No abstract available / Dissertation (MA)--University of Pretoria, 2013. / Afrikaans / unrestricted

Fibulin-4 is an extracellular matrix protein which plays an essential function in the assembly of elastic fibres, and may be involved in the modulation of TGFβ bioavailability and smooth muscle cell differentiation. Mutations in fibulin-4 can cause autosomal recessive cutis laxa, a frequently lethal connective tissue disorder. Although patient studies have provided some insights into the pathological mechanisms of this disease, a detailed analysis of the consequences of fibulin-4 mutations on a molecular and cellular level was required.The findings presented in this thesis demonstrate that cutis laxa-causing fibulin-4 mutations may lead to reduced extracellular levels of fibulin-4 due to its increased susceptibility to protease degradation and misfolding/aggregation. An accumulation of autophagic vesicles was observed, indicating a blockage of autophagy, possibly due to intracellular accumulation of aggregated/misfolded mutant protein. In the extracellular matrix, mutations affected the ability of fibulin-4 to interact with the major components of the elastic fibre assembly, heparin, LTBP-1 and fibronectin. In addition, fibulin-4 mutations generally reduced expression levels of elastic fibre assembly components. In summary, these findings contribute to the understanding of fibulin-4 associated cutis laxa, and provide a basis upon which future therapeutic interventions may be developed.

Dans le contexte actuel, les ressources en énergie fossiles diminuent et deviennent de plus en plus couteuses, se pose aussi le problème de l’environnement. Dans ce cadre, les piles à combustible à oxydes solides (Solid Oxide Fuel Cell en anglais, SOFC) sont une source d’énergie propre et alternative très prometteuse. Utilisé de façon réversible, ce système peut également permettre le stockage de l’électricité produite de façon intermittente via l’électrolyse de l’eau. Néanmoins, plusieurs verrous technologiques restent encore à lever en matière de performances et de durabilité des matériaux actuellement utilisés, notamment pour ce qui concernent les matériaux d’électrode. Dans ce travail de thèse de doctorat, notre contribution a porté sur deux matériaux de cathode de SOFC, Ba2Co9O14 et Ca3Co4O9+δ, et des composés dérivés de La4Ti2O10 pouvant présenter un intérêt comme matériau d’anode. Nous nous sommes intéressés plus particulièrement à la compréhension des mécanismes physico-chimiques intervenant au sein de ces matériaux en faisant appel à la spectroscopie d’impédance. Pour les cobaltites, cette étude a permis de mettre en évidence les paramètres limitants les performances électrochimiques. Elle aidera à l’optimisation de futures cellules complètes plus performantes. Pour les phases dérivées de La4Ti2O10, une étude par diffusion des neutrons a permis de confirmer les mécanismes de diffusion de l’oxygène au sein de ces matériaux. Leurs conductivités et propriétés catalytiques restent néanmoins insuffisantes pour pouvoir espérer les utiliser comme matériau d’anode, au contraire d’autres titanates de lanthane de structure perovskite lamellaire. / In the current context, fossil energy resources decrease and become more expensive, in addition to environmental concern. In this frame, solid oxide fuel cells (SOFC) are a promising green alternative energy source. Reversibly used, this system can also allow storage of electricity produced intermittently through the electrolysis of water. However, several bottlenecks still remain in terms of performances and stability of materials currently used to improve their lifetime and decrease their working temperature. In this doctoral thesis, our contribution focused on two cathode materials for SOFCs, Ba2Co9O14 and Ca3Co4O9+δ, and compounds derived from La4Ti2O10 which may be relevant as anode material. Our study mainly focused on the understanding of the physicochemical mechanisms involved in these materials by using impedance spectroscopy. For cobaltites, this study has led to the identification of the limiting parameters and will help the future optimization of complete stacks with better performances. For the La4Ti2O10 derived phases with the cuspidine structure, a neutron scattering study confirmed the oxygen diffusion mechanisms in these materials. However, their conductivity and catalytic properties remain insufficient to hope to use these compounds as SOFC’s anode, unlike other lanthanum titanates which display a layered perovskite structure.

