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Allergic disease are inflammatory disorders in which aberrant immune regulation occurs, and susceptible individuals mount allergen specific T helper 2 (Th2) responses, which drives disease pathology. Recent studies indicate that Th2 responses that are characteristic of allergic manifestations can be regulated by both naturally occurring CD4+CD25+ regulatory (Treg) cells and antigen-driven IL-10-secreting CD4+ regulatory T cells. Evidence is also emerging that successful Allergen specific immunotherapy (SIT) might work through the induction of IL-10-secreting regulatory T cells. In the first part of this work, I demonstrated the efficiency of allergen specific immunotherapy in the mouse model for allergic airway inflammation. Here I could show that intranasal administration of SIT abrogates allergic symptoms more efficiently, than the subcutaneous treatment. Furthermore, an IL-4/IL-13 (QY) inhibitor was used as an adjuvant for SIT, which has been demonstrated to have an anti-allergic potential, when administered prophylactically during allergic sensitization. However, the combination therapy with SIT and the inhibitory molecule QY did not show any significant enhancement in regards to all measured allergic parameters, when compared to monotherapy with SIT. These results provide the evidence, that shift from Th2 to Th1 cytokine profile might not be a key event in successful SIT. Subsequently, the investigation of immune mechanisms under successful SIT demonstrate that the increase of IL-10 secreting CD4+ T regulatory cells is associated with the suppression of airway inflammation in our mouse system, suggesting that these T cell subsets might be involved in the regulatory mechanisms of allergic disorders. In agreement with these findings is the second part of this work, where superagonistic a-CD28 mAb´s were used for the expansion of T regulatory cell subsets in our murine model for allergic airway inflammation. Here I could show, that the application of a-CD28 mAb during allergic sensitization, resulted in the establishment of a Th2 state, rather than a stimulation of a Treg cell population, supporting the Th2 promoting role of a-CD28 mAb together with TCR engagement. However, interesting findings were obtained by application of the superagonistic a-CD28 mAb in the challenge phase in established allergy. Conversely to the previous experiment, therapeutic administration of a-CD28 mAb lead to the generation of IL-10 secreting CD4+CD25+ T cell population in line with the induction of anti-allergic effects. Taking together the results of this study argue for the anti-inflammatory properties of T regulatory cells in allergic disease and highlights importance of these T cell subsets in the suppression of Th2 cell-driven response to allergen. Moreover, these observations suggest that the induction of IL-10 in vivo by T regulatory cells may represent a novel treatment strategy for allergic disorders.
Viren durchliefen eine gemeinsame Evolution mit ihren Wirtsorganismen, die zu einer spezifischen Anpassung der Viren an ihren jeweiligen Wirt führte. Als Folge dessen verfügen viele Viren über ein eng begrenztes Wirtsspektrum. Gelegentlich machen Viren Veränderungen durch, die es ihnen erlauben, einen neuen Wirt zu infizieren und in ihm zu replizieren, wie dies in jüngster Vergangenheit beim humanen Immundefizienz-Virus oder beim Grippevirus geschehen ist. Spezies-übergreifende Infektionen sind für die meisten neuen und wiederauftauchenden Viruserkrankungen verantwortlich. Allerdings ist bisher wenig über die Mechanismen bekannt, die Viren auf einen bestimmten Wirt beschränken, und welche Faktoren Viren zur Überwindung der Spezies-Barriere und zur Vermehrung in einer neuen Wirtsspezies benötigen. Cytomegaloviren sind Prototypen der beta-Herpesvirus Unterfamilie und verfügen über eine ausgeprägte Spezies-Spezifität. Sie vermehren sich nur in Zellen der eigenen oder einer eng verwandten Wirtsspezies. Der molekulare Mechanismus, der dieser Spezies-Spezifität zugrunde liegt, ist noch weitgehend unbekannt und stellt deshalb das Thema dieser Arbeit dar. Initiale Beobachtungen zeigten, dass sich das Maus-Cytomegalovirus (MCMV) ausschließlich in menschlichen 293 und 911 Zellen, aber keiner anderen getesteten menschlichen Zelle vermehren ließ. Diese beiden Zelllinien sind mit Adenovirus E1-Genen