Uptake and metabolism of lipoproteins from patients with diabetes mellitus type II by glomerular epithelial cells

BACKGROUND: Recent studies suggest that dyslipidaemia accelerates the progression of diabetic nephropathy, but the various pathomechanisms underlying such abnormalities are not completely delineated. METHODS: We isolated, radiolabelled, and characterized very-low-density lipoproteins (VLDL) and low-density lipoproteins (LDL) from eight diabetic patients with moderate impairment of renal function and dyslipidaemia and studied their interaction with LDL receptors in human glomerular epithelial cells. RESULTS: While diabetic VLDL showed no compositional changes, LDL particles contained a higher proportion of triglycerides at the expense of cholesterol in comparison with healthy controls. Despite differences in composition, both VLDL and LDL from patients exhibited reduced receptor affinity and cellular uptake capacity by glomerular epithelial cells. Since LDL composition was altered intracellular cholesterol homeostasis was investigated. Due to reduced cholesterol content and lower uptake capacity, diabetic LDL were less effective in suppressing intracellular sterol synthesis and in activating acylcholesterol acyltransferase than LDL from controls. Electrophoretic mobility of apoB from diabetic patients was enhanced as compared to controls, most probably due to the higher degree of glycation (17 + 1.7 versus 11 + 1%, P < 0.05) but not to oxidation (TBARS 0.5 + 0.2 versus 0.2 + 0.1 mumol/1). Oxidized LDL was not taken up in significant amounts, indicating no scavenger receptor activity in glomerular epithelial cells. CONCLUSION: The receptor-specific uptake of diabetic VLDL and LDL by glomerular epithelial cells is impaired. Compositional changes of the LDL particle and glycation of the protein moiety may contribute to altered glomerular uptake. However, glycation of the protein moiety may be superior to compositional changes. Because glomerular structures like mesangial matrix and endothelial cells are known for preferential binding of modified lipoproteins, further studies are required to elucidate their potential role in the progression of diabetic glomerulosclerosis.     

Technical and economical system comparison of photovoltaic and concentrating solar thermal power systems depending on annual global irradiation

Concentrating solar thermal power and photovoltaics are two major technologies for converting sunlight to electricity. Variations of the annual solar irradiation depending on the site influence their annual efficiency, specific output and electricity generation cost. Detailed technical and economical analyses performed with computer simulations point out differences of solar thermal parabolic trough power plants, non-tracked and two-axis-tracked PV systems. Therefore, 61 sites in Europe and North Africa covering a global annual irradiation range from 923 to 2438 kW h/m² a have been examined. Simulation results are usable irradiation by the systems, specific annual system output and levelled electricity cost. Cost assumptions are made for today's cost and expected cost in 10 years considering different progress ratios. This will lead to a cost reduction by 50% for PV systems and by 40% for solar thermal power plants. The simulation results show where are optimal regions for installing solar thermal trough and tracked PV systems in comparison to non-tracked PV. For low irradiation values the annual output of solar thermal systems is much lower than of PV systems. On the other hand, for high irradiations solar thermal systems provide the best-cost solution even when considering higher cost reduction factors for PV in the next decade. Electricity generation cost much below 10 Eurocents per kW h for solar thermal systems and about 12 Eurocents/kW h for PV can be expected in 10 years in North Africa.     

Irradiance calculation on shaded surfaces

Operating results of recently built photovoltaic systems have shown that shading can cause high losses in performance. We need methods for calculating the reduced irradiance to minimize the shading losses in the planning process. There are well-known models to estimate the irradiance received by a tilted surface. However, these methods normally do not include shading reduction caused by objects in the surroundings. Therefore, methods are proposed to include shading in calculations of direct and diffuse irradiation. Before these methods can be used, the surroundings have to be surveyed. Hence, how to survey objects in an easy way is discussed. Using the proposed methods and calculations it is possible to include shading reduction in the prediction of the irradiance on a tilted surface. Finally, the influence of shading on the irradiance is shown by an example.     

Energieeinsparung durch vorzeitigen Ersatz von Haushaltsgeräten

The energy demand of large household appliances was reduced during the recent years. We can save a large amount of energy and we can reduce the corresponding carbon dioxide emissions if we replace clapped-out appliances. If we replace the appliance before end of life, the energy demand for the operation will be also reduced. On the other hand there is an increased energy demand for the production of the new appliances that is additionally needed for the replacement. In this paper we discuss, when a replacement before end of life is recommendable.     