For centuries people have used plants as medicine or food additives with varying success to cure and prevent diseases. Written records about medicinal plants date back at least 5 000 years to the Sumerians. According to World Health Organization (WHO) around 80 % of the population in developing countries is dependent on herbal medicine for basic healthcare needs. Even at the dawn of the twenty-first century, 11 % of the 252 drugs considered as basic and essential by WHO were exclusively of flowering plant origin. The genus Helichrysum, belongs to the family Asteraceae and is represented by approximately 600 species in Africa, of which 244 species are indigenous in South Africa. In Helichrysum aureonitens, galangin is one of the flavonol compounds with good medicinal properties. H. aureonitens was targeted to be enhanced via cell suspension culture to potentially produce valuable natural products. In ethanol extracts of cell suspension cultures, galangin was not detected even though it was present in the leaves of the intact plants. Some other compounds were induced in higher amounts in the cells of H. aureonitens suspension cultures when compared to that produced in the intact plants. To find out the reasons for the absence of galangin in the cells of H. aureonitens suspension cultures, some of the intermediates of the 4’-OH biosynthetic pathway for production of flavonols were analyzed by GC-MS, including cinnamic acid, p-coumaric acid, naringenin and kaempferol. None of these were detected in the H. aureonitens cell suspension cultures. The major compound from H. aureonitens cell suspension cultures was isolated and identified as a new chlorophenol compound named 4-chloro-2-(hepta-1,3,5-triyne-1-yl)-phenol (a triyne). This triyne has previously been proposed as being an intermediate in the acetylene biosynthetic pathway in Helichrysum spp., however only the methyl ether form had previously been isolated from the roots of H. coriaceum. The triyne isolated from the H. aureonitens cell suspension cultures in the present study was detected in intact plant extracts, but at very low concentrations. Results of the anti-tuberculosis assay of the cell suspension culture extracts and the triyne showed that the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the ethanol extract of cell suspension cultures against Mycobacterium tuberculosis H37Rv were found to be 1.0 mg/ml and 2.0 mg/ml respectively and the triyne was not active at 200 µg/ml. The ethanol extract of the cell suspension cultures and the triyne were also evaluated for their cytotoxicity against monkey kidney Vero cells and human prostate epithelial carcinoma (DU145) cell lines. The inhibitory concentrations (IC50) of the crude extract and the triyne was found to be 12.11 and 1.51 µg/ml against the Vero cells respectively. The crude extract and the triyne showed similar activity in the prostate cancer cell lines by exhibiting IC50 values of 3.52 and 2.14 µg/ml respectively. The triyne therefore warrants further investigation for its potential as an anticancer drug. Flavonoids represent the major phenolic compounds which are responsible for the medicinal properties in the Helichrysum genus. Some of flavonols, including kaempferol, quercetin, and galangin are also present in H. aureonitens. In this study both galangin and kaempferol (containing a 4’-OH group) were detected in leaf samples of H. aureonitens. But GC-MS analysis of the leaf samples of H. aureonitens did not show the existence of biosynthetic intermediates such as p-coumaric acid and naringenin (compounds having a 4’-OH) while cinnamic acid and some other compounds with no OH at the 4’ position on the B ring, were detected. The chemical structure analysis of the isolated compounds showed that they are pinocembrin chalcone, pinocembrin, pinobanksin and galangin, all containing no OH group at the 4’ position. This indicates that some part of the 4’-OH biosynthetic pathway for 4’-OH flavonoids is not functional in H. aureonitens. Since the only (yet identified) enzyme responsible for hydroxylation at the 4’ position on the B ring is cinnamate 4-hydroxylase (C4H), it can be postulated that C4H might be able to hydroxylate other substrates in H. aureonitens plants. One copy of C4H was isolated and cloned from H. aureonitens. It has 1518-base pairs (including stop codon, TAA) and an open reading frame encoding a 506-amino-acid polypeptide. It showed the highest homologies to Echinacea angustifolia (Asteraceae) C4H with 83.6 % identity on the nucleotide level but 93 % identity on the amino acid level. The genomic DNA sequence of the isolated C4H from H. aureonitens indicates the presence of three introns with a longer size compared to the Arabidopsis thaliana C4H gene structure. The presence of the first intron has not been reported before in the C4H gene from other plants and it is therefore a new finding from the isolated C4H in H. aureonitens. To check the putative isolated C4H, the full length cDNA of C4H was isolated from H. aureonitens and for the first time integrated in a secreted expression vector, pPICZáC, and transformed into Pichia pastoris. After the 48 hrs induction protein was collected, precipitated by ammonium sulphate and finally column purified. The results of SDS-PAGE electrophoresis and Western blot showed the expression of a protein with a size of 50-60 kDa. The calculated mass of C4H with regarding to a polyhistidine tag is about 60.5 kDa. The secreted expression was found as an effective system for the production of a soluble C4H protein with easy purification. / Thesis (PhD)--University of Pretoria, 2009. / Plant Science / unrestricted

