University of Tübingen

About: University of Tübingen is a education organization based out in Tübingen, Germany. It is known for research contribution in the topics: Population & Transplantation. The organization has 40555 authors who have published 84108 publications receiving 3015320 citations. The organization is also known as: Eberhard Karls University & Eberhard-Karls-Universität Tübingen.

Facilities for macromolecular crystallography at the Helmholtz-Zentrum Berlin

Abstract: Three macromolecular crystallography (MX) beamlines at the Helmholtz-Zentrum Berlin (HZB) are available for the regional, national and international structural biology user community. The state-of-the-art synchrotron beamlines for MX BL14.1, BL14.2 and BL14.3 are located within the low-β section of the BESSY II electron storage ring. All beamlines are fed from a superconducting 7 T wavelength-shifter insertion device. BL14.1 and BL14.2 are energy tunable in the range 5–16 keV, while BL14.3 is a fixed-energy side station operated at 13.8 keV. All three beamlines are equipped with CCD detectors. BL14.1 and BL14.2 are in regular user operation providing about 200 beam days per year and about 600 user shifts to approximately 50 research groups across Europe. BL14.3 has initially been used as a test facility and was brought into regular user mode operation during the year 2010. BL14.1 has recently been upgraded with a microdiffractometer including a mini-κ goniometer and an automated sample changer. Additional user facilities include office space adjacent to the beamlines, a sample preparation laboratory, a biology laboratory (safety level 1) and high-end computing resources. In this article the instrumentation of the beamlines is described, and a summary of the experimental possibilities of the beamlines and the provided ancillary equipment for the user community is given.

Fault‐graded beds interpreted as seismites

Abstract: SUMMARY Fault grading is expressed by a regular structural sequence of (from top) liquified zone, rubble zone and step-faulted zone, with gradational contacts between these zones and the bottom, but with a sharp boundary at the top. It is interpreted as an effect of strong earthquakes on gradationally compacted muds in quiet water basins. Fault-graded beds are geopetal and paleoslope criteria. If interpreted as seismites they may also be used as paleo-seismograms.

Transdifferentiation of Vascular Smooth Muscle Cells to Macrophage-Like Cells During Atherogenesis

Abstract: Rationale:Atherosclerosis is a widespread and devastating disease, but the origins of cells within atherosclerotic plaques are not well defined. Objective:To investigate the specific contribution of vascular smooth muscle cells (SMCs) to atherosclerotic plaque formation by genetic inducible fate mapping in mice. Methods and Results:Vascular SMCs were genetically pulse-labeled using the tamoxifen-dependent Cre recombinase, CreERT2, expressed from the endogenous SM22α locus combined with Cre-activatable reporter genes that were integrated into the ROSA26 locus. Mature SMCs in the arterial media were labeled by tamoxifen treatment of young apolipoprotein E–deficient mice before the development of atherosclerosis and then their fate was monitored in older atherosclerotic animals. We found that medial SMCs can undergo clonal expansion and convert to macrophage-like cells that have lost classic SMC marker expression and make up a major component of advanced atherosclerotic lesions. Conclusions:This study provid...

Modulation of tight junction structure in blood-brain barrier endothelial cells. Effects of tissue culture, second messengers and cocultured astrocytes

