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Der Steinkauz (Abb. 1) gehört zu den kleinsten Eulen Europas und steht auf der Roten Liste der gefährdeten Vogelarten. Im Kreis Höxter war er aus klimatischen Gründen nie häufig vertreten (PREYWISCH 1962) und Ende des letzten Jahrhunderts konnte nur noch ein einziges Steinkauzvorkommen verzeichnet werden (MEBS 2002). Jedoch kehrt er seit einigen Jahren wieder in den Kreis Höxter zurück (SINGER 2009). Dies war der Anlass zu der diesem Artikel zugrunde liegenden Bachelor-Thesis mit der Zielsetzung: Erfassung der Bestände im Nethetal (zusammen mit dem NABU Kreis Höxter; Überprüfung der Eignung des Nethetales als Lebensraum; Ableitung von Entwicklungsmaßnahmen zur Sicherung und Förderung des Steinkauzes.
Unter dem Anspruch, „so [zu] filmen, wie Kleist erzählt“, wagte sich 1976 der französische Filmemacher Eric Rohmer an die Verfilmung der 'Marquise von O....'. In seiner Überzeugung, die Wirkungsästhetik der Erzählung auch noch in der Verfilmung fortleben zu lassen, greift Rohmer auf ein gestalterisches Verfahren zurück, das wiederum unmittelbar auf Kleists ästhetische Kunstauffassung und den gemeinsamen Entstehungszeitraum der 'Marquise von O....' und des 'Zerbrochnen Krugs' zu verweisen scheint: Rohmer adaptierte die Erzählung nach eigener Aussage „Wort für Wort“, jedoch transformierte er auch das hinter dem Text befindliche Verfahren des bildhaften Erzählens in seinen Film. So zitiert er eine Vielzahl an Gemälden aus Kleists Zeit in den Film hinein, etwa von Caspar David Friedrich oder Jacques-Louis David, und offeriert damit einen filmischen Raum der Imagination, der unter Verwendung einer zeitgenössischen Interpretationsfolie eine Innensicht auf die darin befindlichen Figuren zu visualisieren vermag.
Aus der Sicht der deutschen Innenpolitik ist heute kaum eine andere inter-nationale Relation so brisant wie das Verhältnis zwischen Türken und Deutschen. Nicht erst seit Sarrazins Buch wird die Herausbildung und strukturelle Verfestigung einer neuen Kategorie des "Inländers", der Kategorie des "Deutschtürken", mit großem Argwohn betrachtet. Aber Sarrazin hat diesen Argwohn angeheizt, indem er das Thema in einer Weise angesprochen hat, die den Maximen der obwaltenden Medien- und Jetzt-rede-ich-Gesellschaft entspricht. Seither wird so laut auf "Klärung" gedrungen, dass selbst auf Verdrängung programmierte Ohren den Ruf nicht überhören können. Die Politik reagiert, will Gutes bewirken oder wenigstens die Scherben zusammenkehren und ruft sich selbst zur "integrationspolitischen" Ordnung. Man kündigt eine neue Offensive an, die sich reibungslos in das Netz der zahllosen Offensiven einfügt, die auf allen möglichen Feldern in unserer Offensivenzeit unternommen wurden und noch kommen werden. Dass die integrationspolitischen Blaupausen, die da entstehen sollen, eigentlich gar nicht von Integration im strikten Sinne, sondern von Assimilation handeln, spielt keine Rolle. Falsa demonstratio non nocet. Unterscheidungen stören nur, und "Multi-Kulti" ist tot, wie jeder weiß oder wissen müsste. ...
