Scaffold dimensionality and confinement determine single cell morphology and migration

This thesis describes a highly interdisciplinary approach to discern the differing impact of scaffold dimensionality and physical space restrictions on the behavior of single cells. Rolled-up nanotechnology is employed to fabricate three-dimensional (3D) SiO/SiO2 microtube geometries of varied diameter, that after a biofunctionalization step are shown to support the growth of U2OS and six different types of stem cells. Cell confinement quantifiable through the given microtube diameter is tolerated by U2OS cells through a remarkable elongation of the cell body and nucleus down to a certain threshold, while the integrity of the DNA is maintained. This confinement for NSPCs also leads to the approaching of the in vivo morphology, underlining the space-restrictive property of live tissue. The dimensionality of the cell culture scaffold however is identified as the major determiner of NSPC migration characteristics and leads to a morphologically distinct mesenchymal to amoeboid migration mode transition. The 3D microtube migration is characterized by exclusively filopodia protrusion formation, a higher dependence on actin polymerization and adopts aspects of in vivo-reported saltatory movement. The reported findings contribute to the determination of biomaterial scaffold design principles and advance our current understanding of how physical properties of the extracellular environment affect cell migration characteristics

Entwicklung eines DNA Microarrays zur genomweiten Analyse Polycomb-vermittelter Genregulation in Drosophila melanogaster

Durch die Sequenzierungsprojekte der letzten Jahre konnte eine eindrucksvolle Menge an Daten über die Anzahl und Struktur der Gene sowie über die strukturelle und funktionelle Organisation von Genomen angesammelt werden. Diese Informationen bilden die Grundlage für Projekte, die es in Zukunft ermöglichen werden, die Rolle jeden Gens innerhalb des komplexen Zusammenspiels der Gene im lebenden System zu erforschen. Eine Methode, die auf solche Fragestellungen ausgerichtet ist, nutzt DNA Microarrays. Mit ihrer Hilfe kann die Expression von Genen eines gesamten Genoms zu bestimmten Zeitpunkten oder in verschiedenen Geweben untersucht werden. Auch epigenetische Mechanismen der Regulation können mit einem solchen System untersucht werden. Zwei Gruppen von Genen, die eine wichtige Rolle in diesem als �zelluläres Gedächtnis� bezeichneten Prozess spielen, sind die Polycomb-Gruppe und die trithorax-Gruppe. Während die trithorax- Gruppe die Aufgabe erfüllt, das Expressionsmuster von aktiven Genen während der Entwicklung aufrecht zu erhalten, kommt der Polycomb-Gruppe die Aufgabe zu, den reprimierten Zustand von Genen über viele Zellteilungen sicherzustellen. Innerhalb dieser Arbeit wurden mit Hilfe der Microarraytechnik Gene untersucht, die der regulatorischen Funktion dieser beiden Gengruppen unterliegen. Hierzu wurde in Kollaboration mit anderen Gruppen ein PCR-basierter DNA Microarray entwickelt, der ausgewählte Sequenzen für 20,948 ORFs enthält, die in einer neuen Annotation der Drosophila Genomsequenz identifiziert wurden. Um die in dieser Annotation enthaltenen 7,400 Gene zu validieren, die in vorangegangen Genvorhersagen nicht berücksichtigt wurden, wurde zunächst mit Hilfe des Microarrays ein Entwicklungsprofil mit neun verschiedenen Stadien des Lebenszyklus von Drosophila durchgeführt. Durch diese Analysen und molekularbiologische Validierungen über RT-PCR und in-situ Hybridisierungen konnten etwa 2,000 neue Gene für Drosophila bestätigt werden. Dieser Microarray wurde in weiteren Experimenten eingesetzt, um Hinweise auf Zielgene Polycomb-abhängiger Regulation zu bekommen. Dazu wurden Methoden entwickelt, um die Zielgene zu verschiedenen Zeitpunkten und in unterschiedlichen Geweben ermitteln zu können. Der Vergleich von cDNA Polycomb mutanter Fliegen mit Kontroll-cDNA auf dem Microarray gab erste Hinweise auf Zielgene in frühen embryonalen Stadien. Insgesamt legt diese Arbeit eine wichtige Grundlage für die Analyse aller Gene in Drosophila melanogaster, die über den Mechanismus des �zellulären Gedächtnisses� reguliert werden. Dieses Wissen wird dazu beitragen können, die komplexen Prozesse während der Entstehung eines Lebewesens besser zu verstehen

Competitive Packet Routing with Priority Lists

In competitive packet routing games, packets are routed selfishly through a network and scheduling policies at edges determine which packages are forwarded first if there is not enough capacity on an edge to forward all packages at once. We analyze the impact of priority lists on the worst-case quality of pure Nash equilibria. A priority list is an ordered list of players that may or may not depend on the edge. Whenever the number of packets entering an edge exceeds the inflow capacity, packets are processed in list order. We derive several new bounds on the price of anarchy and stability for global and local priority policies. We also consider the question of the complexity of computing an optimal priority list. It turns out that even for very restricted cases, i.e., for routing on a tree, the computation of an optimal priority list is APX-hard

