opposite directions and can be separated. However, for the passive particle, the transport behavior becomes complicated, the direction is determined by competitions among the chirality, the self-propulsion speed, and the packing fraction. Interestingly, within certain parameters, the passive particle moves to the left, while active particles move to the right. In addition, there exist optimal parameters (the chirality, the height of the barrier, the self-propulsion speed and the packing fraction) at which the rectified efficiency takes its maximal value. Our findings could be used for the experimental pursuit of the ratchet transport powered by chiral active particles. PMID:26795952

  14. Ratchet transport powered by chiral active particles.

    PubMed

    Ai, Bao-quan

    2016-01-01

    We numerically investigate the ratchet transport of mixtures of active and passive particles in a transversal asymmetric channel. A big passive particle is immersed in a 'sea' of active particles. Due to the chirality of active particles, the longitudinal directed transport is induced by the transversal asymmetry. For the active particles, the chirality completely determines the direction of the ratchet transport, the counterclockwise and clockwise particles move to the opposite directions and can be separated. However, for the passive particle, the transport behavior becomes complicated, the direction is determined by competitions among the chirality, the self-propulsion speed, and the packing fraction. Interestingly, within certain parameters, the passive particle moves to the left, while active particles move to the right. In addition, there exist optimal parameters (the chirality, the height of the barrier, the self-propulsion speed and the packing fraction) at which the rectified efficiency takes its maximal value. Our findings could be used for the experimental pursuit of the ratchet transport powered by chiral active particles.

  15. Active sodium transport and fluid secretion in the gall-bladder epithelium of Necturus.

    PubMed Central

    Giraldez, F

    1984-01-01

    Intracellular Na, K and Cl activities (acNa, acK and acCl) and membrane potentials were measured in Necturus gall-bladder epithelium using double-barrelled ion-sensitive micro-electrodes. Mucosal membrane potential was about -55 mV and the mean control activities were acNa = 14.7 mM, acK = 91.6 mM and acCl = 20.3 mM. Replacing mucosal Na by K caused a fall in acNa that followed an exponential time course. The rate of change in acNa was linearly related to acNa above a certain value (congruent to 3 mM). acK and acCl both increased in K Ringer solution. From the change in all three ions the cell was estimated to swell at an initial rate of 0.13% s-1. From the initial rate of change in acNa, a net cell efflux of Na of 405 pmol cm-2 s-1 was calculated. Replacement of Na by Tris or choline led to a similar result. The transepithelial Na transport rate was for this group of animals 346 pmol cm-2 s-1. Ouabain (10(-3) M) produced an increase in acNa and acCl, whereas acK decreased. The cells were estimated to swell at an initial rate of 0.06% s-1. The initial Na influx after Na-pump inhibition was calculated to be 162 pmol cm-2 s-1. The parallel measure of the transepithelial rate of transport of Na gave a value of 189 pmol cm-2 s-1. Ouabain inhibited the decrease in acNa after replacement of Na by K by about 80%. A fast depolarization, ranging from 2 to 7 mV, occurred after the perfusion with ouabain. Em then slowly decreased from about 53 to 32 mV in 1 h. It is concluded that (a) the major fraction of the transepithelial transport of Na is transcellular and mediated by the Na pump, (b) the pumping rate is linearly dependent on internal Na within a certain range and (c) the Na pump is electrogenic under normal circumstances. PMID:6716291

  16. Patterns of K+ permeation following inhibition of Na+ transport in rabbit cortical collecting tubule.

    PubMed

    Stokes, J B

    1986-01-01

    The passive (lumen-to-bath) K+ permeation (KK) of rabbit cortical collecting tubules was measured before and after inhibition of Na+ transport. Inhibition of the Na-K pump with ouabain reduced KK. This result contrasts sharply with the previously described increase in KK observed following inhibition of Na+ transport with amiloride. These opposite changes in KK are owing to the fact that a substantial component of the lumen-to-bath K+ permeation involves a transcellular pathway. Amiloride, because it hyperpolarizes the apical membrane, increases KK; ouabain, because it depolarizes the cell, decreases KK. Previous results have also suggested that the cell K+ permeability is secondarily altered by these agents so that the changes in voltage and permeability are additive. These patterns of changes in KK were used to evaluate the mechanism of action of two agents that partially inhibit Na+ transport: vasopressin and prostaglandin (PG) E2. Their effect on KK was qualitatively similar to that of amiloride. In amiloride-treated tubules, neither vasopressin nor PGE2 altered KK. Neither did they alter the normal reduction in KK caused by pump inhibition. Thus they did not have any direct effect on K+ permeability. These results are consistent with the thesis that vasopressin and PGE2 inhibit Na+ absorption by reducing apical membrane permeability. The relation between the regulation of Na+ absorption and K+ permeation may have important implications for the regulation of K+ secretion by the cortical collecting tubule.

  17. NaDC3 Induces Premature Cellular Senescence by Promoting Transport of Krebs Cycle Intermediates, Increasing NADH, and Exacerbating Oxidative Damage.

    PubMed

    Ma, Yuxiang; Bai, Xue-Yuan; Du, Xuan; Fu, Bo; Chen, Xiangmei

    2016-01-01

    High-affinity sodium-dependent dicarboxylate cotransporter 3 (NaDC3) is a key metabolism-regulating membrane protein responsible for transport of Krebs cycle intermediates. NaDC3 is upregulated as organs age, but knowledge regarding the underlying mechanisms by which NaDC3 modulates mammalian aging is limited. In this study, we showed that NaDC3 overexpression accelerated cellular senescence in young human diploid cells (MRC-5 and WI-38) and primary renal tubular cells, leading to cell cycle arrest in G1 phase and increased expression of senescent biomarkers, senescence-associated β-galactosidase and p16. Intracellular levels of reactive oxygen species, 8-hydroxy-2'-deoxyguanosine, malondialdehyde, and carbonyl were significantly enhanced, and activities of respiratory complexes I and III and ATP level were significantly decreased in NaDC3-infected cells. Stressful premature senescent phenotypes induced by NaDC3 were markedly ameliorated via treatment with the antioxidants Tiron and Tempol. High expression of NaDC3 caused a prominent increase in intracellular levels of Krebs cycle intermediates and NADH. Exogenous NADH and NAD(+) may aggravate and attenuate the aging phenotypes induced by NaDC3, respectively. These results suggest that NaDC3 can induce premature cellular senescence by promoting the transport of Krebs cycle intermediates, increasing generation of NADH and reactive oxygen species and leading to oxidative damage. Our results clarify the aging signaling pathway regulated by NaDC3. PMID:25384549

  18. NaDC3 Induces Premature Cellular Senescence by Promoting Transport of Krebs Cycle Intermediates, Increasing NADH, and Exacerbating Oxidative Damage.

    PubMed

    Ma, Yuxiang; Bai, Xue-Yuan; Du, Xuan; Fu, Bo; Chen, Xiangmei

    2016-01-01

    High-affinity sodium-dependent dicarboxylate cotransporter 3 (NaDC3) is a key metabolism-regulating membrane protein responsible for transport of Krebs cycle intermediates. NaDC3 is upregulated as organs age, but knowledge regarding the underlying mechanisms by which NaDC3 modulates mammalian aging is limited. In this study, we showed that NaDC3 overexpression accelerated cellular senescence in young human diploid cells (MRC-5 and WI-38) and primary renal tubular cells, leading to cell cycle arrest in G1 phase and increased expression of senescent biomarkers, senescence-associated β-galactosidase and p16. Intracellular levels of reactive oxygen species, 8-hydroxy-2'-deoxyguanosine, malondialdehyde, and carbonyl were significantly enhanced, and activities of respiratory complexes I and III and ATP level were significantly decreased in NaDC3-infected cells. Stressful premature senescent phenotypes induced by NaDC3 were markedly ameliorated via treatment with the antioxidants Tiron and Tempol. High expression of NaDC3 caused a prominent increase in intracellular levels of Krebs cycle intermediates and NADH. Exogenous NADH and NAD(+) may aggravate and attenuate the aging phenotypes induced by NaDC3, respectively. These results suggest that NaDC3 can induce premature cellular senescence by promoting the transport of Krebs cycle intermediates, increasing generation of NADH and reactive oxygen species and leading to oxidative damage. Our results clarify the aging signaling pathway regulated by NaDC3.

  19. Long-term transportation noise annoyance is associated with subsequent lower levels of physical activity.

    PubMed

    Foraster, Maria; Eze, Ikenna C; Vienneau, Danielle; Brink, Mark; Cajochen, Christian; Caviezel, Seraina; Héritier, Harris; Schaffner, Emmanuel; Schindler, Christian; Wanner, Miriam; Wunderli, Jean-Marc; Röösli, Martin; Probst-Hensch, Nicole

    2016-05-01

    Noise annoyance (NA) might lead to behavioral patterns not captured by noise levels, which could reduce physical activity (PA) either directly or through impaired sleep and constitute a noise pathway towards cardiometabolic diseases. We investigated the association of long-term transportation NA and its main sources (aircraft, road, and railway) at home with PA levels. We assessed 3842 participants (aged 37-81) that attended the three examinations (SAP 1, 2, and 3 in years 1991, 2001 and 2011, respectively) of the population-based Swiss cohort on Air Pollution and Lung and Heart Diseases in Adults (SAPALDIA). Participants reported general 24-h transportation NA (in all examinations) and source-specific NA at night (only SAP 3) on an ICBEN-type 11-point scale. We assessed moderate, vigorous, and total PA from a short-questionnaire (SAP 3). The main outcome was moderate PA (active/inactive: cut-off≥150min/week). We used logistic regression including random effects by area and adjusting for age, sex, socioeconomic status, and lifestyles (main model) and evaluated potential effect modifiers. We analyzed associations with PA at SAP 3 a) cross-sectionally: for source-specific and transportation NA in the last year (SAP 3), and b) longitudinally: for 10-y transportation NA (mean of SAP 1+2), adjusting for prior PA (SAP 2) and changes in NA (SAP 3-2). Reported NA (score≥5) was 16.4%, 7.5%, 3%, and 1.1% for 1-year transportation, road, aircraft, and railway at SAP 3, respectively. NA was greater in the past, reaching 28.5% for 10-y transportation NA (SAP 1+2). The 10-y transportation NA was associated with a 3.2% (95% CI: 6%-0.2%) decrease in moderate PA per 1-NA rating point and was related to road and aircraft NA at night in cross-sectional analyses. The longitudinal association was stronger for women, reported daytime sleepiness or chronic diseases and it was not explained by objectively modeled levels of road traffic noise at SAP 3. In conclusion, long-term NA

  20. Development of novel active transport membrande devices

    SciTech Connect

    Laciak, D.V.

    1994-11-01

    Air Products has undertaken a research program to fabricate and evaluate gas separation membranes based upon promising ``active-transport`` (AT) materials recently developed in our laboratories. Active Transport materials are ionic polymers and molten salts which undergo reversible interaction or reaction with ammonia and carbon dioxide. The materials are useful for separating these gases from mixtures with hydrogen. Moreover, AT membranes have the unique property of possessing high permeability towards ammnonia and carbon dioxide but low permeability towards hydrogen and can thus be used to permeate these components from a gas stream while retaining hydrogen at high pressure.

  1. Indirect activation of the epithelial Na+ channel by trypsin.

    PubMed

    Bengrine, Abderrahmane; Li, Jinqing; Hamm, L Lee; Awayda, Mouhamed S

    2007-09-14

    We tested the hypothesis that the serine protease trypsin can indirectly activate the epithelial Na(+) channel (ENaC). Experiments were carried out in Xenopus oocytes and examined the effects on the channel formed by all three human ENaC subunits and that formed by Xenopus epsilon and human beta and gamma subunits (epsilonbetagammaENaC). Low levels of trypsin (1-10 ng/ml) were without effects on the oocyte endogenous conductances and were specifically used to test the effects on ENaC. Addition of 1 ng/ml trypsin for 60 min stimulated the amiloride-sensitive human ENaC conductance (g(Na)) by approximately 6-fold. This effect on the g(Na) was [Na(+)]-independent, thereby ruling out an interaction with channel feedback inhibition by Na(+). The indirect nature of this activation was confirmed in cell-attached patch clamp experiments with trypsin added to the outside of the pipette. Trypsin was comparatively ineffective at activating epsilonbetagammaENaC, a channel that exhibited a high spontaneous open probability. These observations, in combination with surface binding experiments, indicated that trypsin indirectly activated membrane-resident channels. Activation by trypsin was also dependent on catalytic activity of this protease but was not accompanied by channel subunit proteolysis. Channel activation was dependent on downstream activation of G-proteins and was blocked by G-protein inhibition by injection of guanyl-5'-yl thiophosphate and by pre-stimulation of phospholipase C. These data indicate a receptor-mediated activation of ENaC by trypsin. This trypsin-activated receptor is distinct from that of protease-activated receptor-2, because the response to trypsin was unaffected by protease-activated receptor-2 overexpression or knockdown. PMID:17627947

  2. Health Impacts of Active Transportation in Europe

    PubMed Central

    Rojas-Rueda, David; de Nazelle, Audrey; Andersen, Zorana J.; Braun-Fahrländer, Charlotte; Bruha, Jan; Bruhova-Foltynova, Hana; Desqueyroux, Hélène; Praznoczy, Corinne; Ragettli, Martina S.; Tainio, Marko; Nieuwenhuijsen, Mark J.

    2016-01-01

    Policies that stimulate active transportation (walking and bicycling) have been related to heath benefits. This study aims to assess the potential health risks and benefits of promoting active transportation for commuting populations (age groups 16–64) in six European cities. We conducted a health impact assessment using two scenarios: increased cycling and increased walking. The primary outcome measure was all-cause mortality related to changes in physical activity level, exposure to fine particulate matter air pollution with a diameter <2.5 μm, as well as traffic fatalities in the cities of Barcelona, Basel, Copenhagen, Paris, Prague, and Warsaw. All scenarios produced health benefits in the six cities. An increase in bicycle trips to 35% of all trips (as in Copenhagen) produced the highest benefits among the different scenarios analysed in Warsaw 113 (76–163) annual deaths avoided, Prague 61 (29–104), Barcelona 37 (24–56), Paris 37 (18–64) and Basel 5 (3–9). An increase in walking trips to 50% of all trips (as in Paris) resulted in 19 (3–42) deaths avoided annually in Warsaw, 11(3–21) in Prague, 6 (4–9) in Basel, 3 (2–6) in Copenhagen and 3 (2–4) in Barcelona. The scenarios would also reduce carbon dioxide emissions in the six cities by 1,139 to 26,423 (metric tonnes per year). Policies to promote active transportation may produce health benefits, but these depend of the existing characteristics of the cities. Increased collaboration between health practitioners, transport specialists and urban planners will help to introduce the health perspective in transport policies and promote active transportation. PMID:26930213

  3. Health Impacts of Active Transportation in Europe.

    PubMed

    Rojas-Rueda, David; de Nazelle, Audrey; Andersen, Zorana J; Braun-Fahrländer, Charlotte; Bruha, Jan; Bruhova-Foltynova, Hana; Desqueyroux, Hélène; Praznoczy, Corinne; Ragettli, Martina S; Tainio, Marko; Nieuwenhuijsen, Mark J

    2016-01-01

    Policies that stimulate active transportation (walking and bicycling) have been related to heath benefits. This study aims to assess the potential health risks and benefits of promoting active transportation for commuting populations (age groups 16-64) in six European cities. We conducted a health impact assessment using two scenarios: increased cycling and increased walking. The primary outcome measure was all-cause mortality related to changes in physical activity level, exposure to fine particulate matter air pollution with a diameter <2.5 μm, as well as traffic fatalities in the cities of Barcelona, Basel, Copenhagen, Paris, Prague, and Warsaw. All scenarios produced health benefits in the six cities. An increase in bicycle trips to 35% of all trips (as in Copenhagen) produced the highest benefits among the different scenarios analysed in Warsaw 113 (76-163) annual deaths avoided, Prague 61 (29-104), Barcelona 37 (24-56), Paris 37 (18-64) and Basel 5 (3-9). An increase in walking trips to 50% of all trips (as in Paris) resulted in 19 (3-42) deaths avoided annually in Warsaw, 11(3-21) in Prague, 6 (4-9) in Basel, 3 (2-6) in Copenhagen and 3 (2-4) in Barcelona. The scenarios would also reduce carbon dioxide emissions in the six cities by 1,139 to 26,423 (metric tonnes per year). Policies to promote active transportation may produce health benefits, but these depend of the existing characteristics of the cities. Increased collaboration between health practitioners, transport specialists and urban planners will help to introduce the health perspective in transport policies and promote active transportation.

  4. Health Impacts of Active Transportation in Europe.

    PubMed

    Rojas-Rueda, David; de Nazelle, Audrey; Andersen, Zorana J; Braun-Fahrländer, Charlotte; Bruha, Jan; Bruhova-Foltynova, Hana; Desqueyroux, Hélène; Praznoczy, Corinne; Ragettli, Martina S; Tainio, Marko; Nieuwenhuijsen, Mark J

    2016-01-01

    Policies that stimulate active transportation (walking and bicycling) have been related to heath benefits. This study aims to assess the potential health risks and benefits of promoting active transportation for commuting populations (age groups 16-64) in six European cities. We conducted a health impact assessment using two scenarios: increased cycling and increased walking. The primary outcome measure was all-cause mortality related to changes in physical activity level, exposure to fine particulate matter air pollution with a diameter <2.5 μm, as well as traffic fatalities in the cities of Barcelona, Basel, Copenhagen, Paris, Prague, and Warsaw. All scenarios produced health benefits in the six cities. An increase in bicycle trips to 35% of all trips (as in Copenhagen) produced the highest benefits among the different scenarios analysed in Warsaw 113 (76-163) annual deaths avoided, Prague 61 (29-104), Barcelona 37 (24-56), Paris 37 (18-64) and Basel 5 (3-9). An increase in walking trips to 50% of all trips (as in Paris) resulted in 19 (3-42) deaths avoided annually in Warsaw, 11(3-21) in Prague, 6 (4-9) in Basel, 3 (2-6) in Copenhagen and 3 (2-4) in Barcelona. The scenarios would also reduce carbon dioxide emissions in the six cities by 1,139 to 26,423 (metric tonnes per year). Policies to promote active transportation may produce health benefits, but these depend of the existing characteristics of the cities. Increased collaboration between health practitioners, transport specialists and urban planners will help to introduce the health perspective in transport policies and promote active transportation. PMID:26930213

  5. Functional characterization in Xenopus oocytes of Na+ transport systems from durum wheat reveals diversity among two HKT1;4 transporters

    PubMed Central

    Masmoudi, Khaled; Véry, Anne-Aliénor

    2014-01-01

    Plant tolerance to salinity constraint involves complex and integrated functions including control of Na+ uptake, translocation, and compartmentalization. Several members of the high-affinity K+ transporter (HKT) family, which comprises plasma-membrane transporters permeable to K+ and Na+ or to Na+ only, have been shown to play major roles in plant Na+ and K+ homeostasis. Among them, HKT1;4 has been identified as corresponding to a quantitative trait locus (QTL) of salt tolerance in wheat but was not functionally characterized. Here, we isolated two HKT1;4-type cDNAs from a salt-tolerant durum wheat (Triticum turgidum L. subsp. durum) cultivar, Om Rabia3, and investigated the functional properties of the encoded transporters using a two-electrode voltage-clamp technique, after expression in Xenopus oocytes. Both transporters displayed high selectivity for Na+, their permeability to other monovalent cations (K+, Li+, Cs+, and Rb+) being ten times lower than that to Na+. Both TdHKT1;4-1 and TdHKT1;4-2 transported Na+ with low affinity, although the half-saturation of the conductance was observed at a Na+ concentration four times lower in TdHKT1;4-1 than in TdHKT1;4-2. External K+ did not inhibit Na+ transport through these transporters. Quinine slightly inhibited TdHKT1;4-2 but not TdHKT1;4-1. Overall, these data identified TdHKT1;4 transporters as new Na+-selective transporters within the HKT family, displaying their own functional features. Furthermore, they showed that important differences in affinity exist among durum wheat HKT1;4 transporters. This suggests that the salt tolerance QTL involving HKT1;4 may be at least in part explained by functional variability among wheat HKT1;4-type transporters. PMID:24192995

  6. Effects of dietary salt on renal Na+ transporter subcellular distribution, abundance, and phosphorylation status.

    PubMed

    Yang, Li E; Sandberg, Monica B; Can, Argun D; Pihakaski-Maunsbach, Kaarina; McDonough, Alicia A

    2008-10-01

    During high-salt (HS) diet the kidney increases urinary Na+ and volume excretion to match intake. We recently reported that HS provokes a redistribution of distal convoluted tubule Na+-Cl- cotransporter (NCC) from apical to subapical vesicles and decreases NCC abundance. This study aimed to test the hypothesis that the other renal Na+ transporters' abundance and or subcellular distribution is decreased by HS diet. Six-week-old Sprague-Dawley rats were fed a normal (NS) 0.4% NaCl diet or a HS 4% NaCl diet for 3 wk or overnight. Kidneys excised from anesthetized rats were fractionated on density gradients or analyzed by microscopy; transporters and associated regulators were detected with specific antibodies. Three-week HS doubled Na+/H+ exchanger (NHE)3 phosphorylation at serine 552 and provoked a redistribution of NHE3, dipeptidyl peptidase IV (DPPIV), myosin VI, Na+-Pi cotransporter (NaPi)-2, ANG II type 2 receptor (AT2R), aminopeptidase N (APN), Na+-K+-2Cl- cotransporter (NKCC2), epithelial Na+ channel (ENaC) beta-subunit, and Na+-K+-ATPase (NKA) alpha1- and beta1-subunits from low-density plasma membrane-enriched fractions to higher-density intracellular membrane-enriched fractions. NHE3, myosin VI, and AT2R retraction to the base of the microvilli (MV) during HS was evident by confocal microscopy. HS did not change abundance of NHE3, NKCC, or NKA alpha1- or beta1-subunits but increased ENaC-beta in high-density intracellular enriched membranes. Responses to HS were fully apparent after just 18 h. We propose that retraction of NHE3 to the base of the MV, driven by myosin VI and NHE3 phosphorylation and accompanied by redistribution of the NHE3 regulator DPPIV, contributes to a decrease in proximal tubule Na+ reabsorption during HS and that redistribution of transporters out of low-density plasma membrane-enriched fractions in the thick ascending limb of the loop of Henle and distal nephron may also contribute to the homeostatic natriuretic response to HS diet

  7. 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

  8. Phosphorylation and activation of the plasma membrane Na+/H+ exchanger (NHE1) during osmotic cell shrinkage.

    PubMed

    Rigor, Robert R; Damoc, Catalina; Phinney, Brett S; Cala, Peter M

    2011-01-01

    The Na(+)/H(+)Exchanger isoform 1 (NHE1) is a highly versatile, broadly distributed and precisely controlled transport protein that mediates volume and pH regulation in most cell types. NHE1 phosphorylation contributes to Na(+)/H(+) exchange activity in response to phorbol esters, growth factors or protein phosphatase inhibitors, but has not been observed during activation by osmotic cell shrinkage (OCS). We examined the role of NHE1 phosphorylation during activation by OCS, using an ideal model system, the Amphiuma tridactylum red blood cell (atRBC). Na(+)/H(+) exchange in atRBCs is mediated by an NHE1 homolog (atNHE1) that is 79% identical to human NHE1 at the amino acid level. NHE1 activity in atRBCs is exceptionally robust in that transport activity can increase more than 2 orders of magnitude from rest to full activation. Michaelis-Menten transport kinetics indicates that either OCS or treatment with the phosphatase inhibitor calyculin-A (CLA) increase Na(+) transport capacity without affecting transport affinity (K(m)=44 mM) in atRBCs. CLA and OCS act non-additively to activate atNHE1, indicating convergent, phosphorylation-dependent signaling in atNHE1 activation. In situ(32)P labeling and immunoprecipitation demonstrates that the net phosphorylation of atNHE1 is increased 4-fold during OCS coinciding with a more than 2-order increase in Na(+) transport activity. This is the first reported evidence of increased NHE1 phosphorylation during OCS in any vertebrate cell type. Finally, liquid chromatography and mass spectrometry (LC-MS/MS) analysis of atNHE1 immunoprecipitated from atRBC membranes reveals 9 phosphorylated serine/threonine residues, suggesting that activation of atNHE1 involves multiple phosphorylation and/or dephosphorylation events. PMID:22216214

  9. Cation Transport Coupled to ATP Hydrolysis by the (Na, K)-ATPase: An Integrated, Animated Model

    ERIC Educational Resources Information Center

    Leone, Francisco A.; Furriel, Rosa P. M.; McNamara, John C.; Horisberger, Jean D.; Borin, Ivana A.

    2010-01-01

    An Adobe[R] animation is presented for use in undergraduate Biochemistry courses, illustrating the mechanism of Na[superscript +] and K[superscript +] translocation coupled to ATP hydrolysis by the (Na, K)-ATPase, a P[subscript 2c]-type ATPase, or ATP-powered ion pump that actively translocates cations across plasma membranes. The enzyme is also…

  10. Molecular dynamics simulations of Na{sup +} and leucine transport by LeuT

    SciTech Connect

    Chen, Rong Chung, Shin-Ho

    2015-08-14

    Molecular dynamics simulations are used to gain insight into the binding of Na{sup +} and leucine substrate to the bacterial amino acid transporter LeuT, focusing on the crystal structures of LeuT in the outward-open and inward-open states. For both conformations of LeuT, a third Na{sup +} binding site involving Glu290 in addition to the two sites identified from the crystal structures is observed. Once the negative charge from Glu290 in the inward-open LeuT is removed, the ion bound to the third site is ejected from LeuT rapidly, suggesting that the protonation state of Glu290 regulates Na{sup +} binding and release. In Cl{sup −}-dependent transporters where Glu290 is replaced by a neutral serine, a Cl{sup −} ion would be required to replace the role of Glu290. Thus, the simulations provide insights into understanding Na{sup +} and substrate transport as well as Cl{sup −}-independence of LeuT. - Highlights: • Ion binding site involving Glu290 is identified in the outward- and inward-open LeuT. • Sodium is released from inward-open LeuT once the side chain of Glu290 is protonated. • Protonation state of Glu290 regulates sodium binding and transport in LeuT.

  11. Fast Na/+/-ion transport in skeleton structures. [solid electrolyte applications

    NASA Technical Reports Server (NTRS)

    Goodenough, J. B.; Hong, H. Y.-P.; Kafalas, J. A.

    1976-01-01

    The skeleton structures considered in the investigations consist of a rigid subarray with an interconnected interstitial space in which ions move in three dimensions. The classes of skeleton structures investigated include the Im3 phase of high-pressure KSbO3, the defect-pyrochlore structure illustrated by RbMgAlF6, and the carnegieite structure of high-temperature NaAlSiO4. A description is given of the results obtained in transport measurements involving dense polycrystalline ceramic disks. Results obtained in the case of the Na(+)-ion transport in Na3Zr2PSi2O12 appear particularly promising concerning the possible use of such substances in solid-electrolyte applications.

  12. Na(+) -Activated K(+) Channels in Rat Supraoptic Neurones.

    PubMed

    Bansal, V; Fisher, T E

    2016-06-01

    The magnocellular neurosecretory cells (MNCs) of the hypothalamus secrete the neurohormones vasopressin and oxytocin. The systemic release of these hormones depends on the rate and pattern of MNC firing and it is therefore important to identify the ion channels that contribute to the electrical behaviour of MNCs. In the present study, we report evidence for the presence of Na(+) -activated K(+) (KN a ) channels in rat MNCs. KN a channels mediate outwardly rectifying K(+) currents activated by the increases in intracellular Na(+) that occur during electrical activity. Although the molecular identity of native KN a channels is unclear, their biophysical properties are consistent with those of expressed Slick (slo 2.1) and Slack (slo 2.2) proteins. Using immunocytochemistry and Western blot experiments, we found that both Slick and Slack proteins are expressed in rat MNCs. Using whole cell voltage clamp techniques on acutely isolated rat MNCs, we found that inhibiting Na(+) influx by the addition of the Na(+) channel blocker tetrodotoxin or the replacement of Na(+) in the external solution with Li(+) caused a significant decrease in sustained outward currents. Furthermore, the evoked outward current density was significantly higher in rat MNCs using patch pipettes containing 60 mm Na(+) than it was when patch pipettes containing 0 mm Na(+) were used. Our data show that functional KN a channels are expressed in rat MNCs. These channels could contribute to the activity-dependent afterhyperpolarisations that have been identified in the MNCs and thereby play a role in the regulation of their electrical behaviour. PMID:27091544

  13. Fluid transport by active elastic membranes

    NASA Astrophysics Data System (ADS)

    Evans, Arthur A.; Lauga, Eric

    2011-09-01

    A flexible membrane deforming its shape in time can self-propel in a viscous fluid. Alternatively, if the membrane is anchored, its deformation will lead to fluid transport. Past work in this area focused on situations where the deformation kinematics of the membrane were prescribed. Here we consider models where the deformation of the membrane is not prescribed, but instead the membrane is internally forced. Both the time-varying membrane shape and the resulting fluid motion result then from a balance between prescribed internal active stresses, internal passive resistance, and external viscous stresses. We introduce two specific models for such active internal forcing: one where a distribution of active bending moments is prescribed, and one where active inclusions exert normal stresses on the membrane by pumping fluid through it. In each case, we asymptotically calculate the membrane shape and the fluid transport velocities for small forcing amplitudes, and recover our results using scaling analysis.

  14. Drug Transporters and Na+/H+ Exchange Regulatory Factor PSD-95/Drosophila Discs Large/ZO-1 Proteins

    PubMed Central

    Walsh, Dustin R.; Nolin, Thomas D.

    2015-01-01

    Drug transporters govern the absorption, distribution, and elimination of pharmacologically active compounds. Members of the solute carrier and ATP binding-cassette drug transporter family mediate cellular drug uptake and efflux processes, thereby coordinating the vectorial movement of drugs across epithelial barriers. To exert their physiologic and pharmacological function in polarized epithelia, drug transporters must be targeted and stabilized to appropriate regions of the cell membrane (i.e., apical versus basolateral). Despite the critical importance of drug transporter membrane targeting, the mechanisms that underlie these processes are largely unknown. Several clinically significant drug transporters possess a recognition sequence that binds to PSD-95/Drosophila discs large/ZO-1 (PDZ) proteins. PDZ proteins, such as the Na+/H+ exchanger regulatory factor (NHERF) family, act to stabilize and organize membrane targeting of multiple transmembrane proteins, including many clinically relevant drug transporters. These PDZ proteins are normally abundant at apical membranes, where they tether membrane-delimited transporters. NHERF expression is particularly high at the apical membrane in polarized tissue such as intestinal, hepatic, and renal epithelia, tissues important to drug disposition. Several recent studies have highlighted NHERF proteins as determinants of drug transporter function secondary to their role in controlling membrane abundance and localization. Mounting evidence strongly suggests that NHERF proteins may have clinically significant roles in pharmacokinetics and pharmacodynamics of several pharmacologically active compounds and may affect drug action in cancer and chronic kidney disease. For these reasons, NHERF proteins represent a novel class of post-translational mediators of drug transport and novel targets for new drug development. PMID:26092975

  15. Basolateral Na+/HCO3– cotransport activity is regulated by the dissociable Na+/H+ exchanger regulatory factor

    PubMed Central

    Bernardo, Angelito A.; Kear, Felicidad T.; Santos, Anna V.P.; Ma, Jianfei; Steplock, Debra; Robey, R. Brooks; Weinman, Edward J.

    1999-01-01

    In the renal proximal tubule, the activities of the basolateral Na+/HCO3– cotransporter (NBC) and the apical Na+/H+ exchanger (NHE3) uniformly vary in parallel, suggesting that they are coordinately regulated. PKA-mediated inhibition of NHE3 is mediated by a PDZ motif–containing protein, the Na+/H+ exchanger regulatory factor (NHE-RF). Given the common inhibition of these transporters after protein kinase A (PKA) activation, we sought to determine whether NHE-RF also plays a role in PKA-regulated NBC activity. Renal cortex immunoblot analysis using anti-peptide antibodies directed against rabbit NHE-RF demonstrated the presence of this regulatory factor in both brush-border membranes (BBMs) and basolateral membranes (BLMs). Using a reconstitution assay, we found that limited trypsin digestion of detergent solubilized rabbit renal BLM preparations resulted in NBC activity that was unaffected by PKA activation. Co-reconstitution of these trypsinized preparations with a recombinant protein corresponding to wild-type rabbit NHE-RF restored the inhibitory effect of PKA on NBC activity in a concentration-dependent manner. NBC activity was inhibited 60% by 10–8M NHE-RF; this effect was not observed in the absence of PKA. Reconstitution with heat-denatured NHE-RF also failed to attenuate NBC activity. To establish further a physiologic role for NHE-RF in NBC regulation, the renal epithelial cell line B-SC-1, which lacks detectable endogenous NHE-RF expression, was engineered to express stably an NHE-RF transgene. NHE-RF–expressing B-SC-1 cells (B-SC-RF) exhibited markedly lower basal levels of NBC activity than did wild-type controls. Inhibition of NBC activity in B-SC-RF cells was enhanced after 10 μM of forskolin treatment, consistent with a postulated role for NHE-RF in mediating the inhibition of NBC activity by PKA. These findings not only suggest NHE-RF involvement in PKA-regulated NBC activity, but also provide a unique molecular mechanism whereby

  16. [Effect of artificial NaC1 and KC1 gradients on the active transport of organic acids in energy-depleted kidney proximal tubules. II. The KC1 gradient].

    PubMed

    Mozhaeva, M G; Bresler, V M; Nikiforov, A A

    1982-07-01

    The stimulatory effect of KCL in bath medium on fluorescein uptake in superficial proximal tubules in the absence of Na in bath medium was observed on Na- and energy-depleted slices of the rat kidney outer cortex. In the absence of K gradient between bath medium and tubular cells, the fluorescein uptake increased with raising the intracellular K concentration. The efflux of fluorescein from the tubules was inversely proportional to K concentration in the cells. Visual control showed that at high K concentrations fluorescein was accumulated mainly in the tubular walls (i. e. in the cytoplasm of tubular cells). It is suggested that the raise of K concentration in cells results in the intracellular binding of organic acid.

  17. Inhibition of K+ Transport through Na+, K+-ATPase by Capsazepine: Role of Membrane Span 10 of the α-Subunit in the Modulation of Ion Gating

    PubMed Central

    Mahmmoud, Yasser A.; Shattock, Michael; Cornelius, Flemming; Pavlovic, Davor

    2014-01-01

    Capsazepine (CPZ) inhibits Na+,K+-ATPase-mediated K+-dependent ATP hydrolysis with no effect on Na+-ATPase activity. In this study we have investigated the functional effects of CPZ on Na+,K+-ATPase in intact cells. We have also used well established biochemical and biophysical techniques to understand how CPZ modifies the catalytic subunit of Na+,K+-ATPase. In isolated rat cardiomyocytes, CPZ abolished Na+,K+-ATPase current in the presence of extracellular K+. In contrast, CPZ stimulated pump current in the absence of extracellular K+. Similar conclusions were attained using HEK293 cells loaded with the Na+ sensitive dye Asante NaTRIUM green. Proteolytic cleavage of pig kidney Na+,K+-ATPase indicated that CPZ stabilizes ion interaction with the K+ sites. The distal part of membrane span 10 (M10) of the α-subunit was exposed to trypsin cleavage in the presence of guanidinum ions, which function as Na+ congener at the Na+ specific site. This effect of guanidinium was amplified by treatment with CPZ. Fluorescence of the membrane potential sensitive dye, oxonol VI, was measured following addition of substrates to reconstituted inside-out Na+,K+-ATPase. CPZ increased oxonol VI fluorescence in the absence of K+, reflecting increased Na+ efflux through the pump. Surprisingly, CPZ induced an ATP-independent increase in fluorescence in the presence of high extravesicular K+, likely indicating opening of an intracellular pathway selective for K+. As revealed by the recent crystal structure of the E1.AlF4-.ADP.3Na+ form of the pig kidney Na+,K+-ATPase, movements of M5 of the α-subunit, which regulate ion selectivity, are controlled by the C-terminal tail that extends from M10. We propose that movements of M10 and its cytoplasmic extension is affected by CPZ, thereby regulating ion selectivity and transport through the K+ sites in Na+,K+-ATPase. PMID:24816799

  18. Inhibition of K+ transport through Na+, K+-ATPase by capsazepine: role of membrane span 10 of the α-subunit in the modulation of ion gating.

    PubMed

    Mahmmoud, Yasser A; Shattock, Michael; Cornelius, Flemming; Pavlovic, Davor

    2014-01-01

    Capsazepine (CPZ) inhibits Na+,K+-ATPase-mediated K+-dependent ATP hydrolysis with no effect on Na+-ATPase activity. In this study we have investigated the functional effects of CPZ on Na+,K+-ATPase in intact cells. We have also used well established biochemical and biophysical techniques to understand how CPZ modifies the catalytic subunit of Na+,K+-ATPase. In isolated rat cardiomyocytes, CPZ abolished Na+,K+-ATPase current in the presence of extracellular K+. In contrast, CPZ stimulated pump current in the absence of extracellular K+. Similar conclusions were attained using HEK293 cells loaded with the Na+ sensitive dye Asante NaTRIUM green. Proteolytic cleavage of pig kidney Na+,K+-ATPase indicated that CPZ stabilizes ion interaction with the K+ sites. The distal part of membrane span 10 (M10) of the α-subunit was exposed to trypsin cleavage in the presence of guanidinum ions, which function as Na+ congener at the Na+ specific site. This effect of guanidinium was amplified by treatment with CPZ. Fluorescence of the membrane potential sensitive dye, oxonol VI, was measured following addition of substrates to reconstituted inside-out Na+,K+-ATPase. CPZ increased oxonol VI fluorescence in the absence of K+, reflecting increased Na+ efflux through the pump. Surprisingly, CPZ induced an ATP-independent increase in fluorescence in the presence of high extravesicular K+, likely indicating opening of an intracellular pathway selective for K+. As revealed by the recent crystal structure of the E1.AlF4-.ADP.3Na+ form of the pig kidney Na+,K+-ATPase, movements of M5 of the α-subunit, which regulate ion selectivity, are controlled by the C-terminal tail that extends from M10. We propose that movements of M10 and its cytoplasmic extension is affected by CPZ, thereby regulating ion selectivity and transport through the K+ sites in Na+,K+-ATPase.

  19. Coregulated expression of the Na+/phosphate Pho89 transporter and Ena1 Na+-ATPase allows their functional coupling under high-pH stress.

    PubMed

    Serra-Cardona, Albert; Petrezsélyová, Silvia; Canadell, David; Ramos, José; Ariño, Joaquín

    2014-12-01

    The yeast Saccharomyces cerevisiae has two main high-affinity inorganic phosphate (Pi) transporters, Pho84 and Pho89, that are functionally relevant at acidic/neutral pH and alkaline pH, respectively. Upon Pi starvation, PHO84 and PHO89 are induced by the activation of the PHO regulon by the binding of the Pho4 transcription factor to specific promoter sequences. We show that PHO89 and PHO84 are induced by alkalinization of the medium with different kinetics and that the network controlling Pho89 expression in response to alkaline pH differs from that of other members of the PHO regulon. In addition to Pho4, the PHO89 promoter is regulated by the transcriptional activator Crz1 through the calcium-activated phosphatase calcineurin, and it is under the control of several repressors (Mig2, Nrg1, and Nrg2) coordinately regulated by the Snf1 protein kinase and the Rim101 transcription factor. This network mimics the one regulating expression of the Na(+)-ATPase gene ENA1, encoding a major determinant for Na(+) detoxification. Our data highlight a scenario in which the activities of Pho89 and Ena1 are functionally coordinated to sustain growth in an alkaline environment. PMID:25266663

  20. NMR Evidence for Complexing of Na+ in Muscle, Kidney, and Brain, and by Actomyosin. The Relation of Cellular Complexing of Na+ to Water Structure and to Transport Kinetics

    PubMed Central

    Cope, Freeman W.

    1967-01-01

    The nuclear magnetic resonance (NMR) spectrum of Na+ is suitable for qualitative and quantitative analysis of Na+ in tissues. The width of the NMR spectrum is dependent upon the environment surrounding the individual Na+ ion. NMR spectra of fresh muscle compared with spectra of the same samples after ashing show that approximately 70% of total muscle Na+ gives no detectable NMR spectrum. This is probably due to complexation of Na+ with macromolecules, which causes the NMR spectrum to be broadened beyond detection. A similar effect has been observed when Na+ interacts with ion exchange resin. NMR also indicates that about 60% of Na+ of kidney and brain is complexed. Destruction of cell structure of muscle by homogenization little alters the per cent complexing of Na+. NMR studies show that Na+ is complexed by actomyosin, which may be the molecular site of complexation of some Na+ in muscle. The same studies indicate that the solubility of Na+ in the interstitial water of actomyosin gel is markedly reduced compared with its solubility in liquid water, which suggests that the water in the gel is organized into an icelike state by the nearby actomyosin molecules. If a major fraction of intracellular Na+ exists in a complexed state, then major revisions in most theoretical treatments of equilibria, diffusion, and transport of cellular Na+ become appropriate. PMID:6033590

  1. Synthesis and high temperature transport properties of new quaternary layered selenide NaCuMnSe{sub 2}

    SciTech Connect

    Pavan Kumar, V.; Varadaraju, U.V.

    2014-04-01

    Synthesis and high temperature transport properties of NaCu{sub 1+x}Mn{sub 1−x}Se{sub 2}, (x=0−0.75) a new quaternary layered selenide, are reported. NaCuMnSe{sub 2} crystallizes in a trigonal unit cell with space group of P-3m1 (a=4.1276 Å, c=7.1253 Å). The isovalent substitution of Mn{sup 2+} by Cu{sup 2+} is carried out. All the compositions show semiconducting nature, whereas the Seebeck coefficient increases gradually over the entire measured temperature range. Compositions with x=0 and 0.025 follow thermally activated behavior. With increase in copper concentration the conduction mechanism transforms to 2D variable range hopping (VRH) for x=0.05 and 0.075. - Graphical abstract: Crystal structure of NaCuMnSe{sub 2}. - Highlights: • A new quaternary layered selenide NaCuMnSe{sub 2} is synthesized. • All the compositions show semiconducting nature, whereas the Seebeck coefficient increases gradually over the entire measured temperature range. • Conduction mechanism transforms from thermally activated behavior to 2D variable range hopping with increase in copper concentration.

  2. Investigation of influence of NaOH and NaCl activating solutions on bentonite stabilization in suspension fertilizers

    NASA Astrophysics Data System (ADS)

    Hoffmann, Krystyna; Hoffmann, Józef; Mikła, Daniel; Huculak-Mä Czka, Marta; Skut, Jakub

    2010-05-01

    1. INTRODUCTION Regular plants growth and their metabolic activity are determined by the macro- (C, H, O, N, P, S, K, Ca, Mg) and micronutrients (Fe, Mn, Zn, Cu, B, Mo, Cl, Ni). The role of these elements is very important, the excess as well as the deficiency have the negative influence on their development [1]. In order to increase yields and quality of crops a mineral, organic and mineral-organic fertilizers are applied. In the last years suspension fertilizers have been of great significance, taking the agricultural benefits into consideration. Suspension fertilizers are products of a new generation on account of higher nutrients concentrations than in the majority of other fertilizers, what makes them more efficient. Suspension fertilizers differ from solid fertilizers in more regular distribution on field. Nutrients are more concentrated what is economically relevant on account of the facilitated transportation. Examinations indicated, that nutrients from suspension fertilizers are more available than from solid fertilizers. The high concentration of nutrients in fertilizer is obtained by introducing a substance which holds them regularly in the suspension. Bentonites are the substances used for stabilization of suspension fertilizers most often [2,3]. Bentonites belong to ore of clay minerals, primarily made from minerals of smectite group, montmorillonite especially [4]. Bentonite loams were formulated as a result of Aluminium Silicate-bearing Rocks weathering and subsequent sedimentation in the aqueous environment. Characteristic features of rocks of the smectite group are their ability to absorb water (swelling), to form thixotrophic suspensions which aren't undergoing sedimentation process for a long time; as well as susceptibility to absorb cations and organic substances [4,5]. Therefore investigations have been carried out in order to evaluate the possibility of application of diverse loamy raw materials as suspension stabilizers for fertilizer

  3. Kinetics and transport at AMTEC electrodes. II - Temperature dependence of the interfacial impedance of Na(g)/porous Mo/Na-Beta-double prime alumina

    NASA Technical Reports Server (NTRS)

    Williams, R. M.; Jeffries-Nakamura, B.; Underwood, M. L.; Bankston, C. P.; Kummer, J. T.

    1990-01-01

    The exchange current, transfer coefficient, mass-transport parameters, and electrode capacitance at the Na(g)/porous Mo/Na-Beta-double prime alumina solid electrolyte (BASE) phase boundary have been evaluated from 740 to 1220 K. The transfer coefficient exhibits a value close to 0.5 and the exchange current is dominated by collision frequency, with no significant activation energy. Since the porous Mp-electrode adopts a fairly regular microstructure on the BASE surface, the magnitude of the exchange current of mature electrodes directly depends on the actual contact zone of the porous metal film with the BASE ceramic, and decreases slightly as grain growth occurs. The exchange currents and the mass-transport parameters derived for very porous, thin Mo electrodes indicate that the charge-transfer reaction occurs at a small fraction of the interface. High-frequency limiting capacitance and resistance values due to the interface show potential dependence and a value on the order of 1 F/sq m and 0.1-1.0 Ohm-sq cm.

  4. Intracellular Na+, K+ and Cl- activities in Acheta domesticus Malpighian tubules and the response to a diuretic kinin neuropeptide.

    PubMed

    Coast, Geoffrey M

    2012-08-15

    The mechanism of primary urine production and the activity of a diuretic kinin, Achdo-KII, were investigated in malpighian tubules of Acheta domesticus by measuring intracellular Na(+), K(+) and Cl(-) activities, basolateral membrane voltage (V(b)), fluid secretion and transepithelial ion transport. Calculated electrochemical gradients for K(+) and Cl(-) across the basolateral membrane show they are actively transported into principal cells, and basolateral Ba(2+)-sensitive K(+) channels do not contribute to net transepithelial K(+) transport and fluid secretion. A basolateral Cl(-) conductance was revealed after the blockade of K(+) channels with Ba(2+), and a current carried by the passive outward movement of Cl(-) accounts for the hyperpolarization of V(b) in response to Ba(2+). Ion uptake via Na(+)/K(+)/2Cl(-) cotransport, driven by the inwardly directed Na(+) electrochemical gradient, is thermodynamically feasible, and is consistent with the actions of bumetanide, which reduces fluid secretion and both Na(+) and K(+) transport. The Na(+) gradient is maintained by its extrusion across the apical membrane and by a basolateral ouabain-sensitive Na(+)/K(+)-ATPase. Achdo-KII has no significant effect on the intracellular ion activities or V(b). Electrochemical gradients across the apical membrane were estimated from previously published values for the levels of Na(+), K(+) and Cl(-) in the secreted fluid. The electrochemical gradient for Cl(-) favours passive movement into the lumen, but falls towards zero after stimulation by Achdo-KII. This coincides with a twofold increase in Cl(-) transport, which is attributed to the opening of an apical Cl(-) conductance, which depolarises the apical membrane voltage.

  5. Mechanism of electrically silent Na and Cl transport across the rumen epithelium of sheep.

    PubMed

    Martens, H; Gäbel, G; Strozyk, B

    1991-01-01

    This study was designed to study the mechanism of electroneutral Na and Cl transport across the isolated rumen epithelium of sheep. Net sodium transport (5.75 +/- 0.35 microequiv cm-2 h-1) was significantly higher than the short-circuit current (0.95 +/- 0.08 microequiv cm-2 h-1). Both, net sodium and net chloride transport were markedly reduced by replacement of chloride, bicarbonate and sodium, respectively, but were not changed by the absence of mucosal potassium. Net sodium and net chloride absorption was significantly decreased by 1.0 mM-amiloride. Mucosal addition of bumetanide, furosemide, hydrochlorothiazide or low concentrations of amiloride (less than 0.1 mM) did not change sodium fluxes. These results provide compelling evidence consistent with the presence of Na-H exchange as the predominant electroneutral mechanism for transepithelial sodium movement. The ion replacement studies and data from literature suggest that the Na-H exchange is working in parallel with a Cl-HCO3 exchange although luminal addition of DIDS (4,4'diisothiocyanatostilbene-2,2'-disulphonate, 1 mM) did not significantly influence Cl transport.

  6. Gravity Wave and Turbulence Transport of Heat and Na in the Mesopause Region over the Andes

    NASA Astrophysics Data System (ADS)

    Guo, Yafang; Liu, Alan Z.

    2016-07-01

    The vertical heat and Na fluxes induced by gravity waves and turbulence are derived based on over 600 hours of observations from the Na wind/temperature lidar located at Andes lidar Observatory (ALO), Cerro Pachón, Chile. In the 85-100 km region, the annual mean vertical fluxes by gravity waves show downward heat transport with a maximum of 0.78K m/s at 90 km, and downward Na transport with a maximum of 210 m/s/cm3 at 94km. The maximum cooing rate reaches -24 K/d at 94km. The vertical fluxes have strong seasonal variations, with large differences in magnitudes and altitudes of maximum fluxes between winter and summer. The vertical fluxes due to turbulence eddies are also derived with a novel method that relates turbulence fluctuations of temperature and vertical wind with photon count fluctuations at very high resolution (25 m, 6 s). The results show that the vertical transports are comparable to those by gravity waves and they both play significant roles in the atmospheric thermal structure and constituent distribution. This direct measure of turbulence transport also enables estimate of the eddy diffusivity for heat and constituent in the mesopause region.

  7. Bursts of active transport in living cells.

    PubMed

    Wang, Bo; Kuo, James; Granick, Steve

    2013-11-15

    We show, using a large new data set, that the temporally resolved speed of active cargo transport in living cells follows a scaling law over several decades of time and length. The statistical regularities display a time-averaged shape that we interpret to reflect stress buildup, followed by rapid release. The scaling power law agrees quantitatively with those reported in inanimate systems (jammed colloids and granular media, and magnetic Barkhausen noise), suggesting a common origin in pushing through a crowded environment in a weak force regime. The implied regulation of the speed of active cellular transport due to environmental obstruction results in bursts of speed and acceleration. These findings extend the classical notion of molecular crowding.

  8. Tubuloglomerular and connecting tubuloglomerular feedback during inhibition of various Na transporters in the nephron.

    PubMed

    Wang, Hong; D'Ambrosio, Martin A; Ren, YiLin; Monu, Sumit R; Leung, Pablo; Kutskill, Kristopher; Garvin, Jeffrey L; Janic, Branislava; Peterson, Edward L; Carretero, Oscar A

    2015-05-01

    Afferent (Af-Art) and efferent arterioles resistance regulate glomerular capillary pressure. The nephron regulates Af-Art resistance via: 1) vasoconstrictor tubuloglomerular feedback (TGF), initiated in the macula densa via Na-K-2Cl cotransporters (NKCC2) and 2) vasodilator connecting tubuloglomerular feedback (CTGF), initiated in connecting tubules via epithelial Na channels (ENaC). Furosemide inhibits NKCC2 and TGF. Benzamil inhibits ENaC and CTGF. In vitro, CTGF dilates preconstricted Af-Arts. In vivo, benzamil decreases stop-flow pressure (PSF), suggesting that CTGF antagonizes TGF; however, even when TGF is blocked, CTGF does not increase PSF, suggesting there is another mechanism antagonizing CTGF. We hypothesize that in addition to NKCC2, activation of Na/H exchanger (NHE) antagonizes CTGF, and when both are blocked CTGF dilates Af-Arts and this effect is blocked by a CTGF inhibitor benzamil. Using micropuncture, we studied the effects of transport inhibitors on TGF responses by measuring PSF while increasing nephron perfusion from 0 to 40 nl/min. Control TGF response (-7.9 ± 0.2 mmHg) was blocked by furosemide (-0.4 ± 0.2 mmHg; P < 0.001). Benzamil restored TGF in the presence of furosemide (furosemide: -0.2 ± 0.1 vs. furosemide+benzamil: -4.3 ± 0.3 mmHg; P < 0.001). With furosemide and NHE inhibitor, dimethylamiloride (DMA), increase in tubular flow increased PSF (furosemide+DMA: 2.7 ± 0.5 mmHg, n = 6), and benzamil blocked this (furosemide+DMA+benzamil: -1.1 ± 0.2 mmHg; P < 0.01, n = 6). We conclude that NHE in the nephron decreases PSF (Af-Art constriction) when NKCC2 and ENaC are inhibited, suggesting that in the absence of NKCC2, NHE causes a TGF response and that CTGF dilates the Af-Art when TGF is blocked with NKCC2 and NHE inhibitors. PMID:25715987

  9. Cytokine modulation of Na(+)-dependent glutamine transport across the brush border membrane of monolayers of human intestinal Caco-2 cells.

    PubMed Central

    Souba, W W; Copeland, E M

    1992-01-01

    Previous studies have demonstrated that Na(+)-dependent brush border glutamine transport is diminished in septic patients. To examine the potential regulation of this decreased transport by endotoxin, cytokines, or glucocorticoids, the human intestinal Caco-2 cell line was studied in vitro. Na(+)-dependent glutamine transport across the apical brush border membrane was assayed in confluent monolayers of differentiated cells that were 10 days old. Uptake of 50 microM glutamine was determined after a 12-hour incubation with varying doses (10 to 1000 U/mL) of tumor necrosis factor-alpha, interleukin-1, interleukin-6, interferon-gamma, and various combinations of these cytokines. Studies were also done in cells incubated with E. coli endotoxin (1 micrograms/mL) or dexamethasone (1 and 10 microM). Endotoxin, tumor necrosis factor, interleukin-1, and interleukin-6 alone and in combination did not significantly reduce Na(+)-dependent glutamine transport across the brush border of Caco-2 cells. Dexamethasone decreased glutamine transport by 20%, but this decrease was not apparent for 48 hours. Interferon consistently decreased glutamine transport by 30%; this was due to a reduction in carrier maximal transport velocity (3427 +/- 783 pmol/mg protein/minute in controls versus 2279 +/- 411 in interferon, p less than 0.05) rather than a change in Km (276 +/- 29 microM in controls versus 333 +/- 74 in interferon, p = not interferon + dexamethasone + tumor necrosis factor + interleukin-1 resulted in a 38% decrease in transport activity. Cytokines and glucocorticoids may work independently and synergistically in regulating Na(+)-dependent brush border glutamine transport in human intestinal cells. Whether these signal molecules play a central role in the cause of the diminished brush border glutamine transport that occurs in septic patients requires further study. PMID:1616390

  10. Lotus tenuis tolerates combined salinity and waterlogging: maintaining O2 transport to roots and expression of an NHX1-like gene contribute to regulation of Na+ transport.

    PubMed

    Teakle, Natasha L; Amtmann, Anna; Real, Daniel; Colmer, Timothy D

    2010-08-01

    Salinity and waterlogging interact to reduce growth for most crop and pasture species. The combination of these stresses often cause a large increase in the rate of Na(+) and Cl(-) transport to shoots; however, the mechanisms responsible for this are largely unknown. To identify mechanisms contributing to the adverse interaction between salinity and waterlogging, we compared two Lotus species with contrasting tolerances when grown under saline (200 mM NaCl) and O(2)-deficient (stagnant) treatments. Measurements of radial O(2) loss (ROL) under stagnant conditions indicated that more O(2) reaches root tips of Lotus tenuis, compared with Lotus corniculatus. Better internal aeration would contribute to maintaining Na(+) and Cl(-) transport processes in roots of L. tenuis exposed to stagnant-plus-NaCl treatments. L. tenuis root Na(+) concentrations after stagnant-plus-NaCl treatment (200 mM) were 17% higher than L. corniculatus, with 55% of the total plant Na(+) being accumulated in roots, compared with only 39% for L. corniculatus. L. tenuis accumulated more Na(+) in roots, presumably in vacuoles, thereby reducing transport to the shoot (25% lower than L. corniculatus). A candidate gene for vacuole Na(+) accumulation, an NHX1-like gene, was cloned from L. tenuis and identity established via sequencing and yeast complementation. Transcript levels of NHX1 in L. tenuis roots under stagnant-plus-NaCl treatment were the same as for aerated NaCl, whereas L. corniculatus roots had reduced transcript levels. Enhanced O(2) transport to roots enables regulation of Na(+) transport processes in L. tenuis roots, contributing to tolerance to combined salinity and waterlogging stresses.

  11. Effects of Pb2+ ions on Na+ transport in the isolated skin of the toad Pleurodema thaul.

    PubMed

    Suwalsky, Mario; Schneider, Carlos; Norris, Beryl; Cárdenas, Hernán

    2004-12-01

    The effects induced by lead ions on the short-circuit current (SCC) and on the potential difference (V) of the toad Pleurodema thaul skin were investigated. Pb2+ applied to the outer (mucosal) surface increased SCC and V and when applied to the inner (serosal) surface decreased both parameters. The stimulatory effect, but not the inhibitory action, was reversible after washout of the metal ion. The amiloride test showed that the increase was due principally to stimulation of the driving potential for Na+ (V-E(Na+)) and that inhibition was accompanied by a reduction in the V-E(Na+) and also by a significant decrease in skin resistance indicating possible disruption of membrane and/or cell integrity. The effect of noradrenaline was increased by outer and decreased by inner administration of Pb2+. The results suggest that mucosal Pb2+ activates toad skin ion transport by stimulating the V-E(Na+) and that serosal Pb2+, with easier access to membrane and cellular constituents, inactivates this mechanism, revealing greater toxicity when applied to the inner surface of the skin. PMID:15689109

  12. Inhibition of sodium intestinal transport and mucosal (Na+-K+)-ATPase in experimental Fanconi syndrome.

    PubMed

    Wapnir, R A; Exeni, R A; McVicar, M; De Rosas, R J; Lifshitz, F

    1975-11-01

    The administration of 1.5 or 9.0 mmoles/kg ip of maleate to rats induced, in addition to renal alterations similar to those occurring in the Fanconi syndrome, a decline in the intestinal mucosa (Na+-K+)-ATPase with a simultaneous decrease in sodium intestinal transport and an increase in potassium absorption. Further differences in the behavior of the two electrolytes were observed when the concentration of sodium in the perfusates was altered. No changes occurred in amino acid or glucose transport in experimental animals.

