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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
211

Silicon availability modifies nutrient use efficiency and content, C:N:P stoichiometry, and productivity of winter wheat (Triticum aestivum L.)

Neu, Silke, Schaller, Jörg, Dudel, E. Gert 28 March 2017 (has links)
Silicon (Si) is known as beneficial element for graminaceous plants. The importance of Si for plant functioning of cereals was recently emphasized. However, about the effect of Si availability on biomass production, grain yield, nutrient status and nutrient use efficiency for wheat (Triticum aestivum L.), as one of the most important crop plants worldwide, less is known so far. Consequently, we assessed the effect of a broad range of supply levels of amorphous SiO2 on wheat plant performance. Our results revealed that Si is readily taken up and accumulated basically in aboveground vegetative organs. Carbon (C) and phosphorus (P) status of plants were altered in response to varying Si supply. In bulk straw biomass C concentration decreased with increasing Si supply, while P concentration increased from slight limitation towards optimal nutrition. Thereby, aboveground biomass production increased at low to medium supply levels of silica whereas grain yield increased at medium supply level only. Nutrient use efficiency was improved by Si insofar that biomass production was enhanced at constant nitrogen (N) status of substrate and plants. Consequently, our findings imply fundamental influences of Si on C turnover, P availability and nitrogen use efficiency for wheat as a major staple crop.
212

Brain-Derived Neurotrophic Factor (Val66Met) and Serotonin Transporter (5-HTTLPR) Polymorphisms Modulate Plasticity in Inhibitory Control Performance Over Time but Independent of Inhibitory Control Training

Enge, Sören, Fleischhauer, Monika, Gärtner, Anne, Reif, Andreas, Lesch, Klaus-Peter, Kliegel, Matthias, Strobel, Alexander 31 March 2017 (has links)
Several studies reported training-induced improvements in executive function tasks and also observed transfer to untrained tasks. However, the results are mixed and there is a large interindividual variability within and across studies. Given that training-related performance changes would require modification, growth or differentiation at the cellular and synaptic level in the brain, research on critical moderators of brain plasticity potentially explaining such changes is needed. In the present study, a pre-post-follow-up design (N = 122) and a 3-weeks training of two response inhibition tasks (Go/NoGo and Stop-Signal) was employed and genetic variation (Val66Met) in the brain-derived neurotrophic factor (BDNF) promoting differentiation and activity-dependent synaptic plasticity was examined. Because Serotonin (5-HT) signaling and the interplay of BDNF and 5-HT are known to critically mediate brain plasticity, genetic variation in the 5-HTT gene-linked polymorphic region (5-HTTLPR) was also addressed. The overall results show that the kind of training (i.e., adaptive vs. non-adaptive) did not evoke genotype-dependent differences. However, in the Go/NoGo task, better inhibition performance (lower commission errors) were observed for BDNF Val/Val genotype carriers compared to Met-allele ones supporting similar findings from other cognitive tasks. Additionally, a gene-gene interaction suggests a more impulsive response pattern (faster responses accompanied by higher commission error rates) in homozygous l-allele carriers relative to those with the s-allele of 5-HTTLPR. This, however, is true only in the presence of the Met-allele of BDNF, while the Val/Val genotype seems to compensate for such non-adaptive responding. Intriguingly, similar results were obtained for the Stop-Signal task. Here, differences emerged at post-testing, while no differences were observed at T1. In sum, although no genotype-dependent differences between the relevant training groups emerged suggesting no changes in the trained inhibition function, the observed genotype-dependent performance changes from pre- to post measurement may reflect rapid learning or memory effects linked to BDNF and 5-HTTLPR. In line with ample evidence on BDNF and BDNF-5-HT system interactions to induce (rapid) plasticity especially in hippocampal regions and in response to environmental demands, the findings may reflect genotype-dependent differences in the acquisition and consolidation of task-relevant information, thereby facilitating a more adaptive responding to task-specific requirements.
213

Work-related exposures and disorders among physical therapists: experiences and beliefs of professional representatives assessed using a qualitative approach