Oligopolistic Competitive Packet Routing

Oligopolistic competitive packet routing games model situations in which traffic is routed in discrete units through a network over time. We study a game-theoretic variant of packet routing, where in contrast to classical packet routing, we are lacking a central authority to decide on an oblivious routing protocol. Instead, selfish acting decision makers ("players") control a certain amount of traffic each, which needs to be sent as fast as possible from a player-specific origin to a player-specific destination through a commonly used network. The network is represented by a directed graph, each edge of which being endowed with a transit time, as well as a capacity bounding the number of traffic units entering an edge simultaneously. Additionally, a priority policy on the set of players is publicly known with respect to which conflicts at intersections are resolved. We prove the existence of a pure Nash equilibrium and show that it can be constructed by sequentially computing an integral earliest arrival flow for each player. Moreover, we derive several tight bounds on the price of anarchy and the price of stability in single source games

Reviews

Magdalena S. Midgley: The Origin and Function of the Earthen Long Barrows of Northern Europe (by D. Liversage).Ben A. Nelson (ed.): Decoding Prehistoric Ceramics (by Eva Koch Nielsen).Pia Bennike: Palaeopathology of Danish Skeletons (by Per Holch).Inga Hagg: Die Textilfonde aus dem Hafen von Haithabu (by Lise Bender Jorgensen).Else Roesdahl: Viking Age Denmark (by Birgitta Hardh)

Carbonate-based Janus micromotors moving in ultra-light acidic environment generated by HeLa cells in situ

Novel approaches to develop naturally-induced drug delivery in tumor environments in a deterministic and controlled manner have become of growing interest in recent years. Different polymeric-based microstructures and other biocompatible substances have been studied taking advantage of lactic acidosis phenomena in tumor cells, which decrease the tumor extracellular pH down to 6.8. Micromotors have recently demonstrated a high performance in living systems, revealing autonomous movement in the acidic environment of the stomach or moving inside living cells by using acoustic waves, opening the doors for implementation of such smart microengines into living entities. The need to develop biocompatible motors which are driven by natural fuel sources inherently created in biological systems has thus become of crucial importance. As a proof of principle, we here demonstrate calcium carbonate Janus particles moving in extremely light acidic environments (pH 6.5), whose motion is induced in conditioned acidic medium generated by HeLa cells in situ. Our system not only obviates the need for an external fuel, but also presents a selective activation of the micromotors which promotes their motion and consequent dissolution in presence of a quickly propagating cell source (i.e. tumor cells), therefore inspiring new micromotor configurations for potential drug delivery systems

Biomimetic microelectronics for regenerative neuronal cuff implants

Smart biomimetics, a unique class of devices combining the mechanical adaptivity of soft actuators with the imperceptibility of microelectronics, is introduced. Due to their inherent ability to self‐assemble, biomimetic microelectronics can firmly yet gently attach to an inorganic or biological tissue enabling enclosure of, for example, nervous fibers, or guide the growth of neuronal cells during regeneration

(3,5,5,6,8,8-Hexamethyl-5,6,7,8-tetra­hydro­naphthalen-2-yl)methanol: a possible metabolite of the synthetic musk fragrance AHTN

The title compound (AHTN-OH), C17H26O, was prepared in order to provide standard materials for the qualitative and quanti­tative analysis of environmental pollutants. The mol­ecule possesses a chiral C atom, although the structure determination was performed on racemic material, expressed in the structure as disordered chiral sites. The asymmetric unit consists of four AHTN-OH mol­ecules containing an hy­droxy group and forming a tetra­meric cyclic motif built up by four strong hydrogen bonds between these hy­droxy groups and additionally by two weak C—H⋯π inter­actions. Furthermore, these tetra­mers are linked via very weak C—H⋯π inter­actions, forming chains along the c axis

Adoptive Cell Transfer of Allogeneic Epstein-Barr Virus-Specific T Lymphocytes for Treatment of Refractory EBV-Associated Posttransplant Smooth Muscle Tumors: A Case Report

Posttransplant smooth muscle tumors (PTSMTs) are rare Epstein-Barr virus (EBV)-associated neoplasms, mostly occurring after solid organ transplantation. Current therapeutic strategies include surgery and reduction of immunosuppressive medication. We describe for the first time a novel treatment approach for PTSMT by adoptive cell transfer (ACT) of EBV-specific T cells to a 20-year-old patient with a medical history of cardiac transplantation, posttransplant lymphoproliferative disease, and multilocular PTSMT. During ACT, mild cytokine release syndrome occurred, while no unexpected safety signals were recorded. We observed in vivo expansion of EBV-specific T cells and reduction of EBV viremia. Best response was stable disease after 4 months with reduction of EBV viremia and normalization of lactate dehydrogenase levels. ACT with EBV-specific T cells may be a safe and efficacious therapeutic option for PTSMT that warrants further exploration

Real-Time Message Routing and Scheduling

Exchanging messages between nodes of a network (e.g., embedded computers) is a fundamental issue in real-time systems involving critical routing and scheduling decisions. In order for messages to meet their deadlines, one has to determine a suitable (short) origin-destination path for each message and resolve conflicts between messages whose paths share a communication link of the network. With this paper we contribute to the theoretic foundations of real-time systems. On the one hand, we provide efficient routing strategies yielding origin-destination paths of bounded dilation and congestion. In particular, we can give good a priori guarantees on the time required to send a given set of messages which, under certain reasonable conditions, implies that all messages can be scheduled to reach their destination on time. Finally, for message routing along a directed path (which is already NP-hard), we identify a natural class of instances for which a simple scheduling heuristic yields provably optimal solutions