  13. Parasympathetic control of Na, K transport in perfused submaxillary duct of the rat.

    PubMed

    Schneyer, L H

    1977-07-01

    The effects of stimulating the parasympathetic innervation to rat submaxillary gland on ductal transport of Na, K, water, and transepithelial PD, were tested in the main excretory duct during perfusion through its lumen. During nerve stimulation, transepithelial PD was consistently decreased, usually by about 15 mV, and this decrease could be blocked by atropine but not by adrenergic blocking agents. Net flux of Na, K, or water was not significantly changed during stimulation. One-way flux of Na from the lumen also was unaffected. The decrease in PD during stimulation was not affected by substituting isethionate for Cl or increasing [K] in the luminal perfusion medium. It is concluded that parasympathetic effects are exerted on the ductal cells, but that these probably do not involve conductance changes at the luminal membrane.

  14. Effects of chlorpromazine on Na+-K+-ATPase pumping and solute transport in rat hepatocytes

    SciTech Connect

    Van Dyke, R.W.; Scharschmidt, B.F.

    1987-11-01

    Inhibition of Na+-K+-ATPase and sodium-dependent bile acid transport has been suggested as a mechanism for the cholestasis produced by certain drugs such as chlorpromazine. We examined the effects of chlorpromazine (and in selected studies, two of its metabolites) on Na+-K+-ATPase cation pumping (ouabain-suppressible /sup 86/Rb uptake), exchangeable intracellular sodium content, membrane potential (assessed by /sup 36/Cl- distribution), and sodium-dependent transport of taurocholate and alanine in primary cultures of rat hepatocytes. Chlorpromazine (10-300 microM), 7,8-dihydroxychlorpromazine (10-300 microM), and ouabain (0.1-2 mM), but not chlorpromazine sulfoxide, produced a concentration-dependent decrease in Na+-K+-ATPase cation pumping and an increase in intracellular sodium content. Chlorpromazine (100 microM) and ouabain (0.75 mM) also modestly decreased hepatocyte membrane potential. In further studies, chlorpromazine (75 and 100 microM) and ouabain (0.1, 0.5, and 0.75 mM) decreased initial sodium-dependent uptake rates of taurocholate and alanine by 18-63%. Although the steady-state intracellular content of alanine was decreased 25-53% by both agents, chlorpromazine increased the steady-state content of taurocholate by 171% and decreased taurocholate efflux, apparently related to partitioning of taurocholate into a large, slowly turning over intracellular pool. These studies provide direct evidence that chlorpromazine inhibits Na+-K+-ATPase cation pumping in intact cells and that partial inhibition of Na+-K+-ATPase cation pumping is associated with a reduction of both the electrochemical sodium gradient and sodium-dependent solute transport. These effects of chlorpromazine may contribute to chlorpromazine-induced cholestasis in animals and humans.

  15. Electrophysiological characterization of human and mouse sodium-dependent citrate transporters (NaCT/SLC13A5) reveal species differences with respect to substrate sensitivity and cation dependence.

    PubMed

    Zwart, Ruud; Peeva, Polina M; Rong, James X; Sher, Emanuele

    2015-11-01

    The citric acid cycle intermediate citrate plays a crucial role in metabolic processes such as fatty acid synthesis, glucose metabolism, and β-oxidation. Citrate is imported from the circulation across the plasma membrane into liver cells mainly by the sodium-dependent citrate transporter (NaCT; SLC13A5). Deletion of NaCT from mice led to metabolic changes similar to caloric restriction; therefore, NaCT has been proposed as an attractive therapeutic target for the treatment of obesity and type 2 diabetes. In this study, we expressed mouse and human NaCT into Xenopus oocytes and examined some basic functional properties of those transporters. Interestingly, striking differences were found between mouse and human NaCT with respect to their sensitivities to citric acid cycle intermediates as substrates for these transporters. Mouse NaCT had at least 20- to 800-fold higher affinity for these intermediates than human NaCT. Mouse NaCT is fully active at physiologic plasma levels of citrate, but its human counterpart is not. Replacement of extracellular sodium by other monovalent cations revealed that human NaCT was markedly less dependent on extracellular sodium than mouse NaCT. The low sensitivity of human NaCT for citrate raises questions about the translatability of this target from the mouse to the human situation and raises doubts about the validity of this transporter as a therapeutic target for the treatment of metabolic diseases in humans.

  16. Expression of rat liver Na+/L-alanine co-transport in Xenopus laevis oocytes. Effect of glucagon in vivo.

    PubMed Central

    Palacin, M; Werner, A; Dittmer, J; Murer, H; Biber, J

    1990-01-01

    Poly(A)+ RNA (mRNA) isolated from rat liver was injected into Xenopus laevis oocytes, and expression of Na+/L-alanine transport was assayed by measuring Na(+)-dependent uptake of L-[3H]alanine. Expression of Na+/L-alanine transport was detected 3-7 days after mRNA injection, and was due to an increment of the Na(+)-dependent component. After injection of 40 ng of total mRNA, Na(+)-dependent uptake of L-alanine was 2.5-fold higher than in water-injected oocytes. In contrast with Na+/L-alanine transport by water-injected oocytes, expressed Na+/L-alanine transport was inhibited by N-methylaminoisobutyric acid, was inhibited by an extracellular pH of 6.5 and was saturated at approx. 1 mM-L-alanine. After sucrose-density-gradient fractionation, highest expression of Na+/L-alanine uptake was observed with mRNA of 1.9-2.5 kb in length. Compared with mRNA isolated from control rats, mRNA isolated from glucagon-treated rats showed a approx. 2-fold higher expression of Na+/L-alanine transport. The results demonstrate that both liver Na+/L-alanine transport systems (A and ASC) can be expressed in X. laevis oocytes. Furthermore, the data obtained with mRNA isolated from glucagon-treated rats suggest that glucagon regulates liver Na+/L-alanine transport (at least in part) via the availability of the corresponding mRNA. Images Fig. 6. PMID:2396979

  17. Volume regulation of intestinal cells of echinoderms: Putative role of ion transporters (Na(+)/K(+)-ATPase and NKCC).

    PubMed

    Castellano, Giovanna C; Souza, Marta M; Freire, Carolina A

    2016-11-01

    Echinoderms are exclusively marine osmoconformer invertebrates. Some species occupy the challenging intertidal region. Upon salinity changes, the extracellular osmotic concentration of these animals also varies, exposing tissues and cells to osmotic challenges. Cells and tissues may then respond with volume regulation mechanisms, which involve transport of ions and water into and/or out of the cells, through ion transporters, such as the Na(+)/K(+)-ATPase and NKCC. The goal of this study was to relate the cell volume regulation capacity of echinoderm intestinal cells Na(+)/K(+)-ATPase and NKCC activities, in three echinoderm species: Holothuria grisea, Arbacia lixula, and Echinometra lucunter. Isolated cells of these species displayed some control of their cell volume upon exposure to anisosmotic media (isolated intestinal cells, calcein fluorescence as indicator of volume change), with a distinct higher capacity shown by H. grisea, which did not swell even upon 50% hyposmotic shock. The holothuroid cells showed indirect evidence (effect of furosemide) of the participation of NKCC in this process, with a secretory function, and of a secondary role by the NKA (effect of ouabain). Other mechanisms are probably responsible for this function in the urchins. Variable expression of these transporters, and others not examined here, may to some extent account for the variability in cell volume regulation capacity in echinoderm cells.

  18. Osmotic activation of a Na(+)-dependent Cl-/HCO3- exchanger.

    PubMed

    Reusch, H P; Lowe, J; Ives, H E

    1995-01-01

    In many systems, osmotically induced cell shrinkage activates the Na+/H+ exchanger. To assess the role of H(+)-extruding transporters in the response to osmotic shrinkage in vascular smooth muscle (VSM) and Chinese hamster ovary (CHO) cells, intracellular pH (pHi) was measured with 2',7'-bis(carboxy-ethyl)-5(6)- carboxyfluorescein-acetoxymethyl ester (BCECF-AM) after exposing cells to hypertonic medium. In nominally HCO(3-)-free medium, addition of 200 mM sucrose caused pHi to increase 0.33 pH unit on average in VSM cells but only 0.13 pH unit in CHO cells. Permeant solutes failed to increase pHi significantly. Cytochalasin B (1-20 microM), colchicine (1-10 microM), Ca2+ removal, and downregulation of protein kinase C activity did not affect osmotic activation of H+ extrusion in either cell type. Additional work was carried out to determine why osmotic activation of H+ extrusion was less in CHO than in VSM cells. In CHO cells, the osmotically induced delta pHi was only weakly sensitive to amiloride, suggesting that osmotic forces may activate an H+ transport system other than Na+/H+ exchange. In the presence of 10 mM HCO3-, osmotically induced delta pHi decreased by 60% in VSM cells but increased by 50% in CHO cells compared with the delta pHi in HCO(3-)-free medium. Lastly, removal of extracellular Cl- did not affect osmotically induced delta pHi in VSM cells but completely abolished the response in CHO cells. We conclude that in VSM cells osmotically induced changes in pHi are mediated by Na+/H+ exchange, whereas in CHO cells they are most likely mediated by a Na(+)-dependent Cl-/HCO3- exchanger. PMID:7840143

  19. p-aminohippurate transport in the airways: Role of Na sup + and HCO sub 3 -

    SciTech Connect

    Cloutier, M.M. )

    1989-12-01

    The role of Na{sup +} and HCO{sub 3}- in the transport of p-aminohippurate (PAH) across the canine tracheal epithelium was investigated using Ussing chamber techniques and radiolabeled PAH. Under control conditions, net PAH absorption or a tendency toward net PAH absorption was observed. Neither amiloride (10(-4) M), furosemide (10(-3) M), ouabain (2 x 10(-4) M), nor Na+ substitution of the Ringer solution with choline had any effect on unidirectional PAH fluxes. When the Ringer solution was replaced with a HCO{sub 3}(-)-free solution, net PAH absorption was consistently observed. In HCO{sub 3}(-)-free experiments, unidirectional PAH absorptive fluxes were inhibited by mucosal addition of either of the stilbene derivatives, 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS, 10(-4) M) or 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS, 10(-4) M). DIDS was more effective than SITS and was also effective in inhibiting PAH absorption in tissues bathed in Ringer solution. Submucosal DIDS or SITS had no effect on PAH fluxes either in HCO{sub 3}(-)-free or Ringer experiments. We conclude that PAH transport in canine tracheal epithelium occurs by a HCO{sub 3}(-)-PAH exchange process located on the luminal membrane. PAH transport is not Na{sup +} dependent but is inhibited by both DIDS and SITS.

  20. Methods for stable recording of short-circuit current in a Na+-transporting epithelium

    PubMed Central

    Gondzik, Veronika

    2011-01-01

    Epithelial Na+ transport as measured by a variety of techniques, including the short-circuit current technique, has been described to exhibit a “rundown” phenomenon. This phenomenon manifests as time-dependent decrease of current and resistance and precludes the ability to carry out prolonged experiments aimed at examining the regulation of this transport. We developed methods for prolonged stable recordings of epithelial Na+ transport using modifications of the short-circuit current technique and commercial Ussing-type chambers. We utilize the polarized MDCK cell line expressing the epithelial Na+ channel (ENaC) to describe these methods. Briefly, existing commercial chambers were modified to allow continuous flow of Ringer solution and precise control of such flow. Chamber manifolds and associated plumbing were modified to allow precise temperature clamp preventing temperature oscillations. Recording electrodes were modified to eliminate the use of KCl and prevent membrane depolarization from KCl leakage. Solutions utilized standard bicarbonate-based buffers, but all gasses were prehydrated to clamp buffer osmolarity. We demonstrate that these modifications result in measurements of current and resistance that are stable for at least 2 h. We further demonstrate that drifts in osmolarity similar to those obtained before prior to our modifications can lead to a decrease of current and resistance similar to those attributed to rundown. PMID:21451104

  1. Electrophoretic Transport of Na(+) and K(+) Ions Within Cyclic Peptide Nanotubes.

    PubMed

    Carvajal-Diaz, Jennifer A; Cagin, Tahir

    2016-08-18

    One of the most important applications of cyclic peptide nanotubes (CPNTs) is their potential to be used as artificial ion channels. Natural ion channels are large and complex membrane proteins, which are very expensive, difficult to isolate, and sensible to denaturation; for this reason, artificial ion channels are an important alternative, as they can be produced by simple and inexpensive synthetic chemistry paths, allowing manipulation of properties and enhancement of ion selectivity properties. Artificial ion channels can be used as component in molecular sensors and novel therapeutic agents. Here, the electrophoretic transport of Na(+) and K(+) ions within cyclic peptide nanotubes is investigated by using molecular dynamic simulations. The effect of electric field in the stability of peptide nanotubes was studied by calculating the root mean square deviation curves. Results show that the stability for CPNTs decreases for higher electric fields. Selective transport of cations within the hydrophilic tubes was observed and the negative Cl(-) ions did not enter the peptide nanotubes during the simulation. Radial distribution functions were calculated to describe structural properties and coordination numbers and changes in the first and second hydration shell were observed for the transport of Na(+) and K(+) inside of cyclic peptide nanotubes. However, no effect on coordination number was observed. Diffusion coefficients were calculated from the mean square deviation curves and the Na(+) ion showed higher mobility than the K(+) ion as observed in equivalent experimental studies. The values for diffusion coefficients are comparable with previous calculations in protein channels of equivalent sizes. PMID:27448165

  2. Molecular characterization of V59E NIS, a Na+/I- symporter mutant that causes congenital I- transport defect.

    PubMed

    Reed-Tsur, Mia D; De la Vieja, Antonio; Ginter, Christopher S; Carrasco, Nancy

    2008-06-01

    I(-) is actively transported into thyrocytes via the Na+/I(-) symporter (NIS), a key glycoprotein located on the basolateral plasma membrane. The cDNA encoding rat NIS was identified in our laboratory, where an extensive structure/function characterization of NIS is being conducted. Several NIS mutants have been identified as causes of congenital I(-) transport defect (ITD), including V59E NIS. ITD is characterized by low thyroid I(-) uptake, low saliva/plasma I(-) ratio, hypothyroidism, and goiter and may cause mental retardation if untreated. Studies of other ITD-causing NIS mutants have revealed valuable information regarding NIS structure/function. V59E NIS was reported to exhibit as much as 30% of the activity of wild-type NIS. However, this observation was at variance with the patients' phenotype of total lack of activity. We have thoroughly characterized V59E NIS and studied several amino acid substitutions at position 59. We demonstrated that, in contrast to the previous report, V59E NIS is inactive, although it is properly targeted to the plasma membrane. Glu and all other charged amino acids or Pro at position 59 also yielded nonfunctional NIS proteins. However, I(-) uptake was rescued to different degrees by the other substitutions. Although the Km values for Na+ and I(-) were not altered in these active mutants, we found that the structural requirement for NIS function at position 59 is a neutral, helix-promoting amino acid. This result suggests that the region that contains V59 may be involved in intramembrane helix-helix interactions during the transport cycle without being in direct contact with the substrates. PMID:18339708

  3. Cyclic nucleotide gated channel 10 negatively regulates salt tolerance by mediating Na+ transport in Arabidopsis.

    PubMed

    Jin, Yakang; Jing, Wen; Zhang, Qun; Zhang, Wenhua

    2015-01-01

    A number of cyclic nucleotide gated channel (CNGC) genes have been identified in plant genomes, but their functions are mainly undefined. In this study, we identified the role of CNGC10 in the response of Arabidopsis thaliana to salt stress. The cngc10 T-DNA insertion mutant showed greater tolerance to salt than wild-type A. thaliana during seed germination and seedling growth. The cngc10 mutant accumulated less Na(+) and K(+), but not less Ca(2+), in shoots in response to salt stress. By contrast, overexpression of CNGC10 resulted in greater sensitivity to salt stress, and complementation of this gene recovered salt sensitivity. In response to salt stress, heterologous expression of CNGC10 in the Na(+) sensitive yeast mutant strain B31 inhibited growth due to accumulation of Na(+) at a rate greater than that of yeast transformed with an empty vector. Quantitative RT-PCR analysis demonstrated that CNGC10 was expressed mainly in roots and flowers. GUS analysis of a root cross section indicated that CNGC10 was expressed mainly in the endodermis and epidermis. Furthermore, the expression of CNGC10 in roots was dramatically inhibited by exposure to 200 mM NaCl for 6 h. These data suggest that CNGC10 negatively regulates salt tolerance in A. thaliana and may be involved in mediating Na(+) transport. PMID:25416933

  4. Cyclic nucleotide gated channel 10 negatively regulates salt tolerance by mediating Na+ transport in Arabidopsis.

    PubMed

    Jin, Yakang; Jing, Wen; Zhang, Qun; Zhang, Wenhua

    2015-01-01

    A number of cyclic nucleotide gated channel (CNGC) genes have been identified in plant genomes, but their functions are mainly undefined. In this study, we identified the role of CNGC10 in the response of Arabidopsis thaliana to salt stress. The cngc10 T-DNA insertion mutant showed greater tolerance to salt than wild-type A. thaliana during seed germination and seedling growth. The cngc10 mutant accumulated less Na(+) and K(+), but not less Ca(2+), in shoots in response to salt stress. By contrast, overexpression of CNGC10 resulted in greater sensitivity to salt stress, and complementation of this gene recovered salt sensitivity. In response to salt stress, heterologous expression of CNGC10 in the Na(+) sensitive yeast mutant strain B31 inhibited growth due to accumulation of Na(+) at a rate greater than that of yeast transformed with an empty vector. Quantitative RT-PCR analysis demonstrated that CNGC10 was expressed mainly in roots and flowers. GUS analysis of a root cross section indicated that CNGC10 was expressed mainly in the endodermis and epidermis. Furthermore, the expression of CNGC10 in roots was dramatically inhibited by exposure to 200 mM NaCl for 6 h. These data suggest that CNGC10 negatively regulates salt tolerance in A. thaliana and may be involved in mediating Na(+) transport.

  5. Alveolar epithelial type I cells contain transport proteins and transport sodium, supporting an active role for type I cells in regulation of lung liquid homeostasis

    PubMed Central

    Johnson, Meshell D.; Widdicombe, Jonathan H.; Allen, Lennell; Barbry, Pascal; Dobbs, Leland G.

    2002-01-01

    Transport of lung liquid is essential for both normal pulmonary physiologic processes and for resolution of pathologic processes. The large internal surface area of the lung is lined by alveolar epithelial type I (TI) and type II (TII) cells; TI cells line >95% of this surface, TII cells <5%. Fluid transport is regulated by ion transport, with water movement following passively. Current concepts are that TII cells are the main sites of ion transport in the lung. TI cells have been thought to provide only passive barrier, rather than active, functions. Because TI cells line most of the internal surface area of the lung, we hypothesized that TI cells could be important in the regulation of lung liquid homeostasis. We measured both Na+ and K+ (Rb+) transport in TI cells isolated from adult rat lungs and compared the results to those of concomitant experiments with isolated TII cells. TI cells take up Na+ in an amiloride-inhibitable fashion, suggesting the presence of Na+ channels; TI cell Na+ uptake, per microgram of protein, is ≈2.5 times that of TII cells. Rb+ uptake in TI cells was ≈3 times that in TII cells and was inhibited by 10−4 M ouabain, the latter observation suggesting that TI cells exhibit Na+-, K+-ATPase activity. By immunocytochemical methods, TI cells contain all three subunits (α, β, and γ) of the epithelial sodium channel ENaC and two subunits of Na+-, K+-ATPase. By Western blot analysis, TI cells contain ≈3 times the amount of αENaC/μg protein of TII cells. Taken together, these studies demonstrate that TI cells not only contain molecular machinery necessary for active ion transport, but also transport ions. These results modify some basic concepts about lung liquid transport, suggesting that TI cells may contribute significantly in maintaining alveolar fluid balance and in resolving airspace edema. PMID:11842214

  6. Physiological adjustment to salt stress in Jatropha curcas is associated with accumulation of salt ions, transport and selectivity of K+, osmotic adjustment and K+/Na+ homeostasis.

    PubMed

    Silva, E N; Silveira, J A G; Rodrigues, C R F; Viégas, R A

    2015-09-01

    This study assessed the capacity of Jatropha curcas to physiologically adjust to salinity. Seedlings were exposed to increasing NaCl concentrations (25, 50, 75 and 100 mm) for 15 days. Treatment without NaCl was adopted as control. Shoot dry weight was strongly reduced by NaCl, reaching values of 35% to 65% with 25 to 100 mm NaCl. The shoot/root ratio was only affected with 100 mm NaCl. Relative water content (RWC) increased only with 100 mm NaCl, while electrolyte leakage (EL) was much enhanced with 50 mm NaCl. The Na(+) transport rate to the shoot was more affected with 50 and 100 mm NaCl. In parallel, Cl(-) transport rate increased with 75 and 100 mm NaCl, while K(+) transport rate fell from 50 mm to 100 mm NaCl. In roots, Na(+) and Cl(-) transport rates fell slightly only in 50 mm (to Na(+)) and 50 and 100 mm (to Cl(-)) NaCl, while K(+) transport rate fell significantly with increasing NaCl. In general, our data demonstrate that J. curcas seedlings present changes in key physiological processes that allow this species to adjust to salinity. These responses are related to accumulation of Na(+) and Cl(-) in leaves and roots, K(+)/Na(+) homeostasis, transport of K(+) and selectivity (K-Na) in roots, and accumulation of organic solutes contributing to osmotic adjustment of the species. PMID:25865670

  7. A pharmacological analysis of high-affinity sodium transport in barley (Hordeum vulgare L.): a 24Na+/42K+ study

    PubMed Central

    Schulze, Lasse M.; Britto, Dev T.; Li, Mingyuan; Kronzucker, Herbert J.

    2012-01-01

    Soil sodium, while toxic to most plants at high concentrations, can be beneficial at low concentrations, particularly when potassium is limiting. However, little is known about Na+ uptake in this ‘high-affinity’ range. New information is provided here with an insight into the transport characteristics, mechanism, and ecological significance of this phenomenon. High-affinity Na+ and K+ fluxes were investigated using the short-lived radiotracers 24Na and 42K, under an extensive range of measuring conditions (variations in external sodium, and in nutritional and pharmacological agents). This work was supported by electrophysiological, compartmental, and growth analyses. Na+ uptake was extremely sensitive to all treatments, displaying properties of high-affinity K+ transporters, K+ channels, animal Na+ channels, and non-selective cation channels. K+, NH4+NH4+, and Ca2+ suppressed Na+ transport biphasically, yielding IC50 values of 30, 10, and <5 μM, respectively. Reciprocal experiments showed that K+ influx is neither inhibited nor stimulated by Na+. Sodium efflux constituted 65% of influx, indicating a futile cycle. The thermodynamic feasibility of passive channel mediation is supported by compartmentation and electrophysiological data. Our study complements recent advances in the molecular biology of high-affinity Na+ transport by uncovering new physiological foundations for this transport phenomenon, while questioning its ecological relevance. PMID:22268152

  8. The importance of company: Na+ and Cl- influence substrate interaction with SLC6 transporters and other proteins.

    PubMed

    Reith, M E A; Zhen, J; Chen, N

    2006-01-01

    SLC6 transporters, which include transporters for gamma-aminobutyric acid (GABA), norepinephrine, dopamine, serotonin, glycine, taurine, L-proline, creatine, betaine, and neutral cationic amino acids, require Na+ and Cl- for their function, and this review covers the interaction between transporters of this family with Na+ and Cl- from a structure-function standpoint. Because detailed structure-function information regarding ion interactions with SLC6 transporters is limited, we cover other proteins cotransporting Na+ or Cl- with substrate (SLClA2, PutP, SLC5A1, melB), or ion binding to proteins in general (rhodanese, ATPase, LacY, thermolysine, angiotensin-converting enzyme, halorhodopsin, CFTR). Residues can be involved in directly binding Na+ or Cl-, in coupling ion binding to conformational changes in transporter, in coupling Na+ or Cl- movement to transport, or in conferring ion selectivity. Coordination of ions can involve a number of residues, and portions of the substrate and coupling ion binding sites can be distal in space in the tertiary structure of the transporter, with other portions that are close in space thought to be crucial for the coupling process. The reactivity with methanethiosulfonate reagents of cysteines placed in strategic positions in the transporter provides a readout for conformational changes upon ion or substrate binding. More work is needed to establish the relationships between ion interactions and oligomerization of SLC6 transporters.

  9. Comparison Of NaI And HPGe Minimum Detectable Activities

    SciTech Connect

    Bailey, Paul

    2002-11-30

    The Minimum Detectable Activity of a 76 mm by 76 mm (3" by 3") sodium iodide (NaI) crystal and 18 %, 42 % and 68 % efficient HPGe detectors were calculated and compared for gamma-ray spectrometry with count times in the range of 1 second to 15 minutes. All cases were for in situ measurements with a surface distribution source and a detector height of 1 meter. The radionuclides considered were 137Cs and 60Co.

  10. Hormonal modulation of Na+ transport in rat fetal distal lung epithelial cells

    PubMed Central

    Ramminger, S J; Inglis, S K; Olver, R E; Wilson, S M

    2002-01-01

    Isolated rat fetal distal lung epithelial (FDLE) cells were cultured (≈48 h) on permeable supports in medium devoid of hormones and growth factors whilst PO2 was maintained at the level found in either the fetal (23 mmHg) or the postnatal (100 mmHg) alveolar regions. The cells became incorporated into epithelial layers that generated a basal short-circuit current (ISC) attributable to spontaneous Na+ absorption. Cells at neonatal PO2 generated larger currents than did cells at fetal PO2, indicating that this Na+ transport process is oxygen sensitive. Irrespective of PO2, isoprenaline failed to elicit a discernible change in ISC, demonstrating that β-adrenoceptor agonists do not stimulate Na+ transport under these conditions. However, isoprenaline did elicit cAMP accumulation in these cells, indicating that functionally coupled β-adrenoceptors are present. Further experiments showed that isoprenaline did increase ISC in cells treated (24 h) with a combination of tri-iodothyronine (T3, 10 nm) and dexamethasone (200 nm). Studies of basolaterally permeabilised cells showed that these hormones are essential for the isoprenaline-evoked increase in the apical membrane's Na+ conductance (GNa), whereas isoprenaline-evoked changes in apical Cl− conductance (GCl) can occur in both control and hormone-treated cells. Irrespective of their hormonal status, FDLE cells thus express β-adrenoceptors that are functionally coupled to adenylate cyclase, and allow β-adrenoceptor agonists to modulate the apical membrane's anion conductance. However, T3 and dexamethasone are needed if these receptors are to exert control over GNa. These hormones may thus play an important role in the functional maturation of the lung by allowing β-adrenoceptor-mediated control over epithelial Na+ channels in the apical plasma membrane. PMID:12381827

  11. Sodium dependency of active chloride transport across isolated fish skin (Gillichthys mirabilis).

    PubMed Central

    Marshall, W S

    1981-01-01

    1. The effects of thiocyanate, ouabain, ion-substituted Ringer solution and electrochemical gradients on Na+ and Cl- transport were examined using the isolated skin of the marine teleost, Gillichthys mirabilis. 2. Bilateral replacement of Na+ with choline in the bathing solutions reduces net Cl- flux by 93%, indicating that active Cl- transport by the skin is Na-dependent. 3. Thiocyanate inhibits short-circuit current with an ED50 of 6.4 x 10(-4)M, and, at 10(-2)M, decreases Cl-efflux, influx, net flux and short-circuit current by 68, 33, 74 and 81%, respectively. 4. Ouabain (10(-5)M) reduces Cl- efflux and net flux by 56 and 86%, respectively, indicating that the Cl- transport requires Na,K-ATPase. 5. Subsequent addition of thiocyanate to ouabain-treated skin reduces Cl- efflux, net flux and short-circuit current, suggesting that the two agents operate at different sites involved in Cl- transport. 6. Unilateral substitution of gluconate for Cl- on the serosal side does not affect Cl- influx, indicating that Cl- passive transport is via Fickean diffusion, not Cl-Cl exchange diffusion. 7. The addition of NaCl to the mucosal side, which mimics the in vivo sea-water condition, increases Cl- influx and transepithelial potential and decreases tissue resistance. The net flux (secretion) of Cl- with hypertonic saline on the mucosal side (0.51 +/- 0.06 muequiv/cm2 . hr) demonstrates that the skin could secrete Cl- in vivo. 8. Na+ fluxes across the skin are passive, as the observed flux ration (efflux/influx) is similar to that predicted by the Ussing-Teorell equation under both closed- and open-circuit conditions. 9. The permeability ratio (PNa:PCl) in approximately 5.4:1.0, indicating that the skin is more permeable to Na+, and that at least part of the serosa-positive transepithelial potential may be a Na+ diffusion potential. 10. The results suggest that Cl- secretion by Gillichthys skin is secondary active transport involving Na,K-ATPase and serosal Na+. PMID:7320911

  12. The difference in sensitivity to cardiac steriods of (Na+ + K+)-stimulated ATPase and amino acid transport in the intestinal mucosa of the rat and other species

    PubMed Central

    Robinson, J. W. L.

    1970-01-01

    1. The effect of various cardioactive steroids on the activity of a microsomal (Na+ + K+)-activated ATPase from rat intestinal mucosa has been studied and compared with their effects on L-phenylalanine and D-galactose transport by rings of rat intestine in vitro. A similar comparison between the sensitivities to ouabain of microsomal (Na+ + K+)-ATPase and of phenylalanine transport in the intestines of the mouse, guinea-pig and toad has been made. 2. The rat intestinal enzyme is 50% inhibited by a concentration of 1 × 10-4M ouabain, 1 × 10-5M scillaren A and 4 × 10-6M scilliroside. At concentrations which almost completely inhibit the (Na+ + K+)-ATPase activity, these steroids have no effect on the transport of phenylalanine or galactose by the rat intestine. Only at concentrations of 1 × 10-3M are scillaren A and scilliroside able to reduce phenylalanine accumulation significantly, the same concentration of ouabain being effective only in the absence of external potassium ions. Digitoxin, 1 × 10-4M, a comparatively apolar glycoside, had no action on phenylalanine transport in the rat intestine. 3. The effect of ouabain on the (Na+ + K+)-ATPase and phenylalanine transport system in the mouse intestine is completely analogous to its effect on these parameters in the rat. 4. A half-maximal inhibition of guinea-pig intestinal (Na+ + K+)-ATPase by ouabain occurs at an inhibitor concentration of 2 × 10-6M, but phenylalanine transport by this tissue is only half-maximally reduced at a concentration of 3 × 10-5M. Similarly, in the rabbit intestine, there appears to be a difference of an order of magnitude between the sensitivities of the two parameters. 5. In the toad, 50% inhibition of the enzymic activity is observed at a concentration of 3 × 10-5M ouabain, whereas a concentration of 8 × 10-4M is required to reduce phenylalanine accumulation by one half. 6. These findings are consistent with the suggestion that an (Na+ + K+)-stimulated ATPase is not the only

  13. Na/sup +/-dependent transport of /sup 14/C-L-lysine across bullfrog alveolar epithelium

    SciTech Connect

    Kim, K.J.; Crandall, E.D.

    1986-03-01

    Transepithelial transport of the basic amino acid L-lysine has been studied utilizing the isolated intact bullfrog lung mounted in the Ussing chamber. Lungs were excised from doubly pithed bullfrogs and sandwiched between two hemichambers. /sup 14/C-(U)-L-lysine was added to the upstream reservoir of amphibian Ringer solution, while the tissue was short-circuited. Two lungs from the same animal were used simultaneously to determine the two opposite unidirectional fluxes. Downstream and upstream radioactivities were assayed and used to estimate the apparent permeability (P) of the labeled lysine. Results indicate that the apparent P of /sup 14/C-L-lysine measured in the alveolar (M) to the pleural (S) direction is 19.06 (+- 2.84) x 10/sup -7/ cm/s and P in the S to M direction is 3.29 (+- 0.02) x 10/sup -7/ cm/s. When the 100 mM NaCl in the bath was replaced by 110 mM choline chloride, the flux of /sup 14/C-L-lysine from the alveolar to the pleural side decreased to the same value as that in the opposite direction. The flux from the pleural to the alveolar direction in the absence of Na/sup +/ did not change. These results suggest that the alveolar epithelium exhibits Na/sup +/-dependent amino acid (L-lysine) transport in the M->S, but not in the S->M, direction.

  14. Relationship between sodium-dependent phosphate transporter (NaPi-IIc) function and cellular vacuole formation in opossum kidney cells.

    PubMed

    Shiozaki, Yuji; Segawa, Hiroko; Ohnishi, Saori; Ohi, Akiko; Ito, Mikiko; Kaneko, Ichiro; Kido, Shinsuke; Tatsumi, Sawako; Miyamoto, Ken-ichi

    2015-01-01

    NaPi-IIc/SLC34A3 is a sodium-dependent inorganic phosphate (Pi) transporter in the renal proximal tubules and its mutations cause hereditary hypophosphatemic rickets with hypercalciuria (HHRH). In the present study, we created a specific antibody for opossum SLC34A3, NaPi-IIc (oNaPi-IIc), and analyzed its localization and regulation in opossum kidney cells (a tissue culture model of proximal tubular cells). Immunoreactive oNaPi-IIc protein levels increased during the proliferative phase and decreased during differentiation. Moreover, stimulating cell growth upregulated oNaPi-IIc protein levels, whereas suppressing cell proliferation downregulated oNaPi-IIc protein levels. Immunocytochemistry revealed that endogenous and exogenous oNaPi-IIc proteins localized at the protrusion of the plasma membrane, which is a phosphatidylinositol 4,5-bisphosphate (PIP2) rich-membrane, and at the intracellular vacuolar membrane. Exogenous NaPi-IIc also induced cellular vacuoles and localized in the plasma membrane. The ability to form vacuoles is specific to electroneutral NaPi-IIc, and not electrogenic NaPi-IIa or NaPi-IIb. In addition, mutations of NaPi-IIc (S138F and R468W) in HHRH did not cause cellular PIP2-rich vacuoles. In conclusion, our data anticipate that NaPi-IIc may regulate PIP2 production at the plasma membrane and cellular vesicle formation. PMID:26399350

  15. The Na+ transport in gram-positive bacteria defect in the Mrp antiporter complex measured with 23Na nuclear magnetic resonance.

    PubMed

    Górecki, Kamil; Hägerhäll, Cecilia; Drakenberg, Torbjörn

    2014-01-15

    (23)Na nuclear magnetic resonance (NMR) has previously been used to monitor Na(+) translocation across membranes in gram-negative bacteria and in various other organelles and liposomes using a membrane-impermeable shift reagent to resolve the signals resulting from internal and external Na(+). In this work, the (23)Na NMR method was adapted for measurements of internal Na(+) concentration in the gram-positive bacterium Bacillus subtilis, with the aim of assessing the Na(+) translocation activity of the Mrp (multiple resistance and pH) antiporter complex, a member of the cation proton antiporter-3 (CPA-3) family. The sodium-sensitive growth phenotype observed in a B. subtilis strain with the gene encoding MrpA deleted could indeed be correlated to the inability of this strain to maintain a lower internal Na(+) concentration than an external one. PMID:24139955

  16. Characterisation of neurotransmitter-induced electrolyte transport in cockroach salivary glands by intracellular Ca2+, Na+ and pH measurements in duct cells.

    PubMed

    Hille, Carsten; Walz, Bernd

    2008-02-01

    Ion-transporting acinar peripheral cells in cockroach salivary glands are innervated by dopaminergic and serotonergic fibres, but saliva-modifying duct cells are innervated only by dopaminergic fibres. We used microfluorometry to record intracellular Na+, Ca2+ and H+ concentrations ([Na+]i, [Ca2+]i and pHi) in duct cells of two types of preparation, viz ;lobes' consisting of acini with their duct system and ;isolated ducts' without acini, in order to obtain information about the transporters involved in saliva secretion and/or modification. Our results indicate that (1) stimulation of lobes by dopamine (DA) causes a strong drop of pHi and increases in [Na+]i and [Ca2+]i in duct cells; (2) in contrast, DA stimulation of isolated ducts produces only a small pHi drop and no changes in [Na+]i and [Ca2+]i; (3) pHi and [Ca2+]i changes are also induced in duct cells by serotonin (5-HT) stimulation of lobes, but not isolated ducts; (4) in the absence of CO2/HCO3(-), the DA-induced pH(i) drop is strongly reduced by removal of extracellular Cl(-) or inhibition of the Na+-K+-2Cl(-) cotransporter (NKCC); (5) in the presence of CO2/HCO3(-), the DA-induced pHi drop is not reduced by NKCC inhibition, but rather by inhibition of the Cl(-)/HCO3(-) exchanger (AE), Na+/H+ exchanger (NHE) or carbonic anhydrase. We suggest that DA and 5-HT act predominantly on acinar peripheral cells. Their activity (secretion of primary saliva) seems to cause changes in ion concentrations in duct cells. NKCC and/or AE/NHE activities are necessary for pHi changes in duct cells; we consider that these transporters are involved in the secretion of the NaCl-rich primary saliva.

  17. Electrophysiological analysis of Na+/Pi cotransport mediated by a transporter cloned from rat kidney and expressed in Xenopus oocytes.

    PubMed Central

    Busch, A; Waldegger, S; Herzer, T; Biber, J; Markovich, D; Hayes, G; Murer, H; Lang, F

    1994-01-01

    Phosphate (Pi) reabsorption in renal proximal tubules involves Na+/Pi cotransport across the brush border membrane; its transport rate is influenced by the Na(+)-coupled transport of other solutes as well as by pH. In the present study, we have expressed a cloned rat renal brush border membrane Na+/Pi cotransporter (NaPi-2) in Xenopus laevis oocytes and have analyzed its electrophysiologic properties in voltage- and current-clamp studies. Addition of Pi to Na(+)-containing superfusates resulted in a depolarization of the membrane potential and, in voltage-clamped oocytes, in an inward current (IP). An analysis of the Na+ and/or Pi concentration dependence of IP suggested a Na+/Pi stoichiometry of 3:1. IP was increased by increasing the pH of the superfusate; this phenomenon seems to be mainly related to a lowering of the affinity for Na+ interaction by increasing H+ concentration. The present data suggest that known properties of Pi handling at the tubular/membrane level are "directly" related to specific characteristics of the transport molecule (NaPi-2) involved. Images PMID:8058781

  18. Over-expression of an Na+-and K+-permeable HKT transporter in barley improves salt tolerance.

    PubMed

    Mian, Afaq; Oomen, Ronald J F J; Isayenkov, Stanislav; Sentenac, Hervé; Maathuis, Frans J M; Véry, Anne-Aliénor

    2011-11-01

    Soil salinity is an increasing menace that affects agriculture across the globe. Plant adaptation to high salt concentrations involves integrated functions, including control of Na+ uptake, translocation and compartmentalization. Na+ transporters belonging to the HKT family have been shown to be involved in tolerance to mild salt stress in glycophytes such as Arabidopsis, wheat and rice by contributing to Na+ exclusion from aerial tissues. Here, we have analysed the role of the HKT transporter HKT2;1, which is permeable to K+ and Na+, in barley, a relatively salt-tolerant crop that displays a salt-including behaviour. In Xenopus oocytes, HvHKT2;1 co-transports Na+ and K+ over a large range of concentrations, displaying low affinity for Na+, variable affinity for K+ depending on external Na+ concentration, and inhibition by K+ (K(i) approximately 5 mm). HvHKT2;1 is predominantly expressed in the root cortex. Transcript levels are up-regulated in both roots and shoots by low K+ growth conditions, and in shoots by high Na+ growth conditions. Over-expression of HvHKT2;1 led to enhanced Na+ uptake, higher Na+ concentrations in the xylem sap, and enhanced translocation of Na+ to leaves when plants were grown in the presence of 50 or 100 mm NaCl. Interestingly, these responses were correlated with increased barley salt tolerance. This suggests that one of the factors that limits barley salt tolerance is the capacity to translocate Na+ to the shoot rather than accumulation or compartmentalization of this cation in leaf tissues. Thus, over-expression of HvHKT2;1 leads to increased salt tolerance by reinforcing the salt-including behaviour of barley. PMID:21749504

  19. Human, rat and chicken small intestinal Na+-Cl−-creatine transporter: functional, molecular characterization and localization

    PubMed Central

    Peral, M J; García-Delgado, M; Calonge, M L; Durán, J M; De La Horra, M C; Wallimann, T; Speer, O; Ilundáin, A A

    2002-01-01

    In spite of all the fascinating properties of oral creatine supplementation, the mechanism(s) mediating its intestinal absorption has(have) not been investigated. The purpose of this study was to characterize intestinal creatine transport. [14C]Creatine uptake was measured in chicken enterocytes and rat ileum, and expression of the creatine transporter CRT was examined in human, rat and chicken small intestine by reverse transcription-polymerase chain reaction, Northern blot, in situ hybridization, immunoblotting and immunohistochemistry. Results show that enterocytes accumulate creatine against its concentration gradient. This accumulation was electrogenic, Na+- and Cl−-dependent, with a probable stoichiometry of 2 Na+: 1 Cl−: 1 creatine, and inhibited by ouabain and iodoacetic acid. The kinetic study revealed a Km for creatine of 29 μm. [14C]Creatine uptake was efficiently antagonized by non-labelled creatine, guanidinopropionic acid and cyclocreatine. More distant structural analogues of creatine, such as GABA, choline, glycine, β-alanine, taurine and betaine, had no effect on intestinal creatine uptake, indicating a high substrate specificity of the creatine transporter. Consistent with these functional data, messenger RNA for CRT was detected only in the cells lining the intestinal villus. The sequences of partial clones, and of the full-length cDNA clone, isolated from human and rat small intestine were identical to previously cloned CRT cDNAs. Immunological analysis revealed that CRT protein was mainly associated with the apical membrane of the enterocytes. This study reports for the first time that mammalian and avian enterocytes express CRT along the villus, where it mediates high-affinity, Na+- and Cl−-dependent, apical creatine uptake. PMID:12433955

  20. Inhibition of Na+-Taurocholate Co-transporting Polypeptide-mediated Bile Acid Transport by Cholestatic Sulfated Progesterone Metabolites*

    PubMed Central

    Abu-Hayyeh, Shadi; Martinez-Becerra, Pablo; Sheikh Abdul Kadir, Siti H.; Selden, Clare; Romero, Marta R.; Rees, Myrddin; Marschall, Hanns-Ulrich; Marin, Jose J. G.; Williamson, Catherine

    2010-01-01

    Sulfated progesterone metabolite (P4-S) levels are raised in normal pregnancy and elevated further in intrahepatic cholestasis of pregnancy (ICP), a bile acid-liver disorder of pregnancy. ICP can be complicated by preterm labor and intrauterine death. The impact of P4-S on bile acid uptake was studied using two experimental models of hepatic uptake of bile acids, namely cultured primary human hepatocytes (PHH) and Na+-taurocholate co-transporting polypeptide (NTCP)-expressing Xenopus laevis oocytes. Two P4-S compounds, allopregnanolone-sulfate (PM4-S) and epiallopregnanolone-sulfate (PM5-S), reduced [3H]taurocholate (TC) uptake in a dose-dependent manner in PHH, with both Na+-dependent and -independent bile acid uptake systems significantly inhibited. PM5-S-mediated inhibition of TC uptake could be reversed by increasing the TC concentration against a fixed PM5-S dose indicating competitive inhibition. Experiments using NTCP-expressing Xenopus oocytes confirmed that PM4-S/PM5-S are capable of competitively inhibiting NTCP-mediated uptake of [3H]TC. Total serum PM4-S + PM5-S levels were measured in non-pregnant and third trimester pregnant women using liquid chromatography-electrospray tandem mass spectrometry and were increased in pregnant women, at levels capable of inhibiting TC uptake. In conclusion, pregnancy levels of P4-S can inhibit Na+-dependent and -independent influx of taurocholate in PHH and cause competitive inhibition of NTCP-mediated uptake of taurocholate in Xenopus oocytes. PMID:20177056

  1. Inhibitory Effect of Fluoride on Na+,K+ ATPase Activity in Human Erythrocyte Membrane.

    PubMed

    A, Shashi; G, Meenakshi

    2015-12-01

    The present study was performed to evaluate the role of long-term consumption of excessive fluoride on electrolyte homeostasis and their transporting mechanisms in erythrocytes of subjects afflicted with dental and skeletal fluorosis. A total of 620 adult (20-50 years) Indian residents participated in this study: 258 men and 242 women exposed to high concentrations of fluoride and 120 age and gender-matched control subjects. Erythrocytes were isolated from blood samples, washed, and used for the estimation of intraerythrocyte sodium and potassium concentrations. Na+,K+ ATPase activity was determined spectrophotometrically from a ghost erythrocyte membrane prepared by osmotic lysis. Erythrocyte analytes were correlated with the water and serum fluoride concentrations by Pearson's bivariate correlation and regression analysis. Results indicated a significant increase in intraerythrocyte sodium (F=14306.265, P<0.0001) in subjects from endemic fluorosis study groups as compared to controls. A significant (P<0.05) positive correlation of intracellular sodium was found with water and serum fluoride concentrations. Mean concentration of intraerythrocytic potassium ions showed significant reduction (F=9136.318, P<0.0001) in subjects exposed to fluoride. A significant (P<0.05) negative correlation of potassium ions was noted with water and serum fluoride concentrations. Na+,K+ ATPase activity was significantly declined (F=1572.763, P<0.0001) in subjects exposed to fluoride. A significant (P<0.05) inverse relationship of Na+,K+ ATPase activity was revealed with water and serum fluoride concentrations.

  2. The early and late effects of digoxin treatment on the sodium transport, sodium content and Na+K+- ATPase or erythrocytes.

    PubMed

    Cumberbatch, M; Zareian, K; Davidson, C; Morgan, D B; Swaminathan, R

    1981-06-01

    1 Erythrocyte sodium content, sodium transport (ouabain sensitive sodium flux Eos, and ouabain sensitive efflux rate constant ERCos) sodium, potassium activated ouabain sensitive adenosine triphosphatase (Na+K+ATPase) and plasma digoxin were measured in patients during acute digitalisation and in patients who were on long-term digoxin treatment. 2 In the six patients who were studied during digitalisation, the ERCos and Na+K+ATPase activity decreased and erythrocyte sodium content increased during days 2-4 treatment, but there was no change in Eos. 3 In 39 patients on long term digoxin therapy (2-119 months) the erythrocyte sodium content was normal, but the erythrocyte Na+K+ATPase activity was higher than the control group. When the results from these 39 patients were divided according to the duration of treatment it was found that the erythrocyte sodium content was higher in patients treated for 2-4 months than in patients treated for longer periods and the erythrocyte Na+K+ATPase activity increased with duration of treatment. In eight patients (duration of treatment greater than 29 months) in whom ERCos and Eos were measured, ERCos and Eos were higher than the control group. 4 The results suggest that the effects of digoxin on erythrocytes which occur during acute digoxin treatment do not persist in the long term. 5 The possible explanation for the higher ERCos, Eos and Na+K+ATPase activity in patients treated with digoxin for more than 2 months is discussed. PMID:6268133

  3. Selective and Reversible Inhibition of Active CO2 Transport by Hydrogen Sulfide in a Cyanobacterium 1

    PubMed Central

    Espie, George S.; Miller, Anthony G.; Canvin, David T.

    1989-01-01

    The active transport of CO2 in the cyanobacterium Synechococcus UTEX 625 was inhibited by H2S. Treatment of the cells with up to 150 micromolar H2S + HS− at pH 8.0 had little effect on Na+-dependent HCO3− transport or photosynthetic O2 evolution, but CO2 transport was inhibited by more than 90%. CO2 transport was restored when H2S was removed by flushing with N2. At constant total H2S + HS− concentrations, inhibition of CO2 transport increased as the ratio of H2S to HS− increased, suggesting a direct role for H2S in the inhibitory process. Hydrogen sulfide does not appear to serve as a substrate for transport. In the presence of H2S and Na+ -dependent HCO3− transport, the extracellular CO2 concentration rose considerably above its equilibrium level, but was maintained far below its equilibrium level in the absence of H2S. The inhibition of CO2 transport, therefore, revealed an ongoing leakage from the cells of CO2 which was derived from the intracellular dehydration of HCO3− which itself had been recently transported into the cells. Normally, leaked CO2 is efficiently transported back into the cell by the CO2 transport system, thus maintaining the extracellular CO2 concentration near zero. It is suggested that CO2 transport not only serves as a primary means of inorganic carbon acquisition for photosynthesis but also serves as a means of recovering CO2 lost from the cell. A schematic model describing the relationship between the CO2 and HCO3− transport systems is presented. Images Figure 7 PMID:16667030

  4. Evaluation of photocatalytic activities of supported catalysts on NaX zeolite or activated charcoal.

    PubMed

    de Brites-Nóbrega, Fernanda F; Polo, Aldino N B; Benedetti, Angélica M; Leão, Mônica M D; Slusarski-Santana, Veronice; Fernandes-Machado, Nádia R C

    2013-12-15

    This study aimed to evaluate the photocatalytic activity of ZnO and Nb2O5 catalysts, both supported on NaX zeolite and activated charcoal (AC). The synergistic effect between oxide and support and the influence of solution pH (3, 7 and 9) on photocatalytic degradation of reactive blue 5G (C.I. 222) were analyzed. The catalysts Nb2O5/NaX, Nb2O5/AC and ZnO/NaX, ZnO/AC with 5 and 10% (wt%) were prepared by wet impregnation. The results showed that the catalysts exhibit quite different structural and textural properties. The synergic effect between ZnO and NaX support was higher than that with the activated charcoal, showing that these catalysts were more efficient. The most photoactive catalyst was 10% ZnO/NaX which showed 100% discoloration of the dye solution at pH 3, 7 and 9 after 0.5, 5 and 2h of irradiation, respectively. The hydrolytic nature of zeolite favored the formation of surface hydroxyl radicals, which increased the activity of the photocatalyst. Thus, catalysts supported on NaX zeolite are promising for use in photocatalysis.

  5. Monoclonal antibodies that bind the renal Na/sup +//glucose symport system. 2. Stabilization of an active conformation

    SciTech Connect

    Wu, J.S.R.; Lever, J.E.

    1987-09-08

    Conformation-dependent fluorescein isothiocyanate (FITC) labeling of the pig renal Na/sup +//glucose symporter was investigated with specific monoclonal antibodies (MAb's). When renal brush border membranes were pretreated with phenyl isothiocyanate (PITC), washed, and then treated at neutral pH with FITC in the presence of transporter substrates Na/sup +/ and glucose, most of the incorporated fluorescence was associated with a single peak after resolution by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The apparent molecular mass of the FITC-labeled species ranged from 79 to 92 kDa. Labeling of this peak was specifically reduced by 70% if Na/sup +/ and glucose were omitted. Na/sup +/ could not be replaced by K/sup +/, Rb/sup +/, or Li/sup +/. FITC labeling of this peak was also stimulated after incubation of membranes with MAb's known to influence high-affinity phlorizin binding, and stimulation was synergistically increased when MAb's were added in the presence of Na/sup +/ and glucose. Substrate-induced or MAb-induced labeling correlated with inactivation of Na/sup +/-dependent phlorizin binding. MAb's recognized an antigen of 75 kDa in the native membranes whereas substrate-induced FITC labeling was accompanied by loss of antigen recognition and protection from proteolysis. These findings are consistent with a model in which MAb's stabilize a Na/sup +/-induced active conformer of the Na/sup +//glucose symport system.

  6. Measuring Cation Transport by Na,K- and H,K-ATPase in Xenopus Oocytes by Atomic Absorption Spectrophotometry: An Alternative to Radioisotope Assays

    PubMed Central

    Dürr, Katharina L.; Tavraz, Neslihan N.; Spiller, Susan; Friedrich, Thomas

    2013-01-01

    Whereas cation transport by the electrogenic membrane transporter Na+,K+-ATPase can be measured by electrophysiology, the electroneutrally operating gastric H+,K+-ATPase is more difficult to investigate. Many transport assays utilize radioisotopes to achieve a sufficient signal-to-noise ratio, however, the necessary security measures impose severe restrictions regarding human exposure or assay design. Furthermore, ion transport across cell membranes is critically influenced by the membrane potential, which is not straightforwardly controlled in cell culture or in proteoliposome preparations. Here, we make use of the outstanding sensitivity of atomic absorption spectrophotometry (AAS) towards trace amounts of chemical elements to measure Rb+ or Li+ transport by Na+,K+- or gastric H+,K+-ATPase in single cells. Using Xenopus oocytes as expression system, we determine the amount of Rb+ (Li+) transported into the cells by measuring samples of single-oocyte homogenates in an AAS device equipped with a transversely heated graphite atomizer (THGA) furnace, which is loaded from an autosampler. Since the background of unspecific Rb+ uptake into control oocytes or during application of ATPase-specific inhibitors is very small, it is possible to implement complex kinetic assay schemes involving a large number of experimental conditions simultaneously, or to compare the transport capacity and kinetics of site-specifically mutated transporters with high precision. Furthermore, since cation uptake is determined on single cells, the flux experiments can be carried out in combination with two-electrode voltage-clamping (TEVC) to achieve accurate control of the membrane potential and current. This allowed e.g. to quantitatively determine the 3Na+/2K+ transport stoichiometry of the Na+,K+-ATPase and enabled for the first time to investigate the voltage dependence of cation transport by the electroneutrally operating gastric H+,K+-ATPase. In principle, the assay is not limited to K+-transporting

  7. Reverse osmosis transport of alkali halides and nickel salts through cellulose triacetate membranes. Performance prediction from NaCl experiments

    SciTech Connect

    Nirmal, J.D.; Pandya, V.P.; Desai, N.V.; Rangarajan, R. )

    1992-10-01

    The separation of alkali metal halides, nickel chloride, and nickel sulfate was determined for cellulose triacetate reverse osmosis (CTA RO) membranes. From transport analysis, the relative free energy parameters for transport of these salts through CTA membranes were determined. From these relative free energy parameters of salts, the solute separation by CTA membranes could be predicted from RO experiment with NaCl solution. The transport analysis and an illustration of how the concept is useful are presented in this paper.

  8. Expression cloning of a rat liver Na(+)-independent organic anion transporter.

    PubMed Central

    Jacquemin, E; Hagenbuch, B; Stieger, B; Wolkoff, A W; Meier, P J

    1994-01-01

    Using expression cloning in Xenopus laevis oocytes, we have isolated a cDNA encoding a rat liver organic anion-transporting polypeptide (oatp). The cloned oatp mediated Na(+)-independent uptake of sulfobromophthalein (BSP) which was Cl(-)-dependent in the presence of bovine serum albumin (BSA) at low BSP concentrations (e.g., 2 microM). Addition of increasing amounts of BSA had no effects on the maximal velocity of initial BSP uptake, but it increased the Km value from 1.5 microM (no BSA) to 24 microM (BSA/BSP molar ratio, 3.7) and 35 microM (BSA/BSP ratio, 18.4). In addition to BSP, the cloned oatp also mediated Na(+)-independent uptake of conjugated (taurocholate) and unconjugated (cholate) bile acids. Sequence analysis of the cDNA revealed an open reading frame of 2010 nucleotides coding for a protein of 670 amino acids (calculated molecular mass, 74 kDa) with four possible N-linked glycosylation sites and 10 putative transmembrane domains. Translation experiments in vitro indicated that the transporter was indeed glycosylated and that its polypeptide backbone had an apparent molecular mass of 59 kDa. Northern blot analysis with the cloned probe revealed crossreactivity with several mRNA species from rat liver, kidney, brain, lung, skeletal muscle, and proximal colon as well as from liver tissues of mouse and rabbit, but not of skate (Raja erinacea) and human. Images Fig. 5 PMID:8278353

  9. Transport of biologically active material in laser cutting.

    PubMed

    Frenz, M; Mathezloic, F; Stoffel, M H; Zweig, A D; Romano, V; Weber, H P

    1988-01-01

    The transport of biologically active material during laser cutting with CO2 and Er lasers is demonstrated. This transport mechanism removes particles from the surface of gelatin, agar, and liver samples into the depth of the laser-formed craters. The transport phenomenon is explained by a contraction and condensation of enclosed hot water vapor. We show by cultivating transported bacteria in agar that biological particles can survive the shock of the transport. Determination of the numbers of active cells evidences a more pronounced activity of the cultivated bacteria after impact with an Er laser than with a CO2 laser.

  10. Close Association of Carbonic Anhydrase (CA2a and CA15a), Na+/H+ Exchanger (Nhe3b), and Ammonia Transporter Rhcg1 in Zebrafish Ionocytes Responsible for Na+ Uptake

    PubMed Central

    Ito, Yusuke; Kobayashi, Sayako; Nakamura, Nobuhiro; Miyagi, Hisako; Esaki, Masahiro; Hoshijima, Kazuyuki; Hirose, Shigehisa

    2013-01-01

    Freshwater (FW) fishes actively absorb salt from their environment to tolerate low salinities. We previously reported that vacuolar-type H+-ATPase/mitochondrion-rich cells (H-MRCs) on the skin epithelium of zebrafish larvae (Danio rerio) are primary sites for Na+ uptake. In this study, in an attempt to clarify the mechanism for the Na+ uptake, we performed a systematic analysis of gene expression patterns of zebrafish carbonic anhydrase (CA) isoforms and found that, of 12 CA isoforms, CA2a and CA15a are highly expressed in H-MRCs at larval stages. The ca2a and ca15a mRNA expression were salinity-dependent; they were upregulated in 0.03 mM Na+ water whereas ca15a but not ca2a was down-regulated in 70 mM Na+ water. Immunohistochemistry demonstrated cytoplasmic distribution of CA2a and apical membrane localization of CA15a. Furthermore, cell surface immunofluorescence staining revealed external surface localization of CA15a. Depletion of either CA2a or CA15a expression by Morpholino antisense oligonucleotides resulted in a significant decrease in Na+ accumulation in H-MRCs. An in situ proximity ligation assay demonstrated a very close association of CA2a, CA15a, Na+/H+ exchanger 3b (Nhe3b), and Rhcg1 ammonia transporter in H-MRC. Our findings suggest that CA2a, CA15a, and Rhcg1 play a key role in Na+uptake under FW conditions by forming a transport metabolon with Nhe3b. PMID:23565095

  11. Characterization and antibacterial activity of silver exchanged regenerated NaY zeolite from surfactant-modified NaY zeolite.