Abstract: Tight junctions between endothelial cells of brain capillaries are the most important structural elements of the blood-brain barrier. Cultured brain endothelial cells are known to loose tight junction-dependent blood-brain barrier characteristics such as macromolecular impermeability and high electrical resistance. We have directly analyzed the structure and function of tight junctions in primary cultures of bovine brain endothelial cells using quantitative freeze-fracture electron microscopy, and ion and inulin permeability. The complexity of tight junctions, defined as the number of branch points per unit length of tight junctional strands, decreased 5 hours after culture but thereafter remained almost constant. In contrast, the association of tight junction particles with the cytoplasmic leaflet of the endothelial membrane bilayer (P-face) decreased continuously with a major drop between 16 hours and 24 hours. The complexity of tight junctions could be increased by elevation of intracellular cAMP levels while phorbol esters had the opposite effect. On the other hand, the P-face association of tight junction particles was enhanced by elevation of cAMP levels and by coculture of endothelial cells with astrocytes or exposure to astrocyte-conditioned medium. The latter effect on P-face association was induced by astrocytes but not fibroblasts. Elevation of cAMP levels together with astrocyte-conditioned medium synergistically increased transendothelial electrical resistance and decreased inulin permeability of primary cultures, thus confirming the effects on tight junction structure and barrier function. P-face association of tight junction particles in brain endothelial cells may therefore be a critical feature of blood-brain barrier function that can be specifically modulated by astrocytes and cAMP levels. Our results suggest an important functional role for the cytoplasmic anchorage of tight junction particles for brain endothelial barrier function in particular and probably paracellular permeability in general.

Extrathymic T-cell differentiation in vitro

Abstract: 1 April 2004 The first ‘Innovation’ article in Nature Reviews Immunology discussed the introduction of a technique for the extrathymic generation of T cells in culture, which was suggested as being a useful new tool for studying T-cell differentiation in a way that was not previously possible. The originators of this technique showed that extrathymic differentiation from bone-marrow progenitors in vitro can be accomplished using the OP9 stromal cell line, ectopically expressing the Notch ligand delta-like 1 (REFS 1,2). It was stated that this allowed T-cell-differentiation processes to be studied in a simple cell-culture system for the first time. Although this might be true for mouse cells, it is not the case for human cells. Some years ago, we showed that CD34 lineage-negative human haematpoietic progenitors could acquire mature T-cell characteristics in a thymus-free culture system. This depended on the presence of peripheral-blood mononuclear cells (PBMCs) as feeder cells, cytokine cocktails and the use of serum-free media. Given the importance of delta-like 1, identified in the mouse system, and the fact that Notch ligands, including this one, are expressed by antigen-presenting cells, one could ask why previous attempts by others to establish extrathymic T-cell-differentiation systems using PBMCs were less successful. We suggest that the reason for such failures was probably the choice of culture medium and, to a lesser extent, the choice of cytokine cocktail and feeder cells. We tested many different formulations over the years, at first containing human serum or fetal-calf serum, with little success. We also tested many serum-free formulations, with equal lack of success. However, the use of the then newly developed X-Vivo 10 medium from BioWhittaker allowed development, for the first time, of T cells in the absence of thymic components in a limitingdilution cloning system. It was necessary to include stem-cell factor (SCF), fms-related tyrosine kinase 3 ligand (FLT3L), interleukin-2 (IL-2) and IL-3 in the cytokine cocktail. Cloning efficiencies were markedly increased by additional inclusion of oncostatin M or IL-7 (REF. 8). Feeder cells consisted of irradiated (at a dose such that no cells escaped proliferation blockade after irradiation) PBMCs pooled from 20 different donors. During the cloning procedure, these cells would have interacted with each other as a multi-way mixed-lymphocyte culture, resulting in cytokine release, and macrophage and dendritic-cell activation. The purity of the starting haematopoietic-cell population and the high cloning efficiency that could be achieved ruled out the possibility that the T cells isolated were derived from contaminants in the starting population. Derived T cells were not autoreactive, suggesting that negative selection had taken place in a system where the feeder cells did express MHC class II or class I molecules, unlike the OP9 mouse system recently discussed. Derived clones were mostly CD4 αβ-T-cell receptor 2 (TCR2), expressed a wide range of antigen-receptor clonotypes, responded to mitogenic stimulation by proliferation and cytokine release, and had the cell-surface markers and growth characteristics typical of human CD4 T-cell clones. Currently, human T-cell clones derived in this manner are being examined by European Union-supported consortia focused on ageing of the immune system, ImAginE and T-CIA (see further information for websites). Perhaps because of our focus on immunogerontology, and exclusively in humans, these previous findings might have been overlooked.