Nanometer scale description of electron transport and damage in condensed media using the TRAX Monte Carlo Code

The single interaction Monte Carlo code TRAX has been extended to describe low-energy electron creation and transport in solids. Electrons with energies below 1 keV have ranges in solids on the nanometerscale. Complete sets of electron interaction cross sections for energies below 1 keV down to 1 eV have been compiled and assessed for various target materials. The applicability of the cross sections has been validated by comparisons with experimental data as far as available. The code has further been extended to handle the production of Auger electrons and cascades. Furthermore, the capability to handle non-uniform targets has been added. With the extended TRAX code, experimental data from GSI’s Toroid electron spectrometer have been reproduced using thin solid state foils of carbon, nickel, silver and gold as targets. Furthermore, the radial dose distribution around ion tracks has been investigated on the nanometer scale. The explicit consideration of Auger electron cascades has been used to evaluate whether metallic nanoparticles can locally enhance the dose in combination with proton or electron irradiation

Propagation of CJD Prions in Primary Murine Glia Cells Expressing Human PrPc

There are various existing cell models for the propagation of animal prions. However, in vitro propagation of human prions has been a long-standing challenge. This study presents the establishment of a long-term primary murine glia culture expressing the human prion protein homozygous for methionine at codon 129, which allows in vitro propagation of Creutzfeldt–Jakob disease (CJD) prions (variant CJD (vCJD) and sporadic CJD (sCJD) type MM2). Prion propagation could be detected by Western blotting of pathological proteinase K-resistant prion protein (PrPSc) from 120 days post exposure. The accumulation of PrPSc could be intensified by adding a cationic lipid mixture to the infectious brain homogenate at the time of infection. Stable propagation of human prions in a long-term murine glia cell culture represents a new tool for future drug development and for mechanistic studies in the field of human prion biology. In addition, our cell model can reduce the need for bioassays with human prions and thereby contributes to further implementation of the 3R principles aiming at replacement, reduction and refinement of animal experiments.Peer Reviewe

Nanolesions induced by heavy ions in human tissues: experimental and theoretical studies

The biological effects of energetic heavy ions are attracting increasing interest for their applications in cancer therapy and protection against space radiation. The cascade of events leading to cell death or late effects starts from stochastic energy deposition on the nanometer scale and the corresponding lesions in biological molecules, primarily DNA. We have developed experimental techniques to visualize DNA nanolesions induced by heavy ions. Nanolesions appear in cells as “streaks” which can be visualized by using different DNA repair markers. We have studied the kinetics of repair of these “streaks” also with respect to the chromatin conformation. Initial steps in the modeling of the energy deposition patterns at the micrometer and nanometer scale were made with MCHIT and TRAX models, respectively

Bartonella Adhesin A Mediates a Proangiogenic Host Cell Response

Bartonella henselae causes vasculoproliferative disorders in humans. We identified a nonfimbrial adhesin of B. henselae designated as Bartonella adhesin A (BadA). BadA is a 340-kD outer membrane protein encoded by the 9.3-kb badA gene. It has a modular structure and contains domains homologous to the Yersinia enterocolitica nonfimbrial adhesin (Yersinia adhesin A). Expression of BadA was restored in a BadA-deficient transposon mutant by complementation in trans. BadA mediates the binding of B. henselae to extracellular matrix proteins and to endothelial cells, possibly via β1 integrins, but prevents phagocytosis. Expression of BadA is crucial for activation of hypoxia-inducible factor 1 in host cells by B. henselae and secretion of proangiogenic cytokines (e.g., vascular endothelial growth factor). BadA is immunodominant in B. henselae–infected patients and rodents, indicating that it is expressed during Bartonella infections. Our results suggest that BadA, the largest characterized bacterial protein thus far, is a major pathogenicity factor of B. henselae with a potential role in the induction of vasculoproliferative disorders

