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Wenn in einem verbrannten Gebäude, in dem sich unliebsame Untermieter breit gemacht haben, diese damit beginnen, Stein für Stein das restliche Gemäuer abzutragen, um die verbliebenen Fenster zuzumauern, wird es Zeit, mit mehr oder weniger freundlichen Worten die Bewohner des Hauses zu verweisen, die nur verhindern, dass sich neue Besucher dem Gelände nähern. Dafür muss freilich alter und neuer Behang von den Wänden genommen werden; und eben durch die Verbannung all dessen, was nicht an diesen Ort gehört, kann ein freundliches Bild des Dichters Friedrich Hölderlin erhalten bleiben, der nicht nur poetisch, sondern auch zwischenmenschlich einigen bedeutenden Persönlichkeiten seiner Zeit im Wege stand, was ihm wohl in beiden Aspekten zum Verhängnis geworden ist, weil er sich weder verwandtschaftlich noch im Rahmen des poetischen Geschäfts gegen seine intrigante Umgebung zur Wehr zu setzen wusste. Der etwas länger geratene Aufsatz „So sind die Zeichen in der Welt“ soll weder ein neues Heiligenbild schaffen noch einen frisch aus der Tasche gezogenen Popstar zum Liebhaben, sondern will behutsam einige Fresken des Gedankengebäudes Hölderlin für diejenigen freilegen, deren Bild des Dichters noch nicht völlig von der Vorstellung des wahnsinnig gewordenen Dichters übertüncht worden ist. Obwohl sich die Arbeit damit ganz bewusst den Hölderlin - Studien von Pierre Bertaux anschließt, setzt sie sich auch mit dieser Wahrnehmungslinie kritisch auseinander, indem sie neben biographischen Anmerkungen auch stil- und ideologiekritische Methoden einsetzt, um die manchmal unübersichtliche Quellenlage ein wenig durchsichtiger zu machen, als dies bisher der Fall ist. Über eine solche, in Einzelheiten vielleicht unorthodox wirkende Darstellung hinaus will die Arbeit die Behandlungsmöglichkeit von Friedrich Hölderlin im Deutschunterricht des Gymnasiums nahe legen, weil selbst Jüngeres über ihn behandelt wird, das darauf hinweist, inwiefern die Marginalisierung dieses Poeten damit zu tun hat, dass er während eines langen Abschnitts der Literaturgeschichte auch dafür verantwortlich gemacht wurde, was er weder geschrieben hat noch meinte. Die Intention der Arbeit besteht insgesamt in der Vorstellung, das Gedankengut Hölderlins müsse aus dem breiten Strom einer konservativen Wahrnehmungstradition entfernt werden (zu der beispielsweise auch die dramatische Hölderlin - Bearbeitung E. Jelineks Wolken.Heim. gezählt werden kann, selbst wenn sie widerborstig gemeint sein sollte) und dieser Dichter sei als realistischer Denker zu restaurieren, der sich deshalb dem Literaturbetrieb seiner Zeit entgezogen hat, weil er, selbst der Lebensführung nach, sehr früh die Bewegungen gegen französische Aufklärung und Revolution begriffen hat – und von deren massiver Ablehnung Hölderlin bis heute getroffen wird. Da Friedrich Hölderlin aber nicht nur ideologischer Betrachtung, Kritik und Verfälschung ausgesetzt ist, sondern auch regelmäßig Gegenstand umfangreicher biographisch - psychologischer Spekulationen darstellt, wurde dieser Aspekt nicht nur bezogen auf die Rezeptionsgeschichte untersucht, sondern am Gegenstand selbst. In diesem Zusammenhang konnte nicht nur eine bislang vernachlässigte Beziehung Hölderlins zu Sophie Mereau rekonstruiert und der Verdacht zurückgewiesen werden, es habe zur selben Zeit eine homoerotische Beziehung zu Isaak Sinclair bestanden, vielmehr gelang auch der Nachweis, dass das Verhältnis des Dichters zu Susette Gontard weder singulär noch konkurrenzlos gewesen ist, weshalb sich eine eindeutige Zuordnung dieser Frau zur poetischen Figur der Diotima verbietet. Dazu wurde einerseits der Umstand entmythologisiert, nach dem die Liebe zur Frankfurter Zeit platonisch betrieben wurde, andererseits aber diese Affaire den Verhältnissen Hölderlins zu anderen Frauen zugeordnet, mit denen sich Frau Gontard – letztlich erfolglos – dadurch auseinander zu setzen versuchte, dass sie die Rolle Diotimas okkupierte. Dabei ließ sich schließlich der Verdacht erhärten, die stabilste Bindung des Dichters an eine Frau sei die zur eigenen Schwester Heinrike gewesen, mit der bis zum Bruch von Bordeaux aus zwar unregelmäßig, aber emotional immer wieder ausufernde Briefe getauscht wurden. Es ist nicht ohne Ironie, wenn ausgerechnet im vielleicht bekanntesten Gedicht Hölderlins, der „Hälfte des Lebens“, in dem regelmäßig ein bedeutender philosophischer Entwurf gesehen wird, Rudimente eines Textes enthalten sind, der – eindeutig erotisch konnotiert – an die eigene Schwester gerichtet ist.
For the elucidation of the dynamics of signal transduction processes that are induced by cellular interactions, defined events along the signal transduction cascade and subsequent activation steps have to be analyzed and then also correlated with each other. This cannot be achieved by ensemble measurements because averaging biological data ignores the variability in timing and response patterns of individual cells and leads to highly blurred results. Instead, only a multi-parameter analysis at a single-cell level is able to exploit the information that is crucially needed for deducing the signaling pathways involved. The aim of this work was to develop a process line that allows the initiation of cell-cell or cell-particle interactions while at the same time the induced cellular reactions can be analyzed at various stages along the signal transduction cascade and correlated with each other. As this approach requires the gentle management of individually addressable cells, a dielectrophoresis (DEP)-based microfluidic system was employed that provides the manipulation of microscale objects with very high spatiotemporal precision and without the need of contacting the cell membrane. The system offers a high potential for automation and parallelization. This is essential for achieving a high level of robustness and reproducibility, which are key requirements in order to qualify this approach for a biomedical application. As an example process for intercellular communication, T cell activation has been chosen. The activation of the single T cells was triggered by contacting them individually with microbeads that were coated with antibodies directed against specific cell surface proteins, like the T cell receptor-associated kinase CD3 and the costimulatory molecule CD28 (CD; cluster of differentiation). The stimulation of the cells with the functionalized beads led to a rapid rise of their cytosolic Ca2+ concentration which was analyzed by a dual-wavelength ratiometric fluorescence measurement of the Ca2+-sensitive dye Fura-2. After Ca2+ imaging, the cells were isolated individually from the microfluidic system and cultivated further. Cell division and expression of the marker molecule CD69 as a late activation event of great significance were analyzed the following day and correlated with the previously recorded Ca2+ traces for each individual cell. It turned out such that the temporal profile of the Ca2+ traces between both activated and non-activated cells as well as dividing and non-dividing cells differed significantly. This shows that the pattern of Ca2+ signals in T cells can provide early information about a later reaction of the cell. As isolated cells are highly delicate objects, a precondition for these experiments was the successful adaptation of the system to maintain the vitality of single cells during and after manipulation. In this context, the influences of the microfluidic environment as well as the applied electric fields on the vitality of the cells and the cytosolic Ca2+ concentration as crucially important physiological parameters were thoroughly investigated. While a short-term DEP manipulation did not affect the vitality of the cells, they showed irregular Ca2+ transients upon exposure to the DEP field only. The rate and the strength of these Ca2+ signals depended on exposure time, electric field strength and field frequency. By minimizing their occurrence rate, experimental conditions were identified that caused the least interference with the physiology of the cell. The possibility to precisely control the exact time point of stimulus application, to simultaneously analyze short-term reactions and to correlate them with later events of the signal transduction cascade on the level of individual cells makes this approach unique among previously described applications and offers new possibilities to unravel the mechanisms underlying intercellular communication.
Due to the unique environmental conditions and different feedback mechanisms, the Arctic region is especially sensitive to climate changes. The influence of clouds on the radiation budget is substantial, but difficult to quantify and parameterize in models. In the framework of the PhD, elastic backscatter and depolarization lidar observations of Arctic clouds were performed during the international Arctic Study of Tropospheric Aerosol, Clouds and Radiation (ASTAR) from Svalbard in March and April 2007. Clouds were probed above the inaccessible Arctic Ocean with a combination of airborne instruments: The Airborne Mobile Aerosol Lidar (AMALi) of the Alfred Wegener Institute for Polar and Marine Research provided information on the vertical and horizontal extent of clouds along the flight track, optical properties (backscatter coefficient), and cloud thermodynamic phase. From the data obtained by the spectral albedometer (University of Mainz), the cloud phase and cloud optical thickness was deduced. Furthermore, in situ observations with the Polar Nephelometer, Cloud Particle Imager and Forward Scattering Spectrometer Probe (Laboratoire de Météorologie Physique, France) provided information on the microphysical properties, cloud particle size and shape, concentration, extinction, liquid and ice water content. In the thesis, a data set of four flights is analyzed and interpreted. The lidar observations served to detect atmospheric structures of interest, which were then probed by in situ technique. With this method, an optically subvisible ice cloud was characterized by the ensemble of instruments (10 April 2007). Radiative transfer simulations based on the lidar, radiation and in situ measurements allowed the calculation of the cloud forcing, amounting to -0.4 W m-2. This slight surface cooling is negligible on a local scale. However, thin Arctic clouds have been reported more frequently in winter time, when the clouds' effect on longwave radiation (a surface warming of 2.8 W m-2) is not balanced by the reduced shortwave radiation (surface cooling). Boundary layer mixed-phase clouds were analyzed for two days (8 and 9 April 2007). The typical structure consisting of a predominantly liquid water layer on cloud top and ice crystals below were confirmed by all instruments. The lidar observations were compared to European Centre for Medium-Range Weather Forecasts (ECMWF) meteorological analyses. A change of air masses along the flight track was evidenced in the airborne data by a small completely glaciated cloud part within the mixed-phase cloud system. This indicates that the updraft necessary for the formation of new cloud droplets at cloud top is disturbed by the mixing processes. The measurements served to quantify the shortcomings of the ECMWF model to describe mixed-phase clouds. As the partitioning of cloud condensate into liquid and ice water is done by a diagnostic equation based on temperature, the cloud structures consisting of a liquid cloud top layer and ice below could not be reproduced correctly. A small amount of liquid water was calculated for the lowest (and warmest) part of the cloud only. Further, the liquid water content was underestimated by an order of magnitude compared to in situ observations. The airborne lidar observations of 9 April 2007 were compared to space borne lidar data on board of the satellite Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). The systems agreed about the increase of cloud top height along the same flight track. However, during the time delay of 1 h between the lidar measurements, advection and cloud processing took place, and a detailed comparison of small-scale cloud structures was not possible. A double layer cloud at an altitude of 4 km was observed with lidar at the West coast in the direct vicinity of Svalbard (14 April 2007). The cloud system consisted of two geometrically thin liquid cloud layers (each 150 m thick) with ice below each layer. While the upper one was possibly formed by orographic lifting under the influence of westerly winds, or by the vertical wind shear shown by ECMWF analyses, the lower one might be the result of evaporating precipitation out of the upper layer. The existence of ice precipitation between the two layers supports the hypothesis that humidity released from evaporating precipitation was cooled and consequently condensed as it experienced the radiative cooling from the upper layer. In summary, a unique data set characterizing tropospheric Arctic clouds was collected with lidar, in situ and radiation instruments. The joint evaluation with meteorological analyses allowed a detailed insight in cloud properties, cloud evolution processes and radiative effects.
