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It was the scope of this work to gain a deeper understanding of the correlation between Interface energetics of molecular semiconductors in planar organic solar cells and the corresponding optoelectronic characteristics. For this aim, different approaches were followed. At first, a direct variation of donor/acceptor (D/A) interface energetics of bilayer cells was achieved by utilizing systematically modified donor compounds. This change could be correlated to the macroscopic device performance. At second, the impact of interface energetics was illustrated, employing a more extended device architecture. By introducing a thin interlayer between a planar D/A heterojunction, an energetic staircase was established. Exciton dissociation in such devices could be linked to the cascade energy level alignment of the photo-active materials. Finally, two different fullerene molecules C60 and C70 were employed in co-evaporated acceptor phases. The expected discrepancy in their electronic structure was related to the transport properties of the corresponding organic photovoltaic cells (OPVCs). The fullerenes are created simultaneously in common synthesis procedures. Next to the photo-physical relevance, the study was carried-out to judge on the necessity of separating the components from each other by purification which constitutes the cost-determining step in the total production costs.
In der vorliegenden Arbeit wurde erfolgreich eine neue Gasphasen-Apparatur für
Photoelektronen-Imaging-Experimente simuliert, aufgebaut und in Verbindung mit einem ps-Lasersystem in Betrieb genommen.
Neben dem Aufbau der Apparatur stand die Aufklärung der Dynamik angeregter Zustände von aromatischen Heterocyclen und Pyrenen im Fokus dieser Arbeit. Die untersuchten Moleküle wurden durch Resonanzverstärkte Mehrphotonenionisation in einem Molekularstrahlexperiment sowohl zeit-, als auch frequenzaufgelöst untersucht.
The Kaapvaal Craton hosts a number of large gold deposits (e.g. Witwatersrand Supergroup) which mining companies have exploited at certain stratigraphic positions. It also hosts the largest platinum group element (PGE) deposits (e.g. Bushveld Igneous Complex) which mining companies have exploited in different mineralised layered magmatic zones. In spite of the extensive exploration history in the Kaapvaal Craton, the origin of the Witwatersrand gold deposits and Bushveld Igneous Complex PGE deposits has remained one of the most debated topics in economic geology. The goal of this study was to identify the geochemical characteristics of marine shales in the Barberton, Witwatersrand, and Transvaal supergroups in South Africa in order to make inferences on their sediment provenance and siderophile element endowments. Understanding why some of the Archaean and Proterozoic hinterlands are heavily mineralised, compared to others with similar geological characteristics, will aid in the development of more efficient exploration models. Fresh, unmineralised marine shales from the Barberton (Fig Tree and Moodies groups), Witwatersrand (West Rand and Central Rand groups), and Transvaal (Black Reef Formation and Pretoria Group) supergroups were sampled from drill core and underground mining exposures. Analytical methods, such as X-ray powder diffraction (XRD), optical microscopy, X-ray fluorescence (XRF), inductively coupled plasma optical emission spectroscopy (ICP-OES), inductively coupled plasma mass spectrometry (ICP-MS), and electron microprobe analysis (EMPA) were applied to comprehensively characterise the shales. All of the Au and PGE assays examined the newly collected shale samples.
The Barberton Supergroup shales consist mainly of quartz, illite, chlorite, and albite, with diverse heavy minerals, including sulfides and oxides, representing the minor constituents. The regionally persistent Witwatersrand Supergroup shales consist mainly of quartz, muscovite, and chlorite, and also contain minor constituents of sulfides and oxides. The Transvaal Supergroup shales comprise quartz, chlorite, and carbonaceous material. Major, trace (including rare-earth element) concentrations were determined for shales from the above supergroups to constrain their source and post-depositional evolution. Chemical variations were observed in all the studied marine shales. Results obtained from this study revealed that post-depositional modification of shale chemistry was significant only near contacts with over- and underlying coarser-grained siliciclastic rocks and along cross-cutting faults, veins, and dykes. Away from such zones, the shale composition remained largely unaltered and can be used to draw inferences concerning sediment provenance and palaeoweathering in the source region and/or on intrabasinal erosion surfaces. Evaluation of weathering profiles through sections of the studied supergroups revealed that the shales therein are characterised by high chemical index of alteration (CIA), chemical index of weathering (CIW), and index of compositional variability (ICV), suggesting that the source area was lithologically complex and subject to intense chemical weathering.
A progressive change in the chemical composition was identified, from a dominant ultramafic–mafic source for the Fig Tree Group to a progressively felsic–plutonic provenance for the Moodies Group. The West Rand Group of the Witwatersrand Supergroup shows a dominance of tonalite–trondhjemite–granodiorite and calcalkaline granite sources. Compositional profiles through the only major marine shale unit within the Central Rand Group indicate the progressive unroofing of a granitic source in an otherwise greenstone-dominated hinterland during the course of sedimentation. No plausible likely tectonic setting was obtained through geochemical modelling. However, the combination of the systematic shale chemistry, geochronology, and sedimentology in the Witwatersrand Supergroup supports the hypothesised passive margin setting for the >2.98 to 2.91 Ga West Rand Group, and an active continental margin source for the overlying >2.90 to 2.78 Ga Central Rand Group, along with a foreland basin setting for the latter.
Ultra-low detection limit analyses of gold and PGE concentrations revealed a variable degree of gold accumulation within pristine unmineralised shales. All the studied shales contain elevated gold and PGE contents relative to the upper continental crust, with marine shales from the Central Rand Group showing the highest Au (±9.85 ppb) enrichment. Based on this variation in the provenance of contemporaneous sediments in different parts of the Kaapvaal Craton, one can infer that the siderophile elements were sourced from a fertile hinterland, but concentrated into the marine shales by a combination of different processes. It is proposed that accumulation of siderophile elements in the studied marine shales was mainly controlled by mechanical coagulation and aggregation. These processes involved suspended sediments, fine gold particles, and other trace elements being trapped in marine environments. Mechanical coagulation and aggregation resulted in gold enrichments by 2–3 orders of magnitude, whereas some of the gold in these marine shales can be reconciled by seawater adsorption into sedimentary pyrite.