transformiert, die den Transkriptions-Transaktivator E1A sowie zwei Apoptose-Inhibitoren (E1B-55k und E1B-19k) kodieren. Daher lag die Hypothese nahe, dass diese Funktionen benötigt werden, um eine MCMV-Replikation in menschlichen Zellen zu ermöglichen. Außerdem konnte gezeigt werden, dass normale menschliche Zellen nach Infektion rapide absterben, und zwar durch eine Caspase-9-vermittelte Apoptose. Die Induktion der Apoptose durch MCMV lässt sich durch Caspase-Inhibitoren unterdrücken, wodurch die virale Replikation wiederhergestellt wird. Dies deutet auf eine Schlüsselfunktion der Caspasen für diesen Prozess hin. Durch Überexpression eines mitochondrialen Apoptose-Inhibitors, d.h. eines Bcl-2-ähnlichen Proteins, in menschlichen Zellen ließ sich die Virus-induzierte Apoptose verhindern. Diese Zellen erlaubten ebenfalls eine effiziente MCMV-Replikation. Die Bedeutung Bcl-2-ähnlicher Proteine für die Spezies-übergreifende Cytomegalovirus-Infektion wurde sowohl durch die Integration korrespondierender Gene, alsauch durch die Integration anderer Inhibitioren der Apoptose oder von Kontroll-Genen in das MCMV Genom bestätigt. Nur rekombinante Viren, die ein Bcl-2-ähnliches Protein kodieren, konnten in menschlichen Zellen vermehrt werden. Ein einziges Gen des humanen Cytomegalovirus, das einen mitochondrialen Apoptose-Inhibitor kodiert, reichte aus, um eine MCMV-Replikation in menschlichen Zellen zu ermöglichen. Zusätzlich konnte gezeigt werden, dass dieselben Prinzipien für eine Replikation des Ratten-Cytomegalovirus in menschlichen Zellen gelten. Zusammenfassend kann festgestellt werden, dass die Induktion der Apoptose eine Spezies-übergreifende Infektion bei den Nagetier-Cytomegaloviren einschränkt.
The astronomical exploration at energies between 30\,GeV and $\lesssim$\,350\,GeV was the main motivation for building the \MAGIC-telescope. With its 17\,m \diameter\ mirror it is the worldwide largest imaging air-Cherenkov telescope. It is located at the Roque de los Muchachos at the Canary island of San Miguel de La Palma at 28.8$^\circ$\,N, 17.8$^\circ$\,W, 2200\,m a.s.l. The telescope detects Cherenkov light produced by relativistic electrons and positrons in air showers initiated by cosmic gamma-rays. The imaging technique is used to powerfully reject the background due to hadronically induced air showers from cosmic rays. Their inverse power-law energy-distribution leads to an increase of the event rate with decreasing energy threshold. For \MAGIC this implies a trigger rate in the order of 250\,Hz, and a correspondingly large data stream to be recorded and analyzed. A robust analysis software package, including the general framework \MARS, was developed and commissioned to allow automation, necessary for data taken under variable observing conditions. Since many of the astronomical sources of high-energy radiation, in particular the enigmatic gamma-ray bursts, are of a transient nature, the telescope was designed to allow repositioning in several tens of seconds, keeping a tracking accuracy of $\lesssim\,$0.01$^\circ$. Employing a starguider, a tracking accuracy of $\lesssim\,$1.3\,minutes of arc was obtained. The main class of sources at very high gamma-ray energies, known from previous imaging air-Cherenkov telescopes, are Active Galactic Nuclei with relativistic jets, the so-called high-peaked Blazars. Their spectrum is entirely dominated by non-thermal emission, spanning more than 15 orders of magnitude in energy, from radio to gamma-ray energies. Predictions based on radiation models invoking a synchrotron self-Compton or hadronic origin of the gamma-rays suggest, that a fairly large number of them should be detectable by \MAGIC. Promising candidates have been chosen from existing compilations, requiring high (synchrotron) X-ray flux, assumed to be related to a high (possibly inverse-Compton) flux at GeV energies, and a low distance, in oder to avoid strong attenuation due to pair-production in interactions with low-energy photons from the extragalactic background radiation along the line of sight. Based on this selection the first \AGN, emitting gamma-rays at 100\,GeV, 1ES\,1218+304 at a redshift of $z=0.182$, was discovered, one of the two farthest known \AGN emitting in the TeV energy region. In this context, the automated analysis chain was successfully demonstrated. The source was observed in January 2005 during