1. Problemstellung und Relevanz des Themas Die deutsche Hochschullandschaft hat in den letzten Jahren zahlreiche Veränderungen bewältigen müssen und steht weiterhin großen Herausforderungen gegenüber, durch welche sich zunehmend wettbewerbsähnliche Merkmale in diesem Sektor verfestigen: • Umstellung auf international vergleichbare Studiengänge • Neuregelung der Studienplatzvergabe • Einführung von Studiengebühren in einigen Bundesländern • Leistungsindikatoren zur Verteilung der staatlichen Haushaltsmittel • Demographischer Wandel Eine Bildungseinrichtung besitzt mehrere Anspruchsgruppen: die Studierenden, welche Bildungsleistungen nachfragen, den Staat, der für die Leistungen zahlt, die Öffentlichkeit, die an Grundlagenforschungen interessiert ist und schließlich die Wirtschaft, die Absolventen rekrutiert (vgl. Berthold, C. 2001, S.431). Die Hochschulen befinden sich untereinander verstärkt im Wettbewerb um qualifizierte (und ggf. zahlungswillige) Studierende, um finanzielle Mittel vom Staat oder aus der Privatwirtschaft und um renommierte Wissenschaftler. Hochschulen müssen sich nun den veränderten Bedingungen anpassen, um auch weiterhin im nationalen und internationalen Wettbewerb überlebensfähig zu bleiben. Grundsätzlich kann sich hierbei an in der Privatwirtschaft erfolgreich eingesetzten Marketinginstrumenten orientiert werden. 2. Zielsetzung und Aufbau der Arbeit Nach einer Analyse der oben genannten Rahmenbedingungen, wird im ersten Teil dieser Arbeit gezeigt, welche Erkenntnisse aus dem Marketing auf Hochschulen übertragen werden können. Dabei werden sowohl strategische Fragen beleuchtet als auch die Instrumente des Marketing-Mix vorgestellt. In einer anschließenden Untersuchung wurden Faktoren bestimmt, welche sich positiv auf den Entwicklungsstand von Marketingaktivitäten an Hochschulen auswirken. Dabei konnten - beispielhaft für die Region Berlin/Brandenburg - sechs verschiedene Hochschultypen identifiziert werden. Diese weisen, in Abhängigkeit der verschiedenen Eigenschaften der jeweiligen Institutionen, einen unterschiedlichen Entwicklungsstand oder ein anderes Verständnis von Hochschulmarketing auf. Aufgrund dessen erscheinen für sie jeweils andere Marketingstrategien empfehlenswert. Die größte Rolle für den differenzierten Status quo im Hochschulmarketing an Berliner und Brandenburger Hochschulen spielt die Stärke des äußeren Drucks unter dem sich die Hochschule befindet, um ihre Auslastung und die notwendige finanzielle Ausstattung sicherzustellen. Ferner unterscheiden sich die Hochschulleitungen erheblich in ihrem Engagement und der Bereitschaft, diesen Herausforderungen mit Marketinginstrumenten zu begegnen. Trotz der gestiegenen Anzahl von Beiträgen zur Notwendigkeit der Einführung von ökonomischen Überlegungen auch im Hochschulmanagement gibt es viele Kritiker, die ein Ende der Freiheit für Forschung und Lehre prophezeien, wenn der Marketing-Gedanke verstärkt auch an Bildungseinrichtungen Einzug hält. Unumstritten ist, dass Managementansätze aus der privaten Wirtschaft nicht ohne weiteres auf eine Hochschule adaptiert werden können. Wahrscheinlich besteht jedoch die größere Gefahr für Freiheit und Erfolg von Forschung und Lehre in der Missachtung dieser aktuellen Tendenzen (vgl. Tutt 2006, S. 171)!
The Earth’s magnetic field (EMF) is generated by convections in the electrically conducting liquid iron-rich outer core, modified by the Earth’s rotation. A drastic manifestation of the dynamics of this fluid body is the occurrence of geomagnetic field reversals in the Earth’s history but also geomagnetic excursions, which are more frequent features of otherwise stable polarity chrons, but often poorly constrained in the geological record. To better understand the origin of the field, we need to know how the field has varied on different geological timescales. This includes not only information about changes in the ancient field’s direction but also about the absolute intensity (palaeointensity) and the age. This palaeointensity record is needed for compiling a full-vector description of the field. A palaeomagnetic and palaeointensity study on lava flows allows gaining insights about the evolution of the EMF through time and space. However, constraining the EMF evolution over different geological timescales remains a difficult objective due to the paucity of available palaeointensity data. One new alternative approach in palaeointensity studies is the recently proposed multispecimen parallel differential pTRM (MS) method, which has potentially several advantages over the commonly used Thellier method, because it is in theory independent of magnetic domain state, less prone to biasing effects, such as thermal alteration and significantly faster to perform in the laboratory. A study of highly active volcanic regions, such as the Trans-Mexican Volcanic Belt, seems promising when attempting a full-vector reconstruction or when looking for field excursions. One aim of this thesis was to gain new information about the occurrence and global validity of geomagnetic excursions from the Brunhes- or Matuyama Chron. For this purpose some 75 lava flows from within the Trans-Mexican Volcanic Belt were sampled for palaeomagnetic analyses. The scatter of virtual geomagnetic poles from lavas younger than 1.7 Ma was used for estimating palaeosecular variation and was found to be consistent with latitude dependent Model G and other high quality palaeomagnetic data from Mexico. The palaeomagnetic mean-vectors of 56 lavas were correlated to the Geomagnetic Polarity Timescale supplemented with information on geomagnetic excursions. On the grounds of their associated radioisotopic ages, four lavas were tentatively correlated with known excursions from marine records. Two lava flows dating of Brunhes Chron were associated with the Big Lost and Delts/Stage 17 excursions, respectively. From further two flows dating of Matuyama Chron, one flow was associated with either the Santa Rosa- or Kamikatsura excursions, while the other could have been emplaced during the Gilsa excursion. The most significant outcome was the finding that both Brunhes excursional flows display nearly fully reversed directions that deviate almost 180°C from the expected normal polarity direction. This observation could indicate that in particular the Big Lost and Delta/Stage17 excursions may represent other short periods during which the field completed a full reversal for a short time, such as was previously found for other older cryptochrons or tiny wiggles. Another focus of this thesis was set on estimating the feasibility of the new MS method for routine palaeointensity determination. This was accomplished by applying the MS method to samples from 11 historical lava flows from Mexico and Iceland from which the actual field intensity was either known from contemporary observatory data, or deduced from magnetic field models. Comparing observed with expected intensity values allowed to test the accuracy of the MS method. It a was found that the majority of palaeointensity estimates after the MS method yielded results that were very close or indistinguishable within the range of uncertainty from the expected values. However, a general trend towards an overestimate in the palaeointensity was also observed, which, on the grounds of corroborating rock magnetic analyses, was associated with multidomain material. This observation was taken as first evidence that the MS method is not entirely independent of magnetic domain state, as was originally claimed. However, a second experiment in which a modification of the most widely used Thellier method was applied to sister samples from 5 Icelandic flows revealed that, in comparison to the MS method, the latter produced more accurate and statistically better defined palaeointensities. Thus, from these first results, the MS method appeared as a viable alternative for future palaeointensity studies. Subsequently it was attempted to corroborate the directional record from Mexican lavas with palaeointensity data. It was possible to acquire palaeointensity estimates for 32 out of 51 investigated lava flows. These new results revealed that the new MS palaeointensities for Mexico are, with a high degree of statistical significance, around 30% higher than expected. The generally high palaeointensities seem to corroborate the results obtained from historical lava flows in this study and other previous studies on synthetic samples where domain state effects were found to cause overestimates in the palaeointensity of up to 30 per cent in the MS method. The primary process that leads to this overestimate is assigned to an asymmetry in the demagnetisation and remagnetisation process. Yet, this overestimate is expected to be no larger than what might be expected from Thellier experiments performed on samples with a given degree of multidomain behaviour.