For the source of gold and PGEs in the studied marine shales in the Kaapvaal Craton, a genetic model is proposed that involves the following:
(1) A highly siderophile elements enriched upper mantle domain, herein referred to as “geochemically anomalous mantle domain”, from which the Kaapvaal crust was sourced. This mantle domain enriched in highly siderophile elements was formed either by inhomogeneous mixing with cosmic material that was added during intense meteorite bombardment of the Hadaean to Palaeoarchaean Earth or by plume-like ascent of relics from the core–mantle boundary. In both cases, elevated siderophile elements concentrations would be expected. The geochemically anomalous mantle domain is likely the ultimate source of the Witwatersrand modified palaeoplacer gold deposits and was tapped again ca. 2.054 Ga during the emplacement of the Bushveld Igneous Complex. Therefore, I propose that there is a genetic link (i.e. common geochemically anomalous mantle source) between the Witwatersrand gold deposits and the younger Bushveld Igneous Complex PGE deposits.
(2) Scavenging of crustal gold by various surface processes such as trapping of gold from Archaean/Palaeoproterozoic river water on the surface of local photosynthesizing cyanobacterial or microbial mats, and reworking of these mats into erosion channels during flooding events.
The above two models complement each other, with model (1) providing a common geological source for the Witwatersrand gold and Bushveld Igneous Complex PGE deposits, and model (2) explaining the processes responsible for Witwatersrand-type gold pre-concentration processes. In sequences such as the Transvaal Supergroup, a less fertile hinterland and/or less reworking of older sediments led to a correspondingly lower gold endowment. These findings indicate temporal distribution of siderophile elements in the upper crust (e.g. marine shales). The overall implications of these findings are that background concentrations of gold and PGEs can be used to target potential exploration areas in other cratons of similar age. This increases the likelihood of finding other Witwatersrand-type gold or Bushveld Igneous Complex-type PGE deposits in other cratons.
During my PhD I studied two principal biological aspects employing Drosophila melanogaster. Therefore, this study is divided into Part I and II.
Part I: Bruchpilot and Complexin interact to regulate synaptic vesicle tethering to the
active zone cytomatrix
At the presynaptic active zone (AZ) synaptic vesicles (SVs) are often physically linked to an electron-dense cytomatrix – a process referred to as “SV tethering”. This process serves to concentrate SVs in close proximity to their release sites before contacting the SNARE complex for subsequent fusion (Hallermann and Silver, 2013). In Drosophila, the AZ protein Bruchpilot (BRP) is part of the proteinous cytomatrix at which SVs accumulate (Kittel et al., 2006b; Wagh et al., 2006; Fouquet et al., 2009). Intriguingly, truncation of only 1% of the C-terminal region of BRP results in a severe defect in SV tethering to this AZ scaffold (hence named brpnude; Hallermann et al., 2010b).
Consistent with these findings, cell-specific overexpression of a C-terminal BRP fragment, named mBRPC-tip (corresponds to 1% absent in brpnude; m = mobile) phenocopied the brpnude mutant in behavioral and functional experiments. These data indicate that mBRPC-tip suffices to saturate putative SV binding sites, which induced a functional tethering deficit at motoneuronal AZs. However, the molecular identity of the BRP complement to tether SVs to the presynaptic AZ scaffold remains unknown. Moreover, within larval motoneurons membrane-attached C-terminal portions of BRP were sufficient to tether SVs to sites outside of the AZ. Based on this finding a genetic screen was designed to identify BRP interactors in vivo. This screen identified Complexin (CPX), which is known to inhibit spontaneous SV fusion and to enhance stimulus evoked SV release (Huntwork and Littleton, 2007; Cho et al., 2010; Martin et al., 2011). However, so far CPX has not been associated with a function upstream of priming/docking and release of SVs. This work provides morphological and functional evidence, which suggests that CPX promotes recruitment of SVs to the AZ and thereby curtails synaptic short-term depression. Together, the presented findings indicate a functional interaction between BRP and CPX at Drosophila AZs.
Part II: The Adhesion-GPCR Latrophilin/CIRL shapes mechanosensation
The calcium independent receptor of α-latrotoxin (CIRL), also named Latrophilin, represents a prototypic Adhesion class G-protein coupled-receptor (aGPCR). Initially, Latrophilin was identified based on its capacity to bind the α-component of latrotoxin (α-LTX; Davletov et al., 1996; Krasnoperov et al., 1996), which triggers massive exocytotic activity from neurons of the peripheral nervous system (Scheer et al., 1984; Umbach et al., 1998; Orlova et al., 2000). As a result Latrophilin is considered to play a role in synaptic transmission. Later on, Latrophilins have been associated with other biological processes including tissue polarity (Langenhan et al., 2009), fertility (Prömel et al., 2012) and synaptogenesis (Silva et al., 2011). However, thus far its subcellular localization and the identity of endogenous ligands, two aspects crucial for the comprehension of Latrophilin’s in vivo function, remain enigmatic.
Drosophila contains only one latrophilin homolog, named dCirl, whose function has not been investigated thus far.
