No description available.

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No description available.

no abstract provided by author / Master of Science

Call number: LD2668 .T4 1955 W43 / Master of Science

Organic cations (OC's) are actively secreted by the renal proximal tubules in a number of species. The transepithelial transport of OC's involves a secondary active OC/H+ exchange process at the brush border (luminal) membrane. This study employed rabbit renal brush border membrane vesicles (BBMV) to investigate the structural requirements associated with substrate recognition at the OC transporter. A number of compounds (an N-alkylammonium series, an N1-alkylpyridinium series and some clinically important organic bases) were tested for their ability to competitively block the uptake of radioactively labelled tetraethylammonium (TEA) into BBMV. The inhibitory effectiveness of these compounds was correlated to the degree of hydrophobicity surrounding the positively-charged nitrogenous nucleus common to all the inhibitors. Preloading BBMV with N1-substituted pyridines trans-stimulated the uptake of TEA, suggesting that these compounds are translocated substrates for the OC transporter. The activity of the OC transport inhibitor and neurotoxin 1-methyl-4-phenylpyridinium was of special interest, and thus its transport characteristics were fully evaluated.

No description available.

L’étude de l’adsorption et de la mobilité des ions dans les argiles est importante pour mieux appréhender de nombreux processus géochimiques et environnementaux, de même que pour prédire le comportement des radionucléides dans les conditions du stockage géologique. A cause de leurs tailles très petites (< 2μm), il n’est pas toujours évident d’étudier les argiles à l’aide des méthodes et techniques expérimentales existantes. L’une des alternatives à ce problème consiste alors à utiliser la modélisation moléculaire pour les étudier. En plus de leurs tailles fines, les argiles présentent également des structures complexes, qui peuvent survenir en raison de la multiplicité de possibilités de distributions et d’arrangements des substitutions isomorphiques dans leurs couches. Il a été clairement démontré qu’il existe une corrélation entre la distribution des substitutions dans les couches des argiles et les propriétés de ces dernières. En revanche, ceci reste à démontrer en ce qui concerne l’arrangement de ces substitutions dans les couches de l’argile. Dans ce travail, la modélisation moléculaire est utilisée pour déterminer et comparer les propriétés d’hydratation, ainsi que la structure et la mobilité des ions (Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Ni²⁺, UO₂²⁺) et de l’eau dans l’espace interfoliaire de trois modèles de montmorillonite, différents entre eux par l’arrangement des substitutions isomorphiques dans les couches de l’argile.L’adsorption et la diffusion des cations cités plus haut et de l’eau sont également étudiées à la surface de la montmorillonite et les résultats sont comparés à ceux obtenus dans l’espace interfoliaire à 298 K et à 363 K. Les résultats obtenus dans ce travail s’accordent bien avec les observations expérimentales, et font ressortir une corrélation plus ou moins importante entre le modèle d’argile utilisé et le type de propriété calculée. Cette corrélation dépend également de la nature du cation présent dans la structure de la montmorillonite et de sa teneur en eau. / The study of adsorption and ion mobility in clay minerals is important for a better understanding of many geochemical and environmental processes, as well as to predict the behavior of radionuclides in geological storage conditions. Because of their very small size (<2μm), it is not always easy to study clays by using the existing experimental methods and techniques. One alternative to this issue is to use computational molecular modeling to carry out clay studies. In addition to their tiny size, clays minerals also have complex structures, which can appear due to various possibilities in the distribution and arrangement of isomorphic substitutions in their layers. It has been clearly demonstrated that there is a strong correlation between the distribution of substitutions in the clay layers and their properties. However, this remains to be shown regarding the arrangement of the substitutions in the layers of the clay. In this work, computational molecular modeling techniques are used to determine and compare the hydration properties, as well as the structure and mobility of ions (Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Ni²⁺,UO₂²⁺) and water in the interlayer space of the three models of montmorillonite, that differ from each other by the arrangement of isomorphic substitutions in the clay layers.The adsorption and diffusion of the previously listed cations and water are also studied on the surface of montmorillonite clay and the results are compared to those obtained in the interlayer space both at 298 K and at 363 K. The data generated in this work agree well with experimental observations, and show a more or less significant correlation between the clay model used and the type of property calculated.

