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1Latest Papers from Table of Contents or Articles in PressD. P. Hibar ; J. L. Stein ; M. E. Renteria ; A. Arias-Vasquez ; S. Desrivieres ; N. Jahanshad ; R. Toro ; K. Wittfeld ; L. Abramovic ; M. Andersson ; B. S. Aribisala ; N. J. Armstrong ; M. Bernard ; M. M. Bohlken ; M. P. Boks ; J. Bralten ; A. A. Brown ; M. M. Chakravarty ; Q. Chen ; C. R. Ching ; G. Cuellar-Partida ; A. den Braber ; S. Giddaluru ; A. L. Goldman ; O. Grimm ; T. Guadalupe ; J. Hass ; G. Woldehawariat ; A. J. Holmes ; M. Hoogman ; D. Janowitz ; T. Jia ; S. Kim ; M. Klein ; B. Kraemer ; P. H. Lee ; L. M. Olde Loohuis ; M. Luciano ; C. Macare ; K. A. Mather ; M. Mattheisen ; Y. Milaneschi ; K. Nho ; M. Papmeyer ; A. Ramasamy ; S. L. Risacher ; R. Roiz-Santianez ; E. J. Rose ; A. Salami ; P. G. Samann ; L. Schmaal ; A. J. Schork ; J. Shin ; L. T. Strike ; A. Teumer ; M. M. van Donkelaar ; K. R. van Eijk ; R. K. Walters ; L. T. Westlye ; C. D. Whelan ; A. M. Winkler ; M. P. Zwiers ; S. Alhusaini ; L. Athanasiu ; S. Ehrlich ; M. M. Hakobjan ; C. B. Hartberg ; U. K. Haukvik ; A. J. Heister ; D. Hoehn ; D. Kasperaviciute ; D. C. Liewald ; L. M. Lopez ; R. R. Makkinje ; M. Matarin ; M. A. Naber ; D. R. McKay ; M. Needham ; A. C. Nugent ; B. Putz ; N. A. Royle ; L. Shen ; E. Sprooten ; D. Trabzuni ; S. S. van der Marel ; K. J. van Hulzen ; E. Walton ; C. Wolf ; L. Almasy ; D. Ames ; S. Arepalli ; A. A. Assareh ; M. E. Bastin ; H. Brodaty ; K. B. Bulayeva ; M. A. Carless ; S. Cichon ; A. Corvin ; J. E. Curran ; M. Czisch ; G. I. de Zubicaray ; A. Dillman ; R. Duggirala ; T. D. Dyer ; S. Erk ; I. O. Fedko ; L. Ferrucci ; T. M. Foroud ; P. T. Fox ; M. Fukunaga ; J. R. Gibbs ; H. H. Goring ; R. C. Green ; S. Guelfi ; N. K. Hansell ; C. A. Hartman ; K. Hegenscheid ; A. Heinz ; D. G. Hernandez ; D. J. Heslenfeld ; P. J. Hoekstra ; F. Holsboer ; G. Homuth ; J. J. Hottenga ; M. Ikeda ; C. R. Jack, Jr. ; M. Jenkinson ; R. Johnson ; R. Kanai ; M. Keil ; J. W. Kent, Jr. ; P. Kochunov ; J. B. Kwok ; S. M. Lawrie ; X. Liu ; D. L. Longo ; K. L. McMahon ; E. Meisenzahl ; I. Melle ; S. Mohnke ; G. W. Montgomery ; J. C. Mostert ; T. W. Muhleisen ; M. A. Nalls ; T. E. Nichols ; L. G. Nilsson ; M. M. Nothen ; K. Ohi ; R. L. Olvera ; R. Perez-Iglesias ; G. B. Pike ; S. G. Potkin ; I. Reinvang ; S. Reppermund ; M. Rietschel ; N. Romanczuk-Seiferth ; G. D. Rosen ; D. Rujescu ; K. Schnell ; P. R. Schofield ; C. Smith ; V. M. Steen ; J. E. Sussmann ; A. Thalamuthu ; A. W. Toga ; B. J. Traynor ; J. Troncoso ; J. A. Turner ; M. C. Valdes Hernandez ; D. van 't Ent ; M. van der Brug ; N. J. van der Wee ; M. J. van Tol ; D. J. Veltman ; T. H. Wassink ; E. Westman ; R. H. Zielke ; A. B. Zonderman ; D. G. Ashbrook ; R. Hager ; L. Lu ; F. J. McMahon ; D. W. Morris ; R. W. Williams ; H. G. Brunner ; R. L. Buckner ; J. K. Buitelaar ; W. Cahn ; V. D. Calhoun ; G. L. Cavalleri ; B. Crespo-Facorro ; A. M. Dale ; G. E. Davies ; N. Delanty ; C. Depondt ; S. Djurovic ; W. C. Drevets ; T. Espeseth ; R. L. Gollub ; B. C. Ho ; W. Hoffmann ; N. Hosten ; R. S. Kahn ; S. Le Hellard ; A. Meyer-Lindenberg ; B. Muller-Myhsok ; M. Nauck ; L. Nyberg ; M. Pandolfo ; B. W. Penninx ; J. L. Roffman ; S. M. Sisodiya ; J. W. Smoller ; H. van Bokhoven ; N. E. van Haren ; H. Volzke ; H. Walter ; M. W. Weiner ; W. Wen ; T. White ; I. Agartz ; O. A. Andreassen ; J. Blangero ; D. I. Boomsma ; R. M. Brouwer ; D. M. Cannon ; M. R. Cookson ; E. J. de Geus ; I. J. Deary ; G. Donohoe ; G. Fernandez ; S. E. Fisher ; C. Francks ; D. C. Glahn ; H. J. Grabe ; O. Gruber ; J. Hardy ; R. Hashimoto ; H. E. Hulshoff Pol ; E. G. Jonsson ; I. Kloszewska ; S. Lovestone ; V. S. Mattay ; P. Mecocci ; C. McDonald ; A. M. McIntosh ; R. A. Ophoff ; T. Paus ; Z. Pausova ; M. Ryten ; P. S. Sachdev ; A. J. Saykin ; A. Simmons ; A. Singleton ; H. Soininen ; J. M. Wardlaw ; M. E. Weale ; D. R. Weinberger ; H. H. Adams ; L. J. Launer ; S. Seiler ; R. Schmidt ; G. Chauhan ; C. L. Satizabal ; J. T. Becker ; L. Yanek ; S. J. van der Lee ; M. Ebling ; B. Fischl ; W. T. Longstreth, Jr. ; D. Greve ; H. Schmidt ; P. Nyquist ; L. N. Vinke ; C. M. van Duijn ; L. Xue ; B. Mazoyer ; J. C. Bis ; V. Gudnason ; S. Seshadri ; M. A. Ikram ; N. G. Martin ; M. J. Wright ; G. Schumann ; B. Franke ; P. M. Thompson ; S. E. Medland