The Tibetan Plateau is the largest elevated landmass in the world and profoundly influences atmospheric circulation patterns such as the Asian monsoon system. Therefore this area has been increasingly in focus of palaeoenvironmental studies. This thesis evaluates the applicability of organic biomarkers for palaeolimnological purposes on the Tibetan Plateau with a focus on aquatic macrophyte-derived biomarkers. Submerged aquatic macrophytes have to be considered to significantly influence the sediment organic matter due to their high abundance in many Tibetan lakes. They can show highly 13C-enriched biomass because of their carbon metabolism and it is therefore crucial for the interpretation of δ13C values in sediment cores to understand to which extent aquatic macrophytes contribute to the isotopic signal of the sediments in Tibetan lakes and in which way variations can be explained in a palaeolimnological context. Additionally, the high abundance of macrophytes makes them interesting as potential recorders of lake water δD. Hydrogen isotope analysis of biomarkers is a rapidly evolving field to reconstruct past hydrological conditions and therefore of special relevance on the Tibetan Plateau due to the direct linkage between variations of monsoon intensity and changes in regional precipitation / evaporation balances. A set of surface sediment and aquatic macrophyte samples from the central and eastern Tibetan Plateau was analysed for composition as well as carbon and hydrogen isotopes of n-alkanes. It was shown how variable δ13C values of bulk organic matter and leaf lipids can be in submerged macrophytes even of a single species and how strongly these parameters are affected by them in corresponding sediments. The estimated contribution of the macrophytes by means of a binary isotopic model was calculated to be up to 60% (mean: 40%) to total organic carbon and up to 100% (mean: 66%) to mid-chain n-alkanes. Hydrogen isotopes of n-alkanes turned out to record δD of meteoric water of the summer precipitation. The apparent enrichment factor between water and n-alkanes was in range of previously reported ones (≈-130‰) at the most humid sites, but smaller (average: -86‰) at sites with a negative moisture budget. This indicates an influence of evaporation and evapotranspiration on δD of source water for aquatic and terrestrial plants. The offset between δD of mid- and long-chain n-alkanes was close to zero in most of the samples, suggesting that lake water as well as soil and leaf water are affected to a similar extent by those effects. To apply biomarkers in a palaeolimnological context, the aliphatic biomarker fraction of a sediment core from Lake Koucha (34.0° N; 97.2° E; eastern Tibetan Plateau) was analysed for concentrations, δ13C and δD values of compounds. Before ca. 8 cal ka BP, the lake was dominated by aquatic macrophyte-derived mid-chain n-alkanes, while after 6 cal ka BP high concentrations of a C20 highly branched isoprenoid compound indicate a predominance of phytoplankton. Those two principally different states of the lake were linked by a transition period with high abundances of microbial biomarkers. δ13C values were relatively constant for long-chain n-alkanes, while mid-chain n-alkanes showed variations between -23.5 to -12.6‰. Highest values were observed for the assumed period of maximum macrophyte growth during the late glacial and for the phytoplankton maximum during the middle and late Holocene. Therefore, the enriched values were interpreted to be caused by carbon limitation which in turn was induced by high macrophyte and primary productivity, respectively. Hydrogen isotope signatures of mid-chain n-alkanes have been shown to be able to track a previously deduced episode of reduced moisture availability between ca. 10 and 7 cal ka BP, indicated by a 20‰ shift towards higher δD values. Indications for cooler episodes at 6.0, 3.1 and 1.8 cal ka BP were gained from drops of biomarker concentrations, especially microbial-derived hopanoids, and from coincidental shifts towards lower δ13C values. Those episodes correspond well with cool events reported from other locations on the Tibetan Plateau as well as in the Northern Hemisphere. To conclude, the study of recent sediments and plants improved the understanding of factors affecting the composition and isotopic signatures of aliphatic biomarkers in sediments. Concentrations and isotopic signatures of the biomarkers in Lake Koucha could be interpreted in a palaeolimnological context and contribute to the knowledge about the history of the lake. Aquatic macrophyte-derived mid-chain n-alkanes were especially useful, due to their high abundance in many Tibetan Lakes and their ability to record major changes of lake productivity and palaeo-hydrological conditions. Therefore, they have the potential to contribute to a fuller understanding of past climate variability in this key region for atmospheric circulation systems.
Hohe Leistungsansprüche im Wettkampfsport erfordern von den Athleten eine hohe sportliche Belastbarkeit. Möglichkeiten die Trainingsumfänge und -intensitäten zu erhöhen, sind z.T. ausgeschöpft. So bestehen nach wie vor Bestrebungen neue Wege zu finden, um mögliche Leistungsreserven zu erschließen. Elektrotherapieverfahren haben sich im klinischen Alltag, u.a. zur Behandlung von Traumata, bewährt und werden häufig zum Zweck der Analgesierung, Verbesserung der Gewebedurchblutung und zur Muskelstimulation angewandt. Deren Einsatz im adjuvanten Bereich der Trainingsbegleitung wurde bislang nur vereinzelt beschrieben. In der vorliegenden Studie wurden die Auswirkungen einer elektromagnetischen Anwendungsform auf ausgewählte psycho-physische Parameter untersucht (Kontrollgruppenvergleich mit placebokontrolliertem Design), um Aussagen über praxisrelevante Ansätze zur trainingsunterstützenden Betreuung abzuleiten. Es stellte sich die Frage, ob eine Intervention (15 x / 4 Wo.) mit frequenzmodulierten Wechselströmen im vorwiegend niederfrequenten Wirkungsspektrum (0-10000Hz, 5 μA / cm², CellVAS®) zu einer Beeinflussung der untersuchten Parameter führen und dahingehend nachhaltige leistungsfördernde oder -reduzierende Effekte erzielt werden könnten. Des Weiteren sollte geprüft werden, inwiefen die erhobenen Parameter (PWC170, Squat-Jump, Lateralflexion der Wirbelsäule und SF36®) aussagekräftig genug sind. Die Wirksamkeit des Applikationsform wurde im Prä-Post-Vergleich vor (T1), nach (T2) und 4 Wo. nach Abschluss (T3, Nachhaltigkeit) der Intervention analysiert. Die Teilnehmer der Kontrollgruppe erhielten vergleichbare Applikationen im Placebomodus. Das Probandenkollektiv bestand aus gesunden Leistungssportlern, deren Sportarten einen hohen Kraftausdaueranteil enthielten (n=127). Die Gruppenzuteilung erfolgte teilrandomisiert in Haupt- (HG) und Kontrollgruppe (KG). Zudem wurden die Gruppen zusätzlich geschlechtsspezifisch getrennt. Im Untersuchungsverlauf ließen sich Veränderungen für die Leistungsparameter PWC170 und Squat Jump erkennen. Inwiefern diese Abweichungen auf den Einfluss der Intervention mit frequenzmodulierten Wechselströmen im niederfrequenten Wirkungsspektrum zurückzuführen sind, konnte in dieser Untersuchung nicht eindeutig geklärt werden. Die nachgewiesenen Effekte ließen sich nach den zu Grunde liegenden wissenschaftlichen Standards nicht statistisch valide belegen. Der wissenschaftliche Nachweis einer mögliche Leistungsveränderung konnte nicht abschließend erbracht werden. Im therapeutischen Bereich hat die untersuchte Applikationsform, auf Basis der bestehen Studienlage, ihre Anwendung gefunden und kann bedenkenlos verwendet werden. Für den Einsatz als unterstützendes Verfahren in der sportlichen Praxis besteht nach wie vor Bedarf an validen, randomisierten Studien, die die Wirksamkeit der Applikationsform auf psycho-physische Parameter von Athleten nachhaltig belegen, bevor sie in der sportlichen Praxis Anwendung finden sollten.
Das homotrimere Tailspikeadhäsin des Bakteriophagen P22 ist ein etabliertes Modellsystem, dessen Faltung, Assemblierung und Stabilität in vivo und in vitro umfassend charakterisiert ist. Das zentrale Strukturmotiv des Proteins ist eine parallele beta-Helix mit 13 Windungen, die von einer N‑terminalen Kapsidbindedomäne und einer C‑terminalen Trimerisierungsdomäne flankiert wird. Jede Windung beinhaltet drei kurze beta-Stränge, die durch turns und loops unterschiedlicher Länge verbunden sind. Durch den sich strukturell wiederholenden, spulenförmigen Aufbau formen beta-Stränge benachbarter Windungen elongierte beta-Faltblätter. Das Lumen der beta-Helix beinhaltet größtenteils hydrophobe Seitenketten, welche linear und sehr regelmäßig entlang der Längsachse gestapelt sind. Eine hoch repetitive Struktur, ausgedehnte beta-Faltblätter und die regelmäßige Anordnung von ähnlichen oder identischen Seitenketten entlang der beta-Faltblattachse sind ebenfalls typische Kennzeichen von Amyloidfibrillen, die bei Proteinfaltungskrankheiten wie Alzheimer, der Creutzfeld-Jakob-Krankheit, Chorea Huntington und Typ-II-Diabetes gebildet werden. Es wird vermutet, dass die hohe Stabilität des Tailspikeproteins und auch die der Amyloidfibrille durch Seitenkettenstapelung, einem geordneten Netzwerk von Wasserstoffbrückenbindungen und den rigiden, oligomeren Verbund bedingt ist. Um den Einfluss der Seitenkettenstapelung auf die Stabilität, Faltung und Struktur des P22 Tailspikeproteins zu untersuchen, wurden sieben Valine in einem im Lumen der beta-Helix begrabenen Seitenkettenstapel gegen das kleinere und weniger hydrophobe Alanin und das voluminösere Leucin substituiert. Der Einfluss der Mutationen wurde anhand zweier Tailspikevarianten, dem trimeren, N‑terminal verkürzten TSPdeltaN‑Konstrukt und der monomeren, isolierten beta-Helix Domäne analysiert. Generell wurde in den Experimenten deutlich, dass Mutationen zu Alanin stärkere Effekte auslösen als Mutationen zu Leucin. Die dichte und hydrophobe Packung im Kern der beta-Helix bildet somit die Basis für Stabilität und Faltung des Proteins. Anhand hoch aufgelöster Kristallstrukturen jeweils zweier Alanin‑ und Leucin‑Mutanten konnte verdeutlicht werden, dass das Strukturmotiv der parallelen beta-Helix stark formbar ist und mutationsbedingte Änderungen des Seitenkettenvolumens durch kleine und lokale Verschiebung der Haupt‑ und Seitenketten ausgeglichen werden, sodass mögliche Kavitäten gefüllt und sterische Spannung abgebaut werden können. Viele Mutanten zeigten in vivo und in vitro einen temperatursensitiven Faltungsphänotyp (temperature sensitive for folding, tsf), d.h. bei Temperaturerhöhung waren die Ausbeuten des N‑terminal verkürzten Trimers im Vergleich zum Wildtyp deutlich verringert. Weiterführende Experimente zeigten, dass der tsf‑Phänotyp durch die Beeinflussung unterschiedlicher Stadien des Reifungsprozesses oder auch durch die Verminderung der kinetischen Stabilität des nativen Trimers ausgelöst wurde. Durch Untersuchungen am vollständigen und am N‑terminal verkürzten Wildtypprotein wurde gezeigt, dass die Entfaltungsreaktion des Tailspiketrimers komplex ist. Die Verläufe der Kinetiken folgen zwar einem apparenten Zweizustandsverhalten, jedoch sind bei Darstellung der Entfaltungsäste im Chevronplot die Abhängigkeiten der Geschwindigkeitskonstanten vom Denaturierungsmittel nicht linear, sondern in unterschiedliche Richtungen gewölbt. Dieses Verhalten könnte durch ein hoch energetisches Entfaltungsintermediat, einen breiten Übergangsbereich oder parallele Entfaltungswege hervorgerufen sein. Mit Hilfe der monomeren, isolierten beta-Helix Domäne, bei der die N‑terminale Capsidbindedomäne und die C‑terminale Trimerisierungsdomäne deletiert sind und welche als unabhängige Faltungseinheit fungiert, wurde gezeigt, dass alle Mutanten im Harnstoff‑induzierten Gleichgewicht analog zum Wildtypprotein einem Zweizustandsverhalten mit vergleichbaren Kooperativitäten folgen. Die konformationellen Stabilitäten von in der beta-Helix zentral gelegenen Alanin‑ und Leucin‑Mutanten sind stark vermindert, während Mutationen in äußeren Bereichen der Domäne keinen Einfluss auf die Stabilität der beta-Helix haben. Bei Verlängerung der Inkubationszeiten der Gleichgewichtsexperimente konnte die langsame Bildung von Aggregaten im Übergangsbereich der destabilisierten Mutanten detektiert werden. Die in der Arbeit erlangten Erkenntnisse lassen vermuten, dass die isolierte beta-Helix einem für die Reifung des Tailspikeproteins entscheidenden thermolabilen Faltungsintermediat auf Monomerebene sehr ähnlich ist. Im Intermediat ist ein zentraler Kern, der die Windungen 4 bis 7 und die „Rückenflosse“ beinhaltet, stabilitätsbestimmend. Dieser Kern könnte als Faltungsnukleus dienen, an den sich sequenziell weitere Helixwindungen anlagern und im Zuge der „Monomerreifung“ kompaktieren.
