Lipoxygenase Activity in Diatoms : A New Tool to Study the Antiproliferative Effects of Diatoms on Copepod Reproduction

The deleterious effects of maternal diatom diets on copepod embryonic development have been puzzling the scientific community for the past 15 years. Since the discovery of the first anti-mitotic compounds, polyunsaturated aldehydes deriving from fatty acid oxidation,our knowledge of the oxylipin metabolism in diatoms has been continuously increasing. Not only have new oxylipin compounds been identified, but it is becoming apparent thatoxylipin metabolism is highly complex and specific.This thesis contributes to the understanding of oxylipin metabolism in diatoms by studying the activity of diatom lipoxygenases, the enzymes responsible for the first oxidative step in transforming polyunsaturated fatty acids into oxylipins. Lipoxygenase activity was measured by a colorimetric and a polarographic assay, and its relationship to oxylipin production was examined. Lipoxygenase metabolism in diatoms was studied under natural conditions during a bloom at sea, under semi-natural conditions during a mesocosm experiment, and in the laboratory, with special emphasis on Skeletanema marinai. The effect of diatom oxylipin production on copepod reproductive success was also examined.Increased oxylipin production was found with the onset of the stationary phase in culture and during the decline of the mesocosm bloom, which indicates a regulatory role foroxy lipins in bloom demise, even though this could not be verified at sea. Lipoxygenase activity and oxylipin production were highly variable and specific to the level of clones.The most important conclusion to be drawn from the present experiments is the lack ofcorrelation between lipoxygenase activity and oxylipin production. This strongly indicates that other compounds still need to be identitied and that we do not yet have a complete picture of oxylipin metabolism in diatoms

Determining rotational dynamics of the guanidino group of arginine side chains in proteins by carbon-detected NMR

Arginine residues are imperative for many active sites and protein-interaction interfaces. A new NMR-based method is presented to determine the rotational dynamics around the Nε-Cζ bond of arginine side chains. An application to a 19 kDa protein shows that the strengths of interactions involving arginine side chains can be characterised

Mending the Failing Heart with a Vascularized Cardiac Patch

Functional, stem-cell-containing cardiac grafts will require vascularized myocardial constructs to support their survival and integration into the host vasculature. Recently in Tissue Engineering, Part A, Lesman et al. (2009) reported the successful integration of vascular cells and hESC-derived cardiomyoctyes into stable grafts in rat recipients

Skin regeneration with a synthetic biomaterial that replaces the extracellular matrix

Our extracellular matrix replacement (EMR) is a photopolymerized, polysaccharide-PEG hydrogel scaffold that promotes functional skin regeneration and stimulates wound closure with reduced scarring. The advanced wound care market is dominated by collagen-based products isolated from animal and human tissues, and these products are often costly, show only modest efficacy, and cannot be extensively modified to provide customized devices. Preclinical data indicates that the EMR provides the optimal mechanical and chemical properties to stimulate an effective and efficient inflammatory response, followed by regeneration of a robust vascular network and restoration of a complete reticulated epithelium, hair follicles, and sebaceous glands. The EMR is a biodegradable synthetic biomaterial, and its properties can be rationally modified by adjusting the reaction conditions under which it is produced. Therefore, future generations of EMR products can be tailored to specific wound types and/or loaded with growth factors and small molecules. We will review EMR discovery and development, covering its synthesis and chemical and biochemical characterization. We will present data from our preclinical animal studies in murine and porcine third degree burn and excisional wound models. Finally, we will discuss efforts to develop scalable EMR manufacturing processes and highlight some future directions to develop next generation EMR-based products

Skalen zur Schulqualität: Dokumentation der Erhebungsinstrumente. ArbeitsPlatzUntersuchung (APU), Pädagogische EntwicklungsBilanzen (PEB)

Der Band dokumentiert und systematisiert hauptsächlich die im DIPF- SEL-Projekt "Schulentwicklung, Qualitätssicherung und Lehrerarbeit" entwickelten Erhebungsinstrumente für die Schulforschung und Schulevaluation. Die Dokumentation der Erhebungsinstrumente gibt eine Übersicht über sämtliche im Projekt verwendeten Skalen der Schulqualität. Diese werden ergänzt um Konstrukte der Schul- und Unterrichtsqualität aus anderen DIPF-Projekten, die Merkmale der Schul- und Unterrichtsqualität mit anderen Fragestellungen und Designs untersuchen... . Die Dokumentation der Erhebungsinstrumente gliedert sich in zwei Teile. Teil I basiert auf den Daten des Fragebogens für Lehrkräfte, Teil II auf den Daten des Fragebogens für Schülerinnen und Schüler. ... Inhaltlich erstreckt sich der allgemeine Teil des Fragebogens für Lehrkräfte auf: Unterricht (Unterrichtsformen, Strukturierung des Unterrichts, Benotungspraxis, Hausaufgaben); Einschätzung der Motivation, Leistung und Zufriedenheit der Schüler; schulische Organisation; Kommunikationsverhalten und Zusammenarbeit im Kollegium; Probleme in der Schule und im Unterricht; Berufsansprüche und -ziele; Aspekte der persönlichen Arbeitszeitgestaltung, Berufzufriedenheit; Belastungs- und Bewältigungserleben und Gesundheitszustand; Angaben zur beruflichen Situation. ... Der allgemeine Teil des Fragebogens für Schülerinnen und Schüler erstreckt sich auf: Zufriedenheit mit der Schule, den Lehrkräften und dem eigenen Lernen; Motivation und Interesse am Unterricht; Störungen in Schule und Unterricht; Sozialformen und Methoden im Unterricht; Computernutzung; Lese- und Schreibtechniken; Schulbiografische Angaben; Alltagssprache außerhalb der Schule; Unterstützung bei Hausaufgaben; kulturelle Ressourcen in der Familie; Bildungsaspirationen und Bildungshintergrund der Eltern. (DIPF/Orig.