Nature Publishing Group (NPG)
Published 2015Staff ViewPublication Date: 2015-01-22Publisher: Nature Publishing Group (NPG)Print ISSN: 0028-0836Electronic ISSN: 1476-4687Topics: BiologyChemistry and PharmacologyMedicineNatural Sciences in GeneralPhysicsKeywords: Adolescent ; Adult ; Aged ; Aged, 80 and over ; Aging/genetics ; Apoptosis/genetics ; Brain/*anatomy & histology ; Caudate Nucleus/anatomy & histology ; Child ; Female ; Gene Expression Regulation, Developmental/genetics ; Genetic Loci/genetics ; Genetic Variation/*genetics ; *Genome-Wide Association Study ; Hippocampus/anatomy & histology ; Humans ; Magnetic Resonance Imaging ; Male ; Membrane Proteins/genetics ; Middle Aged ; Organ Size/genetics ; Putamen/anatomy & histology ; Sex Characteristics ; Skull/anatomy & histology ; Young AdultPublished by: -
2Latest Papers from Table of Contents or Articles in PressT. M. McDonald ; J. A. Mason ; X. Kong ; E. D. Bloch ; D. Gygi ; A. Dani ; V. Crocella ; F. Giordanino ; S. O. Odoh ; W. S. Drisdell ; B. Vlaisavljevich ; A. L. Dzubak ; R. Poloni ; S. K. Schnell ; N. Planas ; K. Lee ; T. Pascal ; L. F. Wan ; D. Prendergast ; J. B. Neaton ; B. Smit ; J. B. Kortright ; L. Gagliardi ; S. Bordiga ; J. A. Reimer ; J. R. Long
Nature Publishing Group (NPG)
Published 2015Staff ViewPublication Date: 2015-03-13Publisher: Nature Publishing Group (NPG)Print ISSN: 0028-0836Electronic ISSN: 1476-4687Topics: BiologyChemistry and PharmacologyMedicineNatural Sciences in GeneralPhysicsKeywords: Adsorption ; Amines/*chemistry ; Carbon Dioxide/*chemistry/*isolation & purification ; *Carbon Sequestration ; Greenhouse Effect/prevention & control ; Magnesium/metabolism ; Ribulose-Bisphosphate Carboxylase/chemistry/metabolism ; Temperature ; X-Ray DiffractionPublished by: -
3Articles: DFG German National LicensesStaff View
ISSN: 0014-5793Keywords: (Human) ; Ca^2^+ ; Inositol phosphate ; LymphocyteSource: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002Topics: BiologyChemistry and PharmacologyPhysicsType of Medium: Electronic ResourceURL: -
4Articles: DFG German National LicensesStaff View
ISSN: 1420-9071Source: Springer Online Journal Archives 1860-2000Topics: BiologyMedicineNotes: Zusammenfassung In der vorliegenden Arbeit wird ein Überblick über die Probleme gegeben, die bei der Interpretation der Wirkung von Substanzen auftreten, welche die passive Ionenpermeabilität der Erythrozytenmembran beeinflussen. Dabei wird besonderes Gewicht auf Hemmstoffe der Anionenpermeabilität gelegt. 1-Fluoro-2,4-Dinitrobenzol (DNBF) und 5-Methoxy-2-Nitrotropon (MNT) können mit Aminogruppen kovalente Bindungen eingehen. Beide Substanzen werden von der Erythrozytenmembran irreversibel gebunden. Sie hemmen die Permeabilität für Anionen und steigern sie für Kationen. Die Wirkung des MNT auf die Kationenpermeabilität wird allerdings nur sichtbar, wenn es zusammen mit einer nahezu hämolytischen Menge an Äthanol dem Inkubationsmedium zugesetzt wird. Die Beobachtungen stehen im Einklang mit der Hypothese, dass die Erythrozytenmembran ein Anionenaustauscher ist, in dem Aminogruppen als Träger der positiven Festladungen vorhanden sind. Schwieriger lässt sich die Hemmwirkung einer Reihe von Stoffen erklären, die nicht mit Aminogruppen reagieren können. Dinitrophenol und Benzoat hemmen den Sulfationenfluss nichtkompetitiv, ohne dabei eine Steigerung des Kaliumeffluxes