    PubMed

    Salim, Mashitah Mad; Malek, Nik Ahmad Nizam Nik

    2016-02-01

    The antibacterial activity of regenerated NaY zeolite (thermal treatment from cetyltrimethyl ammonium bromide (CTAB)-modified NaY zeolite and pretreatment with Na ions) loaded with silver ions were examined using the broth dilution minimum inhibitory concentration (MIC) method against Escherichia coli (E. coli ATCC 11229) and Staphylococcus aureus (S. aureus ATCC 6538). X-ray diffraction (XRD), attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) and chemical elemental analyses were used to characterize the regenerated NaY and AgY zeolites. The XRD patterns indicated that the calcination and addition of silver ions on regenerated NaY zeolite did not affect the structure of the regenerated NaY zeolite as the characteristic peaks of the NaY zeolite were retained, and no new peaks were observed. The regenerated AgY zeolite showed good antibacterial activity against both bacteria strains in distilled water, and the antibacterial activity of the samples increased with increasing Ag loaded on the regenerated AgY zeolite; the regenerated AgY zeolite was more effective against E. coli than S. aureus. However, the antibacterial activity of the regenerated AgY was not effective in saline solution for both bacteria. The study showed that CTAB-modified NaY zeolite materials could be regenerated to NaY zeolite using thermal treatment (550°C, 5h) and this material has excellent performance as an antibacterial agent after silver ions loading. PMID:26652350

  12. Characterization and antibacterial activity of silver exchanged regenerated NaY zeolite from surfactant-modified NaY zeolite.

    PubMed

    Salim, Mashitah Mad; Malek, Nik Ahmad Nizam Nik

    2016-02-01

    The antibacterial activity of regenerated NaY zeolite (thermal treatment from cetyltrimethyl ammonium bromide (CTAB)-modified NaY zeolite and pretreatment with Na ions) loaded with silver ions were examined using the broth dilution minimum inhibitory concentration (MIC) method against Escherichia coli (E. coli ATCC 11229) and Staphylococcus aureus (S. aureus ATCC 6538). X-ray diffraction (XRD), attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) and chemical elemental analyses were used to characterize the regenerated NaY and AgY zeolites. The XRD patterns indicated that the calcination and addition of silver ions on regenerated NaY zeolite did not affect the structure of the regenerated NaY zeolite as the characteristic peaks of the NaY zeolite were retained, and no new peaks were observed. The regenerated AgY zeolite showed good antibacterial activity against both bacteria strains in distilled water, and the antibacterial activity of the samples increased with increasing Ag loaded on the regenerated AgY zeolite; the regenerated AgY zeolite was more effective against E. coli than S. aureus. However, the antibacterial activity of the regenerated AgY was not effective in saline solution for both bacteria. The study showed that CTAB-modified NaY zeolite materials could be regenerated to NaY zeolite using thermal treatment (550°C, 5h) and this material has excellent performance as an antibacterial agent after silver ions loading.

  13. A Simple Laboratory Exercise Illustrating Active Transport in Yeast Cells.

    ERIC Educational Resources Information Center

    Stambuk, Boris U.

    2000-01-01

    Describes a simple laboratory activity illustrating the chemiosmotic principles of active transport in yeast cells. Demonstrates the energy coupling mechanism of active a-glucoside uptake by Saccaromyces cerevisiae cells with a colorimetric transport assay using very simple equipment. (Contains 22 references.) (Author/YDS)

  14. Highly conserved asparagine 82 controls the interaction of Na+ with the sodium-coupled neutral amino acid transporter SNAT2.

    PubMed

    Zhang, Zhou; Gameiro, Armanda; Grewer, Christof

    2008-05-01

    The neutral amino acid transporter 2 (SNAT2), which belongs to the SLC38 family of solute transporters, couples the transport of amino acid to the cotransport of one Na(+) ion into the cell. Several polar amino acids are highly conserved within the SLC38 family. Here, we mutated three of these conserved amino acids, Asn(82) in the predicted transmembrane domain 1 (TMD1), Tyr(337) in TMD7, and Arg(374) in TMD8; and we studied the functional consequences of these modifications. The mutation of N82A virtually eliminated the alanine-induced transport current, as well as amino acid uptake by SNAT2. In contrast, the mutations Y337A and R374Q did not abolish amino acid transport. The K(m) of SNAT2 for its interaction with Na(+), K(Na(+)), was dramatically reduced by the N82A mutation, whereas the more conservative mutation N82S resulted in a K(Na(+)) that was in between SNAT2(N82A) and SNAT2(WT). These results were interpreted as a reduction of Na(+) affinity caused by the Asn(82) mutations, suggesting that these mutations interfere with the interaction of SNAT2 with the sodium ion. As a consequence of this dramatic reduction in Na(+) affinity, the apparent K(m) of SNAT2(N82A) for alanine was increased 27-fold compared with that of SNAT2(WT). Our results demonstrate a direct or indirect involvement of Asn(82) in Na(+) coordination by SNAT2. Therefore, we predict that TMD1 is crucial for the function of SLC38 transporters and that of related families.

  15. Preparation of activated carbon from wet sludge by electrochemical-NaClO activation.

    PubMed

    Miao, Chen; Ye, Caihong; Zhu, Tianxing; Lou, Ziyang; Yuan, Haiping; Zhu, Nanwen

    2014-01-01

    Activated carbon (AC) from sludge is one potential solution for sewage sludge disposal, while the drying sludge is cost and time consuming for preparation. AC preparation from the wet sludge with electrochemical-NaClO activation was studied in this work. Three pretreatment processes, i.e. chemical activation, electrolysis and electrochemical-reagent reaction, were introduced to improve the sludge-derived AC properties, and the optimum dosage of reagent was tested from the 0.1:1 to 1:1 (mass rate, reagent:dried sludge). It was shown that the electrochemical-NaClO preparation is the best method under the test conditions, in which AC has the maximum Brunauer, Emmett and Teller area of 436 m²/g at a mass ratio of 0.7. Extracellular polymeric substances in sludge can be disintegrated by electrochemical-NaClO pretreatment, with a disintegration degree of more than 45%. The percentage of carbon decreased from 34.16 to 8.81 after treated by electrochemical-NaClO activation. Fourier transform infrared spectra showed that a strong C-Cl stretching was formed in electrochemical-NaClO prepared AC. The maximum adsorption capacity of AC reaches 109 mg/g on MB adsorption experiment at pH 10 and can be repeated for three times with high removal efficiency after regeneration.

  16. Air pollution exposure: An activity pattern approach for active transportation

    NASA Astrophysics Data System (ADS)

    Adams, Matthew D.; Yiannakoulias, Nikolaos; Kanaroglou, Pavlos S.

    2016-09-01

    In this paper, we demonstrate the calculation of personal air pollution exposure during trips made by active transportation using activity patterns without personal monitors. We calculate exposure as the inhaled dose of particulate matter 2.5 μg or smaller. Two modes of active transportation are compared, and they include cycling and walking. Ambient conditions are calculated by combining mobile and stationary monitoring data in an artificial neural network space-time model. The model uses a land use regression framework and has a prediction accuracy of R2 = 0.78. Exposure is calculated at 10 m or shorter intervals during the trips using inhalation rates associated with both modes. The trips are children's routes between home and school. The average dose during morning cycling trips was 2.17 μg, during morning walking trips was 3.19 μg, during afternoon cycling trips was 2.19 μg and during afternoon walking trips was 3.23 μg. The cycling trip dose was significantly lower than the walking trip dose. The air pollution exposure during walking or cycling trips could not be strongly predicted by either the school or household ambient conditions, either individually or in combination. Multiple linear regression models regressing both the household and school ambient conditions against the dose were only able to account for, at most, six percent of the variance in the exposure. This paper demonstrates that incorporating activity patterns when calculating exposure can improve the estimate of exposure compared to its calculation from ambient conditions.

  17. Freshwater transport forms of Na, Mg, and Ca in streams of adjacent headwater catchments composed of differing vegetation

    NASA Astrophysics Data System (ADS)

    Terajima, T.; Moriizumi, M.

    2012-04-01

    To understand the freshwater transport forms of major metals, concentrations of Na, Mg, Ca, Si, and fulvic acid-like materials (FAM) were measured in streams of headwater catchments with differing vegetation (coniferous and deciduous forests). The proportion of non-ionic forms (NIF) relative to total elements in the coniferous and deciduous catchments ranged from 0% to 40% and from 0% to 70%, respectively, in baseflows, and from 5% to 60% and from 20% to 60%, respectively, in stormflows. In the baseflows, NIF and total Si (T-Si) were highly correlated (r > 0.9) in both catchments. In contrast, in the stormflows, T-Si and FAM showed a good correlation (r > 0.8) in both catchments, implying that stormflow may have enhanced organic-inorganic binding. However, in the coniferous catchment, good correlations (r > 0.8) between NIF and T-Si or FAM were associated with only the rising limb of the hydrograph, whereas in the deciduous catchment, good correlations (r > 0.8) were associated with both the rising and falling limbs. These results indicate that: (1) under low-flow conditions, major metals may form binding with clay minerals and thus be transported as NIF, (2) storm events may enhance the binding of clay minerals with humic substances, (3) in the coniferous catchment, the complexation of NIF with the organic-inorganic binding and their transport in stormflows are associated with the rising limb of the storm hydrograph, whereas NIF transport during the falling limb may reflect the effect of other materials, and (4) in the deciduous catchment, NIF transport may occur mainly in association with organic-inorganic binding throughout a storm event. These findings show that active binding of Na, Mg, and Ca in freshwater environments with organic and inorganic substances, under the effect of differing vegetation on that binding, should be carefully examined in studies of chemical hydrology in headwater catchments. Key words: fulvic acid, major metal, complexation, humic

  18. Proteinases inhibit H(+)-ATPase and Na+/H+ exchange but not water transport in apical and endosomal membranes from rat proximal tubule.

    PubMed

    Sabolić, I; Shi, L B; Brown, D; Ausiello, D A; Verkman, A S

    1992-01-10

    A marked increase in water permeability can be induced in Xenopus oocytes by injection of mRNA from tissues that express water channels, suggesting that the water channel is a protein. In view of this and previous reports which showed that proteinases may interfere with mercurial inhibition of water transport in red blood cells (RBC), we examined the influence of trypsin, chymotrypsin, papain, pronase, subtilisin and thermolysin on water permeability as well as on ATPase activity, H(+)-pump, passive H+ conductance, and Na+/H+ exchange in apical brush-border vesicles (BBMV) and endosomal (EV) vesicles from rat renal cortex. H+ transport was measured by Acridine orange fluorescence quenching and water transport by stopped-flow light scattering. As measured by potential-driven H+ accumulation in BBMV and EV, proteinase treatment had little effect on vesicle integrity. In BBMV, ecto-ATPase activity was inhibited by 15-30%, Na+/H+ exchange by 20-55%, and H+ conductance was unchanged. Osmotic water permeability (Pf) was 570 microns/s and was inhibited 85-90% by 0.6 mM HgCl2; proteinase treatment did not affect Pf or the HgCl2 inhibition. In EV, NEM-sensitive H+ accumulation and ATPase activity were inhibited by greater than 95%. Pf (140 microns/s) and HgCl2 inhibition (75-85%) were not influenced by proteinase treatment. SDS-PAGE showed selective digestion of multiple polypeptides by proteinases. These results confirm the presence of water channels in BBMV and EV and demonstrate selective inhibition of ATPase function and Na+/H+ exchange by proteinase digestion. The lack of effect of proteinases on water transport by mercurials. We conclude that the water channel may be a small integral membrane protein which, unlike the H(+)-ATPase and Na+/H+ exchanger, has no functionally important membrane domains that are sensitive to proteolysis. PMID:1309658

  19. Effects of insulin on Na and K transporters in the rat CCD.

    PubMed

    Frindt, Gustavo; Palmer, Lawrence G

    2012-05-15

    We tested the effects of insulin (2 nM, 30-60 min) on principal cells of isolated split-open rat cortical collecting ducts (CCD) using whole-cell current measurements. Insulin addition to the superfusate of the tubules enhanced Na pump (ouabain-sensitive) current from 18 ± 3 to 31 ± 3 pA/cell in control and from 74 ± 9 to 126 ± 11 pA/cell in high K-fed animals. It also more than doubled ROMK (tertiapin-Q-sensitive) K(+) currents in control CCD from 320 ± 40 to 700 ± 80 pA/cell, although it did not affect this current in tubules from K-loaded rats. Insulin did not induce the appearance of amiloride-sensitive Na(+) current in control animals, while in high K-fed animals the currents were similar in the presence (140 ± 30) and the absence (180 ± 70 pA/cell) of insulin. Intraperitoneal injection of insulin plus hypertonic dextrose decreased Na excretion, as previously reported. However, injection of dextrose alone, or the nonmetabolized sugar mannose, had similar effects, suggesting that they were largely the result of vascular volume depletion rather than specific actions of the hormone. In summary, we find no evidence for acute upregulation of the epithelial Na channel (ENaC) by physiological concentrations of insulin in the mammalian CCD. However, the hormone does activate both the Na/K pump and apical K(+) channels and could, under some conditions, enhance renal K(+) secretion. PMID:22357918

  20. Leucine-rich repeat kinase 2-sensitive Na+/Ca2+ exchanger activity in dendritic cells.

    PubMed

    Yan, Jing; Almilaji, Ahmad; Schmid, Evi; Elvira, Bernat; Shimshek, Derya R; van der Putten, Herman; Wagner, Carsten A; Shumilina, Ekaterina; Lang, Florian

    2015-05-01

    Gene variants of the leucine-rich repeat kinase 2 (LRRK2) are associated with susceptibility to Parkinson's disease (PD). Besides brain and periphery, LRRK2 is expressed in various immune cells including dendritic cells (DCs), antigen-presenting cells linking innate and adaptive immunity. However, the function of LRRK2 in the immune system is still incompletely understood. Here, Ca(2+)-signaling was analyzed in DCs isolated from gene-targeted mice lacking lrrk2 (Lrrk2(-/-)) and their wild-type littermates (Lrrk2(+/+)). According to Western blotting, Lrrk2 was expressed in Lrrk2(+/+) DCs but not in Lrrk2(-/-)DCs. Cytosolic Ca(2+) levels ([Ca(2+)]i) were determined utilizing Fura-2 fluorescence and whole cell currents to decipher electrogenic transport. The increase of [Ca(2+)]i following inhibition of sarcoendoplasmatic Ca(2+)-ATPase with thapsigargin (1 µM) in the absence of extracellular Ca(2+) (Ca(2+)-release) and the increase of [Ca(2+)]i following subsequent readdition of extracellular Ca(2+) (SOCE) were both significantly larger in Lrrk2(-/-) than in Lrrk2(+/+) DCs. The augmented increase of [Ca(2+)]i could have been due to impaired Ca(2+) extrusion by K(+)-independent (NCX) and/or K(+)-dependent (NCKX) Na(+)/Ca(2+)-exchanger activity, which was thus determined from the increase of [Ca(2+)]i, (Δ[Ca(2+)]i), and current following abrupt replacement of Na(+) containing (130 mM) and Ca(2+) free (0 mM) extracellular perfusate by Na(+) free (0 mM) and Ca(2+) containing (2 mM) extracellular perfusate. As a result, both slope and peak of Δ[Ca(2+)]i as well as Na(+)/Ca(2+) exchanger-induced current were significantly lower in Lrrk2(-/-) than in Lrrk2(+/+) DCs. A 6 or 24 hour treatment with the LRRK2 inhibitor GSK2578215A (1 µM) significantly decreased NCX1 and NCKX1 transcript levels, significantly blunted Na(+)/Ca(2+)-exchanger activity, and significantly augmented the increase of [Ca(2+)]i following Ca(2+)-release and SOCE. In conclusion, the present observations

  1. Na+ coordination at the Na2 site of the Na+/I- symporter.

    PubMed

    Ferrandino, Giuseppe; Nicola, Juan Pablo; Sánchez, Yuly E; Echeverria, Ignacia; Liu, Yunlong; Amzel, L Mario; Carrasco, Nancy

    2016-09-13

    The sodium/iodide symporter (NIS) mediates active I(-) transport in the thyroid-the first step in thyroid hormone biosynthesis-with a 2 Na(+): 1 I(-) stoichiometry. The two Na(+) binding sites (Na1 and Na2) and the I(-) binding site interact allosterically: when Na(+) binds to a Na(+) site, the affinity of NIS for the other Na(+) and for I(-) increases significantly. In all Na(+)-dependent transporters with the same fold as NIS, the side chains of two residues, S353 and T354 (NIS numbering), were identified as the Na(+) ligands at Na2. To understand the cooperativity between the substrates, we investigated the coordination at the Na2 site. We determined that four other residues-S66, D191, Q194, and Q263-are also involved in Na(+) coordination at this site. Experiments in whole cells demonstrated that these four residues participate in transport by NIS: mutations at these positions result in proteins that, although expressed at the plasma membrane, transport little or no I(-) These residues are conserved throughout the entire SLC5 family, to which NIS belongs, suggesting that they serve a similar function in the other transporters. Our findings also suggest that the increase in affinity that each site displays when an ion binds to another site may result from changes in the dynamics of the transporter. These mechanistic insights deepen our understanding not only of NIS but also of other transporters, including many that, like NIS, are of great medical relevance.

  2. cap alpha. -Methylglucoside satisfies only Na/sup +/-dependent transport system of intestinal epithelium

    SciTech Connect

    Kimmich, G.A.; Randles, J.

    1981-01-01

    The unidirectional influx of ..cap alpha..-methylglucoside (..cap alpha..-MG) by isolated chicken intestinal epithelial cells is 98% inhibited by phlorizin. The remaining 2% of the total influx occurs in the absence of Na/sup +/, is not sensitive to phloretin, and is equal to the diffusional entry rate for 2-deoxyglucose. The glucoside is much more strongly accumulated (75-fold) than 3-O-methylglucose (3-OMG) (10-fold). Inhibitors of the serosal sugar carrier (phloretin, cytochalasin B, theophylline, and flavanoids) do not enhance ..cap alpha..-MG accumulation. It is concluded that the glycoside is not a substrate for the intestinal serosal transport system. Steady-state gradients of the sugar can be represented accurately by a concentrative, phlorizin-sensitive system that is opposed by a diffusional efflux process.

  3. Airway surface liquid volume expansion induces rapid changes in amiloride-sensitive Na+ transport across upper airway epithelium-Implications concerning the resolution of pulmonary edema.

    PubMed

    Azizi, Fouad; Arredouani, Abdelilah; Mohammad, Ramzi M

    2015-09-01

    During airway inflammation, airway surface liquid volume (ASLV) expansion may result from the movement of plasma proteins and excess liquid into the airway lumen due to extravasation and elevation of subepithelial hydrostatic pressure. We previously demonstrated that elevation of submucosal hydrostatic pressure increases airway epithelium permeability resulting in ASLV expansion by 500 μL cm(-2) h(-1). Liquid reabsorption by healthy airway epithelium is regulated by active Na(+) transport at a rate of 5 μL cm(-2) h(-1). Thus, during inflammation the airway epithelium may be submerged by a large volume of luminal liquid. Here, we have investigated the mechanism by which ASLV expansion alters active epithelial Na(+) transport, and we have characterized the time course of the change. We used primary cultures of tracheal airway epithelium maintained under air interface (basal ASLV, depth is 7 ± 0.5 μm). To mimic airway flooding, ASLV was expanded to a depth of 5 mm. On switching from basal to expanded ASLV conditions, short-circuit current (Isc, a measure of total transepithelial active ion transport) declined by 90% with a half-time (t1/2) of 1 h. 24 h after the switch, there was no significant change in ATP concentration nor in the number of functional sodium pumps as revealed by [(3)H]-ouabain binding. However, amiloride-sensitive uptake of (22)Na(+) was reduced by 70% upon ASLV expansion. This process is reversible since after returning cells back to air interface, Isc recovered with a t1/2 of 5-10 h. These results may have important clinical implications concerning the development of Na(+) channels activators and resolution of pulmonary edema.

  4. Dynamic model of active transport: application to sodium/potassium pump

    NASA Astrophysics Data System (ADS)

    Keating, Brian; Finkel, Robert

    2006-11-01

    Active transport is a process where some energetic agent, generally an enzyme powered by ATP, conveys ions across a membrane. Here we present a novel physical approach to modeling the dynamics of active transport. Specifically, we employ a general method whereby the non-equilibrium energetics of active transport derive simply from the chemical kinetic rate equations. The case treated here is an exchange of sodium and potassium ions across a cell membrane at the expenditure of one ATP---a process common to most life forms. The generic rate equations are readily formulated and only two well-established quantities are input, the ATP energy value and the membrane potential. The model uses this sparse information to generate several agreements with experimental values including the relative concentrations of Na and K on either side of the membrane and the celebrated 3:2 transfer ratio of sodium to potassium.

  5. Ab initio investigations of the charge transport properties of endohedral M@C20 (M = Na and K) metallofullerenes

    NASA Astrophysics Data System (ADS)

    An, Yi-Peng; Yang, Chuan-Lu; Wang, Mei-Shan; Ma, Xiao-Guang; Wang, De-Hua

    2010-11-01

    Using density functional theory and quantum transport calculations based on nonequilibum Green's function formalism, we investigate the charge transport properties of endohedral M@C20(M = Na and K) metallofullerenes. Our results show that the conductance of C20 fullerene can be obviously improved by insertion of alkali atom at its centre. Both linear and nonlinear sections are found on the I—V curves of the Au-M@C20-Au two-probe systems. The novel negative differential resistance behaviour is also observed in Na@C20 molecule but not in K@C20.

  6. Esophageal desalination of seawater in flounder: role of active sodium transport.

    PubMed

    Parmelee, J T; Renfro, J L

    1983-12-01

    The esophagus of the flounder, Pseudopleuronectes americanus, was studied to determine how salinity of ingested seawater (SW) is decreased before fluid absorption in the intestine. Drinking rate was 2.5 ml X h-1 X kg-1. Stomach fluid osmolality was 45% that of seawater, and intestinal fluid was isosmotic to plasma. Esophagus and stomach were nearly impermeable to 28Mg; thus Mg concentrations were accurate indicators of fluid addition and NaCl removal between pharynx and stomach. Measurements of water and ion fluxes across isolated esophageal epithelium mounted in Ussing chambers and bathed by Ringer solution showed that the tritiated water flux was lower in esophagus than in intestine and that 22Na flux ratio was 1.4 (Jm leads to s/Js leads to m) regardless of acclimation medium (100 or 10% SW). Potential difference was zero, and electrical resistance averaged 90 omega X cm2. Mucosal-to-serosal Na transport was inhibited by 0.1 mM amiloride, 0.1 mM ouabain, and Cl-free medium, whereas 1.0 mM furosemide had no effect. Net esophageal Na absorption (mucosal-to-serosal) averaged 10.0 mumol X h-1 X cm-2 with mucosa exposed to SW and was inhibited 46% by 0.1 mM ouabain. Taken together the above observations suggest a role for both passive and active esophageal Na transport in SW desalination.

  7. Transporting Radioactive Waste: An Engineering Activity. Grades 5-12.

    ERIC Educational Resources Information Center

    HAZWRAP, The Hazardous Waste Remedial Actions Program.

    This brochure contains an engineering activity for upper elementary, middle school, and high school students that examines the transportation of radioactive waste. The activity is designed to inform students about the existence of radioactive waste and its transportation to disposal sites. Students experiment with methods to contain the waste and…

  8. Active transmembrane drug transport in microgravity: a validation study using an ABC transporter model

    PubMed Central

    Vaquer, Sergi; Cuyàs, Elisabet; Rabadán, Arnau; González, Albert; Fenollosa, Felip; de la Torre, Rafael

    2014-01-01

    Microgravity has been shown to influence the expression of ABC (ATP-Binding Cassette) transporters in bacteria, fungi and mammals, but also to modify the activity of certain cellular components with structural and functional similarities to ABC transporters. Changes in activity of ABC transporters could lead to important metabolic disorders and undesired pharmacological effects during spaceflights. However, no current means exist to study the functionality of these transporters in microgravity. To this end, a Vesicular Transport Assay ® (Solvo Biotechnology, Hungary) was adapted to evaluate multi-drug resistance-associated protein 2 (MRP2) trans-membrane estradiol-17-β-glucuronide (E17βG) transport activity, when activated by adenosine-tri-phosphate (ATP) during parabolic flights. Simple diffusion, ATP-independent transport and benzbromarone inhibition were also evaluated. A high accuracy engineering system was designed to perform, monitor and synchronize all procedures. Samples were analysed using a validated high sensitivity drug detection protocol. Experiments were performed in microgravity during parabolic flights, and compared to 1g on ground results using identical equipment and procedures in all cases. Our results revealed that sufficient equipment accuracy and analytical sensitivity were reached to detect transport activity in both gravitational conditions. Additionally, transport activity levels of on ground samples were within commercial transport standards, proving the validity of the methods and equipment used. MRP2 net transport activity was significantly reduced in microgravity, so was signal detected in simple diffusion samples. Ultra-structural changes induced by gravitational stress upon vesicle membranes or transporters could explain the current results, although alternative explanations are possible. Further research is needed to provide a conclusive answer in this regard. Nevertheless, the present validated technology opens new and

  9. Neuronal Activity and Glutamate Uptake Decrease Mitochondrial Mobility in Astrocytes and Position Mitochondria Near Glutamate Transporters

    PubMed Central

    Jackson, Joshua G.; O'Donnell, John C.; Takano, Hajime; Coulter, Douglas A.

    2014-01-01

    Within neurons, mitochondria are nonuniformly distributed and are retained at sites of high activity and metabolic demand. Glutamate transport and the concomitant activation of the Na+/K+-ATPase represent a substantial energetic demand on astrocytes. We hypothesized that mitochondrial mobility within astrocytic processes might be regulated by neuronal activity and glutamate transport. We imaged organotypic hippocampal slice cultures of rat, in which astrocytes maintain their highly branched morphologies and express glutamate transporters. Using time-lapse confocal microscopy, the mobility of mitochondria within individual astrocytic processes and neuronal dendrites was tracked. Within neurons, a greater percentage of mitochondria were mobile than in astrocytes. Furthermore, they moved faster and farther than in astrocytes. Inhibiting neuronal activity with tetrodotoxin (TTX) increased the percentage of mobile mitochondria in astrocytes. Mitochondrial movement in astrocytes was inhibited by vinblastine and cytochalasin D, demonstrating that this mobility depends on both the microtubule and actin cytoskeletons. Inhibition of glutamate transport tripled the percentage of mobile mitochondria in astrocytes. Conversely, application of the transporter substrate d-aspartate reversed the TTX-induced increase in the percentage of mobile mitochondria. Inhibition of reversed Na+/Ca2+ exchange also increased the percentage of mitochondria that were mobile. Last, we demonstrated that neuronal activity increases the probability that mitochondria appose GLT-1 particles within astrocyte processes, without changing the proximity of GLT-1 particles to VGLUT1. These results imply that neuronal activity and the resulting clearance of glutamate by astrocytes regulate the movement of astrocytic mitochondria and suggest a mechanism by which glutamate transporters might retain mitochondria at sites of glutamate uptake. PMID:24478345

  10. Activation of Na+,K+,Cl- cotransport in squid giant axon by extracellular ions: evidence for ordered binding.

    PubMed

    Altamirano, A A; Breitwieser, G E; Russell, J M

    1999-01-12

    Activation of the influx mode of the Na+,K+,Cl- cotransporter (NKCC) by extracellular Na+, K+ and Cl- was studied using the internally dialyzed squid giant axon. Cooperative interactions among the three transported ions were assessed using ion activation of NKCC-mediated 36Cl influx under two sets of experimental conditions. The first, or control condition, used high, non-limiting concentrations of two of the cotransported ions (the co-ions) while activating cotransport with the third ion. Under this non-limiting co-ion condition the calculated Vmax of the cotransporter was between 57 and 60 pmol/cm2/s. The apparent activation (KApp, or half-saturation) constants were: K+, 9 mM; Na+, 52 mM; and Cl-, 146 mM. The second condition used limiting co-ion concentration conditions. In this case, activation by each ion was determined when one of the other two co-ions was present at or near its apparent half-saturation concentration as determined above. Under these limiting conditions, the KApp values for all three co-ions were significantly increased regardless of which co-ion was present at a limiting concentration. The effects on the apparent Vmax were more complicated. When K+ was the limiting co-ion, there was little effect on the Vmax for Na+ or Cl- activation. In contrast, limiting concentrations of Na+ or Cl- both resulted in a large reduction of the apparent Vmax when activating with the other two co-ions. These results are consistent with an ordered binding mechanism for the NKCC in which K+ binds before Na+ or Cl-. Physiological implications for these results are discussed.

  11. Interleukin 18 function requires both interleukin 18 receptor and Na-Cl co-transporter

    PubMed Central

    Wang, Jing; Sun, Chongxiu; Gerdes, Norbert; Liu, Conglin; Liao, Mengyang; Liu, Jian; Shi, Michael A.; He, Aina; Zhou, Yi; Sukhova, Galina K.; Chen, Huimei; Cheng, Xianwu; Kuzuya, Masafumi; Murohara, Toyoaki; Zhang, Jie; Cheng, Xiang; Jiang, Mengmeng; Shull, Gary E.; Rogers, Shaunessy; Yang, Chao-Ling; Ke, Qiang; Jelen, Sabina; Bindels, René; Ellison, David H.; Jarolim, Petr; Libby, Peter; Shi, Guo-Ping

    2015-01-01

    Interleukin-18 (IL18) participates in atherogenesis through several putative mechanisms1,2. Interruption of IL18 action reduces atherosclerosis in mice3,4. This study shows that the absence of IL18 receptor (IL18r) does not affect atherosclerosis in apolipoprotein E-deficient (Apoe−/−) mice, nor does it affect IL18 cell surface binding or signaling. IL18 antibody-mediated immunoprecipitation identified an interaction between IL18 and Na-Cl co-transporter (NCC), a 12-transmembrane-domain ion transporter protein preferentially expressed in the kidney5. Yet, we find NCC expression and colocalization with IL18r in atherosclerotic lesions and both molecules form a complex. IL18 also binds to the cell surface and induces cell signaling and down-stream cytokine expression in NCC-transfected COS-7 cells that do not express IL18r. In Apoe−/− mice, combined deficiency of IL18r and NCC, but not single deficiency, protects mice from atherosclerosis. Peritoneal macrophages from Apoe−/− mice or those lacking IL18r or NCC respond to IL18 binding or IL18 induction of cell signaling and cytokine and chemokine production, but those with combined deficiency of IL18r and NCC do not. This study identifies NCC as an IL18-binding protein that coordinates with IL18r in cell signaling, inflammatory molecule expression, and experimental atherogenesis. PMID:26099046

  12. Activation of tubulo-glomerular feedback by chloride transport.

    PubMed

    Schnermann, J; Ploth, D W; Hermle, M

    1976-04-01

    To define the luminal agent(s) responsible for the reduction of nephron filtration rate following increases of loop of Henle flow rate early proximal flow rate (EPFR) during loop perfusion with 17 different salt solutions were compared to the non-perfused tubules. During orthograde microperfusions a reduction of EPFR as indication of a feedback response was noted with a number of monovalent Cl- and Br- salts (LiCl, KCl, NaCl, RbCl, CsCl, NH4Cl, choline Cl, NaBr, KBr), with Na+ salts except Na acetate (NaHCO3, NaNO3, NaF, NaI, NaSCN), and with CaCl2 and MgCl2. These latter 2 solutions where used in a concentration of 70 mM while all other solutions had a concentration of 140 mM. During retrograde perfusion from the distal to the proximal end of the loop of Henle EPFR fell significantly with Cl- and Br- salts with percentage changes of EPFR ranging from -8.0 to -44.3%. In contrast, Cl- free salts and Cl- salts of divalent cations were associated with percentage changes of EPFR ranging from +7.1 to -6.2%, significance being reached only during perfusion with NaSCN. When furosemide (5 x 10(-4) M) was added to NaBr or KBr a feedback response was not observed. During orthograde perfusion with NaNO3 distal Cl- concentrations were 44.2 +/- 5.08, mM (mean +/- S.E.) at a perfusion rate of 10 nl/min and 59.1 +/- 3.93 mM at a rate of 40 nl/min. CaCl2 perfusion induced a marked elevation of distal Cl- concentrations to levels higher than 140 mM. Loop chloride handling was normal during RbCl perfusion. The magnitude of the feedback response during retrograde perfusion was not changed by lowering NaCl concentration from 140 to 60 mM, but fell when NaCl concentration was further reduced. In contrast to orthograde perfusions it was insensitive to changes in flow rate. Our results are compatible with the thesis that feedback responses depend critically upon the rate of Cl- transport probably across the macula densa cells. Br- ions can replace Cl- because they appear to share a

  13. Coupling of active sodium transport to oxidative metabolism in the rabbit distal colon.

    PubMed Central

    Durand, J; Durand-Arczynska, W; Wankmiller, D

    1988-01-01

    1. Active transepithelial Na+ transport (Ji) and O2 consumption (Jr) were measured simultaneously in rabbit distal colon, under standard (control) incubation conditions and after various manoeuvres, known to inhibit Na+ transport. 2. The determination of Jr was complicated by the presence of fluctuations of the PO2 in the incubation solution and by spontaneous variations of the tissue respiration, which usually declined slowly with time. 3. The control values of Ji and Jr after 2 h incubation were 55 +/- 4 nequiv min-1 cm-2 and 16 +/- 1 nmol O2 min-1 cm-2, respectively (n = 44). The electrical resistance was 386 +/- 23 omega cm2; it was stable over 6 h. 4. Ji was reduced to a very low level with either amiloride, ouabain or Na+ substitution with choline. In all instances, Jr decreased concomitantly by 15-30%. 5. A plot of the change in Jr versus the change in Ji gave a straight line for all situations, i.e. for the spontaneous decline of Na+ transport and respiration and for the effects of the inhibitors. 6. The linearity between Jr and Ji allows for the determination of a stoichiometric ratio. It is of similar magnitude, when calculated either with the data of spontaneous variations or with those obtained by the action of any inhibitor tested. It is 15-20 Na+ ions per O2 molecule, a value close to that reported previously for amphibian epithelia and also close to the maximum theoretical value of 18 Na+ ions per O2 molecule. PMID:3411504

  14. Aerobic and anaerobic metabolism in smooth muscle cells of taenia coli in relation to active ion transport.

    PubMed

    Casteels, R; Wuytack, F

    1975-09-01

    1. The O2 consumption and lactic acid production of the guinea-pig's taenia coli have been studied in relation to the active Na-K transport, in order to estimate the ratio: active Na extrusion/active K uptake/ATP hydrolysis. 2. By applying different procedures of partial metabolic ingibition, it was found that a reactivation of the active Na-K transport in K-depleted tissues could occur in an anaerobic medium, provided glucose was present and in an aerobic medium free of added metabolizable substrate. The active Na-K transport was rapidly blocked in an anaerobic-substrate free medium. 3. Readmission of K to K-depleted tissues under aerobic conditions stimulates both O2 consumption and lactic acid production. While the O2 consumption creeps up slowly and requires 50 min to reach control values, the aerobic lactic acid production increases to a maximum within 10 min and decreases again during the next 50 min to its steady-state value. 4. A reactivation of the Na-pump in K-depleted cells in a N2-glucose medium causes an immediate increase of the lactic acid production, which decreases to its control value after 60 min. The maximal increase in anaerobic lactic acid production during reactivation of the Na-K pump is a function of [K]O. The system can be cescribed with first order kinetics having a Vmax = 0-72 mumole.g-1 f. wt. min-1 and a Km = 1-1 mM. 5. By varying the glucose concentration of [K]O during reactivation of the Na-K pump, different Na-K pumping rates can be obtained. The ratios net Na extrusion/ATP or net K accumulation/ATP amount to -1-32 +/- 0-19 (36) and 1-02 +/- 0-11 (36), in the experiments with different glucose concentrations. Taking into account the interference by net passive fluxes, one can estimate a ratio:active Na transport/active K transport/ATP, of 1-7/0-8/1. This ratio is not very different from the values observed in other tissues.

  15. Metabolic Programming during Lactation Stimulates Renal Na+ Transport in the Adult Offspring Due to an Early Impact on Local Angiotensin II Pathways

    PubMed Central

    Luzardo, Ricardo; Silva, Paulo A.; Einicker-Lamas, Marcelo; Ortiz-Costa, Susana; da Graça Tavares do Carmo, Maria; Vieira-Filho, Leucio D.; Paixão, Ana D. O.; Lara, Lucienne S.; Vieyra, Adalberto

    2011-01-01

    Background Several studies have correlated perinatal malnutrition with diseases in adulthood, giving support to the programming hypothesis. In this study, the effects of maternal undernutrition during lactation on renal Na+-transporters and on the local angiotensin II (Ang II) signaling cascade in rats were investigated. Methodology/Principal Findings Female rats received a hypoproteic diet (8% protein) throughout lactation. Control and programmed offspring consumed a diet containing 20% protein after weaning. Programming caused a decrease in the number of nephrons (35%), in the area of the Bowman's capsule (30%) and the capillary tuft (30%), and increased collagen deposition in the cortex and medulla (by 175% and 700%, respectively). In programmed rats the expression of (Na++K+)ATPase in proximal tubules increased by 40%, but its activity was doubled owing to a threefold increase in affinity for K+. Programming doubled the ouabain-insensitive Na+-ATPase activity with loss of its physiological response to Ang II, increased the expression of AT1 and decreased the expression of AT2 receptors), and caused a pronounced inhibition (90%) of protein kinase C activity with decrease in the expression of the α (24%) and ε (13%) isoforms. Activity and expression of cyclic AMP-dependent protein kinase decreased in the same proportion as the AT2 receptors (30%). In vivo studies at 60 days revealed an increased glomerular filtration rate (GFR) (70%), increased Na+ excretion (80%) and intense proteinuria (increase of 400% in protein excretion). Programmed rats, which had normal arterial pressure at 60 days, became hypertensive by 150 days. Conclusions/Significance Maternal protein restriction during lactation results in alterations in GFR, renal Na+ handling and in components of the Ang II-linked regulatory pathway of renal Na+ reabsorption. At the molecular level, they provide a framework for understanding how metabolic programming of renal mechanisms contributes to the onset

  16. Chlordecone impairs Na(+)-stimulated L-( sup 3 H)glutamate transport and mobility of 16-doxyl stearate in rat liver plasma membrane vesicles

    SciTech Connect

    Rochelle, L.G.; Miller, T.L.; Curtis, L.R. )

    1990-09-01

    Chlordecone (CD) treatment of rat liver plasma membranes (LPM) provided in vitro evidence for mechanisms of in vivo liver dysfunction caused by CD. LPM preparations enriched 14- to 19-fold in the bile canalicular markers gamma-glutamyl transpeptidase, alkaline phosphatase, and leucine aminopeptidase were isolated from male Sprague-Dawley rats. CD inhibited the bile canalicular-specific active transport of Na(+)-stimulated L-({sup 3}H)glutamate in LPM vesicles. CD (0.08 and 0.5 mumol/mg protein) reduced both the initial velocity and the maximum level of Na(+)-stimulated L-(3H)glutamate uptake without significantly reducing Na(+)-independent uptake. In vitro treatment of LPM with CD (0.2-1.0 mumols/mg protein) also reduced the mobility of a 16-doxyl stearate spin label probe in a concentration-dependent manner. No change in mobility was apparent at CD concentrations below 0.2 mumol/mg protein. These results demonstrated that CD impaired a bile canalicular-specific transport system and induced liver plasma membrane perturbation. Na(+)-stimulated L-({sup 3}H)glutamate uptake was more sensitive to CD than was detectable immobilization of the spin label probe.

  17. Discovery and characterization of novel inhibitors of the sodium-coupled citrate transporter (NaCT or SLC13A5)

    PubMed Central

    Huard, Kim; Brown, Janice; Jones, Jessica C.; Cabral, Shawn; Futatsugi, Kentaro; Gorgoglione, Matthew; Lanba, Adhiraj; Vera, Nicholas B.; Zhu, Yimin; Yan, Qingyun; Zhou, Yingjiang; Vernochet, Cecile; Riccardi, Keith; Wolford, Angela; Pirman, David; Niosi, Mark; Aspnes, Gary; Herr, Michael; Genung, Nathan E.; Magee, Thomas V.; Uccello, Daniel P.; Loria, Paula; Di, Li; Gosset, James R.; Hepworth, David; Rolph, Timothy; Pfefferkorn, Jeffrey A.; Erion, Derek M.

    2015-01-01

    Citrate is a key regulatory metabolic intermediate as it facilitates the integration of the glycolysis and lipid synthesis pathways. Inhibition of hepatic extracellular citrate uptake, by blocking the sodium-coupled citrate transporter (NaCT or SLC13A5), has been suggested as a potential therapeutic approach to treat metabolic disorders. NaCT transports citrate from the blood into the cell coupled to the transport of sodium ions. The studies herein report the identification and characterization of a novel small dicarboxylate molecule (compound 2) capable of selectively and potently inhibiting citrate transport through NaCT, both in vitro and in vivo. Binding and transport experiments indicate that 2 specifically binds NaCT in a competitive and stereosensitive manner, and is recognized as a substrate for transport by NaCT. The favorable pharmacokinetic properties of 2 permitted in vivo experiments to evaluate the effect of inhibiting hepatic citrate uptake on metabolic endpoints. PMID:26620127

  18. Discovery and characterization of novel inhibitors of the sodium-coupled citrate transporter (NaCT or SLC13A5).

    PubMed

    Huard, Kim; Brown, Janice; Jones, Jessica C; Cabral, Shawn; Futatsugi, Kentaro; Gorgoglione, Matthew; Lanba, Adhiraj; Vera, Nicholas B; Zhu, Yimin; Yan, Qingyun; Zhou, Yingjiang; Vernochet, Cecile; Riccardi, Keith; Wolford, Angela; Pirman, David; Niosi, Mark; Aspnes, Gary; Herr, Michael; Genung, Nathan E; Magee, Thomas V; Uccello, Daniel P; Loria, Paula; Di, Li; Gosset, James R; Hepworth, David; Rolph, Timothy; Pfefferkorn, Jeffrey A; Erion, Derek M

    2015-12-01

    Citrate is a key regulatory metabolic intermediate as it facilitates the integration of the glycolysis and lipid synthesis pathways. Inhibition of hepatic extracellular citrate uptake, by blocking the sodium-coupled citrate transporter (NaCT or SLC13A5), has been suggested as a potential therapeutic approach to treat metabolic disorders. NaCT transports citrate from the blood into the cell coupled to the transport of sodium ions. The studies herein report the identification and characterization of a novel small dicarboxylate molecule (compound 2) capable of selectively and potently inhibiting citrate transport through NaCT, both in vitro and in vivo. Binding and transport experiments indicate that 2 specifically binds NaCT in a competitive and stereosensitive manner, and is recognized as a substrate for transport by NaCT. The favorable pharmacokinetic properties of 2 permitted in vivo experiments to evaluate the effect of inhibiting hepatic citrate uptake on metabolic endpoints.

  19. Insulin-stimulated Na/sup +/ transport in a model renal epithelium: protein synthesis dependence and receptor interactions

    SciTech Connect

    Blazer-Yost, B.L.; Cox, M.

    1987-05-01

    The urinary bladder of the toad, Bufo marinus, is a well characterized model of the mammalian distal nephron. Porcine insulin (approx. 0.5-5.0 ..mu..M) stimulates net mucosal to serosal Na/sup +/ flux within 10 minutes of hormone addition. The response is maintained for at least 5 hr and is completely abolished by low doses (10..mu..M) of the epithelial Na/sup +/ channel blocker amiloride. Insulin-stimulated Na/sup +/ transport does not require new protein synthesis since it is actinomycin-D (10..mu..g/ml) insensitive. Also in 3 separate experiments in which epithelial cell proteins were examined by /sup 35/S-methionine labeling, 2-dimensional polyacrylamide gel electrophoresis/autoradiography, no insulin induced proteins were observed. Equimolar concentrations of purified porcine proinsulin and insulin (0.64..mu..M) stimulate Na/sup +/ transport to the same extent. Thus, the putative toad insulin receptor may have different affinity characteristics than those demonstrated for insulin and proinsulin in mammalian tissues. Alternatively, the natriferic action of insulin in toad urinary bladders may be mediated by occupancy of another receptor. Preliminary experiments indicating that nanomolar concentrations of IGF/sub 1/ stimulate Na/sup +/ transport in this tissue support the latter contention.

  20. The alpha 1 Na(+)-K+ pump of the Dahl salt-sensitive rat exhibits altered Na+ modulation of K+ transport in red blood cells.

    PubMed

    Canessa, M; Romero, J R; Ruiz-Opazo, N; Herrera, V L

    1993-06-01

    The properties of the alpha 1 Na(+)-K+ pump were compared in Dahl salt-sensitive (DS) and salt-resistant (DR) strains by measuring ouabain-sensitive fluxes (mmol/liter cell x hr = FU, Mean +/- SE) in red blood cells (RBCs) and varying internal (i) and external (o) Na+ and K+ concentrations. Kinetic parameters of several modes of operation, i.e., Na+/K+, K+/K+, Na+/Na+ exchanges, were characterized and analyzed for curve-fitting using the Enzfitter computer program. In unidirectional flux studies (n = 12 rats of each strain) into fresh cells incubated in 140 mM Na(+) + 5 mM K+, ouabain-sensitive K+ influx was substantially lower in the DS than in DR RBCs, while ouabain-sensitive Na+ efflux and Nai were similar in both strains. Thus, the coupling ratio between unidirectional Na+:K+ fluxes was significantly higher in DS than in DR cells at similar RBC Na+ content. In the presence of 140 mM Nao, activation of ouabain-sensitive K+ influx by Ko had a lower Km and Vmax in DS as estimated by the Garay equation (N = 2.70 +/- 0.33, Km 0.74 +/- 0.09 mM; Vmax 2.87 +/- 0.09 FU) than in DR rats (N = 1.23 +/- 0.36, Km 2.31 +/- 0.16 mM; Vmax 5.70 +/- 0.52 FU). However, the two kinetic parameters were similar following Nao removal. The activation of ouabain-sensitive K+ influx by Nai had significantly lower Vmax in DS (9.3 +/- 0.4 FU) than in DR (14.5 +/- 0.6 FU) RBCs but similar Km. These data suggest that the low K+ influx in DS cells is caused by a defect in modulation by Nao and Nai. Na+ efflux showed no differences in Nai activation or trans effects by Nao and Ko, thus accounting for the different Na+:K+ coupling ratio in the Dahl strains. Further evidence for the differences in the coupling of ouabain-sensitive fluxes was found in studies of net Na+ and K+ fluxes, where the net ouabain-sensitive Na+ losses showed similar magnitudes in the two Dahl strains while the net ouabain-sensitive K+ gains were significantly greater in the DR than the DS RBCs. Ouabain-sensitive Na

  1. Effect of External Electric Field on Substrate Transport of a Secondary Active Transporter.

    PubMed

    Zhang, Ji-Long; Zheng, Qing-Chuan; Yu, Li-Ying; Li, Zheng-Qiang; Zhang, Hong-Xing

    2016-08-22

    Substrate transport across a membrane accomplished by a secondary active transporter (SAT) is essential to the normal physiological function of living cells. In the present research, a series of all-atom molecular dynamics (MD) simulations under different electric field (EF) strengths was performed to investigate the effect of an external EF on the substrate transport of an SAT. The results show that EF both affects the interaction between substrate and related protein's residues by changing their conformations and tunes the timeline of the transport event, which collectively reduces the height of energy barrier for substrate transport and results in the appearance of two intermediate conformations under the existence of an external EF. Our work spotlights the crucial influence of external EFs on the substrate transport of SATs and could provide a more penetrating understanding of the substrate transport mechanism of SATs. PMID:27472561

  2. Sustained Na+/H+ exchanger activation promotes gliotransmitter release from reactive hippocampal astrocytes following oxygen-glucose deprivation.

    PubMed

    Cengiz, Pelin; Kintner, Douglas B; Chanana, Vishal; Yuan, Hui; Akture, Erinc; Kendigelen, Pinar; Begum, Gulnaz; Fidan, Emin; Uluc, Kutluay; Ferrazzano, Peter; Sun, Dandan

    2014-01-01

    Hypoxia ischemia (HI)-related brain injury is the major cause of long-term morbidity in neonates. One characteristic hallmark of neonatal HI is the development of reactive astrogliosis in the hippocampus. However, the impact of reactive astrogliosis in hippocampal damage after neonatal HI is not fully understood. In the current study, we investigated the role of Na(+)/H(+) exchanger isoform 1 (NHE1) protein in mouse reactive hippocampal astrocyte function in an in vitro ischemia model (oxygen/glucose deprivation and reoxygenation, OGD/REOX). 2 h OGD significantly increased NHE1 protein expression and NHE1-mediated H(+) efflux in hippocampal astrocytes. NHE1 activity remained stimulated during 1-5 h REOX and returned to the basal level at 24 h REOX. NHE1 activation in hippocampal astrocytes resulted in intracellular Na(+) and Ca(2+) overload. The latter was mediated by reversal of Na(+)/Ca(2+) exchange. Hippocampal astrocytes also exhibited a robust release of gliotransmitters (glutamate and pro-inflammatory cytokines IL-6 and TNFα) during 1-24 h REOX. Interestingly, inhibition of NHE1 activity with its potent inhibitor HOE 642 not only reduced Na(+) overload but also gliotransmitter release from hippocampal astrocytes. The noncompetitive excitatory amino acid transporter inhibitor TBOA showed a similar effect on blocking the glutamate release. Taken together, we concluded that NHE1 plays an essential role in maintaining H(+) homeostasis in hippocampal astrocytes. Over-stimulation of NHE1 activity following in vitro ischemia disrupts Na(+) and Ca(2+) homeostasis, which reduces Na(+)-dependent glutamate uptake and promotes release of glutamate and cytokines from reactive astrocytes. Therefore, blocking sustained NHE1 activation in reactive astrocytes may provide neuroprotection following HI.

  3. Regulation of the mouse Na+-dependent glutamate/aspartate transporter GLAST: putative role of an AP-1 DNA binding site.

    PubMed

    Ramírez-Sotelo, Guadalupe; López-Bayghen, Esther; Hernández-Kelly, L Clara R; Arias-Montaño, J Antonio; Bernabé, Alfonso; Ortega, Arturo

    2007-01-01

    Appropriate removal of L: -glutamate from the synaptic cleft is important for prevention of the excitotoxic effects of this neurotransmitter. The Na+-dependent glutamate/aspartate transporter GLAST is regulated in the short term, by a transporter-dependent decrease in uptake activity while in the long term, a receptor's-dependent decrease in GLAST protein levels leads to a severe reduction in glutamate uptake. The promoter region of the mouse glast gene harbors an Activator Protein-1 site (AP-1). To gain insight into the molecular mechanisms triggered by Glu-receptors activation involved in GLAST regulation, we took advantage of the neonatal mouse cerebellar prisms model. We characterized the glutamate uptake activity; the glutamate-dependent effect on GLAST protein levels and over the interaction of nuclear proteins with a mouse glast promoter AP-1 probe. A time and dose dependent decrease in transporter activity matching with a decrease in GLAST levels was recorded upon glutamate treatment. Moreover, a significant increase in glast AP-1 DNA binding was found. Pharmacological experiments established that both effects are mediated through alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate receptors, favoring the notion of the critical involvement of glutamate in the regulation of its binding partners: receptors and transporters.

  4. Molecular simulation of thermodynamic and transport properties for the H2O+NaCl system.

    PubMed

    Orozco, Gustavo A; Moultos, Othonas A; Jiang, Hao; Economou, Ioannis G; Panagiotopoulos, Athanassios Z

    2014-12-21

    Molecular dynamics and Monte Carlo simulations have been carried out to obtain thermodynamic and transport properties of the binary mixture H2O+NaCl at temperatures from T = 298 to 473 K. In particular, vapor pressures, liquid densities, viscosities, and vapor-liquid interfacial tensions have been obtained as functions of pressure and salt concentration. Several previously proposed fixed-point-charge models that include either Lennard-Jones (LJ) 12-6 or exponential-6 (Exp6) functional forms to describe non-Coulombic interactions were studied. In particular, for water we used the SPC and SPC/E (LJ) models in their rigid forms, a semiflexible version of the SPC/E (LJ) model, and the Errington-Panagiotopoulos Exp6 model; for NaCl, we used the Smith-Dang and Joung-Cheatham (LJ) parameterizations as well as the Tosi-Fumi (Exp6) model. While none of the model combinations are able to reproduce simultaneously all target properties, vapor pressures are well represented using the SPC plus Joung-Cheathem model combination, and all LJ models do well for the liquid density, with the semiflexible SPC/E plus Joung-Cheatham combination being the most accurate. For viscosities, the combination of rigid SPC/E plus Smith-Dang is the best alternative. For interfacial tensions, the combination of the semiflexible SPC/E plus Smith-Dang or Joung-Cheatham gives the best results. Inclusion of water flexibility improves the mixture densities and interfacial tensions, at the cost of larger deviations for the vapor pressures and viscosities. The Exp6 water plus Tosi-Fumi salt model combination was found to perform poorly for most of the properties of interest, in particular being unable to describe the experimental trend for the vapor pressure as a function of salt concentration. PMID:25527948

  5. Molecular simulation of thermodynamic and transport properties for the H2O+NaCl system

    NASA Astrophysics Data System (ADS)

    Orozco, Gustavo A.; Moultos, Othonas A.; Jiang, Hao; Economou, Ioannis G.; Panagiotopoulos, Athanassios Z.

    2014-12-01

    Molecular dynamics and Monte Carlo simulations have been carried out to obtain thermodynamic and transport properties of the binary mixture H2O+NaCl at temperatures from T = 298 to 473 K. In particular, vapor pressures, liquid densities, viscosities, and vapor-liquid interfacial tensions have been obtained as functions of pressure and salt concentration. Several previously proposed fixed-point-charge models that include either Lennard-Jones (LJ) 12-6 or exponential-6 (Exp6) functional forms to describe non-Coulombic interactions were studied. In particular, for water we used the SPC and SPC/E (LJ) models in their rigid forms, a semiflexible version of the SPC/E (LJ) model, and the Errington-Panagiotopoulos Exp6 model; for NaCl, we used the Smith-Dang and Joung-Cheatham (LJ) parameterizations as well as the Tosi-Fumi (Exp6) model. While none of the model combinations are able to reproduce simultaneously all target properties, vapor pressures are well represented using the SPC plus Joung-Cheathem model combination, and all LJ models do well for the liquid density, with the semiflexible SPC/E plus Joung-Cheatham combination being the most accurate. For viscosities, the combination of rigid SPC/E plus Smith-Dang is the best alternative. For interfacial tensions, the combination of the semiflexible SPC/E plus Smith-Dang or Joung-Cheatham gives the best results. Inclusion of water flexibility improves the mixture densities and interfacial tensions, at the cost of larger deviations for the vapor pressures and viscosities. The Exp6 water plus Tosi-Fumi salt model combination was found to perform poorly for most of the properties of interest, in particular being unable to describe the experimental trend for the vapor pressure as a function of salt concentration.

  6. Active and passive Na+ fluxes across the basolateral membrane of rabbit urinary bladder.

    PubMed

    Eaton, D C; Frace, A M; Silverthorn, S U

    1982-01-01

    The apical membrane of rabbit urinary bladder can be functionally removed by application of nystatin at high concentration if the mucosal surface of the tissue is bathed in a saline which mimics intracellular ion concentrations. Under these conditions, the tissue is as far as the movement of univalent ions no more than a sheet of basolateral membrane with some tight junctional membrane in parallel. In this manner the Na+ concentration at the inner surface of the basolateral membrane can be varied by altering the concentration in the mucosal bulk solution. When this was done both mucosal-to-serosal 22Na flux and net change in basolateral current were measured. The flux and the current could be further divided into the components of each that were either blocked by ouabain or insensitive to ouabain. Ouabain-insensitive mucosal-to-serosal Na+ flux was a linear function of mucosal Na+ concentration. Ouabain-sensitive Na+ flux and ouabain-sensitive, Na+-induced current both display a saturating relationship which cannot be accounted for by the presence of unstirred layers. If the interaction of Na+ with the basolateral transport process is assumed to involve the interaction of some number of Na+ ions, n, with a maximal flux, MMAX, then the data can be fit by assuming 3.2 equivalent sites for interaction and a value for MMAX of 287.8 pM cm-2 sec-1 with an intracellular Na concentration of 2.0 mM Na+ at half-maximal saturation. By comparing these values with the ouabain-sensitive, Na+-induced current, we calculate a Na+ to K+ coupling ratio of 1.40 +/- 0.07 for the transport process.

  7. Volume-activated Na/H exchange activity in fetal and adult pig red cells: inhibition by cyclic AMP.

    PubMed

    Sergeant, S; Sohn, D H; Kim, H D

    1989-08-01

    Hyposmotic swelling of pig red cells leads to a selective increase in K permeability, whereas hyperosmotic cell shrinkage augments the Na permeability. In this regard, the ouabain-resistant (OR) Na flux of red cells of newborn and adult pigs is characterized in detail. A reduction in cell volume by approximately 18% leads to an increase in the OR Na efflux of fetal and adult cells by 15- and fourfold, respectively. The OR Na influx in both cell types is equally influenced by cell shrinkage. Depletion of cellular K does not influence the volume-activated OR Na efflux. Nor does OR Na influx require external K. Both OR Na efflux and influx activated by shrinkage are inhibited by the diuretics furosemide and amiloride. The rank order of decreasing anion sensitivity for diuretic-sensitive Na efflux was acetate greater than chloride greater than gluconate greater than nitrate. Cell shrinkage induced by the addition of hypertonic salts results in an acidification of the unbuffered and CO2-free media, provided that both Na and DIDS are present. The acidification process can be reversed by either of the diuretic agents. These findings suggest that the shrinkage-activated OR Na flux is primarily mediated by a Na/H exchanger rather than by a Na/K/Cl cotransporter. Once loaded with either cAMP or cGMP, cell swelling can no longer activate the Na/H exchanger. The Na/H exchanger activity is detectable in the fetal cells of normal volume but quiescent in adult cells, indicating that the exchanger undergoes a developmental change during the transition from the fetal to adult stage. PMID:2552123

  8. Study of active cooling for supersonic transports

    NASA Technical Reports Server (NTRS)

    Brewer, G. D.; Morris, R. E.

