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Search Results: 1 - 10 of 169475 matches for " Friedrich E. Kruse "
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Mobility of Min-proteins in Escherichia coli measured by fluorescence correlation spectroscopy
G. Meacci,J. Ries,E. Fischer-Friedrich,N. Kahya,P. Schwille,K. Kruse
Physics , 2007, DOI: 10.1088/1478-3975/3/4/003
Abstract: In the bacterium Escherichia coli, selection of the division site involves pole-to-pole oscillations of the proteins MinD and MinE. Different oscillation mechanisms based on cooperative effects between Min-proteins and on the exchange of Min-proteins between the cytoplasm and the cytoplasmic membrane have been proposed. The parameters characterizing the dynamics of the Min-proteins in vivo are not known. It has therefore been difficult to compare the models quantitatively with experiments. Here, we present in vivo measurements of the mobility of MinD and MinE using fluorescence correlation spectroscopy. Two distinct time-scales are clearly visible in the correlation curves. While the faster time-scale can be attributed to cytoplasmic diffusion, the slower time-scale could result from diffusion of membrane-bound proteins or from protein exchange between the cytoplasm and the membrane. We determine the diffusion constant of cytoplasmic MinD to be approximately 16\mu^{2}/s, while for MinE we find about 10\mu^{2}/s, independently of the processes responsible for the slower time-scale. Implications of the measured values for the oscillation mechanism are discussed.
Preventive Effects of Omega-3 and Omega-6 Fatty Acids on Peroxide Mediated Oxidative Stress Responses in Primary Human Trabecular Meshwork Cells
Theofilos Tourtas, Marco T. Birke, Friedrich E. Kruse, Ulrich-Christoph Welge-Lüssen, Kerstin Birke
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0031340
Abstract: Pathologic processes in glaucoma include increased apoptosis, accumulation of extracellular material in the trabecular meshwork and optic nerve, condensations of the cytoskeleton and precocious cellular senescence. Oxidative stress was shown to generate these alterations in primary ocular cells. Fatty acids omega-3 and -6 are alleged to constitute a prophylaxis against these deleterious effects. Here, we tested actual preventive effects omega-3 and -6 against peroxide induced stress responses in primary human trabecular meshwork cells. Changes of mitochondrial activity, proliferation, heat shock proteins, extracellular matrix components, and inflammatory markers were evaluated. Alterations of the cytoskeleton were evaluated by phalloidin labeling. Here we report a repressive effect of omega-6 on metabolic activity and proliferation, which was not detected for omega-3. Both agents were able to prevent the anti-proliferative effect of H2O2, but only omega-3 prevented metabolic repression. Expression of heat shock protein 27 was unaltered by both fatty acids, whereas heat shock protein 90 was significantly induced by both. Omega-6 increased fibronectin and connective tissue growth factor synthesis, as well as the amount of secreted fibronectin. Omega-3, instead, induced plasminogen activator inhibitor 1 synthesis. H2O2 further increased fibronectin production in omega-6 supplemented cells, which was not the case in omega-3 treated cells. H2O2 stimulation of plasminogen activator inhibitor 1 and connective tissue growth factor was repressed by both fatty acids. Both fatty acids appeared to abolish H2O2 mediated stimulation of nuclear factor κB and IL-6, but not IL-1α and IL-8. H2O2 induced formation of cross-linked actin networks and stress fibers, which was reduced by preemptive application of omega-3. Omega-6, in contrast, had no protective effect on that, and even seemed to promote condensation. Based on the observed side effects of omega-6, omega-3 appears to be the more beneficial fatty acid in respect of prophylactic intake for prevention of a glaucomatous disease.