six moonless nights for 8.2\,h. At the same time the collaborating \KVA-telescope, located near the \MAGIC site, observed in the optical band. The lightcurve calculated showed no day-to-day variability and is compatible with a constant flux of $F($\,$>$\,$100\,\mbox{GeV})=(8.7\pm1.4) \cdot 10^{-7}\,\mbox{m}^{-2}\,\mbox{s}^{-1}$ within the statistical errors. A differential spectrum between 87\,GeV and 630\,GeV was calculated and is compatible with a power law of $F_E(E) = (8.1\pm 2.1) \cdot 10^{-7}(E/\mbox{250\,GeV})^{-3.0\pm0.4}\,\mbox{TeV}^{-1}\,\mbox{m}^{-2}\,\mbox{s}^{-1}$ within the statistical errors. The spectrum emitted by the source was obtained by taking into account the attenuation due to pair-production with photons of the extragalactic background at low photon energies. A homogeneous, one-zone synchrotron self-Compton model has been fitted to the collected multi-wavelength data. Using the simultaneous optical data, a best fit model could be obtained from which some physical properties of the emitting plasma could be inferred. The result was compared with the so-called {\em Blazar sequence}.
Quantum chemical modeling of electron paramagnetic resonance (EPR) parameters, in combination with data from the modern high-field/high-frequency EPR (HF-EPR) techniques, constitutes an invaluable analytical tool for gaining insight into radical-protein interactions, which determine the specificity and directionality of the radical-mediated biochemical processes. This thesis reports a series of density functional (DFT) studies on EPR parameters of several biologically relevant radicals and a series of molecular devices inspired by radical-protein interaction in photosystem I (PS-I). We demonstrate our methodology’s accuracy and capacity to provide insight into the in vivo environment and reactivity of bioradicals. Our DFT approach for the calculation of electronic g-tensors has been applied to semiquinone radical anions in the different protein environments of photosynthetic reaction centers. Supermolecular models have been constructed, based on combined crystallographic and quantum chemical structure data, for the QA and QB active sites of bacterial reaction centers, for the A1 site of PS-I, as well as for ubisemiquinone in frozen 2-propanol. After scaling of the computed gx components by 0.92, both gx and gy components computed at gradient-corrected DFT level with accurate spin-orbit operators agree with HF-EPR reference data essentially to within experimental accuracy in all four systems studied. The influence of the various semiquinone-protein non-covalent interactions has been studied by successive removal of individual residues from the models. The effects of hydrogen bonding to the two carbonyl oxygen atoms of the semiquinones was found to be nonadditive, due to compensating spin-polarization effects. The effects of tryptophan-semiquinone -stacking are different for QA and A1 sites. This may be traced back to a different alignment of the interacting fragments and to differential spin polarization. In the next part of this work our DFT methodology has been applied to the semiquinone in the environment of the “high-affinity” binding site of quinol oxidase (QH site). Recent multi-frequency EPR studies of the QH binding site of quinol oxidase have suggested a very asymmetric hydrogen-bonding environment for the semiquinone radical anion state. Single-sided hydrogen bonding to the O1 carbonyl position was one of the proposals, which contrasts with some previous experimental indications. The density functional calculations of the EPR parameters (g-tensors, 13C, 1H, and 17O hyperfine tensors) for a wide variety of supermolecular model complexes have been used to provide insight into the detailed relations between structure, environment and EPR parameters of ubisemiquinone radical anions. A single-sided binding model is not able to account for the experimentally observed low gx component of the g-tensor nor for the observed magnitude of the asymmetry of the 13C carbonyl hyperfine coupling (HFC) tensors. Based on the detailed comparison between computation and experiment, a model with two hydrogen bonds to O1 and one hydrogen bond to O4 was suggested for the QH site, but a model with one more hydrogen bond on each side could not be excluded. Additionally, several general conclusions on the interrelations between EPR parameters