Pak-chung Leung. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1994. / Includes bibliographical references (leaves 151-158). / Abstract --- p.i / Acknowledgments --- p.iii / Table of contents --- p.iv / List of Figures --- p.viii / List of Tables --- p.ix / List of Abbreviations --- p.xiv / Chapter / Chapter 1. --- General Introduction --- p.1 / Chapter 2. --- Literature Review: Greening process in higher plants --- p.4 / Chapter 3. --- Greening Bioassay in Excised Cucumber Cotyledons / Introduction --- p.13 / Materials and Methods / Plant material --- p.14 / Measurement of Ch1 synthesizing activity in excised cotyledons of different ages --- p.14 / Measurement of Ch1 accumulation in excised cotyledons after various pretreatment periods --- p.15 / Measurement of Ch1 accumulation in excised cotyledons under different light intensities and temperatures --- p.15 / Greening curve --- p.16 / Results and Discussion / Effect of seedling age on Ch1 accumulation --- p.16 / Effect of pretreatment period on Ch1 accumulation --- p.18 / Effects of light intensity and temperature on Ch1 accumulation --- p.18 / Effect of shaking (for oxygen replenishment) on Ch1 accumulation --- p.19 / Greening curve --- p.20 / Greening bioassay in excised cucumber cotyledons --- p.20 / Chapter 4. --- Regulation of Chlorophyll Accumulation in Excised Cucumber Cotyledons / Introduction --- p.27 / Materials and Methods / Materials --- p.28 / Seed germination --- p.28 / Harvesting and pretreatment --- p.28 / Illumination and Ch1 determination --- p.29 / Results / Effect of BA on Ch1 accumulation --- p.29 / Effect of Na2EGTA on Ch1 accumulation --- p.30 / "Effect of Na+, Ca2+ and K+ on Ch1 accumulation" --- p.32 / Effect of duration of pretreatment with Na+ ， Ca2+ and K+ on Ch1 accumulation --- p.34 / Effect of verapamil and Ca ionophore A23187 on Chl accumulation --- p.36 / Effect of TFP on Chl accumulation --- p.37 / Discussion / Effect of BA on Chl accumulation --- p.38 / "Effect of Na+, Ca2+ and K+ on Chl accumulation" --- p.39 / Demonstration of the involvement of Ca2+ in Chl accumulation --- p.43 / Chapter 5. --- The Calcium Effect on Benzyladenine-induced Stimulation of Chlorophyll Accumulation in Excised Cucumber Cotyledons / Introduction --- p.63 / Materials and Methods / Materials --- p.64 / Plant growth and treatment --- p.64 / Pretreatment experiment --- p.64 / Sequence experiment --- p.65 / Results / Pretreatment experiment --- p.65 / Sequence experiment --- p.66 / Discussion --- p.68 / Chapter 6. --- Regulation of 5-Aminolevulinic Acid and Chlorophyll Accumulation in Levulinic Acid-treated Cotyledons / Introduction --- p.80 / Materials and Methods / Materials --- p.81 / Plant growth and treatment --- p.81 / Chl determination and ALA assay --- p.82 / Measurement of ALA and Chl accumulation in LA-treated cotyledons --- p.83 / ALA accumulation curve --- p.83 / Measurement of Chl accumulation in 50 mM NaCl-treated cotyledons --- p.84 / "Measurement of ALA and Chl accumulation in BA-, cations-, Na2EGTA-, verapamil- and TFP-pretreated cotyledons" --- p.85 / Results / Concentrations effect of LA on ALA and Chl accumulation --- p.85 / ALA accumulation curve --- p.86 / Effect of 50 mM NaCl on Chl accumulation --- p.87 / Effect of BA on ALA and Chl accumulation in LA- treated cotyledons --- p.90 / "Effects of Na+, Ca2+ and K+ on ALA and Chl accumulation in LA-treated cotyledons" --- p.91 / "Effects of Na2EGTA, verapamil and TFP on ALA and Chl accumulation in LA-treated cotyledons" --- p.92 / Discussion / Measurement of ALA accumulation in LA-treated cotyledons --- p.93 / Effect of BA on ALA and Chl accumulation in LA-treated cotyledons --- p.96 / "Effects of Na+, Ca2+ and K+ on ALA and Chl accumulation in LA-treated cotyledons" --- p.98 / Demonstration of the involvement of Ca2+ in ALA accumulation --- p.99 / Chapter 7. --- Regulation of 5-Aminolevulinic Acid Accumulation in Isolated Developing Chloroplasts / Introduction --- p.123 / Materials and Methods / Materials --- p.124 / Plant materials --- p.124 / Chloroplast isolation --- p.125 / Incubation conditions --- p.126 / ALA assay --- p.127 / Measurement of ALA accumulation in LA-treated isolated developing chloroplasts --- p.128 / "Measurement of ALA accumulation in BA-, cations-, Na2EGTA-, verapamil- and TFP-treated isolated developing chloroplasts" --- p.128 / Results / Time course study of Chl accumulation in intact greening cotyledons of different ages --- p.129 / Measurement of ALA synthesizing activity in isolated developing chloroplasts incubated in the dark and light --- p.130 / Concentrations effect of LA on ALA accumulation in isolated developing chloroplasts --- p.130 / Effects of BA and the cations on ALA accumulation in isolated developing chloroplasts --- p.131 / "Effect of Na2EGTA, verapamil and TFP on ALA accumulation in isolated developing chloroplasts" --- p.132 / Discussion / Light regulation of ALA synthesizing activity in isolated developing chloroplasts --- p.132 / Regulation of ALA accumulation in isolated developing chloroplasts --- p.134 / Chapter 8. --- Conclusion --- p.147 / References --- p.151

Fung Wai-man. / Thesis (M.Phil.)--Chinese University of Hong Kong. / Includes bibliographies.