Adaptive Finite Element Simulation of Coupled PDE/ODE Systems Modeling Intercellular Signaling

Intercellular signaling is a defining property of multicellular organisms, yet the spatio-temporal dynamics remain poorly understood. The subject of this work is the design of an efficient numerical algorithm for simulations of intercellular signaling in multicellular 3D environments modeled by coupled systems of partial differential equations (PDE) and ordinary differential equations (ODE). The PDE part of these systems consists of reaction-diffusion equations and describes the concentration distribution of diffusible messengers, e.g. cytokines. Intracellular dynamics are described by a small number of ODEs per cell. Thus, every single iteration of a commonly used decoupling scheme has similar computational costs than solving the coupled PDE/ODE system at once. We therefore develop an efficient multilevel preconditioner for the coupled system. The computational cost of both coupled and decoupled solution methods are investigated for model problems of different coupling strength. To keep the computational costs of the 3D simulations moderate, we use methods for adaptive mesh refinement. We discretize the system by different time meshes for the PDE and the ODE part to reduce the number of computationally expensive PDE time steps. Reliable a posteriori error estimations for coupled PDE/ODE systems are derived by means of the ’Dual Weighted Residual’ (DWR) method. The discretization error is split into the contributions of the PDE and the ODE part. We compute local error indicators in space and time and set up an efficient adaptive mesh refinement method. The described methods are validated by numerical tests for several biologically motivated model problems. We apply the developed numerical methods and simulate cytokine signaling between T cells in lymph nodes, which regulates the adaptive immune response in the human body. The numerical results show that, despite the high diffusivity of cytokines, highly localized cytokine concentrations with large gradients occur, which enables short-range cell-to-cell communication

Phosphorus limitation and heat stress decrease calcification in Emiliania huxleyi

Calcifying haptophytes (coccolithophores) sequester carbon in the form of organic and inorganic cellular components (coccoliths). We examined the effect of phosphorus (P) limitation and heat stress on particulate organic and inorganic carbon (calcite) production in the coccolithophore Emiliania huxleyi. Both environmental stressors are related to rising CO2 levels and affect carbon production in marine microalgae, which in turn impacts biogeochemical cycling. Using semi-continuous cultures, we show that P limitation and heat stress decrease the calcification rate in E. huxleyi. However, using batch cultures, we show that different culturing approaches (batch versus semi-continuous) induce different physiologies. This affects the ratio of particulate inorganic (PIC) to organic carbon (POC) and complicates general predictions on the effect of P limitation on the PIC = POC ratio. We found heat stress to increase P requirements in E. huxleyi, possibly leading to lower standing stocks in a warmer ocean, especially if this is linked to lower nutrient input. In summary, the predicted rise in global temperature and resulting decrease in nutrient availability may decrease CO2 sequestration by E. huxleyi through lower overall carbon production. Additionally, the export of carbon may be diminished by a decrease in calcification and a weaker coccolith ballasting effect

Three-Dimensional Gradients of Cytokine Signaling between T Cells

Immune responses are regulated by diffusible mediators, the cytokines, which act at sub-nanomolar concentrations. The spatial range of cytokine communication is a crucial, yet poorly understood, functional property. Both containment of cytokine action in narrow junctions between immune cells (immunological synapses) and global signaling throughout entire lymph nodes have been proposed, but the conditions under which they might occur are not clear. Here we analyze spatially three-dimensional reaction-diffusion models for the dynamics of cytokine signaling at two successive scales: in immunological synapses and in dense multicellular environments. For realistic parameter values, we observe local spatial gradients, with the cytokine concentration around secreting cells decaying sharply across only a few cell diameters. Focusing on the well-characterized T-cell cytokine interleukin-2, we show how cytokine secretion and competitive uptake determine this signaling range. Uptake is shaped locally by the geometry of the immunological synapse. However, even for narrow synapses, which favor intrasynaptic cytokine consumption, escape fluxes into the extrasynaptic space are expected to be substantial (≥20% of secretion). Hence paracrine signaling will generally extend beyond the synapse but can be limited to cellular microenvironments through uptake by target cells or strong competitors, such as regulatory T cells. By contrast, long-range cytokine signaling requires a high density of cytokine producers or weak consumption (e.g., by sparsely distributed target cells). Thus in a physiological setting, cytokine gradients between cells, and not bulk-phase concentrations, are crucial for cell-to-cell communication, emphasizing the need for spatially resolved data on cytokine signaling

Schulqualität und Schulevaluation. Schulspezifische Rückmeldung auf der Basis der pädagogischen Entwicklungsbilanzen

Die Arbeit analysiert die Erhebungen aus der Schulentwicklungsstudie "Pädagogische EntwicklungsBilanzen" in Hessen und prüft deren Anwendungsmöglichkeiten für eine schulspezifische Rückmeldung. [...] Der theoretische Teil enthält verschiedene Definitionen von Qualität und darauf aufbauend die theoretischen Grundlagen der Schulentwicklungs- und Schuleffektivitätsforschung. Diese werden in ein Rahmenmodell eingebettet, das Ausgangspunkt für die theoretische Fundierung und Strukturierung der Pädagogischen EntwicklungsBilanzen ist. [...] Ausgangspunkt für den empirischen Teil der Arbeit ist das Untersuchungsdesign und die Analysestrategie der Pädagogischen Entwicklungsbilanzen. Dabei steht die Entwicklung einer auf Skalenmittelwerten basierenden Rückmeldung im Mittelpunkt. (DIPF/Orig.