This study demonstrates abundant dCirl expression throughout the nervous system of Drosophila larvae. dCirlKO animals are viable and display no defects in development and neuronal differentiation. However, dCirl appears to influence the dimension of the postsynaptic sub-synaptic reticulum (SSR), which was accompanied by an increase in the postsynaptic Discs-large abundance (DLG). In contrast, morphological and functional properties of presynaptic motoneurons were not compromised by the removal of dCirl. Instead, dCirl is required for the perception of mechanical challenges (acoustic-, tactile- and proprioceptive stimuli) through specialized mechanosensory devices, chordotonal organs (Eberl, 1999). The data indicate that dCirl modulates the sensitivity of chordotonal neurons towards mechanical stimulation and thereby adjusts their input-output relation. Genetic interaction analyses suggest that adaption of the molecular mechanotransduction machinery by dCirl may underlie this process. Together, these results uncover an unexpected function of Latrophilin/dCIRL in mechanosensation and imply general modulatory roles of aGPCR in mechanoception.
Platelets are continuously produced from megakaryocytes (MK) in the bone marrow by a cytoskeleton-driven process of which the molecular regulation is not fully understood.
As revealed in this thesis, MK/ platelet-specific Profilin1 (Pfn1) deficiency results in micro- thrombocytopenia, a hallmark of the Wiskott-Aldrich syndrome (WAS) in humans, due to accelerated platelet turnover and premature platelet release into the bone marrow. Both Pfn1-deficient mouse platelets and platelets isolated from WAS patients contained abnormally organized and hyper-stable microtubules. These results reveal an unexpected function of Pfn1 as a regulator of microtubule organization and point to a previously unrecognized mechanism underlying the platelet formation defect in WAS patients.
In contrast, Twinfilin2a (Twf2a) was established as a central regulator of platelet reactivity and turnover. Twf2a-deficient mice revealed an age-dependent macrothrombocytopenia that could be explained by a markedly decreased platelet half-life, likely due to the pronounced hyper-reactivity of \(Twf2a^{-/-}\) platelets. The latter was characterized by sustained integrin acti- vation and thrombin generation in vitro that translated into accelerated thrombus formation in vivo. To further elucidate mechanisms of integrin activation, Rap1-GTP-interacting adaptor molecule (RIAM)-null mice were generated. Despite the proposed critical role of RIAM for platelet integrin activation, no alterations in this process could be found and it was concluded that RIAM is dispensable for the activation of β1 and β3 integrins, at least in platelets. These findings change the current mechanistic understanding of platelet integrin activation.
Outside-in signaling by integrins and other surface receptors was supposed to regulate MK migration, but also the temporal and spatial formation of proplatelet protrusions. In this the- sis, phospholipase D (PLD) was revealed as critical regulator of actin dynamics and podo- some formation in MKs. Hence, the unaltered platelet counts and production in \(Pld1/2^{-/-}\) mice and the absence of a premature platelet release in the bone marrow of \(Itga2^{-/-}\) mice question the role of podosomes in platelet production and raise the need to reconsider the proposed inhibitory signaling by α2β1 integrins on proplatelet formation.
Non-muscle myosin IIA (NMMIIA) has been implicated as a downstream effector of the in- hibitory signals transmitted via α2β1 integrins. Besides Rho-GTPase signaling, also \(Mg^{2+}\) and transient receptor potential melastatin-like 7 (TRPM7) channel α-kinase are known regulators of NMMIIA activity. In this thesis, TRPM7 was identified as major regulator of \(Mg^{2+}\) homeostasis in MKs and platelets. Furthermore, decreased \([Mg^{2+}]_i\) led to deregulated NMMIIA activity and altered cytoskeletal dynamics that impaired thrombopoiesis and resulted in macrothrombocytopenia in humans and mice.
In der vorliegenden Arbeit wurden die Effekte des neurotrophen Faktors GDNF auf die Struktur und Funktion der intestinalen Epithelbarriere untersucht. Zellkulturen mit Caco2 beziehungsweise HT29B6 dienten als Modellsysteme für die Epithelschicht der Darmschleimhaut. Transwellsassays und TER-Messungen mittels ECIS-Gerät fungierten als zentrale Untersuchungsmethoden zur Evaluation der funktionellen Barriereeigenschaft der Zellmonolayer. Die morphologischen und quantitativen Veränderungen von Zelljunktionsproteinen wurden mittels indirekter Immunfluoreszenzfärbungen beziehungsweise Western Blot-Untersuchungen dargestellt. Um Migration- und Proliferationsverhalten nach Verletzung des Zellmonolayers zu untersuchen, führten wir in vitro-Scratch-Assays durch.
Zunächst wurde bestätigt, dass intestinale Epithelzellen die GDNF-Rezeptoren GFRα1, GFRα2 und RET exprimieren. Es zeigte sich sowohl in Immunfärbungen gegen Junktionsproteine als auch in Permeabilitätsmessungen, dass GDNF zu einer verstärkten Differenzierung der intestinalen Epithelbarriere führt. In Inhibitions- und Aktivierungsexperimenten mit verschiedenen Mediatoren wurde als zugrunde liegender Mechanismus die Inaktiverung der p38 MAPK durch GDNF identifiziert. Weiterhin zeigten Versuche mit epithelialen Wundheilungsassays, dass GDNF, über eine cAMP/PKA-abhängige Induktion der Proliferation, zu einer Verbesserung der Wundheilung führt. In Immunfärbungen und Western Blot-Analysen wurde beobachtet, dass auch intestinale Epithelzelllinien in der Lage sind GDNF zu synthetisieren.
Zusammenfassend konnte in der vorliegenden Arbeit erstmals gezeigt werden, dass der neurotrophe Faktor GDNF direkt auf die Differenzierung und Proliferation von kultivierten Enterozyten Einfluss nehmen kann. Die Tatsache, dass intestinale Epithelzellen selbst GDNF synthetisieren und sezernieren können, weist auf einen neuen autokrinen- oder parakrinen Wirkmechanismus des neurotrophen Faktors hin.