To date, positive relationships between diversity and community biomass have been mainly found, especially in terrestrial ecosystems due to the complementarity and/or dominance effect. In this thesis, the effect of diversity on the performance of terrestrial plant and phytoplankton communities was investigated to get a better understanding of the underlying mechanisms in the biodiversity-ecosystem functioning context. In a large grassland biodiversity experiment, the Jena Experiment, the effect of community diversity on the individual plant performance was investigated for all species. The species pool consisted of 60 plant species belonging to 4 functional groups (grasses, small herbs, tall herbs, legumes). The experiment included 82 large plots which differed in species richness (1-60), functional richness (1-4), and community composition. Individual plant height increased with increasing species richness suggesting stronger competition for light in more diverse communities. The aboveground biomass of the individual plants decreased with increasing species richness indicating stronger competition in more species-rich communities. Moreover, in more species-rich communities plant individuals were less likely to flower out and had fewer inflorescences which may be resulting from a trade-off between resource allocation to vegetative height growth and to reproduction. Responses to changing species richness differed strongly between functional groups and between species of similar functional groups. To conclude, individual plant performance can largely depend on the diversity of the surrounding community. Positive diversity effects on biomass have been mainly found for substrate-bound plant communities. Therefore, the effect of diversity on the community biomass of phytoplankton was studied using microcosms. The communities consisted of 8 algal species belonging to 4 functional groups (green algae, diatoms, cyanobacteria, phytoflagellates) and were grown at different functional richness levels (1-4). Functional richness and community biomass were negatively correlated and all community biomasses were lower than their average monoculture biomasses of the component species, revealing community underyielding. This was mainly caused by the dominance of a fast-growing species which built up low biomasses in monoculture and mixture. A trade-off between biomass and growth rate in monoculture was found for all species, and thus fast-growing species built up low biomasses and slow-growing species reached high biomasses in monoculture. As the fast-growing, low-productive species monopolised nutrients in the mixtures, they became the dominant species resulting in the observed community underyielding. These findings suggest community overyielding when biomasses of the component species are positively correlated with their growth rates in monocultures. Aquatic microcosm experiments with an extensive design were performed to get a broad range of community responses. The phytoplankton communities differed in species diversity (1, 2, 4, 8, and 12), functional diversity (1, 2, 3, and 4) and community composition. The species/functional diversity positively affected community biomass, revealing overyielding in most of the communities. This was mainly caused by a positive complementarity effect which can be attributed to resource use complementarity and/or facilitative interaction among the species. Overyielding of more diverse communities occurred when the biomass of the component species was correlated positively with their growth rates in monoculture and thus, fast-growing and high-productive species were dominant in mixtures. This and the study mentioned above generated an emergent pattern for community overyielding and underyielding from the relationship between biomass and growth rate in monoculture as long as the initial community structure prevailed. Invasive species can largely affect ecosystem processes, whereas invasion is also influenced by diversity. To date, studies revealed negative and positive diversity effects on the invasibility (susceptibility of a community to the invasion by new species). The effect of productivity (nutrient concentration ranging from 10 to 640 µg P L-1), herbivory (presence/absence of the generalist feeder) and diversity (3, 4, 6 species were randomly chosen from the resident species pool) on the invasibility of phytoplankton communities consisting of 10 resident species was investigated using semi-continuous microcosms. Two functionally diverse invaders were chosen: the filamentous and less-edible cynaobacterium C. raciborskii and the unicellular and well-edible phytoflagellate Cryptomonas sp. The phytoflagellate indirectly benefited from grazing pressure of herbivores whereas C. raciborskii suffered more from it. Diversity did not affect the invasibility of the phytoplankton communities. Rather, it was strongly influenced by the functional traits of the resident and invasive species.
Der Streifenkiwi (Apteryx mantelli) kommt im Freiland nur auf der Nordinsel Neuseelands vor. Aufgrund des gefährdeten Bestands ist eine sich selbst erhaltene Zoopopulation wichtig. Kenntnisse des Verhaltens helfen, die Ansprüche der Tiere zu verstehen. Zudem können sie darüber Auskunft geben, inwiefern das Wohlbefinden eines Tieres gegeben ist. Durch die Untersuchung der Brutaktivität sollte ein Überblick über den allgemeinen Verlauf der Brut gegeben und Aktivitätsmuster für den Berliner Hahn erarbeitet werden, um den Verlauf zukünftiger Bruten einschätzen und eventuell positiv beeinflussen zu können. Dazu kamen die Untersuchung der täglichen Aktivität einer Henne sowie Beobachtungen des Verhaltens der Tiere. Diese dienten der Bestandsaufnahme der gezeigten Verhaltensweisen und sollten zusammen mit der Aktivität die Grundlage zur Einschätzung bilden, ob die Ansprüche der Kiwis im Zoo Berlin erfüllt werden, und Hinweise zur Verbesserung der Haltung geben. Die Brutaktivität des Hahnes konnte über drei Brutperioden hinweg detailliert dargestellt werden und zeigte, dass nicht nur innerhalb der Art sondern bei einem einzigen Tier unter ähnlichen Bedingungen die Variabilität so groß sein kann, dass sie für Vorhersagen über den Erfolg einer Brut nicht geeignet ist. Im Zusammenhang mit der Aktivität der Henne ließen sich keine Auffälligkeiten erkennen, die auf eine allgemeine Störung der Tiere schließen lassen oder für eine Beeinträchtigung der Brut verantwortlich gemacht werden könnten. Soweit aus den Beobachtungen im Freiland geschlossen werden kann, scheinen die Kiwis im Zoo ein weitgehend natürliches Verhalten zu zeigen. Die Haltungsbedingungen scheinen den Ansprüchen der Tiere zu entsprechen. Es ließen sich nur bedingt Strategien entwickeln, um die Bedingungen für die Brut und damit für die Nachzucht zu verbessern, da sich die Aktivität des Hahnes während der Brut von Jahr zu Jahr als unerwartet variabel erwies. Für ein weiteres Verständnis des Brutverhaltens und eine mögliche Verbesserung der Bedingungen wäre eine Untersuchung zum Einfluss verschiedener Umweltfaktoren auf die Brutaktivität des Hahnes wünschenswert.