Blood vessel formation is a well orchestrated process where multiple components including different cells types, growth factors as well as extracellular matrix proteins act in synergistic and highly regulated manner to support the growth of new blood vessels. During embryonic development this process is marked as vasculogenesis and entails the differentiation of mesodermal cells into angioblasts and their subsequent fusion into a primitive vascular plexus. Angiogenesis, in contrast, describes the formation of new vessels from the pre-existing vasculature and it occurs in the embryo during remodeling of the primitive plexus into a mature vascular network. Furthermore, in the adult, angiogenic processes play a role in various physiological and pathological conditions. Angiogenesis is governed by a set of factors and molecular mechanisms whose identification has been a major focus of cardiovascular research for the past several decades. Most recently, Epidermal growth factor-like domain 7 (EGFL7) has been described as a novel molecular player in this context. This secreted protein is produced by endothelial cells and has been implicated in vessel development. Studies performed in zebrafish revealed an important role for EGFL7 in lumen formation during vasculogenesis although the underlying molecular mechanism has not been elucidated yet. In contrast, the investigation of EGFL7’s functions during angiogenic sprouting has faced several challenges and the role of EGFL7 in angiogenesis remained elusive. The purpose of this thesis was to identify the functions of EGFL7 during angiogenic mode of vessel formation in a systematic fashion using numerous in vitro as well as in vivo approaches.
Previously it has been suggested that EGFL7 might associate with the extracellular matrix from where it could exert its effects. Indeed, we could show that EGFL7 accumulates on the outer surface of endothelial cells in vivo by demonstrating its co-localization with collagen IV, a major constituent of the basal lamina. Furthermore, after its secretion to the extracellular matrix (ECM), EGFL7 seemed to interact with some components of the extracellular matrix including fibronectin and vitronectin, but not collagens and laminin.
A major group of receptors that mediate the interaction between the cells and the ECM are integrin receptors. Our co-immunoprecipitation studies revealed that EGFL7 associated with integrin αvβ3 which is highly expressed in endothelial cells and known to be important for vessel growth. Importantly, this EGFL7-αvβ3 integrin interaction was dependent on Arg-Gly-Asp (RGD) motif present within the second EGF-like domain of EGFL7 protein. Adhesion assays performed with human umbilical vein endothelial cells (HUVEC) revealed that EGFL7 promoted endothelial cell adhesion compared to BSA used as a negative control, however, adhesion seemed to be less efficient as compared to bona fide ECM proteins such as fibronectin and vitronectin. In addition, cultivation of endothelial cells on EGFL7 was characterized by the absence of mature focal adhesions and stress fibers, but was paralleled by increased phosphorylation of kinases typical for integrin activation signaling cascade such as FAK, Src and Akt. This led us to the hypothesis that EGFL7 creates an environment that supports a motile phenotype of endothelial cells by serving as a modulator of existing interactions between the cells and the surrounding matrix. Indeed, EGFL7 increased random migration of HUVEC on fibronectin in an αvβ3 integrin dependent manner as shown using a live cell imaging platform. Most importantly, this was paralleled by a decrease in endothelial cell adhesion to fibronectin which is consistent with previous reports on secreted proteins that support a medium strength of adhesion and such promote cellular migration. To assess the overall effect of EGFL7 on the process of blood formation several in vitro and in vivo approaches were employed. First, the addition of EGFL7 to Matrigel injected subcutaneously into mice significantly increased the invasion of endothelial cells into the plugs. Second, a spheroid-based sprouting assay in three-dimensional collagen matrix clearly demonstrated the ability of EGFL7 to support angiogenic sprouting in an integrin dependent manner. This is consistent with the observed effects of EGFL7 on endothelial cell migration. Third, using in vivo assays such as the chick chorioallantoic membrane (CAM) assay as well as a zebrafish model system we were able to validate the importance of the EGFL7-integrin interaction for the process of angiogenesis in vivo. Taken together, I identified some of the major cellular functions EGFL7 modulates during angiogenesis. In addition, with integrin αvβ3 I unraveled a novel interaction partner of EGFL7 that delivers a mechanistical explanation for EGFL7’s effects on blood vessel formation. Most importantly, data presented in this PhD thesis contribute substantially to the existing literature on EGFL7 unambiguously assigning a role for this protein in the process of angiogenesis.