    1975-01-01

    The potential benefits of using the fuel heat sink of hydrogen fueled supersonic transports for cooling large portions of the aircraft wing and fuselage are examined. The heat transfer would be accomplished by using an intermediate fluid such as an ethylene glycol-water solution. Some of the advantages of the system are: (1) reduced costs by using aluminum in place of titanium, (2) reduced cabin heat loads, and (3) more favorable environmental conditions for the aircraft systems. A liquid hydrogen fueled, Mach 2.7 supersonic transport aircraft design was used for the reference uncooled vehicle. The cooled aircraft designs were analyzed to determine their heat sink capability, the extent and location of feasible cooled surfaces, and the coolant passage size and spacing.

  9. The active ion transport properties of canine lingual epithelia in vitro. Implications for gustatory transduction.

    PubMed

    Desimone, J A; Heck, G L; Mierson, S; Desimone, S K

    1984-05-01

    The electrophysiological properties of the dorsal and ventral canine lingual epithelium are studied in vitro. The dorsal epithelium contains a special ion transport system activated by mucosal solutions hyperosmotic in NaCl or LiCl. Hyperosmotic KCl is significantly less effective as an activator of this system. The lingual frenulum does not contain the transport system. In the dorsal surface it is characterized by a rapid increase in inward current and can be quantitated as a second component in the time course of either the open-circuit potential or short-circuit current when the mucosal solution is hyperosmotic in NaCl or LiCl. The increased inward current (hyperosmotic response) can be eliminated by amiloride (10(-4) M). The specific location of this transport system in the dorsal surface and the fact that it operates over the concentration range characteristic of mammalian salt taste suggests a possible link to gustatory transduction. This possibility is tested by recording neural responses in the rat to NaCl and KCl over a concentration range including the hyperosmotic. We demonstrate that amiloride specifically blocks the response to NaCl over the hyperosmotic range while affecting the KCl response significantly less. The results suggest that gustatory transduction for NaCl is mediated by Na entry into the taste cells via the same amiloride-sensitive pathway responsible for the hyperosmotic response in vitro. Further studies of the in vitro system give evidence for paracellular as well as transcellular current paths. The transmural current-voltage relations are linear under both symmetrical and asymmetrical conditions. After ouabain treatment under symmetrical conditions, the short-circuit current decays to zero. The increase in resistance, though significant, is small, which suggests a sizeable shunt pathway for current. Flux measurements show that sodium is absorbed under symmetrical conditions. Mucosal solutions hyperosmotic in various sugars also induce

  10. Organophosphate inhibition of avian salt gland Na, K-ATPase activity

    USGS Publications Warehouse

    Eastin, W.C.; Fleming, W.J.; Murray, H.C.

    1982-01-01

    1. Adult black ducks (Anas rubripes) were given freshwater or saltwater (1.5% NaCl) for 11 days and half of each group was also given an organophosphate (17 p.p.m. fenthion) in the diet on days 6-11. 2. After 11 days, ducks drinking saltwater had lost more weight and had higher plasma Na and uric acid concentrations and osmolalities than birds drinking freshwater. 3. Saltwater treatment stimulated the salt gland to increased weight and Na, K-ATPase activity. 4. Fenthion generally reduced plasma and brain cholinesterase activity and depressed cholinesterase and Na, K-ATPase activities in salt glands of birds drinking saltwater.

  11. /sup 22/Na+ and /sup 86/Rb+ transport in vascular smooth muscle of SHR, Wistar Kyoto, and Wistar rats

    SciTech Connect

    Kuriyama, S.; Denny, T.N.; Aviv, A.

    1988-06-01

    To gain further insight into differences in cellular Na+ and K+ regulation between the spontaneously hypertensive rat (SHR), Wistar Kyoto (WKY), and American Wistar (W) rats, 22Na+ and 86Rb+ washouts were performed under steady-state conditions in cultured vascular smooth muscle cells from the three rat strains. SHR vascular smooth muscle cells showed significantly higher bumetanide sensitive 86Rb+ washout rate constant (x 10(-4)/min; mean +/- SEM) than WKY cells (-38.6 +/- 2.84 and -23.8 +/- 3.58, respectively; p less than 0.005). SHR vascular smooth muscle cells also exhibited significantly higher values than WKY cells in the total 22Na+ washout rate constant (x 10(-2)/min) (-61.0 +/- 1.57 vs. -53.8 +/- 1.24; p less than 0.005). The amiloride sensitive component of the 22Na+ washout rate constant accounted for these differences (-18.6 +/- 1.04 for SHR and -12.1 +/- 2.00 for WKY; p less than 0.05). There were no apparent differences in cellular Na+ concentrations between WKY and SHR cells. In general, the 86Rb+ and 22Na+ washout parameters of W rat cells were quite similar to those of cells from SHR. We conclude that the bumetanide-sensitive 86Rb+ washout (the Na+ K+-cotransport), the overall, and the amiloride-sensitive 22Na+ washout (the latter primarily represents the Na+/H+ antiport) are higher in SHR than WKY rat vascular smooth muscle cells. These findings indicate innate differences in cellular Na+ and K+ transport in vascular smooth muscle cells of the SHR and WKY rat. The mechanisms responsible for these differences are yet to be determined.

  12. Na,K-ATPase activity in mouse muscle is regulated by AMPK and PGC-1α.

    PubMed

    Ingwersen, Maria S; Kristensen, Michael; Pilegaard, Henriette; Wojtaszewski, Jørgen F P; Richter, Erik A; Juel, Carsten

    2011-07-01

    Na,K-ATPase activity, which is crucial for skeletal muscle function, undergoes acute and long-term regulation in response to muscle activity. The aim of the present study was to test the hypothesis that AMP kinase (AMPK) and the transcriptional coactivator PGC-1α are underlying factors in long-term regulation of Na,K-ATPase isoform (α,β and PLM) abundance and Na(+) affinity. Repeated treatment of mice with the AMPK activator AICAR decreased total PLM protein content but increased PLM phosphorylation, whereas the number of α- and β-subunits remained unchanged. The K(m) for Na(+) stimulation of Na,K-ATPase was reduced (higher affinity) after AICAR treatment. PLM abundance was increased in AMPK kinase-dead mice compared with control mice, but PLM phosphorylation and Na,K-ATPase Na(+) affinity remained unchanged. Na,K-ATPase activity and subunit distribution were also measured in mice with different degrees of PGC-1α expression. Protein abundances of α1 and α2 were reduced in PGC-1α +/- and -/- mice, and the β(1)/β(2) ratio was increased with PGC-1α overexpression (TG mice). PLM protein abundance was decreased in TG mice, but phosphorylation status was unchanged. Na,K-ATPase V (max) was decreased in PCG-1α TG and KO mice. Experimentally in vitro induced phosphorylation of PLM increased Na,K-ATPase Na(+) affinity, confirming that PLM phosphorylation is important for Na,K-ATPase function. In conclusion, both AMPK and PGC-1α regulate PLM abundance, AMPK regulates PLM phosphorylation and PGC-1α expression influences Na,K-ATPase α(1) and α(2) content and β(1)/β(2) isoform ratio. Phosphorylation of the Na,K-ATPase subunit PLM is an important regulatory mechanism.

  13. Presynaptic Na+-dependent transport and exocytose of GABA and glutamate in brain in hypergravity.

    NASA Astrophysics Data System (ADS)

    Borisova, T.; Pozdnyakova, N.; Krisanova, N.; Himmelreich, N.

    γ-Aminobutyric acid (GABA) and L-glutamate are the most widespread neurotransmitter amino acids in the mammalian central nervous system. GABA is now widely recognized as the major inhibitory neurotransmitter. L-glutamate mediates the most of excitatory synaptic neurotransmission in the brain. They involved in the main aspects of normal brain function. The nerve terminals (synaptosomes) offer several advantages as a model system for the study of general mechanisms of neurosecretion. Our data allowed to conclude that exposure of animals to hypergravity (centrifugation of rats at 10G for 1 hour) had a profound effect on synaptic processes in brain. Comparative analysis of uptake and release of GABA and glutamate have demonstrated that hypergravity loading evokes oppositely directed alterations in inhibitory and excitatory signal transmission. We studied the maximal velocities of [^3H]GABA reuptake and revealed more than twofold enhancement of GABA transporter activity (Vmax rises from 1.4 |pm 0.3 nmol/min/mg of protein in the control group to 3.3 ± 0.59 nmol/min/mg of protein for animals exposed to hypergravity (P ≤ 0.05)). Recently we have also demonstrated the significant lowering of glutamate transporter activity (Vmax of glutamate reuptake decreased from 12.5 ± 3.2 nmol/min/mg of protein in the control group to 5.6 ± 0.9 nmol/min/mg of protein in the group of animals, exposed to the hypergravity stress (P ≤ 0.05)). Significant changes occurred in release of neurotransmitters induced by stimulating exocytosis with the agents, which depolarized nerve terminal plasma membrane. Depolarization-evoked Ca2+-stimulated release was more abundant for GABA (7.2 ± 0.54% and 11,74 ±1,2 % of total accumulated label for control and hypergravity, respectively (P≤0.05)) and was essentially less for glutamate (14.4 ± 0.7% and 6.2 ± 1.9%) after exposure of animals to centrifuge induced artificial gravity. Changes observed in depolarization-evoked exocytotic release

  14. An Abiotic Glass-Bead Collector Exhibiting Active Transport

    PubMed Central

    Goto, Youhei; Kanda, Masato; Yamamoto, Daigo; Shioi, Akihisa

    2015-01-01

    Animals relocate objects as needed by active motion. Active transport is ubiquitous in living organisms but has been difficult to realize in abiotic systems. Here we show that a self-propelled droplet can gather scattered beads toward one place on a floor and sweep it clean. This is a biomimetic active transport with loadings and unloadings, because the transport was performed by a carrier and the motion of the carrier was maintained by the energy of the chemical reaction. The oil droplet produced fluctuation of the local number density of the beads on the floor, followed by its autocatalytic growth. This mechanism may inspire the technologies based on active transport wherein chemical and physical substances migrate as in living organisms. PMID:26387743

  15. An Abiotic Glass-Bead Collector Exhibiting Active Transport

    NASA Astrophysics Data System (ADS)

    Goto, Youhei; Kanda, Masato; Yamamoto, Daigo; Shioi, Akihisa

    2015-09-01

    Animals relocate objects as needed by active motion. Active transport is ubiquitous in living organisms but has been difficult to realize in abiotic systems. Here we show that a self-propelled droplet can gather scattered beads toward one place on a floor and sweep it clean. This is a biomimetic active transport with loadings and unloadings, because the transport was performed by a carrier and the motion of the carrier was maintained by the energy of the chemical reaction. The oil droplet produced fluctuation of the local number density of the beads on the floor, followed by its autocatalytic growth. This mechanism may inspire the technologies based on active transport wherein chemical and physical substances migrate as in living organisms.

  16. Space transportation activities in the United States

    NASA Technical Reports Server (NTRS)

    Gabris, Edward A.

    1994-01-01

    The status of the existing space transportation systems in the U.S. and options for increased capability is being examined in the context of mission requirements, options for new vehicles, cost to operate the existing vehicles, cost to develop new vehicles, and the capabilities and plans of other suppliers. This assessment is addressing the need to build and resupply the space station, to maintain necessary military assets in a rapidly changing world, and to continue a competitive commercial space transportation industry. The Department of Defense (DOD) and NASA each conducted an 'access to space' study using a common mission model but with the emphasis on their unique requirements. Both studies considered three options: maintain and improve the existing capability, build a new launch vehicle using contemporary technology, and build a new launch vehicle using advanced technology. While no decisions have been made on a course of action, it will be influenced by the availability of funds in the U.S. budget, the changing need for military space assets, the increasing competition among space launch suppliers, and the emerging opportunity for an advanced technology, low cost system and international partnerships to develop it.

  17. Rapid activation of gill Na+,K+-ATPase in the euryhaline teleost Fundulus heteroclitus

    USGS Publications Warehouse

    Mancera, J.M.; McCormick, S.D.

    2000-01-01

    The rapid activation of gill Na+,K+-ATPase was analyzed in the mummichog (Fundulus heteroclitus) and Atlantic salmon (Salmo salar) transferred from low salinity (0.1 ppt) to high salinity (25-35 ppt). In parr and presmolt, Salmo salar gill Na+,K+-ATPase activity started to increase 3 days after transfer. Exposure of Fundulus heteroclitus to 35 ppt seawater (SW) induced a rise in gill Na+,K+-ATPase activity 3 hr after transfer. After 12 hr, the values dropped to initial levels but showed a second significant increase 3 days after transfer. The absence of detergent in the enzyme assay resulted in lower values of gill Na+,K+-ATPase, and the rapid increase after transfer to SW was not observed. Na+,K+-ATPase activity of gill filaments in vitro for 3 hr increased proportionally to the osmolality of the culture medium (600 mosm/kg > 500 mosm/kg > 300 mosm/kg). Osmolality of 800 mosm/kg resulted in lower gill Na+,K+-ATPase activity relative to 600 mosm/kg. Increasing medium osmolality to 600 mosm/kg with mannitol also increased gill Na+,K+-ATPase. Cycloheximide inhibited the increase in gill Na+,K+-ATPase activity observed in hyperosmotic medium in a dose-dependent manner (10-4 M > 10-5 M > 10-6 M). Actinomycin D or bumetanide in the culture (doses of 10-4 M, 10-5 M, and 10-6 M) did not affect gill Na+,K+-ATPase. Injection of fish with actinomycin D prior to gill organ culture, however, prevented the increase in gill Na+,K+-ATPase activity in hyperosmotic media. The results show a very rapid and transitory increase in gill Na+,K+-ATPase activity in the first hours after the transfer of Fundulus heteroclitus to SW that is dependent on translational and transcriptional processes. (C) 2000 Wiley-Liss, Inc.

  18. Overexpression of a novel soybean gene modulating Na+ and K+ transport enhances salt tolerance in transgenic tobacco plants.

    PubMed

    Chen, Huatao; He, Hui; Yu, Deyue

    2011-01-01

    Salt is an important factor affecting the growth and development of soybean in saline soil. In this study, a novel soybean gene encoding a transporter (GmHKT1) was identified and its function analyzed using transgenic plants. GmHKT1 encoded a protein of 419 amino acids, with a potential molecular mass of 47.06 kDa and a predicted pI value of 8.59. Comparison of the genomic and cDNA sequences of GmHKT1 identified no intron. The deduced amino acid sequence of GmHKT1 showed 38-49% identity with other plant HKT-like sequences. RT-PCR analysis showed that the expression of GmHKT1 was upregulated by salt stress (150 mM NaCl) in roots and leaves but not in stems. Overexpression of GmHKT1 significantly enhanced the tolerance of transgenic tobacco plants to salt stress, compared with non-transgenic plants. To investigate the role of GmHKT1 in K(+) and Na(+) transport, we compared K(+) and Na(+) accumulation in roots and shoots of wild-type and transgenic tobacco plants. The results suggested that GmHKT1 is a transporter that affected K(+) and Na(+) transport in roots and shoots, and regulated Na(+) /K(+) homeostasis in these organs. Our findings suggest that GmHKT1 plays an important role in response to salt stress and would be useful in engineering crop plants for enhanced tolerance to salt stress.

  19. The Na+/K(+)-pump in rat peritoneal mast cells: some aspects of regulation of activity and cellular function.

    PubMed

    Knudsen, T

    1995-11-01

    from the mast cell in a calcium-free medium, while there is no effect of digitalis glycosides in a medium containing physiologically relevant concentrations of calcium. The effect of digitalis glycosides on the histamine release is dependent on the drug concentrations used and the time of preincubation. An increase in the intracellular concentration of sodium secondary to inhibition of the Na+/K(+)-pump is the effector mechanism likely to explain the effect of digitalis glycosides on the mast cell histamine release. Increases in intracellular sodium might affect the intracellular concentration of calcium via changes in Na+/Ca(2+)-exchange. IgE-directed and non-IgE-directed stimulation of the mast cell activates the Na+/K(+)-pump. In case of compound 48/80-induced histamine release, the pump is stimulated for at least 2 hr. It is proposed, that the poststimulatory activation of the Na+/K(+)-pump is due to increased cellular sodium uptake associated with the release process. This sodium uptake may occur via Na+/Ca(2+)-exchange, Na+/H(+)-exchange, Na+/K+/2Cl(-)-cotransport or a non-selective ion channel. Besides describing aspects of the function and regulation of the Na+/K(+)-pump in the rat peritoneal mast cells, this thesis points to the potential role of sodium transport mechanisms in mast cell physiology. Pharmacological manipulations of such transport mechanisms might in the future add to the treatment of allergic diseases.

  20. Entropic Ratchet transport of interacting active Brownian particles

    SciTech Connect

    Ai, Bao-Quan; He, Ya-Feng; Zhong, Wei-Rong

    2014-11-21

    Directed transport of interacting active (self-propelled) Brownian particles is numerically investigated in confined geometries (entropic barriers). The self-propelled velocity can break thermodynamical equilibrium and induce the directed transport. It is found that the interaction between active particles can greatly affect the ratchet transport. For attractive particles, on increasing the interaction strength, the average velocity first decreases to its minima, then increases, and finally decreases to zero. For repulsive particles, when the interaction is very weak, there exists a critical interaction at which the average velocity is minimal, nearly tends to zero, however, for the strong interaction, the average velocity is independent of the interaction.

  1. Discrimination between citrulline and arginine transport in activated murine macrophages: inefficient synthesis of NO from recycling of citrulline to arginine.

    PubMed Central

    Baydoun, A. R.; Bogle, R. G.; Pearson, J. D.; Mann, G. E.

    1994-01-01

    1. The kinetics, specificity, pH- and Na(+)-dependency of L-citrulline transport were examined in unstimulated and lipopolysaccharide (LPS)-activated murine macrophage J774 cells. The dependency of nitric oxide production on extracellular arginine or citrulline was investigated in cells activated with LPS (1 microgram ml-1) for 24 h. 2. In unstimulated J774 cells, transport of citrulline was saturable (Kt = 0.16 mM and Vmax = 32 pmol micrograms-1 protein min-1), pH-insensitive and partially Na(+)-dependent. In contrast to arginine, transport of citrulline was unchanged in LPS-activated (1 microgram ml-1, 24 h) cells. 3. Kinetic inhibition experiments revealed that arginine was a relatively poor inhibitor of citrulline transport, whilst citrulline was a more potent inhibitor (Ki = 3.4 mM) of arginine transport but only in the presence of extracellular Na+. Neutral amino acids inhibited citrulline transport (Ki = 0.2-0.3 mM), but were poor inhibitors of arginine transport. 4. Activated J774 cells did not release nitrite in the absence of exogenous arginine. Addition of citrulline (0.01-10 mM), in the absence of exogenous arginine, could only partially restore the ability of cells to synthesize nitrite, which was abolished by 100 microM NG-nitro-L-arginine methyl ester or NG-iminoethyl-L-ornithine. 5. Intracellular metabolism of L-[14C]-citrulline to L-[14C]-arginine was detected in unstimulated J774 cells and was increased further in cells activated with LPS and interferon-gamma. 6. We conclude that J774 macrophage cells transport citrulline via a saturable but nonselective neutral carrier which is insensitive to induction by LPS.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8075867

  2. Light-activated amino acid transport in Halobacterium halobium envelope vesicles

    NASA Technical Reports Server (NTRS)

    Macdonald, R. E.; Lanyi, J. K.

    1977-01-01

    Vesicles prepared from Halobacterium halobium cell envelopes accumulate amino acids in response to light-induced electrical and chemical gradients. Nineteen of 20 commonly occurring amino acids have been shown to be actively accumulated by these vesicles in response to illumination or in response to an artificially created Na+ gradient. On the basis of shared common carriers the transport systems can be divided into eight classes, each responsible for the transport of one or several amino acids: arginine, lysine, histidine; asparagine, glutamine; alanine, glycine, threonine, serine; leucine, valine, isoleucine, methionine; phenylalanine, tyrosine, tryptophan; aspartate; glutamate; proline. Available evidence suggests that these carriers are symmetrical in that amino acids can be transported equally well in both directions across the vesicle membranes. A tentative working model to account for these observations is presented.

  3. The effect of juvenile hormone III, methyl farnesoate, and methoprene on Na/K-ATPase activity in larvae of the brine shrimp, Artemia.

    PubMed

    Ahl, J S; Brown, J J

    1991-01-01

    1. Ion transport enzyme (Na/K-ATPase) activity in stage III larvae of the brine shrimp, Artemia, remains elevated throughout the stadium when populations are exposed to methoprene in artificial seawater. 2. Infusion of methoprene, juvenile hormone, or methyl farnesoate causes increased Na/K-ATPase activity in homogenates of mid-stadium larvae that would otherwise exhibit low activity. 3. The sensitivity of the enzyme system to extremely low concentrations of the juvenoids suggests that this may be a common mode of action of these compounds. Additionally it suggests that the enzyme may be under the influence of a similar compound present in the larvae. PMID:1682091

  4. Nitrite Transport Activity of the ABC-Type Cyanate Transporter of the Cyanobacterium Synechococcus elongatus▿

    PubMed Central

    Maeda, Shin-ichi; Omata, Tatsuo

    2009-01-01

    In addition to the ATP-binding cassette (ABC)-type nitrate/nitrite-bispecific transporter, which has a high affinity for both substrates (Km, ∼1 μM), Synechococcus elongatus has an active nitrite transport system with an apparent Km (NO2−) value of 20 μM. We found that this activity depends on the cynABD genes, which encode a putative cyanate (NCO−) ABC-type transporter. Accordingly, nitrite transport by CynABD was competitively inhibited by NCO− with a Ki value of 0.025 μM. The transporter was induced under conditions of nitrogen deficiency, and the induced cells showed a Vmax value of 11 to 13 μmol/mg of chlorophyll per h for cyanate or nitrite, which could supply ∼30% of the amount of nitrogen required for optimum growth. Its relative specificity for the substrates and regulation at transcriptional and posttranslational levels suggested that the physiological role of the bispecific cyanate/nitrite transporter in S. elongatus is to allow nitrogen-deficient cells to assimilate low concentrations of cyanate in the medium. Its contribution to nitrite assimilation was significant in a mutant lacking the ABC-type nitrate/nitrite transporter, suggesting a possible role for CynABD in nitrite assimilation by cyanobacterial species that lack another high-affinity mechanism(s) for nitrite transport. PMID:19286804

  5. Passive and active ion transport by the urinary bladder of a euryhaline flounder.

    PubMed

    Demarest, J R; Machen, T E

    1984-04-01

    The effects of voltage clamping on the flux ratios and unidirectional and net fluxes of Na and Cl were used to gain insight into the mechanisms of active and passive ion transport across urinary bladders isolated from seawater-(SW) and freshwater-acclimated (FW) flounder, Platichthys stellatus. Although the transepithelial conductance (Gt = 2.77 mS X cm-2) of FW bladders was much greater than that of SW bladders (Gt = 0.40 mS X cm-2), the current-voltage relationships of both SW and FW bladders were markedly nonlinear. Under short-circuit conditions there was a large difference in the serosal-to-mucosal Na flux (JNasm) between SW (0.10 mueq X cm-2 X h-1) and FW (1.71 mueq X cm-2 X h-1) bladders, but their mannitol permeabilities were identical. The results indicate that 1) the paracellular pathway of both SW and FW bladders is Cl selective and Cl movements through the shunt account for a maximum of 90% of Gt in SW bladders and 19% in FW bladders; 2) the larger Gt of FW bladders is due to greater conductance of the apical cell membrane; 3) the majority of the passive ion movement across these epithelia proceeds through nonconductive, presumably transcellular, pathways; and 4) active transport of Na and Cl occurs by neutral coupling to each other and to other unidentified ions.

  6. Studies on lipids and the activity of Na,K-ATPase in lens fibre cells.

    PubMed Central

    Dean, W L; Delamere, N A; Borchman, D; Moseley, A E; Ahuja, R P

    1996-01-01

    Na,K-ATPase was studied in the two cell types that make up the lens of the eye. Membrane material was isolated from lens fibre cells, which make up the bulk of the lens cell mass, and also from lens epithelial cells, which are present only as a monolayer on the anterior lens surface. Judged by immunoblotting, greater amounts of Na,K-ATPase alpha1 and beta1 polypeptides were found in fibre cell membrane material than in epithelial cell membrane material. However, the NA,K-ATPase activity in epithelial cell membrane material was 20 times that measured in fibre cell membrane material. In 86Rb uptake experiments with intact lenses, ouabain-inhibitable 86Rb uptake was observed for lens epithelium but not for lens fibres. These findings are consistent with a low Na,K-ATPase activity in lens fibre cells even though these cells express a considerable amount of Na,K-ATPase alpha1 and beta1 polypeptides. The lipid composition of lens fibre cell membranes causes them to be more ordered than epithelial cell membranes; this was confirmed by measurements of the infrared CH2 symmetric stretching band frequency. Because lipid composition can influence Na,K-ATPase activity, experiments were conducted to determine whether the activity of Na,K-ATPase alpha1 beta1 is inhibited by lens fibre lipid. However, no significant difference in Na,K-ATPase activity was detected when Na,K-ATPase alpha1 beta1 was purified from rabbit kidney and then reconstituted with lipid that had been isolated from either lens epithelium or lens fibre cells. These studies indicate that lens fibre cells contain both Na,K-ATPase alpha1 and beta1 polypeptides but have low Na,K-ATPase activity. However, the results do not support the notion that this is due to the lipid composition of lens fibre cell membranes. PMID:8615795

  7. Classroom Activities in Transportation: Technology Education.

    ERIC Educational Resources Information Center

    Wisconsin State Dept. of Public Instruction, Madison.

    This curriculum supplement was designed to correlate directly with "A Guide to Curriculum Planning in Technology Education," published by the Wisconsin Department of Public Instruction. It is also a companion book to three other classroom activity compilations, one in each of the other three major systems of technology--manufacturing,…

  8. L-leucine, L-methionine, and L-phenylalanine share a Na(+)/K (+)-dependent amino acid transporter in shrimp hepatopancreas.

    PubMed

    Duka, Ada; Ahearn, Gregory A

    2013-08-01

    max in the same medium. These results suggest that shrimp BBMV transport (3)H-L-leucine by a single L-methionine- and L-phenylalanine-shared carrier system that is enhanced by acidic pH and can be stimulated by either Na(+) or K(+) acting as co-transport drivers binding to shared activator sites.

  9. Caulis Sinomenii extracts activate DA/NE transporter and inhibit 5HT transporter.

    PubMed

    Zhao, Gang; Bi, Cheng; Qin, Guo-Wei; Guo, Li-He

    2009-08-01

    Caulis Sinomenii (QFT) has analgesic, sedative, and anxiolytic-like actions, and is proven effective for improving drug dependence that is known to be associated with abnormal monoaminergic transmission. We assessed whether QFT would be biologically active in functionally regulating monoamine transporters using CHO cells expressing dopamine transporter (DAT), norepinephrine transporter (NET), or serotonin transporter (SERT) (i.e. D8, N1, or S6 cells, respectively). Here, we showed that its primary extracts, such as QA, QC, QE, QD, and QB (QFT ethanol, chloroform, ethyl acetate, alkaloid-free chloroform, and alkaloid-containing chloroform extract, respectively), and secondary extracts, such as QE-2, - 3, - 5, - 7, QD-1, - 2, - 3, - 4, - 5, and QB-1, - 2, - 3, - 4, - 5 (fractioned from QE, QD, and QB, respectively), in differing degrees, either increased DA/ NE uptake by corresponding D8/N1 cells or decreased 5HT uptake by S6 cells; wherein, QE-2, QD-3, and QE-7 were potent DA/NE uptake activators while both QE-7 and QB-5 were potent 5HT uptake inhibitors. Furthermore, the enhancement of DA/NE uptake was dependent of DAT/NET activity, and the inhibition of 5HT uptake was typical of competition. Thus, QFT extracts, especially QE-2 and QE-7 (both with stronger potencies), are novel monoamine transporter modulators functioning as DAT/ NET activators and/or SERT inhibitors, and would likely improve neuropsychological disorders through regulating monoamine transporters.

  10. Girls' perception of physical environmental factors and transportation: reliability and association with physical activity and active transport to school

    PubMed Central

    Evenson, Kelly R; Birnbaum, Amanda S; Bedimo-Rung, Ariane L; Sallis, James F; Voorhees, Carolyn C; Ring, Kimberly; Elder, John P

    2006-01-01

    Background Preliminary evidence suggests that the physical environment and transportation are associated with youth physical activity levels. Only a few studies have examined the association of physical environmental factors on walking and bicycling to school. Therefore, the purpose of this study was (1) to examine the test-retest reliability of a survey designed for youth to assess perceptions of physical environmental factors (e.g. safety, aesthetics, facilities near the home) and transportation, and (2) to describe the associations of these perceptions with both physical activity and active transport to school. Methods Test and retest surveys, administered a median of 12 days later, were conducted with 480 sixth- and eighth-grade girls in or near six U.S. communities. The instrument consisted of 24 questions on safety and aesthetics of the perceived environment and transportation and related facilities. Additionally, girls were asked if they were aware of 14 different recreational facilities offering structured and unstructured activities, and if so, whether they would visit these facilities and the ease with which they could access them. Test-retest reliability was determined using kappa coefficients, overall and separately by grade. Associations with physical activity and active transport to school were examined using mixed model logistic regression (n = 610), adjusting for grade, race/ethnicity, and site. Results Item-specific reliabilities for questions assessing perceived safety and aesthetics of the neighborhood ranged from 0.31 to 0.52. Reliabilities of items assessing awareness of and interest in going to the 14 recreational facilities ranged from 0.47 to 0.64. Reliabilities of items assessing transportation ranged from 0.34 to 0.58. Some items on girls' perceptions of perceived safety, aesthetics of the environment, facilities, and transportation were important correlates of physical activity and, in some cases, active transport to school. Conclusion

  11. Ezrin regulates NHE3 translocation and activation after Na+-glucose cotransport

    PubMed Central

    Zhao, Huiren; Shiue, Harn; Palkon, Sara; Wang, Yingmin; Cullinan, Patrick; Burkhardt, Janis K.; Musch, Mark W.; Chang, Eugene B.; Turner, Jerrold R.

    2004-01-01

    Initiation of Na+-glucose cotransport in intestinal epithelial cells leads to activation of the apical Na+-H+ exchanger NHE3 and subsequent increases in cytoplasmic pH (pHi). This process requires activation of p38 mitogen-activated protein (MAP) kinase, but additional signaling intermediates have not been identified. One candidate is the cytoskeletal linker protein ezrin, which interacts with NHE3 via specific regulatory proteins. The data show that initiation of Na+-glucose cotransport resulted in rapid increases in both apical membrane-associated NHE3 and cytoskeletal-associated ezrin and occurred in parallel with ezrin phosphorylation at threonine 567. Phosphorylation at this site is known to activate ezrin and increase its association with actin. Consistent with a central role for ezrin activation in this NHE3 regulation, an N-terminal dominant negative ezrin construct inhibited both NHE3 recruitment and pHi increases after Na+-glucose cotransport. Ezrin phosphorylation occurred in parallel with p38 MAP kinase activation, and the latter proceeded normally in cells expressing dominant negative ezrin. In contrast, inhibition of p38 MAP kinase prevented increases in ezrin phosphorylation after initiation of Na+-glucose cotransport. Thus, ezrin phosphorylation after Na+-glucose cotransport requires p38 MAP kinase activity, but p38 MAP kinase activation does not require ezrin function. These data describe a specific role for ezrin in the coordinate regulation of Na+-glucose cotransport and Na+-H+ exchange. Intact ezrin function is necessary for NHE3 recruitment to the apical membrane and NHE3-dependent pHi increases triggered by Na+-glucose cotransport. The data also define a pathway of p38 MAP kinase-dependent ezrin activation. PMID:15197272

  12. Suppression of Na+/K+-ATPase activity during estivation in the land snail Otala lactea.

    PubMed

    Ramnanan, Christopher J; Storey, Kenneth B

    2006-02-01

    Entry into the hypometabolic state of estivation requires a coordinated suppression of the rate of cellular ATP turnover, including both ATP-generating and ATP-consuming reactions. As one of the largest consumers of cellular ATP, the plasma membrane Na+/K+-ATPase is a potentially key target for regulation during estivation. Na+/K+-ATPase was investigated in foot muscle and hepatopancreas of the land snail Otala lactea, comparing active and estivating states. In both tissues enzyme properties changed significantly during estivation: maximal activity was reduced by about one-third, affinity for Mg.ATP was reduced (Km was 40% higher), and activation energy (derived from Arrhenius plots) was increased by approximately 45%. Foot muscle Na+/K+-ATPase from estivated snails also showed an 80% increase in Km Na+ and a 60% increase in Ka Mg2+ as compared with active snails, whereas hepatopancreas Na+/K+-ATPase showed a 70% increase in I50 K+ during estivation. Western blotting with antibodies recognizing the alpha subunit of Na+/K+-ATPase showed no change in the amount of enzyme protein during estivation. Instead, the estivation-responsive change in Na+/K+-ATPase activity was linked to posttranslational modification. In vitro incubations manipulating endogenous kinase and phosphatase activities indicated that Na+/K+-ATPase from estivating snails was a high phosphate, low activity form, whereas dephosphorylation returned the enzyme to a high activity state characteristic of active snails. Treatment with protein kinases A, C or G could all mediate changes in enzyme properties in vitro that mimicked the effect of estivation, whereas treatments with protein phosphatase 1 or 2A had the opposite effect. Reversible phosphorylation control of Na+/K+-ATPase can provide the means of coordinating ATP use by this ion pump with the rates of ATP generation by catabolic pathways in estivating snails. PMID:16449562

  13. Active Transportation to School: Findings from a National Survey

    ERIC Educational Resources Information Center

    Fulton, Janet E.; Shisler, Jessica L.; Yore, Michelle M.; Caspersen, Carl J.

    2005-01-01

    In the past, active transportation to school offered an important source of daily physical activity for youth; more recently, however, factors related to distance, safety, or physical or social environments may have contributed to the proportion of children who travel to school by motorized vehicle. The authors examine the characteristics of…

  14. Coupling of active motion and advection shapes intracellular cargo transport.

    PubMed

    Khuc Trong, Philipp; Guck, Jochen; Goldstein, Raymond E

    2012-07-13

    Intracellular cargo transport can arise from passive diffusion, active motor-driven transport along cytoskeletal filament networks, and passive advection by fluid flows entrained by such cargo-motor motion. Active and advective transport are thus intrinsically coupled as related, yet different representations of the same underlying network structure. A reaction-advection-diffusion system is used here to show that this coupling affects the transport and localization of a passive tracer in a confined geometry. For sufficiently low diffusion, cargo localization to a target zone is optimized either by low reaction kinetics and decoupling of bound and unbound states, or by a mostly disordered cytoskeletal network with only weak directional bias. These generic results may help to rationalize subtle features of cytoskeletal networks, for example as observed for microtubules in fly oocytes.

  15. Leishmania amazonensis: PKC-like protein kinase modulates the (Na++K+)ATPase activity.

    PubMed

    Almeida-Amaral, Elmo Eduardo de; Caruso-Neves, Celso; Lara, Lucienne Silva; Pinheiro, Carla Mônica; Meyer-Fernandes, José Roberto

    2007-08-01

    The present study aimed to identify the presence of protein kinase C-like (PKC-like) in Leishmania amazonensis and to elucidate its possible role in the modulation of the (Na(+)+K(+))ATPase activity. Immunoblotting experiments using antibody against a consensus sequence (Ac 543-549) of rabbit protein kinase C (PKC) revealed the presence of a protein kinase of 80 kDa in L. amazonensis. Measurements of protein kinase activity showed the presence of both (Ca(2+)-dependent) and (Ca(2+)-independent) protein kinase activity in plasma membrane and cytosol. Phorbol ester (PMA) activation of the Ca(2+)-dependent protein kinase stimulated the (Na(+)+K(+))ATPase activity, while activation of the Ca(2+)-independent protein kinase was inhibitory. Both effects of protein kinase on the (Na(+)+K(+))ATPase of the plasma membrane were lower than that observed in intact cells. PMA induced the translocation of protein kinase from cytosol to plasma membrane, indicating that the maximal effect of protein kinase on the (Na(+)+K(+))ATPase activity depends on the synergistic action of protein kinases from both plasma membrane and cytosol. This is the first demonstration of a protein kinase activated by PMA in L. amazonensis and the first evidence for a possible role in the regulation of the (Na(+)+K(+))ATPase activity in this trypanosomatid. Modulation of the (Na(+)+K(+))ATPase by protein kinase in a trypanosomatid opens up new possibilities to understand the regulation of ion homeostasis in this parasite. PMID:17475255

  16. Role of the transmembrane and extracytoplasmic domain of beta subunits in subunit assembly, intracellular transport, and functional expression of Na,K-pumps

    PubMed Central

    1993-01-01

    The ubiquitous Na,K- and the gastric H,K-pumps are heterodimeric plasma membrane proteins composed of an alpha and a beta subunit. The H,K- ATPase beta subunit (beta HK) can partially act as a surrogate for the Na,K-ATPase beta subunit (beta NK) in the formation of functional Na,K- pumps (Horisberger et al., 1991. J. Biol. Chem. 257:10338-10343). We have examined the role of the transmembrane and/or the ectodomain of beta NK in (a) its ER retention in the absence of concomitant synthesis of Na,K-ATPase alpha subunits (alpha NK) and (b) the functional expression of Na,K-pumps at the cell surface and their activation by external K+. We have constructed chimeric proteins between Xenopus beta NK and rabbit beta HK by exchanging their NH2-terminal plus transmembrane domain with their COOH-terminal ectodomain (beta NK/HK, beta HK/NK). We have expressed these constructs with or without coexpression of alpha NK in the Xenopus oocyte. In the absence of alpha NK, Xenopus beta NK and all chimera that contained the ectodomain of beta NK were retained in the ER while beta HK and all chimera with the ectodomain of beta HK could leave the ER suggesting that ER retention of unassembled Xenopus beta NK is mediated by a retention signal in the ectodomain. When coexpressed with alpha NK, only beta NK and beta NK/HK chimera assembled efficiently with alpha NK leading to similar high expression of functional Na,K-pumps at the cell surface that exhibited, however, a different apparent K+ affinity. beta HK or chimera with the transmembrane domain of beta HK assembled less efficiently with alpha NK leading to lower expression of functional Na,K-pumps with a different apparent K+ affinity. The data indicate that the transmembrane domain of beta NK is important for efficient assembly with alpha NK and that both the transmembrane and the ectodomain of beta subunits play a role in modulating the transport activity of Na,K- pumps. PMID:8276895

  17. Oxygen consumption and active sodium and chloride transport in bovine tracheal epithelium.

    PubMed Central

    Durand, J; Durand-Arczynska, W; Schoenenweid, F

    1986-01-01

    The O2 consumption (Jr) and the short-circuit current (Ji) were measured simultaneously in bovine tracheal epithelium in vitro. In this tissue, Ji is the sum of two active transport processes, Cl- secretion and Na+ absorption. Jr was determined from the decrease of PO2 in the incubation solution, at 37 +/- 0.05 degrees C and at a PO2 around 600 torr. Microbial contamination and leaks of dissolved O2 from the solution never exceeded 4% of the rate of PO2 decrease due to the O2 consumption of the tissue. Ji and Jr were stable over 5 h of incubation under standard conditions. Ji was 106 +/- 4 nequiv min-1 cm-2 and Jr was 39.8 +/- 1.1 nmol O2 min-1 cm-2 (mean +/- S.E., n = 46). Ji was varied with several agents known to affect ion transport across the tracheal epithelium. Na+ absorption was inhibited partly with amiloride or completely following Na+ substitution with choline. Cl- secretion was selectively suppressed by furosemide. Ji was also reduced to a very low level, using ouabain or K+ suppression to inhibit the Na+-K+-ATPase. All these manoeuvres resulted in significant reductions of both Ji and Jr. Basal Jr was not affected when Ji was modified. A plot of the relative change in suprabasal Jr versus the relative change of Ji gave a straight line (r = 0.98, n = 60). A plot using absolute values yielded a stoichiometric ratio of 13.9 ions per O2 molecule, for Na+ as well as for Cl-. The stoichiometric ratio was also calculated for each experiment. Its mean value was 14.9 ions per O2 molecule. The population of the ratios was widely dispersed, but this was explained as a predictable statistical phenomenon. PMID:3723416

  18. Thyroid hormones increase Na -H exchange activity in renal brush border membranes

    SciTech Connect

    Kinsella, J.; Sacktor, B.

    1985-06-01

    Na -H exchange activity, i.e., amiloride-sensitive Na and H flux, in renal proximal tubule brush border (luminal) membrane vesicles was increased in the hyperthyroid rat and decreased in the hypothyroid rat, relative to the euthyroid animal. A positive correlation was found between Na -H exchange activity and serum concentrations of thyroxine (T4) and triiodothyronine (T3). The thyroid status of the animal did not alter amiloride-insensitive Na uptake. The rate of passive pH gradient dissipation was higher in membrane vesicles from hyperthyroid rats compared to the rate in vesicles from hypothyroid animals, a result which would tend to limit the increase in Na uptake in vesicles from hyperthyroid animals. Na -dependent phosphate uptake was increased in membrane vesicles from hyperthyroid rats; Na -dependent D-glucose and L-proline uptakes were not changed by the thyroid status of the animal. The effect of thyroid hormones in increasing the uptake of Na in the brush border membrane vesicle is consistent with the action of the hormones in enhancing renal Na reabsorption.

  19. Acute inhibition of NCC does not activate distal electrogenic Na+ reabsorption or kaliuresis

    PubMed Central

    Craigie, Eilidh; Homer, Natalie Z. M.; Mullins, John J.; Bailey, Matthew A.

    2014-01-01

    Na+ reabsorption from the distal renal tubule involves electroneutral and electrogenic pathways, with the latter promoting K+ excretion. The relative activities of these two pathways are tightly controlled, participating in the minute-to-minute regulation of systemic K+ balance. The pathways are interdependent: the activity of the NaCl cotransporter (NCC) in the distal convoluted tubule influences the activity of the epithelial Na+ channel (ENaC) downstream. This effect might be mediated by changes in distal Na+ delivery per se or by molecular and structural adaptations in the connecting tubule and collecting ducts. We hypothesized that acute inhibition of NCC activity would cause an immediate increase in Na+ flux through ENaC, with a concomitant increase in renal K+ excretion. We tested this using renal clearance methodology in anesthetized mice, by the administration of hydrochlorothiazide (HCTZ) and/or benzamil (BZM) to exert specific blockade of NCC and ENaC, respectively. Bolus HCTZ elicited a natriuresis that was sustained for up to 110 min; urinary K+ excretion was not affected. Furthermore, the magnitude of the natriuresis was no greater during concomitant BZM administration. This suggests that ENaC-mediated Na+ reabsorption was not normally limited by Na+ delivery, accounting for the absence of thiazide-induced kaliuresis. After dietary Na+ restriction, HCTZ elicited a kaliuresis, but the natiuretic effect of HCTZ was not enhanced by BZM. Our findings support a model in which inhibition of NCC activity does not increase Na+ reabsorption through ENaC solely by increasing distal Na+ delivery but rather by inducing a molecular and structural adaptation in downstream nephron segments. PMID:24402096

  20. Gill Na{sup +}, K{sup +}-ATPase activity in largemouth bass (Micropterus salmoides) inhabiting reservoirs contaminated with mercury

    SciTech Connect

    Brundage, S.; Jagoe, C.H.; Shaw-Allen, P.

    1995-12-31

    Active transport of Na{sup +} and K{sup +} for osmoregulation in fish involves gill Na{sup +}, K{sup +}-ATPase, a membrane-bound enzyme powered by hydrolysis of ATP. Na{sup +}, K{sup +}-ATPase is inhibited by many dissolved metals including Al, Cd, Cu and Hg, resulting in ionoregulatory dysfunction. However, dissolved Hg concentrations are quite low in most aquatic systems, and dietary sources are the most important contributors to Hg burdens in fish. One recent study demonstrated relationships between muscle Hg concentration and gill Na{sup +}, K{sup +}-ATPase in a marine fish, suggesting that Hg accumulated via diet can affect osmoregulation. The authors tested for such a relationship in several age-classes of a freshwater fish (Micropterus salmoides) collected from three reservoirs. Fish from Par Pond and L Lake, on the USDOE Savannah River Site in South Carolina had relatively high Hg content: for Par Pond, muscle and liver ranged from 1.58--12.01 and 1.46--23.22 {micro}g Hg/g dry mass, respectively, and for L Lake muscle and liver ranged from 3.11--5.16 and 1.28--12.59 {micro}g Hg/g dry mass, respectively. Bass from an offsite location, Thurmond Lake, had significantly (P <0.05 by Kruskal-Wallis test) less Hg (muscle and liver range 0.61--2.39 and 0.28--2.32 {micro}g Hg/g dry mass, respectively). In all reservoirs, liver Hg varied more among individuals than muscle Hg. Water chemistry was similar in all reservoirs. Fish from the three reservoirs did not differ significantly in gill ATPase activity, and a correlation between tissue Hg and Na{sup +}, K{sup +}-ATPase activity was not evident.

  1. The active transport of carbohydrates by Escherichia coli.

    PubMed

    Henderson, P J; Kornberg, H L

    1975-01-01

    The active transport of carbohydrates by Escherichia coli is discussed with particular reference to (1) identification of an uptake process as 'active transport', (2) nature and control of transport proteins, and (3) mechanisms of energy transduction. (1) The use of substrate analogues, of mutants blocked in metabolism and of subcellular vesicles in the isolation of the transport process from interference by subsequent metabolic reactions is described. Criteria are outlined for establishing that the solute is taken up against a concentration gradient and that this is energy-dependent. Three types of poisons for energy systems that act primarily on respiration, on ATP formation and as uncoupling ('proton conducting') agents are considered. (2) Methods are described for the selection of mutants impaired in the active uptake of specific carbohydrates. (3) Results show that the uptake of galactose, D-fucose and arabinose by appropriate strains of E. coli is inducible, specific and accompanied by proton uptake. Such and other data support a model based on a chemiosmotic theory of active transport.

  2. Active water transport in unicellular algae: where, why, and how.

    PubMed

    Raven, John A; Doblin, Martina A

    2014-12-01

    The occurrence of active water transport (net transport against a free energy gradient) in photosynthetic organisms has been debated for several decades. Here, active water transport is considered in terms of its roles, where it is found, and the mechanisms by which it could occur. First there is a brief consideration of the possibility of active water transport into plant xylem in the generation of root pressure and the refilling of embolized xylem elements, and from an unsaturated atmosphere into terrestrial organisms living in habitats with limited availability of liquid water. There is then a more detailed consideration of volume and osmotic regulation in wall-less freshwater unicells, and the possibility of generation of buoyancy in marine phytoplankton such as large-celled diatoms. Calculations show that active water transport is a plausible mechanism to assist cells in upwards vertical movements, requires less energy than synthesis of low-density organic solutes, and potentially on a par with excluding certain ions from the vacuole.

  3. Effects of Ouabain on Proliferation of Human Endothelial Cells Correlate with Na+,K+-ATPase Activity and Intracellular Ratio of Na+ and K.

    PubMed

    Tverskoi, A M; Sidorenko, S V; Klimanova, E A; Akimova, O A; Smolyaninova, L V; Lopina, O D; Orlov, S N

    2016-08-01

    Side-by-side with inhibition of the Na+,K+-ATPase ouabain and other cardiotonic steroids (CTS) can affect cell functions by mechanisms other than regulation of the intracellular Na+ and K+ ratio ([Na+]i/[K+]i). Thus, we compared the dose- and time-dependences of the effect of ouabain on intracellular [Na+]i/[K+]i ratio, Na+,K+-ATPase activity, and proliferation of human umbilical vein endothelial cells (HUVEC). Treatment of the cells with 1-3 nM ouabain for 24-72 h decreased the [Na+]i/[K+]i ratio and increased cell proliferation by 20-50%. We discovered that the same ouabain concentrations increased Na+,K+-ATPase activity by 25-30%, as measured by the rate of (86)Rb(+) influx. Higher ouabain concentrations inhibited Na+,K+-ATPase, increased [Na+]i/[K+]i ratio, suppressed cell growth, and caused cell death. When cells were treated with low ouabain concentrations for 48 or 72 h, a negative correlation between [Na+]i/[K+]i ratio and cell growth activation was observed. In cells treated with high ouabain concentrations for 24 h, the [Na+]i/[K+]i ratio correlated positively with proliferation inhibition. These data demonstrate that inhibition of HUVEC proliferation at high CTS concentrations correlates with dissipation of the Na+ and K+ concentration gradients, whereas cell growth stimulation by low CTS doses results from activation of Na+,K+-ATPase and decrease in the [Na+]i/[K+]i ratio. PMID:27677555

  4. Prolonged Intracellular Na+ Dynamics Govern Electrical Activity in Accessory Olfactory Bulb Mitral Cells.

    PubMed

    Zylbertal, Asaph; Kahan, Anat; Ben-Shaul, Yoram; Yarom, Yosef; Wagner, Shlomo

    2015-12-01

    Persistent activity has been reported in many brain areas and is hypothesized to mediate working memory and emotional brain states and to rely upon network or biophysical feedback. Here, we demonstrate a novel mechanism by which persistent neuronal activity can be generated without feedback, relying instead on the slow removal of Na+ from neurons following bursts of activity. We show that mitral cells in the accessory olfactory bulb (AOB), which plays a major role in mammalian social behavior, may respond to a brief sensory stimulation with persistent firing. By combining electrical recordings, Ca2+ and Na+ imaging, and realistic computational modeling, we explored the mechanisms underlying the persistent activity in AOB mitral cells. We found that the exceptionally slow inward current that underlies this activity is governed by prolonged dynamics of intracellular Na+ ([Na+]i), which affects neuronal electrical activity via several pathways. Specifically, elevated dendritic [Na+]i reverses the Na+-Ca2+ exchanger activity, thus modifying the [Ca2+]i set-point. This process, which relies on ubiquitous membrane mechanisms, is likely to play a role in other neuronal types in various brain regions. PMID:26674618

  5. Prolonged Intracellular Na+ Dynamics Govern Electrical Activity in Accessory Olfactory Bulb Mitral Cells.

    PubMed

    Zylbertal, Asaph; Kahan, Anat; Ben-Shaul, Yoram; Yarom, Yosef; Wagner, Shlomo

    2015-12-01

    Persistent activity has been reported in many brain areas and is hypothesized to mediate working memory and emotional brain states and to rely upon network or biophysical feedback. Here, we demonstrate a novel mechanism by which persistent neuronal activity can be generated without feedback, relying instead on the slow removal of Na+ from neurons following bursts of activity. We show that mitral cells in the accessory olfactory bulb (AOB), which plays a major role in mammalian social behavior, may respond to a brief sensory stimulation with persistent firing. By combining electrical recordings, Ca2+ and Na+ imaging, and realistic computational modeling, we explored the mechanisms underlying the persistent activity in AOB mitral cells. We found that the exceptionally slow inward current that underlies this activity is governed by prolonged dynamics of intracellular Na+ ([Na+]i), which affects neuronal electrical activity via several pathways. Specifically, elevated dendritic [Na+]i reverses the Na+-Ca2+ exchanger activity, thus modifying the [Ca2+]i set-point. This process, which relies on ubiquitous membrane mechanisms, is likely to play a role in other neuronal types in various brain regions.

  6. Prolonged Intracellular Na+ Dynamics Govern Electrical Activity in Accessory Olfactory Bulb Mitral Cells

    PubMed Central

    Zylbertal, Asaph; Kahan, Anat; Ben-Shaul, Yoram; Yarom, Yosef; Wagner, Shlomo

    2015-01-01

    Persistent activity has been reported in many brain areas and is hypothesized to mediate working memory and emotional brain states and to rely upon network or biophysical feedback. Here, we demonstrate a novel mechanism by which persistent neuronal activity can be generated without feedback, relying instead on the slow removal of Na+ from neurons following bursts of activity. We show that mitral cells in the accessory olfactory bulb (AOB), which plays a major role in mammalian social behavior, may respond to a brief sensory stimulation with persistent firing. By combining electrical recordings, Ca2+ and Na+ imaging, and realistic computational modeling, we explored the mechanisms underlying the persistent activity in AOB mitral cells. We found that the exceptionally slow inward current that underlies this activity is governed by prolonged dynamics of intracellular Na+ ([Na+]i), which affects neuronal electrical activity via several pathways. Specifically, elevated dendritic [Na+]i reverses the Na+-Ca2+ exchanger activity, thus modifying the [Ca2+]i set-point. This process, which relies on ubiquitous membrane mechanisms, is likely to play a role in other neuronal types in various brain regions. PMID:26674618

  7. Control of spontaneous activation of rat oocytes by regulating plasma membrane Na+/Ca2+ exchanger activities.

    PubMed

    Cui, Wei; Zhang, Jie; Zhang, Chuan-Xin; Jiao, Guang-Zhong; Zhang, Min; Wang, Tian-Yang; Luo, Ming-Jiu; Tan, Jing-He

    2013-06-01

    Inhibiting oocyte spontaneous activation (SA) is essential for successful rat cloning by nuclear transfer (NT). This study tested the hypothesis that activities of the Na(+)/Ca(2+) exchanger (NCX) would decrease with oocyte aging and that SA of rat oocytes could be inhibited if the intraoocyte Ca(2+) rises were prevented by activating the NCX through increasing Na(+) concentrations in the culture medium. Elevating Na(+) levels in culture medium by supplementing NaCl inhibited SA of rat oocytes, while maintaining a constant level of maturation-promoting factor and mitogen-activated protein kinase activities. Experiments using the NCX inhibitor bepridil, the Na(+)/K(+)-ATPase inhibitor ouabain, and an assay for intraoocyte Ca(2+) concentrations showed that extracellular Na(+) inhibited rat oocyte SA by enhancing NCX activity and preventing intracellular Ca(2+) rises. Immunohistochemical quantification indicated that the density of NCX1 decreased significantly in aged oocytes that were prone to SA compared with that in freshly ovulated oocytes whose SA rates were low during in vitro culture. Cumulus cell NT showed that sham enucleation caused marked SA in freshly ovulated rat oocytes and that Na(+) supplementation prevented the manipulation-induced SA and improved the in vitro and in vivo development of rat somatic cell NT embryos. Taken together, the results have confirmed our hypothesis that the NCX is active in rat oocytes and its activity decreases with oocyte aging and that activating the NCX by increasing extracellular Na(+) inhibits SA of rat oocytes and improves the development of rat somatic cell NT embryos. These data are also important for understanding the mechanisms of oocyte aging. PMID:23677981

  8. SORLA/SORL1 functionally interacts with SPAK to control renal activation of Na(+)-K(+)-Cl(-) cotransporter 2.

    PubMed

    Reiche, Juliane; Theilig, Franziska; Rafiqi, Fatema H; Carlo, Anne-Sophie; Militz, Daniel; Mutig, Kerim; Todiras, Mihail; Christensen, Erik Ilsø; Ellison, David H; Bader, Michael; Nykjaer, Anders; Bachmann, Sebastian; Alessi, Dario; Willnow, Thomas E

    2010-06-01

    Proper control of NaCl excretion in the kidney is central to bodily functions, yet many mechanisms that regulate reabsorption of sodium and chloride in the kidney remain incompletely understood. Here, we identify an important role played by the intracellular sorting receptor SORLA (sorting protein-related receptor with A-type repeats) in functional activation of renal ion transporters. We demonstrate that SORLA is expressed in epithelial cells of the thick ascending limb (TAL) of Henle's loop and that lack of receptor expression in this cell type in SORLA-deficient mice results in an inability to properly reabsorb sodium and chloride during osmotic stress. The underlying cellular defect was correlated with an inability of the TAL to phosphorylate Na(+)-K(+)-Cl(-) cotransporter 2 (NKCC2), the major sodium transporter in the distal nephron. SORLA functionally interacts with Ste-20-related proline-alanine-rich kinase (SPAK), an activator of NKCC2, and receptor deficiency is associated with missorting of SPAK. Our data suggest a novel regulatory pathway whereby intracellular trafficking of SPAK by the sorting receptor SORLA is crucial for proper NKCC2 activation and for maintenance of renal ion balance. PMID:20385770

  9. Na(+) doping induced changes in the reduction and charge transport characteristics of Al2O3-stabilized, CuO-based materials for CO2 capture.

    PubMed

    Imtiaz, Q; Abdala, P M; Kierzkowska, A M; van Beek, W; Schweiger, S; Rupp, J L M; Müller, C R

    2016-04-28

    Chemical looping combustion (CLC) and chemical looping with oxygen uncoupling (CLOU) are emerging CO2 capture technologies that could reduce appreciably the costs associated with the capture of CO2. In CLC and CLOU, the oxygen required to combust a hydrocarbon is provided by a solid oxygen carrier. Among the transition metal oxides typically considered for CLC and CLOU, copper oxide (CuO) stands out owing to its high oxygen carrying capacity, exothermic reduction reactions and fast reduction kinetics. However, the low Tammann (sintering) temperature of CuO is a serious drawback. In this context, it has been proposed to support CuO on high Tammann temperature and low cost alumina (Al2O3), thus, reducing the morphological changes occurring over multiple CLC or CLOU redox cycles and stabilizing, in turn, the high activity of CuO. However, in CuO-Al2O3 systems, phase stabilization and avoiding the formation of the CuAl2O4 spinel is key to obtaining a material with a high redox stability and activity. Here, we report a Na(+) doping strategy to phase stabilize Al2O3-supported CuO, yielding in turn an inexpensive material with a high redox stability and CO2 capture efficiency. We also demonstrate that doping CuO-Al2O3 with Na(+) improves the oxygen uncoupling characteristics and coke resistance of the oxygen carriers. Utilizing in situ and ex situ X-ray absorption spectroscopy (XAS), the local structure of Cu and the reduction pathways of CuO were determined as a function of the Na(+) content and cycle number. Finally, using 4-point conductivity measurements, we confirm that doping of Al2O3-supported CuO with Na(+) lowers the activation energy for charge transport explaining conclusively the improved redox characteristics of the new oxygen carriers developed. PMID:27080470

  10. Na(+) doping induced changes in the reduction and charge transport characteristics of Al2O3-stabilized, CuO-based materials for CO2 capture.