and hydrogen bond patterns of ubisemiquinones in proteins were provided. The computational studies related to the mechanism of electron transfer in PS-I gave an impetus to the theoretical design, based on quantum-chemical calculations, of relatively small rotational molecular motors made up from intramolecularly connected dyads consisting of a quinone unit and a pyrrole or indole moiety. It was shown computationally for several systems, depending on the length and attachment points of the interconnecting chains, that a reduction of the quinone to the semiquinone radical anion or quinolate dianion states leads to a reversible intramolecular reorientation from a -stacked to a T-stacked arrangement. In the rearranged structures, a hydrogen bond from the pyrrole or indole N-H function to the semiquinone or quinolate -system is created upon reduction. In some systems, hydrogen bonds to the semiquinone or quinolate oxygen atoms are partly feasible and will be preferred over T-stacking. It was shown that the intramolecular interactions modify the quinone redox potentials. The electronic g-tensors computed for the semiquinone states reflected characteristically the presence and nature of hydrogen bonds to the semiquinone and were suggested as suitable EPR spectroscopic probes for the preferred structures. Intramolecular proton transfer was observed to be possible in the dianionic state. In contrast to semiquinones, which represent paramagnetic states of enzyme cofactors, glycyl radicals are genuine protein radicals. As a step towards an in-depth understanding of the EPR parameters of glycyl radicals in proteins, the hyperfine- tensors and, particularly, the g-tensor of N-acetylglcyl in the environment of a single crystal of N-acetylglycine have been studied by systematic state-of-the-art quantum chemical calculations on various suitable model systems. The quantitative computation of the g-tensors for such glycyl-derived radicals is a veritable challenge, mainly due to the very small g-anisotropy combined with a non-symmetrical, delocalized spin-density distribution and several atoms with comparable spin-orbit contributions to the g-tensors. The choice of gauge origin of the magnetic vector potential, and of approximate spin-orbit operators, both turn out to be more critical than found in previous studies of g-tensors for organic radicals. Environmental effects, included by supermolecular hydrogen-bonded models, were found to be moderate, due to a partial compensation between the influences from intramolecular and intermolecular hydrogen bonds. The largest effects on the g-tensor are caused by the conformation of the radical. The DFT methods employed systematically overestimate both the gx and gy components of the g-tensor. This is important for investigations on the protein-glycyl radicals (see next paragraph). The 1H and 13C hyperfine couplings depend only slightly on the supermolecular model chosen and appear less sensitive probes of detailed structure and environment. The number of enzymes that require a glycyl-based radical for their function is growing. Here we provide systematic quantum-chemical studies of spin-density distributions, electronic g-tensors, and hyperfine couplings of various models of protein-bound glycyl radicals. Similarly to what was found for N-acetylglycyl (see previous paragraph), the small g-anisotropy for this delocalized, unsymmetrical system presents appreciable challenges to state-of-the-art computational methodology. This pertains to the quality of structure optimization, as well as to the choice of spin-orbit Hamiltonian and gauge origin of the magnetic vector potential. Environmental effects due to hydrogen bonding are complicated and depend in a subtle fashion on the different intramolecular hydrogen bonding for different conformations of the radical. Indeed, the conformation has the largest overall effect on the computed g-tensors (less so on the hyperfine-tensors). We discuss this in the context of different g-tensors obtained by recent HF-EPR measurements for three different enzymes. Based on results of calibration study for N-acetylglycyl, we support that the glycyl radical observed for E.coli anaerobic ribonucleotide reductase (ARNR) has a fully extended conformation, which differs from those of the corresponding radicals in pyruvate formate-lyase (PFL) or benzylsuccinate synthase (BSS).