Im Rahmen dieser Arbeit wurden Fibroblasten und Keratinozyten, welche in vitro auf unterschiedlichen Scaffolds sowohl gemeinsam als auch in Monokulturen gezüchtet wurden, mittels Real-time PCR auf ihre Genausschüttung untersucht, um festzustellen wie sich die Unterlage auf die Genausschüttung auswirkt. Hierzu wurden die Proben sowohl auf die Genexpressionsmarker für die Basallamina Kollagen IV, Laminin 1 und 5 als auch auf die Genexpressionsmarker für die frühe Differenzierung Keratin K13 und K14 untersucht. Als Referenzgen wurde β-Actin ausgewählt, da dieses Gen in den Vorversuchen mit zwei weiteren Referenzgenen die stabilste Expression gezeigt hatte. Die Genexpressionsanalyse zeigte, dass nur in den Kokulturen von Keratinozyten und Fibroblasten eine ausgewogene Genexpression stattfindet, da sich die Zellen darin beeinflussen und regulieren.
Dementia is a complex neurodegenerative syndrome that by 2050 could affect about 135 Million people worldwide. People with dementia experience a progressive decline in their cognitive abilities and have serious problems coping with activities of daily living, including
orientation and wayfinding tasks. They even experience difficulties in finding their way in a familiar environment. Being lost or fear of getting lost may consequently develop into other psychological deficits such as anxiety, suspicions, illusions, and aggression. Frequent results are social isolation and a reduced quality of life. Moreover, the lives of relatives and
caregivers of people with dementia are also negatively affected.
Regarding navigation and orientation, most existing approaches focus on outdoor environment and people with mild dementia, who have the capability to use mobile devices. However, Rasquin (2007) observe that even a device with three buttons may be too complicated for
people with moderate to severe dementia. In addition, people who are living in care homes mainly perform indoor activities. Given this background, we decided to focus on designing a system for indoor environments for people with moderate to severe dementia, who are unable
or reluctant to use smartphone technology.
Adopting user-centered design approach, context and requirements of people with dementia were gathered as a first step to understand needs and difficulties (especially in spatial disorientation and wayfinding problems) experienced in dementia care facilities. Then, an "Implicit Interactive Intelligent (III) Environment" for people with dementia was proposed emphasizing implicit interaction and natural interface. The backbone of this III Environment is based on supporting orientation and navigation tasks with three systems: a Monitoring system, an intelligent system, and a guiding system. The monitoring system and intelligent system automatically detect and interpret the locations and activities performed by the users i.e. people with dementia. This approach (implicit input) reduces cognitive workload as well as physical workload on the user to provide input. The intelligent system is also aware of context, predicts next situations (location, activity), and decides when to provide an appropriate service to the users. The guiding system with intuitive and dynamic environmental cues (lighting with color) has the responsibility for guiding the users to the places they need to be.
Overall, three types of a monitoring system with Ultra-Wideband and iBeacon technologies, different techniques and algorithms were implemented for different contexts of use.
They showed a high user acceptance with a reasonable price as well as decent accuracy and precision. In the intelligent system, models were built to recognize the users’ current activity, detect the erroneous activity, predict the next location and activity, and analyze the
history data, detect issues, notify them and suggest solutions to caregivers via visualized web interfaces. About the guiding systems, five studies were conducted to test and evaluate the effect of lighting with color on people with dementia. The results were promising. Although
several components of III Environment in general and three systems, in particular, are in place (implemented and tested separately), integrating them all together and employing this in the dementia context as a fully properly evaluation with formal stakeholders (people with
dementia and caregivers) are needed for the future step.
Social life is organized around rules and norms. The present experiments investigate the cognitive architecture of rule violations. To do so, a setting with arbitrary rules that had to be followed or broken was developed, and breaking these rules did not have any negative consequences. Removed from any social influences that might further encourage or hinder the rule breaker, results suggest that simply labeling a behavior as a rule violation comes with specific costs: They are more difficult to plan and come with specific behavioral markers during execution. In essence, rule violations resemble rule negations, but they also trigger additional processes.
The question of what makes rule violations more difficult than rule inversions is the major focus of the remaining experiments. These experiments revealed negative affective consequences of rule violation and rule inversions alike, while rule violations additionally prime authority-related concepts, thus sensitizing towards authority related stimuli.
Next, the question how these burdens of non-conformity can be mitigated was investigated, and the influence of having executed the behavior in question frequently and recently was tested in both negations and rule violations. The burdens of non-conformity can best be reduced by a combination of having violated/negated a rule very frequently and very recently. Transfer from another task, however, could not be identified.
To conclude, a model that accounts for the data that is currently presented is proposed. As a variant of a task switching model, it describes the cognitive processes that were investigated and highlights unique processing steps that rule violations seem to require.
Polyneuropathien sind Erkrankungen des peripheren Nervensystems. Die Erkrankung kommt gehäuft als Zweiterkrankungen bei anderen Primärerkrankungen vor, daher ist es schwierig, epidemiologische Angaben zu machen.
Ätiologisch lassen sich Polyneuropathien in fünf große Gruppen einteilen: Hereditäre Polyneuropathien, entzündliche Polyneuropathien, vaskulär bedingte Polyneuropathien, exotoxische Polyneuropathien und endotoxisch-metabolische Polyneuropathien. Die Differentialdiagnose der Polyneuropathie richtet sich nach dem zeitlichen Verlauf der Krankheit, dem betroffenen System und danach, ob primär die Axone oder die Markscheiden betroffen sind.
Für die Diagnosestellung einer Polyneuropathie werden Anamnese und klinischer Befund, elektrophysiologische Untersuchungen, Laboruntersuchungen, genetische Untersuchungen und die histopathologische Untersuchung herangezogen. Entscheidend für die Therapie ist es, die behandelbaren Polyneuropathien zu erkennen, hierunter u.a. die entzündlichen Formen. Die hierfür entnommene Suralisbiopsie ist wegen ihrer invasiven Natur erst dann indiziert, wenn die Differentialdiagnose mit nicht-invasiven Maßnahmen nicht geklärt werden kann, sich aber eine Behandlungskonsequenz erwarten lässt.