herbeizuführen. Auch aliphatische Verbindungen, darunter primäre Alkohole und Amine, können die Anionenpermeabilität vermindern, wobei bereits ein deutlicher Hemmeffekt auftritt, bevor der Kaliumefflux vergrössert wird. Die einzige Gemeinsamkeit dieser chemisch sehr heterogenen Gruppe an Hemmstoffen ist der polar-apolare Charakter ihrer Moleküle, was zu einer Anreicherung dieser Stoffe an Grenzflächen zwischen Lipid und Wasser führen sollte. Die Beziehung zwischen Sulfatpermeabilität und Hemmstoffkonzentration lässt sich mit Hilfe einer einfachen, aus der Enzymkinetik bekannten Formel beschreiben. Zwischen dem gemessenen Sulfatfluss und der aufgrund der Festladungshypothese berechneten Sulfatkonzentration in der Membran besteht ein exponentieller Zusammenhang, der durch eine empirische Gleichung wiedergegeben werden kann. Mit Hilfe dieser Gleichung lässt sich der Anionenfluss auch in Gegenwart eines Hemmstoffes (Phenol) beschreiben, wobei sich nur eine der beiden empirischen Konstanten erheblich ändert. Die geschilderten Ergebnisse legen die Vermutung nahe, dass die Anionen bei der Penetration durch die Erythrozytenmembran mindestens zwei verschiedene, hintereinander geschaltete Permeabilitätsbarrieren überwinden müssen.Type of Medium: Electronic ResourceURL: -
5Articles: DFG German National LicensesStaff View
ISSN: 1432-1912Source: Springer Online Journal Archives 1860-2000Topics: MedicineDescription / Table of Contents: Summary 1. Homogenates from guinea-pig hearts were fractionated by differential centrifugation. The fractions obtained after removal of the low speed sediment 2000 g showed the following distribution of catecholamines: the sediment 15000 g contains 14%, the sediment 100000 g 49% and the supernatant 100000 g 37% of the catecholamines (adrenaline + noradrenaline). The catecholamine content per mg protein of sediment 100000 g is about 8 times as high as that of the other fraction. 2. 66% of the noradrenaline are stored in the granular fraction 100000 g. The ratio noradrenaline/protein in this fraction is at least 10 times as high as in the others. Adrenaline is unspecifically distributed to the fractions according to their protein content. 3. Pretreatment of the guinea-pigs with reserpine (4 μg/kg i.m.) causes after 20 hours a 70–80% decrease of the catecholamine content of the hearts. All fractions are equally depleted. 30 min after 100 μg/kg reserpine a 50% loss, 90 min after 500 μg/kg a 90% loss of catecholamines is observed affecting all fractions to the same degree. 4. The spontaneous release of catecholamines from isolated heart granules (sediment 100000 g) during incubation (45 min) is dependent on the temperature. At 0°C, 22°C and 37°C a release of 16%, 36% and 100% is observed. Under the same experimental conditions the release of catecholamines from nerve granules is 14.5%, 52.5% and 100%, from medullary granules 3.2%, 8.5% and 22% respectively. Heart granules loose under osmotic lysis with water (0°C, 10 min) 31%, medullary granules 94% of their original catecholamine content. 5. Calcium (5–50 μMol/ml) and magnesium (20 μMol/ml) do not enhance the catecholamine release either from heart or from nerve granules (incubation 45 min, 0°C and 22°C). On the contrary these cations release catecholamines from medullary granules at both temperatures. 6. Ribonuclease (1 mg/ml) and segontin lactate (30–300 μg/ml) release at 22°C catecholamines from heart, nerve and medullary granules as well. 7. The properties of granules from heart, splenic nerves and suprarenal medulla are compared. The similarities between heart and nerve granules lead to the conclusion that heart granules originate from the postganglionic sympathetic nerves of the heart.Notes: Zusammenfassung 1. Homogenate von Meerschweinchenherzen wurden durch Differentialzentrifugieren fraktioniert. Läßt man das grobpartikuläre Sediment 2000 g unberücksichtigt, so erhält man folgende Verteilung der Gesamtbrenzcatechinamine (Adrenalin + Noradrenalin) auf die einzelnen Fraktionen: Sediment 15000 g enthält 14%, Sediment 100000 g 49% und der Überstand 100000 g 37%. Auf mg Eiweiß berechnet enthält Sediment 100000 g etwa achtmal mehr Amine als die anderen Fraktionen. 