Herbivorous insects are the major link between primary producers and a multitude of animals at higher trophic levels. Elucidating the causes and consequences of their distribution patterns in the "green world" is thus essential for our understanding of numerous ecological processes on multiple spatial scales. We can ask where and why a certain herbivore can be found in the landscape, within the habitat, on which plant within the habitat and finally, where on that plant. Depending on spatial scale the distribution of herbivores is shaped by different processes (fitness considerations, physiological abilities, population dynamics, dispersal behavior, history of the landscape etc.). Scaling down from fragmented landscapes to individual host plants this thesis analyzes the distribution patterns of the strictly monophagous herbivore Cassida canaliculata Laich. (Coleoptera: Chrysomelidae), which feeds and oviposits exclusively on meadow sage, Salvia pratensis L. (Lamiales: Lamiaceae), and compares it to those of the polyphagous tansy leaf beetle Galeruca tanaceti L. (Coleoptera: Chrysomelidae), which does not oviposit on its host plants, but on dry non-host structures. The specialist Cassida canaliculata depended on all spatial scales (fragmented landscape, microhabitat and host plant individual) mainly on the distribution and quality of its single host plant species Salvia pratensis, whereas enemy-free-space - i.e. avoidance of parasitism and predation of egg clutches, larvae, and pupae - seemed to influence oviposition site choice only on the scale of the host plant individual. On this spatial scale, offspring of Cassida canaliculata had a higher chance of survival on large host plant individuals, which were also preferred for oviposition by the females. In contrast, the distribution patterns of the generalist Galeruca tanaceti was shaped by the interaction with its parasitoid regarding both microhabitat choice and egg distribution within individual host plants. On the microhabitat scale, beetles could escape from their parasitoids by ovipositing into high and dense vegetation. Regarding oviposition site choice within a host plant individual, females oviposited as high as possible in the vegetation and could thus reduce both the risk of parasitism and the probability of winter mortality. The results of my thesis show that the degree of specificity of a herbivore is of central importance for the resulting egg distribution pattern on all spatial scales.
The cyclic nucleotides cAMP and cGMP are two ubiquitous important second messengers, which regulate diverse physiological responses from vision and memory to blood pressure and thrombus formation. They act in cells via cAMP- and cGMP-dependent protein kinases (PKA and GK), cyclic nucleotide-gated channels and Epac. Although the concept of cyclic nucleotide signalling is well developed based on classical biochemical studies, these techniques have not allowed to analyze cAMP and cGMP in live cells with high temporal and spatial resolution. In the present study fluorescence resonance energy transfer was used to develop a technique for visualization of cAMP and cGMP in live cells and in vitro by means of fluorescent biosensors. Ligand-induced conformational change in a single nucleotide-binding domain flanked with green fluorescent protein mutants was used for dynamic, highly sensitive measurements of cAMP and cGMP. Such biosensors retained binding properties and chemical specificity of unmodified domains, allowing to image cyclic nucleotides in a physiologically relevant range of concentrations. To develop cAMP-sensors, binding domains of PKA, Epac and cAMP-gated HCN-channel were used. cGMP-sensors were based on single domains of GK and phosphodiesterases (PDEs). Sensors based on Epac were used to analyze spatio-temporal dynamics of cAMP in neurons and macrophages, demonstrating that cAMP-gradients travel with a high speed (~ 40 μm/s) throughout the entire cytosol. To understand the mechanisms of cAMP-compartmentation, kinetics properties of phosphodi-esterase (PDE2) were, next, analyzed in aldosterone producing cells. PDE2 is able to rapidly hydrolyze extensive amounts of cAMP, so that the speed of cAMP-hydrolysis is much faster than that of its synthesis, which might serve as a basis of compartmentation. cAMP-sensors were also used to develop a clinically relevant diagnostic method for reliable detection of β1-adrenergic receptor autoantibodies in cardiac myopathy patients, which has allowed to significantly increase the sensitivity of previously developed diagnostic approaches. Conformational change in a single binding domain of GK and PDE was, next, used to create novel fluorescent biosensors for cGMP. These sensors demonstrated high spatio-temporal resolution and were applied to analyze rapid dynamics of cGMP production by soluble and particulate guanylyl cyclases as well as to image cGMP in mesangial cells. In summary, highly sensitive biosensors for cAMP and cGMP based on single cyclic nucleotide-binding domains have been developed and used in various biological and clinically relevant applications.
In this thesis affine-scaling-methods for two different types of mathematical problems are considered. The first type of problems are nonlinear optimization problems subject to bound constraints. A class of new affine-scaling Newton-type methods is introduced. The methods are shown to be locally quadratically convergent without assuming strict complementarity of the solution. The new methods differ from previous ones mainly in the choice of the scaling matrix. The second type of problems are semismooth system of equations with bound constraints. A new affine-scaling trust-region method for these problems is developed. The method is shown to have strong global and local convergence properties under suitable assumptions. Numerical results are presented for a number of problems arising from different areas.