A series of bidentate amidate ligands with variable groups R' and R" abbreviated by [R"(NO)R'] and adamantyl substituted tetradentate amidate ligands abbreviated by Ad[0₂N₂] were utilized as ancillaries for Ti, Zr, and Hf. Protonolysis routes into homoleptic amidate complexes, tris(amidate) mono(amido), bis(amidate) bis(amido), and bis(amidate) dibenzyl complexes are high yielding when performed with tetrakis(amido) and tetrabenzyl group 4 starting materials. Many of these complexes have been characterized in both the solid-state and in the solution phase, where in the latter case these complexes are fluxional and undergo exchange processes. Multiple geometric isomers are possible with the mixed N,0 chelate provided by the amidate ligands, and geometric isomerization of bis(amidate) bis(amido) complexes has been examined through X-ray crystallographic and density functional theory (DFT) calculations. Isomerization is dictated largely by the steric bulk present at the N of the amidate ligands, and is proposed to proceed through a K²-K¹-K² ligand isomerization mechanism, which is supported by crystallographic evidence of K¹-bound amidate ligands. The amidate ligand system binds to these metals in a largely electrostatic fashion, with poor orbital overlap, generating highly electrophilic metal centers. The bis(amidate) dibenzyl complexes of Zr and Hf are reactive towards insertion, abstraction, and protonolysis. Insertion of isocyanides into the Zr-C bonds of [DMP(NO) tBu]₂Zr(CH₂Ph₂ results in the formation of ƞ₂-iminoacyl complexes, which can either undergo thermally induced C=C coupling to generate an enediamido complex (aryl isocyanides), or rearrange to generate a bis(amidate) bis(vinylamido) complex (alkyl isocyanides). Benzyl abstraction to generate cationic Zr bis(amidate) benzyl complexes is also possible through reaction with [Ph₃C][B(C₆F₅)4] or B(C₆F₅)₃ Terminal imido complexes with novel pyramidal geometries are generated through protonolysis of bis(amidate) bis(amido) Ti and Zr complexes with primary aryl amines. DFT calculations demonstrate the existence of a Zr⁻₌N triple bond for these complexes. Dimeric imido complexes have been characterized in the solid state, but are not maintained in solution. Cycloaddition reactions of the terminal Zr imido complexes with C=0 bonds result in the formation of proposed oxo complexes and organic metathesis products. Catalytic aminoalkene cyclohydroamination has also been realized with these complexes, generating N-heterocyclic products. A series of kinetic and labeling studies support an imido-cycloaddition mechanism for catalytic cyclohydroamination of primary aminoalkenes with neutral bis(amidate) Ti and Zr precatalysts. The intermediate Ti imido complex, K²-[Dipp(NO)tBu-K¹_[DiPP(No) tBu]Ti=NCH₂CPh₂CH₂CH=CH₂(NHMe₂), has been isolated and characterized in the solid-state and in solution. Amine stabilized imido complexes of this type are invoked as the resting state for the catalytic reaction, and solution phase data support a chair-like geometry, where the alkene is coordinated to the metal center. A diastereoselectivity study supports this proposed solution structure. Eyring and Arrhenius parameters, as well as isolation of a 7-coordinate model imido complex, support a seven-coordinate transition state for the rate-determining metallacycle protonolysis reaction. In contrast, secondary aminoalkene hydroamination catalysis with cationic Zr benzyl complexes is proposed to proceed through a σ-bond insertion mechanism. Proton loss from cationic Zr amido complexes to generate imido species is proposed with primary aminoalkenes, and the resultant neutral imido complexes can catalyze the cyclization of these substrates by the aforementioned imido-cycloaddition mechanism. The ability of the amidate ligand system to promote both mechanisms is unique in the field of alkene hydroamination catalysis. / Science, Faculty of / Chemistry, Department of / Graduate