2. Noradrenalin wird zu 66% in der Granulafraktion 100000 g gespeichert, der Noradrenalin-Eiweißquotient in dieser Fraktion ist mindestens zehnmal so hoch wie in den anderen Fraktionen. Adrenalin ist unspezifisch auf die einzelnen Fraktionen verteilt, dem Eiweißgehalt entsprechend. 3. Durch Vorbehandlung der Meerschweinchen mit Reserpin kommt es in Abhängigkeit von der Dosis und der Vorbehandlungszeit zu einer 50–90% igen Abnahme der Brenzcatechinamine des Herzens, die alle Fraktionen gleichmäßig betrifft. Die nach Guanethidin auftretende Verarmung von ca. 40% betrifft ebenfalls alle Fraktionen prozentual gleich stark. 4. Aus Suspensionen isolierter Herzgranula (Sediment 100000 g) in isotonischer Saccharoselösung werden bei Inkubation (45 min) in Abhängigkeit von der Temperatur Brenzcatechinamine freigesetzt, bei 0, 22 bzw. 37°C 16, 36 bzw. 100%. Unter den gleichen Versuchsbedingungen ist die Aminfreisetzung aus isolierten Nervengranula etwa gleich groß, während diejenige aus isolierten Nebennierenmarkgranula wesentlich geringer ist. Durch osmotische Lyse mit Aqua dest. (0° C, 10 min) verlieren Herzgranula 31%, Nebennierenmarkgranula 94% ihrer Amine. 5. Aus isolierten Herz- und Nervengranula läßt sich durch Inkubation mit Calcium und Magnesium sowohl bei 22° C als auch bei 0° C im Gegensatz zu Nebennierenmarkgranula keine Steigerung der Brenzcatechinaminabgabe erzielen. 6. Ribonuclease und Segontinlactat setzen bei 22°C aus Herz-, Nerven- und Nebennierenmarkgranula Amine frei. 7. Das unterschiedliche Verhalten von Herz-, Nerven- und Nebennierenmarkgranula wird diskutiert und der Schluß gezogen, daß die Herzgranula (Sediment 100000 g) im wesentlichen Granula aus postganglionären, sympathischen Nerven sind.Type of Medium: Electronic ResourceURL: -
6Articles: DFG German National LicensesStaff View
ISSN: 1432-2013Keywords: Sulfate ; Phosphate ; Transport ; Erythrocyte ghostsSource: Springer Online Journal Archives 1860-2000Topics: MedicineNotes: Abstract The concentration dependence of the sulfate and the phosphate selfexchange and homoexchange fluxes was studied in resealed red cell ghosts (25° C, pH 7.3). The selfexchange fluxes were calculated from the rate constant of the tracer back-exchange and from the intracellular substrate anion content. The homoexchange fluxes were determined from the initial cis-to-trans tracer fluxes and the initial specific substrate anion activities at the cis-membrane side. Sulfate and phosphate concentrations ranging from approx. 2–100 mM were employed. The selfexchange fluxes of sulfate and of phosphate exhibit sigmoidal flux/concentration curves. The apparent Hill coefficients were in the range of 1.2–1.4 indicating a type of positive cooperativity. Under homoexchange conditions the positive cooperativity of the flux/concentration curves disappears. The outward homoexchange fluxes of sulfate and phosphate display a saturation kinetics with Hill coefficients close to 1.0. The inward homoexchange fluxes exhibit a negative type of cooperativity with Hill coefficients smaller than 1.0. The sulfate and the phosphate half-saturation concentrations for the outer and the inner membrane surface are equal in size and amount to approx. 35 mM for sulfate and to approx. 110 mM for phosphate, respectively. The positive cooperativity of the unidirectional sulfate and phosphate fluxes under selfexchange conditions and the disappearance of the positive cooperativity under homoexchange conditions indicate a cooperativity of the translocation process. The saturation of the outward homoexchange flux and the negative cooperativity of the inward homoexchange flux suggest a substrate anion binding according to the law of mass action at the inner and a negative cooperativity of substrate anion binding at the outer membrane surface.Type of Medium: Electronic ResourceURL: -
