An adult thymic stromal-cell suspension model for in vitro positive selection.

Presented here is a cell-suspension model for positive selection using thymocytes from alphabeta-TCR (H-2Db-restricted) transgenic mice specific to the lymphocytic choriomeningitis virus (LCMV) on a nonselecting MHC background (H-2d or TAP-1 -/-), cocultured with freshly isolated adult thymus stromal cells of the selecting MHC type. The thymic stromal cells alone induced positive selection of functional CD4- CD8+ cells whose kinetics and efficiency were enhanced by nominal peptide. Fibroblasts expressing the selecting MHC alone did not induce positive selection; however, together with nonselecting stroma and nominal peptide, there was inefficient positive. These results suggest multiple signaling in positive selection with selection events able to occur on multiple-cell types. The ease with which this model can be manipulated should greatly facilitate the resolution of the mechanisms of positive selection in normal and pathological states

Ректор ТПИ А. А. Воробьев - изобретатель электроимпульсного способа разрушения горных пород

Представлена история создания электроимпульсного способа разрушения горных пород ректором ТПИ А. А. Воробьевым

Wirkung und Wirkungsweise von Insulin-like Growth-factor-I auf das proliferative Wachstum neuroendokriner Tumorzellen am Beispiel der humanen Karzinoidzelllinie BON

Karzinoide sind neuroendokrine Tumoren des gastroenteropankreatischen Systems. Bis heute gibt es mit Ausnahme eines chirurgischen Eingriffes keine adäquate kurativeTherapiemöglichkeit. Die Expression des IGF-I-Rezeptors und von IGF-I konnte bei dieser Tumorart bereits nachgewiesen werden. Diese beiden Teile des IGF-Systems sind von besonderer Bedeutung für das Entstehen und das Erhalten verschiedener Tumorarten und gelten heute als sehr interessanter Ansatzpunkt für die Erforschung neuer Therapiestrategien. Ziel dieser Arbeit war es, am Beispiel der humanen Karzinoid-Zellinie BON, das proliferative Wachstum dieser Tumorart unter dem Einfluß von IGF-I zu untersuchen und mögliche, für die Signalvermittlung verantwortliche Transduktionswege zu entschlüsseln. In einem ersten Schritt konnte durch Rezeptor-Bindungsstudien gezeigt werden, dass BON-Zellen einen funktionstüchtigen IGF-I-Rezeptor tragen. Im Radioimmunoassay wurde zudem die IGF-I-Synthese quantitativ nachgewiesen. Die Stimulation der Zellen mit IGF-I bewirkt eine deutliche und signifikante Steigerung des proliferativen Zellwachstums. In Versuchen mit den Hemmstoffen PD 98059 als spezifischer Inhibitor der MAP-Kinasen ERK1 und 2 sowie mit LY 294002 als selektiven PI-3Kinase-Inhibitor konnte darüber hinaus gezeigt werden, dass die Signalkaskaden dieser beiden Kinasefamilien für die Signaltransduktion nach Bindung von IGF-I an seinen Rezeptor von wesentlicher Bedeutung sind. Aus diesen Hemmungsversuchen ergeben sich zudem Hinweise für eine mögliche Verknüpfung beider Transduktionswege. Im MAP-Kinase-Assay wurden die Einflüsse auf die MAP-Kinase visualisiert. Abschließend wurde durch Transfektionsstudien mit einem IGF-I-Promotor die Bedeutungen beider Signaltransduktionswege auch auf die IGF-I-Produktion der BON-Zellen nachgewiesen. Zusammen mit dem beschriebenen quantitativen Nachweis von IGF-I ergeben sich damit deutliche Hinweise für einen auto- beziehungsweise parakrinen Wirkungsmechanismus dieses Peptides bei BON-Zellen. Das IGF-I-System stellt damit einen interessanten Ansatz für die Entwicklung neuer therapeutischer Strategien zur Behandlung neuroendokriner Tumoren des gastroenteropankreatischen Systems dar. Um das IGF-I-vermittelte Wachstum also zu unterbinden erscheinen mehrere Ansatzpunkte möglich: (1.) Auf der Ebene des Rezeptors durch Antagonisierung des IGF-I-Rezeptors, (2.) auf Cytoplasmaebene durch Unterbrechung der Signaltransduktionswege beziehungsweise Antagonisierung des autokrin sezernierten IGF-I oder (3.) auf Genebene durch Störung der IGF-I-Expression selbst

