Thesis (M. Phil.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves 50-53) Also available in print.

Thesis--University of Missouri, School of Mines and Metallurgy, 1884. / A. Neustaedter determined to be Arthur Neustaedter from "1874-1999 MSM-UMR Alumni Directory". The entire thesis text is included in file. Holograph [Handwritten and illustrated in entirety by author]. Title from title screen of thesis/dissertation PDF file (viewed November 21, 2008)

Thesis (M.S.)--University of Texas at El Paso, 2008. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Thesis (Ph. D.)--Materials Science and Engineering, Georgia Institute of Technology, 2006. / Wang, Zhong Lin, Committee Chair ; Summers, Christopher J., Committee Co-Chair ; Wong, C. P., Committee Member ; Dupuis, Russell D., Committee Member ; Wagner, Brent, Committee Member

Th.--Sci. phys.--Grenoble 1, 1978. N°: 86.

Proyecto de Actividad Formativa Equivalente a tesis presentada para optar al Grado de Magíster en Manejo de Suelos y Aguas / En Chile el cultivo de maíz representa el 20% del área total de cultivos anuales y, debido a condiciones favorables de temperatura y radiación solar, se obtiene uno de los rendimientos más altos a nivel mundial (12 Mg ha-1). Sin embargo, la productividad de este cultivo se ve afectada por diversos factores, en particular, la baja fertilidad de los suelos donde es cultivado. Es así que en los últimos años ha cobrado relevancia la deficiencia de zinc (Zn) en Chile, considerado en la actualidad como el micronutriente más deficiente en suelos agrícolas del mundo. El Zn cumple funciones fisiológicas importantes en la planta y una deficiencia de este micronutriente puede comprometer seriamente el rendimiento y la calidad del grano, particularmente el maíz es altamente sensible a esta deficiencia nutricional. Consecuentemente, se han planteado recomendaciones de fertilización con Zn en ciertos suelos, generalmente basadas en la biodisponibilidad del Zn obtenida mediante la extracción con agentes quelantes, que intentan simular su absorción por las raíces de las plantas. No obstante, existe evidencia que esta única prueba química no es suficiente para realizar recomendaciones adecuadas de fertilización.

Chez les plantes, alors qu'il est clair que l'homéostasie des différents nutriments est fortement dépendante les uns des autres, ils sont généralement étudiés indépendamment les uns des autres. Étant donné la rareté des études antérieures évaluant la signification biologique de l'interaction de l'homéostasie des nutriments minéraux, on en sait très peu sur la base génétique et moléculaire de ces interactions. Au cours de ma thèse, nous avons progressé de manière significative vers une compréhension plus intégrative du problème et identifié les bases moléculaires et génétiques d'une interaction nutritive très importante et conservée: l'interaction du zinc et du phosphate, dans laquelle les gènes PHO1;H3 et Lyso PhosphatidylCholine (PC) AcylTransferase 1 (LPCAT1) jouent des rôles centraux. En combinant des approches de biologie systémique et de biologie fonctionnelle, nous avons identifié le module fonctionnel (quatre facteurs transcriptions) qui régule l'expression de PHO1; H3 en condition de carence en Zn. Suite à une étude de génétique d’association (GWAS) nous avons découvert un nouveau rôle du gène LPCAT1 dans l’accumulation du phosphate en conditions de carence en Zn, Ensuite, nous avons déterminé une voie moléculaire complète contrôlant l'expression de ce gène. Ce travail nous permis de révéler un lien fondamental entre le métabolisme des phospholipides et l'interaction homéostasie Pi-Zn, et de proposer un nouveau rôle pour Lyso-PC et PC dans le contrôle de l'interaction homéostasie macro- et micronutriments chez les plantes. Les résultats obtenus offrent une nouvelle perspective pour élabore des nouvelles stratégies pour améliorer l’accumulation de Pi dans les plantes via la modulation de la voie de signalisation de la carence en Zn. / In plants, while it is clear the homeostasis of different nutrients is highly dependent on each other, they are usually studied independent of each other. Given the paucity of past studies assessing the biological significance of mineral nutrient homeostasis interaction, very little is known about the genetic and molecular basis of such interactions. During my thesis, we made significant progress in going towards a more integrative comprehension of the problem and identify the molecular and genetic bases for a highly important and conserved nutrients interaction: the interaction of zinc and phosphate. First, using the phosphate transporter PHO1;H3 as entry molecular point, and by combining system biology and functional genomics approaches we have identified the functional module (four transcription factors) that regulates the expression and activity of PHO1;H3 under Zn deficiency leading to control Pi accumulation in shoots. Second, following our discovery of Lyso PhosphatidylCholine (PC) AcylTransferase 1 (LPCAT1) using genome-wide association studies (GWAS), we determined complete molecular pathway controlling the expression of this gene. We further uncovered a fundamental link between phospholipid metabolism and Pi-Zn homeostasis interaction via LPCAT1, which lays the foundations to explore a new role for Lyso-PC and PC in control of macro- and micronutrients homeostasis interaction. Taken together, our discoveries offer a new perspective on how to improve Pi content in plants, as our findings suggests that modulating the Zn-deficiency signalling pathway might be a good and simple approach for that.

