Techn. Universiẗat, Diss., 2007--Darmstadt.

Techn. Universiẗat, Diss., 2000--Berlin.

Techn. Universiẗat, Diss., 2001--Berlin.

Techn. Universiẗat, Diss., 2004--Berlin.

Cardiac hypertrophy and heart failure are affecting almost one million people in the UK alone. The available therapies of cardiac hypertrophy are for symptomatic treatment. Recently attention has been moved towards identification of novel drugs which intervene with signalling pathways involved in hypertrophy. To achieve this goal it was important to understand the role of genes involved in the development of cardiac hypertrophy. One of such genes is plasma membrane calcium ATPase isoform 4 (PMCA4). Although several studies which used genetically modified animal models suggested the involvement of PMCA4 during the development of cardiac hypertrophy, the actual role of PMCA4 is still unclear. In this study, we will clarify the role of PMCA4 during the development of cardiac hypertrophy using a novel PMCA4 specific inhibitor. Until now there is no known PMCA4 specific inhibitor so a library of 1280 medically optimised compounds was screened using a novel in vitro assay which measures the ATPase activity of PMCA4. The compound aurintricarboxylic acid (ATA) was identified, which inhibited PMCA4 ATPase activity with higher affinity (IC50= 100 nM) compared with related ATPases. In isolated neonatal rat cardiomyocytes, ATA showed dose dependent inhibition of phenylephrine-induced hypertrophy. In vivo studies showed that ATA (5mg/kg body weight/day IP) significantly reduced the development of pressure-overload induced hypertrophy in wild type mice following two weeks transverse aortic constriction (TAC). Echocardiography and haemodynamic analyses showed that ATA treatment significantly reduced the abnormal left ventricular remodelling after TAC compared with vehicle treatment. ATA treated TAC mice showed a significant reduction in the enlargement of heart weight/tibia length ratio as well as cardiomyocyte cross sectional surface area compared with vehicle treated TAC mice. A significant reduction in the expression of the hypertrophic markers ANP and BNP and, importantly, in the percentage of fibrosis was observed in ATA treated TAC mice compared with vehicle treated TAC mice. In addition, ATA treatment significantly reversed the already established pressure overload induced hypertrophy following three weeks TAC. ATA treatment to TAC mice led to a significant reduction in the expression of the bona fide calcineurin target MCIP1 and a reduction in NFAT phosphorylation level in vivo and NFAT transcriptional activity in vitro. ATA did not show a direct inhibition to the active form of calcineurin nor to the phosphatase activity of full length calcineurin.In conclusion, we have identified ATA as a novel and specific inhibitor to PMCA4 ATPase activity. Pharmacological inhibition of PMCA4 significantly reduces the hypertrophic response to pressure overload likely through inhibition of calcineurin/NFAT signalling.

No description available.

