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  • 1
    Unknown
    The Hydrogeology of Crystalline Basement Aquifers in Africa (1992)
    London : The Geological Society
    Details
    Keywords: Grundwasserleiter ; Hydrogeologie ; Kristallines Gestein ; Africa ; Aquifers ; Aquifères - Afrique ; Hidrogeologia ; Hydrogéologie - Afrique ; Rocks, Crystalline
    Description / Table of Contents: E. P. Wright: The hydrogeology of crystalline basement aquifers in Africa / Geological Society, London, Special Publications, 66:1-27, doi:10.1144/GSL.SP.1992.066.01.01 --- R. M. Key: An introduction to the crystalline basement of Africa / Geological Society, London, Special Publications, 66:29-57, doi:10.1144/GSL.SP.1992.066.01.02 --- F. A. K. Farquharson and A. Bullock: The hydrology of basement complex regions of Africa with particular reference to southern Africa / Geological Society, London, Special Publications, 66:59-76, doi:10.1144/GSL.SP.1992.066.01.03 --- D. Greenbaum: Structural influences on the occurrence of groundwater in SE Zimbabwe / Geological Society, London, Special Publications, 66:77-85, doi:10.1144/GSL.SP.1992.066.01.04 --- Eduard Boeckh: An exploration strategy for higher-yield boreholes in the West African crystalline basement / Geological Society, London, Special Publications, 66:87-100, doi:10.1144/GSL.SP.1992.066.01.05 --- M. J. McFarlane: Groundwater movement and water chemistry associated with weathering profiles of the African surface in parts of Malawi / Geological Society, London, Special Publications, 66:101-129, doi:10.1144/GSL.SP.1992.066.01.06 --- M. J. McFarlane, P. J. Chilton, and M. A. Lewis: Geomorphological controls on borehole yields: a statistical study in an area of basement rocks in central Malawi / Geological Society, London, Special Publications, 66:131-154, doi:10.1144/GSL.SP.1992.066.01.07 --- J. R. T. Hazell, C. R. Cratchley, and C. R. C. Jones: The hydrogeology of crystalline aquifers in northern Nigeria and geophysical techniques used in their exploration / Geological Society, London, Special Publications, 66:155-182, doi:10.1144/GSL.SP.1992.066.01.08 --- R. D. Barker, C. C. White, and J. F. T. Houston: Borehole siting in an African accelerated drought relief project / Geological Society, London, Special Publications, 66:183-201, doi:10.1144/GSL.SP.1992.066.01.09 --- R. M. Carruthers and I. F. Smith: The use of ground electrical survey methods for siting water-supply boreholes in shallow crystalline basement terrains / Geological Society, London, Special Publications, 66:203-220, doi:10.1144/GSL.SP.1992.066.01.10 --- R. Herbert, J. A. Barker, and R. Kitching: New approaches to pumping test interpretation for dug wells constructed on hard rock aquifers / Geological Society, London, Special Publications, 66:221-242, doi:10.1144/GSL.SP.1992.066.01.11 --- John Houston: Rural water supplies: comparative case histories from Nigeria and Zimbabwe / Geological Society, London, Special Publications, 66:243-257, doi:10.1144/GSL.SP.1992.066.01.12
    Pages: Online-Ressource (VII, 264 Seiten) , Diagramme, Karten
    ISBN: 090331777X
    URL: http://sp.lyellcollection.org/content/66/1
    Language: English
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  • 2
    Electronic Resource
    Electronic Resource
    Multipurpose Method of Spectrographic Analysis. Sodium Nitrate Matrix and Alternating Current Arc Excitation (1950)
    s.l. : American Chemical Society
    Analytical chemistry 22 (1950), S. 1516-1518 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac60048a014
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  • 3
    Electronic Resource
    Electronic Resource
    Separation of Calcium from Magnesium (1949)
    s.l. : American Chemical Society
    Analytical chemistry 21 (1949), S. 596-597 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac60029a020
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  • 4
    Electronic Resource
    Electronic Resource
    The number of graphs on many unlabelled nodes (1969)
    Springer
    Mathematische Annalen 183 (1969), S. 250-253 
    Details
    ISSN: 1432-1807
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01350794
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  • 5
    Electronic Resource
    Electronic Resource
    Kinetics and specificity of the renal Na+/myo-inositol cotransporter expressed in Xenopus Oocytes (1995)
    Springer
    The journal of membrane biology 143 (1995), S. 103-113 
    Details
    ISSN: 1432-1424
    Keywords: Na+/myo ; inositol cotransport ; Na+/glucose cotransport ; Kinetics ; Electrophysiology ; Xenopus oocytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The two-microelectrode voltage clamp technique was used to examine the kinetics and substrate specificity of the cloned renal Na+/myo-inositol cotransporter (SMIT) expressed in Xenopus oocytes. The steady-state myo-inositol-induced current was measured as a function of the applied membrane potential (V m ), the external myo-inositol concentration and the external Na+ concentration, yielding the kinetic parameters: K 0.5 MI , K 0.5 Na , and the Hill coefficient n. At 100 mM NaCl, K 0.5 MI was about 50 μm and was independent of V m . At 0.5 mm myo-inositol, K 0.5 Na ranged from 76 mm at V m =−50 mV to 40 mm at V m =−150 mV. n was voltage independent with a value of 1.9±0.2, suggesting that two Na+ ions are transported per molecule of myo-inositol. Phlorizin was an inhibitor with a voltage-dependent apparent K I of 64 μm at V m =−50 mV and 130 μm at V m = −150 mV. To examine sugar specificity, sugar-induced steady-state currents (at V m =−150 mV) were recorded for a series of sugars, each at an external concentration of 50 mm. The substrate selectivity series was myo-inositol, scyllo-inositol 〉 l-fucose 〉 l-xylose 〉 l-glucose, d-glucose, α-methyl-d-glucopyranoside 〉 d-galactose, d-fucose, 3-O-methyl-d-glucose, 2-deoxy-d-glucose 〉 d-xylose. For comparison, oocytes were injected with cRNA for the rabbit intestinal Na+/glucose cotransporter (SGLT1) and sugar-induced steady-state currents (at V m =−150 mV) were measured. For oocytes expressing SGLT1, the sugar selectivity was: d-glucose, α-methyl-d-glucopyranoside, d-galactose, d-fucose, 3-O-methyl-d-glucose 〉 d-xylose, l-xylose, 2-deoxy-d-glucose 〉 myo-inositol, l-glucose, l-fucose. The ability of SMIT to transport glucose and SGLT1 to transport myo-inositol was independently confirmed by monitoring the Na+-dependent uptake of 3H-d-glucose and 3H-myo-inositol, respectively. In common with SGLT1, SMIT gave a relaxation current in the presence of 100 mm Na+ that was abolished by phlorizin (0.5 mm). This transient current decayed with a voltage-sensitive time constant between 10 and 14 msec. The presteady-state current is apparently due to the reorientation of the cotransporter protein in the membrane in response to a change in V m . The kinetics of SMIT is accounted for by an ordered six-state nonrapid equilibrium model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00234656
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  • 6
    Electronic Resource
    Electronic Resource
    A method for determining the unitary functional capacity of cloned channels and transporters expressed in Xenopus laevis oocytes (1995)
    Springer
    The journal of membrane biology 148 (1995), S. 65-78 
    Details
    ISSN: 1432-1424
    Keywords: Freeze-fracture ; Plasma membranes ; Heterologous expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The Xenopus laevis oocyte is widely used to express exogenous channels and transporters and is well suited for functional measurements including currents, electrolyte and nonelectrolyte fluxes, water permeability and even enzymatic activity. It is difficult, however, to transform functional measurements recorded in whole oocytes into the capacity of a single channel or transporter because their number often cannot be estimated accurately. We describe here a method of estimating the number of exogenously expressed channels and transporters inserted in the plasma membrane of oocytes. The method is based on the facts that the P (protoplasmic) face in water-injected control oocytes exhibit an extremely low density of endogenous particles (212±48 particles/μm2, mean, sd) and that exogenously expressed channels and transporters increased the density of particles (up to 5,000/μm2) only on the P face. The utility and generality of the method were demonstrated by estimating the “gating charge” per particle of the Na+/ glucose cotransporter (SGLT1) and a nonconducting mutant of the Shaker K+ channel proteins, and the single molecule water permeability of CHIP (Channel-like Intramembrane Protein) and MIP (Major Intrinsic Protein). We estimated a “gating charge” of ∼3.5 electronic charges for SGLT1 and ∼9 for the mutant Shaker K+ channel from the ratio of Q max to density of particles measured on the same oocytes. The “gating charges” were 3-fold larger than the “effective valences” calculated by fitting a Boltzmann equation to the same charge transfer data suggesting that the charge movement in the channel and cotransporter occur in several steps. Single molecule water permeabilities (p f s) of 1.4 × 10−14 cm3/ sec for CHIP and of 1.5 × 10−16 cm3/sec for MIP were estimated from the ratio of the whole-oocyte water permeability (P f ) to the density of particles. Therefore, MIP is a water transporter in oocytes, albeit ∼100-fold less effective than CHIP.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00234157
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  • 7
    Electronic Resource
    Electronic Resource
    Phenylglucosides and the Na+/glucose cotransporter (SGLT1): Analysis of interactions (1994)
    Springer
    The journal of membrane biology 142 (1994), S. 161-170 
    Details
    ISSN: 1432-1424
    Keywords: Na+/glucose cotransporter ; Xenopus oocytes ; Phenylglucosides ; Voltage clamp ; Kinetics ; Molecular modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Phenylglucosides are transported by the intestinal Na+/glucose cotransporter (SGLT1) and phlorizin, the classical competitive inhibitor of SGLT1, is also a phenylglucoside. To investigate the structural requirements for binding of substrates to SGLT1, we have studied the interactions between phenylglucosides and the cotransporter expressed in Xenopus oocytes using tracer uptake and electrophysiological methods. Some phenylglucosides inhibited the Na+-dependent uptake of 14C-α-methyl-d-glucopyranoside (αMDG) with apparent K is in the range 0.1 to 20 mm, while others had no effect. Electrophysiological experiments indicated that phenylglucosides can act either as: (1) transported substrates, e.g., arbutin; (2) nontransported