The present study was carried out to determine the effects and possible mechanism of action of zinc supplementation on the in vitro growth of malignant murine melanoma (B16) and non-malignant monkey kidney (LLCMK) cells. Cell culture studies showed that zinc supplementation significantly inhibited B16 growth at all the concentrations studied (1, 3, 5 and lOμg/ml). Zinc was also found to inhibit the growth of the LLCMK cells, although to a lesser extent than the B16 cells. Possible evidence of mobilisation of the essential fatty acids from the membrane phospholipid stores was noted in both cell types. This effect was, however, greater in the B16 cells. Δ⁶-desaturase activity was found to be significantly lower in the B16 cells than in the LLCMK cells (p ≥ 0.05). Zinc supplementation resulted in an increase in the enzymes activity in the LLCMK cells and, at high concentrations, in the B16 cells. An estimation of elongase and Δ⁶-desaturase activity with zinc supplementation indicated that zinc had little or no effect on the activity of these enzymes. B16 cells were found to have higher levels of free radicals than the LLCMK cells. Zinc supplementation resulted in increased free radical formation in the B16 cells, while no effect was observed in the LLCMK cells. Lipid peroxidation increased in both cell types with increased zinc concentrations. The observed effect of zinc supplementation on cell growth may involve these elevated levels of lipid peroxides. CycIo-oxygenase activity was found to be greater in the B16 cells than the LLCMK cells. The activity of the enzyme increased with higher concentrations of zinc (lOμg/ml) in both cell types. Prostaglandin E, levels were found to be lower in the B16 cells compared to the LLCMK cells. The levels of prostaglandin E, in both cell types appeared to be dependent on the levels of the polyunsaturated fatty acid precursors to the prostaglandins. Zinc was found to inhibit the activity of the enzyme adenylate cyclase in both cell types. The cAMP levels in the LLCMK cells were also found to decrease with zinc supplementation. In the case of the B16 cells, cAMP levels increased at low concentrations of zinc despite a decrease in adenyl ate cyclase activity, suggesting a possible inhibition of cAMP phosphodiesterase activity at these concentrations of zinc. It is concluded that although zinc supplementation does have an effect on cell growth, this effect is not mediated through the activation of adenylate cyclase by the prostaglandins resulting in elevated levels of cAMP. A possible mechanism involving lipid peroxidation is proposed.

This thesis is missing pages 9, 39, 108-110. The pages are not in the other copies of the thesis. -Digitization Centre / This work describes efforts towards creating chemical models for a variety of zinc based metalloenzymes. A background on the current progress of modeling zinc enzymes is presented, as is a brief review of zinc biochemistry. The structure of triaquo(tris-2-pyridylphosphine)nickel(ll) dinitrate is presented and compared with its zinc analogue. Both structures have octahedral geometry with no unusual bond lengths. The synthesis and characterization of bis(2,4,5-tribromoimidazole)(diaquo)zinc(II). (II) is also presented in this work. A similar compound, Zn(Im)2 (III) was also prepared in this work. Both compounds were characterized by X-ray crystallography, IR spectroscopy, and elemental analysis. Neutron crystallography was used to characterize (II) as a peraquo species. Both (II) and (III) possess tetrahedral geometry about the zinc atom. (III) is multiply catenated and cannot be considered as a discrete molecular species. The pKa2 of 2,4,5-tribromoimidazole, the organic ligand in (II), was measured and found to be 10.7(2). Bond valence theory was used to analyze (II). Extended Huckel molecular orbital calculations were carried out on (II). (II) was compared with a variety of other zincimidazole compounds. It was discovered that (II) has unusually small carbon-nitrogen-carbon angles within its tribromoimidazole rings. It is uncertain whether this feature is because of the coordination of the tribromoimidazole rings to the zinc atom, or whether it is an inherent feature of the tribromoimidazole rings. A copper analogue of (II) has also been synthesized and has been tentatively assigned the formula Cu(lmBr3)2(OH2)2 . X-ray characterization of this compound has not yet been accomplished. / Thesis / Master of Science (MS)

published_or_final_version / abstract / Physics / Master / Master of Philosophy