In this work we have developed the method of back-transfoprmation within the Douglas-Kroll-Hess (DKH) framework, which has simplified the picture-change consistent transformation of first-order property operators in the DKH approach, making the implementation feasible. This has enabled us to implement the first all-electron scalar relativistic calculations of hyperfine coupling tensors at DKH2 level. Furthemore we have presented a general, relativistic two-component DFT approach for the unrestricted calculations of electronic g-tensors, based on DKH Hamiltonian. Additionally we have derived the expressions for the evaluation of hyperfine structurs and two-component unrestricted treatment of g-tensor within the Resolution of Identity Dirac Kohn Sham method developed by Stanoslav Komorovsky and Michal Repisky in collaboration with other members of the group of V. G. Malkin. All these approaches have been extensively validated.
A hitherto unresolved problem is how workers are prevented from reproducing in large insect societies. The queen informs about her fertility and health which ensures sufficient indirect fitness benefits for workers. In the ant Camponotus floridanus, I found such a signal located on eggs of highly fertile queens. Groups of workers were regularly provided with different sets of brood. Only in groups with queen eggs workers refrain from reproducing. Thus, the eggs seem to inform the workers about queen presence. The signal on queen eggs is presumably the same that enables workers to distinguish between queen and worker-laid eggs, latter are destroyed by workers. Queen and worker-laid eggs differ in their surface hydrocarbons in a similar way as fertile queens differ from workers in the composition of their cuticular hydrocarbons. When I transferred hydrocarbons from the queen cuticle to worker eggs the eggs were no longer destroyed, indicating that they now carry the signal. These hydrocarbons thus represent a queen signal that regulates worker reproduction in this species. But the signal is not present in all fertile queens. Founding queens with low egg-laying rates differ in the composition of cuticular hydrocarbons from queens with high productivity. Similar differences in the composition of surface hydrocarbons were present on their eggs. The queen signal develops along with an increasing fertility and age of the queen, and this is perceived by the workers. Eggs from founding queens were destroyed like worker eggs. This result shows that founding queens lack the appropriate signal. In these little colony foundations chemical communication of queen status may not be necessary to prevent workers from reproducing, since workers may benefit more from investing in colony growth and increased productivity of large colonies rather than from producing male eggs in incipient colonies. If the queen is missing or the productivity of the queen decreases, workers start laying eggs. There is some evidence from correlative studies that, under queenless conditions, worker police each other because of differences in individual odors as a sign of social status. It can be expressed as either aggressive inhibition of ovarian activity, workers with developed ovaries are attacked by nest-mates, or destruction by worker-laid eggs. I found that in C. floridanus workers, in contrast to known studies, police only by egg eating since they are able to discriminate queen- and worker-laid eggs. Workers with developed ovaries will never attacked by nest-mates. This is further supported by qualitative and quantitative differences in the cuticular hydrocarbon profile of queens and workers, whereas profiles of workers with and without developed ovaries show a high similarity. I conclude that workers discriminate worker eggs on the basis of their hydrocarbon profile, but they are not able to recognize egg-laying nest-mates. Improving our knowledge of the proximate mechanisms of the reproductive division of labor in evolutionary derived species like C. floridanus will help to understand the evolution of extreme reproductive altruism involving sterility as a characteristic feature of advanced eusocial systems.
The complexity of membership problems for finite recurrent systems and minimal triangulations
(2006)
The dissertation thesis studies the complexity of membership problems. Generally, membership problems consider the question whether a given object belongs to a set. Object and set are part of the input. The thesis studies the complexity of membership problems for two special kinds of sets. The first problem class asks whether a given natural number belongs to a set of natural numbers. The set of natural numbers is defined via finite recurrent systems: sets are built by iterative application of operations, like union, intersection, complementation and arithmetical operations, to already defined sets. This general problem implies further problems by restricting the set of used operations. The thesis contains completeness results for well-known complexity classes as well as undecidability results for these problems. The second problem class asks whether a given graph is a minimal triangulation of another graph. A graph is a triangulation of another graph, if it is a chordal spanning supergraph of the second graph. If no proper supergraph of the first graph is a triangulation of the second graph, the first graph is a minimal triangulation of the second graph. The complexity of the membership problem for minimal triangulations of several graph classes is investigated. Restricted variants are solved by linear-time algorithms. These algorithms rely on appropriate characterisations of minimal triangulations.