We study buckling instabilities of filaments in biological systems. Filaments in a cell are the building blocks of the cytoskeleton. They are responsible for the mechanical stability of cells and play an important role in intracellular transport by molecular motors, which transport cargo such as organelles along cytoskeletal filaments. Filaments of the cytoskeleton are semiflexible polymers, i.e., their bending energy is comparable to the thermal energy such that they can be viewed as elastic rods on the nanometer scale, which exhibit pronounced thermal fluctuations. Like macroscopic elastic rods, filaments can undergo a mechanical buckling instability under a compressive load. In the first part of the thesis, we study how this buckling instability is affected by the pronounced thermal fluctuations of the filaments. In cells, compressive loads on filaments can be generated by molecular motors. This happens, for example, during cell division in the mitotic spindle. In the second part of the thesis, we investigate how the stochastic nature of such motor-generated forces influences the buckling behavior of filaments. In chapter 2 we review briefly the buckling instability problem of rods on the macroscopic scale and introduce an analytical model for buckling of filaments or elastic rods in two spatial dimensions in the presence of thermal fluctuations. We present an analytical treatment of the buckling instability in the presence of thermal fluctuations based on a renormalization-like procedure in terms of the non-linear sigma model where we integrate out short-wavelength fluctuations in order to obtain an effective theory for the mode of the longest wavelength governing the buckling instability. We calculate the resulting shift of the critical force by fluctuation effects and find that, in two spatial dimensions, thermal fluctuations increase this force. Furthermore, in the buckled state, thermal fluctuations lead to an increase in the mean projected length of the filament in the force direction. As a function of the contour length, the mean projected length exhibits a cusp at the buckling instability, which becomes rounded by thermal fluctuations. Our main result is the observation that a buckled filament is stretched by thermal fluctuations, i.e., its mean projected length in the direction of the applied force increases by thermal fluctuations. Our analytical results are confirmed by Monte Carlo simulations for buckling of semiflexible filaments in two spatial dimensions. We also perform Monte Carlo simulations in higher spatial dimensions and show that the increase in projected length by thermal fluctuations is less pronounced than in two dimensions and strongly depends on the choice of the boundary conditions. In the second part of this work, we present a model for buckling of semiflexible filaments under the action of molecular motors. We investigate a system in which a group of motors moves along a clamped filament carrying a second filament as a cargo. The cargo-filament is pushed against the wall and eventually buckles. The force-generating motors can stochastically unbind and rebind to the filament during the buckling process. We formulate a stochastic model of this system and calculate the mean first passage time for the unbinding of all linking motors which corresponds to the transition back to the unbuckled state of the cargo filament in a mean-field model. Our results show that for sufficiently short microtubules the movement of kinesin-I-motors is affected by the load force generated by the cargo filament. Our predictions could be tested in future experiments.
Recent years witnessed a vast advent of stalagmites as palaeoclimate archives. The multitude of geochemical and physical proxies and a promise of a precise and accurate age model greatly appeal to palaeoclimatologists. Although substantial progress was made in speleothem-based palaeoclimate research and despite high-resolution records from low-latitudinal regions, proving that palaeo-environmental changes can be archived on sub-annual to millennial time scales our comprehension of climate dynamics is still fragmentary. This is in particular true for the summer monsoon system on the Indian subcontinent. The Indian summer monsoon (ISM) is an integral part of the intertropical convergence zone (ITCZ). As this rainfall belt migrates northward during boreal summer, it brings monsoonal rainfall. ISM strength depends however on a variety of factors, including snow cover in Central Asia and oceanic conditions in the Indic and Pacific. Presently, many of the factors influencing the ISM are known, though their exact forcing mechanism and mutual relations remain ambiguous. Attempts to make an accurate prediction of rainfall intensity and frequency and drought recurrence, which is extremely important for South Asian countries, resemble a puzzle game; all interaction need to fall into the right place to obtain a complete picture. My thesis aims to create a faithful picture of climate change in India, covering the last 11,000 ka. NE India represents a key region for the Bay of Bengal (BoB) branch of the ISM, as it is here where the monsoon splits into a northwestward and a northeastward directed arm. The Meghalaya Plateau is the first barrier for northward moving air masses and receives excessive summer rainfall, while the winter season is very dry. The proximity of Meghalaya to the Tibetan Plateau on the one hand and the BoB on the other hand make the study area a key location for investigating the interaction between different forcings that governs the ISM. A basis for the interpretation of palaeoclimate records, and a first important outcome of my thesis is a conceptual model which explains the observed pattern of seasonal changes in stable isotopes (d18O and d2H) in rainfall. I show that although in tropical and subtropical regions the amount effect is commonly called to explain strongly depleted isotope values during enhanced rainfall, alone it cannot account for observed rainwater isotope variability in Meghalaya. Monitoring of rainwater isotopes shows no expected negative correlation between precipitation amount and d18O of rainfall. In turn I find evidence that the runoff from high elevations carries an inherited isotopic signature into the BoB, where during the ISM season the freshwater builds a strongly depleted plume on top of the marine water. The vapor originating from this plume is likely to memorize' and transmit further very negative d18O values. The lack of data does not allow for quantication of this plume effect' on isotopes in rainfall over Meghalaya but I suggest that it varies on seasonal to millennial timescales, depending on the runoff amount and source characteristics. The focal point of my thesis is the extraction of climatic signals archived in stalagmites from NE India. High uranium concentration in the stalagmites ensured excellent age control required for successful high-resolution climate reconstructions. Stable isotope (d18O and d13C) and grey-scale data allow unprecedented insights into millennial to seasonal dynamics of the summer and winter monsoon in NE India. ISM strength (i. e. rainfall amount) is recorded in changes in d18Ostalagmites. The d13C signal, reflecting drip rate changes, renders a powerful proxy for dry season conditions, and shows similarities to temperature-related changes on the Tibetan Plateau. A sub-annual grey-scale profile supports a concept of lower drip rate and slower stalagmite growth during dry conditions. During the Holocene, ISM followed a millennial-scale decrease of insolation, with decadal to centennial failures resulting from atmospheric changes. The period of maximum rainfall and enhanced seasonality corresponds to the Holocene Thermal Optimum observed in Europe. After a phase of rather stable conditions, 4.5 kyr ago, the strengthening ENSO system dominated the ISM. Strong El Nino events weakened the ISM, especially when in concert with positive Indian Ocean dipole events. The strongest droughts of the last 11 kyr are recorded during the past 2 kyr. Using the advantage of a well-dated stalagmite record at hand I tested the application of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) to detect sub-annual to sub-decadal changes in element concentrations in stalagmites. The development of a large ablation cell allows for ablating sample slabs of up to 22 cm total length. Each analyzed element is a potential proxy for different climatic parameters. Combining my previous results with the LAICP- MS-generated data shows that element concentration depends not only on rainfall amount and associated leaching from the soil. Additional factors, like biological activity and hydrogeochemical conditions in the soil and vadose zone can eventually affect the element content in drip water and in stalagmites. I present a theoretical conceptual model for my study site to explain how climatic signals can be transmitted and archived in stalagmite carbonate. Further, I establish a first 1500 year long element record, reconstructing rainfall variability. Additionally, I hypothesize that volcanic eruptions, producing large amounts of sulfuric acid, can influence soil acidity and hence element mobilization.
Das serotonerge System besitzt sowohl bei Invertebraten als auch bei Vertebraten eine große Bedeutung für die Kontrolle und Modulation vieler physiologischer Prozesse und Verhaltensleistungen. Bei der Honigbiene Apis mellifera spielt Serotonin (5-Hydroxytryptamin, 5-HT) eine wichtige Rolle bei der Arbeitsteilung und dem Lernen. Die 5-HT-Rezeptoren, die überwiegend zur Familie der G-Protein gekoppelten Rezeptoren (GPCRs) gehören, besitzen eine Schlüsselstellung für das Verständnis der molekularen Mechanismen der serotonergen Signalweiterleitung. Ziel dieser Arbeit war es, 5-HT-Rezeptoren der Honigbiene zu charakterisieren. Dazu zählt die Identifizierung der molekularen Struktur, die Ermittlung der intrazellulären Signalwege, die Erstellung von pharmakologischen Profilen, die Ermittlung der Expressionsmuster und die Ermittlung der physiologischen Funktionen der Rezeptoren. Mit Hilfe der Informationen aus dem Honey Bee Genome Project, konnten drei RezeptorcDNAs kloniert werden. Vergleiche der abgeleiteten Aminosäuresequenzen mit den Aminosäuresequenzen bereits charakterisierter Rezeptoren legten nahe, dass es sich dabei um einen 5-HT1- (Am5-HT1) und zwei 5-HT2-Rezeptoren (Am5-HT2α und Am5-HT2β) handelt. Die strukturelle Analyse der abgeleiteten Aminosäuresequenz dieser Rezeptoren postuliert das Vorhandensein der charakteristischen heptahelikalen Architektur von GPCRs und zeigt starkkonservierte Motive, die bedeutend für die Ligandenbindung, die Rezeptoraktivierung und die Kopplung an G-Proteine sind. Für die beiden 5 HT2-Rezeptoren konnte zudem alternatives Spleißen nachgewiesen werden. Mit den cDNAs des Am5-HT1- und des Am5-HT2α-Rezeptors wurden HEK293-Zellen stabil transfiziert und anschließend die Rezeptoren funktionell und pharmakologisch analysiert. Am5-HT1 hemmt bei Aktivierung abhängig von der 5-HT-Konzentration die cAMPProduktion.Die Substanzen 5-Methoxytryptamin (5-MT) und 5-Carboxamidotryptamin konnten als Agonisten identifiziert werden. Methiothepin dagegen blockiert die 5-HTWirkung vollständig. Prazosin und WAY100635 stellen partielle Antagonisten des Am5-HT1-Rezeptors dar. Der Am5-HT2_-Rezeptor stimuliert bei Aktivierung die Synthese des sekundären Botenstoffs Inositoltrisphosphat, was wiederum zu einer messbaren Erhöhung der intrazellulären Ca2+-Konzentration führt. 5-MT und 8-OH-DPAT zeigen eine deutliche agonistische Wirkung auf Am5-HT2α. Dagegen besitzen Clozapin, Methiothepin, Mianserin und Cyproheptadin die Fähigkeit, die 5-HT-Wirkung um 51-64 % zu vermindern. Die bereits erwähnte alternative Spleißvariante von Am5-HT2α wurde ebenfalls in HEK293-Zellen exprimiert und analysiert, scheint jedoch eigenständig nicht funktionell zu sein. Gegen die dritte cytoplasmatische Schleife (CPL3) wurde ein polyklonales Antiserum generiert. Dieses erkennt in Western-Blot-Analysen ein Protein mit einer Masse von ca. 50 kDa. Durch immunhistochemische Analysen am Bienengehirn wurde die Verteilung des Rezeptors genauer untersucht. Dabei zeigten die optischen Neuropile, besonders die Lamina und die Ocellarnerven, stets eine starke Markierung. Außerdem wird der Rezeptor in den α- und β-Loben sowie der Lippe, dem Basalring und dem Pedunculus der Pilzkörper exprimiert. Doppelmarkierungen zeigen stets eine enge Nachbarschaft von serotonergen Fasern und dem Am5-HT1-Rezeptor. Weiterhin konnte gezeigt werden, dass der Am5-HT1-Rezeptor sehr wahrscheinlich an der Regulation des phototaktischen Verhalten der Honigbiene beteiligt ist. Verfütterung von 5-HT hat eine deutlich negative Wirkung auf das phototaktischen Verhalten. Diese kann durch den Am5-HT1-Rezeptor-Agonisten 5-CT imitiert werden. Schließlich konnte gezeigt werden, dass der Am5-HT1-Antagonist Prazosin die 5-HT-Wirkung deutlich vermindern kann.