An Adult Thymic Stromal-Cell Suspension Model for in Vitro Positive Selection

Presented here is a cell-suspension model for positive selection using thymocytes from αβ-TCR (H-2Db-restricted) transgenic mice specific to the lymphocytic choriomeningitis virus (LCMV) on a nonselecting MHC background (H-2d or TAP-1 –/–), cocultured with freshly isolated adult thymus stromal cells of the selecting MHC type. The thymic stromal cells alone induced positive selection of functional CD4-CD8+ cells whose kinetics and efficiency were enhanced by nominal peptide. Fibroblasts expressing the selecting MHC alone did not induce positive selection; however, together with nonselecting stroma and nominal peptide, there was inefficient positive. These results suggest multiple signaling in positive selection with selection events able to occur on multiple-cell types. The ease with which this model can be manipulated should greatly facilitate the resolution of the mechanisms of positive selection in normal and pathological states

A cortisone sensitive CD3low subset of CD4+CD8− thymocytes represents an intermediate stage in intrathymic repertoire selection

Two populations of CD4 single positive (SP) thymocytes were found In transgenic mice bearing class l-restricted Mls-1a reactive (Vβ8.1) TCR genes in the absence of the restriction element. CD3high CD4 sp cells were deleted In the presence of Mls-15 and were cortisone resistant, whereas CD3low CD4 SP cells were not deleted In the presence of Mls-1* and were cortisone sensitive. Intravenous transfer of CD3low CD4 SP cells into nude mice resulted in significant peripheral expansion of these cells with apparent upregulation of CD3. These data Indicate that CD3low CD4 SP thymocytes represent an Intermediate stage In the transition from CDSlow double positive (DP) to CD3high SP thymocytes and raise the possibility that these cells may have undergone positive but not negative selection events (at least to Mls-1a). Furthermore the fact that CD3high DP thymocytes were also deleted by Mls-1a in these mice suggests strongly that sensitivity to Mls-1a deletion is dependent upon stage of thymic maturation (as revealed by TCR density) rather than CD4/CD8 phenotyp

QuaSI: Quantile Sparse Image Prior for Spatio-Temporal Denoising of Retinal OCT Data

Optical coherence tomography (OCT) enables high-resolution and non-invasive 3D imaging of the human retina but is inherently impaired by speckle noise. This paper introduces a spatio-temporal denoising algorithm for OCT data on a B-scan level using a novel quantile sparse image (QuaSI) prior. To remove speckle noise while preserving image structures of diagnostic relevance, we implement our QuaSI prior via median filter regularization coupled with a Huber data fidelity model in a variational approach. For efficient energy minimization, we develop an alternating direction method of multipliers (ADMM) scheme using a linearization of median filtering. Our spatio-temporal method can handle both, denoising of single B-scans and temporally consecutive B-scans, to gain volumetric OCT data with enhanced signal-to-noise ratio. Our algorithm based on 4 B-scans only achieved comparable performance to averaging 13 B-scans and outperformed other current denoising methods.Comment: submitted to MICCAI'1

A small ribosome-associated ncRNA globally inhibits translation by restricting ribosome dynamics

Ribosome-associated non-coding RNAs (rancRNAs) have been recognized as an emerging class of regulatory molecules capable of fine-tuning translation in all domains of life. RancRNAs are ideally suited for allowing a swift response to changing environments and are therefore considered pivotal during the first wave of stress adaptation. Previously, we identified an mRNA-derived 18 nucleotides long rancRNA (rancRNA_18) in Saccharomyces cerevisiae that rapidly downregulates protein synthesis during hyperosmotic stress. However, the molecular mechanism of action remained enigmatic. Here, we combine biochemical, genetic, transcriptome-wide and structural evidence, thus revealing rancRNA_18 as global translation inhibitor by targeting the E-site region of the large ribosomal subunit. Ribosomes carrying rancRNA_18 possess decreased affinity for A-site tRNA and impaired structural dynamics. Cumulatively, these discoveries reveal the mode of action of a rancRNA involved in modulating protein biosynthesis at a thus far unequalled precision