7Articles: DFG German National LicensesStaff View
ISSN: 1432-2013Keywords: Chloride ; Transport ; Erythrocyte ghostsSource: Springer Online Journal Archives 1860-2000Topics: MedicineNotes: Abstract The concentration dependence of the unidirectional chloride flux in human red cell ghosts was studied under selfexchange and under homoexchange conditions. Under selfexchange conditions the intracellular concentration of chloride [Cl]in is equal to the extracellular concentration [Cl]ex and [Cl]in and [Cl]ex are raised concomitantly. Under homoexchange conditions [Cl]in or [Cl]ex were varied separately at a fixed trans-concentration of chloride. The chloride fluxes were calculated from the rate of the tracer efflux and the intracellular chloride. All experiments were executed in isotonic (330 mosM) KCl/K-citrate/sorbitol solutions containing 0–100 mM KCl, 40 mM K-citrate and different concentrations of sorbitol for isoosmotic substitution. The chloride selfexchange and the chloride homoexchange fluxes exhibit a pure saturation kinetics. The halfsaturation constant for the chloride selfexchange was ∼ 20 mM, the maximal flux was approx. 3.5·10−4 mol/(min g cells). The apparent chloride halfsaturation constants from the homoexchange experiments were in the range of 0.9–4.5 mM for the outer and of 5.5–14.5 mM (0° C, pH 7.3) for the inner membrane surface, both halfsaturation constants increase with increasing trans-concentrations. At infinite trans-concentrations of chloride, the halfsaturation constant for the outer and the inner membrane surface amounts to ∼ 5 mM and ∼ 15 mM, respectively. The slope of the double reciprocal plots of flux versus cis-chloride concentration decreases with increasing trans-concentration of chloride. The kinetics of the chloride transport provides evidence for a carrier mediated transport mechanism with a single reciprocating transport site. The translocation of the loaded carrier appears to be much faster than the translocation of the unloaded carrier. At low concentrations of chloride, however, the slippage of the empty carrier seems to contribute to the back-diffusion of carrier to the cis-side of the membrane.Type of Medium: Electronic ResourceURL: -
8Articles: DFG German National LicensesStaff View
ISSN: 1432-2013Keywords: DMO-transport ; ErythrocytesSource: Springer Online Journal Archives 1860-2000Topics: MedicineNotes: Abstract The DMO (5,5-dimethyloxazolidine-2,4-dione) transport was studied in human red blood cells by measuring the14C-DMO back exchange under self exchange conditions from14C-DMO labeled cells at 0°C. The unidirectional DMO-flux was linearly related to the DMO concentration up to approx. 100 mM. The unidirectional DMO-flux increases as pH is reduced. The DMO transport is not inhibited by anion transport inhibitors like DIDS, SITS, dipyridamole, phlorhizin, salicylate or butanol. A close correlation between the unidirectional DMO-flux and DMOH, the unionized form of DMO, has been observed suggesting that DMO is transported predominantly by nonionic diffusion. The permeability of DMOH is 9.5·10−6 cm/s (0°C) while the permeability of DMO− cannot be assessed from our data.Type of Medium: Electronic ResourceURL: -
9Articles: DFG German National LicensesStaff View