After the epoch of reionisation the intergalactic medium (IGM) is kept at a high photoionisation level by the cosmic UV background radiation field. Primarily composed of the integrated contribution of quasars and young star forming galaxies, its intensity is subject to spatial and temporal fluctuations. In particular in the vicinity of luminous quasars, the UV radiation intensity grows by several orders of magnitude. Due to an enhanced UV radiation up to a few Mpc from the quasar, the ionised hydrogen fraction significantly increases and becomes visible as a reduced level of absorption in the HI Lyman alpha (Ly-alpha) forest. This phenomenon is known as the proximity effect and it is the main focus of this thesis. Modelling the influence on the IGM of the quasar radiation, one is able to determine the UV background intensity at a specific frequency (J_nu_0), or equivalently, its photoionisation rate (Gamma_b). This is of crucial importance for both theoretical and observational cosmology. Thus far, the proximity effect has been investigated primarily by combining the signal of large samples of quasars, as it has been regarded as a statistical phenomenon. Only a handful of studies tried to measure its signature on individual lines of sight, albeit focusing on one sight line only. Our aim is to perform a systematic investigation of large samples of quasars searching for the signature of the proximity effect, with a particular emphasis on its detection on individual lines of sight. We begin this survey with a sample of 40 high resolution (R~45000), high signal to noise ratio (S/N~70) quasar spectra at redshift 2.1<z<4.7, publicly available in the European Southern Observatory (ESO) archive. The extraordinary quality of this data set enables us to detect the proximity effect signature not only in the combined quasar sample, but also along each individual sight line. This allows us to determine not only the UV background intensity at the mean redshift of this sample, but also to estimate its intensity in small (Delta z~0.2) redshift intervals in the range 2<z<4. Our estimates (J_nu_0~ 3x10^{-22} erg s^{-1} cm^{-2} Hz^{-1} sr^{-1}) are for the first time in very good agreement with different constraints of its evolution obtained from theoretical predictions and numerical simulations. We continue this systematic analysis of the proximity effect with the largest search to date invoking the Sloan Digital Sky Survey (SDSS) data set. The sample consists of 1733 quasars at redshifts z>2.3. In spite of the low resolution and limited S/N we detect the proximity effect on about 98\% of the quasars at a high significance level. Thereby we are able to determine the evolution of the UV background photoionisation rate within the redshift range 2<z<5 finding Gamma_b~ 1.6x10^{-12} s^{-1}. With these new measurements we explore literature estimates of the quasar luminosity function and predict the stellar luminosity density up to redshift of about z~5. Our results are globally in good agreement with recent determinations inferred from deep surveys of high redshift galaxies. We then compare our measurements on the UV background photoionisation rate inferred from the two samples at high and low resolution. While these data sets show extreme differences, our determinations are in considerable agreement at z<3.3, even though they show less agreement at higher redshifts. We suspect that this may be caused by either the small number of high resolution quasar spectra at the highest redshifts considered or by some systematic effect due to the limited data quality of SDSS. Complementary to the observational investigation of the proximity effect on high redshift quasars, we exploit some theoretical aspects linked to and based on the results on this phenomenon. We employ complex numerical simulations of structure formation to achieve a better representation of the Ly-alpha forest. Modelling the signature of the proximity effect on randomly selected sight lines, we prove the advantages of dealing with individual lines of sight instead of combining their signal to investigate this phenomenon. Furthermore, we develop and test novel techniques aimed at a more precise determination of the proximity effect signal. With this investigation we demonstrate that the technique developed and employed in this thesis is the most accurate adopted thus far. Tighter determinations of the UV background are certainly based on suitable methods to detect its signature, but also on a deeper understanding of the environments in which quasars form and evolve. We initiate an investigation of complex numerical simulations including the radiative transport of energy to model in a more detailed way the proximity effect. Such a simulation may lead to the characterisation of the quasar environment based on the comparison between the observed and simulated statistical properties of the proximity effect signature.
The present thesis aims to introduce process-based model for species range dynamics that can be fitted to abundance data. For this purpose, the well-studied Proteaceae species of the South African Cape Floristic Region (CFR) offer a great data set to fit process-based models. These species are subject to wildflower harvesting and environmental threats like habitat loss and climate change. The general introduction of this thesis presents shortly the available models for species distribution modelling. Subsequently, it presents the feasibility of process-based modelling. Finally, it introduces the study system as well as the objectives and layout. In Chapter 1, I present the process-based model for range dynamics and a statistical framework to fit it to abundance distribution data. The model has a spatially-explicit demographic submodel (describing dispersal, reproduction, mortality and local extinction) and an observation submodel (describing imperfect detection of individuals). The demographic submodel links species-specific habitat models describing the suitable habitat and process-based demographic models that consider local dynamics and anemochoric seed dispersal between populations. After testing the fitting framework with simulated data, I applied it to eight Proteaceae species with different demographic properties. Moreover, I assess the role of two other demographic mechanisms: positive (Allee effects) and negative density-dependence. Results indicate that Allee effects and overcompensatory local dynamics (including chaotic behaviour) seem to be important for several species. Most parameter estimates quantitatively agreed with independent data. Hence, the presented approach seemed to suit the demand of investigating non-equilibrium scenarios involving wildflower harvesting (Chapter 2) and environmental change (Chapter 3). The Chapter 2 addresses the impacts of wildflower harvesting. The chapter includes a sensitivity analysis over multiple spatial scales and demographic properties (dispersal ability, strength of Allee effects, maximum reproductive rate, adult mortality, local extinction probability and carrying capacity). Subsequently, harvesting effects are investigated on real case study species. Plant response to harvesting showed abrupt threshold behavior. Species with short-distance seed dispersal, strong Allee effects, low maximum reproductive rate, high mortality and high local extinction are most affected by harvesting. Larger spatial scales benefit species response, but the thresholds become sharper. The three case study species supported very low to moderate harvesting rates. Summarizing, demographic knowledge about the study system and careful identification of the spatial scale of interest should guide harvesting assessments and conservation of exploited species. The sensitivity analysis’ results can be used to qualitatively assess harvesting impacts for poorly studied species. I investigated in Chapter 3 the consequences of past habitat loss, future climate change and their interaction on plant response. I use the species-specific estimates of the best model describing local dynamics obtained in Chapter 1. Both habitat loss and climate change had strong negative impacts on species dynamics. Climate change affected mainly range size and range filling due to habitat reductions and shifts combined with low colonization. Habitat loss affected mostly local abundances. The scenario with both habitat loss and climate change was the worst for most species. However, this impact was better than expected by simple summing of separate effects of habitat loss and climate change. This is explained by shifting ranges to areas less affected by humans. Range size response was well predicted by the strength of environmental change, whereas range filling and local abundance responses were better explained by demographic properties. Hence, risk assessments under global change should consider demographic properties. Most surviving populations were restricted to refugia, serving as key conservation focus.The findings obtained for the study system as well as the advantages, limitations and potentials of the model presented here are further discussed in the General Discussion. In summary, the results indicate that 1) process-based demographic models for range dynamics can be fitted to data; 2) demographic processes improve species distribution models; 3) different species are subject to different processes and respond differently to environmental change and exploitation; 4) density regulation type and Allee effects should be considered when investigating range dynamics of species; 5) the consequences of wildflower harvesting, habitat loss and climate change could be disastrous for some species, but impacts vary depending on demographic properties; 6) wildflower harvesting impacts varies over spatial scale; 7) The effects of habitat loss and climate change are not always additive.
With the rise of electronic integration between organizations, the need for a precise specification of interaction behavior increases. Information systems, replacing interaction previously carried out by humans via phone, faxes and emails, require a precise specification for handling all possible situations. Such interaction behavior is described in process choreographies. Choreographies enumerate the roles involved, the allowed interactions, the message contents and the behavioral dependencies between interactions. Choreographies serve as interaction contract and are the starting point for adapting existing business processes and systems or for implementing new software components. As a thorough analysis and comparison of choreography modeling languages is missing in the literature, this thesis introduces a requirements framework for choreography languages and uses it for comparing current choreography languages. Language proposals for overcoming the limitations are given for choreography modeling on the conceptual and on the technical level. Using an interconnection modeling style, behavioral dependencies are defined on a per-role basis and different roles are interconnected using message flow. This thesis reveals a number of modeling "anti-patterns" for interconnection modeling, motivating further investigations on choreography languages following the interaction modeling style. Here, interactions are seen as atomic building blocks and the behavioral dependencies between them are defined globally. Two novel language proposals are put forward for this modeling style which have already influenced industrial standardization initiatives. While avoiding many of the pitfalls of interconnection modeling, new anomalies can arise in interaction models. A choreography might not be realizable, i.e. there does not exist a set of interacting roles that collectively realize the specified behavior. This thesis investigates different dimensions of realizability.
