Mechanisms of lumen formation during sprouting angiogenesis in vivo

During development, vascular networks expand following a process known as sprouting angiogenesis. New vascular branches arise from pre-existing vessels through the coordinated migration and proliferation of endothelial cells, and eventually connect to form new vascular loops. The functionality of these new vessel segments is dependent on the opening of a central lumen to allow perfusion. While mechanisms of lumen formation during the establishment of the primary vasculature by vasculogenesis have been well characterised, the mechanisms underlying lumen formation during sprouting angiogenesis in vivo are still poorly understood and subject to debate. In this work, I established high spatial and temporal imaging of apical membrane dynamics during sprouting angiogenesis in vivo, both in the zebrafish trunk vasculature and the mouse retina primary inner plexus. By doing so, I identified a novel mechanism of lumen formation, where blood flow expands luminal compartments by driving spherical deformations reminiscent of membrane blebs at the apical membrane of sprouting endothelial cells. Additionally, I show that this process, that I chose to term inverse membrane blebbing, is tightly controlled through local and transient recruitment and contraction of actomyosin at the surface of growing blebs. This mechanism eventually leads to the selective retraction of inverse blebs along the apical membrane, allowing unidirectional lumen expansion. When endothelial cells ability to retract is inhibited through expression of a dominant-negative form of myosin II, cells fail to lumenise or show dilated lumens with multiple unresolved side blebs and branches. Together, this work provides a mechanism for lumen expansion within sprouting endothelial cells in vivo, and identifies for the first time inverse blebbing as a reaction of membranes to high external pressure. In the context of sprouting endothelial cells, I show that a tight equilibrium between the forces exerted by the blood and the contractile responses from the cells is required for lumen expansion within angiogenic sprouts

Gefangen im eigenen Mythos? : zur Konstruktion kollektiver Identität in Mittel- und Osteuropa am Beispiel Polens ; Grundlagen für die internationale Austauschpädagogik

Welchen Einfluss hat die Konstruktion von Nation auf die kollektive Identitätsbildung? Welches Verständnis von Nationalität ist in Mittel- und Osteuropa vorherrschend? Inwieweit müssen Fragen der kollektiven Identität in der internationalen Austauschpädagogik berücksichtigt werden? Diesen Fragen geht die sich im interdisziplinären Feld sozial-, politik- und erziehungswissenschaftlicher Diskurse bewegende Arbeit nach und beleuchtet damit einen hoch aktuellen, in der Forschung bisher jedoch nur wenig beachteten Gegenstand. Den Ausgangspunkt der Überlegungen bildet das Spannungsverhältnis zwischen europäischer Integration und nationaler Selbstfindung in Ländern Mittel- und Osteuropas. Vor diesem Hintergrund werden Konstruktionen von Nationalität und kollektiver Identität, nationale Mythen und Symbole, ihre Entstehungsgeschichten, Wirkungen, Rahmungen und Funktionalitäten diskutiert. Der Schwerpunkt liegt dabei auf der Betrachtung Polens, wo die Ambivalenz zwischen Nationalismus und Homogenisierung einerseits und Europäisierung und Pluralisierung andererseits eine einmalige Plakativität und Evidenz erfährt. Die Reflexion darüber, wie diese Disparität aktuelle politische und gesellschaftliche Entwicklungen beeinflusst und vor welche Herausforderungen sie die pädagogische Praxis stellt, gehört zu den zentralen Fragestellungen dieser Arbeit

Globalization and local development : does a peasant farmer in Marera in Mozambique benefit from trade liberalization?

Mozambique is one of the poorest countries in the world, with most of its population living in rural areas. The study analysed the impact of trade liberalization on peasant farmers involved in fruit production in Marera in Central Mozambique and measured their benefits and life improvements as compared with the decade of the 1990s. It found that 73.3% of peasant farmers assess their life as little better than 10-15 years ago and only 5.6% have experienced substantial improvements. It was discovered that better knowledge and access to productive resources play a role in improving benefits from fruit production and trade. Therefore, the study concluded that although trade liberalization can bring benefits, when appropriate conditions are met, peasant farmers in Marera are not different from their counterparts around the world and benefit little from trade liberalization.M.A. (Development Studies)Development Studie

Optimizing Segment Based Document Protection (Corrected Version)