inhibitors, e.g., glucosylphenyl-isothiocyanate; or (3) noninteracting sugars, e.g., salicin. The transported substrates (glucose, arbutin, phenylglucoside and helicin) induced different maximal currents, and computer simulations showed that this may be explained by a difference in the translocation rates of the sugar and Na+-loaded transporter. Computational chemistry indicated that all these β-phenylglucosides have similar 3-D structures. Analysis showed that among the side chains in the para position of the phenyl ring the -OH group (arbutin) facilitates transport, but the-NCS (glucosylphenyl-isothiocyanate) inhibits transport. In the ortho position, -CH2OH (salicin) prevents interaction, but the aldehyde (helicin) permits the molecule to be transported. Studies such as these may help to understand the geometry and nature of glucoside binding to SGLT1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00234938
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  • 8
    Electronic Resource
    Electronic Resource
    Highly purified basal lateral plasma membranes from rat duodenum. Physical criteria for purity (1979)
    Springer
    The journal of membrane biology 50 (1979), S. 343-363 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Preparations of intestinal epithelial cell basal lateral plasma membranes were analyzed with free flow electrophoresis and density pertubation with digitonin. The initial basal lateral membrane preparations were obtained by equilibrium density gradient centrifugation after two different schemes of homogenization and differential sedimentation (A.K. Mircheff, C.H. van Os, and E.M. Wright. 1978.Membr. Biochem. 1: 177, and A.K. Mircheff, S.D. Hanna, M.W. Walling, and E.M. Wright. 1979.Prep. Biochem. 9:33. In these preparations, Na,K-ATPase, a marker for the basal lateral mambrane, was purified 16- to 18-fold over the initial homogenate. The preparations were also enriched in NADPH-cytochromec reductase, alkaline phosphatase, acid phosphatase, and galactosylstransferase. Both free-flow electrophoresis, which separates on the basis of surface charge, and density perturbation with digitonin, which depends on a specific interaction of digitonin with cholesterol-rich membranes, resolved the preparation into three populations of particles. The major population, which represented basal lateral membranes purified 20- to 32-fold with respect to the initial homogenate, contained Na,K-ATPase, alkaline phosphatase, adenylate cyclase, and acid phosphatase. A second population was defined by its content of NADPH-cytochromec reductase, and the third was defined by its content of galactosyltransferase. Guanylate cyclase appeared to be partitioned between the Na,K-ATPase-rich and NADPH-cytochromec reductase-rich populations. Galactosyltransferase is also present in fractions which contain the Na,K-ATPase-rich membranes, but the present data cannot exclude the possibility of spillovers by the adjacent, galactosyltransferase-rich population. This work emphasize the importance of multiple, physical criteria for purity in the isolation of subcellular components.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01868897
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  • 9
    Electronic Resource
    Electronic Resource
    Histidyl residues at the active site of the Na/succinate cotransporter in rabbit renal brush borders (1984)
    Springer
    The journal of membrane biology 81 (1984), S. 159-170 
    Details
    ISSN: 1432-1424
    Keywords: renal brush border membranes ; carboxylic acid transport ; glucose transport ; Na-coupled cotransport ; histidyl, sulfhydryl, tyrosyl and tryptophanyl residues
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Mono-, dicarboxylic acid-, andd-glucose transport were measured in brush border vesicles from renal cortex after treatment with reagents known to modify terminal amino, lysyl, ɛ-amino, guanidino, serine/threonine, histidyl, tyrosyl, tryptophanyl and carboxylic residues. All three sodium-coupled cotransport systems proved to possess sulfhydryl (and maybe tryptophanyl sulfhydryl, disulfide, thioether and tyrosyl) residues but not at the substrate site or at the allosteric cavity for the Na coion. Histidyl groups seem to be located in the active site of the dicarboxylic transporter in that the simultaneous presence of Na and succinate protects the transporter against the histidyl specific reagent diethylpyrocarbonate. Lithium, which specifically competes for sodium sites in the dicarboxylic acid transporter, substantially blocked the protective effect of Na and succinate. Hydroxylamine specifically reversed the covalent binding of diethylpyrocarbonate to the succinate binding site. The pH dependence of the Na/succinate cotransport is consistent with an involvement of histidyl and sulfhydryl residues. We conclude that a histidyl residue is at, or is close to, the active site of the dicarboxylate transporter in renal brush border membranes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01868980
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  • 10
    Electronic Resource
    Electronic Resource
    Theory I (1982)
    Springer
    Applied physics 28 (1982), S. 163-171 
    Details
    ISSN: 1432-0649
    Keywords: 42.50
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00697842
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