Levels of Aqueous Humor Trace Elements in Patients with Non-Exsudative Age-related Macular Degeneration: A Case-control Study
Anselm G. M. Jünemann, Piotr Stopa, Bernhard Michalke, Anwar Chaudhri, Udo Reulbach, Cord Huchzermeyer, Ursula Schl?tzer-Schrehardt, Friedrich E. Kruse, Eberhart Zrenner, Robert Rejdak
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0056734
Abstract: Trace elements might play a role in the complex multifactorial pathogenesis of age-related macular degeneration (AMD). The aim of this study was to measure alterations of trace elements levels in aqueous humor of patients with non-exsudative (dry) AMD. For this pilot study, aqueous humor samples were collected from patients undergoing cataract surgery. 12 patients with dry AMD (age 77.9±6.62, female 8, male 4) and 11 patients without AMD (age 66.6±16.7, female 7, male 4) were included. Aqueous levels of cadmium, cobalt, copper, iron, manganese, selenium, and zinc were measured by use of Flow-Injection-Inductively-Coupled-Plasm?a-Mass-Spectrometry(FI-ICP-MS), quality controlled with certified standards. Patients with AMD had significantly higher aqueous humor levels of cadmium (median: 0.70 μmol/L, IQR: 0.40–0.84 vs. 0.06 μmol/L; IQR: 0.01–.018; p = 0.002), cobalt (median: 3.1 μmol/L, IQR: 2.62–3.15 vs. 1.17 μmol/L; IQR: 0.95–1.27; p<0.001), iron (median: 311 μmol/L, IQR: 289–329 vs. 129 μmol/L; IQR: 111–145; p<0.001) and zinc (median: 23.1 μmol/L, IQR: 12.9–32.6 vs. 5.1 μmol/L; IQR: 4.4–9.4; p = 0.020) when compared with patients without AMD. Copper levels were significantly reduced in patients with AMD (median: 16.2 μmol/L, IQR: 11.4–31.3 vs. 49.9 μmol/L; IQR: 32.0–.142.0; p = 0.022) when compared to those without. No significant differences were observed in aqueous humor levels of manganese and selenium between patients with and without AMD. After an adjustment for multiple testing, cadmium, cobalt, copper and iron remained a significant factor in GLM models (adjusted for age and gender of the patients) for AMD. Alterations of trace element levels support the hypothesis that cadmium, cobalt, iron, and copper are involved in the pathogenesis of AMD.
Vulnerability of wastewater infrastructure of coastal cities to sea level rise: A South African case study
E Friedrich, D Kretzinger
Water SA , 2012,
Abstract: Sea-level rise is one of the consequences of global warming that has the potential to affect the infrastructure of coastal urban areas. In this context, it is important to perform vulnerability assessments in order to understand how this infrastructure may be at risk, and, if necessary, adapt and maintain functionality of infrastructure systems. This study investigates the vulnerability of the wastewater collection and disposal infrastructure (i.e. pipelines and manholes, pumping stations and wastewater treatment plants) to sea-level rise in eThekwini Municipality, South Africa. By using geographical information systems (GIS) and a multi-criteria analysis considering elevation, operational capacity and connectivity, a scale of vulnerability was established and the most vulnerable infrastructural elements were identified in the municipality. These should be prioritised for detailed monitoring and adaptive interventions in order to maintain the functionality of the wastewater system as sea level is predicted to rise. As such this study presents a model of how vulnerability of wastewater systems can be evaluated in coastal cities.
Creation of the substorm current wedge through the perturbation of the directly driven current system: a new model for substorm expansion
G. Rostoker,E. Friedrich
Annales Geophysicae (ANGEO) , 2005,
Abstract: The past four decades have seen a considerable amount of research on the study of magnetospheric substorms, and over most of these years the expansive phase of the substorm has been associated with the development of a three dimensional current system that has been termed the substorm current wedge. This current system has been thought to be a consequence of the short-circuiting of crosstail current through the ionosphere, and is viewed as a distinctive current system operating independently from the directly driven current with which it co-exists. The purpose of this paper is to show that the substorm current wedge should be viewed as an equivalent current system rather than a real current system. It will be shown that the magnetic perturbation pattern associated with the current wedge can be modeled as purely a perturbation of the directly driven current system in the midnight sector. Keywords. Magnetospheric physics (Auroral phenomena; Current systems; Magnetotail; Storms and substorms
Sobre os diferentes métodos de traduzir
Friedrich E. D. Schleiermacher
Princípios : Revista de Filosofia , 2007,
Abstract: Tradu o do texto über die verschiedenen Methoden des übersetzens, redigido no período em que Schleiermacher lecionava em Berlim, originalmente escrito como base para uma conferência proferida em 24 de junho de 1813, na Academia Real de Ciências. A presente tradu o baseia-se na publica o inclusa na Friedrich Schleiermacher’s s mmtliche Werke, Dritte Abteilung: Zur Philosophie, Zweiter Bd., Berlin, Reimer, 1838, S. 207-245. [Tradu o de Celso Braida, Professor do Departamento de Filosofia da UFSC.]