Girbig, Maria, Freiberg, Alice, Deckert, Stefanie, Druschke, Diana, Kopkow, Christian, Nienhaus, Albert, Seidler, Andreas 31 March 2017 (has links)
Background According to international study results, physical therapists are afflicted with work-related musculoskeletal, psychosocial and dermal disorders as well as infections. The few existing studies in German-speaking regions focus mainly on dermal and psychosocial exposures and resulting complaints. An overview of all relevant work-related exposures and complaints of physical therapists is currently lacking. We sought to identify work-related exposures based on the subjective experiences and beliefs of physiotherapeutic representatives, in order to identify relevant work-related complaints and diseases. Likewise we aimed to compare the international evidence with the actual situation of physical therapists in Germany. Methods Two complementary qualitative approaches were used: 1) a focus group discussion with representatives of professional physiotherapy associations as well as health and safety stakeholders and 2) qualitative semi-structured telephone interviews incorporating currently employed physical therapists. The group discussion was conducted applying a moderation technique, and interviews were analyzed using the content analysis approach by Mayring. Results The focus group discussion with five participants and the 40 semi-structured interviews with physical therapists identified comparable results. The main exposures of physiotherapeutic work were considered to be musculoskeletal (e.g., awkward body postures during treatment, patient transfers, passive mobilization), psychosocial (e.g., statutory audit of prescriptions and the associated conflicts with doctors and health insurance providers) and partly dermal and infectious (e.g., wet work and risk of infection) factors. Diseases of the spine, wrist or finger joints, burnout syndrome and infections were mentioned as possible consequences. Conclusions The subjective data generated by both groups (focus group discussion and interviews) were comparable and consistent with the current state of research. The results provide new insight regarding work-related exposures and diseases of physical therapists working in Germany. These findings aided the design of a German-wide representative survey of practicing physical therapists.
214

A peroxygenase from Chaetomium globosum catalyzes the selective oxygenation of testosterone

Kiebist, Jan, Schmidtke, Kai-Uwe, Zimmermann, Jörg, Kellner, Harald, Jehmlich, Nico, Ullrich, René, Zänder, Daniel, Hofrichter, Martin, Scheibner, Katrin 03 April 2017 (has links)
Unspecific peroxygenases (UPO, EC 1.11.2.1) secreted by fungi open an efficient way to selectively oxyfunctionalize diverse organic substrates, including less-activated hydrocarbons, by transferring peroxide-borne oxygen. We investigated a cell-free approach to incorporate epoxy and hydroxyl functionalities directly into the bulky molecule testosterone by a novel unspecific peroxygenase (UPO) that is produced by the ascomycetous fungus Chaetomium globosum in a complex medium rich in carbon and nitrogen. Purification by fast protein liquid chromatography revealed two enzyme fractions with the same molecular mass (36 kDa) and with specific activity of 4.4 to 12 U mg−1. Although the well-known UPOs of Agrocybe aegerita (AaeUPO) and Marasmius rotula (MroUPO) failed to convert testosterone in a comparative study, the UPO of C. globosum (CglUPO) accepted testosterone as substrate and converted it with total turnover number (TTN) of up to 7000 into two oxygenated products: the 4,5-epoxide of testosterone in β-configuration and 16α-hydroxytestosterone. The reaction performed on a 100 mg scale resulted in the formation of about 90 % of the epoxide and 10 % of the hydroxylation product, both of which could be isolated with purities above 96 %. Thus, CglUPO is a promising biocatalyst for the oxyfunctionalization of bulky steroids and it will be a useful tool for the synthesis of pharmaceutically relevant steroidal molecules.
215

Diabetes-linked transcription factor HNF4α regulates metabolism of endogenous methylarginines and β-aminoisobutyric acid by controlling expression of alanine-glyoxylate aminotransferase 2

Burdin, Dmitry V., Kolobov, Alexey A., Brocker, Chad, Soshnev, Alexey A., Samusik, Nikolay, Demyanov, Anton v., Brilloff, Silke, Jarzebska, Natalia, Martens-Lobenhoffer, Jens, Mieth, Maren, Maas, Renke, Bornstein, Stefan R., Bode-Böger, Stefanie M., Gonzalez, Frank, Weiss, Norbert, Rodionov, Roman N. 21 July 2017 (has links)
Elevated levels of circulating asymmetric and symmetric dimethylarginines (ADMA and SDMA) predict and potentially contribute to end organ damage in cardiovascular diseases. Alanine-glyoxylate aminotransferase 2 (AGXT2) regulates systemic levels of ADMA and SDMA, and also of beta-aminoisobutyric acid (BAIB)-a modulator of lipid metabolism. We identified a putative binding site for hepatic nuclear factor 4 α (HNF4α) in AGXT2 promoter sequence. In a luciferase reporter assay we found a 75% decrease in activity of Agxt2 core promoter after disruption of the HNF4α binding site. Direct binding of HNF4α to Agxt2 promoter was confirmed by chromatin immunoprecipitation assay. siRNA-mediated knockdown of Hnf4a led to an almost 50% reduction in Agxt2 mRNA levels in Hepa 1–6 cells. Liver-specific Hnf4a knockout mice exhibited a 90% decrease in liver Agxt2 expression and activity, and elevated plasma levels of ADMA, SDMA and BAIB, compared to wild-type littermates. Thus we identified HNF4α as a major regulator of Agxt2 expression. Considering a strong association between human HNF4A polymorphisms and increased risk of type 2 diabetes our current findings suggest that downregulation of AGXT2 and subsequent impairment in metabolism of dimethylarginines and BAIB caused by HNF4α deficiency might contribute to development of cardiovascular complications in diabetic patients.
216