Die exakte Diagnose setzt bei einigen Polyneuropathien eine neuropathologische Diagnostik voraus. Die Nervenbiopsie muss optimal aufbereitet und ausgewertet werden. Hierfür stehen verschiedene Färbe- und Aufbereitungsmethoden zur Verfügung.
In dieser Arbeit wurde untersucht, ob anhand eines Schnellschnittes (d.h. Gefrier-Querschnitt des biopsierten Nerven mit Hämatoxylin-Eosin gefärbt) bereits Hinweise auf entzündliche Infiltrate als Zeichen einer Neuritis und damit einer therapiebedürftigen und aber auch therapierbaren Neuropathie gefunden werden können.
Anhand eines vordefinierten Schemas wurden die Biopsate in verblindeter Weise von einem Laien und einem erfahrenem Untersucher histologisch begutachtet und den entzündlichen/nicht entzündlichen Diagnosegruppen zugeordnet. Es wurde untersucht, ob die entzündlichen Veränderungen im Hämatoxylin-Eosin-Gefrierschnitt so deutlich sind, dass auch ein Laienauswerter diese erkennen kann. Ebenso wurden die Untersuchungsergebnisse mittels Hämatoxylin-Eosin- Färbung an Gefrier- und Paraffinschnitten mit den Untersuchungsergebnissen mittels immunhistochemischer Färbemethoden verglichen. Des weiteren wurde untersucht, ob bei histologisch gesicherter Entzündung klinische Einflussfaktoren ermittelt werden können, die auf die neuropathologische Diagnostik Auswirkung haben.
Die Ergebnisse der Studie zeigen, dass sich die Hämatoxylin-Eosin-Färbung für eine erste und schnelle Diagnostik von entzündlichen Polyneuropathien als wertvoll erwies. Dies gilt für den erfahrenen und unerfahrenen Untersucher. Es zeigen sich keine klinischen Einflussfaktoren für die histopathologische Diagnosestellung. Die Ergebnisse der Studie zeigen, dass schon eine einfache Färbemethode wie die Hämatoxylin-Eosin-Färbung an Gefrier-und Paraffinschnitten bei Polyneuropathie unklarer Genese hilfreich bei einer differenzierten Diagnosefindung sein kann.
Effects of timing and herbivory on a grass-endophyte association and its trophic interactions
(2017)
I.) Plant associated microorganisms can affect the plant`s interaction with herbivores and higher trophic levels. For instance, endophytic fungi infecting aerial plant parts of grass species produce bioactive alkaloids that can negatively affect species from higher trophic levels, indicating a defensive mutualism between the grass and the endophyte. However, beneficial insects can also be negatively affected by the endophyte, which might question the mutualistic effect of endophytic fungi. On the other hand, grass-endophytes are affected by environmental conditions and species interactions. Grazing can increase endophyte frequencies in natural habitats. Furthermore, endophyte mediated effects on herbivores are most pronounced during warm summers following rainy springs. In this study, we investigated whether endophyte derived alkaloids cascade up a food chain (chapter II) and whether their concentrations depend on plant age and season (chapter III). Further we analysed, whether altered herbivore phenology affects the endophytic fungus (chapter IV) and whether endophyte derived alkaloid production is induced by different herbivore species (chapter V).
II.) In our first experimental study we analysed whether grass-endophyte derived alkaloids decreased the performance of two ladybird species feeding on aphids exclusively reared on endophyte infected grass (6 weeks young grass). Further, we screened species from three trophic levels (grass, herbivores and aphid predators) for their alkaloid content using two year old infected grass as diet for herbivores. We established an UPLC-MS method to detect and quantify the amount of the endophyte derived alkaloids peramine and lolitrem B extracted from the organic plant and insect material. Performance parameters of ladybirds revealed little differences between ladybirds fed on aphids reared on endophyte infected and non-infected grass, which probably resulted from low alkaloid concentrations in the young (6-weeks old) endophyte infected grass used in this part of the study. Alkaloid quantification of the two year old endophyte infected grass, herbivores and aphid predators revealed similar concentrations between grass and aphids, while aphid predators contained approximately half of that amount which still exceeded the bioactive threshold. We conclude that alkaloids produced by grass-endophytes cascade up the food chain and are responsible for fitness disadvantages of higher trophic levels.
III.) In the second study we investigated the impact of plant age and seasonal timing on grass-endophyte growth and alkaloid production. Plants were sown in April of 2013 and sampled monthly over 30 consecutive months. Endophyte growth was quantified with real-time PCR (qPCR) and alkaloid concentrations with UPLC-MS. We showed that alkaloid concentrations and fungal growth followed a seasonal rhythmicity and that alkaloid concentrations increased with plant age. Alkaloid concentrations peak during summer, when also herbivore abundances are high. Consequently, we conclude that plant age and season contribute to the toxicity of endophytes on grass herbivores
IV.) In the third study we simulated earlier spring arrival of aphids by enhancing aphid abundance on endophyte infected and endophyte-free grass in spring and analysed responses across three trophic levels. Enhanced aphid abundance in spring caused higher aphid abundances during the study period. Predators stayed unaffected by increased herbivore abundances; however they did level aphid numbers within two weeks after arrival on the plants, independent of aphid abundance. Grass-endophyte showed a time delayed growth, two weeks after aphid abundance peak and after predators already controlled aphid infestations on the plants. We conclude that phenology shifts of herbivorous insects can affect multi-trophic interactions leading to desynchronizations between phenologies of interacting species and mismatches in food-webs.