    PubMed

    Imtiaz, Q; Abdala, P M; Kierzkowska, A M; van Beek, W; Schweiger, S; Rupp, J L M; Müller, C R

    2016-04-28

    Chemical looping combustion (CLC) and chemical looping with oxygen uncoupling (CLOU) are emerging CO2 capture technologies that could reduce appreciably the costs associated with the capture of CO2. In CLC and CLOU, the oxygen required to combust a hydrocarbon is provided by a solid oxygen carrier. Among the transition metal oxides typically considered for CLC and CLOU, copper oxide (CuO) stands out owing to its high oxygen carrying capacity, exothermic reduction reactions and fast reduction kinetics. However, the low Tammann (sintering) temperature of CuO is a serious drawback. In this context, it has been proposed to support CuO on high Tammann temperature and low cost alumina (Al2O3), thus, reducing the morphological changes occurring over multiple CLC or CLOU redox cycles and stabilizing, in turn, the high activity of CuO. However, in CuO-Al2O3 systems, phase stabilization and avoiding the formation of the CuAl2O4 spinel is key to obtaining a material with a high redox stability and activity. Here, we report a Na(+) doping strategy to phase stabilize Al2O3-supported CuO, yielding in turn an inexpensive material with a high redox stability and CO2 capture efficiency. We also demonstrate that doping CuO-Al2O3 with Na(+) improves the oxygen uncoupling characteristics and coke resistance of the oxygen carriers. Utilizing in situ and ex situ X-ray absorption spectroscopy (XAS), the local structure of Cu and the reduction pathways of CuO were determined as a function of the Na(+) content and cycle number. Finally, using 4-point conductivity measurements, we confirm that doping of Al2O3-supported CuO with Na(+) lowers the activation energy for charge transport explaining conclusively the improved redox characteristics of the new oxygen carriers developed.

  11. Monocarboxylate transporter 1 contributes to growth factor-induced tumor cell migration independent of transporter activity

    PubMed Central

    Gray, Alana L.; Coleman, David T.; Shi, Runhua; Cardelli, James A.

    2016-01-01

    Tumor progression to metastatic disease contributes to the vast majority of incurable cancer. Understanding the processes leading to advanced stage cancer is important for the development of future therapeutic strategies. Here, we establish a connection between tumor cell migration, a prerequisite to metastasis, and monocarboxylate transporter 1 (MCT1). MCT1 transporter activity is known to regulate aspects of tumor progression and, as such, is a clinically relevant target for treating cancer. Knockdown of MCT1 expression caused decreased hepatocyte growth factor (HGF)-induced as well as epidermal growth factor (EGF)-induced tumor cell scattering and wound healing. Western blot analysis suggested that MCT1 knockdown (KD) hinders signaling through the HGF receptor (c-Met) but not the EGF receptor. Exogenous, membrane-permeable MCT1 substrates were not able to rescue motility in MCT1 KD cells, nor was pharmacologic inhibition of MCT1 able to recapitulate decreased cell motility as seen with MCT1 KD cells, indicating transporter activity of MCT1 was dispensable for EGF- and HGF-induced motility. These results indicate MCT1 expression, independent of transporter activity, is required for growth factor-induced tumor cell motility. The findings presented herein suggest a novel function for MCT1 in tumor progression independent of its role as a monocarboxylate transporter. PMID:27127175

  12. APP anterograde transport requires Rab3A GTPase activity for assembly of the transport vesicle

    PubMed Central

    Szodorai, A; Kuan, Y-H; Hunzelmann, S; Engel, U; Sakane, A; Sasaki, T; Takai, Y; Kirsch, J; Müller, U; Beyreuther, K; Brady, S; Morfini, G; Kins, S

    2010-01-01

    The amyloid precursor protein (APP) may be sequentially cleaved by β- and γ-secretases leading to accumulation of Aβ peptides in brains of Alzheimer’s Disease patients. Cleavage by α-secretase prevents Aβ generation. APP is anterogradely transported by conventional kinesin in a distinct transport vesicle, but both the biochemical composition of such a vesicle as well as the specific kinesin-1 motor responsible for transport are poorly defined. Here, we demonstrate by time-lapse analysis and immunoisolations that APP is a cargo of a vesicle containing the kinesin heavy chain isoform kinesin-1C, the small GTPase Rab3A and a specific subset of presynaptic protein components. Moreover, we report that assembly of kinesin-1C and APP in this vesicle type requires Rab3A GTPase activity. Finally, we show cleavage of APP in the analyzed transport vesicles by α-secretase activity, likely mediated by ADAM10. Together, these data indicate for the first time that maturation of transport vesicles, including coupling of conventional kinesin, requires Rab GTPase activity. PMID:19923287

  13. Tuning upconversion through a sensitizer/activator-isolated NaYF4 core/shell structure

    NASA Astrophysics Data System (ADS)

    Ye, Shuai; Chen, Guanying; Shao, Wei; Qu, Junle; Prasad, Paras N.

    2015-02-01

    The ability to tune the emission color of upconversion nanoparticles (UCNPs) will greatly enhance the scope of their applications, ranging from infrared solar cells to volumetric multiplexed bioimaging. Conventional methods to tune upconversion are to vary the type and/or the concentration of doped rare-earth ions in these nanoparticle formulations. Here, we introduce a different approach to vary the emission colors of the frequently used sensitizer/activator pairs of Yb3+/RE3+ (RE = Ho, Er, Tm) via utilization of a sensitizer/activator-isolated NaYF4 core-shell structure. We show that the typical green, yellow, and blue luminescent colors from Yb3+/Ho3+-, Yb3+/Er3+-, and Yb3+/Tm3+-co-doped NaYF4 UCNPs can be converted into the quasi-white, green, and pink blue, when corresponding core-shell structures of NaYF4:Yb3+ @NaYF4:Ho3+, NaYF4:Yb3+ @NaYF4:Er3+ and NaYF4:Yb3+ @NaYF4:Tm3+ are built. Time-resolved spectra indicate that decay lifetimes of the emission bands from the sensitizer/activator-isolated core-shell structure significantly vary from that of the sensitizer/activator-codoped NaYF4 UCNPs, verifying the strain-induced modulation of emission channels in the core-shell structure. These sensitizer-activator-isolated core-shell UCNPs have implications for a range of biophotonic or photonic applications.The ability to tune the emission color of upconversion nanoparticles (UCNPs) will greatly enhance the scope of their applications, ranging from infrared solar cells to volumetric multiplexed bioimaging. Conventional methods to tune upconversion are to vary the type and/or the concentration of doped rare-earth ions in these nanoparticle formulations. Here, we introduce a different approach to vary the emission colors of the frequently used sensitizer/activator pairs of Yb3+/RE3+ (RE = Ho, Er, Tm) via utilization of a sensitizer/activator-isolated NaYF4 core-shell structure. We show that the typical green, yellow, and blue luminescent colors from Yb3+/Ho3+-, Yb3+/Er

  14. Tuning upconversion through a sensitizer/activator-isolated NaYF₄ core/shell structure.

    PubMed

    Ye, Shuai; Chen, Guanying; Shao, Wei; Qu, Junle; Prasad, Paras N

    2015-03-01

    The ability to tune the emission color of upconversion nanoparticles (UCNPs) will greatly enhance the scope of their applications, ranging from infrared solar cells to volumetric multiplexed bioimaging. Conventional methods to tune upconversion are to vary the type and/or the concentration of doped rare-earth ions in these nanoparticle formulations. Here, we introduce a different approach to vary the emission colors of the frequently used sensitizer/activator pairs of Yb(3+)/RE(3+) (RE = Ho, Er, Tm) via utilization of a sensitizer/activator-isolated NaYF4 core-shell structure. We show that the typical green, yellow, and blue luminescent colors from Yb(3+)/Ho(3+)-, Yb(3+)/Er(3+)-, and Yb(3+)/Tm(3+)-co-doped NaYF4 UCNPs can be converted into the quasi-white, green, and pink blue, when corresponding core-shell structures of NaYF4:Yb(3+) @NaYF4:Ho(3+), NaYF4:Yb(3+) @NaYF4:Er(3+) and NaYF4:Yb(3+) @NaYF4:Tm(3+) are built. Time-resolved spectra indicate that decay lifetimes of the emission bands from the sensitizer/activator-isolated core-shell structure significantly vary from that of the sensitizer/activator-codoped NaYF4 UCNPs, verifying the strain-induced modulation of emission channels in the core-shell structure. These sensitizer-activator-isolated core-shell UCNPs have implications for a range of biophotonic or photonic applications.

  15. Ontogeny of Na/H antiporter activity in rabbit renal brush border membrane vesicles.

    PubMed Central

    Beck, J C; Lipkowitz, M S; Abramson, R G

    1991-01-01

    The development of the Na/H antiporter was studied in renal brush border membrane vesicles (BBMV) from fetal and adult rabbits using isotopic and fluorescent techniques. The kinetics of the antiporter studied by 22Na+ uptake revealed that the Vmax was only 25% of that in the adult; however, the Km's for Na+ were not significantly different. These data were confirmed by a fluorescent assay using the pH-sensitive probe, acridine orange: the Vmax was significantly lower in the fetal BBMV. Conductive Na+ movement was estimated from amiloride-insensitive 22Na+ uptake and the rate of alkalinization induced by K+, an ion whose relative conductance was found to be similar to that of Na+. Although relative Na+ conductance was significantly greater in fetal BBMV, the lower Vmax in fetal vesicles could not be ascribed to this factor. Maternal administration of betamethasone (50 micrograms/kg intramuscularly) for 2 d before delivery significantly increased the Vmax of the antiporter to levels observed in the adult; Km was unaffected. Na/K ATPase activity increased fourfold after betamethasone, but the specific activities of four brush border marker enzymes and the kinetics of Na(+)-glucose cotransport were unchanged. These data indicate that there is a developmental increase in brush border Na/H exchange which is the result of an increase in the number and/or the turnover number of the carriers. Further, these data suggest that the postnatal increase in antiporter activity may be related to the surge in glucocorticoid concentration that occurs perinatally. Images PMID:1645751

  16. Regulatory activation is accompanied by movement in the C terminus of the Na-K-Cl cotransporter (NKCC1).

    PubMed

    Monette, Michelle Y; Forbush, Biff

    2012-01-13

    The Na-K-Cl cotransporter (NKCC1) is expressed in most vertebrate cells and is crucial in the regulation of cell volume and intracellular chloride concentration. To study the structure and function of NKCC1, we tagged the transporter with cyan (CFP) and yellow (YFP) fluorescent proteins at two sites within the C terminus and measured fluorescence resonance energy transfer (FRET) in stably expressing human embryonic kidney cell lines. Both singly and doubly tagged NKCC1s were appropriately produced, trafficked to the plasma membrane, and exhibited (86)Rb transport activity. When both fluorescent probes were placed within the same C terminus of an NKCC1 transporter, we recorded an 11% FRET decrease upon activation of the transporter. This result clearly demonstrates movement of the C terminus during the regulatory response to phosphorylation of the N terminus. When we introduced CFP and YFP separately in different NKCC1 constructs and cotransfected these in HEK cells, we observed FRET between dimer pairs, and the fractional FRET decrease upon transporter activation was 46%. Quantitatively, this indicates that the largest FRET-signaled movement is between dimer pairs, an observation supported by further experiments in which the doubly tagged construct was cotransfectionally diluted with untagged NKCC1. Our results demonstrate that regulation of NKCC1 is accompanied by a large movement between two positions in the C termini of a dimeric cotransporter. We suggest that the NKCC1 C terminus is involved in transport regulation and that dimerization may play a key structural role in the regulatory process. It is anticipated that when combined with structural information, our findings will provide a model for understanding the conformational changes that bring about NKCC1 regulation.

  17. Active and passive calcium transport systems in plant cells

    SciTech Connect

    Sze, H.

    1990-01-01

    The ability to change cytoplasmic Ca{sup 2+} levels ((Ca{sup 2+})) by cells has made this cation a key regulator of many biological processes. Cytoplasmic (Ca{sup 2+}) is determined by the coordination of passive Ca{sup 2+} fluxes which increase cytosolic (Ca{sup 2+}) and active Ca{sup 2+} transport systems that lower cytosolic (Ca{sup 2+}). The mechanisms by which plant cells achieve this is poorly understood. We have initially used isolated vesicles from the plasma membrane or organellar membranes to study Ca{sup 2+} transport systems in oat roots (a monocot) and carrot suspension cells (a dicot). The objectives of the proposal were to identify and characterize active (energy-dependent) and passive calcium transport systems that work together to regulate calcium levels in the cytoplasm of plant cells. 10 figs., 2 tabs.

  18. Active transport and cluster formation on 2D networks.

    PubMed

    Greulich, P; Santen, L

    2010-06-01

    We introduce a model for active transport on inhomogeneous networks embedded in a diffusive environment which is motivated by vesicular transport on actin filaments. In the presence of a hard-core interaction, particle clusters are observed that exhibit an algebraically decaying distribution in a large parameter regime, indicating the existence of clusters on all scales. The scale-free behavior can be understood by a mechanism promoting preferential attachment of particles to large clusters. The results are compared with a diffusion-limited aggregation model and active transport on a regular network. For both models we observe aggregation of particles to clusters which are characterized by a finite size scale if the relevant time scales and particle densities are considered. PMID:20556462

  19. Transport of active ellipsoidal particles in ratchet potentials

    SciTech Connect

    Ai, Bao-Quan Wu, Jian-Chun

    2014-03-07

    Rectified transport of active ellipsoidal particles is numerically investigated in a two-dimensional asymmetric potential. The out-of-equilibrium condition for the active particle is an intrinsic property, which can break thermodynamical equilibrium and induce the directed transport. It is found that the perfect sphere particle can facilitate the rectification, while the needlelike particle destroys the directed transport. There exist optimized values of the parameters (the self-propelled velocity, the torque acting on the body) at which the average velocity takes its maximal value. For the ellipsoidal particle with not large asymmetric parameter, the average velocity decreases with increasing the rotational diffusion rate, while for the needlelike particle (very large asymmetric parameter), the average velocity is a peaked function of the rotational diffusion rate. By introducing a finite load, particles with different shapes (or different self-propelled velocities) will move to the opposite directions, which is able to separate particles of different shapes (or different self-propelled velocities)

  20. Active and passive calcium transport systems in plant cells

    SciTech Connect

    Sze, H.

    1991-01-01

    The ability to change cytoplasmic Ca{sup 2+} levels ((Ca{sup 2+})) by cells has made this cation a key regulator of many biological processes. Cytoplasmic (Ca{sup 2+}) is determined by the coordination of passive Ca{sup 2+} fluxes which increase cytosolic (Ca{sup 2+}) and active Ca{sup 2+} transport systems that lower cytosolic (Ca{sup 2+}). The mechanisms by which plant cells achieve this is poorly understood. We have initially used isolated vesicles from the plasma membrane or organellar membranes to study Ca{sup 2+} transport systems in oat roots (a monocot) and carrot suspension cells (a dicot). The objectives of the proposal were to identify and characterize active (energy-dependent) and passive calcium transport systems that work together to regulate calcium levels in the cytoplasm of plant cells.

  1. Effects of internal and external pH on amiloride-blockable Na transport across toad urinary bladder vesicles

    SciTech Connect

    Garty, H.; Civan, E.D.; Civan, M.M.

    1985-01-01

    The authors have examined the effect of internal and external pH on Na+ transport across toad bladder membrane vesicles. Of the total SSNa uptake measured 0.5-2.0 min after introducing tracer, 80 +/- 4% (mean +/- SE, n = 9) is blocked by the diuretic with a KI of 2 X 10(-8) M. Thus, this amiloride-sensitive flux is mediated by the apical sodium-selective channels. Varying the internal (cytosolic) pH over the physiologic range 7.0-8.0 had no effect on sodium transport; this result suggests that variation of intracellular pH in vivo has no direct apical effect on modulating sodium uptake. On the other hand, SSNa was directly and monotonically dependent on external pH. External acidification also reduced the amiloride-sensitive efflux across the walls of the vesicles. This inhibition of 22Na efflux was noted at external Na concentrations of both 0.2 microM and 53 mM. These results are different from those reported with whole toad bladder. A number of possible bases for these differences are considered and discussed. They suggest that the natriferic response induced by mucosal acidification of whole toad urinary bladder appears to operate indirectly through one or more factors, presumably cytosolic, present in whole cells and absent from the vesicles.

  2. Dopamine transporter occupancy by RTI-55, inhibition of dopamine transport and stimulation of locomotor activity

    SciTech Connect

    Gatley, S.J.; Gifford, A.N.; Volkow, N.D.

    1997-05-01

    Cocaine analogs such as RTI-55 (or {beta}CIT) with a higher affinity for the DAT are potentially useful as therapeutic drugs in cocaine abuse as well as for radiopharmaceutical use. Previously we showed that in mice RTI-55 (2 mg/Kg, i/p) reduced H-3 cocaine striatum-to-cerebellum ratios (St/Cb, {lg_bullet}) from 1.6 to 1.2 at 3 h after administration, with recovery by 12 h. In the present study we demonstrate a very similar time-course for transport {triangle} measured in striatal homo within 2 min of sacrifice. The maximum inhibition of uptake at about 1 h corresponded to about 80% of the control uptake rate, similar to the percent reduction in St/Cb. The time-course of the effect of this dose of RTI-55 on locomotor activity ({sq_bullet}) was complex, with a drop in the activity measure at 7 h, after a further injection of RTI-55, but activity remained higher than in saline controls. In spite of this complexity, which may be associated with stereotypies and/or exhaustion, the duration of increased activity is consistent with the duration of transporter blockade. These experiments support the notion that PET/SPECT measures of transporter occupancy accurately reflect transporter inhibition.

  3. Highly porous activated carbons prepared from carbon rich Mongolian anthracite by direct NaOH activation

    NASA Astrophysics Data System (ADS)

    Byamba-Ochir, Narandalai; Shim, Wang Geun; Balathanigaimani, M. S.; Moon, Hee

    2016-08-01

    Highly porous activated carbons (ACs) were prepared from Mongolian raw anthracite (MRA) using sodium hydroxide as an activation agent by varying the mass ratio (powdered MRA/NaOH) as well as the mixing method of chemical agent and powdered MRA. The specific BET surface area and total pore volume of the prepared MRA-based activated carbons (MACs) are in the range of 816-2063 m2/g and of 0.55-1.61 cm3/g, respectively. The pore size distribution of MACs show that most of the pores are in the range from large micropores to small mesopores and their distribution can be controlled by the mass ratio and mixing method of the activating agent. As expected from the intrinsic property of the MRA, the highly graphitic surface morphology of prepared carbons was confirmed from Raman spectra and transmission electron microscopy (TEM) studies. Furthermore the FTIR and XPS results reveal that the preparation of MACs with hydrophobic in nature is highly possible by controlling the mixing conditions of activating agent and powdered MRA. Based on all the results, it is suggested that the prepared MACs could be used for many specific applications, requiring high surface area, optimal pore size distribution, proper surface hydrophobicity as well as strong physical strength.

  4. Na-dependent L-proline transport by eel intestinal brush-border membrane vesicles

    SciTech Connect

    Vilella, S.; Ahearn, G.A.; Cassano, G.; Storelli, C. University of Hawaii at Manoa, Honolulu )

    1988-10-01

    L-({sup 3}H)proline uptake by brush-border membrane vesicles prepared from intestinal mucosa of the European eel, Anguilla anguilla, was stimulated by a transmembrane Na gradient (out > in.) Kinetic analysis of L-proline influx, under short-circuited membrane potential conditions, indicated the presence of an apparent single Na-dependent carrier process and a nonsaturable transfer component with an apparent diffusional permeability (P) of 1.53 {plus minus} 0.35 {mu}l{center dot}mg protein{sup {minus}1}{center dot}min{sup {minus}1}. An imposed transmembrane potential (inside negative) increased apparent L-proline binding affinity (lowered K{sub app}) without appreciably altering maximal amino acid influx (J{sub max}). Hill analysis of L-proline influx over a wide range of external Na concentrations indicated a 1:1 stoichiometry for Na-proline cotransport. Use of amino acid inhibitors of L-proline influx suggested that L-proline transfer may occur by either a classical Na-dependent A System with a wide substrate specificity or by the combination of Na-dependent PHE (phenylalanine preferring) and IMINO (proline, {alpha}-methylaminoisobutyric acid preferring) Systems.

  5. Na+ dependent acid-base transporters in the choroid plexus; insights from slc4 and slc9 gene deletion studies

    PubMed Central

    Christensen, Henriette L.; Nguyen, An T.; Pedersen, Fredrik D.; Damkier, Helle H.

    2013-01-01

    The choroid plexus epithelium (CPE) is located in the ventricular system of the brain, where it secretes the majority of the cerebrospinal fluid (CSF) that fills the ventricular system and surrounds the central nervous system. The CPE is a highly vascularized single layer of cuboidal cells with an unsurpassed transepithelial water and solute transport rate. Several members of the slc4a family of bicarbonate transporters are expressed in the CPE. In the basolateral membrane the electroneutral Na+ dependent Cl−/HCO3− exchanger, NCBE (slc4a10) is expressed. In the luminal membrane, the electrogenic Na+:HCO3− cotransporter, NBCe2 (slc4a5) is expressed. The electroneutral Na+:HCO3− cotransporter, NBCn1 (slc4a7), has been located in both membranes. In addition to the bicarbonate transporters, the Na+/H+ exchanger, NHE1 (slc9a1), is located in the luminal membrane of the CPE. Genetically modified mice targeting slc4a2, slc4a5, slc4a7, slc4a10, and slc9a1 have been generated. Deletion of slc4a5, 7 or 10, or slc9a1 has numerous impacts on CP function and structure in these mice. Removal of the transporters affects brain ventricle size (slc4a5 and slc4a10) and intracellular pH regulation (slc4a7 and slc4a10). In some instances, removal of the proteins from the CPE (slc4a5, 7, and 10) causes changes in abundance and localization of non-target transporters known to be involved in pH regulation and CSF secretion. The focus of this review is to combine the insights gathered from these knockout mice to highlight the impact of slc4 gene deletion on the CSF production and intracellular pH regulation resulting from the deletion of slc4a5, 7 and 10, and slc9a1. Furthermore, the review contains a comparison of the described human mutations of these genes to the findings in the knockout studies. Finally, the future perspective of utilizing these proteins as potential targets for the treatment of CSF disorders will be discussed. PMID:24155723

  6. Dimerization of Plant Defensin NaD1 Enhances Its Antifungal Activity*

    PubMed Central

    Lay, Fung T.; Mills, Grant D.; Poon, Ivan K. H.; Cowieson, Nathan P.; Kirby, Nigel; Baxter, Amy A.; van der Weerden, Nicole L.; Dogovski, Con; Perugini, Matthew A.; Anderson, Marilyn A.; Kvansakul, Marc; Hulett, Mark D.

    2012-01-01

    The plant defensin, NaD1, from the flowers of Nicotiana alata, is a member of a family of cationic peptides that displays growth inhibitory activity against several filamentous fungi, including Fusarium oxysporum. The antifungal activity of NaD1 has been attributed to its ability to permeabilize membranes; however, the molecular basis of this function remains poorly defined. In this study, we have solved the structure of NaD1 from two crystal forms to high resolution (1.4 and 1.58 Å, respectively), both of which contain NaD1 in a dimeric configuration. Using protein cross-linking experiments as well as small angle x-ray scattering analysis and analytical ultracentrifugation, we show that NaD1 forms dimers in solution. The structural studies identified Lys4 as critical in formation of the NaD1 dimer. This was confirmed by site-directed mutagenesis of Lys4 that resulted in substantially reduced dimer formation. Significantly, the reduced ability of the Lys4 mutant to dimerize correlated with diminished antifungal activity. These data demonstrate the importance of dimerization in NaD1 function and have implications for the use of defensins in agribiotechnology applications such as enhancing plant crop protection against fungal pathogens. PMID:22511788

  7. Significance of active ion transport in transalveolar water absorption: a study on isolated rat lung.

    PubMed

    Basset, G; Crone, C; Saumon, G

    1987-03-01

    1. Experiments were performed on isolated rat lungs perfused with Ringer solutions containing red cells. The goal was to clarify the role of active transport of Na+ for the absorption of fluid across the alveolar membrane, and to characterize active and passive pathways. 2. Partially degassed lungs were filled with 5 ml of an isotonic Ringer solution containing 125I-labelled albumin in order to calculate the fluid movement, and 22Na+ or 36Cl- for measurement of ion fluxes. Passive non-electrolyte permeability was determined in all experiments using [3H]mannitol. 3. The average rate of fluid absorption in phosphate-buffered instillates was 134 nl/s (S.E., 18.5; n = 14). With ouabain (10(-4) M) in the perfusate the fluid absorption rate fell to 57 nl/s (S.E., 8.2; n = 18). Amiloride (10(-3)-10(-4) M) in the instillate reduced the absorption to 75 nl/s (S.E., 8.6; n = 16). These results show that fluid absorption depends on transcellular transport of Na+ and that alveolar epithelial cells have a Na+ entry system in the luminal membrane and a Na+-K+ pump in the abluminal membrane. 4. The transcellular ion transport operates in parallel with a paracellular, passive leak that allows mannitol to pass with a permeability surface area product of 1.2 X 10(-4) ml/s, corresponding to a permeability coefficient of 2.4 X 10(-8) cm/s, assuming an alveolar surface area of 5000 cm2. 5. The passive fluxes of Na+ were 9.4 pmol/(cm2s) (S.E., 1.3; n = 25) in the direction from alveoli to perfusate and 8.0 pmol/(cm2s) (S.E., 0.86; n = 6) from perfusate to plasma. The passive fluxes of Cl- in the two directions were not significantly different either. Thus the transalveolar electrical potential difference is too small to affect ion movements measurably. 6. The passive permeability to Na+ was 6.7 X 10(-8) cm/s and to Cl- was 10.2 X 10(-8) cm/s (alveolar surface area assumed to be 5000 cm2). The ratio of the permeabilities is close to the ratio of the diffusion coefficients in free

  8. Sarcolemmal localisation of Na+/H+ exchange and Na+-HCO3- co-transport influences the spatial regulation of intracellular pH in rat ventricular myocytes.

    PubMed

    Garciarena, Carolina D; Ma, Yu-ling; Swietach, Pawel; Huc, Laurence; Vaughan-Jones, Richard D

    2013-05-01

    Membrane acid extrusion by Na(+)/H(+) exchange (NHE1) and Na(+)-HCO3(-) co-transport (NBC) is essential for maintaining a low cytoplasmic [H(+)] (∼60 nm, equivalent to an intracellular pH (pHi) of 7.2). This protects myocardial function from the high chemical reactivity of H(+) ions, universal end-products of metabolism. We show here that, in rat ventricular myocytes, fluorescent antibodies map the NBC isoforms NBCe1 and NBCn1 to lateral sarcolemma, intercalated discs and transverse tubules (t-tubules), while NHE1 is absent from t-tubules. This unexpected difference matches functional measurements of pHi regulation (using AM-loaded SNARF-1, a pH fluorophore). Thus, myocyte detubulation (by transient exposure to 1.5 m formamide) reduces global acid extrusion on NBC by 40%, without affecting NHE1. Similarly, confocal pHi imaging reveals that NBC stimulation induces spatially uniform pHi recovery from acidosis, whereas NHE1 stimulation induces pHi non-uniformity during recovery (of ∼0.1 units, for 2-3 min), particularly at the ends of the cell where intercalated discs are commonly located, and where NHE1 immunostaining is prominent. Mathematical modelling shows that this induction of local pHi microdomains is favoured by low cytoplasmic H(+) mobility and long H(+) diffusion distances, particularly to surface NHE1 transporters mediating high membrane flux. Our results provide the first evidence for a spatial localisation of [H(+)]i regulation in ventricular myocytes, suggesting that, by guarding pHi, NHE1 preferentially protects gap junctional communication at intercalated discs, while NBC locally protects t-tubular excitation-contraction coupling.

  9. Cell kinetics of differentiation of Na/sup +/-dependent hexose transport in a cultured renal epithelial cell line

    SciTech Connect

    Cook, J.S.; Weiss, E.R.

    1985-01-01

    Fully differentiated cells of the renal proximal tubule have the capability of taking up hexoses across their apical borders by transport coupled to the Na/sup +/-electrochemical gradient. This property is also found in postconfluent cultures of the cloned cell line LLC-PK/sub 1/, a morphologically polarized line of renal cells. Postconfluent cells develop the Na/sup +/-dependent capacity to transport hexoses at their apical surface. This function is not observable during the growth phase of the cultures. To analyze the developmental process at the cellular level a method has been derived to separate transporting cells, expressing the differentiated function, from nontransporting cells. The method is based on the swelling of the cells accompanying the uptake of the nonmetabolizable glucose analog alpha methylglucoside. The swollen cells have a lower buoyant density than the undifferentiated cells and may be separated from them on density gradients. Analysis of the distribution of cells on such gradients shows that after the cells reach confluence the undifferentiated subpopulation is recruited onto the differentiation pathway with a rate constant of 0.2 per day, that 5 to 7 days are required for a cell to traverse this pathway to the fully differentiated state, and that once the maximum uptake capacity is achieved the cells do not develop further.

  10. Engineering intracellular active transport systems as in vivo biomolecular tools.

    SciTech Connect

    Bachand, George David; Carroll-Portillo, Amanda

    2006-11-01

    Active transport systems provide essential functions in terms of cell physiology and metastasis. These systems, however, are also co-opted by invading viruses, enabling directed transport of the virus to and from the cell's nucleus (i.e., the site of virus replication). Based on this concept, fundamentally new approaches for interrogating and manipulating the inner workings of living cells may be achievable by co-opting Nature's active transport systems as an in vivo biomolecular tool. The overall goal of this project was to investigate the ability to engineer kinesin-based transport systems for in vivo applications, specifically the collection of effector proteins (e.g., transcriptional regulators) within single cells. In the first part of this project, a chimeric fusion protein consisting of kinesin and a single chain variable fragment (scFv) of an antibody was successfully produced through a recombinant expression system. The kinesin-scFv retained both catalytic and antigenic functionality, enabling selective capture and transport of target antigens. The incorporation of a rabbit IgG-specific scFv into the kinesin established a generalized system for functionalizing kinesin with a wide range of target-selective antibodies raised in rabbits. The second objective was to develop methods of isolating the intact microtubule network from live cells as a platform for evaluating kinesin-based transport within the cytoskeletal architecture of a cell. Successful isolation of intact microtubule networks from two distinct cell types was demonstrated using glutaraldehyde and methanol fixation methods. This work provides a platform for inferring the ability of kinesin-scFv to function in vivo, and may also serve as a three-dimensional scaffold for evaluating and exploiting kinesin-based transport for nanotechnological applications. Overall, the technology developed in this project represents a first-step in engineering active transport system for in vivo applications. Further

  11. Ion activities in the lateral intercellular spaces of gallbladder epithelium transporting at low external osmolarities.

    PubMed

    Zeuthen, T

    1983-01-01

    The ion activities in the lateral spaces of the unilateral preparation of the gallbladder of Rana catesbiana were measured by double-barrelled ion-selective microelectrodes. The bladders were bathed in a saline solution with a low osmolarity (62 mOsm) containing, in mM: 27 Na+, 27 Cl-, 2 K+, 1 Ca++, 4 HCO3-. Working at reduced osmolarities had the advantage of an increased volume transport and of widened intercellular spaces. The reference barrel recorded an electrical potential of +2.7 mV in the spaces; they contained a solution similar to the external solution. The electrodes recorded a Na+ concentration of 27 mM, a K+ concentration of 1.7 mM, a Ca++ concentration of 0.69 mM and a Cl- concentration of 28.5 mM. In the spaces there was a lower resistance between the tip of the electrode and the serosal bath than that recorded with the tip in the lumen, and injection of fluorescent dye (11 A diameter) via the electrodes did not stain the cells. The concentrations in the secretion were similar to those in the spaces. The intracellular compartment had an apparent K+ concentration of 95 mM, and the concentrations of Na+ and Cl- were both about 5 mM. These data indicate that when the gallbladder is bathed with hypotonic solutions and is transporting fluid at approximately three or four times the normal rate, there are no significant osmotic gradients between the lumen and the lateral spaces. It is suggested that transcellular transport of water is implemented by a combination of high osmotic permeabilities across both mucosal and serosal cell membranes and low reflection coefficients (for K+ salts) at the serosal cell membranes. PMID:6606049

  12. Na+ activation of the muscarinic K+ channel by a G-protein-independent mechanism

    PubMed Central

    1996-01-01

    Muscarinic potassium channels (KACh) are composed of two subunits, GIRK1 and GIRK4 (or CIR), and are directly gated by G proteins. We have identified a novel gating mechanism of KACh, independent of G-protein activation. This mechanism involved functional modification of KACh which required hydrolysis of physiological levels of intracellular ATP and was manifested by an increase in the channel mean open time. The ATP-modified channels could in turn be gated by intracellular Na+, starting at approximately 3 mM with an EC50 of approximately 40 mM. The Na(+)-gating of KACh was operative both in native atrial cells and in a heterologous system expressing recombinant channel subunits. Block of the Na+/K+ pump (e.g., by cardiac glycosides) caused significant activation of KACh in atrial cells, with a time course similar to that of Na+ accumulation and in a manner indistinguishable from that of Na(+)-mediated activation of the channel, suggesting that cardiac glycosides activated KACh by increasing intracellular Na+ levels. These results demonstrate for the first time a direct effect of cardiac glycosides on atrial myocytes involving ion channels which are critical in the regulation of cardiac rhythm. PMID:8923264

  13. Magnetic and charge transport properties of the Na-based Os oxide pyrochlore

    SciTech Connect

    Shi, Y.G.; Belik, A.A.; Tachibana, M.; Tanaka, M.; Katsuya, Y.; Kobayashi, K.; Yamaura, K.; Takayama-Muromachi, E.

    2009-04-15

    The Na-based osmium oxide pyrochlore was synthesized for the first time by an ion-exchange method using KOs{sub 2}O{sub 6} as a host. The composition was identified as Na{sub 1.4}Os{sub 2}O{sub 6}.H{sub 2}O by electron probe micro-analysis, thermogravimetric analysis, and structural analysis using synchrotron X-ray diffraction. Na{sub 1.4}Os{sub 2}O{sub 6}.H{sub 2}O crystallizes in a regular pyrochlore structure with some defects (space group: Fd-3m, a=10.16851(1) A). Electrical resistivity, heat capacity, and magnetization measurements clearly showed absence of superconductivity down to 2 K, being in large contrast to what was found for the beta-type pyrochlore superconductor AOs{sub 2}O{sub 6} (A=Cs, Rb, and K). The Sommerfeld coefficient is 22 mJ K{sup -2} mol{sup -1}, being the smallest among AOs{sub 2}O{sub 6}. A magnetic anomaly at {approx}57 K and associated magneto-resistance (+3.7% at 2 K in 70 kOe) were found. - Graphical abstract: Crystal structure of the Na-based Os oxide pyrochlore Na{sub 1.4}Os{sub 2}O{sub 6}.H{sub 2}O.

  14. Thermally activated long range electron transport in living biofilms.

    PubMed

    Yates, Matthew D; Golden, Joel P; Roy, Jared; Strycharz-Glaven, Sarah M; Tsoi, Stanislav; Erickson, Jeffrey S; El-Naggar, Mohamed Y; Calabrese Barton, Scott; Tender, Leonard M

    2015-12-28

    Microbial biofilms grown utilizing electrodes as metabolic electron acceptors or donors are a new class of biomaterials with distinct electronic properties. Here we report that electron transport through living electrode-grown Geobacter sulfurreducens biofilms is a thermally activated process with incoherent redox conductivity. The temperature dependency of this process is consistent with electron-transfer reactions involving hemes of c-type cytochromes known to play important roles in G. sulfurreducens extracellular electron transport. While incoherent redox conductivity is ubiquitous in biological systems at molecular-length scales, it is unprecedented over distances it appears to occur through living G. sulfurreducens biofilms, which can exceed 100 microns in thickness. PMID:26611733

  15. Role of calcium in insulin-stimulated NaC1 transport in medullary thick ascending limb.

    PubMed

    Ito, O; Kondo, Y; Takahashi, N; Omata, K; Abe, K

    1995-08-01

    It has been reported that insulin stimulates directly NaCl transport in the rabbit medullary thick ascending limb (MTAL) [O. Ito, Y. Kondo, N. Takahashi, K. Kudo, Y. Imai, K. Omata, and K. Abe. Am. J. Physiol. 267 (Renal Fluid Electrolyte Physiol. 36): F265-F270, 1994]. In the present investigation, we evaluated the role of Ca2+ in insulin-stimulated NaCl transport in rabbit MTAL by in vitro microperfusion methods. In control experiments, insulin increases transepithelial voltage (Vte) and net lumen-to-bath Cl-flux (JCl). The effects of insulin on Vte and JCl in a Ca2+ -free solution containing ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N' -tetraacetic acid did not differ from those in a Ca2+ -containing control solution. Direct measurements of cytosolic free Ca2+ ([Ca2+]i) with fura 2 fluorescence showed that insulin caused no detectable change in [Ca2+]i in MTAL cells. Chelation of intracellular Ca2+ with the acetoxymethyl ester of 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid inhibited the actions of insulin in Vte and JCl without affecting basal values. We examined further whether calmodulin is also involved in insulin-stimulated NaCl transport in MTAL using two dissimilar inhibitors of calmodulin, trifluoperazine (TFP) and N-(6-aminohexyl)-5-chloro-1-naphthalene-sulfonamide (W-7). TFP and W-7 inhibited the action of insulin in a dose-dependent manner, with maximal inhibition of both agents of > 90%. The half-maximal inhibition by TFP and W-7 was approximately 50 and 100 microM, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

  16. Statistical analysis on Na layer response to geomagnetic activities using Odin/OSIRIS data

    NASA Astrophysics Data System (ADS)

    Tsuda, Takuo T.; Nakamura, Takuji; Ejiri, Mitsumu K.; Nishiyama, Takanori; Hosokawa, Keisuke; Takahashi, Toru; Gumbel, Jörg; Hedin, Jonas

    2016-04-01

    The Na layer is normally distributed from 80 to 110 km, and the height range is corresponding to the ionospheric D and E region. In the polar region, the energetic particles precipitating from the magnetosphere can often penetrate into the E region and even into the D region. Thus, the influence of the energetic particles to the Na layer is one of interests in the aspect of the atmospheric composition change accompanied with the auroral activity. There are several previous studies in this issue. For example, recently, we have reported an initial result on a clear relationship between the electron density increase (due to the energetic particles) and the Na density decrease from observational dataset obtained by Na lidar, EISCAT VHF radar, and optical instruments at Tromsoe, Norway on 24-25 January 2012. However, all of the previous studies had been carried out based on case studies by ground-based lidar observations. In this study, we have performed, for the first time, statistical analysis using Na density data from 2004 to 2009 obtained with the Optical Spectrograph and InfraRed Imager System (OSIRIS) onboard Odin satellite. In the presentation, we will show relationship between the Na density and geomagnetic activities, and its latitudinal variation. Based on these results, the Na layer response to the energetic particles will be discussed.

  17. The SPX domain of the yeast low-affinity phosphate transporter Pho90 regulates transport activity

    PubMed Central

    Hürlimann, Hans Caspar; Pinson, Benoît; Stadler-Waibel, Martha; Zeeman, Samuel C; Freimoser, Florian M

    2009-01-01

    Yeast has two phosphate-uptake systems that complement each other: the high-affinity transporters (Pho84 and Pho89) are active under phosphate starvation, whereas Pho87 and Pho90 are low-affinity transporters that function when phosphate is abundant. Here, we report new regulatory functions of the amino-terminal SPX domain of Pho87 and Pho90. By studying truncated versions of Pho87 and Pho90, we show that the SPX domain limits the phosphate-uptake velocity, suppresses phosphate efflux and affects the regulation of the phosphate signal transduction pathway. Furthermore, split-ubiquitin assays and co-immunoprecipitation suggest that the SPX domain of both Pho90 and Pho87 interacts physically with the regulatory protein Spl2. This work suggests that the SPX domain inhibits low-affinity phosphate transport through a physical interaction with Spl2. PMID:19590579

  18. Fluctuation driven active molecular transport in passive channel proteins

    NASA Astrophysics Data System (ADS)

    Kosztin, Ioan

    2006-03-01

    Living cells interact with their extracellular environment through the cell membrane, which acts as a protective permeability barrier for preserving the internal integrity of the cell. However, cell metabolism requires controlled molecular transport across the cell membrane, a function that is fulfilled by a wide variety of transmembrane proteins, acting as either passive or active transporters. In this talk it is argued that, contrary to the general belief, in active cell membranes passive and spatially asymmetric channel proteins can act as active transporters by consuming energy from nonequilibrium fluctuations fueled by cell metabolism. This assertion is demonstrated in the case of the E. coli aquaglyceroporin GlpF channel protein, whose high resolution crystal structure is manifestly asymmetric. By calculating the glycerol flux through GlpF within the framework of a stochastic model, it is found that, as a result of channel asymmetry, glycerol uptake driven by a concentration gradient is enhanced significantly in the presence of non-equilibrium fluctuations. Furthermore, the enhancement caused by a ratchet-like mechanism is larger for the outward, i.e., from the cytoplasm to the periplasm, flux than for the inward one, suggesting that the same non-equilibrium fluctuations also play an important role in protecting the interior of the cell against poisoning by excess uptake of glycerol. Preliminary data on water and sugar transport through aquaporin and maltoporin channels, respectively, are indicative of the universality of the proposed nonequilibrium-fluctuation-driven active transport mechanism. This work was supported by grants from the Univ. of Missouri Research Board, the Institute for Theoretical Sciences and the Department of Energy (DOE Contract W-7405-ENG-36), and the National Science Foundation (FIBR-0526854).

  19. Measurement and Modeling of Mean Activity Coefficients of NaCl in an Aqueous Mixed Electrolyte Solution Containing Glycine

    NASA Astrophysics Data System (ADS)

    Sheikholeslami, Paniz; Dehghani, M. R.; Safahieh, Tina

    2016-08-01

    An electrochemical cell with two ion-selective electrodes (Na+ glass) and (Cl- solid state) was used to measure the mean ionic activity coefficient of NaCl in an aqueous mixture containing NaCl, glycine, and NaNO3 at 308.15 K. The experiments were conducted at fixed molality of NaNO3 (0.1 m) and various molalities of glycine (0-1 m) and NaCl (up to 0.8 m). The experimental data were modeled using a modified version of the Pitzer equation. Finally the activity coefficient ratio of glycine was determined based on the Maxwell equation.

  20. Preparation and visible light induced photocatalytic activity of C-NaTaO3 and C-NaTaO3-Cl-TiO2 composite.

    PubMed

    Wu, Xiaoyong; Yin, Shu; Dong, Qiang; Sato, Tsugio

    2013-12-21

    A nice visible light responsive C-doped NaTaO3 (C-NaTaO3) particle has been successfully prepared by a facile solvothermal method using water-ethylene glycol mixed solutions as solvent. The results presented that the carbon could be easily incorporated in NaTaO3 from ethylene glycol during a solvothermal reaction, finally leading to excellent visible light absorption. The as-synthesized C-NaTaO3 showed excellent visible light induced photocatalytic activity superior to those of pure NaTaO3 and commercial P25. In addition, in order to further improve the visible light driven photocatalytic performance of C-NaTaO3, a new C-doped NaTaO3-Cl-doped TiO2 (C-NaTaO3-Cl-TiO2) core-shell type of composite was also fabricated. After coupling C-NaTaO3 with Cl-TiO2, the visible light induced NOx gas destruction ability of C-NaTaO3-Cl-TiO2 composite was significantly enhanced as compared to those of sole C-NaTaO3 and Cl-TiO2, probably due to the hindrance of the recombination rate of photogenerated electron-hole pairs. The C-NaTaO3 particle and C-NaTaO3-Cl-TiO2 composite prepared in this work would probably provide a new way to prepare high performance of visible light induced perovskite-type NaTaO3 based photocatalysts.

  1. Charge transport in thin layer Na x CoO2 (x ∼ 0.63) studied by terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Němec, H.; Knížek, K.; Jirák, Z.; Hejtmánek, J.; Soroka, M.; Buršík, J.

    2016-09-01

    Charge transport in Na0.63CoO2 thin film deposited by a spin-coating method was investigated experimentally by time-domain terahertz spectroscopy and theoretically using Monte Carlo calculations of charge response in nano-structured materials. The dominating type of transport mechanism over the entire investigated range of temperatures (20–300 K) is a metallic-like conductivity of charges partly confined in constituting nano-sized grains. Due to the granular character of our thin film, the scattering time at low temperatures is limited by scattering on grain boundaries and the conductivity is strongly suppressed due to capture of a major fraction of charge carriers in deep traps. Nevertheless, our experimental setup and the applied model allowed us to distinguish the parameters related to the grain interior from those influenced by grain boundaries, and to conclude that the metallic type of conductivity is the intrinsic property relevant to single crystal materials.

  2. Charge transport in thin layer Na x CoO2 (x ∼ 0.63) studied by terahertz spectroscopy.

    PubMed

    Němec, H; Knížek, K; Jirák, Z; Hejtmánek, J; Soroka, M; Buršík, J

    2016-09-01

    Charge transport in Na0.63CoO2 thin film deposited by a spin-coating method was investigated experimentally by time-domain terahertz spectroscopy and theoretically using Monte Carlo calculations of charge response in nano-structured materials. The dominating type of transport mechanism over the entire investigated range of temperatures (20-300 K) is a metallic-like conductivity of charges partly confined in constituting nano-sized grains. Due to the granular character of our thin film, the scattering time at low temperatures is limited by scattering on grain boundaries and the conductivity is strongly suppressed due to capture of a major fraction of charge carriers in deep traps. Nevertheless, our experimental setup and the applied model allowed us to distinguish the parameters related to the grain interior from those influenced by grain boundaries, and to conclude that the metallic type of conductivity is the intrinsic property relevant to single crystal materials. PMID:27365361

  3. Substrate-bound outward-open state of the betaine transporter BetP provides insights into Na+ coupling

    NASA Astrophysics Data System (ADS)

    Perez, Camilo; Faust, Belinda; Mehdipour, Ahmad Reza; Francesconi, Kevin A.; Forrest, Lucy R.; Ziegler, Christine

    2014-07-01

    The Na+-coupled betaine symporter BetP shares a highly conserved fold with other sequence unrelated secondary transporters, for example, with neurotransmitter symporters. Recently, we obtained atomic structures of BetP in distinct conformational states, which elucidated parts of its alternating-access mechanism. Here, we report a structure of BetP in a new outward-open state in complex with an anomalous scattering substrate, adding a fundamental piece to an unprecedented set of structural snapshots for a secondary transporter. In combination with molecular dynamics simulations these structural data highlight important features of the sequential formation of the substrate and sodium-binding sites, in which coordinating water molecules play a crucial role. We observe a strictly interdependent binding of betaine and sodium ions during the coupling process. All three sites undergo progressive reshaping and dehydration during the alternating-access cycle, with the most optimal coordination of all substrates found in the closed state.

  4. Theoretical investigation on local structure and transport properties of NaFsbnd AlF3 molten salts under electric field environment

    NASA Astrophysics Data System (ADS)

    Lv, Xiaojun; Xu, Zhenming; Li, Jie; Chen, Jiangan; Liu, Qingsheng

    2016-08-01

    The effect of electric field and molecular ratio CR (NaF/AlF3) on basic structure and transport properties of NaFsbnd AlF3 molten salts were investigated by molecular dynamics simulations with the Buckingham potential model. The [AlF6]3- groups are the dominant specie in NaFsbnd AlF3 molten salts at CR ≥ 2.6, and followed by the [AlF5]2- groups, while CR ≤ 2.4, [AlF5]2- groups are the protagonists up to 40%. In NaFsbnd AlF3 system, with the increase of CR, the proportion of Fb decreases slightly and the percentage of Ff increases dramatically. The Alsbnd F bonds have ionic characters as well as partial covalently characters due to the hybridization of F-2p and Al-3s, 3p orbitals. The order of ion diffusion ability follows as Na+ > F- > Al3+. Adding more NaF can break some F bridges of structure networks and decrease the polymerization degree of NaFsbnd AlF3 molten salts, the viscosity reduces and ionic conductivity increases as a consequence. The calculated results of ionic conductivity are in agreement with the experimental results. Electric field has no significant impact on the local structure characters, while transport properties are not. The change of CR (NaF/AlF3) can significantly affect these characters of both the structure and transport.

  5. Fluctuation-driven directional flow in biochemical cycle: further study of electric activation of Na,K pumps.

    PubMed Central

    Xie, T D; Chen, Y; Marszalek, P; Tsong, T Y

    1997-01-01

    Directional flow of information and energies is characteristic of many types of biochemical reactions, for instance, ion transport, energy coupling during ATP synthesis, and muscle contraction. Can a fluctuating force field, or a noise, induce such a directional flux? Previous work has shown that Na,K-ATPase of human erythrocyte can absorb free energy from an externally applied random-telegraph-noise (RTN) electric field to pump Rb+ up its concentration gradient. However, the RTN field used in these experiments was constant in amplitude and would not mimic fluctuating electric fields of a cell membrane. Here we show that electric fields which fluctuate both in life time and in amplitude, and thus, better mimicking the transmembrane electric fields of a cell, can also induce Rb+ pumping by Na,K-ATPase. A Gaussian-RTN-electric field, or a field with amplitude fluctuating according to the Gaussian distribution, with varied standard deviation (sigma), induced active pumping of Rb+ in human erythrocyte, which was completely inhibited by ouabain. Increased values for sigma led to a nonmonotonic reduction in pumping efficiency. A general formula for calculating the ion transport in a biochemical cycle induced by fluctuating electric field has been derived and applied to a simple four-state electroconformational coupling (ECC) model. It was found that the calculated efficiency in the energy coupling decreased with increasing sigma value, and this effect was relatively small and monotonic, whereas experimental data were more complex: monotonic under certain sets of conditions but nonmonotonic under different sets. The agreement in general features but disagreement in some fine features suggest that there are other properties of the electric activation process for Na,K-ATPase that cannot be adequately described by the simple ECC model, and further refinement of the ECC model is required. PMID:9168026

  6. How Na+ Activates Thrombin – A Review of the Functional and Structural Data

    PubMed Central

    Huntington, James A.

    2009-01-01

    Thrombin is often referred to as the ultimate blood coagulation protease. This is true in both senses: it is the final protease generated in the series of proteolytic events known as the blood coagulation cascade, and it is the effector of clot formation, cleaving over twelve different substrates and interacting with at least six cofactors. Regulation of thrombin activity is thus of great relevance to determining the correct haemostatic balance, with dysregulation leading to bleeding or thrombosis. One of the most enigmatic and controversial regulators of thrombin activity is the monovalent cation Na+. When bound to Na+, thrombin adopts a ‘fast’ conformation which cleaves all procoagulant substrates more rapidly, and when free of Na+, thrombin reverts to a ‘slow’ state which preferentially activates the protein C anticoagulant pathway. Thus, Na+ binding allosterically modulates the activity of thrombin and helps determine the haemostatic balance. Over the last 30 years there has been a great deal of research into the structural basis of thrombin allostery. Biochemical and mutagenesis studies established which regions and residues are involved in the slow→fast conformational change, and recently several crystal structures of the putative slow form have been solved. In this article I review the biochemical and crystallographic data to see if we are any closer to understanding the conformational basis of the Na+ activation of thrombin. PMID:18979627

  7. Gamma ray spectrometer experiment, NaI(Tl) detector crystal activation. [onboard Apollo 17 command module

    NASA Technical Reports Server (NTRS)

    Trombka, J. I.; Schmadebeck, R. L.; Bielefeld, M.; Okelley, G. D.; Eldridge, J. S.; Northcutt, K. J.; Metzger, A. E.; Schonfeld, E.; Peterson, L. E.; Arnold, J. R.

    1973-01-01

    Preliminary results are presented of data on the extent of the cosmic ray-induced activity obtained by a sodium iodide thallium-activated crystal flown onboard the Apollo 17 command module. Qualitative identification is reported for the following: Na-24, I-123, I-124, I-125, I-126, and Xe-127.

  8. Methylphenidate treatment increases Na(+), K (+)-ATPase activity in the cerebrum of young and adult rats.

    PubMed

    Scherer, Emilene B S; Matté, Cristiane; Ferreira, Andréa G K; Gomes, Karin M; Comim, Clarissa M; Mattos, Cristiane; Quevedo, João; Streck, Emilio L; Wyse, Angela T S

    2009-12-01

    Methylphenidate is a central nervous system stimulant used for the treatment of attention-deficit hyperactivity disorder. Na(+), K(+)-ATPase is a membrane-bound enzyme necessary to maintain neuronal excitability. Considering that methylphenidate effects on central nervous system metabolism are poorly known and that Na(+), K(+)-ATPase is essential to normal brain function, the purpose of this study was to evaluate the effect of this drug on Na(+), K(+)-ATPase activity in the cerebrum of young and adult rats. For acute administration, a single injection of methylphenidate (1.0, 2.0, or 10.0 mg/Kg) or saline was given to rats on postnatal day 25 or postnatal day 60, in the young and adult groups, respectively. For chronic administration, methylphenidate (1.0, 2.0, or 10.0 mg/Kg) or saline injections were given to young rats starting at postnatal day 25 once daily for 28 days. In adult rats, the same regimen was performed starting at postnatal day 60. Our results showed that acute methylphenidate administration increased Na(+), K(+)-ATPase activity in hippocampus, prefrontal cortex, and striatum of young and adult rats. In young rats, chronic administration of methylphenidate also enhanced Na(+), K(+)-ATPase activity in hippocampus and prefrontal cortex, but not in striatum. When tested in adult rats, Na(+), K(+)-ATPase activity was increased in all cerebral structures studied. The present findings suggest that increased Na(+), K(+)-ATPase activity may be associated with neuronal excitability caused by methylphenidate.

  9. Transendothelial albumin flux: evidence against active transport of albumin

    SciTech Connect

    Siflinger-Birnboim, A.; Del Vecchio, P.J.; Cooper, J.A.; Malik, A.B.

    1986-03-01

    The authors studied whether albumin is actively transported across cultured pulmonary endothelium by comparing the transendothelial flux of /sup 125/I-albumin from the luminal-to-abluminal side to the flux from the abluminal-to-luminal side. Bovine pulmonary artery endothelial cells were grown to confluence on gelatinized polycarbonated filters separating abluminal from luminal compartments. Each compartment had an albumin concentration of 1 g/100 ml to equalize oncotic pressure gradients. The effect of hydrostatic pressure was eliminated by maintaining an equal level of fluid in both compartments. The transendothelial flux of albumin across the monolayer was measured by placing /sup 125/I-albumin tracer either on the luminal or the abluminal side. Equal fluxes of /sup 125/I-albumin from luminal-to-abluminal side and from abluminal-to-luminal side were observed. The results indicate that the pulmonary endothelium behaves symmetrically for albumin, indicating the absence of active transport of albumin.

  10. Selective decrease of Na+/k+ -ATPase activity in the brain of hypothyroid rats.

    PubMed

    Pacheco-Rosado, Jorge; Arias-Citalán, G; Ortiz-Butrón, R; Rodríquez-Páez, L

    2005-01-01

    The present work was performed in order to know if mild hypothyroidism in rats modifies the activity of the Na+/K+ -ATPase in different regions of the brain. Male Wistar rats (300-350 g) were randomly divided into three groups: (1) control group (n=8) drank tap water. (2) hypothyroid group (n=8) treated with 60 mg/kg of methimazole in drinking water; and (3) replaced group (n=8) treated with 60 mg/kg of methimazole plus 35 microg/kg of thyroid hormone (T3) in drinking water. After four weeks of treatment, the rats of all groups were sacrificed by decapitation. The cortex, amygdala, hippocampus and cerebellum were dissected and frozen at -70 degrees C until assay. For enzymatic assay, the tissues were homogenized. The Na+/K+ -ATPase activity was determined by quantifying inorganic phosphate after the samples were incubated with ATP in the presence and absence of 1 mM ouabain. The Na+/K+ -ATPase activity is expressed as pmoles Pi/hr/mg protein. The results showed that the Na+/K+ -ATPase activity in the cortex, amygdala and hippocampus, but not in cerebellum, was lower in hypothyroid group than in control group (p<0.05). The co-administration of methimazole and T3 avoided the decrease of Na+/K+ -ATPase activity, except in amygdala. According to the results obtained we concluded that methimazole treatment decreased the Na+/K+- ATPase activity in the brain's regions which are related to seizures onset. That decrement in enzyme activity was avoided with the coadministration of thyroid hormone.

  11. Na,K-ATPase α2 activity in mammalian skeletal muscle T-tubules is acutely stimulated by extracellular K+

    PubMed Central

    Hakimjavadi, Hesamedin; Lingrel, Jerry B.