Climate change and urban road transport - a South African case study of vulnerability due to sea level rise
E Friedrich,S Timol
Journal of the South African Institution of Civil Engineering , 2011,
Abstract: The focus of this investigation was the impact of predicted sea level rise on the road transportation network of the eThekwini Municipality, South Africa. The main objective was to identify the areas within the municipality which are most vulnerable to sea level rise and to develop adaptive responses and interventions in order to maintain road functionality. For the identification of the most vulnerable areas a multi-criteria analysis supported by geographical information system modelling was used. Three areas were identified, namely, the Isipingo, Bayhead and the Umgeni mouth areas. Adaptive road responses have been researched by employing a network analysis of each of the areas identified. Parameters modelled were traffic volume changes, travel time and volume to capacity ratio - for the main roads in the areas identified. The adaptive responses required for each area were found to be different, varying from the addition of a lane to changes in signal settings. Overall this study presents a model of how vulnerability and the development of adaptive strategies to sea level rise could be addressed by municipalities.
Membrane Binding of MinE Allows for a Comprehensive Description of Min-Protein Pattern Formation
Mike Bonny,Elisabeth Fischer-Friedrich,Martin Loose,Petra Schwille,Karsten Kruse
PLOS Computational Biology , 2013, DOI: 10.1371/journal.pcbi.1003347
Abstract: The rod-shaped bacterium Escherichia coli selects the cell center as site of division with the help of the proteins MinC, MinD, and MinE. This protein system collectively oscillates between the two cell poles by alternately binding to the membrane in one of the two cell halves. This dynamic behavior, which emerges from the interaction of the ATPase MinD and its activator MinE on the cell membrane, has become a paradigm for protein self-organization. Recently, it has been found that not only the binding of MinD to the membrane, but also interactions of MinE with the membrane contribute to Min-protein self-organization. Here, we show that by accounting for this finding in a computational model, we can comprehensively describe all observed Min-protein patterns in vivo and in vitro. Furthermore, by varying the system's geometry, our computations predict patterns that have not yet been reported. We confirm these predictions experimentally.
Intra- and intercellular fluctuations in Min-protein dynamics decrease with cell length
Elisabeth Fischer-Friedrich,Giovanni Meacci,Joe Lutkenhaus,Hugues Chate,Karsten Kruse
Quantitative Biology , 2010, DOI: 10.1073/pnas.0911708107
Abstract: Self-organization of proteins in space and time is of crucial importance for the functioning of cellular processes. Often, this organization takes place in the presence of strong random fluctuations due to the small number of molecules involved. We report on stochastic switching of the Min-protein distributions between the two cell halves in short Escherichia coli cells. A computational model provides strong evidence that the macroscopic switching is rooted in microscopic noise on the molecular scale. In longer bacteria, the switching turns into regular oscillations that are required for positioning of the division plane. As the pattern becomes more regular, cell-to-cell variability also lessens, indicating cell length-dependent regulation of Min-protein activity.
Shape mode analysis exposes movement patterns in biology: flagella and flatworms as case studies
Steffen Werner,Jochen C. Rink,Ingmar H. Riedel-Kruse,Benjamin M. Friedrich
Quantitative Biology , 2014, DOI: 10.1371/journal.pone.0113083
Abstract: We illustrate shape mode analysis as a simple, yet powerful technique to concisely describe complex biological shapes and their dynamics. We characterize undulatory bending waves of beating flagella and reconstruct a limit cycle of flagellar oscillations, paying particular attention to the periodicity of angular data. As a second example, we analyze non-convex boundary outlines of gliding flatworms, which allows us to expose stereotypic body postures that can be related to two different locomotion mechanisms. Further, shape mode analysis based on principal component analysis allows to discriminate different flatworm species, despite large motion-associated shape variability. Thus, complex shape dynamics is characterized by a small number of shape scores that change in time. We present this method using descriptive examples, explaining abstract mathematics in a graphic way.
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