V.) In the fourth study we analysed whether herbivores induce endophyte growth and alkaloid production and whether different types of herbivores induce specific alkaloid production. We applied three different herbivore treatments on endophyte infected grass over 18 weeks. Locust herbivory increased the insect deterring alkaloid peramine and clipping of plants (simulation of grazing livestock) increased the vertebrate toxic alkaloid lolitrem B. Aphid herbivory did not affect endophyte derived alkaloid concentrations. Endophyte responses to herbivory were species specific which indicates a primarily plant protecting role of alkaloid synthesis in endophyte infected plants and a close chemical crosstalk between interacting species.
VI.) In summary, we showed that endophyte derived alkaloids affect higher trophic levels and that alkaloid concentrations in the plant depend on prevalent herbivore species, plant age and seasonal timing. Our results indicate a close chemical crosstalk between the host plant and the endophytic fungus which is susceptible to environmental changes altering the endophyte`s alkaloid production in plants. We gained insights into the grass-endophyte symbiosis in ecological contexts and conclude that several factors determine the herbivore toxic potential of endophytic fungi and thereby their plant mutualistic or parasitic character. Future studies should investigate the mechanisms behind the herbivore induced alkaloid concentration increase, shown in this thesis, especially whether plant signals mediate the endophyte response. Furthermore it would be interesting to study the induction of indirect endophyte mediated defence and how it affects multi-trophic level interactions.
Optical antennas work similar to antennas for the radio-frequency regime and convert electromagnetic radiation into oscillating electrical currents. Charge density accumulations form at the antenna surface leading to strong and localized near-fields. Since most optical antennas have dimensions of a few hundred nanometers, their near-fields allow the focusing of electromagnetic fields to volumes much smaller than the diffraction limit, with intensities several orders of magnitude larger than achievable with classical diffractive and refractive optical elements. The task to maximize the emission of a quantum emitter, a point-like entity capable of reception and emission of single photons, is identical to the task to maximize the field intensity at the position of the quantum emitter. Therefore it is desirable to optimize the capabilities of focusing optical antennas.
Radio-frequency-antenna designs scaled to optical dimensions of several hundred nanometers show already a decent performance. However, optical frequencies lie near the plasma frequency of the metals used for optical antennas and the mass of electrons cannot be neglected anymore. This leads to new physical phenomena. Light can couple to charge density oscillations, yielding a so-called Plasmon. Effects emerge which have no equivalent in the very advanced field of radio-frequency-technology, e.g.~volume currents and shortened effective wavelengths. Additionally the conductivity is not infinite anymore, leading to thermal losses. Therefore, the question for the optimal geometry of a focusing optical antenna is not easy to answer. However, up to now there was no evidence that there exist better alternatives for optical antennas than down-scaled radio-frequency designs.
In this work the optimization of focusing optical antennas is based on an approach, which often proved successful for radio-frequency-antennas in complex applications (e.g.~broadband and isotropic reception): evolutionary algorithms. The first implementation introduced here allows a large freedom regarding particle shape and count, as it arranges cubic voxels on a planar, square grid. The geometries are encoded in a binary matrix, which works as a genome and enables the methods of mutation and crossing as mechanism of improvement. Antenna geometries optimized in this way surpass a comparable dipolar geometry by a factor of 2. Moreover, a new working principle can be deduced from the optimized antennas: a magnetic split-ring resonance can be coupled conductively to dipolar antennas, to form novel and more effective split-ring-antennas, as their currents add up constructively near the focal point.
In a next step, the evolutionary algorithm is adapted so that the binary matrices describe geometries with realistic fabrication constraints. In addition a 'printer driver' is developed which converts the binary matrices into commands for focused ion-beam milling in mono-crystalline gold flakes. It is shown by means of confocal two-photon photo-luminescence microscopy that antennas with differing efficiency can be fabricated reliably directly from the evolutionary algorithm. Besides, the concept of the split-ring antenna is further improved by adding this time two split-rings to the dipole-like resonance.
The best geometry from the second evolutionary algorithm inspires a fundamentally new formalism to determine the power transfer between an antenna and a point dipole, best termed 'three-dimensional mode-matching'. Therewith, for the first time intuitive design rules for the geometry of an focusing optical antenna can be deduced. The validity of the theory is proven analytically at the case of a point dipole in from of a metallic nano sphere.
The full problem of focusing light by means of an optical antenna can, thus, be reduced to two simultaneous mode-matching conditions -- on the one hand with the fields of a point dipole, on the other hand with a plane wave. Therefore, two types of ideal focusing optical antenna mode patterns are identified, being fundamentally different from the established dipolar antenna mode. This allows not only to explain the functionality of the evolutionary antennas and the split-ring antenna, but also helps to design novel plamonic cavity antennas, which lead to an enhanced focusing of light. This is proven numerically in direct comparison to a classical dipole antenna design.
The genus Ficaria is now considered to comprize eight Eurasian species. The most widespread European species is the tetraploid F. verna Huds. The present study provides evidence for the existence of two main lineages of F. verna that differ considerably in their genomic size by about 3 pg. A Western F. verna lineage west of river Rhine displays a mean genome size (2C-value) of 34.2 pg and is almost precisely codistributed with the diploid F. ambigua Boreau (20 pg) north of the Mediterranean. The remaining part of Europe appears to be occupied by the Eastern F. verna lineage solely (mean genome size of 31.3 pg) which codistributes in South-Eastern Europe with the diploid F. calthifolia Rchb. (15 pg). There is little overlap at the boundary of Western and Eastern F. verna lineages with the occurrence of a separate intermediate group in the Netherlands (mean genomic size of 33.2 pg) that appears to result from hybridization of both lineages. On the basis of these observations and further considerations we propose development of F. ambigua and F. calthifolia south of the Alps with subsequent divergence to populate their current Western and Eastern European ranges, respectively. The Western F. verna lineage is proposed to originate from autotetraploidization of F. ambigua (precursor) with moderate genomic downsizing and the Eastern F. verna lineage from auto¬tetraploidization of F. calthifolia (precursor).
Jahresbericht 2014/2015
(2017)
Jahresbericht 2012/2013
(2017)
Der M. Fabry ist eine X-chromosomal vererbte lysosomale Speicherkankheit, die zu einem Multiorganversagen führt. Ein frühes Symptom sind Schmerzen, die meist schon in der frühen Kindheit einsetzen. Das Besondere an diesen Schmerzen ist, dass sie sich sehr unterschiedlich u.a. bezüglich ihres Verlaufs, ihrer Dauer und ihrer Lokalisation präsentieren können. Diese Fabry-assoziierten Schmerzen sind meist brennend und akral betont, können aber auch andere Qualitäten aufweisen und sehr variable Körperpartien erfassen, was ihre diagnostische Einordnung erschwert. Bisher verfügbare validierte Schmerzfragebögen können das Spektrum der Fabry-assoziierten Schmerzen nicht erfassen. In dieser Arbeit wird der erste M. Fabry spezifische Schmerzfragebogen für Erwachsene in zwei Versionen präsentiert. Die erste Version ist eine Interview Version (iFPQ), bei der der Arzt in einem persönlichen Gespräch mit dem Patienten mit Hilfe des Fragbogens alle wesentlichen Aspekte der Fabry-assoziierten Schmerzen erfragen kann. Die zweite Version kann eigenständig vom Patienten ausgefüllt werden (saFPQ). Zur Etablierung der Fragebögen wurde in einer Pilotstudie zunächst mit 20 Patienten eine erste Version des iFPQ entwickelt. Nach Verbesserungen wurde die Interview Version mit Hilfe von 42 Studienteilnehmern validiert, die jeweils an einem Erst- und Zweitgespräch im Abstand von zwei Wochen teilnahmen. Hierbei wurde auch der NPSI als vergleichender Fragebogen ausgefüllt. Bei der ersten statistischen Analyse ergab sich eine gute Reliabilität mit ICC-Werten von 0,896 bis 0,999 aber eine unzureichende Validität zwischen iFPQ und NPSI mit K-Werten von 0,257 bis 0,566. Nach der ersten statistischen Analyse wurde der Fragebogen erneut überarbeitet und mit Hilfe von 20 Studienteilnehmern erneut validiert. Anschließend zeigte sich eine gute Validität mit K-Werten von 0,634 bis 1,0. Der saFPQ wurde im Anschluss an die finale iFPQ Version entwickelt. Bei 40 Patienten erfolgte ein Erstgespräch, bei dem die Patienten die valide Version des iFPQ ausfüllten. Im Abstand von zwei Wochen schickten die Patienten dann die selbständig ausgefüllte Version des saFPQ postalisch zurück. Die postalische Version erweitert die Flexibilität dieses Fragebogens. Sie ist für den klinischen Alltag sehr relevant. Die Resonanz der Patienten hinsichtlich beider Fragebögen war sehr positiv. Perspektivisch ist die Entwicklung einer englischen Version geplant.
Ausgehend von der Hypothese, dass die in dieser Arbeit eingesetzten Substanzen Natriumnitroprussid, Magnesium und Clazosentan aus pathophysiologischen Überlegungen dem in der Frühphase nach SAB auftretenden Perfusionsdefizit entgegenwirken und neuroprotektive Wirkung entfalten können, hat diese Arbeit das Ziel verfolgt, konkrete Therapieansätze zu entwickeln, die für die Behandlung der frühen Durchblutungsstörung nach einer SAB geeignet sein könnten. Ebenso sollte das neuroprotektive Potenzial dieser Substanzen, bei denen es sich um klinisch bereits getestete Medikamente handelt, evaluiert werden. Hierzu wurden drei Versuchsreihen unternommen, die folgende Ergebnisse erbrachten:
Die Gabe des NO-Donators Natriumnitroprussid erwies sich als die zerebrale Perfusion in der Frühphase nach SAB signifikant steigernd. Damit einhergehend zeigte sich eine signifikante Reduktion der neuronalen Schädigung im Hippocampus. Insgesamt legt diese Arbeit also das therapeutische Potential dieser Substanz für die Frühphase nach SAB nahe.
Für Magnesium konnte im Rahmen dieser Arbeit kein perfusionssteigernder Effekt festgestellt werden. Die hier erhobenen Daten weisen allerdings auf ein mögliches neuroprotektives Potential dieser Substanz hin, sodass weitere Studien größeren Umfangs angestrebt werden sollten, um eine neuroprotektive Wirkung verifizieren zu können.
Von dem ETA-Antagonisten Clazosentan wurden drei Dosierungen auf ihr neuroprotektives und perfusionssteigerndes Potential hin getestet. Hinsichtlich des perfusionssteigernden Effektes erwies sich die Maximaldosis zwar als deutlich überlegen, verfehlte jedoch zu den Zeitpunkten 120, 150 und 180 Minuten nach SAB knapp das Signifikanzniveau. Ein neuroprotektives Potential kann auf Grundlage einer knappen Signifikanz in der H&E-Färbung vermutet, aber nicht sicher konstatiert, werden.
Das Ziel dieses größer angelegten Projekts ist die Entwicklung einer Kombinationstherapie aus unterschiedlichen Methoden und Medikamenten. Basierend auf den hier vorgestellten Ergebnissen kommen von den in dieser Arbeit untersuchten Substanzen insbesondere der NO-Donator Natriumnitroprussid, aber auch der ETA-Antagonist Clazosentan in Frage. Als mögliche Kombinationspartner könnten Prostazyklin-Agonisten oder Thrombozytenaggregationshemmer eingesetzt werden. Daneben sind die Anwendung einer moderaten Hypothermie sowie die Gabe hyperonkotischer Lösungen therapeutische Ansätze, die im weiteren Verlauf dieses Projekts untersucht werden.
Wi man di ku fom ais kricht. Mit dem Grundschul-Wortschatz eine sichere Rechtschreibung erlernen
(2017)
Die Grundschulwörterliste ist eine Sammlung von ca. 6400 Wörtern bzw. Wortverbindungen auf knapp 280 Seiten, die es erleichtern sollen, Übungsdiktate für Grundschulkinder zu erstellen. Sie richtet sich damit vornehmlich an LehrerInnen, aber auch an LerntherapeutInnen und die Eltern der Kinder für das Lernen in der Schule, im Nachhilfeinstitut oder zu Hause. Die Wörterlisten basieren auf den Grundwortschätzen verschiedener Grundschullehrpläne und den Wörterlisten im Anhang von über 60 Schulbüchern. Damit decken sie repräsentativ den in der Rechtschreibung zu erlernenden Wortschatz ab und ermöglichen es darüber hinaus, durch spezielle Themenlisten Übungstexte mit spezifischen orthographischen Schwerpunkten zusammenzustellen.
An der Ausbildung der individuellen Persönlichkeitseigenschaften eines Menschen sowie an der Entstehung von Persönlichkeitsstörungen und anderen psychischen Erkrankungen sind sowohl genetische Faktoren als auch Umwelteinflüsse beteiligt. Mittels Assoziationsstudien kann man prüfen, ob zwischen einzelnen genetischen Varianten und Persönlichkeitsmerkmalen bzw. psychischen Störungen ein Zusammenhang besteht. Im Rahmen der vorliegenden Arbeit wurden funktionelle Polymorphismen in zwei Kandidatengenen, der Dopamin-β-Hydroxylase (DBH) und der neuronalen NO-Synthase (NOS1), im Hinblick auf eine Assoziation mit Persönlichkeitsvariablen und Persönlichkeitsstörungen untersucht. Diese Enzyme spielen eine wichtige Rolle im noradrenergen bzw. nitrinergen System, die beide an der Steuerung des Verhaltens entscheidend beteiligt sind. Des Weiteren wurde geprüft, ob der Polymorphismus im Promotorbereich des DBH-Gens mit affektiven Störungen assoziiert ist. Die Genotypisierung wurde bei 642 Probanden mit Persönlichkeitsstörungen und 182 Patienten mit affektiven Störungen durchgeführt; die Kontrollgruppen umfassten 387 Personen (DBH-Polymorphismus) bzw. 494 Personen (NOS1-Polymorphismen).
Eine Assoziation des -1021C→T-Polymorphismus des DBH-Gens mit affektiven Störungen ließ sich nicht nachweisen, obwohl Vorbefunde einen Zusammenhang zwischen dem mit einer niedrigen Plasmaaktivität der Dopamin-β-Hydroxylase assoziierten T/T-Genotyp und affektiven Störungen nahegelegt hatten. Diese Assoziation findet sich jedoch möglicherweise nur bei Subgruppen affektiver Störungen wie z. B. Depressionen mit psychotischer Symptomatik. Eine hochsignifikante Assoziation zeigte sich zwischen dem T/T-Genotyp und dem Auftreten von zwei oder mehr Persönlichkeitsstörungen, so dass dieser Genotyp als Risikofaktor für die Entwicklung von Persönlichkeitsstörungen angesehen werden kann. Des Weiteren ist der T/T-Genotyp mit verschiedenen Subskalen von Neuroticism, Agreeableness und Novelty Seeking assoziiert, die sich auf impulsives, feindseliges und wenig zielgerichtetes Verhalten beziehen. Dies bestätigt die Ergebnisse früherer Studien, die einen Zusammenhang zwischen dem noradrenergen System und impulsiven Verhaltensweisen gezeigt haben.
Zahlreiche Studien weisen auch auf eine Verbindung zwischen Veränderungen des NOS1-Gens und impulsivem, aggressivem Verhalten hin. Im Rahmen dieser Arbeit konnte eine Assoziation beider NOS1-Polymorphismen mit Cluster-B-Persönlichkeitsstörungen beobachtet werden, die Impulsivität als ein gemeinsames Merkmal aufweisen. Es fand sich jedoch keine Assoziation mit Persönlichkeitsdimensionen, die impulsives und aggressives Verhalten widerspiegeln. In einer Weiterführung der vorliegenden Studie mit größeren Probandenzahlen wurde erneut der Zusammenhang zwischen einem dieser NOS1-Polymorphismen, dem Exon-1f-VNTR, und Persönlichkeitsvariablen sowie dem durch gesteigerte Impulsivität gekennzeichneten Aufmerksamkeitsdefizit- und Hyperaktivitätssyndrom (ADHS) bei erwachsenen Patienten untersucht. In dieser Studie wurde in der Kontrollgruppe eine nur bei Frauen statistisch signifikante Assoziation des kurzen Allels mit niedrigen Conscientiousness-Werten, die als Anzeichen für ein hohes Maß an Impulsivität verstanden werden können, beobachtet. Auch eine Assoziation des kurzen Allels mit ADHS konnte nachgewiesen werden, was die Bedeutung dieses Polymorphismus bei der Entstehung impulsiver Verhaltensweisen weiter untermauert.
Zur Aufdeckung der genetischen Grundlage von Persönlichkeitseigenschaften und psychischen Erkrankungen bedarf es der Identifizierung weiterer genetischer Risikovarianten und deren Untersuchung in großen Assoziationsstudien mit einer hohen Probandenzahl. Um den Zusammenhang zwischen genetischen Varianten und Persönlichkeit bzw. Verhalten zu erhellen, müssen zudem komplexe Interaktionen verschiedener Gene und der Einfluss von Umweltfaktoren einbezogen werden.