    2015-01-01

    The Na,K-ATPase α2 isoform is the predominant Na,K-ATPase in adult skeletal muscle and the sole Na,K-ATPase in the transverse tubules (T-tubules). In quiescent muscles, the α2 isozyme operates substantially below its maximal transport capacity. Unlike the α1 isoform, the α2 isoform is not required for maintaining resting ion gradients or the resting membrane potential, canonical roles of the Na,K-ATPase in most other cells. However, α2 activity is stimulated immediately upon the start of contraction and, in working muscles, its contribution is crucial to maintaining excitation and resisting fatigue. Here, we show that α2 activity is determined in part by the K+ concentration in the T-tubules, through its K+ substrate affinity. Apparent K+ affinity was determined from measurements of the K1/2 for K+ activation of pump current in intact, voltage-clamped mouse flexor digitorum brevis muscle fibers. Pump current generated by the α2 Na,K-ATPase, Ip, was identified as the outward current activated by K+ and inhibited by micromolar ouabain. Ip was outward at all potentials studied (−90 to −30 mV) and increased with depolarization in the subthreshold range, −90 to −50 mV. The Q10 was 2.1 over the range of 22–37°C. The K1/2,K of Ip was 4.3 ± 0.3 mM at −90 mV and was relatively voltage independent. This K+ affinity is lower than that reported for other cell types but closely matches the dynamic range of extracellular K+ concentrations in the T-tubules. During muscle contraction, T-tubule luminal K+ increases in proportion to the frequency and duration of action potential firing. This K1/2,K predicts a low fractional occupancy of K+ substrate sites at the resting extracellular K+ concentration, with occupancy increasing in proportion to the frequency of membrane excitation. The stimulation of preexisting pumps by greater K+ site occupancy thus provides a rapid mechanism for increasing α2 activity in working muscles. PMID:26371210

  12. Thermoelectric transport properties of pristine and Na-doped SnSe(1-x)Te(x) polycrystals.

    PubMed

    Wei, Tian-Ran; Wu, Chao-Feng; Zhang, Xiaozhi; Tan, Qing; Sun, Li; Pan, Yu; Li, Jing-Feng

    2015-11-28

    SnSe, a "simple" and "old" binary compound composed of earth-abundant elements, has been reported to exhibit a high thermoelectric performance in single crystals, which stimulated recent interest in its polycrystalline counterparts. This work investigated the electrical and thermal transport properties of pristine and Na-doped SnSe1-xTex polycrystals prepared by mechanical alloying and spark plasma sintering. It is revealed that SnSe1-xTex solid solutions are formed when x ranges from 0 to 0.2. An energy barrier scattering mechanism is suitable for understanding the electrical conducting behaviour observed in the present SnSe polycrystalline materials, which may be associated with abundant defects at grain boundaries. The thermal conductivity was greatly reduced upon Te substitution due to alloy scattering of phonons as well explained by the Debye model. Due to the increased carrier concentration by Na-doping, thermoelectric figure of merit (ZT) was enhanced in the whole temperature range with a maximum value of 0.72 obtained at a relatively low temperature (773 K) for Sn0.99Na0.01Se0.84Te0.16. PMID:26496971

  13. The Asymmetric Active Coupler: Stable Nonlinear Supermodes and Directed Transport

    PubMed Central

    Kominis, Yannis; Bountis, Tassos; Flach, Sergej

    2016-01-01

    We consider the asymmetric active coupler (AAC) consisting of two coupled dissimilar waveguides with gain and loss. We show that under generic conditions, not restricted by parity-time symmetry, there exist finite-power, constant-intensity nonlinear supermodes (NS), resulting from the balance between gain, loss, nonlinearity, coupling and dissimilarity. The system is shown to possess non-reciprocal dynamics enabling directed power transport functionality. PMID:27640818

  14. The Asymmetric Active Coupler: Stable Nonlinear Supermodes and Directed Transport.

    PubMed

    Kominis, Yannis; Bountis, Tassos; Flach, Sergej

    2016-01-01

    We consider the asymmetric active coupler (AAC) consisting of two coupled dissimilar waveguides with gain and loss. We show that under generic conditions, not restricted by parity-time symmetry, there exist finite-power, constant-intensity nonlinear supermodes (NS), resulting from the balance between gain, loss, nonlinearity, coupling and dissimilarity. The system is shown to possess non-reciprocal dynamics enabling directed power transport functionality. PMID:27640818

  15. The Asymmetric Active Coupler: Stable Nonlinear Supermodes and Directed Transport

    NASA Astrophysics Data System (ADS)

    Kominis, Yannis; Bountis, Tassos; Flach, Sergej

    2016-09-01

    We consider the asymmetric active coupler (AAC) consisting of two coupled dissimilar waveguides with gain and loss. We show that under generic conditions, not restricted by parity-time symmetry, there exist finite-power, constant-intensity nonlinear supermodes (NS), resulting from the balance between gain, loss, nonlinearity, coupling and dissimilarity. The system is shown to possess non-reciprocal dynamics enabling directed power transport functionality.

  16. Transport property and Raman spectroscopic studies of the polymer electrolyte system P(EO){sub n}-NaTFSI

    SciTech Connect

    Ferry, A.; Doeff, M.M.; De Jonghe, L.C.

    1998-05-01

    Concentration dependences of a complete set of ionic transport properties are reported for the binary solid polymeric ion conductor poly(ethylene-oxide) [P(EO)], complexed with NaTFSI, [TFSI = (bis)trifluoromethanesulfonate imide, (CF{sub 3}SO{sub 2}){sub 2}N]. Measured transport properties include the ionic conductivity ({sigma}), the differential salt diffusion coefficient (D{sub s}), and the cationic transference number (t{sub +}{sup 0}). To measure t{sub +}{sup 0}, a recently developed technique based on concentrated solution theory is used. Under this framework no assumptions need to be made concerning ideality of the electrolytic solution. The authors find that for the P(EO){sub n}-NaTFSI complexes the ionic conductivities, and differential salt diffusion coefficients are much higher than those of the previously reported P(EO){sub n}-NaCF{sub 3}SO{sub 3} system. D{sub s} also varies less with complex composition in concentrated solutions. Interestingly, the cationic transference numbers are found to be negative over a wide concentration range, i.e., t{sub +}{sup 0} decreases with increasing salt concentration and reaches a low of {minus}1.15 {+-} 0.25 at a composition corresponding to an ether-oxygen to sodium-ion ratio of 7:1. This implies that the cationic current is mainly carried by complexed ions. Complementary Raman spectroscopic studies directly probing cation-anion and cation-polymer molecular interactions show that extensive interionic interactions occur in this system.

  17. Effects of NKCC2 isoform regulation on NaCl transport in thick ascending limb and macula densa: a modeling study.

    PubMed

    Edwards, Aurélie; Castrop, Hayo; Laghmani, Kamel; Vallon, Volker; Layton, Anita T

    2014-07-15

    This study aims to understand the extent to which modulation of the Na(+)-K(+)-2Cl(-) cotransporter NKCC2 differential splicing affects NaCl delivery to the macula densa. NaCl absorption by the thick ascending limb and macula densa cells is mediated by apical NKCC2. A recent study has indicated that differential splicing of NKCC2 is modulated by dietary salt (Schieβl IM, Rosenauer A, Kattler V, Minuth WW, Oppermann M, Castrop H. Am J Physiol Renal Physiol 305: F1139-F1148, 2013). Given the markedly different ion affinities of its splice variants, modulation of NKCC2 differential splicing is believed to impact NaCl reabsorption. To assess the validity of that hypothesis, we have developed a mathematical model of macula densa cell transport and incorporated that cell model into a previously applied model of the thick ascending limb (Weinstein AM, Krahn TA. Am J Physiol Renal Physiol 298: F525-F542, 2010). The macula densa model predicts a 27.4- and 13.1-mV depolarization of the basolateral membrane [as a surrogate for activation of tubuloglomerular feedback (TGF)] when luminal NaCl concentration is increased from 25 to 145 mM or luminal K(+) concentration is increased from 1.5 to 3.5 mM, respectively, consistent with experimental measurements. Simulations indicate that with luminal solute concentrations consistent with in vivo conditions near the macula densa, NKCC2 operates near its equilibrium state. Results also suggest that modulation of NKCC2 differential splicing by low salt, which induces a shift from NKCC2-A to NKCC2-B primarily in the cortical thick ascending limb and macula densa cells, significantly enhances salt reabsorption in the thick limb and reduces Na(+) and Cl(-) delivery to the macula densa by 3.7 and 12.5%, respectively. Simulation results also predict that the NKCC2 isoform shift hyperpolarizes the macula densa basolateral cell membrane, which, taken in isolation, may inhibit the release of the TGF signal. However, excessive early distal salt

  18. The Na+-motive terminal oxidase activity in an alkalo- and halo-tolerant Bacillus.

    PubMed

    Semeykina, A L; Skulachev, V P; Verkhovskaya, M L; Bulygina, E S; Chumakov, K M

    1989-08-15

    An alkalo- and halo-tolerant aerobic microorganism has been isolated which, according to microbiological analysis data and the ribosomal 5S RNA sequence, is a Bacillus similar, but not identical, to B. licheniformis and B. subtilis. The microorganism, called Bacillus FTU, proved to be resistant to the protonophorous uncoupler carbonylcyanide m-chlorophenylhydrazone (CCCP). The fast growth of Bacillus FTU in the presence of CCCP was shown to require a high Na+ concentration in the medium. A procedure was developed to exhaust endogenous respiratory substrates in Bacillus FTU cells so that fast oxygen consumption by the cells was observed only when an exogenous respiratory substrate was added. The exhausted cells were found to oxidize ascorbate in the presence of N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) in a cyanide-sensitive fashion. The ascorbate oxidation was coupled to the uphill Na+ extrusion which was stimulated by CCCP and a penetrating weak base, diethylamine, as well as by valinomycin with or without diethylamine. Operation of the Bacillus FTU terminal oxidase resulted in the generation of a delta psi which, in the Na+ medium, was slightly decreased by CCCP and strongly decreased by CCCP + diethylamine. In the K+ medium, CCCP discharged delta psi even without diethylamine. Ascorbate oxidation was competent in ATP synthesis which was resistant to CCCP in the Na+ medium and sensitive to CCCP in the K+ medium as if Na+- and H+-coupled oxidative phosphorylations were operative in the Na+ and K+ media, respectively. Inside-out subcellular vesicles of Bacillus FTU were found to be competent in the Na+ uptake supported by oxidation of ascorbate + TMPD or diaminodurene. CCCP or valinomycin + K+ increased the Na+ uptake very strongly. The process was completely inhibited by cyanide or monensin, the former, but not the latter, being inhibitory for respiration. The data obtained indicate that in Bacillus FTU there is not only H+-motive but also Na

  19. Na+,Cl- cotransport in Ehrlich ascites tumor cells activated during volume regulation (regulatory volume increase).

    PubMed

    Hoffmann, E K; Sjøholm, C; Simonsen, L O

    1983-01-01

    Ehrlich ascites cells were preincubated in hypotonic medium with subsequent restoration of tonicity. After the initial osmotic shrinkage the cells recovered their volume within 5 min with an associated KCl uptake. The volume recovery was inhibited when NO-3 was substituted for Cl-, and when Na+ was replaced by K+, or by choline (at 5 mM external K+). The volume recovery was strongly inhibited by furosemide and bumetanide, but essentially unaffected by DIDS. The net uptake of Cl- was much larger than the value predicted from the conductive Cl- permeability. The undirectional 36Cl flux, which was insensitive to bumetanide under steady-state conditions, was substantially increased during regulatory volume increase, and showed a large bumetanide-sensitive component. During volume recovery the Cl- flux ratio (influx/efflux) for the bumetanide-sensitive component was estimated at 1.85, compatible with a coupled uptake of Na+ and Cl-, or with an uptake via a K+,Na+,2Cl- cotransport system. The latter possibility is unlikely, however, because a net uptake of KCl was found even at low external K+, and because no K+ uptake was found in ouabain-poisoned cells. In the presence of ouabain a bumetanide-sensitive uptake during volume recovery of Na+ and Cl- in nearly equimolar amounts was demonstrated. It is proposed that the primary process during the regulatory volume increase is an activation of an otherwise quiescent, bumetanide-sensitive Na+,Cl- cotransport system with subsequent replacement of Na+ by K+ via the Na+/K+ pump, stimulated by the Na+ influx through the Na+,Cl- cotransport system. PMID:6100866

  20. Proteins which mediate the nuclear entry of goat uterine non activated estrogen receptor (naER) following naER internalization from the plasma membrane.

    PubMed

    Sreeja, S; Thampan, Raghava Varman

    2004-04-01

    The nuclear transport of the internalised naER is influenced by a 58 kDa protein, p58, that appears to recognize the nuclear localization signals on the naER. At the nuclear pore complex the naER-p58 complex binds to a 62 kDa protein, p62; p58 recognizes p62 in this interaction. It is further observed that p62 gets 'docked' at a 66 kDa nuclear pore complex protein, npcp66. The nuclear entry of naER is an ATP-dependent process. An ATP-dependent biphasic nuclear entry of naER, has been observed. It is possible that the docking of p58-naER complex at the nuclear pore complex and the eventual nuclear entry of naER following its dissociation from the p58 are influenced by two different ranges in the concentration of ATP. In this process, it appears that, the nuclear entry requires an additional quantum of energy, provided by the hydrolysed ATP, in contrast to the energy requirement associated with, the nuclear 'docking' event. PMID:15124917

  1. N-Glycosylation is required for Na{sup +}-dependent vitamin C transporter functionality

    SciTech Connect

    Subramanian, Veedamali S. Marchant, Jonathan S.; Reidling, Jack C.; Said, Hamid M.

    2008-09-12

    The human sodium-dependent vitamin C transporters (hSVCT1 and hSVCT2) mediate cellular uptake of ascorbic acid. Both these transporters contain potential sites for N-glycosylation in their extracellular domains (Asn-138, Asn-144 [hSVCT1]; Asn-188, Asn-196 [hSVCT2]), however the role of N-glycosylation in transporter function is unexplored. On the basis of the result that tunicamycin decreased {sup 14}C-ascorbic acid uptake in HepG2 cells, we systematically ablated all consensus N-glycosylation sites in hSVCT1 and hSVCT2 to resolve any effects on ascorbic acid uptake, transporter expression and targeting. We show that removal of individual N-glycosylation sites significantly impairs protein expression and consequently ascorbic acid uptake for hSVCT1 mutants (N138Q is retained intracellularly) and for hSVCT2 mutants (all of which reach the cell surface). N-Glycosylation is therefore essential for vitamin C transporter functionality.

  2. Ionic regulation of Na absorption in proximal colon: cation inhibition of electroneutral Na absorption

    SciTech Connect

    Sellin, J.H.; De Soignie, R.

    1987-01-01

    Active Na absorption (J/sub net//sup NA/) in rabbit proximal colon in vitro is paradoxically stimulated as (Na) in the bathing media is lowered with constant osmolarity. J/sub m..-->..s//sup Na/ increases almost linearly from 0 to 50 mM (Na)/sub 0/ but then plateaus and actually decreases from 50 to 140 mM (Na)/sub 0/, consistent with inhibition of an active transport process. Both lithium and Na are equally effective inhibitors of J/sub net//sup Na/, whereas choline and mannitol do not block the high rate of J/sub net//sup Na/ observed in decreased (Na)/sub 0/. Either gluconate or proprionate replacement of Cl inhibits J/sub net//sup Na/. J/sub net//sup Na/ at lowered (Na)/sub 0/ is electrically silent and is accompanied by increased Cl absorption; it is inhibited by 10/sup -3/ M amiloride and 10/sup -3/ theophylline but not by 10/sup -4/ M bumetanide. Epinephrine is equally effective at stimulating Na absorption at 50 and 140 mM (Na). Na gradient experiments are consistent with a predominantly serosal effect of the decreased (Na)/sub 0/. These results suggest that 1) Na absorption in rabbit proximal colon in vitro is stimulated by decreased (Na); 2) the effect is cation specific, both Na and Li blocking the stimulatory effect; 3) the transport is mediated by Na-H exchange and is Cl dependent but 4) is under different regulatory mechanisms than the epinephrine-sensitive Na-Cl cotransport previously described in proximal colon. Under the appropriate conditions, proximal colon absorbs Na extremely efficiently. Na-H exchange in this epithelium is cation inhibitable, either directly or by a secondary regulatory process.

  3. Cadmium induced inhibition of Na sup + /K sup + ATPase activity in tissues of crab Scylla serrata (Forskal)

    SciTech Connect

    Dhavale, D.M. ); Masurekar, V.B. ); Giridhar, B.A. )

    1988-06-01

    Heavy metals discharged from industries these days are a major source of pollution which has become threat to all forms of life. A measure of metabolism may be a most sensitive parameter since it integrates many factors such as enzyme activity, biochemical contents and physiological response. The ability to accurately characterize enzymes with respect to their distribution and kinetics makes them attractive indices of stress. The concept of Na{sup +}/K{sup +}-ATPase being intimately involved in active transport of ions across biological membranes has gained wide acceptance in recent years. Interference with osmoregulation may restrict the animal's ability to adapt to salinity changes. Several studies have shown that crustacenas are highly sensitive to metal pollutants, particularly when acclimated to low salinities. The present study was initiated to compare the characteristics of Na{sup +}/K{sup +}-ATPase activity in hepatopancreas and gills of crabs Scylla serrata (Forskal) exposed to acute and sublethal concentrations of cadmium chloride for defined periods with those from undosed animals.

  4. Differences in associations between active transportation and built environmental exposures when expressed using different components of individual activity spaces.

    PubMed

    van Heeswijck, Torbjorn; Paquet, Catherine; Kestens, Yan; Thierry, Benoit; Morency, Catherine; Daniel, Mark

    2015-05-01

    This study assessed relationships between built environmental exposures measured within components of individual activity spaces (i.e., travel origins, destinations and paths in-between), and use of active transportation in a metropolitan setting. Individuals (n=37,165) were categorised as using active or sedentary transportation based on travel survey data. Generalised Estimating Equations analysis was used to test relationships with active transportation. Strength and significance of relationships between exposures and active transportation varied for different components of the activity space. Associations were strongest when including travel paths in expression of the built environment. Land use mix and greenness were negatively related to active transportation.

  5. Examining Changes in Radioxenon Isotope Activity Ratios during Subsurface Transport

    NASA Astrophysics Data System (ADS)

    Annewandter, Robert

    2014-05-01

    The Non-Proliferation Experiment (NPE) has demonstrated and modelled the usefulness of barometric pumping induced gas transport and subsequent soil gas sampling during On-Site inspections. Generally, gas transport has been widely studied with different numerical codes. However, gas transport of radioxenons and radioiodines in the post-detonation regime and their possible fractionation is still neglected in the open peer-reviewed literature. Atmospheric concentrations of the radioxenons Xe-135, Xe-133m, Xe-133 and Xe-131m can be used to discriminate between civilian releases (nuclear power plants or medical isotope facilities), and nuclear explosion sources. It is based on the multiple isotopic activity ratio method. Yet it is not clear whether subsurface migration of the radionuclides, with eventual release into the atmosphere, can affect the activity ratios due to fractionation. Fractionation can be caused by different mass diffusivities due to mass differences between the radionuclides. Cyclical changes in atmospheric pressure can drive subsurface gas transport. This barometric pumping phenomenon causes an oscillatoric flow in upward trending fractures or highly conductive faults which, combined with diffusion into the porous matrix, leads to a net transport of gaseous components - a so-called ratcheting effect. We use a general purpose reservoir simulator (Complex System Modelling Platform, CSMP++) which is recognized by the oil industry as leading in Discrete Fracture-Matrix (DFM) simulations. It has been applied in a range of fields such as deep geothermal systems, three-phase black oil simulations, fracture propagation in fractured, porous media, and Navier-Stokes pore-scale modelling among others. It is specifically designed to account for structurally complex geologic situation of fractured, porous media. Parabolic differential equations are solved by a continuous Galerkin finite-element method, hyperbolic differential equations by a complementary finite

  6. "JCE" Classroom Activity Connections: NaCl or CaCl[subscript 2], Smart Polymer Gel Tells More

    ERIC Educational Resources Information Center

    Chen, Yueh-Huey; Lin, Jia-Ying; Wang, Yu-Chen; Yaung, Jing-Fun

    2010-01-01

    This classroom activity connection demonstrates the differences between the effects of NaCl (a salt of monovalent metal ions) and CaCl[subscript 2] (a salt of polyvalent metal ions) on swollen superabsorbent polymer gels. Being ionic compounds, NaCl and CaCl[subscript 2] both collapse the swollen polymer gels. The gel contracted by NaCl reswells…

  7. Ride On! Mini-Units and Learning Activities on Public Transportation for Grades 6 through 9.

    ERIC Educational Resources Information Center

    Finn, Peter; And Others

    One of a series of eleven curriculum manuals which cover the four transportation topics of public transportation, transportation and the environment, transportation safety, and bicycles for elementary, secondary, and adult levels, this manual covers the public transportation topic for grades 6-9. It contains forty-two learning activities grouped…

  8. Ride On! Mini-Units and Learning Activities on Public Transportation for Grades 9 through 12.

    ERIC Educational Resources Information Center

    Finn, Peter; And Others

    One of a series of eleven curriculum manuals which cover the four transportation topics of public transportation, transportation and the environment, transportation safety, and bicycles for elementary, secondary, and adult levels, this manual covers the public transportation topic for grades 9-12. It contains forty-nine learning activities grouped…

  9. Engineering Protein Allostery: 1.05 Å Resolution Structure and Enzymatic Properties of a Na[superscript +]-activated Trypsin

    SciTech Connect

    Page, Michael J.; Carrell, Christopher J.; Di Cera, Enrico

    2008-05-28

    Some trypsin-like proteases are endowed with Na{sup +}-dependent allosteric enhancement of catalytic activity, but this important mechanism has been difficult to engineer in other members of the family. Replacement of 19 amino acids in Streptomyces griseus trypsin targeting the active site and the Na{sup +}-binding site were found necessary to generate efficient Na{sup +} activation. Remarkably, this property was linked to the acquisition of a new substrate selectivity profile similar to that of factor Xa, a Na{sup -} activated protease involved in blood coagulation. The X-ray crystal structure of the mutant trypsin solved to 1.05 {angstrom} resolution defines the engineered Na{sup +} site and active site loops in unprecedented detail. The results demonstrate that trypsin can be engineered into an efficient allosteric protease, and that Na+ activation is interwoven with substrate selectivity in the trypsin scaffold.

  10. Relation of Na+, K(+)-ATPase to delayed motor nerve conduction velocity: effect of aldose reductase inhibitor, ADN-138, on Na+, K(+)-ATPase activity.

    PubMed

    Hirata, Y; Okada, K

    1990-06-01

    The role of sorbitol, myo-inositol, and Na+, K(+)-adenosine triphosphatase (ATPase) activity on motor nerve conduction velocity (MNCV) in streptozotocin (STZ)-diabetic rats was studied. Reduction of MNCV and Na+, K(+)-ATPase in caudal nerves appeared after 3 weeks of diabetes, and at this time treatment with aldose reductase inhibitor (ARI), ADN-138 and 1% myo-inositol supplement was begun. One percent myo-inositol supplement for 3 weeks resulted in a significant increase in myo-inositol levels in diabetic nerves, but left MNCV and sorbitol levels unchanged. In contrast, treatment with ADN-138 for 3 weeks reduced sorbitol levels in diabetic nerves and resulted in significant increases in MNCV and Na+, K(+)-ATPase in the nerves. Since ADN-138 did not restore myo-inositol levels, the increase in Na+, K(+)-ATPase levels by ADN-138 treatment was independent of myo-inositol levels. Also, nerve Na+ levels in ADN-138-treated rats were reduced and the ratio of K+ to Na+ was raised, while 1% myo-inositol supplement did not affect them. These results suggest that treatment with ADN-138 elevates MNCV through a series of processes: ARI----reduction of sorbitol level----increase in Na+, K(+)-ATPase activity----correction of K+, Na+ imbalance----increase in MNCV.

  11. Effect of TGFβ on Na{sup +}/K{sup +} ATPase activity in megakaryocytes

    SciTech Connect

    Hosseinzadeh, Zohreh; Schmid, Evi; Shumilina, Ekaterina; Laufer, Stefan; Borst, Oliver; Gawaz, Meinrad; Lang, Florian

    2014-09-26

    Highlights: • TGFß1 markedly up-regulates Na{sup +}/K{sup +} ATPase in megakaryocytes. • The effect is abrogated by p38-MAP kinase inhibitor skepinone. • The effect is abrogated by SGK inhibitor EMD638683. • The effect is abrogated by NF-κB inhibitor wogonin. - Abstract: The Na{sup +}/K{sup +} ATPase generates the Na{sup +} and K{sup +} concentration gradients across the plasma membrane and is thus essential for cellular electrolyte homeostasis, cell membrane potential and cell volume maintenance. A powerful regulator of Na{sup +}/K{sup +} ATPase is the serum- and glucocorticoid-inducible kinase 1 (SGK1). The most powerful known regulator of SGK1 expression is TGFß1, which is pivotal in the regulation of megakaryocyte maturation and platelet formation. Signaling involved in the upregulation of SGK1 by TGFß1 includes p38 mitogen activated protein (MAP) kinase. SGK1 in turn phosphorylates the IκB kinase (IKKα/β), which phosphorylates the inhibitor protein IκBα thus triggering nuclear translocation of nuclear factor kappa B (NF-κB). The present study explored whether TGFβ influences Na{sup +}/K{sup +} ATPase activity in megakaryocytes, and if so, whether the effect of TGß1 requires p38 MAP kinase, SGK1 and/or NF-κB. To this end, murine megakaryocytes were treated with TGFß1 and Na{sup +}/K{sup +} ATPase activity determined from K{sup +} induced current utilizing whole cell patch clamp. The pump current (I{sub pump}) was determined in the absence and presence of Na{sup +}/K{sup +} ATPase inhibitor ouabain (100 μM). TGFß1 (60 ng/ml) was added in the absence or presence of p38 MAP kinase inhibitor skepinone-L (1 μM), SGK1 inhibitor EMD638683 (50 μM) or NF-κB inhibitor wogonin (50 nM). As a result, the I{sub pump} was significantly increased by pretreatment of the megakaryocytes with TGFß1, an effect reaching statistical significance within 16 and 24 h and virtually abrogated in the presence of skepinone-L, EMD638683 or wogonin. In conclusion

  12. Comparative Transport Activity of Intact Cells, Membrane Vesicles, and Mesosomes of Bacillus licheniformis

    PubMed Central

    MacLeod, Robert A.; Thurman, Paul; Rogers, H. J.

    1973-01-01

    Sodium ion was shown to stimulate strongly the transport of l-glutamic acid into cells of Bacillus licheniformis 6346 His−. Lithium ion had a slight capacity to replace Na+ in this capacity, but K+ was without effect. Three of five amino acids tested. l-glutamic acid, l-aspartic acid, and l-alanine, were concentrated against a gradient in the cells. Intracellular pools of these amino acids were extractable with 5% trichloroacetic acid. Pools of l-histidine and l-lysine could not be detected. No evidence of active transport of lysine into cells could be detected, and histidine was taken up in the absence of chloramphenicol but not in its presence. The uptake of glutamic acid by membrane vesicle preparations was strongly stimulated by reduced nicotinamide adenine dinucleotide (NADH) and to a lesser extent by succinate. The presence of phenazine methosulfate increased uptake in the presence of succinate. Either l- or d-lactate and adenosine triphosphate were without effect. None of these compounds stimulated the uptake of glutamic acid by mesosomes, although some mesosome preparations contained separable membrane which was very active. NADH strongly stimulated the uptake of aspartic acid and alanine by membrane vesicles but had only a slight effect on the uptake of histidine and lysine. No evidence of active transport of any of the amino acids into mesosomes could be detected either in the presence or absence of NADH. NADH stimulation of the uptake of glutamic acid by membrane vesicles was destroyed by exposure to light of 360 nm; this inactivation was reversible by vitamin K2(5) or K2(10). Sodium ion stimulated transport of glutamic acid by membrane vesicles. PMID:4347247

  13. Activity of the Na,K-ATPase alpha4 isoform is important for membrane potential, intracellular Ca2+, and pH to maintain motility in rat spermatozoa.

    PubMed

    Jimenez, Tamara; Sánchez, Gladis; Wertheimer, Eva; Blanco, Gustavo

    2010-05-01

    While the function of the ubiquitous Na,K-ATPase alpha1 subunit has been well documented, the role of the sperm-specific alpha4 isoform of this ion transporter is less known. We have explored the importance of alpha4 in rat sperm physiology by taking advantage of the high sensitivity of this isoform for the inhibitor ouabain. Using concentrations that selectively block alpha4 activity, we found ouabain to reduce not only sperm total motility, but also multiple parameters of sperm movement, including progressive motility, straight line, curvilinear, and average path velocities, lateral head displacement, beat cross frequency, and linearity. According to a direct role of alpha4 in Na(+) transport, ouabain inhibition of alpha4 increased [Na(+)](i) in the male gametes. In addition, interference of alpha4 activity with ouabain produced cell membrane depolarization, diminished pH, and increased [Ca(2)(+)](i) in spermatozoa. Inhibition of alpha4 was sufficient to cause all these effects and additional blockage of alpha1, the other Na,K-ATPase alpha isoform expressed in sperm, and higher doses of ouabain did not result in further changes in the cell parameters studied. These results show that alpha4 is the Na,K-ATPase isoform primarily involved in controlling the transmembrane Na(+) gradient in sperm, and that alpha4 activity is necessary for maintaining membrane potential, [Ca(2)(+)](i), and [H(+)](i) in the cells. The high dependence of sperm motility on membrane excitability, [Ca(2)(+)](i), and acid-base balance suggests that their regulation is the mechanism by which alpha4 maintains motility of the male gametes.

  14. Vortical ciliary flows actively enhance mass transport in reef corals.

    PubMed

    Shapiro, Orr H; Fernandez, Vicente I; Garren, Melissa; Guasto, Jeffrey S; Debaillon-Vesque, François P; Kramarsky-Winter, Esti; Vardi, Assaf; Stocker, Roman

    2014-09-16

    The exchange of nutrients and dissolved gasses between corals and their environment is a critical determinant of the growth of coral colonies and the productivity of coral reefs. To date, this exchange has been assumed to be limited by molecular diffusion through an unstirred boundary layer extending 1-2 mm from the coral surface, with corals relying solely on external flow to overcome this limitation. Here, we present direct microscopic evidence that, instead, corals can actively enhance mass transport through strong vortical flows driven by motile epidermal cilia covering their entire surface. Ciliary beating produces quasi-steady arrays of counterrotating vortices that vigorously stir a layer of water extending up to 2 mm from the coral surface. We show that, under low ambient flow velocities, these vortices, rather than molecular diffusion, control the exchange of nutrients and oxygen between the coral and its environment, enhancing mass transfer rates by up to 400%. This ability of corals to stir their boundary layer changes the way that we perceive the microenvironment of coral surfaces, revealing an active mechanism complementing the passive enhancement of transport by ambient flow. These findings extend our understanding of mass transport processes in reef corals and may shed new light on the evolutionary success of corals and coral reefs.

  15. Vortical ciliary flows actively enhance mass transport in reef corals

    PubMed Central

    Shapiro, Orr H.; Fernandez, Vicente I.; Garren, Melissa; Guasto, Jeffrey S.; Debaillon-Vesque, François P.; Kramarsky-Winter, Esti; Vardi, Assaf; Stocker, Roman

    2014-01-01

    The exchange of nutrients and dissolved gasses between corals and their environment is a critical determinant of the growth of coral colonies and the productivity of coral reefs. To date, this exchange has been assumed to be limited by molecular diffusion through an unstirred boundary layer extending 1–2 mm from the coral surface, with corals relying solely on external flow to overcome this limitation. Here, we present direct microscopic evidence that, instead, corals can actively enhance mass transport through strong vortical flows driven by motile epidermal cilia covering their entire surface. Ciliary beating produces quasi-steady arrays of counterrotating vortices that vigorously stir a layer of water extending up to 2 mm from the coral surface. We show that, under low ambient flow velocities, these vortices, rather than molecular diffusion, control the exchange of nutrients and oxygen between the coral and its environment, enhancing mass transfer rates by up to 400%. This ability of corals to stir their boundary layer changes the way that we perceive the microenvironment of coral surfaces, revealing an active mechanism complementing the passive enhancement of transport by ambient flow. These findings extend our understanding of mass transport processes in reef corals and may shed new light on the evolutionary success of corals and coral reefs. PMID:25192936

  16. Regulation of NAD(P)H dehydrogenase-dependent cyclic electron transport around PSI by NaHSO₃ at low concentrations in tobacco chloroplasts.

    PubMed

    Wu, Yanxia; Zheng, Fangfang; Ma, Weimin; Han, Zhiguo; Gu, Qun; Shen, Yunkang; Mi, Hualing

    2011-10-01

    Although bisulfite at low concentrations (L-NaHSO₃) has been found to increase the cyclic electron transport around PSI (CET), its regulative mechanism remains unknown. In this work, the role of L-NaHSO₃ (0.1-500 μM) in NAD(P)H dehydrogenase-dependent CET (the NDH pathway) was investigated. After treatment of tobacco leaves with L-NaHSO₃, the NDH pathway, as reflected by a transient post-illumination increase in Chl fluorescence, the dark reduction of P700+ after far-red light and the amount of NDH, was increased after the light-dark-light transition, but was slightly lowered under continuous light. Meanwhile, the linear electron transport (LET) was accelerated by L-NaHSO₃ under both the light regimes. Experiments in thylakoids further demonstrated that both LET, monitored by light-dependent oxygen uptake, and CET, as determined from the NADPH-dependent oxygen uptake and dark reduction of P700+, were enhanced by L-NaHSO₃ and the enhancements were abolished by superoxide dismutase. Furthermore, L-NaHSO₃-induced CET was partially impaired in thylakoids of the ΔndhCKJ mutant, while L-NaHSO₃-induced LET was not affected. Based on these results, we propose that the photooxidation of L-NaHSO₃ initiated by superoxide anions in PSI regulates NDH pathway to maintain efficient photosynthesis. PMID:21828103

  17. Effect of changes in dietary sodium on active electrolyte transport by erythrocytes at different stages of human pregnancy.

    PubMed

    Gallery, E D; Rowe, J; Brown, M A; Ross, M

    1988-02-01

    1. Active electrolyte transport was examined in erythrocytes from women in the second and third trimesters of pregnancy and post partum, and compared with that in ovulating women. 2. There was a significant reduction in intracellular sodium ([Na]i) and increase in intracellular potassium ([K]i) in pregnancy with a return towards normal values in the post-partum period. 3. Maximum specific ouabain binding [number of Na+,K+-adenosine triphosphatase (Na+, K+-ATPase) units] was increased by 70% in pregnancy and returned slowly towards normal values post partum. 4. Na+,K+-ATPase activity as determined by ouabain-sensitive 86Rb influx in artificial media was also increased in pregnancy by 13%. It returned towards normal post partum. 5. The increases in Na+,K+-ATPase in pregnancy were not closely related to the concomitant increases in aldosterone or cholesterol nor to reticulocytosis and were not affected by 7 days of high (greater than 250 mmol/day) or low (less than 50 mmol/day) sodium intake.

  18. Platelet Serotonin Transporter Function Predicts Default-Mode Network Activity

    PubMed Central

    Kasess, Christian H.; Meyer, Bernhard M.; Hofmaier, Tina; Diers, Kersten; Bartova, Lucie; Pail, Gerald; Huf, Wolfgang; Uzelac, Zeljko; Hartinger, Beate; Kalcher, Klaudius; Perkmann, Thomas; Haslacher, Helmuth; Meyer-Lindenberg, Andreas; Kasper, Siegfried; Freissmuth, Michael; Windischberger, Christian; Willeit, Matthäus; Lanzenberger, Rupert; Esterbauer, Harald; Brocke, Burkhard; Moser, Ewald; Sitte, Harald H.; Pezawas, Lukas

    2014-01-01

    Background The serotonin transporter (5-HTT) is abundantly expressed in humans by the serotonin transporter gene SLC6A4 and removes serotonin (5-HT) from extracellular space. A blood-brain relationship between platelet and synaptosomal 5-HT reuptake has been suggested, but it is unknown today, if platelet 5-HT uptake can predict neural activation of human brain networks that are known to be under serotonergic influence. Methods A functional magnetic resonance study was performed in 48 healthy subjects and maximal 5-HT uptake velocity (Vmax) was assessed in blood platelets. We used a mixed-effects multilevel analysis technique (MEMA) to test for linear relationships between whole-brain, blood-oxygen-level dependent (BOLD) activity and platelet Vmax. Results The present study demonstrates that increases in platelet Vmax significantly predict default-mode network (DMN) suppression in healthy subjects independent of genetic variation within SLC6A4. Furthermore, functional connectivity analyses indicate that platelet Vmax is related to global DMN activation and not intrinsic DMN connectivity. Conclusion This study provides evidence that platelet Vmax predicts global DMN activation changes in healthy subjects. Given previous reports on platelet-synaptosomal Vmax coupling, results further suggest an important role of neuronal 5-HT reuptake in DMN regulation. PMID:24667541

  19. Activation of Na+ channels in cell membrane by capacitive stimulation with silicon chip

    NASA Astrophysics Data System (ADS)

    Schoen, Ingmar; Fromherz, Peter

    2005-11-01

    Sodium channels are the crucial electrical elements of neuronal excitation. As a step toward hybrid neuron-semiconductor devices, we studied the activation of recombinant NaV1.4 sodium channels in human embryonic kidney (HEK293) cells by stimulation from an electrolyte/oxide/silicon (EOS) capacitor. HfO2 was used as an insulator to attain a high capacitance. An effective activation was achieved by decaying voltage ramps at constant intracellular voltage at a depleted NaCl concentration in the bath to enhance the resistance of the cell-chip contact. We were also able to open sodium channels at a NaCl concentration close to physiological conditions. This experiment provides a basis for noninvasive capacitive stimulation of nerve cells with semiconductor chips.

  20. [Na,K-ATPase activity of erythrocytes of rats during prolonged starvation].

    PubMed

    Skverchinskaia, E A; Tavrovskaia, T V; Novozhilov, A V

    2013-01-01

    Activity of Na,K-ATPase (Na+,K+-adenosine triphosphatase, EC 3.6.3.9) in the whole erythrocytes was studied in dynamics of the complete rat alimentary starvation for 1, 3, 5, 7-8, and 10-12 days with water drinking ad libitum. There has been established a change of the erythrocyte Na,K-ATPase activity depending on the phase of starvation (the period connected with a certain level of metabolism). After the state on an empty stomach and adaptation to endogenous nutrition (the 0-I phase), from the 3rd to the 7-8th starvation day, the II phase, the period of compensated adaptation occurs (the euglycemia is preserved, the plateau level is preserved, the plateau level is achieved for protein loss and hormonal stimulation). Changes of the Na,K-ATPase activity level within the limits of the II phase were insignificant (p < 0.05), but loses of potassium content in plasma and erythrocytes have been from the 5th starvation day. The III phase (the 12-13th day) is the beginning of the terminal period and is characterized by a decrease of the Na,K-ATPase activity (the oubain-sensitive activity) and of Mg2+-ATPase (the oubain-independent activity), by a decrease of the plasma sodium level (prior to that, this level remained practically unchanged). Ad causes of the revealed decrease of the ATPase activities at the long-term starvation, there are considered aging of population of circulating erythrocytes (the absence of reticulocytes and young erythrocytes), depletion of cell energetic resources (hypoglycemia and glycopenia), effect of endogenous oubain, and endotoxemia.

  1. Evaluation of the Physical Activity Biography: Sport and Transport

    PubMed Central

    Rogen, Sandra; Hofmann, Peter; Bauernhofer, Thomas; Müller, Wolfram

    2014-01-01

    Beside the genetic disposition, physical activity (PA) is one of the major health factors and can play a large role in the prevention and therapy of many diseases (cardiovascular diseases, cancer, obesity-related diseases etc.). In contrast to the genetic disposition, PA can be deliberately influenced by lifestyle. Therefore, it is of high importance to assess PA patterns. In order to assess PA reliably and validly, a new questionnaire (Physical Activity Biography, PAB) was created. The PAB assesses recreational PA (sport and transport) and enables to distinguish between endurance intensity levels and considers strength and high speed activity patterns throughout life. This study aims to evaluate the PAB by means of item analysis, retest-reliability and validity (criteria were physical fitness assessed by the questionnaire FFB-mot and by exercise tests). 141 participants answered the PAB. For deriving retest-reliability, 81 participants completed the PAB after a retest-interval of one month again. 55 participated in exercise tests and answered the FFB-mot to determine construct validity. Retest-reliability (ICC) above 0.7 was found for most items. For the items assessing recent PA, the criteria of convergent and discriminant validity were given. Despite the complexity of the question under study, the results fulfilled the expectations concerning reliability and validity. The PAB enables to assess the amount of sport and locomotion a person has accomplished during different life time frames and, because of the protective effects of PA on various diseases, may become an important tool for risk assessment. Key points The risk of chronic diseases depends largely on physical activity biography. A new questionnaire (PAB) assessing recent and lifetime physical activity was created. The PAB assesses physical activity during sports and transport. The results of the evaluation of the PAB fulfilled the expectations. The PAB enables to determine a person’s amount of

  2. Curcumin directly inhibits the transport activity of GLUT1

    PubMed Central

    Gunnink, Leesha K.; Alabi, Ola D.; Kuiper, Benjamin D.; Gunnink, Stephen M.; Schuiteman, Sam J.; Strohbehn, Lauren E.; Hamilton, Kathryn E.; Wrobel, Kathryn E.; Louters, Larry L.

    2016-01-01

    Curcumin, a major ingredient in turmeric, has a long history of medicinal applications in a wide array of maladies including treatment for diabetes and cancer. Seemingly counterintuitive to the documented hypoglycemic effects of curcumin, however, a recent report indicates that curcumin directly inhibits glucose uptake in adipocytes. The major glucose transporter in adipocytes is GLUT4. Therefore, this study investigates the effects of curcumin in cell lines where the major transporter is GLUT1. We report that curcumin has an immediate inhibitory effect on basal glucose uptake in L929 fibroblast cells with a maximum inhibition of 80% achieved at 75 μM curcumin. Curcumin also blocks activation of glucose uptake by azide, glucose deprivation, hydroxylamine, or phenylarsine oxide. Inhibition does not increase with exposure time and the inhibitory effects reverse within an hour. Inhibition does not appear to involve a reaction between curcumin and the thiol side chain of a cysteine residue since neither prior treatment of cells with iodoacetamide nor curcumin with cysteine alters curcumin’s inhibitory effects. Curcumin is a mixed inhibitor reducing the Vmax of 2DG transport by about half with little effect on the Km. The inhibitory effects of curcumin are not additive to the effects of cytochalasin B and 75 μM curcumin actually reduces specific cytochalasin B binding by 80%. Taken together, the data suggest that curcumin binds directly to GLUT1 at a site that overlaps with the cytochalasin B binding site and thereby inhibits glucose transport. A direct inhibition of GLUT proteins in intestinal epithelial cells would likely reduce absorption of dietary glucose and contribute to a hypoglycemic effect of curcumin. Also, inhibition of GLUT1 activity might compromise cancer cells that overexpress GLUT1 and be another possible mechanism for the documented anticancer effects of curcumin. PMID:27039889

  3. Urinary Proteolytic Activation of Renal Epithelial Na+ Channels in Chronic Heart Failure.

    PubMed

    Zheng, Hong; Liu, Xuefei; Sharma, Neeru M; Li, Yulong; Pliquett, Rainer U; Patel, Kaushik P

    2016-01-01

    One of the key mechanisms involved in renal Na(+) retention in chronic heart failure (CHF) is activation of epithelial Na(+) channels (ENaC) in collecting tubules. Proteolytic cleavage has an important role in activating ENaC. We hypothesized that enhanced levels of proteases in renal tubular fluid activate ENaC, resulting in renal Na(+) retention in rats with CHF. CHF was produced by left coronary artery ligation in rats. By immunoblotting, we found that several urinary serine proteases were significantly increased in CHF rats compared with sham rats (fold increases: furin 6.7, prostasin 23.6, plasminogen 2.06, and plasmin 3.57 versus sham). Similar increases were observed in urinary samples from patients with CHF. Whole-cell patch clamp was conducted in cultured renal collecting duct M-1 cells to record Na(+) currents. Protease-rich urine (from rats and patients with CHF) significantly increased the Na(+) inward current in M-1 cells. Two weeks of protease inhibitor treatment significantly abrogated the enhanced diuretic and natriuretic responses to ENaC inhibitor benzamil in rats with CHF. Increased podocyte lesions were observed in the kidneys of rats with CHF by transmission electron microscopy. Consistent with these results, podocyte damage markers desmin and podocin expressions were also increased in rats with CHF (increased ≈2-folds). These findings suggest that podocyte damage may lead to increased proteases in the tubular fluid, which in turn contributes to the enhanced renal ENaC activity, providing a novel mechanistic insight for Na(+) retention commonly observed in CHF.

  4. Active ingredients in Chinese medicines promoting blood circulation as Na+/K+-ATPase inhibitors

    PubMed Central

    Chen, Ronald JY; Jinn, Tzyy-rong; Chen, Yi-ching; Chung, Tse-yu; Yang, Wei-hung; Tzen, Jason TC

    2011-01-01

    The positive inotropic effect of cardiac glycosides lies in their reversible inhibition on the membrane-bound Na+/K+-ATPase in human myocardium. Steroid-like compounds containing a core structure similar to cardiac glycosides are found in many Chinese medicines conventionally used for promoting blood circulation. Some of them are demonstrated to be Na+/K+-ATPase inhibitors and thus putatively responsible for their therapeutic effects via the same molecular mechanism as cardiac glycosides. On the other hand, magnesium lithospermate B of danshen is also proposed to exert its cardiac therapeutic effect by effectively inhibiting Na+/K+-ATPase. Theoretical modeling suggests that the number of hydrogen bonds and the strength of hydrophobic interaction between the effective ingredients of various medicines and residues around the binding pocket of Na+/K+-ATPase are crucial for the inhibitory potency of these active ingredients. Ginsenosides, the active ingredients in ginseng and sanqi, substantially inhibit Na+/K+-ATPase when sugar moieties are attached only to the C-3 position of their steroid-like structure, equivalent to the sugar position in cardiac glycosides. Their inhibitory potency is abolished, however, when sugar moieties are linked to C-6 or C-20 position of the steroid nucleus; presumably, these sugar attachments lead to steric hindrance for the entrance of ginsenosides into the binding pocket of Na+/K+-ATPase. Neuroprotective effects of cardiac glycosides, several steroid-like compounds, and magnesium lithospermate B against ischemic stroke have been accordingly observed in a cortical brain slice-based assay model, and cumulative data support that effective inhibitors of Na+/K+-ATPase in the brain could be potential drugs for the treatment of ischemic stroke. PMID:21293466

  5. Active ingredients in Chinese medicines promoting blood circulation as Na+/K+ -ATPase inhibitors.

    PubMed

    Chen, Ronald J Y; Jinn, Tzyy-rong; Chen, Yi-ching; Chung, Tse-yu; Yang, Wei-hung; Tzen, Jason T C

    2011-02-01

    The positive inotropic effect of cardiac glycosides lies in their reversible inhibition on the membrane-bound Na(+)/K(+)-ATPase in human myocardium. Steroid-like compounds containing a core structure similar to cardiac glycosides are found in many Chinese medicines conventionally used for promoting blood circulation. Some of them are demonstrated to be Na(+)/K(+)-ATPase inhibitors and thus putatively responsible for their therapeutic effects via the same molecular mechanism as cardiac glycosides. On the other hand, magnesium lithospermate B of danshen is also proposed to exert its cardiac therapeutic effect by effectively inhibiting Na(+)/K(+)-ATPase. Theoretical modeling suggests that the number of hydrogen bonds and the strength of hydrophobic interaction between the effective ingredients of various medicines and residues around the binding pocket of Na(+)/K(+)-ATPase are crucial for the inhibitory potency of these active ingredients. Ginsenosides, the active ingredients in ginseng and sanqi, substantially inhibit Na(+)/K(+)-ATPase when sugar moieties are attached only to the C-3 position of their steroid-like structure, equivalent to the sugar position in cardiac glycosides. Their inhibitory potency is abolished, however, when sugar moieties are linked to C-6 or C-20 position of the steroid nucleus; presumably, these sugar attachments lead to steric hindrance for the entrance of ginsenosides into the binding pocket of Na(+)/K(+)-ATPase. Neuroprotective effects of cardiac glycosides, several steroid-like compounds, and magnesium lithospermate B against ischemic stroke have been accordingly observed in a cortical brain slice-based assay model, and cumulative data support that effective inhibitors of Na(+)/K(+)-ATPase in the brain could be potential drugs for the treatment of ischemic stroke.

  6. Saharan Dust, Transport Processes, and Possible Impacts on Hurricane Activities

    NASA Technical Reports Server (NTRS)

    Lau, William K. M.; Kim, K. M.

    2010-01-01

    In this paper, we present observational evidence of significant relationships between Saharan dust outbreak, and African Easterly wave activities and hurricane activities. We found two dominant paths of transport of Saharan dust: a northern path, centered at 25degN associated with eastward propagating 6-19 days waves over northern Africa, and a southern path centered at 15degN, associated with the AEW, and the Atlantic ITCZ. Seasons with stronger dust outbreak from the southern path are associated with a drier atmosphere over the Maximum Development Region (MDR) and reduction in tropical cyclone and hurricane activities in the MDR. Seasons with stronger outbreak from the northern path are associated with a cooler N. Atlantic, and suppressed hurricane in the western Atlantic basin.

  7. Cryo-EM structure of the Slo2.2 Na+-activated K+ channel

    PubMed Central

    Hite, Richard; Yuan, Peng; Li, Zongli; Hsuing, Yichun; Walz, Thomas; MacKinnon, Roderick

    2015-01-01

    Na+-activated K+ channels are members of the Slo family of large conductance K+ channels that are widely expressed in the brain, where their opening regulates neuronal excitability. These channels are fascinating for the biological roles they fulfill as well as for their intriguing biophysical properties, including conductance levels ten times most other K+ channels and gating sensitivity to intracellular Na+. Here we present the structure a complete Na+-activated K+ channel, Slo2.2, in the Na+-free state, determined by cryo-electron microscopy at a nominal resolution of 4.5 Å. The channel is composed of a large cytoplasmic gating ring within which resides the Na+-binding site and a transmembrane domain that closely resembles voltage-gated K+ channels. In the structure, the cytoplasmic domain adopts a closed conformation and the ion conduction pore is also closed. The structure provides a first view of a member of the Slo K+ channel family, which reveals features explaining their high conductance and gating mechanism. PMID:26436452

  8. Discovery of a Biological Mechanism of Active Transport through the Tympanic Membrane to the Middle Ear

    PubMed Central

    Kurabi, Arwa; Pak, Kwang K.; Bernhardt, Marlen; Baird, Andrew; Ryan, Allen F.

    2016-01-01

    Otitis media (OM) is a common pediatric disease for which systemic antibiotics are often prescribed. While local treatment would avoid the systemic treatment side-effects, the tympanic membrane (TM) represents an impenetrable barrier unless surgically breached. We hypothesized that the TM might harbor innate biological mechanisms that could mediate trans-TM transport. We used two M13-bacteriophage display biopanning strategies to search for mediators of trans-TM transport. First, aliquots of linear phage library displaying 1010th 12mer peptides were applied on the TM of rats with active bacterial OM. The middle ear (ME) contents were then harvested, amplified and the preparation re-applied for additional rounds. Second, the same naïve library was sequentially screened for phage exhibiting TM binding, internalization and then transit. Results revealed a novel set of peptides that transit across the TM to the ME in a time and temperature dependent manner. The peptides with highest transport capacities shared sequence similarities. Historically, the TM was viewed as an impermeable barrier. However, our studies reveal that it is possible to translocate peptide-linked small particles across the TM. This is the first comprehensive biopanning for the isolation of TM transiting peptidic ligands. The identified mechanism offers a new drug delivery platform into the ME. PMID:26946957

  9. [The effect of a mite allergen on Na/H metabolic activity in peritoneal mast cells].

    PubMed

    Khlgatian, S V; Pinelis, V G; Berzhets, V M; Strukova, S M

    1992-12-01

    Mite allergen interacting with mast cells treated with sera from bronchial patient sensitized to home dust Dermatophagoides farinae causes changes in intracellular pH. Regulation of pHi peritoneal mast cells is participated by Na/H metabolism probably activated by protein kinase C.

  10. Impact of humic acid fouling on membrane performance and transport of pharmaceutically active compounds in forward osmosis.

    PubMed

    Xie, Ming; Nghiem, Long D; Price, William E; Elimelech, Menachem

    2013-09-01

    The impact of humic acid fouling on the membrane transport of two pharmaceutically active compounds (PhACs) - namely carbamazepine and sulfamethoxazole - in forward osmosis (FO) was investigated. Deposition of humic acid onto the membrane surface was promoted by the complexation with calcium ions in the feed solution and the increase in ionic strength at the membrane surface due to the reverse transport of NaCl draw solute. The increase in the humic acid deposition on the membrane surface led to a substantial decrease in the membrane salt (NaCl) permeability coefficient but did not result in a significant decrease in the membrane pure water permeability coefficient. As the deposition of humic acid increased, the permeation of carbamazepine and sulfamethoxazole decreased, which correlated well with the decrease in the membrane salt (NaCl) permeability coefficient. It is hypothesized that the hydrated humic acid fouling layer hindered solute diffusion through the membrane pore and enhanced solute rejection by steric hindrance, but not the permeation of water molecules. The membrane water and salt (NaCl) permeability coefficients were fully restored by physical cleaning of the membrane, suggesting that humic acid did not penetrate into the membrane pores.

  11. Impact of humic acid fouling on membrane performance and transport of pharmaceutically active compounds in forward osmosis.

    PubMed

    Xie, Ming; Nghiem, Long D; Price, William E; Elimelech, Menachem

    2013-09-01

    The impact of humic acid fouling on the membrane transport of two pharmaceutically active compounds (PhACs) - namely carbamazepine and sulfamethoxazole - in forward osmosis (FO) was investigated. Deposition of humic acid onto the membrane surface was promoted by the complexation with calcium ions in the feed solution and the increase in ionic strength at the membrane surface due to the reverse transport of NaCl draw solute. The increase in the humic acid deposition on the membrane surface led to a substantial decrease in the membrane salt (NaCl) permeability coefficient but did not result in a significant decrease in the membrane pure water permeability coefficient. As the deposition of humic acid increased, the permeation of carbamazepine and sulfamethoxazole decreased, which correlated well with the decrease in the membrane salt (NaCl) permeability coefficient. It is hypothesized that the hydrated humic acid fouling layer hindered solute diffusion through the membrane pore and enhanced solute rejection by steric hindrance, but not the permeation of water molecules. The membrane water and salt (NaCl) permeability coefficients were fully restored by physical cleaning of the membrane, suggesting that humic acid did not penetrate into the membrane pores. PMID:23764606

  12. Modulation of Na+/K+ ATPase Activity by Hydrogen Peroxide Generated through Heme in L. amazonensis.

    PubMed

    Rocco-Machado, Nathália; Cosentino-Gomes, Daniela; Meyer-Fernandes, José Roberto

    2015-01-01

    Leishmania amazonensis is a protozoan parasite that occurs in many areas of Brazil and causes skin lesions. Using this parasite, our group showed the activation of Na+/K+ ATPase through a signaling cascade that involves the presence of heme and protein kinase C (PKC) activity. Heme is an important biomolecule that has pro-oxidant activity and signaling capacity. Reactive oxygen species (ROS) can act as second messengers, which are required in various signaling cascades. Our goal in this work is to investigate the role of hydrogen peroxide (H2O2) generated in the presence of heme in the Na+/K+ ATPase activity of L. amazonensis. Our results show that increasing concentrations of heme stimulates the production of H2O2 in a dose-dependent manner until a concentration of 2.5 μM heme. To confirm that the effect of heme on the Na+/K+ ATPase is through the generation of H2O2, we measured enzyme activity using increasing concentrations of H2O2 and, as expected, the activity increased in a dose-dependent manner until a concentration of 0.1 μM H2O2. To investigate the role of PKC in this signaling pathway, we observed the production of H2O2 in the presence of its activator phorbol 12-myristate 13-acetate (PMA) and its inhibitor calphostin C. Both showed no effect on the generation of H2O2. Furthermore, we found that PKC activity is increased in the presence of H2O2, and that in the presence of calphostin C, H2O2 is unable to activate the Na+/K+ ATPase. 100 μM of Mito-TEMPO was capable of abolishing the stimulatory effect of heme on Na+/K+ ATPase activity, indicating that mitochondria might be the source of the hydrogen peroxide production induced by heme. The modulation of L. amazonensis Na+/K+ ATPase by H2O2 opens new possibilities for understanding the signaling pathways of this parasite. PMID:26070143

  13. Electron transport chain inhibitors induce microglia activation through enhancing mitochondrial reactive oxygen species production.

    PubMed

    Ye, Junli; Jiang, Zhongxin; Chen, Xuehong; Liu, Mengyang; Li, Jing; Liu, Na

    2016-01-15

    Reactive oxygen species (ROS) are believed to be mediators of excessive microglial activation, yet the resources and mechanism are not fully understood. Here we stimulated murine microglial BV-2 cells and primary microglial cells with different inhibitors of electron transport chain (ETC), rotenone, thenoyltrifluoroacetone (TTFA), antimycin A, and NaN3 to induce mitochondrial ROS production and we observed the role of mitochondrial ROS in microglial activation. Our results showed that ETC inhibitors resulted in significant changes in cell viability, microglial morphology, cell cycle arrest and mitochondrial ROS production in a dose-dependent manner in both primary cultural microglia and BV-2 cell lines. Moreover, ETC inhibitors, especially rotenone and antimycin A stimulated secretion of interleukin 1β (IL-1β), interleukin 6 (IL-6), interleukin 12 (IL-12) and tumor necrosis factor α (TNF-α) by microglia with marked activation of mitogen-activated proteinkinases (MAPKs) and nuclear factor κB (NF-κB), which could be blocked by specific inhibitors of MAPK and NF-κB and mitochondrial antioxidants, Mito-TEMPO. Taken together, our results demonstrated that inhibition of mitochondrial respiratory chain in microglia led to production of mitochondrial ROS and therefore may activate MAPK/NF-кB dependent inflammatory cytokines release in microglia, which indicated that mitochondrial-derived ROS were contributed to microglial activation.

  14. Active urea transport by the skin of Bufo viridis: Amiloride- and phloretin-sensitive transport sites

    SciTech Connect

    Rapoport, J.; Abuful, A.; Chaimovitz, C.; Noeh, Z.; Hays, R.M. Albert Einstein College of Medicine, New York, NY )

    1988-09-01

    Urea is actively transported inwardly (J{sub i}) across the skin of the green toad Bufo viridis. J{sub i} is markedly enhanced in toads adapted to hypertonic saline. The authors studied urea transport across the skin of Bufo viridis under a variety of experimental conditions, including treatment with amiloride and phloretin, agents that inhibit urea permeability in the bladder of Bufo marinus. Amiloride (10{sup {minus}4} M) significantly inhibited J{sub i} in both adapted and unadapted animals and was unaffected by removal of sodium from the external medium. Phloretin (10{sup {minus}4} M) significantly inhibited J{sub i} in adapted animals by 23-46%; there was also a reduction in J{sub i} in unadapted toads at 10{sup {minus}4} and 5 {times} 10{sup {minus}4} M phloretin. A dose-response study revealed that the concentration of phloretin causing half-maximal inhibition (K{sub {1/2}}) was 5 {times} 10{sup {minus}4} M for adapted animals. J{sub i} was unaffected by the substitution of sucrose for Ringer solution or by ouabain. They conclude (1) the process of adaptation appears to involve an increase in the number of amiloride- and phloretin-inhibitable urea transport sites in the skin, with a possible increase in the affinity of the sites for phloretin; (2) the adapted skin resembles the Bufo marinus urinary bladder with respect to amiloride and phloretin-inhibitable sites; (3) they confirm earlier observations that J{sub i} is independent of sodium transport.