Vätgas kan framställas från förnybara energikällor genom vattenelektrolys med anjonbytande membran (AEMWE). AEMWE har vissa fördelar jämfört med traditionell alkalisk vattenelektrolys och elektrolysmed protonledande membran. Till exempel finns det möjlighet att använda alkalisk elektrolyt (även rent vatten) och billiga platinagruppsmetallfria katalysatorer tillsammans med ett anjonbytesmembran. Den största utmaningen med tekniken är att uppnå utmärkt och stabil prestanda för membran och elektroder. AemionTM anjonbytande membran (AEMs) av olika tjocklek, vattenupptag och kapacitet undersöktes i ett AEMWE system med 5 cm2 elektrodarea. Elektrokemisk prestanda hos dessa kommersiella AEM studerades med hjälp av porösa nickel elektroder. Bland de undersökta membranen visade AF2-HWP8-75-X stabil prestanda med en högfrekvent resistans (HFR) på 90 mΩ•cm2 och kunde nå en strömtäthet på 0,8 A/cm2 vid 2,38 V med 1 M KOH vid 60 ˚C.  AEMWE med AF2-HWP8-75-X och olika elektrodkombinationer undersöktes under samma driftsförhållanden. En elektrodkombination med Raney-Ni och NiFeO som katod respektive anod visade bäst prestanda under utvärderingen och gav en strömtäthet på 1,06 och 3,08 A/cm2 vid 2,00 respektive 2,32 V. KOH-lösningens temperatur och koncentration sänktes till 45 ˚C respektive 0,1 M för att undersöka effekten av driftsparametrar på flödescellens prestanda. Flödescellen uppvisade god stabilitet under de nya driftsförhållandena, men dess prestanda minskade avsevärt. Den nådde en strömtäthet på 0,8 A/cm2 vid 2,25 V. / Hydrogen can be produced from renewable energy sources using a novel anion exchange membrane water electrolysis (AEMWE) system. AEMWE has some benefits over the currently used state-of-the-art alkaline and proton exchange membrane water electrolysis systems. For instance, there is a possibility of using alkaline electrolytes (even pure water) and low-cost platinum-group-metal free catalysts together with an ion exchange membrane. However, the main challenge is that the AEMWE system should show excellent and stable performance, depending on the stability of the membrane and the electrodes. AemionTM anion exchange membranes (AEMs) of different thickness and water uptake capacity were investigated using a 5 cm2 AEMWE system. The electrochemical behaviour of these commercial AEMs was studied using nickel (Ni) felt electrodes. Among the investigated AEMs, the AF2-HWP8-75-X showed stable performance with a high frequency resistance (HFR) of 90 mΩ•cm2 and was able to reach a current density of 0.8 A/cm2 at 2.38 V using 1 M KOH at 60 ˚C.  AEMWE systems based on AF2-HWP8-75-X and different electrode combinations were examined under the same operating conditions. An electrode combination with Raney-Ni and NiFeO as cathode and anode, respectively, showed the best performance during the degradation test and provided a current density of 1.06 and 3.08 A/cm2 at 2.00 and 2.32 V, respectively. The operating temperature and concentration of the KOH solution were reduced to 45 ˚C and 0.1 M, respectively, to study the effect of operating parameters on the flow cell performance. The flow cell showed good stability under the new operating conditions, but its performance was reduced significantly. It reached a current density of 0.8 A/cm2 at 2.25 V.

Diese Dissertation befasst sich mit der industrienahen Herstellung von Katalysatorschichten für Polymer-Elektrolyt-Membran-Brennstoffzellen mit Hilfe des Tiefdrucks als Fertigungsverfahren. Um die Anforderungen an die Katalysatorschicht hinsichtlich der Schichtdicke zu erreichen, wird ein Linienraster für den Tiefdruck entwickelt. Das patentierte und verifizierte Designkonzept des Linienrasters ermöglicht es, trotz Tinten mit geringem Feststoffgehalt hohe Trockenschichtdicken zu erzeugen. Aufgrund des verwendeten Tiefdruckrasters sind Optimierungsschritte an der Fertigungsanlage notwendig, um eine hohe Schichtqualität zu erreichen. Schließlich werden kontinuierlich und industrienah Katalysatorschichten gefertigt, die als Membran-Elektroden-Einheit in einer Polymer-Elektrolyt-Membran-Brennstoffzelle erfolgreich eingesetzt werden. / This work presents an industrial close manufacturing process of active electrodes for Polymer Electrolyte Fuel Cells utilizing an adapted gravure printing process. To meet the requirements of the electrodes regarding the layer thickness (weight) and quality a novel line screen with maximized dipping volume for gravure printing was developed and investigated. A design rule for this kind of screens was realized and verified by a successful manufacturing of electrodes with different dried layer thicknesses. Due to the rough structure and the high dipping volumes of these line screens an adaption and optimization of the machinery and the whole process was necessary to achieve high quality electrodes. Finally, it is shown that it is possible to manufacture continuiously in an industrial close roll-to-roll process platinum loaded electrodes, working successful as cathode in a Membran-Electrode-Assembly.

Diese Dissertation befasst sich mit der industrienahen Herstellung von Katalysatorschichten für Polymer-Elektrolyt-Membran-Brennstoffzellen mit Hilfe des Tiefdrucks als Fertigungsverfahren. Um die Anforderungen an die Katalysatorschicht hinsichtlich der Schichtdicke zu erreichen, wird ein Linienraster für den Tiefdruck entwickelt. Das patentierte und verifizierte Designkonzept des Linienrasters ermöglicht es, trotz Tinten mit geringem Feststoffgehalt hohe Trockenschichtdicken zu erzeugen. Aufgrund des verwendeten Tiefdruckrasters sind Optimierungsschritte an der Fertigungsanlage notwendig, um eine hohe Schichtqualität zu erreichen. Schließlich werden kontinuierlich und industrienah Katalysatorschichten gefertigt, die als Membran-Elektroden-Einheit in einer Polymer-Elektrolyt-Membran-Brennstoffzelle erfolgreich eingesetzt werden. / This work presents an industrial close manufacturing process of active electrodes for Polymer Electrolyte Fuel Cells utilizing an adapted gravure printing process. To meet the requirements of the electrodes regarding the layer thickness (weight) and quality a novel line screen with maximized dipping volume for gravure printing was developed and investigated. A design rule for this kind of screens was realized and verified by a successful manufacturing of electrodes with different dried layer thicknesses. Due to the rough structure and the high dipping volumes of these line screens an adaption and optimization of the machinery and the whole process was necessary to achieve high quality electrodes. Finally, it is shown that it is possible to manufacture continuiously in an industrial close roll-to-roll process platinum loaded electrodes, working successful as cathode in a Membran-Electrode-Assembly.