In this paper we provide a corrected and generalized version of the scheme presented at SOFSEM\u272012 in our paper ``Optimizing Segment Based Document Protection\u27\u27 (SOFSEM 2012: Theory and Practice of Computer Science, LNCS 7147, pp. 566-575). We develop techniques for protecting documents with restricted access rights. In these documents so called \emph{segments} are encrypted. Different segments may be encrypted with different keys so that different user may be given different \emph{access rights}. Hierarchy of access rights is represented by means of a directed acyclic \emph{access graph}. The segments are encrypted with keys - where each key corresponds to one node in the access graph. The main feature of the access graph is that if there is an arch $\overrightarrow{AB}$ in the graph, then all segments labelled with $B$ can be decrypted with the key corresponding to node $A$. We show how to minimize the space overhead necessary for auxiliary keying information stored in the document. We provide an algorithm based on node disjoint paths in the access graph and key derivation based on one-way functions. Our current solution, based on maximal weighted matchings, provides an optimal solution for creating subdocuments, in case when frequency of creating each subdocument is known

Blood flow drives lumen formation by inverse membrane blebbing during angiogenesis in vivo

How vascular tubes build, maintain and adapt continuously perfused lumens to meet local metabolic needs remains poorly understood. Recent studies showed that blood flow itself plays a critical role in the remodelling of vascular networks, and suggested it is also required for the lumenization of new vascular connections. However, it is still unknown how haemodynamic forces contribute to the formation of new vascular lumens during blood vessel morphogenesis. Here we report that blood flow drives lumen expansion during sprouting angiogenesis in vivo by inducing spherical deformations of the apical membrane of endothelial cells, in a process that we have termed inverse blebbing. We show that endothelial cells react to these membrane intrusions by local and transient recruitment and contraction of actomyosin, and that this mechanism is required for single, unidirectional lumen expansion in angiogenic sprouts. Our work identifies inverse membrane blebbing as a cellular response to high external pressure. We show that in the case of blood vessels such membrane dynamics can drive local cell shape changes required for global tissue morphogenesis, shedding light on a pressure-driven mechanism of lumen formation in vertebrates

Pericytes or mesenchymal stem cells: is that the question?

For almost a decade, mesenchymal stem cells (MSCs) were believed to reside as perivascular cells in vivo. In this issue of Cell Stem Cell, Guimaraes-Camboa et al. (2017) challenge this idea and use lineage tracing to demonstrate that perivascular cells do not behave as tissue-specific progenitors in various organs, despite showing MSC potential in vitro

Selected physical medicine interventions in the treatment of diabetic foot syndrome

The diabetic foot syndrome (DFS) is among chronic complications of diabetes mellitus; it can affect individuals with both type 1 and type 2 diabetes. Diabetic patients have up to a 25% lifetime risk of developing DFS, which is both a medical and social problem. Several studies have indicated that, apart from pharmacotherapy and modern active wound dressings, physical medicine also has a role in prevention and management of diabetic foot ulcers. The paper presents physical medicine interventions most recognized in the conservative management of DFS

Selected physical medicine interventions in the treatment of diabetic foot syndrome

The diabetic foot syndrome (DFS) is among chronic complications of diabetes mellitus; it can affect individuals with both type 1 and type 2 diabetes. Diabetic patients have up to a 25% lifetime risk of developing DFS, which is both a medical and social problem. Several studies have indicated that, apart from pharmacotherapy and modern active wound dressings, physical medicine also has a role in prevention and management of diabetic foot ulcers. The paper presents physical medicine interventions most recognized in the conservative management of DFS.The diabetic foot syndrome (DFS) is among chronic complications of diabetes mellitus; it can affect individuals with both type 1 and type 2 diabetes. Diabetic patients have up to a 25% lifetime risk of developing DFS, which is both a medical and social problem. Several studies have indicated that, apart from pharmacotherapy and modern active wound dressings, physical medicine also has a role in prevention and management of diabetic foot ulcers. The paper presents physical medicine interventions most recognized in the conservative management of DFS

A new crystal modification of diammonium hydrogen phosphate, (NH4)2(HPO4)

The addition of hexa­fluorido­phosphate salts (ammonium, silver, thallium or potassium) is usually used to precipitate complex cations from aqueous solutions. It has long been known that PF6 − is sensitive towards hydrolysis under acidic conditions [Gebala & Jones (1969 ▶). J. Inorg. Nucl. Chem. 31, 771–776; Plakhotnyk et al. (2005 ▶). J. Fluorine Chem. 126, 27–31]. During the course of our investigation into coinage metal complexes of diphosphine ligands, we used ammonium hexa­fluorido­phosphate in order to crystallize [Ag(diphos­phine)2]PF6 complexes. From these solutions we always obtained needle-like crystals which turned out to be the title compound, 2NH4 +·HPO4 2−. It was received as the hydrolysis product of NH4PF6. The crystals are a new modification of diammonium hydrogen phosphate. In contrast to the previously published polymorph [Khan et al. (1972 ▶). Acta Cryst. B28, 2065–2069], Z′ of the title compound is 2. In the new modification of the title compound, there are eight mol­ecules of (NH4)2(HPO4) in the unit cell. The structure consists of PO3OH and NH4 tetra­hedra, held together by O—H⋯O and N—H⋯O hydrogen bonds