  15. Active transport and accumulation of bicarbonate by a unicellular cyanobacterium.

    PubMed

    Miller, A G; Colman, B

    1980-09-01

    The rates of inorganic carbon accumulation and carbon fixation in light by the unicellular cyanobacterim Coccohloris peniocystis have been determined. Cells incubated in the light in medium containing H14CO3- were rapidly separated from the medium by centrifugation through silicone oil into a strongly basic terminating solution. Samples of these inactivated cells were assayed to determine total 14C accumulation, and acid-treated samples were assayed to determine 14C fixation. The rate of transport of inorganic into illuminated cells was faster than the rate of CO2 production in the medium from HCO3- dehydration. This evidence for HCO3- transport in these cells is in agreement with our previous results based upon measurements of photosynthetic O2 evolution. A substantial pool of inorganic carbon was bulit up within the cells presumably as HCO3- before the onset of the maximum rate of photosynthesis. Large accumulation ratios were observed, greater than 1,000 times the external HCO3- concentration. Accumulation did not occur in the dark and was greatly suppressed by the photosynthesis inhibitors 3-(3,4-dichlorophenyl)-1,1-dimethyl urea and 3-chloro-carbonylcyanide phenylhydrazone. These results indicate that the accumulation of inorganic carbon in these cells involves a light-dependent active transport process. PMID:6773925

  16. CFD Model of Water Droplet Transport for ISS Hygiene Activity

    NASA Technical Reports Server (NTRS)

    Son, Chang H.

    2011-01-01

    The goal of the study is to assess the impacts of free water propagation in the Waste and Hygiene Compartment (WHC). Free water can be generated inside the WHC in small quantities due to crew hygiene activity. To mitigate potential impact of free water in Node 3 cabin the WHC doorway is enclosed by a waterproof bump-out, Kabin, with openings at the top and bottom. At the overhead side of the rack, there is a screen that prevents large drops of water from exiting. However, as the avionics fan in the WHC causes airflow toward the deck side of the rack, small quantities of free water may exit at the bottom of the Kabin. A Computational Fluid Dynamics (CFD) analysis of Node 3 cabin airflow made possible to identify the paths of water transport. The Node 3 airflow was computed for several ventilation scenarios. To simulate the droplet transport the Lagrangian discrete phase approach was used. Various initial droplet distributions were considered in the study. The droplet diameter was varied in the range of 2-20 mm. The results of the computations showed that most of the drops fall to the rack surface not far from the WHC curtain. The probability of the droplet transport to the adjacent rack surface with electronic equipment was predicted.

  17. Essential role for NHERF in cAMP-mediated inhibition of the Na+-HCO3- co-transporter in BSC-1 cells.

    PubMed

    Weinman, E J; Evangelista, C M; Steplock, D; Liu, M Z; Shenolikar, S; Bernardo, A

    2001-11-01

    Prior studies have indicated a requirement for the PDZ domain-containing protein, Na(+)/H(+) Exchanger Regulatory Factor (NHERF), for protein kinase A (PKA)-mediated inhibition of the renal basolateral Na(+)-HCO(3)(-) co-transporter (NBC). The present studies explore the potential mechanisms by which NHERF transduces cAMP signals to inhibit NBC. In BSC-1 cells, cells that express NBC but lack NHERF, 8-bromo-cAMP (100 microm for 15 min) failed to inhibit transport until wild-type mNHERF-(1-355) was expressed. mNHERF-(116-355) containing PDZ II and C-terminal ezrin-binding sequences or a mutant unphosphorylated form of rabbit NHERF effectively transduced the cAMP signals that inhibited NBC. By contrast, mNHERF-(1-126) encompassing N-terminal PDZ I and mNHERF-(1-325), which lacks ezrin-binding, failed to support cAMP inhibition of NBC activity. NBC and NHERF did not associate with each other in yeast two-hybrid or co-immunoprecipitation assays, and confocal microscopy indicated distinct subcellular localization of the two proteins. NBC was phosphorylated in BSC-1 cells, but its phosphorylation was not increased by cAMP nor was immunoprecipitated NBC phosphorylated by PKA in vitro. Acute exposure of mNHERF-(1-355)-expressing BSC-1 cells to cAMP did not change cell surface expression of NBC. Although these results established an essential role for NHERF in cAMP-mediated inhibition of NBC in BSC-1 cells, they also suggest a novel mechanism for NHERF-mediated signal transduction distinct from that previously characterized from studies of other NHERF targets.

  18. Activation of the epithelial Na+ channel in the collecting duct by vasopressin contributes to water reabsorption.

    PubMed

    Bugaj, Vladislav; Pochynyuk, Oleh; Stockand, James D

    2009-11-01

    We used patch-clamp electrophysiology on isolated, split-open murine collecting ducts (CD) to test the hypothesis that regulation of epithelial sodium channel (ENaC) activity is a physiologically important effect of vasopressin. Surprisingly, this has not been tested directly before. We ask whether vasopressin affects ENaC activity distinguishing between acute and chronic effects, as well as, parsing the cellular signaling pathway and molecular mechanism of regulation. In addition, we quantified possible synergistic regulation of ENaC by vasopressin and aldosterone associating this with a requirement for distal nephron Na+ reabsorption during water conservation vs. maintenance of Na+ balance. We find that vasopressin significantly increases ENaC activity within 2-3 min by increasing open probability (P(o)). This activation was dependent on adenylyl cyclase (AC) and PKA. Water restriction (18-24 h) and pretreatment of isolated CD with vasopressin (approximately 30 min) resulted in a similar increase in P(o). In addition, this also increased the number (N) of active ENaC in the apical membrane. Similar to P(o), increases in N were sensitive to inhibitors of AC. Stressing animals with water and salt restriction separately and jointly revealed an important effect of vasopressin: conservation of water and Na+ each independently increased ENaC activity and jointly had a synergistic effect on channel activity. These results demonstrate a quantitatively important action of vasopressin on ENaC suggesting that distal nephron Na+ reabsorption mediated by this channel contributes to maintenance of water reabsorption. In addition, our results support that the combined actions of vasopressin and aldosterone are required to achieve maximally activated ENaC. PMID:19692483

  19. Activation of the epithelial Na+ channel in the collecting duct by vasopressin contributes to water reabsorption.

    PubMed

    Bugaj, Vladislav; Pochynyuk, Oleh; Stockand, James D

    2009-11-01

    We used patch-clamp electrophysiology on isolated, split-open murine collecting ducts (CD) to test the hypothesis that regulation of epithelial sodium channel (ENaC) activity is a physiologically important effect of vasopressin. Surprisingly, this has not been tested directly before. We ask whether vasopressin affects ENaC activity distinguishing between acute and chronic effects, as well as, parsing the cellular signaling pathway and molecular mechanism of regulation. In addition, we quantified possible synergistic regulation of ENaC by vasopressin and aldosterone associating this with a requirement for distal nephron Na+ reabsorption during water conservation vs. maintenance of Na+ balance. We find that vasopressin significantly increases ENaC activity within 2-3 min by increasing open probability (P(o)). This activation was dependent on adenylyl cyclase (AC) and PKA. Water restriction (18-24 h) and pretreatment of isolated CD with vasopressin (approximately 30 min) resulted in a similar increase in P(o). In addition, this also increased the number (N) of active ENaC in the apical membrane. Similar to P(o), increases in N were sensitive to inhibitors of AC. Stressing animals with water and salt restriction separately and jointly revealed an important effect of vasopressin: conservation of water and Na+ each independently increased ENaC activity and jointly had a synergistic effect on channel activity. These results demonstrate a quantitatively important action of vasopressin on ENaC suggesting that distal nephron Na+ reabsorption mediated by this channel contributes to maintenance of water reabsorption. In addition, our results support that the combined actions of vasopressin and aldosterone are required to achieve maximally activated ENaC.

  20. Pharmacological evidence that the activation of the Na+-Ca2+ exchanger protects C6 glioma cells during chemical hypoxia

    PubMed Central

    Amoroso, Salvatore; De Maio, Matteo; Russo, Giovanni M; Catalano, Annalisa; Bassi, Antonella; Montagnani, Stefania; Di Renzo, Gianfranco; Annunziato, Lucio

    1997-01-01

    In C6 glioma cells exposed to chemical hypoxia a massive release of lactate dehydrogenase (LDH) occurred at 3 and 6 h, coupled with an increased number of propidium-iodide positive dead cells. Extracellular Na+ removal, which activates the Na+-Ca2+ exchanger as a Na+ efflux pathway and prevents Na+ entrance, significantly reduced LDH release and the number of propidium iodide positive C6 cells. During chemical hypoxia, in the presence of extracellular Na+ ions, a progressive increase of [Ca2+]i occurred; in the absence of extracellular Na+ ions [Ca2+]i was enhanced to a greater extent. The blockade of the Na+-Ca2+ exchanger by the amiloride derivative 5-(N-4-chlorobenzyl)-2′,4′-dimethylbenzamil (CB-DMB), lanthanum (La3+) and the Ca2+ chelator EGTA, completely reverted the protective effect exerted by the removal of Na+ ions on C6 glioma cells exposed to chemical hypoxia. The inhibition of the Na+-Ca2+ antiporter enhanced chemical hypoxia-induced LDH release when C6 glioma cells were incubated in the presence of physiological concentrations of extracellular Na+ ions (145 mM), suggesting that the blockade of the Na+-Ca2+ antiporter during chemical hypoxia can lead to increased cell damage. Collectively, these results suggest that activation of the Na+-Ca2+ exchanger protects C6 glioma cells exposed to chemical hypoxia, whereas its pharmacological blockade can exacerbate cellular injury. PMID:9154341

  1. Simulation of Cl− Secretion in Epithelial Tissues: New Methodology Estimating Activity of Electro-Neutral Cl− Transporter

    PubMed Central

    Sasamoto, Kouhei; Niisato, Naomi; Taruno, Akiyuki; Marunaka, Yoshinori

    2015-01-01

    Transcellular Cl− secretion is, in general, mediated by two steps; (1) the entry step of Cl− into the cytosolic space from the basolateral space across the basolateral membrane by Cl− transporters, such as Na+-K+-2Cl− cotransporter (NKCC1, an isoform of NKCC), and (2) the releasing step of Cl− from the cytosolic space into the luminal (air) space across the apical membrane via Cl− channels, such as cystic fibrosis transmembrane conductance regulator (CFTR) Cl− channel. Transcellular Cl− secretion has been characterized by using various experimental techniques. For example, measurements of short-circuit currents in the Ussing chamber and patch clamp techniques provide us information on transepithelial ion movements via transcellular pathway, transepithelial conductance, activity (open probability) of single channel, and whole cell currents. Although many investigators have tried to clarify roles of Cl− channels and transporters located at the apical and basolateral membranes in transcellular Cl− secretion, it is still unclear how Cl− channels/transporters contribute to transcellular Cl− secretion and are regulated by various stimuli such as Ca2+ and cAMP. In the present study, we simulate transcellular Cl− secretion using mathematical models combined with electrophysiological measurements, providing information on contribution of Cl− channels/transporters to transcellular Cl− secretion, activity of electro-neutral ion transporters and how Cl− channels/transporters are regulated. PMID:26779025

  2. Adult Active Transport in the Netherlands: An Analysis of Its Contribution to Physical Activity Requirements

    PubMed Central

    Fishman, Elliot; Böcker, Lars; Helbich, Marco

    2015-01-01

    Introduction Modern, urban lifestyles have engineered physical activity out of everyday life and this presents a major threat to human health. The Netherlands is a world leader in active travel, particularly cycling, but little research has sought to quantify the cumulative amount of physical activity through everyday walking and cycling. Methods Using data collected as part of the Dutch National Travel Survey (2010 – 2012), this paper determines the degree to which Dutch walking and cycling contributes to meeting minimum level of physical activity of 150 minutes of moderate intensity aerobic activity throughout the week. The sample includes 74,465 individuals who recorded at least some travel on the day surveyed. As physical activity benefits are cumulative, all walking and cycling trips are analysed, including those to and from public transport. These trips are then converted into an established measure of physical activity intensity, known as metabolic equivalents of tasks. Multivariate Tobit regression models were performed on a range of socio-demographic, transport resources, urban form and meteorological characteristics. Results The results reveal that Dutch men and women participate in 24 and 28 minutes of daily physical activity through walking and cycling, which is 41% and 55% more than the minimum recommended level. It should be noted however that some 57% of the entire sample failed to record any walking or cycling, and an investigation of this particular group serves as an important topic of future research. Active transport was positively related with age, income, bicycle ownership, urban density and air temperature. Car ownership had a strong negative relationship with physically active travel. Conclusion The results of this analysis demonstrate the significance of active transport to counter the emerging issue of sedentary lifestyle disease. The Dutch experience provides other countries with a highly relevant case study in the creation of

  3. NaCl-activated extracellular proteinase from Virgibacillus sp. SK37 isolated from fish sauce fermentation.

    PubMed

    Sinsuwan, S; Rodtong, S; Yongsawatdigul, J

    2007-06-01

    Virgibacillus sp. SK37 exhibited high extracellular proteolytic activity in skim milk broth containing 10% NaCl. Optimum conditions of the crude proteinase were at pH 8.0 and 65 degrees C. The proteinase was strongly inhibited by phenylmethanesulfonyl fluoride (PMSF) and preferably hydrolyzed Suc-Ala-Ala-Pro-Phe-AMC, suggesting the serine proteinase with a subtilisin-like characteristic. Proteolytic activity increased with NaCl concentration up to 20%. Ca(2+) activated the enzyme activity but reduced enzyme stability at 65 degrees C. Several proteinases with dominant molecular mass (MW) of 81, 67, 63, 50, 38, and 18 kDa were detected on native-polyacrylamide gel electrophoresis (native-PAGE) activity staining in the absence and presence of 25% NaCl. These results demonstrated that Virgibacillus sp. SK37 produced salt-activated extracellular proteinases. Virgibacillus sp. SK37 could be a promising strain for starter culture development used in fish sauce fermentation. PMID:17995713

  4. Leishmania amazonensis: characterization of an ouabain-insensitive Na+-ATPase activity.

    PubMed

    de Almeida-Amaral, Elmo Eduardo; Caruso-Neves, Celso; Pires, Vanessa Maria Pereira; Meyer-Fernandes, José Roberto

    2008-02-01

    We characterized ouabain-insensitive Na+-ATPase activity present in the plasma membrane of Leishmania amazonensis and investigated its possible role in the growth of the parasite. An increase in Na+ concentration in the presence of 1mM ouabain, increased the ATPase activity with a V(max) of 154.1+/-13.5nmol Pi x h(-1) x mg(-1) and a K0.5 of 28.9+/-7.7mM. Furosemide and sodium orthovanadate inhibited the Na+-stimulated ATPase activity with an IC(50) of 270microM and 0.10microM, respectively. Furosemide inhibited the growth of L. amazonensis after 48h incubation, with maximal effect after 96h. The IC50 for furosemide was 840. On the other hand, ouabain (1mM) did not change the growth of the parasite. Taken together, these results show that L. amazonensis expresses a P-type, ouabain-insensitive Na+-ATPase that could be involved with the growth of the parasite. PMID:17825292

  5. Ileal apical Na+-dependent bile acid transporter ASBT is upregulated in rats with diabetes mellitus induced by low doses of streptozotocin.

    PubMed

    Annaba, Fadi; Ma, Ke; Kumar, Pradeep; Dudeja, Amish K; Kineman, Rhonda D; Shneider, Benjamin L; Saksena, Seema; Gill, Ravinder K; Alrefai, Waddah A

    2010-10-01

    Increased intestinal bile acid absorption and expansion of the bile acid pool has been implicated in the hypercholesterolemia associated with diabetes mellitus. However, the molecular basis of the increase in bile acid absorption in diabetes mellitus is not fully understood. The ileal apical Na(+)-dependent bile acid transporter (ASBT) is primarily responsible for active reabsorption of the majority of bile acids. Current studies were designed to investigate the modulation of ASBT function and expression in streptozotocin (STZ)-induced diabetes mellitus in rats and to examine the effect of insulin on rat ASBT promoter by insulin. Diabetes mellitus was induced in Sprague-Dawley rats by intraperitoneal injection of low doses of STZ (20 mg/kg body wt) on five consecutive days. Human insulin (10 U/day) was given to a group of diabetic rats for 3 days before euthanasia. RNA and protein were extracted from mucosa isolated from the small intestine and ASBT expression was assessed by real-time quantitative RT-PCR and Western blotting. Our data showed that ASBT mRNA and protein expression were significantly elevated in diabetic rats. Insulin treatment of diabetic rats reversed the increase in ASBT protein expression to control levels. Consistently, ileal Na(+)-dependent [(3)H]taurocholic uptake in isolated intestinal epithelial cells was significantly increased in diabetic rats. In vitro studies utilizing intestinal epithelial Caco-2 cells demonstrated that ASBT expression and promoter activity were significantly decreased by insulin. These studies demonstrated that insulin directly influences ASBT expression and promoter activity and that ASBT function and expression are increased in rats with STZ-induced diabetes mellitus. The increase in ASBT expression may contribute to disturbances in cholesterol homeostasis associated with diabetes mellitus.

  6. Mechanism of Na+-dependent citrate transport from the structure of an asymmetrical CitS dimer

    PubMed Central

    Wöhlert, David; Grötzinger, Maria J; Kühlbrandt, Werner; Yildiz, Özkan

    2015-01-01

    The common human pathogen Salmonella enterica takes up citrate as a nutrient via the sodium symporter SeCitS. Uniquely, our 2.5 Å x-ray structure of the SeCitS dimer shows three different conformations of the active protomer. One protomer is in the outside-facing state. Two are in different inside-facing states. All three states resolve the substrates in their respective binding environments. Together with comprehensive functional studies on reconstituted proteoliposomes, the structures explain the transport mechanism in detail. Our results indicate a six-step process, with a rigid-body 31° rotation of a helix bundle that translocates the bound substrates by 16 Å across the membrane. Similar transport mechanisms may apply to a wide variety of related and unrelated secondary transporters, including important drug targets. DOI: http://dx.doi.org/10.7554/eLife.09375.001 PMID:26636752

  7. Active transport of vesicles in neurons is modulated by mechanical tension.

    PubMed

    Ahmed, Wylie W; Saif, Taher A

    2014-03-27

    Effective intracellular transport of proteins and organelles is critical in cells, and is especially important for ensuring proper neuron functionality. In neurons, most proteins are synthesized in the cell body and must be transported through thin structures over long distances where normal diffusion is insufficient. Neurons transport subcellular cargo along axons and neurites through a stochastic interplay of active and passive transport. Mechanical tension is critical in maintaining proper function in neurons, but its role in transport is not well understood. To this end, we investigate the active and passive transport of vesicles in Aplysia neurons while changing neurite tension via applied strain, and quantify the resulting dynamics. We found that tension in neurons modulates active transport of vesicles by increasing the probability of active motion, effective diffusivity, and induces a retrograde bias. We show that mechanical tension modulates active transport processes in neurons and that external forces can couple to internal (subcellular) forces and change the overall transport dynamics.

  8. Oscillations and multiple steady states in active membrane transport models.

    PubMed

    Vieira, F M; Bisch, P M

    1994-01-01

    The dynamic behavior of some non-linear extensions of the six-state alternating access model for active membrane transport is investigated. We use stoichio-metric network analysis to study the stability of steady states. The bifurcation analysis has been done through standard numerical methods. For the usual six-state model we have proved that there is only one steady state, which is globally asymptotically stable. When we added an autocatalytic step we found self-oscillations. For the competition between a monomer cycle and a dimer cycle, with steps of dimer formation, we have also found self-oscillations. We have also studied models involving the formation of a complex with other molecules. The addition of two steps for formation of a complex of the monomer with another molecule does not alter either the number or the stability of steady states of the basic six-state model. The model which combines the formation of a complex with an autocatalytic step shows both self-oscillations and multiple steady states. The results lead us to conclude that oscillations could be produced by active membrane transport systems if the transport cycle contains a sufficiently large number of steps (six in the present case) and is coupled to at least one autocatalytic reaction,. Oscillations are also predicted when the monomer cycle is coupled to a dimer cycle. In fact, the autocatalytic reaction can be seen as a simplification of the model involving competition between monomer and dimer cycles, which seems to be a more realistic description of biological systems. A self-regulation mechanism of the pumps, related to the multiple stationary states, is expected only for a combined effect of autocatalysis and formation of complexes with other molecules. Within the six-state model this model also leads to oscillation.

  9. Socioeconomic and regional differences in active transportation in Brazil

    PubMed Central

    de Sá, Thiago Hérick; Pereira, Rafael Henrique Moraes; Duran, Ana Clara; Monteiro, Carlos Augusto

    2016-01-01

    ABSTRACT OBJECTIVE To present national estimates regarding walking or cycling for commuting in Brazil and in 10 metropolitan regions. METHODS By using data from the Health section of 2008’s Pesquisa Nacional por Amostra de Domicílio (Brazil’s National Household Sample Survey), we estimated how often employed people walk or cycle to work, disaggregating our results by sex, age range, education level, household monthly income per capita, urban or rural address, metropolitan regions, and macro-regions in Brazil. Furthermore, we estimated the distribution of this same frequency according to quintiles of household monthly income per capita in each metropolitan region of the country. RESULTS A third of the employed men and women walk or cycle from home to work in Brazil. For both sexes, this share decreases as income and education levels rise, and it is higher among younger individuals, especially among those living in rural areas and in the Northeast region of the country. Depending on the metropolitan region, the practice of active transportation is two to five times more frequent among low-income individuals than among high-income individuals. CONCLUSIONS Walking or cycling to work in Brazil is most frequent among low-income individuals and the ones living in less economically developed areas. Active transportation evaluation in Brazil provides important information for public health and urban mobility policy-making PMID:27355465

  10. The influence of active transport systems on morphine -6-glucuronide transport in MDCKII and MDCK-PGP cells

    PubMed Central

    Sattari, M.; Routledge, PA.; Mashayekhi, SO.

    2011-01-01

    Background and the purpose of the study Morphine-6-glucuronide (M6G) is a potent metabolite of morphine which has high penetration into the brain despite its high polarity, which could be the result of an active transport system involved in M6G transport through blood brain barrier. Examples of such transporters are p-glycoprotein (PGP), probenecid-sensitive transport mechanism, multidrug resistance related protein 1-3, the organic anion transporter family, and the organic anion transporter polypeptide family. The aim of present study was to elucidate the mechanisms involved in transporting morphine's potent metabolite, M6G. Methods M6G permeability via two cell lines; MDCKII and MDCK-PGP, was compared with that of sucrose. M6G transport was examined in different concentrations and in the presence of inhibitors of different transport systems such as cyclosporine, digoxin and probenecid. M6G concentration was measured using ELISA assay. The method was sensitive, reliable and reproducible. Results The results confirmed that M6G could cross a layer of MDCK II or MDR-PGP cells more than sucrose could. It was also observed that M6G is a PGP transporter substrate. Its permeability was increased by the use of a PGP expressed cell line, and also in the presence of a strong PGP inhibitor. Digoxin related transporters such as Oatp2 may also involved in transport of M6G. M6G seemed to be a glucose transporter 1 substrate, but was not a substrate to probenecid sensitive transporters. Major conclusion It is concluded that different transporters are responsible for M6G transports via different membrane, which could have effects on its pharmacokinetics or pharmacodynamics. PMID:23008686

  11. Bactericidal and Fungicidal Activity in the Gas Phase of Sodium Dichloroisocyanurate (NaDCC).

    PubMed

    Proto, Antonio; Zarrella, Ilaria; Cucciniello, Raffaele; Pironti, Concetta; De Caro, Francesco; Motta, Oriana

    2016-08-01

    Sodium dichloroisocyanurate (NaDCC) is usually employed as a disinfectant for the treatment of water, environmental surfaces and medical equipment principally for its effectiveness as a microbicide agent. In this study, we explore the possibility of a new use for NaDCC by investigating the microbicidal activity of chlorine, which derives from the hydrolysis of NaDCC mediated by air humidity, and by testing its effect on the neutralization of microbes present in domestic waste. NaDCC was inserted in a plastic garbage can where LB agar plates, with different dilutions of a known title of four different microorganisms (Escherichia coli, Staphylococcus aureus, Debaryomyces hansenii and Aspergillus brasiliensis), were weakly inserted. The molecular chlorine (Cl2) levels present in the garbage can were quantified using an iodometric titration. The gas emitted in the garbage can presented a strong microbicide effect, inhibiting the proliferation of all four microorganisms and for four consecutive weeks, thus showing that NaDCC hydrolysis, mediated by air humidity, is able to ensure the decontamination of restricted environments, avoiding the proliferation of both Gram-positive and Gram-negative bacteria as well as fungi. PMID:27086304

  12. The F130S point mutation in the Arabidopsis high-affinity K+ transporter AtHAK5 increases K+ over Na+ and Cs+ selectivity and confers Na+ and Cs+ tolerance to yeast under heterologous expression

    PubMed Central

    Alemán, Fernando; Caballero, Fernando; Ródenas, Reyes; Rivero, Rosa M.; Martínez, Vicente; Rubio, Francisco

    2014-01-01

    Potassium (K+) is an essential macronutrient required for plant growth, development and high yield production of crops. Members of group I of the KT/HAK/KUP family of transporters, such as HAK5, are key components for K+ acquisition by plant roots at low external K+ concentrations. Certain abiotic stress conditions such as salinity or Cs+-polluted soils may jeopardize plant K+ nutrition because HAK5-mediated K+ transport is inhibited by Na+ and Cs+. Here, by screening in yeast a randomly-mutated collection of AtHAK5 transporters, a new mutation in AtHAK5 sequence is identified that greatly increases Na+ tolerance. The single point mutation F130S, affecting an amino acid residue conserved in HAK5 transporters from several species, confers high salt tolerance, as well as Cs+ tolerance. This mutation increases more than 100-fold the affinity of AtHAK5 for K+ and reduces the Ki values for Na+ and Cs+, suggesting that the F130 residue may contribute to the structure of the pore region involved in K+ binding. In addition, this mutation increases the Vmax for K+. All this changes occur without increasing the amount of the AtHAK5 protein in yeast and support the idea that this residue is contributing to shape the selectivity filter of the AtHAK5 transporter. PMID:25228905

  13. Protease-activated receptor-2-mediated inhibition of ion transport in human bronchial epithelial cells.

    PubMed

    Danahay, H; Withey, L; Poll, C T; van de Graaf, S F; Bridges, R J

    2001-06-01

    A cytoprotective role for protease-activated receptor-2 (PAR2) has been suggested in a number of systems including the airway, and to this end, we have studied the role that PARs play in the regulation of airway ion transport, using cultures of normal human bronchial epithelial cells. PAR2 activators, added to the basolateral membrane, caused a transient, Ca2+-dependent increase in short-circuit current (I(sc)), followed by a sustained inhibition of amiloride-sensitive I(sc). These phases corresponded with a transient increase in intracellular Ca2+ concentration and then a transient increase, followed by decrease, in basolateral K+ permeability. After PAR2 activation and the addition of amiloride, the forskolin-stimulated increase in I(sc) was also attenuated. By contrast, PAR2 activators added to the apical surface of the epithelia or PAR1 activators added to both the apical and basolateral surfaces were without effect. PAR2 may, therefore, play a role in the airway, regulating Na+ absorption and anion secretion, processes that are central to the control of airway surface liquid volume and composition.

  14. Examining Changes in Radioxenon Isotope Activity Ratios during Subsurface Transport

    NASA Astrophysics Data System (ADS)

    Annewandter, R.

    2013-12-01

    The Non-Proliferation Experiment (NPE) has demonstrated and modelled the usefulness of barometric pumping induced soil gas sampling during On-Site inspections. Gas transport has been widely studied with different numerical codes. However, gas transport of all radioxenons in the post-detonation regime and their possible fractionation is still neglected in the open literature. Atmospheric concentrations of the radioxenons Xe-135, Xe-133m, Xe-133 and Xe-131m can be used to discriminate between civilian releases (nuclear power plants or medical isotope facilities), and nuclear explosion sources. It is based on the isotopic activity ratio method. Yet it is not clear whether subsurface migration of the radioxenons, with eventual release into the atmosphere, can affect the activity ratios due to fractionation. Fractionation can be caused by different diffusivities due to mass differences between the radioxenons. A previous study showed surface arrival time of a chemically inert gaseous tracer is affected by its diffusivity. They observed detectable amount for SF6 50 days after detonation and 375 days for He-3. They predict 50 and 80 days for Xe-133 and Ar-37 respectively. Cyclical changes in atmospheric pressure can drive subsurface gas transport. This barometric pumping phenomenon causes an oscillatoric flow in upward trending fractures which, combined with diffusion into the porous matrix, leads to a net transport of gaseous components - a ratcheting effect. We use a general purpose reservoir simulator (Complex System Modelling Platform, CSMP++) which has been applied in a range of fields such as deep geothermal systems, three-phase black oil simulations , fracture propagation in fractured, porous media, Navier-Stokes pore-scale modelling among others. It is specifically designed to account for structurally complex geologic situation of fractured, porous media. Parabolic differential equations are solved by a continuous Galerkin finite-element method, hyperbolic

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

    PubMed

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

    2013-08-01

    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.

  16. Reversible emission evolution from Ag activated zeolite Na-A upon dehydration/hydration

    SciTech Connect

    Lin, Hui E-mail: fujii@eedept.kobe-u.ac.jp; Imakita, Kenji; Fujii, Minoru E-mail: fujii@eedept.kobe-u.ac.jp

    2014-11-24

    Reversible emission evolution of thermally treated Ag activated zeolite Na-A upon dehydration/hydration in vacuum/water vapor was observed. The phenomenon was observed even for the sample with low Ag{sup +}-Na{sup +} exchanging (8.3%), indicating that the emission from Ag activated zeolites may not come from Ag clusters while from the surrounding coordinated Ag{sup +} ions or Ag{sup 0} atoms. It was disclosed that the characteristic yellow-green emission at ∼560 ± 15 nm is strongly associated with the coordinating water molecules to the Ag{sup +} ions or Ag{sup 0} atoms, which is clear evidence for that the efficient emission from Ag activated zeolites may not originate from the quantum confinement effect.

  17. The thermophysical and transport properties of eutectic NaK near room temperature

    SciTech Connect

    O'Donnell, W.J.; Papanikolaou, P.G.; Reed, C.B.

    1989-02-01

    The purpose of this report is to compile recommended room temperature thermophysical properties of NaK/sub 78/. The report was prepared to provide a single unified collection of property values for the eutectic sodium-potassium alloy. These properties include density, kinematic and absolute viscosities, thermal conductivity, specific heat, electrical resistivity, electrical conductivity, Prandtl number, and thermal diffusivity. Each section of the report contains a completely referenced property that focuses in the 0--80/degree/C temperature range. All available data for each property have been taken from original publications. The individual sections are organized following a specific outline, considering: discussion of experimental methods, discussion of sources and error, discussion of each reference, tabular presentation of all available data, graphical presentation of the data, recommendations, tabular presentation of recommended values, an equation to calculate recommended values, and a graphical presentation of the recommended curve (0--80/degree/C) generated from the above equation. Also included are experimental methods, whether the references included equations to fit the data, and whether or not these references were primary sources. 26 refs., 12 figs., 14 tabs.

  18. NBCe1 as a Model Carrier for Understanding the Structure-Function Properties of Na+-Coupled SLC4 Transporters in Health and Disease

    PubMed Central

    Kurtz, Ira

    2014-01-01

    SLC4 transporters are membrane proteins that in general mediate the coupled transport of bicarbonate (carbonate) and share amino acid sequence homology. These proteins differ as to whether they also transport Na+ and/or Cl−, in addition to their charge transport stoichiometry, membrane targeting, substrate affinities, developmental expression, regulatory motifs, and protein-protein interactions. These differences account in part for the fact that functionally, SLC4 transporters have various physiological roles in mammals including transepithelial bicarbonate transport, intracellular pH regulation, transport of Na+ and/or Cl−, and possibly water. Bicarbonate transport is not unique to the SLC4 family since the structurally unrelated SLC26 family has at least three proteins that mediate Cl−-HCO3− exchange. The present review focuses on the first of the sodium-dependent SLC4 transporters that was identified whose structure has been most extensively studied: the electrogenic Na+-base cotransporter NBCe1. Mutations in NBCe1 cause proximal renal tubular acidosis (pRTA) with neurologic and ophthalmologic extrarenal manifestations. Recent studies have characterized important structure-function properties of the transporter and how they are perturbed as a result of mutations that cause pRTA. It has become increasingly apparent that the structure of NBCe1 differs in several key features from the SLC4 Cl−-HCO3− exchanger AE1 whose structural properties have been well-studied. In this review, the structure-function properties and regulation of NBCe1 will be highlighted and its role in health and disease will be reviewed in detail. PMID:24515290

  19. Na+/H+ exchanger in regulation of platelet activation and paradoxical effects of cariporide

    PubMed Central

    Chang, He Benny; Gao, Xin; Nepomuceno, Rachel; Hu, Shaoshan; Sun, Dandan

    2015-01-01

    Platelets are anucleated cell fragments derived from mature megakaryocytes and function in hemostasis when the endothelium is injured. Hemostasis involving platelets can be divided into four phases: adhesion, activation, secretion, and aggregation. Platelet activation requires a rise in intracellular Ca2+ concentrations and results in both a morphological change and the secretion of platelet granule contents. Na+/H+ exchanger isoform 1 (NHE1) regulates the intracellular pH (pHi) and the volume of platelets. In addition, NHE1 plays a large role in platelet activation. Thrombus generation involves NHE1 activation and an increase in [Ca2+]i, which results from NHE1-mediated Na+ overload and the reversal of the Na+/Ca2+ exchanger. Cariporide (HOE-642), a potent NHE1 inhibitor, has inhibitory effects on the degranulation of human platelets, the formation of platelet–leukocyte-aggregates, and the activation of the GPIIb/IIIa receptor (PAC-1). However, despite the demonstrated protection of myocardial infarction as mediated by cariporide in patients undergoing coronary artery bypass graft surgery, the EXPEDITION clinical trial revealed that cariporide treatment increased mortality due to thromboembolic stroke. These findings suggest that a better understanding of NHE1 and its effect on platelet function and procoagulant factor regulation is warranted in order to develop therapies using NHE inhibitors. PMID:25595121

  20. Na+ -K+ pump activity in rat peritoneal mast cells: inhibition by extracellular calcium.

    PubMed Central

    Knudsen, T.; Johansen, T.

    1989-01-01

    1. Pure populations of rat peritoneal mast cells were used to study cellular potassium uptake. The radioactive potassium analogue, 86rubidium, was used as a tracer for potassium for measurements of the activity of the cellular potassium uptake process. 2. The ouabain-sensitive and the ouabain-resistant potassium (86rubidium) uptake of mast cells incubated in the presence of calcium, 1 mmol l-1, were very low, 52 and 147 pmol per 10(6) cells min-1. 3. Calcium-deprivation of the cells uncovered a large capacity ouabain-sensitive potassium (86rubidium) uptake mechanism. The activity of the uptake mechanism was decreased by reintroduction of calcium into the cell suspension, and it was dependent on cellular energy metabolism, temperature and pH. 4. The potassium (86rubidium) uptake of mast cells incubated in a calcium-free medium occurs through an active and ouabain-sensitive mechanism that has the nature of an enzyme, and it is mediated by the Na+ -K+ pump located in the plasma membrane. It is demonstrated that the activity of the Na+ -K+ pump mechanism is inhibited by low concentrations of extracellular calcium (0.1-1.2 mmol l-1). The possibility is discussed that calcium-deprivation may increase the pump activity by increasing the permeability of the plasma membrane for Na+. PMID:2743077

  1. Na⁺ transport in the normal and failing heart - remember the balance.

    PubMed

    Despa, Sanda; Bers, Donald M

    2013-08-01

    In the heart, intracellular Na(+) concentration ([Na(+)]i) is a key modulator of Ca(2+) cycling, contractility and cardiac myocyte metabolism. Several Na(+) transporters are electrogenic, thus they both contribute to shaping the cardiac action potential and at the same time are affected by it. [Na(+)]i is controlled by the balance between Na(+) influx through various pathways, including the Na(+)/Ca(2+) exchanger and Na(+) channels, and Na(+) extrusion via the Na(+)/K(+)-ATPase. [Na(+)]i is elevated in HF due to a combination of increased entry through Na(+) channels and/or Na(+)/H(+) exchanger and reduced activity of the Na(+)/K(+)-ATPase. Here we review the major Na(+) transport pathways in cardiac myocytes and how they participate in regulating [Na(+)]i in normal and failing hearts. This article is part of a Special Issue entitled "Na(+) Regulation in Cardiac Myocytes."

  2. Structural lipid changes and Na(+)/K(+)-ATPase activity of gill cells' basolateral membranes during saltwater acclimation in sea lamprey (Petromyzon marinus, L.) juveniles.

    PubMed

    Lança, Maria João; Machado, Maria; Ferreira, Ana Filipa; Quintella, Bernardo Ruivo; de Almeida, Pedro Raposo

    2015-11-01

    Seawater acclimation is a critical period for anadromous species and a process yet to be understood in lampreys. Considering that changes in lipid composition of the gill cells' basolateral membranes may disrupt the major transporter Na(+)K(+)-ATPase, the goal of this study was to detect changes at this level during juvenile sea lamprey seawater acclimation. The results showed that saltwater acclimation has a direct effect on the fatty acid composition of gill cells basolateral membrane's phospholipids. When held in full-strength seawater, the fatty acid profile of basolateral membrane's phospholipids suffered a restructure by increasing either saturation or the ratio between oleic acid and eicosapentaenoic acid. Simultaneously, the activity of Na(+)K(+)-ATPase revealed a significant and positive correlation with basolateral membrane's cholesterol content in the presence of highest salinity. Our results pointed out for lipid adjustments involving the functional transporter present on the gill cell basolateral membranes to ensure the role played by branchial Na(+)K(+)-ATPase in ion transport during saltwater acclimation process. The responses observed contributed to the strategy adopted by gill cell's basolateral membranes to compensate for osmotic and ionic stressors, to ensure the success of the process of seawater acclimation associated with the downstream trophic migration of juvenile sea lamprey.

  3. Role of H{sub 2}O{sub 2} on the kinetics of low-affinity high-capacity Na{sup +}-dependent alanine transport in SHR proximal tubular epithelial cells

    SciTech Connect

    Pinto, Vanda; Pinho, Maria Joao; Jose, Pedro A.; Soares-da-Silva, Patricio

    2010-07-30

    Research highlights: {yields} H{sub 2}O{sub 2} in excess is required for the presence of a low-affinity high-capacity component for the Na{sup +}-dependent [{sup 14}C]-L-alanine uptake in SHR PTE cells only. {yields} It is suggested that Na{sup +} binding in renal ASCT2 may be regulated by ROS in SHR PTE cells. -- Abstract: The presence of high and low sodium affinity states for the Na{sup +}-dependent [{sup 14}C]-L-alanine uptake in immortalized renal proximal tubular epithelial (PTE) cells was previously reported (Am. J. Physiol. 293 (2007) R538-R547). This study evaluated the role of H{sub 2}O{sub 2} on the Na{sup +}-dependent [{sup 14}C]-L-alanine uptake of ASCT2 in immortalized renal PTE cells from Wistar Kyoto rat (WKY) and spontaneously hypertensive rat (SHR). Na{sup +} dependence of [{sup 14}C]-L-alanine uptake was investigated replacing NaCl with an equimolar concentration of choline chloride in vehicle- and apocynin-treated cells. Na{sup +} removal from the uptake solution abolished transport activity in both WKY and SHR PTE cells. Decreases in H{sub 2}O{sub 2} levels in the extracellular medium significantly reduced Na{sup +}-K{sub m} and V{sub max} values of the low-affinity high-capacity component in SHR PTE cells, with no effect on the high-affinity low-capacity state of the Na{sup +}-dependent [{sup 14}C]-L-alanine uptake. After removal of apocynin from the culture medium, H{sub 2}O{sub 2} levels returned to basal values within 1 to 3 h in both WKY and SHR PTE cells and these were found stable for the next 24 h. Under these experimental conditions, the Na{sup +}-K{sub m} and V{sub max} of the high-affinity low-capacity state were unaffected and the low-affinity high-capacity component remained significantly decreased 1 day but not 4 days after apocynin removal. In conclusion, H{sub 2}O{sub 2} in excess is required for the presence of a low-affinity high-capacity component for the Na{sup +}-dependent [{sup 14}C]-L-alanine uptake in SHR PTE cells only

  4. Proton and cation transport activity of the M2 proton channel from influenza A virus.

    PubMed

    Leiding, Thom; Wang, Jun; Martinsson, Jonas; DeGrado, William F; Arsköld, Sindra Peterson

    2010-08-31

    The M2 protein is a small, single-span transmembrane (TM) protein from the influenza A virus. This virus enters cells via endosomes; as the endosomes mature and become more acidic M2 facilitates proton transport into the viral interior, thereby disrupting matrix protein/RNA interactions required for infectivity. A mystery has been how protons can accumulate in the viral interior without developing a large electrical potential that impedes further inward proton translocation. Progress in addressing this question has been limited by the availability of robust methods of unidirectional insertion of the protein into virus-like vesicles. Using an optimized procedure for reconstitution, we show that M2 has antiporter-like activity, facilitating K(+) or Na(+) efflux when protons flow down a concentration gradient into the vesicles. Cation efflux is very small except under conditions mimicking those encountered by the endosomally entrapped virus, in which protons are flowing through the channel. This proton/cation exchange function is consistent with the known high proton selectivity of the channel. Thus, M2 acts as a proton uniporter that occasionally allows K(+) to flow to maintain electrical neutrality. Remarkably, as the pH inside M2-containing vesicles (pH(in)) decreases, the proton channel activity of M2 is inhibited, but its cation transport activity is activated. This reciprocal inhibition of proton flux and activation of cation flux with decreasing pH(in) first allows accumulation of protons in the early stages of acidification, then trapping of protons within the virus when low pH(in) is achieved.

  5. Expression of renal Oat5 and NaDC1 transporters in rats with acute biliary obstruction

    PubMed Central

    Brandoni, Anabel; Torres, Adriana Mónica

    2015-01-01

    AIM: To examine renal expression of organic anion transporter 5 (Oat5) and sodium-dicarboxylate cotransporter 1 (NaDC1), and excretion of citrate in rats with acute extrahepatic cholestasis. METHODS: Obstructive jaundice was induced in rats by double ligation and division of the common bile duct (BDL group). Controls underwent sham operation that consisted of exposure, but not ligation, of the common bile duct (Sham group). Studies were performed 21 h after surgery. During this period, animals were maintained in metabolic cages in order to collect urine. The urinary volume was determined by gravimetry. The day of the experiment, blood samples were withdrawn and used to measure total and direct bilirubin as indicative parameters of hepatic function. Serum and urine samples were used for biochemical determinations. Immunoblotting for Oat5 and NaDC1 were performed in renal homogenates and brush border membranes from Sham and BDL rats. Immunohistochemistry studies were performed in kidneys from both experimental groups. Total RNA was extracted from rat renal tissue in order to perform reverse transcription polymerase chain reaction. Another set of experimental animals were used to evaluate medullar renal blood flow (mRBF) using fluorescent microspheres. RESULTS: Total and direct bilirubin levels were significantly higher in BDL animals, attesting to the adequacy of biliary obstruction. An important increase in mRBF was determined in BDL group (Sham: 0.53 ± 0.12 mL/min per 100 g body weight vs BDL: 1.58 ± 0.24 mL/min per 100 g body weight, P < 0.05). An increase in the urinary volume was observed in BDL animals. An important decrease in urinary levels of citrate was seen in BDL group. Besides, a decrease in urinary citrate excretion (Sham: 0.53 ± 0.11 g/g creatinine vs BDL: 0.07 ± 0.02 g/g creatinine, P < 0.05) and an increase in urinary excretion of H+ (Sham: 0.082 ± 0.03 μmol/g creatinine vs BDL: 0.21 ± 0.04 μmol/g creatinine, P < 0.05) were observed in BDL

  6. Two independent evolutionary routes to Na+/H+ cotransport function in membrane pyrophosphatases.

    PubMed

    Nordbo, Erika; Luoto, Heidi H; Baykov, Alexander A; Lahti, Reijo; Malinen, Anssi M

    2016-10-01

    Membrane-bound pyrophosphatases (mPPases) hydrolyze pyrophosphate (PPi) to transport H(+), Na(+) or both and help organisms to cope with stress conditions, such as high salinity or limiting nutrients. Recent elucidation of mPPase structure and identification of subfamilies that have fully or partially switched from Na(+) to H(+) pumping have established mPPases as versatile models for studying the principles governing the mechanism, specificity and evolution of cation transporters. In the present study, we constructed an accurate phylogenetic map of the interface of Na(+)-transporting PPases (Na(+)-PPases) and Na(+)- and H(+)-transporting PPases (Na(+),H(+)-PPases), which guided our experimental exploration of the variations in PPi hydrolysis and ion transport activities during evolution. Surprisingly, we identified two mPPase lineages that independently acquired physiologically significant Na(+) and H(+) cotransport function. Na(+),H(+)-PPases of the first lineage transport H(+) over an extended [Na(+)] range, but progressively lose H(+) transport efficiency at high [Na(+)]. In contrast, H(+)-transport by Na(+),H(+)-PPases of the second lineage is not inhibited by up to 100 mM Na(+) With the identification of Na(+),H(+)-PPase subtypes, the mPPases protein superfamily appears as a continuum, ranging from monospecific Na(+) transporters to transporters with tunable levels of Na(+) and H(+) cotransport and further to monospecific H(+) transporters. Our results lend credence to the concept that Na(+) and H(+) are transported by similar mechanisms, allowing the relative efficiencies of Na(+) and H(+) transport to be modulated by minor changes in protein structure during the course of adaptation to a changing environment.

  7. Reliability and Validity of the Transport and Physical Activity Questionnaire (TPAQ) for Assessing Physical Activity Behaviour

    PubMed Central

    Adams, Emma J.; Goad, Mary; Sahlqvist, Shannon; Bull, Fiona C.; Cooper, Ashley R.; Ogilvie, David

    2014-01-01

    Background No current validated survey instrument allows a comprehensive assessment of both physical activity and travel behaviours for use in interdisciplinary research on walking and cycling. This study reports on the test-retest reliability and validity of physical activity measures in the transport and physical activity questionnaire (TPAQ). Methods The TPAQ assesses time spent in different domains of physical activity and using different modes of transport for five journey purposes. Test-retest reliability of eight physical activity summary variables was assessed using intra-class correlation coefficients (ICC) and Kappa scores for continuous and categorical variables respectively. In a separate study, the validity of three survey-reported physical activity summary variables was assessed by computing Spearman correlation coefficients using accelerometer-derived reference measures. The Bland-Altman technique was used to determine the absolute validity of survey-reported time spent in moderate-to-vigorous physical activity (MVPA). Results In the reliability study, ICC for time spent in different domains of physical activity ranged from fair to substantial for walking for transport (ICC = 0.59), cycling for transport (ICC = 0.61), walking for recreation (ICC = 0.48), cycling for recreation (ICC = 0.35), moderate leisure-time physical activity (ICC = 0.47), vigorous leisure-time physical activity (ICC = 0.63), and total physical activity (ICC = 0.56). The proportion of participants estimated to meet physical activity guidelines showed acceptable reliability (k = 0.60). In the validity study, comparison of survey-reported and accelerometer-derived time spent in physical activity showed strong agreement for vigorous physical activity (r = 0.72, p<0.001), fair but non-significant agreement for moderate physical activity (r = 0.24, p = 0.09) and fair agreement for MVPA (r = 0.27, p = 0.05). Bland-Altman analysis

  8. Phosphorylation of the adipose/muscle-type glucose transporter (GLUT4) and its relationship to glucose transport activity.

    PubMed Central

    Schürmann, A; Mieskes, G; Joost, H G

    1992-01-01

    The effects of protein phosphorylation and dephosphorylation on glucose transport activity reconstituted from adipocyte membrane fractions and its relationship to the phosphorylation state of the adipose/muscle-type glucose transporter (GLUT4) were studied. In vitro phosphorylation of membranes in the presence of ATP and protein kinase A produced a stimulation of the reconstituted glucose transport activity in plasma membranes and low-density microsomes (51% and 65% stimulation respectively), provided that the cells had been treated with insulin prior to isolation of the membranes. Conversely, treatment of membrane fractions with alkaline phosphatase produced an inhibition of reconstituted transport activity. However, in vitro phosphorylation catalysed by protein kinase C failed to alter reconstituted glucose transport activity in membrane fractions from both basal and insulin-treated cells. In experiments run under identical conditions, the phosphorylation state of GLUT4 was investigated by immunoprecipitation of glucose transporters from membrane fractions incubated with [32P]ATP and protein kinases A and C. Protein kinase C stimulated a marked phosphate incorporation into GLUT4 in both plasma membranes and low-density microsomes. Protein kinase A, in contrast to its effect on reconstituted glucose transport activity, produced a much smaller phosphorylation of the GLUT4 in plasma membranes than in low-density microsomes. The present data suggest that glucose transport activity can be modified by protein phosphorylation via an insulin-dependent mechanism. However, the phosphorylation of the GLUT4 itself was not correlated with changes in its reconstituted transport activity. Images Fig. 1. Fig. 2. Fig. 3. PMID:1637303

  9. Dissecting the Molecular Mechanism of Nucleotide-Dependent Activation of the KtrAB K+ Transporter

    PubMed Central

    Szollosi, Andras; Vieira-Pires, Ricardo S.; Teixeira-Duarte, Celso M.; Rocha, Rita; Morais-Cabral, João H.

    2016-01-01

    KtrAB belongs to the Trk/Ktr/HKT superfamily of monovalent cation (K+ and Na+) transport proteins that closely resemble K+ channels. These proteins underlie a plethora of cellular functions that are crucial for environmental adaptation in plants, fungi, archaea, and bacteria. The activation mechanism of the Trk/Ktr/HKT proteins remains unknown. It has been shown that ATP stimulates the activity of KtrAB while ADP does not. Here, we present X-ray structural information on the KtrAB complex with bound ADP. A comparison with the KtrAB-ATP structure reveals conformational changes in the ring and in the membrane protein. In combination with a biochemical and functional analysis, we uncover how ligand-dependent changes in the KtrA ring are propagated to the KtrB membrane protein and conclude that, despite their structural similarity, the activation mechanism of KtrAB is markedly different from the activation mechanism of K+ channels. PMID:26771197

  10. Dissecting the Molecular Mechanism of Nucleotide-Dependent Activation of the KtrAB K+ Transporter.

    PubMed

    Szollosi, Andras; Vieira-Pires, Ricardo S; Teixeira-Duarte, Celso M; Rocha, Rita; Morais-Cabral, João H

    2016-01-01

    KtrAB belongs to the Trk/Ktr/HKT superfamily of monovalent cation (K+ and Na+) transport proteins that closely resemble K+ channels. These proteins underlie a plethora of cellular functions that are crucial for environmental adaptation in plants, fungi, archaea, and bacteria. The activation mechanism of the Trk/Ktr/HKT proteins remains unknown. It has been shown that ATP stimulates the activity of KtrAB while ADP does not. Here, we present X-ray structural information on the KtrAB complex with bound ADP. A comparison with the KtrAB-ATP structure reveals conformational changes in the ring and in the membrane protein. In combination with a biochemical and functional analysis, we uncover how ligand-dependent changes in the KtrA ring are propagated to the KtrB membrane protein and conclude that, despite their structural similarity, the activation mechanism of KtrAB is markedly different from the activation mechanism of K+ channels.

  11. Allosteric Regulation of Transport Activity by Heterotrimerization of Arabidopsis Ammonium Transporter Complexes in Vivo[C][W][OA

    PubMed Central

    Yuan, Lixing; Gu, Riliang; Xuan, Yuanhu; Smith-Valle, Erika; Loqué, Dominique; Frommer, Wolf B.; von Wirén, Nicolaus

    2013-01-01

    Ammonium acquisition by plant roots is mediated by AMMONIUM TRANSPORTERs (AMTs), ubiquitous membrane proteins with essential roles in nitrogen nutrition in all organisms. In microbial and plant cells, ammonium transport activity is controlled by ammonium-triggered feedback inhibition to prevent cellular ammonium toxicity. Data from heterologous expression in yeast indicate that oligomerization of plant AMTs is critical for allosteric regulation of transport activity, in which the conserved cytosolic C terminus functions as a trans-activator. Employing the coexpressed transporters AMT1;1 and AMT1;3 from Arabidopsis thaliana as a model, we show here that these two isoforms form functional homo- and heterotrimers in yeast and plant roots and that AMT1;3 carrying a phosphomimic residue in its C terminus regulates both homo- and heterotrimers in a dominant-negative fashion in vivo. 15NH4+ influx studies further indicate that allosteric inhibition represses ammonium transport activity in roots of transgenic Arabidopsis expressing a phosphomimic mutant together with functional AMT1;3 or AMT1;1. Our study demonstrates in planta a regulatory role in transport activity of heterooligomerization of transporter isoforms, which may enhance their versatility for signal exchange in response to environmental triggers. PMID:23463773

  12. Thermally activated charge transport in microbial protein nanowires

    PubMed Central

    Lampa-Pastirk, Sanela; Veazey, Joshua P.; Walsh, Kathleen A.; Feliciano, Gustavo T.; Steidl, Rebecca J.; Tessmer, Stuart H.; Reguera, Gemma

    2016-01-01

    The bacterium Geobacter sulfurreducens requires the expression of conductive protein filaments or pili to respire extracellular electron acceptors such as iron oxides and uranium and to wire electroactive biofilms, but the contribution of the protein fiber to charge transport has remained elusive. Here we demonstrate efficient long-range charge transport along individual pili purified free of metal and redox organic cofactors at rates high enough to satisfy the respiratory rates of the cell. Carrier characteristics were within the orders reported for organic semiconductors (mobility) and inorganic nanowires (concentration), and resistivity was within the lower ranges reported for moderately doped silicon nanowires. However, the pilus conductance and the carrier mobility decreased when one of the tyrosines of the predicted axial multistep hopping path was replaced with an alanine. Furthermore, low temperature scanning tunneling microscopy demonstrated the thermal dependence of the differential conductance at the low voltages that operate in biological systems. The results thus provide evidence for thermally activated multistep hopping as the mechanism that allows Geobacter pili to function as protein nanowires between the cell and extracellular electron acceptors. PMID:27009596

  13. Thermally activated charge transport in microbial protein nanowires.

    PubMed

    Lampa-Pastirk, Sanela; Veazey, Joshua P; Walsh, Kathleen A; Feliciano, Gustavo T; Steidl, Rebecca J; Tessmer, Stuart H; Reguera, Gemma

    2016-01-01

    The bacterium Geobacter sulfurreducens requires the expression of conductive protein filaments or pili to respire extracellular electron acceptors such as iron oxides and uranium and to wire electroactive biofilms, but the contribution of the protein fiber to charge transport has remained elusive. Here we demonstrate efficient long-range charge transport along individual pili purified free of metal and redox organic cofactors at rates high enough to satisfy the respiratory rates of the cell. Carrier characteristics were within the orders reported for organic semiconductors (mobility) and inorganic nanowires (concentration), and resistivity was within the lower ranges reported for moderately doped silicon nanowires. However, the pilus conductance and the carrier mobility decreased when one of the tyrosines of the predicted axial multistep hopping path was replaced with an alanine. Furthermore, low temperature scanning tunneling microscopy demonstrated the thermal dependence of the differential conductance at the low voltages that operate in biological systems. The results thus provide evidence for thermally activated multistep hopping as the mechanism that allows Geobacter pili to function as protein nanowires between the cell and extracellular electron acceptors. PMID:27009596

  14. L-Cysteine and glutathione restore the reduction of rat hippocampal Na+, K+-ATPase activity induced by aspartame metabolites.

    PubMed

    Simintzi, Irene; Schulpis, Kleopatra H; Angelogianni, Panagoula; Liapi, Charis; Tsakiris, Stylianos

    2007-07-31

    Studies have implicated aspartame (ASP) ingestion in neurological problems. The aim of this study was to evaluate hippocampal Na(+),K(+)-ATPase and Mg(2+)-ATPase activities after incubation with ASP or each of ASP metabolites, phenylalanine (Phe), methanol (MeOH) and aspartic acid (asp) separately. Suckling rat hippocampal homogenates or pure Na(+),K(+)-ATPase were incubated with ASP metabolites. Na(+),K(+)-ATPase and Mg(2+)-ATPase activities were measured spectrophotometrically. Incubation of hippocampal or pure Na(+),K(+)-ATPase with ASP concentrations (expected in the cerebrospinal fluid (CSF)) after ASP consumption of 34, 150 or 200mg/kg resulted in hippocampal enzyme activity reduction of 26%, 50% or 59%, respectively, whereas pure enzyme was remarkably stimulated. Moreover, incubation with hippocampal homogenate of each one of the corresponding in the CSF ASP metabolites related to the intake of common, high/abuse doses of the sweetener, inhibited Na(+),K(+)-ATPase, while pure enzyme was activated. Hippocampal Mg(2+)-ATPase remained unaltered. Addition of l-cysteine (cys) or reduced glutathione (GSH) in ASP mixtures, related with high/toxic doses of the sweetener, completely or partially restored the inactivated membrane Na(+),K(+)-ATPase, whereas the activated pure enzyme activity returned to normal. CSF concentrations of ASP metabolites related to common, abuse/toxic doses of the additive significantly reduced rat hippocampal Na(+),K(+)-ATPase activity, whereas pure enzyme was activated. Cys or GSH completely or partially restored both enzyme activities.

  15. Physical Activity Energy Expenditure in Dutch Adolescents: Contribution of Active Transport to School, Physical Education, and Leisure Time Activities

    ERIC Educational Resources Information Center

    Slingerland, Menno; Borghouts, Lars B.; Hesselink, Matthijs K. C.

