Role of Glomerular Proteoglycans in IgA Nephropathy

Mesangial matrix expansion is a prominent feature of the most common form of glomerulonephritis, IgA nephropathy (IgAN). To find molecular markers and improve the understanding of the disease, the gene and protein expression of proteoglycans were investigated in biopsies from IgAN patients and correlated to clinical and morphological data. We collected and microdissected renal biopsies from IgAN patients (n = 19) and from healthy kidney donors (n = 14). Patients were followed for an average time of 4 years and blood pressure was according to target guidelines. Distinct patterns of gene expression were seen in glomerular and tubulo-interstitial cells. Three of the proteoglycans investigated were found to be of special interest and upregulated in glomeruli: perlecan, decorin and biglycan. Perlecan gene expression negatively correlated to albumin excretion and progress of the disease. Abundant decorin protein expression was found in sclerotic glomeruli, but not in unaffected glomeruli from IgAN patients or in controls. Transforming growth factor beta (TGF-β), known to interact with perlecan, decorin and biglycan, were upregulated both on gene and protein level in the glomeruli. This study provides further insight into the molecular mechanisms involved in mesangial matrix expansion in IgAN. We conclude that perlecan is a possible prognostic marker for patients with IgAN. In addition, the up-regulation of biglycan and decorin, as well as TGF-β itself, indicate that regulation of TGF-β, and other profibrotic markers plays a role in IgAN pathology

Catalysis for Lean NOx Reduction - Aspects of Catalyst Synthesis and Surface Acidity

From both economic and environmental perspectives it is desirable to reduce the consumption of fossil fuels. One route to increase the fuel efficiency for vehicles is operation in oxygen excess. However, a major problem with this technique is the lean environment, which obstructs catalytic reduction of nitrogen oxides (NOx) to harmless nitrogen. This thesis focuses on key parameters affecting catalytic reduction of NOx under lean conditions. In specific surface acidity and nanoparticle synthesis have been investigated. The activity for lean NOx reduction by propene and propane, the selectivity for N2 formation, and the surface acidity were investigated with flow reactor experiments and Fourier Transform Infrared (FTIR) spectroscopy over model catalysts, with and without platinum. The NOx reduction activity is markedly dependent on the type of reducing agent. Propene and propane were used in the reaction over platinum supported catalysts and it was found that the samples that showed activity for NOx reduction with propane all contained Br\uf8nsted acid sites. Further, the N2 selectivity was enhanced (using propane) with increasing Br\uf8nsted-site density over these catalysts. For the platinum-free samples a clear correlation between the amount of Br\uf8nsted acid sites and the activity for NOx reduction, with propane, was observed. It is likely that the propane is activated over the Br\uf8nsted acid sites forming some kind of carbenium ions, which probably react with adsorbed NO+ species to form isocyanates that, in turn, may be hydrolysed to amine species. The NOx reduction by isopropylamine was followed in-situ by FTIR and the results indicate a rapid reaction, over Br\uf8nsted acid sites, compared to the corresponding reaction with propane. It is thus conceivable that amine species are possible reaction intermediates in the HC-SCR reaction under the present conditions. However, the hydrocarbon activation and the formation of NO+ species seem to be a prerequisite for the reaction to occur. Platinum nanoparticles were prepared in microemulsions and the resulting particles were used in model catalyst synthesis. The effect of surfactant type on the kinetics of platinum nanoparticle formation in water-in-oil microemulsions was studied with UV-visible spectroscopy. The rate of particle formation was found to be strongly dependent on the type of surfactant used in the microemulsion formulation. The difference in reactivity may be due to either droplet fusion and/or to the chemical microenvironment in the fused microemulsion droplets. Platinum nanoparticles were deposited on alumina support using two different methods. Both methods gave considerable particle agglomeration. However, the rate of addition of solvent, the choice of surfactant, and the pH value are of importance and a weak interaction between the platinum particles and the support seems favourable

Aspects of reducing agent and role of amine species in the reduction of NO over H-ZSM-5 in oxygen excess

In this study the selective catalytic reduction (SCR) of NO has been investigated over H-ZSM-5 with three different reducing agents. Comparison of the reaction mechanisms using propane, ammonia and isopropylamine has been performed using in situ DRIFTS step-response experiments. The same type of surface NH species, likely organic amines, is formed in the presence of either propane or isopropylamine as reducing agent. For NH3, on the other hand, NH4+ is the dominating NH surface species during reaction. Furthermore, in the case of propane, the nature of the NOx-source, i.e. NO or NO2, is crucial for the reaction. With NO2. the reaction likely proceeds fast via direct reduction, while for NO, oxidation to NO2 is required initially. in either case NH species play a vital role in the SCR reaction and organic amines are possible key-intermediates in the SCR with saturated hydrocarbons over H-ZSM-5

On the different roles of NCO and CN in propene-SCR over silver/alumina

Silver/alumina is one of the most promising catalyst materials for HC-SCR. The reaction mechanism remains incompletely understood, however. Isocyanate species (–NCO) and cyanide species (–CN), important intermediates in the reaction path in HC-SCR, were investigated by gas-phase FTIR and DRIFT spectroscopy in step-response experiments. In accordance with the literature, the corresponding gas-phase species, HNCO and HCN, were always detected at the same time at the different steps of the experiment; however, the accumulation and consumption of surface –NCO and –CN species did not show a similar correlation. Consequently, in conflict with the literature, we propose two parallel, independent reaction pathways for –NCO and –CN species. In one of these reaction pathways, surface nitrates react with C-containing surface species either directly to –NCO or via R–NO2 species. In the other pathway, C-containing surface species react with gas-phase NOx or short-lived N-containing surface species to R–NO species and subsequently to –CN species

Aspects of the Role of Hydrogen in H-2-Assisted HC-SCR Over Ag-Al2O3

The role of hydrogen in H-2-assisted HC-SCR of NOx over Ag-Al2O3 is investigated by XPS and in situ DRIFT spectroscopy. Hydrogen does not reduce the surface silver species to metallic silver, however direct reduction of surface nitrates by hydrogen is observed. It is proposed that one important role of hydrogen is the removal of nitrates from the Ag-Al2O3 surface