ISSN: 1432-1424Source: Springer Online Journal Archives 1860-2000Topics: BiologyChemistry and PharmacologyNotes: Summary The anion transport across the red blood cell membrane is assumed to occur by ionic diffusion through dielectric pores which are formed by protein molecules spanning the red blood cell membrane. The access of anions to the dielectric pores is regulated by anion adsorption sites positioned at the entrances of the pores. The adsorption of small inorganic anions to the adsorption sites is facilitated by ionizing cationic groups setting up a surface potential at the respective membrane surfaces. Applying the transition state theory of rate processes, flux equations for the unidirectional flux were derived expressing the unidirectional flux as a function of the fractional occupancies of anion adsorption sites at both membrane surfaces. The basic properties of the transport model were investigated. The concentration-dependence and the pH-dependence of the unidirectional fluxes were shown to depend upon the surface charge density and upon the affinity of the transported anion species to the anion binding sites. The concentration-response and the pH-response of the unidirectional fluxes of different anion species may differ substantially even if the anion species are transported by the same anion transport system. The model predicts a characteristic behavior of the Lineweaver-Burk plot and of the Dixon plot. A comparison between computer simulated and experimentally determined flux curves was made. By choosing a suitable set of parameters, the anion transport model is capable of simulating the concentration-dependencies and the pH-dependencies of the unidirectional sulfate and chloride flux. It is sufficient to change one single constant in order to convert the “sulfate transport system” into a “chloride transport system”. Furthermore, the model is capable of predicting the inhibitory action of chloride on the sulfate transport system. No attempts were made to fit the experimental data to the model. The behavior of the model was qualitatively in accordance with the experimental results.Type of Medium: Electronic ResourceURL: -
10Articles: DFG German National LicensesStaff View
ISSN: 1432-1424Source: Springer Online Journal Archives 1860-2000Topics: BiologyChemistry and PharmacologyNotes: Summary The sulfate and the chloride self-exchange fluxes were determined by measuring the rate of the tracer efflux from radioactively labeled human red blood cells and red blood cell ghosts. The concentration dependence and the pH-dependence of the sulfate self-exchange flux were studied. In addition, the effects of some monovalent and divalent anions on the sulfate and the chloride self-exchange fluxes were investigated. The sulfate self-exchange fluxes saturate, exhibiting a concentration maximum at sulfate concentrations between 100 and 300mm (25°C). The position of the concentration maximum depends upon pH. At high sulfate concentrations a self-inhibition of the flux becomes apparent. The apparent half-saturation constant and the apparent self-inhibition constant at pH 7.2 were 30mm and 400mm respectively. Within the pH range of 6.3–8.5, both constants decreased with increasing pH. No saturation of the sulfate self-exchange flux was observed if the sulfate concentration was raised by substituting sulfate for isoosmotic amounts of a second salt (NaCl, NaNO3, Na-acetate, Na-lactate, Na-succinate or Na2HPO4). Red blood cells and red blood cell ghosts display the same pattern of concentration responsiveness. The sulfate self-exchange flux exhibits a pH-maximum at about pH 6.2 (37°C). The location of the pH-maximum is little affected by variations of the sulfate concentration. The logarithmic plots (log $$\vec J_{SO_4 } $$ vs. pH) revealed that the flux/pH relation can be approximated by two straight lines. The slopes of the alkaline branches of the flux/pH curves range from −0.55 to −0.86, the slopes of the branches of the curves range from 0.08 to 1.14 and were strongly affected by changes of the sulfate concentrations. The