New determinants of olfactory habituation

Sinding, Charlotte, Valadier, François, Al-Hassani, Viviana, Feron, Gilles, Tromelin, Anne, Kontaris, Ioannis, Hummel, Thomas 27 July 2017 (has links)
Habituation is a filter that optimizes the processing of information by our brain in all sensory modalities. It results in an unconscious reduced responsiveness to continuous or repetitive stimulation. In olfaction, the main question is whether habituation works the same way for any odorant or whether we habituate differently to each odorant? In particular, whether chemical, physical or perceptual cues can limit or increase habituation. To test this, the odour intensity of 32 odorants differing in physicochemical characteristics was rated by 58 participants continuously during 120s. Each odorant was delivered at a constant concentration. Results showed odorants differed significantly in habituation, highlighting the multifactoriality of habituation. Additionally habituation was predicted from 15 physico-chemical and perceptual characteristics of the odorants. The analysis highlighted the importance of trigeminality which is highly correlated to intensity and pleasantness. The vapour pressure, the molecular weight, the Odor Activity Value (OAV) and the number of double bonds mostly contributed to the modulation of habituation. Moreover, length of the carbon chain, number of conformers and hydrophobicity contributed to a lesser extent to the modulation of habituation. These results highlight new principles involved in the fundamental process of habituation, notably trigeminality and the physicochemical characteristics associated.
217

Clinical impact of duodenal pancreatic heterotopia – Is there a need for surgical treatment?

Betzler, Alexander, Mees, Soeren Torge, Pump, Josefine, Schölch, Sebastian, Zimmermann, Carolin, Aust, Daniela E., Weitz, Jürgen, Welsch, Thilo, Distler, Marius 27 July 2017 (has links)
Background Pancreatic heterotopia (PH) is defined as ectopic pancreatic tissue outside the normal pancreas and its vasculature and duct system. Most frequently, PH is detected incidentally by histopathological examination. The aim of the present study was to analyze a large single-center series of duodenal PH with respect to the clinical presentation. Methods A prospective pancreatic database was retrospectively analyzed for cases of PH of the duodenum. All pancreatic and duodenal resections performed between January 2000 and October 2015 were included and screened for histopathologically proven duodenal PH. PH was classified according to Heinrich’s classification (Type I acini, ducts, and islet cells; Type II acini and ducts; Type III only ducts). Results A total of 1274 pancreatic and duodenal resections were performed within the study period, and 67 cases of PH (5.3%) were identified. The respective patients were predominantly male (72%) and either underwent pancreatoduodenectomy (n = 60); a limited pancreas resection with partial duodenal resection (n = 4); distal pancreatectomy with partial duodenal resection (n = 1); total pancreatectomy (n = 1); or enucleation (n = 1). Whereas 65 patients (83.5%) were asymptomatic, 11 patients (18.4%) presented with symptoms related to PH (most frequently with abdominal pain [72%] and duodenal obstruction [55%]). Of those, seven patients (63.6%) had chronic pancreatitis in the heterotopic pancreas. The risk of malignant transformation into adenocarcinoma was 2.9%. Conclusions PH is found in approximately 5% of pancreatic or duodenal resections and is generally asymptomatic. Chronic pancreatitis is not uncommon in heterotopic pancreatic tissue, and even there is a risk of malignant transformation. PH should be considered for the differential diagnosis of duodenal lesions and surgery should be considered, especially in symptomatic cases.
218

Response inhibition in Attention deficit disorder and neurofibromatosis type 1 – clinically similar, neurophysiologically different