The Tumor Necrosis Factor Receptor Superfamily (TNFR) is responsible in regulating a myriad of physiological function including the regulation of the immune system. Among the members include CD137 (4-1BB), an inducible costimulatory receptor known for its potent activation, proliferation, and survival effects on T cells. Stimulation of NK cells with agonistic α-CD137 antibodies are known to increase IFN-γ production and proliferation in NK cells as well as increase efficacy of anti-tumor responses. However, NK cell death has also been seen in certain circumstances, although the mechanism remains to be determined. In vitro stimulation of NK cells revealed that α-CD137 induced NK cell death occurs through both TNFR1 and TNFR2, although the action of TNF-α and TNF-ß remain uncertain. Death was independent of other cytotoxic mechanisms such as granzyme/perforin, Fas-Fas ligand, and TRAIL. During MCMV infection, α-CD137 induces NK cell death during the early phase of infection reducing viral resistance. This causes increased viral proliferation which drives NK cell proliferation, likely through Ly49H-m157 interactions, to high levels by day 4 of infection. The use of α-CD137 as a tumor therapeutic is promising with several applications undergoing clinical trials. However, my results raise concern of other effects including the depletion of NK cells. This may cause a temporary impairment in immune function against pathogenic infections and a compensatory reaction of NK cell proliferation, both of which may cause damage to the host. However, with proper co-stimulation or co-treatments, this impairment may be overcome and prevent adverse effects in patients.

L'agglomération des fines entraîne une augmentation importante de la demande en eau des mélanges cimentaires et constitue un frein à la valorisation des sous-produits contenant des proportions élevées de fines. Une modélisation discrète de la microstructure des agglomérats de fines particules est développée. Le modèle intègre les forces de contact avec prise en compte du frottement et du roulement, les forces physico-chimiques et les forces hydrodynamiques calculées avec l'approximation de drainage libre. Le processus d'agglomération, de fragmentation et de restructuration sous cisaillement d'agglomérats fractals de fines particules minérales est étudié en vue de quantifier l'eau immobilisée dans les flocs. Un agglomérat initial isolé et lâche est soumis à un taux de cisaillement constant. Lorsque les forces hydrodynamiques sont prépondérantes par rapport aux forces de cohésion, l'agglomérat mère se fragmente en agglomérats secondaires jusqu'à atteindre un état stationnaire, où le nombre, la taille et la structure des flocs peuvent être considérés comme constants. L'influence du gradient de vitesse, du contexte physico-chimique, de la taille et de la polydispersité des particules sur les caractéristiques microstructurales des flocs à l'équilibre est étudiée. Il est montré que le comportement d'une suspension diluée monodisperse peut être décrit par un unique nombre adimensionnel faisant intervenir la force de cohésion maximale, la taille des particules et le gradient de vitesse. / The agglomeration of fines leads to a significant increase in water demand of cement mixtures and hinders the valorization of by-products containing high fines proportions. A discrete modeling of the microstructure of fine particles agglomerates is developed. The model takes into account contact forces, physico-chemical, and hydrodynamic forces computed with the free draining approximation. The agglomeration, fragmentation and restructuring process of fractal agglomerates of fine mineral particles under shear is studied to quantify the entrapped water in the flocs. A loose initial agglomerate isolated is submitted to a constant shear rate. When the hydrodynamic forces predominate over the adhesive forces, the parent agglomerate is broken up into secondary agglomerates until reaching a steady state, where the number, size and structure of flocs can be considered constant. The influence of the velocity gradient, the physico-chemical context, particles size and their polydispersity on the microstructural characteristics of flocs at steady state is studied. It is shown that the behavior of a monodisperse dilute suspensions can be described by a dimensionless single number involving maximum cohesion force, particle size and velocity gradient.