Das Bakterium Legionella pneumophila vermehrt sich in Alveolarmakrophagen und kann zu einer Pneumonie, der Legionärskrankheit, führen. Phospholipasen können zur bakteriellen Pathogenität beitragen, indem sie den Wirt durch Zerstörung von Lipidstrukuren schädigen, oder über die Generation von „second messengern“ immunmodulatorisch wirken. Im Rahmen dieser Arbeit wurde die prominenteste zell-assoziierte und hämolytische Phospholipase A/Lysophospholipase A (PlaB) von L. pneumophila Corby charakterisiert und auf eine mögliche Virulenzassoziation hin untersucht. Die Bestimmung des Transkriptionsstartpunktes von plaB ermöglichte die Identifikation einer möglichen sigma70-Bindungsstelle. Die Transkriptionsrate ist relativ gering und nimmt zur stationären Phase hin ab, das Enzym ist vorwiegend exponentiell aktiv. Enzymatisch aktives PlaB-Protein ist zumindest zum Teil auf der oberflächenexponierten Seite der äußeren Membran lokalisiert. Der Transport des PlaB-Proteins ist nicht vom Tat-abhängigen Transport oder den Sekretionssystemen des Typ I, II oder IVB abhängig. Im Meerschweinchenmodell konnte eine Virulenzassoziation von PlaB nachgewiesen werden. PlaB-defiziente Bakterien zeigten eine geringere Replikationsrate in den Lungen und eine verminderte Kolonisierung der Milz. Vergleichende histologische Studien zeigten eine schwächer ausgeprägte Inflammation und Zerstörung der Lungen nach Infektion mit der plaB-Mutante. Somit handelt es sich bei PlaB um ein innerhalb der Spezies Legionella sehr weit verbreitetes Protein, welches in L. pneumophila Corby vorwiegend vor dem Eintritt in die stationäre Phase exprimiert wird. Enzymatisch aktives PlaB-Protein ist an der oberflächenexponierten Seite der äußeren Membran zu finden und spielt eine wichtige Rolle bei der Entstehung der Legionellen-Pneumonie. / The bacterium Legionella pneumophila replicates inside of alveolar macrophages and causes a severe pneumonia, the Legionnaires` disease. Bacterial phospholipases are well known virulence factors. Some cause cell lysis by pore formation, others generate second messengers and modulate the inflammatory response of the host. The aim of this work was to further characterize the major cell-associated hemolytic phospholipase A/lysophospholipase A activity (PlaB) of L. pneumophila Corby and to investigate a possible role of PlaB as virulence factor. Determination of the transcriptional start site of plaB allowed the identification of a possible sigma70-binding site. The transcription rate is relatively weak and decreases from exponential to stationary phase and enzymatic activity is most prominent in the exponential growth phases. Enzymatically active PlaB-protein is at least in parts localised on the surface-exposed side of the outer membrane. Studies with mutants of the Tat-dependent pathway and the type I, II, IVB secretion systems showed that these pathways are not involved in secretion of the PlaB-protein. Infection of guinea pigs revealed that PlaB plays an important role in proliferation of the bacteria in the lungs and dissemination to the spleen. Comparative histological studies revealed a less extensive inflammation and destruction of the lungs infected with the plaB-mutant strain. In summary, this work revealed that PlaB is a protein which is widespread within Legionella species. In L. pneumophila Corby, it is primarily expressed and active before stationary phase. Enzymatically active PlaB-protein is at least in parts located at the surface-exposed side of the outer membrane and contributes to the establishment of Legionnaires` disease.