Nature of Surface Deposits on Sulfated Zirconia Used as Catalyst in the Benzoylation of Anisole

The effects of CO₂, CO and H₂ co-reactants on CH₄ pyrolysis reactions catalyzed by Mo/H-ZSM-5 were investigated as a function of reaction temperatures and co-reactant and CH₄ concentrations. Total CH₄ conversion rates were not affected by CO₂ co-reactants, except at high CO₂ pressures, which led to the oxidation of the active MoC _x species, but CH _x intermediates formed in rate-determining C–H bond activation steps increasingly formed CO instead of hydrocarbons as CO₂ concentrations increased. CO formation rates increased with increasing CO₂ partial pressure; all entering CO₂ molecules reacted with CH₄ within the catalyst bed to form two CO molecules at 950-1033 K. In contrast, hydrocarbon formation rates decreased linearly with increasing CO₂ partial pressure and reached undetectable levels at CO₂/CH₄ ratios above 0.075 at 950 K. CO formation continued for a short period of time at these CO₂/CH₄ molar ratios, but then all catalytic activity ceased, apparently as a result of the conversion of active carbide structures to MoO _x . The removal of CO₂ from the CH₄ stream led to gradual catalyst reactivation via reduction-carburization processes similar to those observed during the initial activation of MoO _x /H-ZSM-5 precursors in CH₄. The CO₂/CH₄ molar ratios required to inhibit hydrocarbon synthesis were independent of CH₄ pressure because of the first-order kinetic dependencies of both CH₄ and CO₂ activation steps. These ratios increased from 0.075 to 0.143 as reaction temperatures increased from 950 to 1033 K. This temperature dependence reflects higher activation energies for reductant (CH₄) than for oxidant (CO₂) activation, leading to catalyst oxidation at higher relative oxidant concentrations as temperature increases. The scavenging of CH _x intermediates by CO₂-derived species leads also to lower chain growth probabilities and to a significant inhibition of catalyst deactivation via oligomerization pathways responsible for the formation of highly unsaturated unreactive deposits. CO co-reactants did not influence the rate or selectivity of CH₄ pyrolysis reactions on Mo/H-ZSM-5; therefore, CO formed during reactions of CO₂/CH₄ mixtures are not responsible for the observed effects of CO₂ on reaction rates and selectivities, or in catalyst deactivation rates during CH₄ reactions. H₂ addition studies showed that H₂ formed during CH₄/CO₂ reactions near the bed inlet led to inhibited catalyst deactivation in downstream catalyst regions, even after CO₂ co-reactants were depleted.     

Speicherbedarf einer Elektrizitätsversorgung bei einem hohen Anteil regenerativer Kraftwerke

Due to the unsteadiness of wind and solar power there will be more fluctuations in the energy supply with an increasing amount of renewable energy. The fluctuations have to be regulated with an optimized demand management and with new storage systems. A possible future electricity supply in Germany serves as an example for determining the storage demand and possibilities for its reduction.     

Soiling of irradiation sensors and methods for soiling correction

Access to exact solar irradiation data is indispensable for planning and dimensioning of applications as e.g. solar power plants. The expectable amount of yearly solar irradiation has an over-proportional impact on the financing and therefore has to be known very precisely. For this reason, DLR performs investigations at PSA to improve the accuracy of irradiation data, which are measured at several locations in southern Spain and Morocco. Devices as Rotating Shadowband Pyranometers (RSP) as well as thermal pyranometers and a pyrheliometer are used. Besides well-documented and known technical aberrations, soiling of the sensors is an important source for underestimation of the measured irradiation, especially at offside stations where daily maintenance is not possible. In this paper, we present soiling characteristics of these sensors and a corresponding method for its correction.     

Catalytic acylation of aromatics with carboxylic anhydrides over sulfated zirconia

Two sulfated zirconia samples have been synthesized using different preparation procedures. Textural and acid properties of these catalysts have been characterized and compared with commercial zeolite Hβ by means of nitrogen low-temperature adsorption, temperature-programmed desorption of ammonia and microcalorimetry. The two sulfated zirconias proved to be appropriate catalysts for acylations of aromatic compounds containing electron donating substituents, e.g., for syntheses of several aromatic ketones. This revised version was published online in June 2006 with corrections to the Cover Date.