Bluschke, Annet, von der Hagen, Maja, Papenhagen, Katharina, Roessner, Veit, Beste, Christian 15 November 2017 (has links)
There are large overlaps in cognitive deficits occurring in attention deficit disorder (ADD) and neurodevelopmental disorders like neurofibromatosis type 1 (NF1). This overlap is mostly based on clinical measures and not on in-depth analyses of neuronal mechanisms. However, the consideration of such neuronal underpinnings is crucial when aiming to integrate measures that can lead to a better understanding of the underlying mechanisms. Inhibitory control deficits, for example, are a hallmark in ADD, but it is unclear how far there are similar deficits in NF1. We thus compared adolescent ADD and NF1 patients to healthy controls in a Go/Nogo task using behavioural and neurophysiological measures. Clinical measures of ADD-symptoms were not different between ADD and NF1. Only patients with ADD showed increased Nogo errors and reductions in components reflecting response inhibition (i.e. Nogo-P3). Early perceptual processes (P1) were changed in ADD and NF1. Clinically, patients with ADD and NF1 thus show strong similarities. This is not the case in regard to underlying cognitive control processes. This shows that in-depth analyses of neurophysiological processes are needed to determine whether the overlap between ADD and NF1 is as strong as assumed and to develop appropriate treatment strategies.
219

Impacts of a capillary barrier on infiltration and subsurface stormflow in layered slope deposits monitored with 3-D ERT and hydrometric measurements

Hübner, Rico, Günther, Thomas, Heller, Katja, Noell, Ursula, Kleber, Arno 09 November 2017 (has links)
Identifying principles of water movement in the shallow subsurface is crucial for adequate process-based hydrological models. Hillslopes are the essential interface for water movement in catchments. The shallow subsurface on slopes typically consists of different layers with varying characteristics. The aim of this study was to draw conclusions about the infiltration behaviour, to identify water flow pathways and derive some general interpretations for the validity of the water movement on a hillslope with periglacial slope deposits (cover beds), where the layers differ in their sedimentological and hydrological properties. Especially the described varying influence of the basal layer (LB) as an impeding layer on the one hand and as a remarkable pathway for rapid subsurface stormflow on the other. We used a time lapse 3-D electrical resistivity tomography (ERT) approach combined with punctual hydrometric data to trace the spreading and the progression of an irrigation plume in layered slope deposits during two irrigation experiments. This multi-technical approach enables us to connect the high spatial resolution of the 3-D ERT with the high temporal resolution of the hydrometric devices. Infiltration through the uppermost layer was dominated by preferential flow, whereas the water flow in the deeper layers was mainly matrix flow. Subsurface stormflow due to impeding characteristic of the underlying layer occurs in form of organic layer interflow and at the interface to the first basal layer (LB1). However, the main driving factor for subsurface stormflow is the formation of a capillary barrier at the interface to the second basal layer (LB2). The capillary barrier prevents water from entering the deeper layer under unsaturated conditions and diverts the seepage water according to the slope inclination. With higher saturation, the capillary barrier breaks down and water reaches the highly conductive deeper layer. This highlights the importance of the capillary barrier effect for the prevention or activation of different flow pathways under variable hydrological conditions.
220

Sulfated Hyaluronan Derivatives Modulate TGF-β1:Receptor Complex Formation: Possible Consequences for TGF-β1 Signaling

Hintze, Vera, Samsonov, Sergey, Rother, Sandra, Vogel, Sarah, Köhling, Sebastian, Moeller, Stephanie, Schnabelrauch, Matthias, Rademann, Jörg, Hempel, Ute, Pisabarro, M. Teresa, Scharnweber, Dieter 10 November 2017 (has links)
Glycosaminoglycans are known to bind biological mediators thereby modulating their biological activity. Sulfated hyaluronans (sHA) were reported to strongly interact with transforming growth factor (TGF)-β1 leading to impaired bioactivity in fibroblasts. The underlying mechanism is not fully elucidated yet. Examining the interaction of all components of the TGF-β1:receptor complex with sHA by surface plasmon resonance, we could show that highly sulfated HA (sHA3) blocks binding of TGF-β1 to its TGF-β receptor-I (TβR-I) and -II (TβR-II). However, sequential addition of sHA3 to the TβR-II/TGF-β1 complex led to a significantly stronger recruitment of TβR-I compared to a complex lacking sHA3, indicating that the order of binding events is very important. Molecular modeling suggested a possible molecular mechanism in which sHA3 could potentially favor the association of TβR-I when added sequentially. For the first time bioactivity of TGF-β1 in conjunction with sHA was investigated at the receptor level. TβR-I and, furthermore, Smad2 phosphorylation were decreased in the presence of sHA3 indicating the formation of an inactive signaling complex. The results contribute to an improved understanding of the interference of sHA3 with TGF-β1:receptor complex formation and will help to further improve the design of functional biomaterials that interfere with TGF-β1-driven skin fibrosis.

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