This work presents the synthesis and the self-assembly of symmetrical amphiphilic ABA and BAB triblock copolymers in dilute, semi-concentrated and highly concentrated aqueous solution. A series of new bifunctional bistrithiocarbonates as RAFT agents was used to synthesise these triblock copolymers, which are characterised by a long hydrophilic middle block and relatively small, but strongly hydrophobic end blocks. As hydrophilic A blocks, poly(N-isopropylacrylamide) (PNIPAM) and poly(methoxy diethylene glycol acrylate) (PMDEGA) were employed, while as hydrophobic B blocks, poly(4-tert-butyl styrene), polystyrene, poly(3,5-dibromo benzyl acrylate), poly(2-ethylhexyl acrylate), and poly(octadecyl acrylate) were explored as building blocks with different hydrophobicities and glass transition temperatures. The five bifunctional trithiocarbonates synthesised belong to two classes: the first are RAFT agents, which position the active group of the growing polymer chain at the outer ends of the polymer (Z-C(=S)-S-R-S-C(=S)-Z, type I). The second class places the active groups in the middle of the growing polymer chain (R-S-C(=S)-Z-C(=S)-S-R, type II). These RAFT agents enable the straightforward synthesis of amphiphilic triblock copolymers in only two steps, allowing to vary the nature of the hydrophobic blocks as well as the length of the hydrophobic and hydrophilic blocks broadly with good molar mass control and narrow polydispersities. Specific side reactions were observed among some RAFT agents including the elimination of ethylenetrithiocarbonate in the early stage of the polymerisation of styrene mediated by certain agents of the type II, while the use of the RAFT agents of type I resulted in retardation of the chain extension of PNIPAM with styrene. These results underline the need of a careful choice of RAFT agents for a given task. The various copolymers self-assemble in dilute and semi-concentrated aqueous solution into small flower-like micelles. No indication for the formation of micellar clusters was found, while only at high concentration, physical hydrogels are formed. The reversible thermoresponsive behaviour of the ABA and BAB type copolymer solutions in water with A made of PNIPAM was examined by turbidimetry and dynamic light scattering (DLS). The cloud point of the copolymers was nearly identical to the cloud point of the homopolymer and varied between 28-32 °C with concentrations from 0.01 to 50 wt%. This is attributed to the formation of micelles where the hydrophobic blocks are shielded from a direct contact with water, so that the hydrophobic interactions of the copolymers are nearly the same as for pure PNIPAM. Dynamic light scattering measurements showed the presence of small micelles at ambient temperature. The aggregate size dramatically increased above the cloud point, indicating a change of aggregate morphology into clusters due to the thermosensitivity of the PNIPAM block. The rheological behaviour of the amphiphilic BAB triblock copolymers demonstrated the formation of hydrogels at high concentrations, typically above 30-35 wt%. The minimum concentration to induce hydrogels decreased with the increasing glass transition temperatures and increasing length of the end blocks. The weak tendency to form hydrogels was attributed to a small share of bridged micelles only, due to the strong segregation regime occurring. In order to learn about the role of the nature of the thermoresponsive block for the aggregation, a new BAB triblock copolymer consisting of short polystyrene end blocks and PMDEGA as stimuli-responsive middle block was prepared and investigated. Contrary to PNIPAM, dilute aqueous solutions of PMDEGA and of its block copolymers showed reversible phase transition temperatures characterised by a strong dependence on the polymer composition. Moreover, the PMDEGA block copolymer allowed the formation of physical hydrogels at lower concentration, i.e. from 20 wt%. This result suggests that PMDEGA has a higher degree of water-swellability than PNIPAM.
Analytical ultracentrifugation (AUC) has made an important contribution to polymer and particle characterization since its invention by Svedberg (Svedberg and Nichols 1923; Svedberg and Pederson 1940) in 1923. In 1926, Svedberg won the Nobel price for his scientific work on disperse systems including work with AUC. The first important discovery performed with AUC was to show the existence of macromolecules. Since that time AUC has become an important tool to study polymers in biophysics and biochemistry. AUC is an absolute technique that does not need any standard. Molar masses between 200 and 1014 g/mol and particle size between 1 and 5000 nm can be detected by AUC. Sample can be fractionated into its components due to its molar mass, particle size, structure or density without any stationary phase requirement as it is the case in chromatographic techniques. This very property of AUC earns it an important status in the analysis of polymers and particles. The distribution of molar mass, particle sizes and densities can be measured with the fractionation. Different types of experiments can give complementary physicochemical parameters. For example, sedimentation equilibrium experiments can lead to the study of pure thermodynamics. For complex mixtures, AUC is the main method that can analyze the system. Interactions between molecules can be studied at different concentrations without destroying the chemical equilibrium (Kim et al. 1977). Biologically relevant weak interactions can also be monitored (K ≈ 10-100 M-1). An analytical ultracentrifuge experiment can yield the following information: • Molecular weight of the sample • Number of the components in the sample if the sample is not a single component • Homogeneity of the sample • Molecular weight distribution if the sample is not a single component • Size and shape of macromolecules & particles • Aggregation & interaction of macromolecules • Conformational changes of macromolecules • Sedimentation coefficient and density distribution Such an extremely wide application area of AUC allows the investigation of all samples consisting of a solvent and a dispersed or dissolved substance including gels, micro gels, dispersions, emulsions and solutions. Another fact is that solvent or pH limitation does not exist for this method. A lot of new application areas are still flourishing, although the technique is 80 years old. In 1970s, 1500 AUC were operational throughout the world. At those times, due to the limitation in detection technologies, experimental results were obtained with photographic records. As time passed, faster techniques such as size exclusion chromatography (SEC), light scattering (LS) or SDS-gel electrophoresis occupied the same research fields with AUC. Due to these relatively new techniques, AUC began to loose its importance. In the 1980s, only a few AUC were in use throughout the world. In the beginning of the 1990s a modern AUC -the Optima XL-A - was released by Beckman Instruments (Giebeler 1992). The Optima XL-A was equipped with a modern computerized scanning absorption detector. The addition of Rayleigh Interference Optics is introduced which is called XL-I AUC. Furthermore, major development in computers made the analysis easier with the help of new analysis software. Today, about 400 XL-I AUC exist worldwide. It is usually applied in the industry of pharmacy, biopharmacy and polymer companies as well as in academic research fields such as biochemistry, biophysics, molecular biology and material science. About 350 core scientific publications which use analytical ultracentrifugation are published every year (source: SciFinder 2008 ) with an increasing number of references (436 reference in 2008). A tremendous progress has been made in method and analysis software after digitalization of experimental data with the release of XL-I. In comparison to the previous decade, data analysis became more efficient and reliable. Today, AUC labs can routinely use sophisticated data analysis methods for determination of sedimentation coefficient distributions (Demeler and van Holde 2004; Schuck 2000; Stafford 1992), molar mass distributions (Brookes and Demeler 2008; Brookes et al. 2006; Brown and Schuck 2006), interaction constants (Cao and Demeler 2008; Schuck 1998; Stafford and Sherwood 2004), particle size distributions with Angstrom resolution (Cölfen and Pauck 1997) and the simulations determination of size and shape distributions from sedimentation velocity experiments (Brookes and Demeler 2005; Brookes et al. 2006). These methods are also available in powerful software packages that combines various methods, such as, Ultrascan (Demeler 2005), Sedift/Sedphat (Schuck 1998; Vistica et al. 2004) and Sedanal (Stafford and Sherwood 2004). All these powerful packages are free of charge. Furthermore, Ultrascans source code is licensed under the GNU Public License (http://www.gnu.org/copyleft/gpl.html). Thus, Ultrascan can be further improved by any research group. Workshops are organized to support these software packages. Despite of the tremendous developments in data analysis, hardware for the system has not developed much. Although there are various user developed detectors in research laboratories, they are not commercially available. Since 1992, only one new optical system called “the fluorescence optics” (Schmidt and Reisner, 1992, MacGregor et al. 2004, MacGregor, 2006, Laue and Kroe, in press) has been commercialized. However, except that, there has been no commercially available improvement in the optical system. The interesting fact about the current hardware of the XL-I is that it is 20 years old, although there has been an enormous development in microelectronics, software and in optical systems in the last 20 years, which could be utilized for improved detectors. As examples of user developed detector, Bhattacharyya (Bhattacharyya 2006) described a Multiwavelength-Analytical Ultracentrifuge (MWL-AUC), a Raman detector and a small angle laser light scattering detector in his PhD thesis. MWL-AUC became operational, but a very high noise level prevented to work with real samples. Tests with the Raman detector were not successful due to the low light intensity and thus high integration time is required. The small angle laser light scattering detector could only detect latex particles but failed to detect smaller particles and molecules due to low sensitivity of the detector (a photodiode was used as detector). The primary motivation of this work is to construct a detector which can measure new physico-chemical properties with AUC with a nicely fractionated sample in the cell. The final goal is to obtain a multiwavelength detector for the AUC that measures complementary quantities. Instrument development is an option for a scientist only when there is a huge potential benefit but there is no available commercial enterprise developing appropriate equipment, or if there is not enough financial support to buy it. The first case was our motivation for developing detectors for AUC. Our aim is to use today’s technological advances in microelectronics, programming, mechanics in order to develop new detectors for AUC and improve the existing MWL detector to routine operation mode. The project has multiple aspects which can be listed as mechanical, electronical, optical, software, hardware, chemical, industrial and biological. Hence, by its nature it is a multidisciplinary project. Again by its nature it contains the structural problem of its kind; the problem of determining the exact discipline to follow at each new step. It comprises the risk of becoming lost in some direction. Having that fact in mind, we have chosen the simplest possible solution to any optical, mechanical, electronic, software or hardware problem we have encountered and we have always tried to see the overall picture. In this research, we have designed CCD-C-AUC (CCD Camera UV/Vis absorption detector for AUC) and SLS-AUC (Static Light Scattering detector for AUC) and tested them. One of the SLS-AUC designs produced successful test results, but the design could not be brought to the operational stage. However, the operational state Multiwavelength Analytical Ultracentrifuge (MWL-AUC) AUC has been developed which is an important detector in the fields of chemistry, biology and industry. In this thesis, the operational state Multiwavelength Analytical Ultracentrifuge (MWL-AUC) AUC is to be introduced. Consequently, three different applications of MWL-AUC to the aforementioned disciplines shall be presented. First of all, application of MWL-AUC to a biological system which is a mixture of proteins lgG, aldolase and BSA is presented. An application of MWL-AUC to a mass-produced industrial sample (β-carotene gelatin composite particles) which is manufactured by BASF AG, is presented. Finally, it is shown how MWL-AUC will impact on nano-particle science by investigating the quantum size effect of CdTe and its growth mechanism. In this thesis, mainly the relation between new technological developments and detector development for AUC is investigated. Pioneering results are obtained that indicate the possible direction to be followed for the future of AUC. As an example, each MWL-AUC data contains thousands of wavelengths. MWL-AUC data also contains spectral information at each radial point. Data can be separated to its single wavelength files and can be analyzed classically with existing software packages. All the existing software packages including Ultrascan, Sedfit, Sedanal can analyze only single wavelength data, so new extraordinary software developments are needed. As a first attempt, Emre Brookes and Borries Demeler have developed mutliwavelength module in order to analyze the MWL-AUC data. This module analyzes each wavelength separately and independently. We appreciate Emre Brookes and Borries Demeler for their important contribution to the development of the software. Unfortunately, this module requires huge amount of computer power and does not take into account the spectral information during the analysis. New software algorithms are needed which take into account the spectral information and analyze all wavelengths accordingly. We would like also invite the programmers of Ultrascan, Sedfit, Sedanal and the other programs, to develop new algorithms in this direction.