apparent pK's obtained from the alkaline and from the acidic branches of the flux/pH curves were about 7.0 and 6.0, respectively. Intact red blood cells and red blood cell ghosts display the same type of pH-dependency of the sulfate self-exchange flux. The sulfate self-exchange flux is competitively inhibited by nitrate, chloride, acetate, oxalate and phosphate. The chloride self-exchange flux is competitively inhibited by thiocyanate, nitrate, sulfate and phosphate. The inhibition constants for the various anion species increase in the given sequence. The results of our studies indicate that the sulfate self-exchange flux is mediated by a “two-site transport mechanism” consisting either of a mobile carrier or a two-site pore. The experiments reported in this paper do not permit distinguishing between both transport mechanisms. The similarities of the sulfate and the chloride self-exchange flux and the mutual competition between sulfate and chloride point to a common transport system for both anion species.Type of Medium: Electronic ResourceURL: -
11Articles: DFG German National LicensesStaff View
ISSN: 1432-1424Keywords: anion transport ; erythrocyte ; spin labeling ; Band 3Source: Springer Online Journal Archives 1860-2000Topics: BiologyChemistry and PharmacologyNotes: Summary NDS-TEMPO is a specific disulfonatostilbene spin label for the Band 3 substrate site (K. F. Schnell, W. Elbe, J. Käsbauer & E. Kaufmann,Biochim. Biophys. Acta 732:266–275, 1983). The pH dependence of NDS-TEMPO binding and of chloride and sulfate binding was studied in resealed human erythrocyte ghosts. pH was varied from 6.0 to 9.0. The ESR spectra from NDS-TEMPO-labeled red cell ghosts exhibited a strong immobilization of membrane-bound NDS-TEMPO. Changes of pH had no effect upon the mobility of membrane-bound NDS-TEMPO. A mutual competition between NDS-TEMPO binding and the binding of the substrate-anions, chloride and sulfate, was observed throughout the entire pH range. The maximal number of NDS-TEMPO binding sites per cell was in the range of 9.0×105 to 1.10×106 and was found to be insusceptible to changes of pH. The NDS-TEMPO/substrate-site and the chloride/substratesite dissociation constants amounted to 1.25 μm and to 17mm and were independent of pH from pH 6.0 to 8.0, while the sulfate/substrate-site dissociation constant displayed a strong pH dependency with a maximum of ∼50mm at about pH 7.0. The NDS-TEMPO inhibition constants from the chloride and the sulfate flux experiments were 0.5 μm (0°C) and 1.8 μm (25°C), respectively, and are in close accordance with the NDS-TEMPO/substrate-site dissociation constants. Our studies provide strong evidence for the assumption that NDS-TEMPO binds in fact to the substrate site of Band 3. They show that the strong pH dependence of the chloride and of the sulfate transport cannot result from the pH dependency of substrate-anion binding, but point to the participation of ionizable regulator sites in transport catalysis. These regulator sites seem to be positioned outside the substrate site of the Band 3 transport domain.Type of Medium: Electronic ResourceURL: -
12Articles: DFG German National LicensesStaff View
ISSN: 1432-1424Keywords: phosphate ; transport ; erythrocytes ; humanSource: Springer Online Journal Archives 1860-2000Topics: BiologyChemistry and PharmacologyNotes: Summary The phosphate self-exchange flux in resealed erythrocyte ghosts and in amphotericin B (5.5 μm) permeabilized erythrocytes has been studied. The phosphate self-exchange flux exhibits an S-shaped concentration dependence and a self-inhibition in permeabilized red cells while in erythrocyte ghosts no self-inhibition of the phosphate flux has been observed. The apparent halfsaturation constants and the apparent Hill coefficients were assessed by the double reciprocal Hill plots of $$1/\vec J_p$$ versus 1/[P] n . The phosphate half-saturation constants amount to approx. 