    2012-01-01

    Background: Detailed knowledge about physical activity energy expenditure (PAEE) can guide the development of school interventions aimed at reducing overweight in adolescents. However, relevant components of PAEE have never been objectively quantified in this population. This study investigated the contribution of active transport to and from…

  16. Serotonin transporter genotype modulates amygdala activity during mood regulation

    PubMed Central

    Rao, Hengyi; Wang, Jiongjiong; Detre, John A.; Breland, Jessica; Sankoorikal, Geena Mary V.; Brodkin, Edward S.; Farah, Martha J.

    2010-01-01

    Recent studies have implicated the short allele of the serotonin transporter-linked polymorphic region (5-HTTLPR) in depression vulnerability, particularly in the context of stress. Several neuroimaging studies have shown that 5-HTTLPR genotype predicts amygdala reactivity to negatively valenced stimuli, suggesting a mechanism whereby the short allele confers depression risk. The current study investigated whether 5-HTTLPR genotype similarly affects neural activity during an induced sad mood and during recovery from sad mood. Participants were 15 homozygous short (S) and 15 homozygous long (L) individuals. Regional cerebral blood flow was measured with perfusion functional magnetic resonance imaging during four scanning blocks: baseline, sad mood, mood recovery and following return to baseline. Comparing mood recovery to baseline, both whole brain analyses and template-based region-of-interest analyses revealed greater amygdala activity for the S vs the L-group. There were no significant amygdala differences found during the induced sad mood. These results demonstrate the effect of the S allele on amygdala activity during intentional mood regulation and suggest that amygdala hyperactivity during recovery from a sad mood may be one mechanism by which the S allele confers depression risk. PMID:19858108

  17. Molecular simulation of thermodynamic and transport properties for the H{sub 2}O+NaCl system

    SciTech Connect

    Orozco, Gustavo A.; Jiang, Hao; Panagiotopoulos, Athanassios Z.; Moultos, Othonas A.; Economou, Ioannis G.

    2014-12-21

    Molecular dynamics and Monte Carlo simulations have been carried out to obtain thermodynamic and transport properties of the binary mixture H{sub 2}O+NaCl at temperatures from T = 298 to 473 K. In particular, vapor pressures, liquid densities, viscosities, and vapor-liquid interfacial tensions have been obtained as functions of pressure and salt concentration. Several previously proposed fixed-point-charge models that include either Lennard-Jones (LJ) 12-6 or exponential-6 (Exp6) functional forms to describe non-Coulombic interactions were studied. In particular, for water we used the SPC and SPC/E (LJ) models in their rigid forms, a semiflexible version of the SPC/E (LJ) model, and the Errington-Panagiotopoulos Exp6 model; for NaCl, we used the Smith-Dang and Joung-Cheatham (LJ) parameterizations as well as the Tosi-Fumi (Exp6) model. While none of the model combinations are able to reproduce simultaneously all target properties, vapor pressures are well represented using the SPC plus Joung-Cheathem model combination, and all LJ models do well for the liquid density, with the semiflexible SPC/E plus Joung-Cheatham combination being the most accurate. For viscosities, the combination of rigid SPC/E plus Smith-Dang is the best alternative. For interfacial tensions, the combination of the semiflexible SPC/E plus Smith-Dang or Joung-Cheatham gives the best results. Inclusion of water flexibility improves the mixture densities and interfacial tensions, at the cost of larger deviations for the vapor pressures and viscosities. The Exp6 water plus Tosi-Fumi salt model combination was found to perform poorly for most of the properties of interest, in particular being unable to describe the experimental trend for the vapor pressure as a function of salt concentration.

  18. The Na+/H+ Exchanger Controls Deoxycholic Acid-Induced Apoptosis by a H+-Activated, Na+-Dependent Ionic Shift in Esophageal Cells

    PubMed Central

    Goldman, Aaron; Chen, HwuDauRw; Khan, Mohammad R.; Roesly, Heather; Hill, Kimberly A.; Shahidullah, Mohammad; Mandal, Amritlal; Delamere, Nicholas A.; Dvorak, Katerina

    2011-01-01

    Apoptosis resistance is a hallmark of cancer cells. Typically, bile acids induce apoptosis. However during gastrointestinal (GI) tumorigenesis the cancer cells develop resistance to bile acid-induced cell death. To understand how bile acids induce apoptosis resistance we first need to identify the molecular pathways that initiate apoptosis in response to bile acid exposure. In this study we examined the mechanism of deoxycholic acid (DCA)-induced apoptosis, specifically the role of Na+/H+ exchanger (NHE) and Na+ influx in esophageal cells. In vitro studies revealed that the exposure of esophageal cells (JH-EsoAd1, CP-A) to DCA (0.2 mM -0.5 mM) caused lysosomal membrane perturbation and transient cytoplasmic acidification. Fluorescence microscopy in conjunction with atomic absorption spectrophotometry demonstrated that this effect on lysosomes correlated with influx of Na+, subsequent loss of intracellular K+, an increase of Ca2+ and apoptosis. However, ethylisopropyl-amiloride (EIPA), a selective inhibitor of NHE, prevented Na+, K+ and Ca2+ changes and caspase 3/7 activation induced by DCA. Ouabain and amphotericin B, two drugs that increase intracellular Na+ levels, induced similar changes as DCA (ion imbalance, caspase3/7 activation). On the contrary, DCA-induced cell death was inhibited by medium with low a Na+ concentrations. In the same experiments, we exposed rat ileum ex-vivo to DCA with or without EIPA. Severe tissue damage and caspase-3 activation was observed after DCA treatment, but EIPA almost fully prevented this response. In summary, NHE-mediated Na+ influx is a critical step leading to DCA-induced apoptosis. Cells tolerate acidification but evade DCA-induced apoptosis if NHE is inhibited. Our data suggests that suppression of NHE by endogenous or exogenous inhibitors may lead to apoptosis resistance during GI tumorigenesis. PMID:21887327

  19. Electric field strength of membrane lipids from vertebrate species: membrane lipid composition and Na+-K+-ATPase molecular activity.

    PubMed

    Starke-Peterkovic, Thomas; Turner, Nigel; Else, Paul L; Clarke, Ronald J

    2005-03-01

    Intramembrane electric field strength is a very likely determinant of the activity of ion-transporting membrane proteins in living cells. In the absence of any transmembrane electrical potential or surface potential, its magnitude is determined by the dipole potential of the membrane's lipid components and their associated water of hydration. Here we have used a fluorometric method to quantify the dipole potential of vesicles formed from lipids extracted from kidney and brain of 11 different animal species from four different vertebrate classes. The dipole potential was compared with the fatty acid composition and with the Na(+)-K(+)-ATPase molecular activity of each preparation. The magnitude of the dipole potential was found to be relatively constant across all animal species, i.e., 236-334 mV for vesicles prepared from the total membrane lipids and 223-256 mV for phospholipids alone. The significantly lower value for phospholipids alone is potentially related to the removal of cholesterol and/or other common soluble lipid molecules from the membrane. Surprisingly, no significant dependence of the dipole potential on fatty acid composition was found. This may, however, be due to concomitant compensatory variations in lipid head group composition. The molecular activity of the Na(+)-K(+)-ATPase was found to increase with increasing dipole potential. The fact that the dipole potential is maintained at a relatively constant value over a wide range of animal species suggests that it may play a fundamental role in ensuring correct ion pump conformation and function within the membrane.

  20. Renal transporter activation during angiotensin-II hypertension is blunted in interferon-γ-/- and interleukin-17A-/- mice.

    PubMed

    Kamat, Nikhil V; Thabet, Salim R; Xiao, Liang; Saleh, Mohamed A; Kirabo, Annet; Madhur, Meena S; Delpire, Eric; Harrison, David G; McDonough, Alicia A

    2015-03-01

    Ample genetic and physiological evidence establishes that renal salt handling is a critical regulator of blood pressure. Studies also establish a role for the immune system, T-cell infiltration, and immune cytokines in hypertension. This study aimed to connect immune cytokines, specifically interferon-γ (IFN-γ) and interleukin-17A (IL-17A), to sodium transporter regulation in the kidney during angiotensin-II (Ang-II) hypertension. C57BL/6J (wild-type) mice responded to Ang-II infusion (490 ng/kg per minute, 2 weeks) with a rise in blood pressure (170 mm Hg) and a significant decrease in the rate of excretion of a saline challenge. In comparison, mice that lacked the ability to produce either IFN-γ (IFN-γ(-/-)) or IL-17A (IL-17A(-/-)) exhibited a blunted rise in blood pressure (<150 mm Hg), and both the genotypes maintained baseline diuretic and natriuretic responses to a saline challenge. Along the distal nephron, Ang-II infusion increased abundance of the phosphorylated forms of the Na-K-2Cl cotransporter, Na-Cl cotransporter, and Ste20/SPS-1-related proline-alanine-rich kinase, in both the wild-type and the IL-17A(-/-) but not in IFN-γ(-/-) mice; epithelial Na channel abundance increased similarly in all the 3 genotypes. In the proximal nephron, Ang-II infusion significantly decreased abundance of Na/H-exchanger isoform 3 and the motor myosin VI in IL-17A(-/-) and IFN-γ(-/-), but not in wild-type; the Na-phosphate cotransporter decreased in all the 3 genotypes. Our results suggest that during Ang-II hypertension both IFN-γ and IL-17A production interfere with the pressure natriuretic decrease in proximal tubule sodium transport and that IFN-γ production is necessary to activate distal sodium reabsorption. PMID:25601932

  1. Compromising KCC2 transporter activity enhances the development of continuous seizure activity.

    PubMed

    Kelley, Matthew R; Deeb, Tarek Z; Brandon, Nicholas J; Dunlop, John; Davies, Paul A; Moss, Stephen J

    2016-09-01

    Impaired neuronal inhibition has long been associated with the increased probability of seizure occurrence and heightened seizure severity. Fast synaptic inhibition in the brain is primarily mediated by the type A γ-aminobutyric acid receptors (GABAARs), ligand-gated ion channels that can mediate Cl(-) influx resulting in membrane hyperpolarization and the restriction of neuronal firing. In most adult brain neurons, the K(+)/Cl(-) co-transporter-2 (KCC2) establishes hyperpolarizing GABAergic inhibition by maintaining low [Cl(-)]i. In this study, we sought to understand how decreased KCC2 transport function affects seizure event severity. We impaired KCC2 transport in the 0-Mg(2+) ACSF and 4-aminopyridine in vitro models of epileptiform activity in acute mouse brain slices. Experiments with the selective KCC2 inhibitor VU0463271 demonstrated that reduced KCC2 transport increased the duration of SLEs, resulting in non-terminating discharges of clonic-like activity. We also investigated slices obtained from the KCC2-Ser940Ala (S940A) point-mutant mouse, which has a mutation at a known functional phosphorylation site causing behavioral and cellular deficits under hyperexcitable conditions. We recorded from the entorhinal cortex of S940A mouse brain slices in both 0-Mg(2+) ACSF and 4-aminopyridine, and demonstrated that loss of the S940 residue increased the susceptibility of continuous clonic-like discharges, an in vitro form of status epilepticus. Our experiments revealed KCC2 transport activity is a critical factor in seizure event duration and mechanisms of termination. Our results highlight the need for therapeutic strategies that potentiate KCC2 transport function in order to decrease seizure event severity and prevent the development of status epilepticus. PMID:27108931

  2. Functional demonstration of Na+-K+-2Cl- cotransporter activity in isolated, polarized choroid plexus cells.

    PubMed

    Wu, Q; Delpire, E; Hebert, S C; Strange, K

    1998-12-01

    The function of the apical Na+-K+-2Cl- cotransporter in mammalian choroid plexus (CP) is uncertain and controversial. To investigate cotransporter function, we developed a novel dissociated rat CP cell preparation in which single, isolated cells maintain normal polarized morphology. Immunofluorescence demonstrated that in isolated cells the Na+-K+-ATPase, Na+-K+-2Cl- cotransporter, and aquaporin 1 water channel remained localized to the brush border, whereas the Cl-/HCO-3 (anion) exchanger type 2 was confined to the basolateral membrane. We utilized video-enhanced microscopy and cell volume measurement techniques to investigate cotransporter function. Application of 100 microM bumetanide caused CP cells to shrink rapidly. Elevation of extracellular K+ from 3 to 6 or 25 mM caused CP cells to swell 18 and 33%, respectively. Swelling was blocked completely by Na+ removal or by addition of 100 microM bumetanide. Exposure of CP cells to 5 mM BaCl2 induced rapid swelling that was inhibited by 100 microM bumetanide. We conclude that the CP cotransporter is constitutively active and propose that it functions in series with Ba2+-sensitive K+ channels to reabsorb K+ from cerebrospinal fluid to blood. PMID:9843718

  3. Phase Development of NaOH Activated Blast Furnace Slag Geopolymers Cured at 90 deg. C

    SciTech Connect

    Zhang Bo; Bigley, C.; Ryan, M. J.; MacKenzie, K. J. D.; Brown, I. W. M.

    2009-07-23

    Geopolymers were synthesized from blast furnace slag activated with different levels of NaOH and cured at 90 deg. C. The crystalline and amorphous phases of the resulting geopolymers were characterized by XRD quantitative analysis, and {sup 29}Si and {sup 27}Al MAS NMR. Amorphous species are predominant in materials at all NaOH levels. In the amorphous phase, aluminium substituted silicate species (Q{sup 2}(1Al)) dominated among the species of Q{sup 0}, Q{sup 1}, Q{sup 2}(1Al) and Q{sup 2}(where Q{sup n}(mAl) denotes a silicate tetrahedron [SiO{sub 4}] with n bridging oxygen atoms and m adjacent tetrahedra substituted with an aluminate tetrahedron [AlO{sub 4}]). In addition, it was also found that 4-fold coordination aluminium [AlO{sub 4}] species ({sup 27}Al chemical shift 66.1 ppm) in low NaOH containing materials differs from the species ({sup 27}Al chemical shift 74.3 ppm) in high NaOH containing materials.

  4. Real-time kinetics of electrogenic Na+ transport by rhodopsin from the marine flavobacterium Dokdonia sp. PRO95

    PubMed Central

    Bogachev, Alexander V.; Bertsova, Yulia V.; Verkhovskaya, Marina L.; Mamedov, Mahir D.; Skulachev, Vladimir P.

    2016-01-01

    Discovery of the light-driven sodium-motive pump Na+-rhodopsin (NaR) has initiated studies of the molecular mechanism of this novel membrane-linked energy transducer. In this paper, we investigated the photocycle of NaR from the marine flavobacterium Dokdonia sp. PRO95 and identified electrogenic and Na+-dependent steps of this cycle. We found that the NaR photocycle is composed of at least four steps: NaR519 + hv → K585 → (L450↔M495) → O585 → NaR519. The third step is the only step that depends on the Na+ concentration inside right-side-out NaR-containing proteoliposomes, indicating that this step is coupled with Na+ binding to NaR. For steps 2, 3, and 4, the values of the rate constants are 4×104 s–1, 4.7 × 103 M–1 s–1, and 150 s–1, respectively. These steps contributed 15, 15, and 70% of the total membrane electric potential (Δψ ~ 200 mV) generated by a single turnover of NaR incorporated into liposomes and attached to phospholipid-impregnated collodion film. On the basis of these observations, a mechanism of light-driven Na+ pumping by NaR is suggested. PMID:26864904

  5. Presynaptic Control of Glycine Transporter 2 (GlyT2) by Physical and Functional Association with Plasma Membrane Ca2+-ATPase (PMCA) and Na+-Ca2+ Exchanger (NCX)*

    PubMed Central

    de Juan-Sanz, Jaime; Núñez, Enrique; Zafra, Francisco; Berrocal, María; Corbacho, Isaac; Ibáñez, Ignacio; Arribas-González, Esther; Marcos, Daniel; López-Corcuera, Beatriz; Mata, Ana M.; Aragón, Carmen

    2014-01-01

    Fast inhibitory glycinergic transmission occurs in spinal cord, brainstem, and retina to modulate the processing of motor and sensory information. After synaptic vesicle fusion, glycine is recovered back to the presynaptic terminal by the neuronal glycine transporter 2 (GlyT2) to maintain quantal glycine content in synaptic vesicles. The loss of presynaptic GlyT2 drastically impairs the refilling of glycinergic synaptic vesicles and severely disrupts neurotransmission. Indeed, mutations in the gene encoding GlyT2 are the main presynaptic cause of hyperekplexia in humans. Here, we show a novel endogenous regulatory mechanism that can modulate GlyT2 activity based on a compartmentalized interaction between GlyT2, neuronal plasma membrane Ca2+-ATPase (PMCA) isoforms 2 and 3, and Na+/Ca2+-exchanger 1 (NCX1). This GlyT2·PMCA2,3·NCX1 complex is found in lipid raft subdomains where GlyT2 has been previously found to be fully active. We show that endogenous PMCA and NCX activities are necessary for GlyT2 activity and that this modulation depends on lipid raft integrity. Besides, we propose a model in which GlyT2·PMCA2–3·NCX complex would help Na+/K+-ATPase in controlling local Na+ increases derived from GlyT2 activity after neurotransmitter release. PMID:25315779

  6. Optimization of NaOH Molarity, LUSI Mud/Alkaline Activator, and Na2SiO3/NaOH Ratio to Produce Lightweight Aggregate-Based Geopolymer.

    PubMed

    Razak, Rafiza Abdul; Abdullah, Mohd Mustafa Al Bakri; Hussin, Kamarudin; Ismail, Khairul Nizar; Hardjito, Djwantoro; Yahya, Zarina

    2015-05-21

    This paper presents the mechanical function and characterization of an artificial lightweight geopolymer aggregate (ALGA) using LUSI (Sidoarjo mud) and alkaline activator as source materials. LUSI stands for LU-Lumpur and SI-Sidoarjo, meaning mud from Sidoarjo which erupted near the Banjarpanji-1 exploration well in Sidoarjo, East Java, Indonesia on 27 May 2006. The effect of NaOH molarity, LUSI mud/Alkaline activator (LM/AA) ratio, and Na2SiO3/NaOH ratio to the ALGA are investigated at a sintering temperature of 950 °C. The results show that the optimum NaOH molarity found in this study is 12 M due to the highest strength (lowest AIV value) of 15.79% with lower water absorption and specific gravity. The optimum LUSI mud/Alkaline activator (LM/AA) ratio of 1.7 and the Na2SiO3/NaOH ratio of 0.4 gives the highest strength with AIV value of 15.42% with specific gravity of 1.10 g/cm3 and water absorption of 4.7%. The major synthesized crystalline phases were identified as sodalite, quartz and albite. Scanning Electron Microscope (SEM) image showed more complete geopolymer matrix which contributes to highest strength of ALGA produced.

  7. Optimization of NaOH Molarity, LUSI Mud/Alkaline Activator, and Na2SiO3/NaOH Ratio to Produce Lightweight Aggregate-Based Geopolymer.

    PubMed

    Razak, Rafiza Abdul; Abdullah, Mohd Mustafa Al Bakri; Hussin, Kamarudin; Ismail, Khairul Nizar; Hardjito, Djwantoro; Yahya, Zarina

    2015-01-01

    This paper presents the mechanical function and characterization of an artificial lightweight geopolymer aggregate (ALGA) using LUSI (Sidoarjo mud) and alkaline activator as source materials. LUSI stands for LU-Lumpur and SI-Sidoarjo, meaning mud from Sidoarjo which erupted near the Banjarpanji-1 exploration well in Sidoarjo, East Java, Indonesia on 27 May 2006. The effect of NaOH molarity, LUSI mud/Alkaline activator (LM/AA) ratio, and Na2SiO3/NaOH ratio to the ALGA are investigated at a sintering temperature of 950 °C. The results show that the optimum NaOH molarity found in this study is 12 M due to the highest strength (lowest AIV value) of 15.79% with lower water absorption and specific gravity. The optimum LUSI mud/Alkaline activator (LM/AA) ratio of 1.7 and the Na2SiO3/NaOH ratio of 0.4 gives the highest strength with AIV value of 15.42% with specific gravity of 1.10 g/cm3 and water absorption of 4.7%. The major synthesized crystalline phases were identified as sodalite, quartz and albite. Scanning Electron Microscope (SEM) image showed more complete geopolymer matrix which contributes to highest strength of ALGA produced. PMID:26006238

  8. Optimization of NaOH Molarity, LUSI Mud/Alkaline Activator, and Na2SiO3/NaOH Ratio to Produce Lightweight Aggregate-Based Geopolymer

    PubMed Central

    Abdul Razak, Rafiza; Abdullah, Mohd Mustafa Al Bakri; Hussin, Kamarudin; Ismail, Khairul Nizar; Hardjito, Djwantoro; Yahya, Zarina

    2015-01-01

    This paper presents the mechanical function and characterization of an artificial lightweight geopolymer aggregate (ALGA) using LUSI (Sidoarjo mud) and alkaline activator as source materials. LUSI stands for LU-Lumpur and SI-Sidoarjo, meaning mud from Sidoarjo which erupted near the Banjarpanji-1 exploration well in Sidoarjo, East Java, Indonesia on 27 May 2006. The effect of NaOH molarity, LUSI mud/Alkaline activator (LM/AA) ratio, and Na2SiO3/NaOH ratio to the ALGA are investigated at a sintering temperature of 950 °C. The results show that the optimum NaOH molarity found in this study is 12 M due to the highest strength (lowest AIV value) of 15.79% with lower water absorption and specific gravity. The optimum LUSI mud/Alkaline activator (LM/AA) ratio of 1.7 and the Na2SiO3/NaOH ratio of 0.4 gives the highest strength with AIV value of 15.42% with specific gravity of 1.10 g/cm3 and water absorption of 4.7%. The major synthesized crystalline phases were identified as sodalite, quartz and albite. Scanning Electron Microscope (SEM) image showed more complete geopolymer matrix which contributes to highest strength of ALGA produced. PMID:26006238

  9. A novel Na(+) -Independent alanine-serine-cysteine transporter 1 inhibitor inhibits both influx and efflux of D-Serine.

    PubMed

    Sakimura, Katsuya; Nakao, Kenji; Yoshikawa, Masato; Suzuki, Motohisa; Kimura, Haruhide

    2016-10-01

    NMDA receptor dysfunctions are hypothesized to underlie the pathophysiology of schizophrenia, and treatment with D-serine (D-Ser), an NMDA receptor coagonist, may improve the clinical symptoms of schizophrenia. Thus, upregulating the synaptic D-Ser level is a novel strategy for schizophrenia treatment. Na(+) -independent alanine-serine-cysteine transporter 1 (asc-1) is a transporter responsible for regulating the extracellular D-Ser levels in the brain. In this study, we discovered a novel asc-1 inhibitor, (+)-amino(1-(3,5-dichlorophenyl)-3,5-dimethyl-1H-pyrazol-4-yl)acetic acid (ACPP), and assessed its pharmacological profile. ACPP inhibited the D-[(3) H]Ser uptake in human asc-1-expressing CHO cells and rat primary neurons with IC50 values of 0.72 ± 0.13 and 0.89 ± 0.30 μM, respectively. In accordance with the lower asc-1 expression levels in astrocytes, ACPP did not inhibit D-Ser uptake in rat primary astrocytes. In a microdialysis study, ACPP dose dependently decreased the extracellular D-Ser levels in the rat hippocampus under the same conditions in which the asc-1 inhibitor S-methyl-L-cysteine (SMLC) increased it. To obtain insights into this difference, we conducted a D-[(3) H]Ser efflux assay using asc-1-expressing CHO cells. ACPP inhibited D-[(3) H]Ser efflux, whereas SMLC increased it. These results suggest that ACPP is a novel inhibitor of asc-1. © 2016 Wiley Periodicals, Inc. PMID:27302861

  10. Intracellular mediators of Na -K pump activity in guinea pig pancreatic acinar cells

    SciTech Connect

    Hootman, S.R.; Ochs, D.L.; Williams, J.A.

    1985-10-01

    The involvement of CaS and cyclic nucleotides in neurohormonal regulation of Na -K -ATPase (Na -K pump) activity in guinea pig pancreatic acinar cells was investigated. Changes in Na+-K+ pump activity elicited by secretagogues were assessed by (3H)ouabain binding and by ouabain-sensitive YWRb uptake. Carbachol (CCh) and cholecystokinin octapeptide (CCK-8) each stimulated both ouabain-sensitive 86Rb+ uptake and equilibrium binding of (TH)ouabain by approximately 60%. Secretin increased both indicators of Na+-K+ pump activity by approximately 40% as did forskolin, 8-bromo- and dibutyryl cAMP, theophylline, and isobutylmethylxanthine. Incubation of acinar cells in CaS -free HEPES-buffered Ringer (HR) with 0.5 mM EGTA reduced the stimulatory effects of CCh and CCK-8 by up to 90% but caused only a small reduction in the effects of secretin, forskolin, and cAMP analogues. In addition, CCh, CCK-8, secretin, and forskolin each stimulated ouabain-insensitive 86Rb+ uptake by acinar cells. The increase elicited by CCh and CCK-8 was greatly reduced in the absence of extracellular CaS , while that caused by the latter two agents was not substantially altered. The effects of secretagogues on free CaS levels in pancreatic acinar cells also were investigated with quin-2, a fluorescent CaS chelator. Basal intracellular CaS concentration ((CaS )i) was 161 nM in resting cells and increased to 713 and 803 nM within 15 s after addition of 100 microM CCh or 10 nM CCK-8, respectively.

  11. Serum- and glucocorticoid-inducible kinase sgk2 stimulates the transport activity of human organic anion transporters 1 by enhancing the stability of the transporter.

    PubMed

    Xu, Da; Huang, Haozhe; Toh, May Fern; You, Guofeng

    2016-01-01

    Human organic anion transporter 1 (hOAT1) belongs to a family of organic anion transporters that play critical roles in the body disposition of clinically important drugs, including anti-viral therapeutics, anti-cancer drugs, antibiotics, antihypertensives, and anti-inflammatories. hOAT1 is abundantly expressed in the kidney and brain. In the current study, we examined the regulation of hOAT1 by serum- and glucocorticoid-inducible kinase 2 (sgk2) in the kidney COS-7 cells. We showed that sgk2 stimulated hOAT1 transport activity. Such stimulation mainly resulted from an increased cell surface expression of the transporter, kinetically revealed as an increased maximal transport velocity V max without significant change in substrate-binding affinity K m. We further showed that stimulation of hOAT1 activity by sgk2 was achieved by preventing hOAT1 degradation. Our co-immunoprecipitation experiment revealed that the effect of sgk2 on hOAT1 was through a direct interaction between these two proteins. In conclusion, our study demonstrated that sgk2 stimulates hOAT1 transport activity by enhancing the stability of the transporter. This study provides the insights into sgk2 regulation of hOAT1-mediated transport in normal physiology and disease. PMID:27335683

  12. Evidence of active transport involvement in morphine transport via MDCKII and MDCK-PGP cell lines.

    PubMed

    Mashayekhi, S O; Sattari, M R; Routledge, P A

    2010-07-01

    Several transporters appear to be important in transporting various drugs. Many patients, who receive morphine as analgesic medication, also receive other medications with potency of changing morphine transport by affecting P-glycoprotein (P-GP) and oatp2 transport system. This could influence morphine pharmacokinetics and pharmacodynamics. The aim of present study was to elucidate the transport mechanisms involved in transporting morphine via MDCKII and MDCK-PGP cells. Morphine permeability was examined in the presence of various compounds with ability in inhibiting different transport systems including: digoxin, probenecid and d- glucose. The effect of morphine concentration changes on its transport was also examined. Morphine concentration was measured using HPLC with electrochemical detector. Morphine permeability via a MDCK II cells was greater than sucrose permeability, and reduced when a P-GP expressed cell line was used. Its permeability was increased significantly in the presence of a strong P-GP inhibitor. Morphine permeability decreased significantly in the presence of digoxin but not in the presence of d-glucose or probenecid. These results showed that morphine was a P-GP substrate, and digoxin related transporters such as oatp2 were involved in its transport. Morphine was not substrate for glucose or probenecid-sensitive transporters. PMID:21589798

  13. Evidence of active transport involvement in morphine transport via MDCKII and MDCK-PGP cell lines

    PubMed Central

    Mashayekhi, S.O.; Sattari, M.R.; Routledge, P.A.

    2010-01-01

    Several transporters appear to be important in transporting various drugs. Many patients, who receive morphine as analgesic medication, also receive other medications with potency of changing morphine transport by affecting P-glycoprotein (P-GP) and oatp2 transport system. This could influence morphine pharmacokinetics and pharmacodynamics. The aim of present study was to elucidate the transport mechanisms involved in transporting morphine via MDCKII and MDCK-PGP cells. Morphine permeability was examined in the presence of various compounds with ability in inhibiting different transport systems including: digoxin, probenecid and d- glucose. The effect of morphine concentration changes on its transport was also examined. Morphine concentration was measured using HPLC with electrochemical detector. Morphine permeability via a MDCK II cells was greater than sucrose permeability, and reduced when a P-GP expressed cell line was used. Its permeability was increased significantly in the presence of a strong P-GP inhibitor. Morphine permeability decreased significantly in the presence of digoxin but not in the presence of d-glucose or probenecid. These results showed that morphine was a P-GP substrate, and digoxin related transporters such as oatp2 were involved in its transport. Morphine was not substrate for glucose or probenecid-sensitive transporters. PMID:21589798

  14. Active transporters as enzymes: an energetic framework applied to major facilitator superfamily and ABC importer systems.

    PubMed

    Shilton, Brian H

    2015-04-15

    Active membrane transporters are dynamic molecular machines that catalyse transport across a membrane by coupling solute movement to a source of energy such as ATP or a secondary ion gradient. A central question for many active transporters concerns the mechanism by which transport is coupled to a source of energy. The transport process and associated energetic coupling involve conformational changes in the transporter. For efficient transport, the conformational changes must be tightly regulated and they must link energy use to movement of the substrate across the membrane. The present review discusses active transport using the well-established energetic framework for enzyme-mediated catalysis. In particular, membrane transport systems can be viewed as ensembles consisting of low-energy and high-energy conformations. The transport process involves binding interactions that selectively stabilize the higher energy conformations, and in this way promote conformational changes in the system that are coupled to decreases in free energy and substrate translocation. The major facilitator superfamily of secondary active transporters is used to illustrate these ideas, which are then be expanded to primary active transport mediated by ABC (ATP-binding cassette) import systems, with a focus on the well-studied maltose transporter.

  15. Water activated doping and transport in multilayered germanane crystals.

    PubMed

    Young, Justin R; Chitara, Basant; Cultrara, Nicholas D; Arguilla, Maxx Q; Jiang, Shishi; Fan, Fan; Johnston-Halperin, Ezekiel; Goldberger, Joshua E

    2016-01-27

    The synthesis of germanane (GeH) has opened the door for covalently functionalizable 2D materials in electronics. Herein, we demonstrate that GeH can be electronically doped by incorporating stoichiometric equivalents of phosphorus dopant atoms into the CaGe2 precursor. The electronic properties of these doped materials show significant atmospheric sensitivity, and we observe a reduction in resistance by up to three orders of magnitude when doped samples are measured in water-containing atmospheres. This variation in resistance is a result of water activation of the phosphorus dopants. Transport measurements in different contact geometries show a significant anisotropy between in-plane and out-of-plane resistances, with a much larger out-of-plane resistance. These measurements along with finite element modeling results predict that the current distribution in top-contacted crystals is restricted to only the topmost, water activated crystal layers. Taken together, these results pave the way for future electronic and optoelectronic applications utilizing group IV graphane analogues.

  16. Active Transport Can Greatly Enhance Cdc20:Mad2 Formation

    PubMed Central

    Ibrahim, Bashar; Henze, Richard

    2014-01-01

    To guarantee genomic integrity and viability, the cell must ensure proper distribution of the replicated chromosomes among the two daughter cells in mitosis. The mitotic spindle assembly checkpoint (SAC) is a central regulatory mechanism to achieve this goal. A dysfunction of this checkpoint may lead to aneuploidy and likely contributes to the development of cancer. Kinetochores of unattached or misaligned chromosomes are thought to generate a diffusible “wait-anaphase” signal, which is the basis for downstream events to inhibit the anaphase promoting complex/cyclosome (APC/C). The rate of Cdc20:C-Mad2 complex formation at the kinetochore is a key regulatory factor in the context of APC/C inhibition. Computer simulations of a quantitative SAC model show that the formation of Cdc20:C-Mad2 is too slow for checkpoint maintenance when cytosolic O-Mad2 has to encounter kinetochores by diffusion alone. Here, we show that an active transport of O-Mad2 towards the spindle mid-zone increases the efficiency of Mad2-activation. Our in-silico data indicate that this mechanism can greatly enhance the formation of Cdc20:Mad2 and furthermore gives an explanation on how the “wait-anaphase” signal can dissolve abruptly within a short time. Our results help to understand parts of the SAC mechanism that remain unclear. PMID:25338047

  17. Active transport can greatly enhance Cdc20:Mad2 formation.

    PubMed

    Ibrahim, Bashar; Henze, Richard

    2014-01-01

    To guarantee genomic integrity and viability, the cell must ensure proper distribution of the replicated chromosomes among the two daughter cells in mitosis.The mitotic spindle assembly checkpoint (SAC) is a central regulatory mechanism to achieve this goal. A dysfunction of this checkpoint may lead to aneuploidy and likely contributes to the development of cancer. Kinetochores of unattached or misaligned chromosomes are thought to generate a diffusible ''wait-anaphase'' signal, which is the basis for downstream events to inhibit the anaphase promoting complex/cyclosome (APC/C). The rate of Cdc20:C-Mad2 complex formation at the kinetochore is a key regulatory factor in the context of APC/C inhibition. Computer simulations of a quantitative SAC model show that the formation of Cdc20:C-Mad2 is too slow for checkpoint maintenance when cytosolic O-Mad2 has to encounter kinetochores by diffusion alone. Here, we show that an active transport of O-Mad2 towards the spindle mid-zone increases the efficiency of Mad2-activation. Our data indicate that this mechanism can greatly enhance the formation of Cdc20:Mad2 and furthermore gives an explanation on how the ''wait-anaphase'' signal can dissolve abruptly within a short time. Our results help to understand parts of the SAC mechanism that remain unclear.

  18. Active transport in dense diffusive single-file systems.

    PubMed

    Illien, P; Bénichou, O; Mejía-Monasterio, C; Oshanin, G; Voituriez, R

    2013-07-19

    We study a minimal model of active transport in crowded single-file environments which generalizes the emblematic model of single-file diffusion to the case when the tracer particle (TP) performs either an autonomous directed motion or is biased by an external force, while all other particles of the environment (bath) perform unbiased diffusions. We derive explicit expressions, valid in the limit of high density of bath particles, of the full distribution P((n))(X) of the TP position and of all its cumulants, for arbitrary values of the bias f and for any time n. Our analysis reveals striking features, such as the anomalous scaling [proportionality] √[n] of all cumulants, the equality of cumulants of the same parity characteristic of a Skellam distribution and a convergence to a Gaussian distribution in spite of asymmetric density profiles of bath particles. Altogether, our results provide the full statistics of the TP position and set the basis for a refined analysis of real trajectories of active particles in crowded single-file environments.

  19. Piezoelectric Active Humidity Sensors Based on Lead-Free NaNbO₃ Piezoelectric Nanofibers.

    PubMed

    Gu, Li; Zhou, Di; Cao, Jun Cheng

    2016-06-07

    The development of micro-/nano-scaled energy harvesters and the self-powered sensor system has attracted great attention due to the miniaturization and integration of the micro-device. In this work, lead-free NaNbO₃ piezoelectric nanofibers with a monoclinic perovskite structure were synthesized by the far-field electrospinning method. The flexible active humidity sensors were fabricated by transferring the nanofibers from silicon to a soft polymer substrate. The sensors exhibited outstanding piezoelectric energy-harvesting performance with output voltage up to 2 V during the vibration process. The output voltage generated by the NaNbO₃ sensors exhibited a negative correlation with the environmental humidity varying from 5% to 80%, where the peak-to-peak value of the output voltage generated by the sensors decreased from 0.40 to 0.07 V. The sensor also exhibited a short response time, good selectively against ethanol steam, and great temperature stability. The piezoelectric active humidity sensing property could be attributed to the increased leakage current in the NaNbO₃ nanofibers, which was generated due to proton hopping among the H₃O⁺ groups in the absorbed H₂O layers under the driving force of the piezoelectric potential.

  20. Piezoelectric Active Humidity Sensors Based on Lead-Free NaNbO3 Piezoelectric Nanofibers

    PubMed Central

    Gu, Li; Zhou, Di; Cao, Jun Cheng

    2016-01-01

    The development of micro-/nano-scaled energy harvesters and the self-powered sensor system has attracted great attention due to the miniaturization and integration of the micro-device. In this work, lead-free NaNbO3 piezoelectric nanofibers with a monoclinic perovskite structure were synthesized by the far-field electrospinning method. The flexible active humidity sensors were fabricated by transferring the nanofibers from silicon to a soft polymer substrate. The sensors exhibited outstanding piezoelectric energy-harvesting performance with output voltage up to 2 V during the vibration process. The output voltage generated by the NaNbO3 sensors exhibited a negative correlation with the environmental humidity varying from 5% to 80%, where the peak-to-peak value of the output voltage generated by the sensors decreased from 0.40 to 0.07 V. The sensor also exhibited a short response time, good selectively against ethanol steam, and great temperature stability. The piezoelectric active humidity sensing property could be attributed to the increased leakage current in the NaNbO3 nanofibers, which was generated due to proton hopping among the H3O+ groups in the absorbed H2O layers under the driving force of the piezoelectric potential. PMID:27338376

  1. Piezoelectric Active Humidity Sensors Based on Lead-Free NaNbO₃ Piezoelectric Nanofibers.

    PubMed

    Gu, Li; Zhou, Di; Cao, Jun Cheng

    2016-01-01

    The development of micro-/nano-scaled energy harvesters and the self-powered sensor system has attracted great attention due to the miniaturization and integration of the micro-device. In this work, lead-free NaNbO₃ piezoelectric nanofibers with a monoclinic perovskite structure were synthesized by the far-field electrospinning method. The flexible active humidity sensors were fabricated by transferring the nanofibers from silicon to a soft polymer substrate. The sensors exhibited outstanding piezoelectric energy-harvesting performance with output voltage up to 2 V during the vibration process. The output voltage generated by the NaNbO₃ sensors exhibited a negative correlation with the environmental humidity varying from 5% to 80%, where the peak-to-peak value of the output voltage generated by the sensors decreased from 0.40 to 0.07 V. The sensor also exhibited a short response time, good selectively against ethanol steam, and great temperature stability. The piezoelectric active humidity sensing property could be attributed to the increased leakage current in the NaNbO₃ nanofibers, which was generated due to proton hopping among the H₃O⁺ groups in the absorbed H₂O layers under the driving force of the piezoelectric potential. PMID:27338376

  2. Osmoregulation and salt gland Na, K-ATPase activity following exposure to the anticholinesterase fenthion

    USGS Publications Warehouse

    Rattner, B.A.; Fleming, W.J.; Murray, H.C.

    1982-01-01

    Salt gland function and osmoregulation in aquatic birds drinking hyperosmotic water has been suggested to be impaired by organophosphorus insecticides. To test this hypothesis, adult ducks (Anas rubripes) were provided various regimens of fresh or salt (1.5% NaCl) water (FW, SW) and mash containing vehicle or 21 ppm fenthion (Fn) on days 1-7 and 7-12 of this study. The 8 treatments (day 1-7:day 7-12) included :FW:FW, FW:FW+Fn, FW:SW, FW+Fn:SW, FW:SW+Fn, FW+Fn:SW+FN, SW;SW, and SW:5W+Fn. Ducks were bled by jugular venipuncture on days 1,7 and 12, and then sacrificed. Brain and salt gland acetylcholinesterase activities were substantially inhibited (44-52% and 14-26%) by Fn. However, plasma Na, Cl and osmolality, as indirect but cumulative indices of salt gland function, were uniformly elevated in all SW groups including those receiving Fn. In a second experiment, salt gland Na,K-ATPase activity was reduced after in vitro incubation with DDE (40 and 400 ?M; positive control), but was unaffected by Fn and its oxygen analog (0.04-400 ?M). The present findings suggest that environmentally realistic concentrations of organophosphorus insecticides do not affect osmoregulatory function in adult ducks.

  3. Ouabain triggers preconditioning through activation of the Na+,K+-ATPase signaling cascade in rat hearts

    PubMed Central

    Pierre, Sandrine V.; Yang, Changjun; Yuan, Zhaokan; Seminerio, Jennifer; Mouas, Christian; Garlid, Keith D.; Dos-Santos, Pierre; Xie, Zijian

    2007-01-01

    Objective Because ouabain activates several pathways that are critical to cardioprotective mechanisms such as ischemic preconditioning, we tested if this digitalis compound could protect the heart against ischemia-reperfusion injury through activation of the Na+,K+-ATPase/c-Src receptor complex. Methods and Results In Langendorff-perfused rat hearts, a short (4 min) administration of ouabain 10 μM followed by an 8-minute washout before 30 minutes of global ischemia and reperfusion improved cardiac function, decreased lactate dehydrogenase release and reduced infarct size by 40%. Western blot analysis revealed that ouabain activated the cardioprotective phospholipase Cγ1/protein kinase Cε (PLC-γ1/PKCε) pathway. Pre-treatment of the hearts with the Src kinase family inhibitor 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolol[3,4-d]pyrimidine (PP2) blocked not only ouabain-induced activation of PLC-γ1/PKCε pathway, but also cardiac protection. This protection was also blocked by a PKCε translocation inhibitor peptide (PKCε TIP). Conclusion Short exposure to a low concentration of ouabain protects the heart against ischemia/reperfusion injury. This effect of ouabain on the heart is most likely due to the activation of the Na+,K+-ATPase/c-Src receptor complex and subsequent stimulation of key mediators of preconditioning, namely PLC-γ1 and PKCε. PMID:17157283

  4. Mutations in the diastrophic dysplasia sulfate transporter (DTDST) gene: correlation between sulfate transport activity and chondrodysplasia phenotype.

    PubMed

    Karniski, L P

    2001-07-01

    The diastrophic dysplasia sulfate transporter (DTDST) gene encodes a transmembrane protein that transports sulfate into chondrocytes to maintain adequate sulfation of proteoglycans. Mutations in this gene are responsible for four recessively inherited chondrodysplasias that include diastrophic dysplasia, multiple epiphyseal dysplasia, atelosteogenesis type 2 and achondrogenesis 1B (ACG-1B). To determine whether the DTDST mutations found in individuals with these chondrodysplasias differ functionally from each other, we compared the sulfate transport activity of 11 reported DTDST mutations. Five mutations, G255E, Delta a1751, L483P, R178X and N425D, had minimal sulfate transport function following expression in Xenopus laevis oocytes. Two mutations, Delta V340 and R279W, transported sulfate at rates of 17 and 32%, respectively, of wild-type DTDST. Four mutations, A715V, C653S, Q454P and G678V, had rates of sulfate transport nearly equal to that of wild-type DTDST. Transport kinetics were not different among the four mutations with near-normal sulfate transport function and wild-type DTDST. When the sulfate transport function of the different DTDST mutations are grouped according to the general phenotypes, individuals with the most severe form, ACG-1B, tend to be homozygous for null mutations, individuals with the moderately severe atelosteogenesis type 2 have at least one allele with a loss-of-function mutation, and individuals with the mildest forms are typically homozygous for mutations with residual sulfate transport function. However, in the X.laevis oocyte expression system, the correlation between residual transport function and the severity of phenotype was not absolute, suggesting that factors in addition to the intrinsic sulfate transport properties of the DTDST protein may influence the phenotype in individuals with DTDST mutations. PMID:11448940

  5. Voltage-gated Na+ Channel Activity Increases Colon Cancer Transcriptional Activity and Invasion Via Persistent MAPK Signaling

    PubMed Central

    House, Carrie D.; Wang, Bi-Dar; Ceniccola, Kristin; Williams, Russell; Simaan, May; Olender, Jacqueline; Patel, Vyomesh; Baptista-Hon, Daniel T.; Annunziata, Christina M.; Silvio Gutkind, J.; Hales, Tim G.; Lee, Norman H.

    2015-01-01

    Functional expression of voltage-gated Na+ channels (VGSCs) has been demonstrated in multiple cancer cell types where channel activity induces invasive activity. The signaling mechanisms by which VGSCs promote oncogenesis remain poorly understood. We explored the signal transduction process critical to VGSC-mediated invasion on the basis of reports linking channel activity to gene expression changes in excitable cells. Coincidentally, many genes transcriptionally regulated by the SCN5A isoform in colon cancer have an over-representation of cis-acting sites for transcription factors phosphorylated by ERK1/2 MAPK. We hypothesized that VGSC activity promotes MAPK activation to induce transcriptional changes in invasion-related genes. Using pharmacological inhibitors/activators and siRNA-mediated gene knockdowns, we correlated channel activity with Rap1-dependent persistent MAPK activation in the SW620 human colon cancer cell line. We further demonstrated that VGSC activity induces downstream changes in invasion-related gene expression via a PKA/ERK/c-JUN/ELK-1/ETS-1 transcriptional pathway. This is the first study illustrating a molecular mechanism linking functional activity of VGSCs to transcriptional activation of invasion-related genes. PMID:26096612

  6. Voltage-gated Na+ Channel Activity Increases Colon Cancer Transcriptional Activity and Invasion Via Persistent MAPK Signaling

    NASA Astrophysics Data System (ADS)

    House, Carrie D.; Wang, Bi-Dar; Ceniccola, Kristin; Williams, Russell; Simaan, May; Olender, Jacqueline; Patel, Vyomesh; Baptista-Hon, Daniel T.; Annunziata, Christina M.; Silvio Gutkind, J.; Hales, Tim G.; Lee, Norman H.

    2015-06-01

    Functional expression of voltage-gated Na+ channels (VGSCs) has been demonstrated in multiple cancer cell types where channel activity induces invasive activity. The signaling mechanisms by which VGSCs promote oncogenesis remain poorly understood. We explored the signal transduction process critical to VGSC-mediated invasion on the basis of reports linking channel activity to gene expression changes in excitable cells. Coincidentally, many genes transcriptionally regulated by the SCN5A isoform in colon cancer have an over-representation of cis-acting sites for transcription factors phosphorylated by ERK1/2 MAPK. We hypothesized that VGSC activity promotes MAPK activation to induce transcriptional changes in invasion-related genes. Using pharmacological inhibitors/activators and siRNA-mediated gene knockdowns, we correlated channel activity with Rap1-dependent persistent MAPK activation in the SW620 human colon cancer cell line. We further demonstrated that VGSC activity induces downstream changes in invasion-related gene expression via a PKA/ERK/c-JUN/ELK-1/ETS-1 transcriptional pathway. This is the first study illustrating a molecular mechanism linking functional activity of VGSCs to transcriptional activation of invasion-related genes.

  7. Evaluation of Proposed In Vivo Probe Substrates and Inhibitors for Phenotyping Transporter Activity in Humans.

    PubMed

    Momper, Jeremiah D; Tsunoda, Shirley M; Ma, Joseph D

    2016-07-01

    Drug transporters are present in various tissues and have a significant role in drug absorption, distribution, and elimination. The International Transporter Consortium has identified 7 transporters of increasing importance from evidence of clinically significant transporter-mediated drug-drug interactions. The transporters are P-glycoprotein, breast cancer resistance protein, organic anion transporting polypeptide (OATP) 1B1, OATP1B3, organic cation transporter 2, organic anion transporters (OAT) 1, and OAT3. Decision trees were created based on in vitro experiments to determine whether an in vivo transporter-mediated drug-drug interaction study is needed. Phenotyping is a methodology that evaluates real-time in vivo transporter activity, whereby changes in a probe substrate or probe inhibitor reflect alternations in the activity of the specified transporter. In vivo probe substrates and/or probe inhibitors have been proposed for each aforementioned transporter. In vitro findings and animal models provide the strongest evidence regarding probe specificity. However, such findings have not conclusively correlated with human phenotyping studies. Furthermore, the extent of contribution from multiple transporters in probe disposition complicates the ability to discern if study findings are the result of a specific transporter and thus provide a recommendation for a preferred probe for a drug transporter. PMID:27385182

  8. The association between access to public transportation and self-reported active commuting.

    PubMed

    Djurhuus, Sune; Hansen, Henning S; Aadahl, Mette; Glümer, Charlotte

    2014-12-05

    Active commuting provides routine-based regular physical activity which can reduce the risk of chronic diseases. Using public transportation involves some walking or cycling to a transit stop, transfers and a walk to the end location and users of public transportation have been found to accumulate more moderate physical activity than non-users. Understanding how public transportation characteristics are associated with active transportation is thus important from a public health perspective. This study examines the associations between objective measures of access to public transportation and self-reported active commuting. Self-reported time spent either walking or cycling commuting each day and the distance to workplace were obtained for adults aged 16 to 65 in the Danish National Health Survey 2010 (n = 28,928). Access to public transportation measures were computed by combining GIS-based road network distances from home address to public transit stops an integrating their service level. Multilevel logistic regression was used to examine the association between access to public transportation measures and active commuting. Distance to bus stop, density of bus stops, and number of transport modes were all positively associated with being an active commuter and with meeting recommendations of physical activity. No significant association was found between bus services at the nearest stop and active commuting. The results highlight the importance of including detailed measurements of access to public transit in order to identify the characteristics that facilitate the use of public transportation and active commuting.

  9. Mean ionic activity coefficients in aqueous NaCl solutions from molecular dynamics simulations

    SciTech Connect

    Mester, Zoltan; Panagiotopoulos, Athanassios Z.

    2015-01-28

    The mean ionic activity coefficients of aqueous NaCl solutions of varying concentrations at 298.15 K and 1 bar have been obtained from molecular dynamics simulations by gradually turning on the interactions of an ion pair inserted into the solution. Several common non-polarizable water and ion models have been used in the simulations. Gibbs-Duhem equation calculations of the thermodynamic activity of water are used to confirm the thermodynamic consistency of the mean ionic activity coefficients. While the majority of model combinations predict the correct trends in mean ionic activity coefficients, they overestimate their values at high salt concentrations. The solubility predictions also suffer from inaccuracies, with all models underpredicting the experimental values, some by large factors. These results point to the need for further ion and water model development.

  10. School Travel Planning: Mobilizing School and Community Resources to Encourage Active School Transportation

    ERIC Educational Resources Information Center

    Buliung, Ron; Faulkner, Guy; Beesley, Theresa; Kennedy, Jacky

    2011-01-01

    Background: Active school transport (AST), school travel using an active mode like walking, may be important to children's overall physical activity. A "school travel plan" (STP) documents a school's transport characteristics and provides an action plan to address school and neighborhood barriers to AST. Methods: We conducted a pilot STP…

  11. Potential of jackfruit peel as precursor for activated carbon prepared by microwave induced NaOH activation.

    PubMed

    Foo, K Y; Hameed, B H

    2012-05-01

    The feasibility of preparing activated carbon (JPAC) from jackfruit peel, an industrial residue abundantly available from food manufacturing plants via microwave-assisted NaOH activation was explored. The influences of chemical impregnation ratio, microwave power and radiation time on the properties of activated carbon were investigated. JPAC was examined by pore structural analysis, scanning electron microscopy, Fourier transform infrared spectroscopy, nitrogen adsorption isotherm, elemental analysis, surface acidity/basicity and zeta potential measurements. The adsorptive behavior of JPAC was quantified using methylene blue as model dye compound. The best conditions resulted in JPAC with a monolayer adsorption capacity of 400.06 mg/g and carbon yield of 80.82%. The adsorption data was best fitted to the pseudo-second-order equation, while the adsorption mechanism was well described by the intraparticle diffusion model. The findings revealed the versatility of jackfruit peels as good precursor for preparation of high quality activated carbon.

  12. Plasma Membrane Na+ Transport in a Salt-Tolerant Charophyte (Isotopic Fluxes, Electrophysiology, and Thermodynamics in Plants Adapted to Saltwater and Freshwater).

    PubMed

    Kiegle, E. A.; Bisson, M. A.

    1996-08-01

    In salt-tolerant Chara longifolia, enhanced Na+ efflux plays an important role in maintaining low cytoplasmic Na+. When it is cultured in fresh water (FW), C. longifolia has a higher Na+ efflux than the obligate FW Chara corallina, although pH dependence and inhibitor profiles are similar for both species (J. Whittington and M.A. Bisson [1994] J Exp Bot 45: 657-665). When it is cultured in saltwater, C. longifolia has a Na+ efflux of 264 [plus or minus] 14 nmol m-2 s-1 at pH 7, 13 times higher than FW-adapted cultures and 31 times higher than C. corallina. As in FW-adapted plants, efflux is highest at pH 5, but pH dependence is less steep and more linear in cells adapted to saltwater. In plants of both species from FW cultures, Na+ efflux is inhibited by Li+ at pH 5 but not at pH 7 or 9, whereas in the salt-adapted C. longifolia, Li+ inhibits Na+ efflux at pH 7 and 9 but not at pH 5. Amiloride inhibits Na+ efflux in salt-adapted cells but not in FW cells. We conclude that a new type of Na+ efflux system is induced in salt-adapted plants, although both systems have characteristics suggestive of a Na+/H+ antiport. In all cases, a 1:1 Na+/H+ antiport would have sufficient energy to maintain the cytoplasmic Na+ activities measured at pH 5 and 7 but not at pH 9, which suggests that another efflux system must be operating at pH 9.

  13. Analysis of transcriptional regulation and tissue-specific expression of Avicennia marina Plasma Membrane Protein 3 suggests it contributes to Na(+) transport and homoeostasis in A. marina.

    PubMed

    Chidambaram, Rajalakshmi; Venkataraman, Gayatri; Parida, Ajay

    2015-07-01

    Plasma membrane proteins (PMP3) play a role in cation homoeostasis. The 5' flanking sequence of stress inducible, Avicennia marina PMP3 (AmPMP3prom) was transcriptionally fused to (a) GUS or (b) GFP-AmPMP3 and analyzed in transgenic tobacco. Tissue-histochemical GUS and GFP:AmPMP3 localization are co-incident under basal and stress conditions. AmPMP3prom directed GUS activity is highest in roots. Basal transcription is conferred by a 388bp segment upstream of the translation start site. A 463bp distal enhancer in the AmPMP3prom confers enhanced expression under salinity in all tissues and also responds to increases in salinity. The effect of a central, stem-specific negative regulatory region is suppressed by the distal enhancer. The A. marina rhizosphere encounters dynamic changes in salinity at the inter-tidal interface. The complex, tissue-specific transcriptional responsiveness of AmPMP3 to salinity appears to have evolved in response to these changes. Under salinity, guard cell and phloem-specific expression of GFP:AmPMP3 is highly enhanced. Mesophyll, trichomes, bundle sheath, parenchymatous cortex and xylem parenchyma also show GFP:AmPMP3 expression. Cis-elements conferring stress, root and vascular-specific expression are enriched in the AmPMP3 promoter. Pronounced vascular-specific AmPMP3 expression suggests a role in salinity induced Na(+) transport, storage, and secretion in A. marina.

  14. Are the correlates of active school transport context-specific?

    PubMed Central

    Larouche, R; Sarmiento, O L; Broyles, S T; Denstel, K D; Church, T S; Barreira, T V; Chaput, J-P; Fogelholm, M; Hu, G; Kuriyan, R; Kurpad, A; Lambert, E V; Maher, C; Maia, J; Matsudo, V; Olds, T; Onywera, V; Standage, M; Tremblay, M S; Tudor-Locke, C; Zhao, P; Katzmarzyk, P T

    2015-01-01

    OBJECTIVES: Previous research consistently indicates that children who engage in active school transport (AST) are more active than their peers who use motorized modes (car or bus). However, studies of the correlates of AST have been conducted predominantly in high-income countries and have yielded mixed findings. Using data from a heterogeneous sample of 12 country sites across the world, we investigated the correlates of AST in 9–11-year olds. METHODS: The analytical sample comprised 6555 children (53.8% girls), who reported their main travel mode to school and the duration of their school trip. Potential individual and neighborhood correlates of AST were assessed with a parent questionnaire adapted from previously validated instruments. Multilevel generalized linear mixed models (GLMM) were used to examine the associations between individual and neighborhood variables and the odds of engaging in AST while controlling for the child's school. Site moderated the relationship of seven of these variables with AST; therefore we present analyses stratified by site. RESULTS: The prevalence of AST varied from 5.2 to 79.4% across sites and the school-level intra-class correlation ranged from 0.00 to 0.56. For each site, the final GLMM included a different set of correlates of AST. Longer trip duration (that is, ⩾16 min versus ⩽15 min) was associated with lower odds of AST in eight sites. Other individual and neighborhood factors were associated with AST in three sites or less. CONCLUSIONS: Our results indicate wide variability in the prevalence and correlates of AST in a large sample of children from twelve geographically, economically and culturally diverse country sites. This suggests that AST interventions should not adopt a ‘one size fits all' approach. Future research should also explore the association between psychosocial factors and AST in different countries. PMID:27152191

  15. Trimethyloxonium modification of batrachotoxin-activated Na channels alters functionally important protein residues.

    PubMed Central

    Cherbavaz, D B

    1995-01-01

    The extracellular side of single batrachotoxin-activated voltage-dependent Na channels isolated from rat skeletal muscle membranes incorporated into neutral planar lipid bilayers were treated in situ with the carboxyl methylating reagent, trimethyloxonium (TMO). These experiments were designed to determine whether TMO alters Na channel function by a general through-space electrostatic mechanism or by methylating specific carboxyl groups essential to channel function. TMO modification reduced single-channel conductance by decreasing the maximal turnover rate. Modification increased channel selectivity for sodium ions relative to potassium ions as measured under biionic conditions. TMO modification increased the mu-conotoxin (muCTX) off-rate by three orders of magnitude. Modification did not alter the muCTX on-rate at low ionic strength or Na channel voltage-dependent gating characteristics. These data demonstrate that TMO does not act via a general electrostatic mechanism. Instead, TMO targets protein residues specifically involved in ion conduction, ion selectivity, and muCTX binding. These data support the hypothesis that muCTX blocks open-channel current by physically obstructing the ion channel pore. PMID:7787022

  16. Cholesterol inhibits the nuclear entry of estrogen receptor activation factor (E-RAF) and its dimerization with the nonactivated estrogen receptor (naER) in goat uterus.

    PubMed

    Thampan, R V; Zafar, A; Imam, N S; Sreeja, S; Suma, K; Vairamani, M

    2000-04-01

    An alternative form of estrogen receptor isolated from goat uterus, the nonactivated estrogen receptor (