Zum Erhalt vom Aussterben bedrohter Papageienvögel (Psittaciformes) ist die Nachzucht in Menschenobhut neben dem Erhalt freilebender Populationen von großer Bedeutung, die Reproduktion bestimmter Arten gelingt allerdings nur unzureichend. Als Hauptgrund dafür gilt die Zwangsverpaarung im Rahmen von Zuchtprogrammen (Beispiel: Europäisches Erhaltungszuchtprogramm, EEP), hier werden Brutpaare hauptsächlich nach genetischen Aspekten zusammengestellt. Der reproduktive Erfolg ist bei den meisten Papageienarten, die in dauerhaften Paarbindungen leben (perennial monogamy), eng der Paarbindung korreliert. Eine freie Partnerwahl ist demnach von großer Bedeutung für die Zucht in Menschenobhut, im Rahmen von Erhaltungszuchtprogrammen jedoch nur selten möglich. Das Ziel der Untersuchung war, eine wissenschaftlich begründete Methode zu entwickeln, durch die es möglich sein soll, das Fortpflanzungspotential von Brutpaaren der Gattung Ara anhand der Paarbindung zu bestimmen. Dafür wurde die Bedeutung der Qualität der Paarbindung der Brutpaare für den Lebens-Reproduktionserfolg (Lifetime-reproductive success, LRS) untersucht. Die Datenaufnahme erfolgte in dem Zuchtzentrum 'La Vera' der Loro Parque Fundación auf Teneriffa/ Spanien. Hier wurden in den Jahren 2006 und 2007 21 Brutpaare der Gattung Ara untersucht. Die Paarbindung wurde zum Einen durch typisches Paarbindungsverhalten und zum Anderen durch die physiologische Abstimmung der einzelnen Brutpaare anhand der Ausschüttung des Steroidhormons Testosteron dargestellt. Das Paarbindungsverhalten setzte sich aus der ‚Abstimmung der Tagesaktivität’, dem ‚Kontaktverhalten’ und den ‚sozialen Interaktionen’ zusammen. Zur Abstimmung der Tagesaktivität zählten die Verhaltensweisen Ruhen, Sitzen, Nahrungsaufnahme, Gefiederpflege, Beschäftigung und Lokomotion. Unter Kontaktverhalten wurden das Überschreiten der Individualdistanz bei bestimmten Verhaltensweisen und die Rollenverteilung der Geschlechter untersucht. Unter ‚sozialen Interaktionen’ wurden die Dauer und der Häufigkeit der sozialen Gefiederpflege und der Sozialen Index zusammengefasst. Bei der sozialen Gefiederpflege wurde die Dauer und die Häufigkeit der Phasen erhoben, sowie der jeweilige Initiator dieser Interaktion. Zusätzlich wurde untersucht, welches Geschlecht, wie häufig und mit welcher Dauer aktiv an der sozialen Gefiederpflege beteiligt war. Aus den Beobachtungen wurde der soziale Index berechnet, der angibt, wie das Verhältnis sozio-positiver zu agonistischen Interaktionen für jedes Individuum, sowie das Paar an sich ist. Zur Messung der Testosteron-Ausschüttung der Partnertiere wurden von September bis November 2007 über einen Zeitraum von 9 Wochen jede Woche einmal für jedes Individuum Kotproben gesammelt. Mit der Analyse der Proben wurde das Veterinär-Physiologisch-Chemische-Institut der Universität Leipzig unter der Leitung von Prof. Dr. Almuth Einspanier beauftragt. Zur Ermittlung des Hormongehalts in den gewonnenen Kotproben diente ein kompetitiver Doppelantikörper-Enzymimmunoassay (EIA). Das Fortpflanzungspotential wurde über die Anzahl der Eier, Gelege und Jungtiere, sowie über die Gelegegröße dargestellt. Diese Daten geben, bezogen auf die Dauer der Paarbindung, Auskunft über die Produktivität eines Brutpaares, anhand dessen zusätzlich ein Produktivitäts-Koeffizient berechnet wurde. Des weiteren sollte die Anzahl der von einem Brutpaar selbständig großgezogenen Jungtiere Auskunft über die Fähigkeit zur kooperativen Jungenaufzucht geben. Zur Untersuchung der Bedeutung der Paarbindungsqualität wurden Diskriminanzfunktionsanalysen und Regressionsanalysen durchgeführt, wozu die untersuchten Brutpaare anhand ihres Fortpflanzungspotentials in verschiedene Gruppen eingeteilt wurden. Anhand der Ergebnisse der Studie konnte gezeigt werden, dass das Fortpflanzungspotential von Brutpaaren von verschiedenen Kriterien, die die Paarbindungsqualität charakterisieren, abhängt. Dabei ist zwischen der Produktivität und der Fähigkeit zur kooperativen Jungenaufzucht zu unterscheiden. Die Produktivität eines Paares wurde hinsichtlich der abgestimmten Tagesaktivität positiv vom synchronen Ruhen mit dem Partner beeinflusst, sowie von der Häufigkeit und Dauer der vom Weibchen ausgehenden sozialen Gefiederpflege. Brutpaare mit hoher Produktivität waren zudem über eine hohe ‚intra-Paar Fluktuation’ des Steroidhormons Testosteron gekennzeichnet. Die Brutpaare, die in der Lage sind, ihre Jungtiere in Kooperation großzuziehen, zeigten ebenfalls einen hohen Anteil zeitlich mit dem Partner abgestimmter Ruhephasen, zudem häufiges Ruheverhalten in Körperkontakt zum Partner und ein hohes zeitliches Investment der Männchen bei der Initiierung und Durchführung sozialer Gefiederpflege. Darüber hinaus zeigten Männchen, die einen Beitrag zur kooperativen Jungenaufzucht leisten, eine wesentlich geringere durchschnittliche Testosteron-Konzentration – bezogen auf den Untersuchungszeitraum, als Männchen, die Brutpaaren angehören, die nicht zur selbständigen Jungenaufzucht fähig sind. Dieses Ergebnis spiegelt die Bedeutung von Testosteron bei der elterlichen Fürsorge wider und bietet einen Anhaltspunkt für weitere Untersuchungen. Die Untersuchung konnte zeigen, dass es möglich und sinnvoll ist, das individuelle Verhalten von Tieren in Menschenobhut für den Erhalt bedrohter Tierarten einzusetzen. Weitere, auf dieser Studie aufbauende Untersuchungen sollten zum Ziel haben, zuverlässig die Brutpaare erkennbar zu machen, die über ein gutes Fortpflanzungspotential verfügen. Auf diese Weise kann unzureichender Reproduktionserfolg bedrohter Papageienarten in Menschenobhut infolge von Zwangsverpaarung minimiert werden.
Die funktionelle Bedeutung des Coxsackie- und Adenovirus Rezeptors (CAR) im kolorektalen Karzinom
(2009)
Der Coxsackie- und Adenovirus Rezeptor (CAR) ist als Bestandteil von Tight Junctions (TJ) an interzellulären Adhäsionsprozessen beteiligt und scheint eine wichtige Rolle in der Karzinogenese zu spielen. Diese ist jedoch insbesondere bei Entstehung von Darmkrebs weitgehend unklar. Ziel der Arbeit war es daher, die funktionelle Bedeutung, mögliche Interaktionspartner sowie die Expressionsregulation von CAR im kolorektalen Karzinom zu analysieren. In den Zelllinien CaCo2, Colo205, DLD1, HCT116, HT29, SW480 und T84 konnte die Expression von CAR (mRNA und Protein) nachgewiesen werden. Nach stabiler CAR-Überexpression durch Transfektion von CARcDNA in DLD1, HCT116 und SW480 wurde das Zellwachstum gehemmt und eine Abnahme von Migration und Invasion induziert. Eine stabile CAR-Inhibition nach Transfektion von CARsiRNA führte in diesen Zelllinien zum Anstieg der Proliferation sowie zu verstärkter Migrations- und Invasionsaktivität, die in DLD1 mit morphologischen Änderungen einhergingen. Eine Genexpressionsanalyse der Zelllinie DLD1 mit CAR-Inhibition identifizierte α-Catenin als das am stärksten regulierte Gen. Obwohl keine direkte Interaktion beider Proteine detektiert werden konnte, führte eine stabile Re-Expression von α-Catenin in DLD1 mit stabiler CAR-Inhibition zu einer deutlichen Reduktion von Proliferation, Migration und Invasion sowie zu einem Rückgang der zellmorphologischen Änderungen. Um den Einfluss von Differenzierung auf die Regulation der CAR-Expression zu untersuchen, erfolgte eine Behandlung aller Zelllinien mit Natriumbutyrat. Dies führte in fünf der sieben Zelllinien zu einer Aktivierung des CAR-Promotors sowie zu einer gesteigerten Expression und Immunoreaktivität von CAR an der Zelloberfläche. Die Zelllinie CaCo2 zeigte nach spontaner Differenzierung durch 21-tägiges Wachstum post Konfluenz ebenfalls eine verstärkte CAR-mRNA-Expression sowie eine erhöhte CAR-Präsenz an der Zelloberfläche. Die gewonnenen Daten konnten die funktionelle Bedeutung von CAR für die Kolonkarzinogenese sowie den Einfluss von α-Catenin auf diese Funktion deutlich machen. Es wurde gezeigt, dass die Expressionsregulation sowie die subzelluläre Verteilung von CAR durch den zellulären Differenzierungsstatus beeinflusst werden kann.