Ce travail a pour objectif le développement de films d’emballage alimentaire à haute teneur en matières premières bio-sourcées, et l’optimisation de leurs propriétés d’usage. L’ajout de G1, grade de base de la polyoléfine greffée amidon, détériore les propriétés optiques des films obtenus. L’adhésion interfaciale LDPE / G1 est insuffisante pour l’application visée, en raison de l’incompatibilité entre le LDPE et la partie PP de la polyoléfine greffée amidon. Des améliorations de cette adhésion sont observées, notamment par l’augmentation de la température d’extrusion de G1, de la filière, ou en modifiant la résine bio-sourcée. L’adhésion interfaciale PEgMA / G1 est également faible, pour les raisons citées précédemment. Le remplacement du PEgMA par du PPgMA permet d’obtenir une adhésion excellente sans détériorer l’adhésion entre le liant et l’EVOH. Enfin, l’étude du comportement à la rupture de films obtenus à partir des trois grades du polymère bio-sourcé est réalisée par la méthode du travail essentiel à la rupture. On observe une augmentation de 85 % de la tenacité entre le grade de base et le grade le plus modifié. Cette différence peut être attribuée à l’augmentation de la masse molaire induite par la modification de la résine. De plus, la corrélation de l’image digitale permet d’accéder aux déformations locales d’éprouvettes à double entaille, et permet par ailleurs de montrer la symétrie des déformations pour toutes les éprouvettes. En suivant la taille du ligament au cours du temps, il est montré que la propagation des fissures commence à 95 % de la force maximale, démontrant une plastification complète du ligament avant la propagation des fissures. / The aim of this work is the development of food packaging films with a high concentration of biobased raw materials, and the optimization of the usual properties. The addition of G1, basic grade of the starch grafted polyolefin, significantly deteriorates the optical properties together with the tear strength of the obtained films. The interfacial adhesion LDPE / G1 is insufficient for a use in the field of food packaging, because of an incompatibility between LDPE and the PP part of the starch grafted polyolefin. Some improvements of this adhesion are observed, in particular by increasing the extrusion temperature of G1, the temperature of the die, or by the modification of the bio-based resin. The interfacial adhesion PEgMA / G1 is also relatively low, for the same reasons as mentioned above. The replacement of PEgMA by PPgMA provides excellent adhesion at the interface without deteriorating the adhesion between the binder and EVOH. Finally, the study of the fracture behavior of the films made from three grades of the starch grafted polyolefin is produced by the method of essential work of fracture. An increase of 85 % of the toughness is observed, between the base grade and the highest modified grade. This difference can be attributed to the increase in molecular weight induced by the modification of bio-based resin. In addition, the digital image correlation provides access to local deformations of the double notched specimens. It also serves to show the symmetry of all the specimens. By following the ligament size over time, it is shown that the crack starts growing at 95% of the maximum force, showing a complete plasticization ligament before the crack growth.

Using a basic qualitative approach, interviews were conducted with five agents in North Dakota with a range of experiences and lengths of service to evaluate the effectiveness and implementation of Common Measures, a set of survey instruments designed to assess the impact of the 4-H program. The study addresses the culture of North Dakota Extension’s views on evaluation and the implementation of Common Measures. The use of a state-wide reporting tool to assess the 4-H program in North Dakota was perceived as necessary, however, many agents felt Common Measures, missed the mark and did not meet the North Dakota reporting. The ability to tell the story of the 4-H program and the long-term impact it has on youth is necessary to the success of any state-wide reporting venture. Additional training on how alternative forms of data collection can be used to tell the story of their program is needed.

The purpose of this thesis is to explore and analyze the wealth of intrinsic value that is to be found in compositions originally written for piano duet (two performers at one piano). Only compositions originally conceived for piano duet will be considered transcriptions of works that were at first in the form of piano solo, string quartet, orchestra or any such medium other than piano duet, will not be considered in this writing. Also excluded will be works for piano duet that are not of concert hall use; this paper is concerned with that literature for piano duet which is of a caliber transcending pure pedagogy. Another object of this thesis is to show what a remarkable amount of art has been cast in the form of piano duet literature.