125mm in ghosts and to about 75mm in permeabilized cells while the apparent Hill coefficients amount to 1.15 and to 1.65 (pH 7.2, 25°C), respectively. Both chloride and sulfate elicit a mixed-type inhibition of the phosphate self-exchange flux. In permeabilized cells, chloride and sulfate shift the flux optimum towards higher phosphate concentrations and reduce the apparent Hill coefficients. In erythrocyte ghosts, the apparent Hill coefficients are insensitive to these anions. The double reciprocal Hill plots indicate a mixed-type inhibition of the phosphate self-exchange flux by DNDS, salicylate and dipyridamole and a noncompetitive inhibition of the phosphate self-exchange flux by phlorhizin. By contrast, the Hill-Dixon plots for chloride and sulfate indicate a competitive inhibition of the phosphate self-exchange flux in erythrocyte ghosts and a mixed-type inhibition in permeabilized cells and provide Hill coefficients of greater than unity for chloride and sulfate. The Dixon plots for DNDS, salicylate, phlorhizin and dipyridamole show a noncompetitive inhibition of the phosphate flux and provide apparent Hill coefficients of 0.95–1.0 for inhibitor binding. Using the Debye-Hückel theory, the effects of ionic strength upon phosphate transport and inhibitor binding can be eliminated. The results of our studies provide strong evidence for the assumption that electrostatic forces are involved in phosphate transport and in inhibitor binding.Type of Medium: Electronic ResourceURL: -
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ISSN: 1432-1424Keywords: Erythrocyte membrane ; phosphate transport ; anion permeability ; transport kineticsSource: Springer Online Journal Archives 1860-2000Topics: BiologyChemistry and PharmacologyNotes: Summary The concentration dependence and the pH dependence of the phosphate transport across the red cell membrane were investigated. The unidirectional phosphate fluxes were determined by measuring the32P-phosphate self-exchange in amphotericin B (5 μmol/liter) treated erythrocytes at 25°C. The flux/concentration curves display anS-shaped increase at low phosphate concentrations, a concentration optimum in the range of 150 to 200mm phosphate and a self-inhibition at high phosphate concentrations. The apparent half-saturation concentrations,P (0.5), range from 50 to 70mm and are little affected by pH. The self-inhibition constants, as far as they can be estimated, range from 400 to 600mm. The observed maximal phosphate fluxes exhibit a strong pH dependence. At pH 7.2, the actual maximal flux is 2.1×10−6 moles·min−1·g cells−1. The ascending branches of the flux/concentration curves were fitted to the Hill equation. The apparent Hill coefficients were always in the range of 1.5–2.0. The descending branches of the flux/concentration curves appear to follow the same pattern of concentration response. The flux/pH curves were bell-shaped and symmetric with regard to their pH dependence. The pH optimum is at approximately pH 6.5–6.7. The apparent pK of the activator site is in the range of 7.0 to 7.2, while the apparent pK for the inactivating site is in the range of 6.2 to 6.5. The pK-values were not appreciably affected by the phosphate concentration. According to our studies, the transport system possesses two transport sites and probably two modifier sites as indicated by the apparent Hill coefficients. In addition, the transport system has two proton binding sites, one with a higher pK that activates and one with a lower pK that inactivates the transport system. Since our experiments were executed under self-exchange conditions, they do not provide any information concerning the location of these sites at the membrane surfaces.Type of Medium: Electronic ResourceURL: