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Phenology is the study of periodic life cycle events of living organisms and how these are influenced by environmental factors. Late phenological phases such as the timing of seed release and subsequent seed dispersal considerably affect ecology and evolution in plants. Since plants are mostly sessile organisms, seed dispersal is a crucial life cycle event for the ecology and evolution of plants. In fact, long-distance seed dispersal (LDD) is a very complex process in plant biology and significantly shapes the spatial and temporal dynamics of plant populations. For example, wind dispersal in plants is influenced by a variety of factors such as plant traits, habitat type and environmental conditions (e.g. wind speed). Considering the variability of wind conditions throughout the year, the timing of seed release and dispersal is known to have considerable effects on LDD. Even though late phenologies such as ripening duration and timing of seed release and subsequent dispersal are vital in estimating ecologically highly relevant LDD, these phenologies are not appropriately addressed in ecological research. The aim of this thesis is to gain insights into the factors that shape late plant phenologies. In particular, we address the following questions: which ecologically or evolutionary parameters drive the ripening process of plant species? How does the seasonal variability of wind affect the seed release phenology of plant species? How do these factors interact for plant species in different habitat types?
In order to address these questions, we applied different methodological approaches, ranging from fieldwork and monitoring phenology to computational simulation studies and statistical modeling. To study the ripening process of species, we monitored the flowering, ripening and seed release phenology of more than 100 Central European plant species. We conducted computational simulation studies for estimating LDD by wind to study the phenology of seed release and the parameters determining LDD by wind. In conjunction with phenological data from literature, we used the obtained simulation results to investigate evidence for the existence of phenological adaptations towards LDD in 165 plant species. Further, we used the results from simulation studies of LDD by wind to disentangle the effects of species, habitat types and meteorological conditions and their interactions on the spatial spread of plant species.
The results of the relationship between plant traits, phylogeny, the ripening process and climatic factors provide insights into the basic understanding of the ripening process of plants. We identified ecological factors that shape species’ ripening phenology and seed release timing. In particular, we suggest that the species’ seed weight, life form and phylogeny shapes ripening and seed release phenology. With the statistical models on species’ temperature demands for reproduction, we introduce data that that are well suitable for parametrization and further development of plant dispersal models. The results from the simulation study based on a seasonal perspective showed that heavier seeded tree species with medium wind dispersal potential (including genera Abies, Acer, Fraxinus and Larix) have a clear synchronisation of seed abscission with periods favouring LDD. These species, which are both ecologically and economically important, showed significant synchronisation of the highest rate of seed release with high wind-speed that promoted LDD by wind in wintertime. For the tree species mentioned, we suggest strong seasonal synchronisation as evidence for phenological adaptations in order to match favourable conditions during seed release. With a closer look at the wind conditions that promote LDD by wind, our results showed considerable differences in how specific wind conditions affect LDD in different species and habitat types. We suggest that LDD by wind in species from open habitats with high wind dispersal potential is likely to be driven by thermal updrafts that are mainly driven by the sun providing energy to the ground. By contrast, LDD of heavier-seeded species from open and forested habitats is more likely to be driven by storms that produce shear-driven turbulence. The results from this thesis contribute to an increased understanding of the complete dispersal process of plants and to making more realistic projections of (future) plant distribution.
The results obtained on factors driving ripening and release phenology provide valuable insights into their ecological and phylogenetic factor constraints. The implementation of more realistic assumptions in assessing species’ dispersal potential throughout the year could help considerably in improving landscape management (e.g. timing of mowing) and in the conservation of plant populations. The evidence found for phenological adaptations towards LDD in plants is an important step in understanding the evolutionary basis of LDD in these species.
Ischemic injuries of the cardiovascular system are still the leading cause of death worldwide. They are often accompanied by loss of cardiomyocytes (CM) and their replacement by non-functional heart tissue. Cardiac fibroblasts (CF) play a major role in the recovery after ischemic injury and in the scar formation. In the last few years researchers were able to reprogram fibroblasts into CM in vitro and in murine models of myocardial infarction using various protocols including a cocktail of microRNAs (miRs). These miRs can target hundreds of messenger RNAs and inhibit their translation into proteins, potentially regulating multiple cellular signaling pathways. Because of this, there has been a rising interest in the use of miRs for therapeutic purposes. However, as different miRs have different effects in different cells, there is the danger of causing serious side effects. These could be alleviated by enacting a cell-specific transport of miRs, for example by using aptamers. Aptamers are usually short strands of DNA or RNA, which can fold into a specific three-dimensional confirmation which allows them to bind specifically to target molecules. Aptamers are commonly selected from a large library for their ability to bind to target molecules using a procedure called SELEX. Aptamers have already been used to transport miRs into cancer cells.
In this thesis, we first established the transport of miRs into cells of the cardiovascular system using aptamers. MiR-126 is an important part of the signaling in endothelial cells (EC), protects from atherosclerosis and supports angiogenesis, which is why we chose it as a candidate to transport into the vasculature. We first tested two aptamers for their ability to internalize into EC and fibroblasts. Both the aptamer for the ubiquitously expressed transferrin receptor (TRA) and a general internalizing RNA motif, but not a control construct, could internalize efficiently into all cell types tested. We then designed three chimeras (Ch) using different strategies to connect TRA to miR-126. While all chimeras could internalize efficiently, only Ch3, which connects TRA to Pre-miR-126 using a sticky bridge structure, had functional effects in EC. Ch3 reduced the protein expression of VCAM-1 in EC and increased the VEGF induced sprouting of EC in a spheroid-sprouting assay. Treatment of breast cancer cells with Ch3 emulated the effects of treatment with classical miR-126-3p and miR-126-5p mimics. In the SK-BR3 cell line Ch3 and miR-126-3p reduce the viability of the cells while they reduce recruitment of EC by the MCF7 cell line. miR-126-5p had no apparent effect in the SK-BR3 line, but increased viability of MCF7 cells, as did Ch3. This implies that Ch3 can be processed to both functional miR-126-3p and miR-126-5p in treated cells.
We were unable to achieve a reprogramming of adult murine cardiac fibroblasts into cells resembling CM using the cocktail of 4 miRs. This indicates that the miR-mediated transdifferentiation is only possible in neonatal fibroblasts. The effects in mice after an AMI might possibly be caused by an enhanced plasticity of fibroblasts in and close to the infarcted area.
We also screened to find aptamers specifically binding to cells of the cardiovascular system. We used two oligonucleotide libraries in a cell-SELEX to select candidates which bind to CF, but not EC. We observed that only the library which contains two randomized regions of 26 bases showed an enrichment of species binding to fibroblasts. We then sequenced rounds 5-7 of the SELEX and analyzed the data bioinfomatically to select 10 candidate aptamers. All candidates showed a strong binding not only to CF, but also EC. This indicates that the selection pressure against species binding to EC was not high enough and would have to be increased to find true CF-aptamers. Four promising candidates were also analyzed for their potential to be internalized and we surprisingly found that all of them were internalized by EC and CF more efficiently than TRA. The similar behavior of the candidates implies that they possibly share a ligand, which is expressed both by EC and CF, but more prominently by the latter.
This work demonstrates the possibility of using aptamers to transport miRs into cells of the cardiovascular system. It also shows that it is possible to select aptamers for non-cancerous mammalian cells, which has not been done before. It is reasonable to assume that a refinement of the cell-SELEX will allow selection of cell-specific aptamers. Due to the failure of reprogramming of adult fibroblasts into induced cardiomyocytes we were unable to test whether a miR-mediated reprogramming might be inducible using aptamer transported-miRs. Ultimately, aptamer mediated transport of miRs is a feasible and promising therapeutic option for the treatment of cardiovascular diseases and other disorders like cancer.
Reading is an essential ability to master everyday life in our society. The ability to read is based on specific connections between brain regions involved in the reading process – so-called cortical networks for reading. These cortical networks for reading allow us to learn the correct identification of visual words. The use of visual words is based on knowledge about the orthography (lexical) and the meaning of words (semantic). This knowledge must be acquired by beginning readers (first grader), i.e. beginning readers learn in a first step to link letters to a whole word and in a second step associate this whole word with meaning. To retrieve this knowledge during visual word recognition (VWR) a cortical network for lexical-semantic process must be activated. However, it is currently unclear whether beginning readers and reading experts activate the same neuronal network during VWR. Therefore, the aim of this thesis was to investigate the question whether beginning readers (first grader, children) and reading experts (adults) use different cortical networks for the lexical-semantic processing in VWR.
To address this question we recorded electroencephalographic (EEG) activity during VWR in children and adults. Children and adults were instructed to read a visualizable word to compare this word with a following picture stimulus. The first part of this thesis is concerned with the analysis of ERPs for visual word recognition in children and adults at sensor level. For both groups we observed the typical ERP components P100 and N170 for visual word recognition. These components differed in amplitude and time course between both groups. The second part of this thesis investigated the neuronal generators (brain areas) of ERPs during VWR and possible differences between children and adults at source level. We observed a high overlap in brain areas involved during VWR in children and adults. However, the brain areas differed in activation and time course between children and adults. Finally, the third and most important part of the thesis investigated the question whether children and adults use different cortical networks for the lexical-semantic processing in VWR over time. To address this question Dynamic Causal Modeling (DCM) and Bayesian model comparison were used. We compared nine biologically plausible cortical network models underlying the ventral lexical-semantic path in VWR. In addition, increasing time intervals were used to consider possible changes of network structure during VWR. The network models included eight brain regions (four bilateral pairs) involved in the lexical-semantic processing in VWR: occipital cortex (OC), temporo-occipital part of inferior temporal gyrus (ITG), temporal pole (TP), and inferior frontal gyrus (IFG). In almost all time intervals we found evidence that children and adults use the same cortical networks for the lexical-semantic processing in VWR. However, we found differences between adults and children in the connection strengths of the favoured model. Interestingly, we found a stronger direct connection from OC to IFG in adults compared to children.
In conclusion, our results suggest that children and adults activate largely the same lexical-semantic networks during VWR over time. This supports the notion that children and adults use the same biological fiber connections for VWR. However in contrast to children, adults showed increased use of the shortcut pathway from OC to IFG. The increased use of the shortcut pathway from OC to IFG in adults can be interpreted as consequence of learning. Learning causes in accordance with the Hebbian learning rule (“neurons that fire together, wire together” (Hebb, 1949)) synaptic change. Consequently the frequent coactivation of the input and output stage of OC and IFG during the lexical-semantic process facilitates the stronger direct connection between both brain areas. The stronger direct connection from OC to IFG most likely allows adult reading experts to speed up the lexical-semantic process during VWR. Accordingly, we conclude that the stronger direct connections from OC to IFG in adults compared to children underlay the different reading capabilities in both groups.
Termites are important ecosystem engineers of the savanna biome, with the large mounds of fungus-cultivating termites being sources of habitat heterogeneity and structural complexity in African savanna landscapes. Studies from different localities throughout Africa have shown that termite mounds have a strong influence of diversity and composition of plant communities. However, most research has been conducted only at the local scale, and integrating knowledge across Africa is hampered by different methodology of studies and differing environmental context. Little is known about the variation in vegetation composition on termite mounds compared to the surrounding savanna at the regional scale and at the landscape scale, and the main determinants of plant communities on mounds are yet to be ascertained.
This thesis aimes at better understanding the influence of termite mounds on vegetation compared to the surrounding savanna across spatial scales. Three research projects analyse vegetation data and soil data from paired mound and savanna plots in West Africa. The first project examines the influence of termite-induced heterogeneity on plant diversity and vegetation composition at a regional scale, following a bioclimatic gradient from the Sahel of Burkina Faso to the Sudanian vegetation zone in North Benin. The second Project analysed variation of vegetation on and off mounds at the landscape scale in Pendjari National Park, North Benin. The third is a monitoring study over the course of two years, exploring dynamics of juvenile woody plant communities on mounds and in the surrounding savanna at a local scale. The thesis thus provides the first comparative quantitative analysis across scales of mound and savanna vegetation and the drivers of the mound–savanna difference in vegetation.
Synthesizing across scales, its results confirm that termite mounds strongly contribute to savanna plant diversity, even though mounds are not generally more species rich than the surrounding savanna. Variation in mound vegetation is much higher along climatic and soil gradients than previously acknowledged. Mound vegetation differs from the surrounding savanna in the whole study area and in each sampled savanna type, with the strongest differences occurring at the most humid study sites. A large proportion of the differences between mound and savanna vegetation is explained by clay enrichment and related soil factors, such as cation concentrations. Plants on mounds thus benefit from favourable soil conditions, including higher fertility and higher water availability, which is also mirrored by the higher abundance and basal area of juvenile woody plants found on mounds. The variation in mound vegetation between study sites across scales results in part from local differences in soil composition and from climatic differences that influence the regional distribution of species. Different sets of characteristic mound species are identified in each project. Specific plant families and traits like succulency, lianescence, and adaptations to zoochory are found to be overrepresented in mound communities.
In addition to the findings in this thesis, remaining parts of the variation in mound vegetation between study sites could likely be explained by investigating further factors. Specifically, mound vegetation depends on habitat context, which includes available species pools, spatial distribution of mounds, biotic interactions with dispersers and herbivores, fire, and also anthropogenic influence. The high proportion of species with adaptations to zoochory found on mounds, for example, indicates that animal dispersers should be of particular importance for vegetation on termite mounds. Herbivory and fire regime, which are known to contribute to the diversity and community composition of the mound–savanna system, also show strong local variation, not least because of anthropogenic influence.
In conclusion, termite mounds play a crucial role in maintaining heterogeneity and plant diversity in the savanna across scales. Ecosystem services provided by termites, especially considering long-term effects on soil fertility and ecosystem resilience, are most likely undervalued. Mounds should be considered in management plans from local to regional, transnational scales as a matter of course, accompanied by further research on the role of termite mounds in savanna ecology on a longer temporal scale. The research presented here thus provides a basis for future studies on termite mound vegetation that should specifically consider the biotic and abiotic context of the mound–savanna system.
Vascular tumors associated with chronic B. henselae infections are unique examples of infection-associated pathological angiogenesis. The chaotic vascular architecture and prominent myeloid infiltrate of B. henselae induced vascular lesions show many similarities with malignant tumors.
In human cancers infiltrating myeloid cells play a decisive role in tumor progression and vascularization. In particular, tumor associated macrophages (TAMs) transform the tumor microenvironment, drive tumor invasion and vascularization through secretion of pro-angiogenic and immune modulatory cytokines and participation in matrix remodeling processes.
Myeloid angiogenic cells (MACs) are a subset of circulating myeloid progenitors with important roles in regenerative and pathological angiogenesis and a critical involvement in tumor vascularization. The phenotypic plasticity and importance of MACs in pathological angiogenic processes, position these cells as key potential players in B. henselae associated vascular tumor formation.
To investigate the possible role of MACs in B henselae induced pathological angiogenesis, the objective of this study was to examine the interaction of B. henselae with MACs and determine how this may affect their angiogenic capacity.
Building on previous work by Mӓndle (2005) this study has demonstrated that MACs are susceptible to infection with B. henselae and reside in intracellular vacuoles. As in endothelial cells, infection of MACs with B. henselae was associated with inhibition of apoptosis and activation of endogenous angiogenic programs including activation of the angiogenic transcription factor HIF-1.
In addition to angiogenic re-programming on a molecular level B. henselae infection increases MAC functional angiogenic capacity. B. henselae infected MACs were found to integrate into growing endothelium and increase the rate of angiogenic sprouting in a paracrine manner.
When cultured in a Matrigel capillary formation assay, infected MACs were also found to form networks of capillary-like structures that were stable over long periods of time. The B. henselae pathogenicity factor BadA was essential for the induction of this vascular mimicry phenotype as well as the activation of HIF-1 in infected MACs indicating that this factor may play an important role in MAC angiogenic re-programming.
Examination of infected MACs via FACS analysis, cytospin immunohistochemistry and qRT-PCR revealed that endothelial differentiation does not play a role in the B. henselae induced pro-angiogenic phenotype. Instead, MACs were shown to be myeloid in phenotype displaying typical macrophage markers which were upregulated upon B. henselae infection and maintained over long-term culture.
The increased angiogenic activity of B. henselae infected MACs was found to be associated with a broad phenotypic reprogramming in infected cells. In particular, gene expression programs related to angiogenesis, structural organization, apoptosis, sterol metabolism and immune regulation, were upregulated. Further examination of microarray gene expression profiles revealed that B. henselae infected MACs display a predominantly M2 anti-inflammatory macrophage activation status.
Finally, examination of the paracrine microenvironment created by B. henselae infected MACs revealed a diverse cytokine secretion profile dominated by inflammatory-angiogenic cytokines and matrix remodeling elements and lacking expression of some of the most important cytokines involved in the expansion of the inflammatory response. This B. henselae induced activation status was demonstrated to be distinct from the general inflammatory response induced by E. coli LPS treatment.
Comparison of B. henselae infected MACs to TAMs revealed many parallels in functional and phenotypic characteristics. Both TAMs and B. henselae infected MACs demonstrate increased angiogenic capacity, invasive, and immune modulatory phenotypes and the ability to participate in the formation of vascular mimicry phenotypes under angiogenic pressure. Furthermore, the pro-angiogenic paracrine microenvironment created by B. henselae infected MACs shows many similarities to the TAM-created tumor-microenvironment.
In conclusion, these investigations have demonstrated that the infection of MACs with B. henselae results in the phenotypic re-programming towards TAM-like cells with increased pro-angiogenic, invasive and immune-modulatory qualities. The results of this study elucidate new aspects of B. henselae pathogenicity in myeloid cells and highlight the role of these cells as paracrine mediators of B. henselae induced vascular tumor formation. In addition, these findings demonstrate that manipulation of myeloid cells by pathogenic bacteria can contribute to microenvironmental regulation of pathological tissue growth and suggest parallels underlying bacterial infections and cancer.
The brain vascular system is composed of specialized endothelial cells, which regulate the movement of ions, molecules and cells from the blood lumen to the central nervous system (CNS). Endothelial cells in the brain form the blood-brain barrier (BBB) that is essential to maintain the brain homeostasis and protect the CNS from pathogens and toxins for a proper neurological function. Endothelium together with other cellular components such as pericytes, astrocytes and the basement membrane, forms the neurovascular unit (NVU), the structural unit of the BBB. Breakdown of the BBB occurs in various neurological disorders, leading to edema and neuronal damage. Therapeutic strategies focusing on factors that regulate the permeability of the BBB may help to improve neurological disorders and facilitate drug delivery to the brain.
Angiopoietins (Ang) are potential candidates for therapeutic targeting the BBB due to their role in regulating the vascular permeability in periphery. They are key growth factors that control angiogenesis and vessel maturation. Ang-1 and Ang-2 possess similar binding affinities to the Tie2 receptor tyrosine kinase, which is almost exclusively expressed on endothelial cells. Ang-1 is expressed in smooth muscle cells and pericytes, and binds in a paracrine manner to Tie2. This results in phosphorylation of the receptor and induction of downstream signaling pathways leading to vessel maturation via pericyte recruitment and blood vessel stabilization. Ang-2, on the other hand, is stored in Weibel Palade bodies in endothelial cells and is released upon inflammatory or angiogenic stimuli. Therefore, in mature, stabilized blood vessels, Ang-2 expression is low. Increased level of Ang-2 is only observed during development or in pathology such as ischemia, cancer and inflammation. When Ang-2 is released, it acts in an autocrine manner and interferes with Tie2 phosphorylation in a context-dependent way. Antagonizing the receptor results in de-stabilization of the vessels, often accompanied by reduced numbers of pericytes leading to myeloid cell infiltration. In conjunction with the vascular endothelial growth factor (VEGF), Ang-2 contributes to blood vessel sprouting, whereupon in absence of VEGF it promotes vessel regression. ...
Cyanobacteria belong to the most widely distributed microorganisms in the biosphere and contribute significantly to global primary production. Their metabolism is based on oxygenic photosynthesis and some cyanobacteria can fix elemental nitrogen. Obligate photosynthetic diazotrophs have a particularly high iron demand in comparison to heterotrophic bacteria. Nevertheless the understanding of iron acquisition in cyanobacteria is just beginning to emerge. Iron acquisition in bacteria comprises highly specific transport of siderophore-iron complexes over the outer membrane by TonB-dependent transporter (TBDT). The transport itself is active and energized by a multi-complex localized to the inner membrane termed the TonB-system (TonB-ExbB-ExbD). The siderophore-iron complexes are further transported into the cytosol by a binding protein dependent ABC-transporter. Cyanobacterial iron acquisition response has most extensively been studied in unicellular, non-siderophore synthesizing cyanobacteria in the genus Synechococcus and Synechocystis. Anabaena sp. PCC 7120, however, is a different model organism as it is a freshwater living, siderophore synthesizing and, truly multicellular microorganism. It can be assumed that siderophore synthesis and siderophore-dependent iron uptake are tightly coordinated processes, therefore Anabaena represents a different model organism as compared to non-siderophore producing cyanobacteria. Moreover the surprisingly abundant protein family of 22 putative TBDTs in Anabaena indicates a high complexity of TonB-dependent uptake systems. Sequence similarity analysis revealed 4 putative tonB encoding genes (alr0248, all3585, all5036, alr5329), 2 putative exbB-exbD encoding gene cluster (alr0643-alr0644, all5047-all5046), one single standing putative exbB encoding gene (alr4587) and several hypothetical binding-protein-dependent ATP binding cassette (ABC)-type transporter encoding genes (fhu-, fec- and fut-type transporter).
In this study the respond of the predeicted systems to iron-limiting conditions was analysed by qRT-PCR. The expression analysis revealed on the one hand an enhanced transcription of all5036 (tonB3), all5047-all5046 (exbB3-exbD3) and the fhu-like encoding genes (all0387-all0389) under iron-limitation and at the same time down-regulation of expression under enhanced iron concentrations. Summerizing the transcription profile of the tonB3- and the fhu-system showed an expression regulated by iron-availability. To further characterize the role of TonB3-, ExbB3- and the Fhu-system, mutants thereof were generated. None of the generated mutants, except for the exbB3 mutant, could be fully segregated, suggesting an essential character of the genes. Characterization of the mutants revealed enhanced expression of iron-starvatrion indicator genes (isiA, fhuA) and altered growth of the tonB3 mutant under iron-limiting conditions. The iron starvation phenotype was further strengthened by enhanced siderophore secretion in the tonB3, exbB3 and fhuC mutants. Taken as a whole the results strongly indicate involvement of the tonB3- and the fhu-system in siderophore-dependnet iron uptake in Anabaena.
Investigation of the tonB2 (all3585) mutant under iron and citric acid limitation resultated in altered growth of the mutant. However, growth could be restored by addition of iron chlorid. Therefore a connection of the TonB2 protein to iron uptake is implied and further supported by ressitance to toxic iron concentrations. Lastly, mutation of tonB1 (alr0248) reuslted in insensibility to toxic manganese and copper concentrations and macrolid antibiotics. The altered permeability of the outer membrane may be a result of decreased expression of seven putative porin encoding genes in the mutant. A possible role in transcriptional regulation of porin expression is discussed.
Snake bite envenoming often results in disability or death of breadwinners of poor families in the rural tropics and the subtropics of Nepal. Identification of the medically relevant snake species, circumstances of venomous snake bites, prehospital care of their bites and human responses to snakes and snake bite is, therefore, crucial to enable victims or first aider to select the appropriate first aid measures, physicians to anticipate complications and to use appropriate treatment protocols as well as the local community to implement prevention strategies. Inadequate educational gaps exist in Nepal and hinder identification of snakes involved in bites. To fill this gap, I aim to provide an evidence-based list of medically relevant snake species. Snake specimens brought by patients bitten or their attendants from the tropical and subtropical regions in southeastern, southcentral, and southwestern Nepal to snake bite treatment centres over a period from 2010 through 2014, were taxonomically identified and medical records of envenoming were evaluated.
In Nepal, the epidemiology of snake bite is poorly known. Here I describe the ecological circumstances of proven krait (Bungarus spp.) and Russell´s Viper (Daboia russelii) bites to elucidate and examine, whether environmental circumstances or human behaviour contributed to envenoming. In a cross-sectional study, data about prehospital care, environmental circumstances of 46 krait and 10 Russell´s Viper bites were evaluated. Patients were interviewed using structured interview forms. Snake bite prone communities were surveyed to test people´s knowledge on snakes and their attitude towards venomous snakes in general.
Of 349 snakes involved in bites, 199 (57%) specimens were found to be medically relevant venomous snakes that included 11 species belonging to six genera and two families. Among them, Naja naja (n = 76, 22%), Bungarus caeruleus (n = 65, 19%) and Trimeresusurs albolabris (n = 10, 3%) were the most widely distributed snakes. Daboia russelii (n = 10, 3%) was found to be restricted to the southwestern part of Nepal. For B. walli, a previously poorly known species, 13 voucher specimens represent the first country records of this species as well as the first documented cases of involvement in snake bite envenoming by this species in Nepal.
Numerous snake bites (33%) occurred at night, during the rainy season, and are mainly due to Bungarus species, particularly B. caeruleus. Bites of cobras and Russell’s Vipers are a risk at daytime. Evaluation of data regarding the place where the bite happened, indicates that the snake bite risks appear to be as high in residential areas, in and around houses, as in rural areas. In cases of kraits (n = 46), 61% of the bites occurred while the victim was sleeping indoors, those of Russell´s Vipers mainly during agricultural activities in the fields. Analysis of socio-demographic data revealed that both krait and viper bites predominantly affected farmers or their family members. However, snake bites involved also people of higher socio-economic status, which suggests that it is not a health problem of poor people only living in the rural areas of Nepal.
A small number of snake bite victims (n = 7) sought help from traditional healers, but most patients went to hospitals for medical treatment using motorbikes (65%) or were transferred by ambulance cars (22%). As a first aid measure, most patients (78%) had used a tourniquet, which is of doubtful value and has often severe sequelae, instead of applying the WHO recommended pressure immobilisation bandage or local compression pad. The overall case fatality rate was calculated to be 10%, but up to 17% in cases of Bungarus spp. bites.
Rural community people were found to be extremely afraid of snakes, a major reason for indiscriminate killing of even harmless snakes, e.g., Lycodon aulicus, which were wrongly considered to be venomous. This is mainly due to the poor knowledge on snakes in general and on their role in providing ecological services, which may eventually lead to a decline in snake populations and even the extinction of rare species.
The results of the present study strongly emphasize that snake bite is an important public health issue in Nepal. There is an urgent need to improve the knowledge of people on snakes and to try changing their attitudes towards these reptiles, in addition to documenting the biodiversity and distribution of medically relevant snakes, the epidemiology and circumstances of their bites. Avoiding high-risk behaviour (e.g., killing of snakes), using screened doors and windows are some of the suggested measures preventing snake bite. Early and accurate identification of the snakes involved should help physicians to apply timely treatment, eventually referring the patient to the appropriate hospital. This also has important implications in developing public health and conservation strategies, to the benefit of the people of Nepal.
Die Parkinson Erkrankung ist die zweithäufigste neurodegenerative Erkrankung in industrialisierten Ländern. Die charakteristischen Symptome sind schwere Beeinträchtigungen des Bewegungsablaufes welche auf den Verlust dopaminerger Neurone der Substantia nigra und der damit einhergehenden Reduktion des striatalen Dopamin Gehaltes zurückzuführen sind. Alpha-Synuklein (SNCA) ist ein Protein welches zum einen mit sporadischen aber auch mit idiopathischen Erkrankungen assoziiert ist. Mutationen welche einen Funktionsgewinn von SNCA zur Folge haben konnten mit autosomal dominanten Varianten der Parkinson Erkrankung assoziiert werden und genetische Veränderungen an beiden Genenden agieren als Risikofaktor für sporadische Formen der Erkrankung. Des Weiteren wird SNCA als Hauptbestandteil der Lewy Körperchen gefunden, einem pathologischen Kennzeichen der parkinsonschen Erkrankung. Die charakteristischen Bewegungsstörungen können mittels L-DOPA, einer metabolischen Vorstufe von Dopamin, behandelt werden. Neben dem enorm positiven Effekt auf die Bewegungsstörungen, geht die Behandlung mit L-DOPA jedoch auch mit ernsten Nebenwirkungen einher, welche als Levodopa induzierte Dyskinesien (LID) beschrieben werden.
Ziel der Arbeit war die Analyse von Effekten eines SNCA Funktionsgewinns sowie des Pink1 Funktionsverlustes auf molekulare Signalwege der synaptischen Plastizität unter Verwendung dreier PD Mausmodelle (A53T-SNCA überexprimierendes Modell (PrPmtA), Pink1KO Modell sowie A53T-SNCA + Pink1KO Doppelmutante (DM)). Es wurden Kandidatengene welche eine Rolle für synaptische Plastizität spielen in 6 Monate alten Mäusen aller drei PD Mauslinien untersucht. Die Analyse von PrPmtA zeigte erhöhte mRNA Spiegel von Glutamatrezeptor-Untereinheiten und von Kandidatengenen welche eine Rolle bei der synaptischen Signalweiterleitung spielen, sowie reduzierte mRNA Spiegel von IEGs und Transkriptionsfaktoren. Die Analyse der DM zeigte nur geringe Expressionsänderungen der Glutamatrezeptor-Untereinheiten und die Analyse von IEGs und Transkriptionsfaktoren zeigte erneut reduziert mRNA Spiege. In Pink1KO Tieren konnten nur minimale Expressionsveränderungen der Kandidatengene gefunden werden, was den Schluss zulässt, dass die zuvor beschriebenen Expressionsveränderungen in PrPmtA und DM Mäusen eindeutig auf den SNCA Funktionsgewinn zurückzuführen sind. Um frühe Effekte des SNCA Funktionsgewinns zu studieren wurde die Analyse auf 3 Monate alte PrPmtA Mäuse ausgeweitet. Diese ergab, Expressionsveränderungen für Homer1, cFos, NOR1, Nurr1 und Nur77.
In einem weiteren Versuchsansatz wurde die Auswirkung des SNCA Funktionsgewinns auf das Verhalten sowie auf molekulare Parameter nach Apomorphin Behandlung analysiert. Die Analyse ergab ein erhöhtes Niveau an unwillkürlichen Bewegungsmustern mit stereotypen und dystonischen Eigenschaften in PrPmtA im Vergleich zu Wildtypen (wt). Die molekulare Analyse von striatalem Gewebe wurde zu zwei Zeitpunkten durchgeführt, 30 min nach Apomorphin Injektion und 100 min nach Injektion. Die Analyse von striatalem Gewebe welches zum Zeitpunkt 30 min nach Injektion entnommen wurde ergab eine erhöhte Apomorphin abhängige Phosphorylierung von ERK1/2, sowie eine erhöhte Apomorphin abhängige Expression von Dusp1, Dusp6 und cFos in transgenen und wt Tieren. Genotyp abhängige Unterschiede ergaben sich für cFos, welches signifikant höher in PrPmtA induziert wurde. 100 min nach Apomorphin Injektion ergab die gleiche Analyse eine erhöhte Apomorphin abhängige Phosphorylierung von ERK1 und eine erhöhte Apomorphin abhängige Expression von Dusp1, Dusp6, cFos und Nur77 in PrPmtA im Vergleich zu wt. Die Daten unterstreichen die fundamentale Rolle von SNCA auf die Neurotransmission und synaptische Plastizität und zeigen auf, dass PrPmtA ein zuverlässiges Modell für die Analyse von präsynaptischer Dysfunktion in Frühstadien der Parkinson Erkrankung darstellt.
Der letzte Versuchsansatz stellt die Charakterisierung des DM-Mausmodells welches sich durch einen starken Phänotyp auszeichnet, sowie die Analyse des Pink1 Effektes auf die SNCA induzierte Neurotoxizität dar. DM-Tiere zeigen deutlich reduzierte Spontanmotorik im Alter von 3 Monaten sowie einer progressiven Lähmung der Hinterläufe, was Anlass zu einer immunhistologischen Charakterisierung mittels Schnitten des Gehirns und Rückenmarks gab. Die histologische Analyse zeigte pSer129-SNCA, p62/SQSTM1 und Ubiquitin positive Aggregate innerhalb der grauen Substanz des Rückenmarks sowie innerhalb einer neuronalen Zellpopulation welche dorsal der Substantia nigra angeordnet ist. Das histologische Erscheinungsbild wurde spezifisch in gelähmten DM-Tieren gefunden und nicht in Einzelmutanten oder DM-Tieren ohne Lähmung. Dieses Modell stellt ein wertvolles Instrument für die Identifizierung von pathologischen Mechanismen und Signalkaskaden welche beiden Parkinson relevanten Genen gemeinsam sind, dar.
Die vorliegende Dissertation mit dem Titel: Ecophysiological monitoring of Oaks in Central Europe, introduced in the framework of proactive climate change mitigation beschäftigt sich mit der Anwendung zerstörungsfreier, radiometrischer Methoden zur Bestimmung von Pigment- und Stickstoffkonzentrationen und der photosynthetischen Funktionalität in Blättern von heimischen und gebietsfremden Eichen und ihre Beeinflussung durch Trocken-, Hitze- und Kältestress.
Die Eichenarten Quercus robur L. (Stieleiche), Q. pubescens Willd. (Flaumeiche), Q. frainetto Ten. (Ungarische Eiche), Q. ilex L. (immergrüne Steineiche) und Q. rubra L. (amerikanische Roteiche) wurden im Frühjahr 2011 auf einer Versuchsfläche im Frankfurter Stadtwald gepflanzt, um ihre Nutzung als potentielle Waldbäume in einem sich ändernden Klima zu untersuchen. Über eine Dauer von zwei Jahren wurden diese Arten mit einem hohen Maß an blattspezifischer Merkmalsvariabilität beobachtet und beprobt. Ziel war es, die interspezifischen Unterschiede und die jahreszeitliche Dynamik von morphologischen und chemischen Blattmerkmalen sowie die Beeinflussung der radiometrischen Bestimmung des Chlorophyllgehaltes (und damit assoziierten Komponenten wie z.B. Blattstickstoffgehalt und Karotinoiden) und der photosynthetischen Funktionalität durch klimatische Umweltbelastungen in Eichen zu untersuchen. Die Analyse der Blattproben zielte neben der Bestimmung der Beziehung zwischen absoluten und optisch ermittelten Pigmentgehalten auf die Ermittlung des Einflusses der Blattstruktur auf die Lichttransmission im roten und infrarotem Bereich des Elektromagnetischen Spektrums ab, sowie auf die artspezifische Korrelation von Blattstickstoff zu Blattchlorophyll zu dessen indirekte Quantifizierung. Des Weiteren wurden Versuche zur Trocken- und Hitzestressanpassung durchgeführt, um eine potentiell artspezifische Stressantwort, sowie eine mögliche Beeinflussung der aufgenommenen radiometrischen Messwerte zu ermitteln. Ein zusätzliches Monitoringprogramm im Winter 2012/2013 mit einer Dauer von sechs Monaten ermöglichte die Überprüfung der Anpassungsfähigkeit der immergrünen Steineiche (Q. ilex) an mitteleuropäische Winterbedingungen und die Veränderung der photosynthetischen Funktionalität unter Kältestress. Messungen im Zusammenhang mit der praktischen Anwendbarkeit der zerstörungsfreien, optischen Methode und zur Bereitstellung von Referenzdaten für zukünftige Evaluierungen komplementieren die Untersuchungen.
Signifikante, artspezifische Unterschiede wurden in den blattmorphologischen Schlüsselmerkmalen in den Quercus-Arten ermittelt. Die artspezifischen Unterschiede in den morphologischen Blattmerkmalen beeinflussten auf signifikante Weise die Beziehung zwischen absoluten, massebasierten Pigment- und Stickstoffgehalten und deren radiometrischen Bestimmung. Wurden die Pigmentgehalte hingegen auf die Blattfläche bezogen und die Stickstoffgehalte mittels des Verhältnisses von Blattfläche zu Trockenmasse korrigiert, zeichnete sich eine Beziehung zwischen absoluten und optisch ermittelten Werten ab, der jegliche jahreszeitliche oder artspezifisch morphologische Variabilität fehlte und die somit für alle Quercus-taxa anwendbar ist. Koeffizienten für die Berechnung von flächenbezogenen Gehalten von Gesamtchlorophyll, Chl a, Chl b und Carotinoiden für die jeweiligen Quercus-taxa, wie auch für ein artübergreifendes Modell wurden ermittelt, um die Bestimmung dieser Gehalte während aller Entwicklungsstufen zu ermöglich. Aus der jahreszeitlichen Entwicklung der Pigmentgehalte konnten drei deutliche Phasen abgeleitet werden: Die Phase der Blattentwicklung im Frühling, einer Plateauphase mit geringen Veränderungen (“core vegetation time”) und die Phase des Pigmentabbaus während der Herbstlaubfärbung. Die Übergänge zwischen diesen Phasen variierten zum Teil erheblich zwischen einzelnen Individuen einer Art sowie zwischen den Arten, was Unterschiede in der potentiellen, jährlichen Kohlenstoffaufnahme nach sich zieht. Stressbedingungen, wie Hitze- Kälte- oder Trockenstress, können zu Veränderung von Fluoreszenzparametern ohne gleichzeitige Änderung des Pigmentgehaltes führen, wie auch die indirekte Bestimmung von mit Chl assoziierten Komponenten (Carotinoide, Chl a, Chl b) mittels optischer Bestimmung (durch die Veränderungen von Pigmentverhältnissen) beeinflussen.
Im Rahmen des Forschungsprojektes konnten, Modelle zur Berechnung von Blattpigmenten und Blattstickstoff aus optischem Messdaten, Veränderungen der photosynthetischen Funktionalität, sowie Referenzdaten für die zukünftig nutzbaren Eichenarten hinsichtlich artspezifischer und jahreszeitlicher Variabilität unter mitteleuropäischen Umweltbedingungen ermittelt werden, die eine Nutzung und Einordnung von zerstörungsfreien, optischen Messwerten zur Ermittlung von Vitalitätsunterschieden in Eichen ermöglichen.