Propagation of CJD Prions in Primary Murine Glia Cells Expressing Human PrPc

There are various existing cell models for the propagation of animal prions. However, in vitro propagation of human prions has been a long-standing challenge. This study presents the establishment of a long-term primary murine glia culture expressing the human prion protein homozygous for methionine at codon 129, which allows in vitro propagation of Creutzfeldt–Jakob disease (CJD) prions (variant CJD (vCJD) and sporadic CJD (sCJD) type MM2). Prion propagation could be detected by Western blotting of pathological proteinase K-resistant prion protein (PrPSc) from 120 days post exposure. The accumulation of PrPSc could be intensified by adding a cationic lipid mixture to the infectious brain homogenate at the time of infection. Stable propagation of human prions in a long-term murine glia cell culture represents a new tool for future drug development and for mechanistic studies in the field of human prion biology. In addition, our cell model can reduce the need for bioassays with human prions and thereby contributes to further implementation of the 3R principles aiming at replacement, reduction and refinement of animal experiments

Endogene neuronale Vorläuferzellen unterdrücken das Wachstum von Glioblastomen

GesamtdissertationNeural precursor cells (NPCs) migrate towards glioblastoma in vivo and in vitro. They are attracted by glioma cells independent of other cell types or surrounding tissue. Young animals display prolonged survival after glioma inoculation compared to older animals due to the larger amount of precursors, which accumulate around the tumour. Young animals are naturally equipped with a greater number of NPCs. Additionally subventricular proliferation is even more restrained by the presence of a tumour only in adult animals. This further reduction of dividing precursors in adult mice solely refers to diminished proliferation rates since whole cell number and cell death rate was not affected by glioblastoma. Survival times of old animals can be aligned to the one of young mice by applying exogenous precursor cells. Proliferative capacity of NPCs is determined by the age of the subventricular zone and is an intrinsic and stable attribute. Neural precursors as well as NPC-conditioned medium directly induce glioma cell death. The transcription factor activating transcription factor-3 (ATF-3) is necessary and sufficient for the induction of cell death. Differential gene expression and morphological changes after administration of NPC-conditioned medium point to glioma cell death induced by endoplasmic reticulum stress.Neuronale Vorläuferzellen migrieren spezifisch zu Glioblastomen in vivo und in vitro. Dieser Prozess findet unabhängig von anderen Zelltypen oder umgebendem Gewebe statt. Junge Mäuse verfügen nach Inokulierung von Gliomzellen über eine längere Überlebenszeit im Vergleich zu adulten Tieren. Dies lässt sich auf die erhöhte Anzahl von Vorläuferzellen, die um den Tumor herum akkumulieren, zurückführen. Junge Tiere besitzen von Natur aus eine höhere Anzahl von neuronalen Vorläuferzellen. Dazu kommt, dass die subventrikuläre Proliferation nur in adulten Tieren zusätzlich durch den Tumor negativ beeinflusst wird. Diese Reduktion von sich teilenden subventrikulären Vorläuferzellen in adulten Mäusen beruht ausschließlich auf einer verminderten Proliferationsrate da sowohl Gesamtzellzahl und Zelltodrate vom Tumor unbeeinflußt blieben. Es zeigte sich, dass adulte Tiere nach Gabe von exogenen Vorläuferzellen die Überlebenszeit junger Tiere erreichen. Das proliferative Potential von neuronalen Vorläuferzellen wird durch das Alter der subventrikulären Zone determiniert und stellt eine intrinsische und stabile Eigenschaft dar. Neuronale Vorläuferzellen sowie Vorläuferzell-konditioniertes Medium induzieren Gliomzelltod unabhängig von äußeren Faktoren in vitro. Der Transkriptionsfaktor activating transcription factor-3 (ATF-3) ist für die Induktion von Gliomzelltod notwendig und hinreichend. Differentielle Genexpression und Morphologieänderung in Gliomzellen, induziert durch Vorläuferzell-konditioniertes Medium, lassen Zelltod durch endoplasmatischen Stress vermuten