Showing papers by "University of Luxembourg published in 1999"

Psychological and physiological reactivity to stress: an experimental study on bulimic patients, restrained eaters and controls.

Abstract: Background: Binge eating behavior in bulimic patients is thought to play a crucial role in the regulation of psychophysiological arousal in stressful situations. Previous results su

Contributions of Leukemia Inhibitory Factor Receptor and Oncostatin M Receptor to Signal Transduction in Heterodimeric Complexes with Glycoprotein 130

Abstract: Leukemia inhibitory factor (LIF), cardiotrophin-1, ciliary neurotrophic factor, and oncostatin M (OSM) lead to heterodimerization of LIF receptor (LIFR) or the OSM-specific receptor (OSMR) with glycoprotein (gp) 130, the common receptor subunit for IL-6-type cytokines. Thereby intracellular signaling via Janus kinases (Jaks) and STAT transcription factors is initiated. We investigated the contributions of LIFR and OSMR to signal transduction in the context of heterodimers with gp130. Chimeric receptors based on the extracellular parts of the IL-5R α- and β-chains were generated, allowing the induced heterodimerization of two different cytoplasmic tails. Our studies demonstrate that upon heterodimerization with the gp130 cytoplasmic region, the cytoplasmic parts of both LIFR and OSMR were critical for activation of an acute phase protein promoter in HepG2 hepatoma cells. The membrane-proximal region of LIFR or OSMR was crucial for the ability of such receptor complexes to induce DNA binding of STAT1 and STAT3 in COS-7 cells. Membrane-distal regions of LIFR and OSMR contributed to STAT activation even in the absence of gp130 STAT recruitment sites. We further show that the Janus kinases Jak1 and Jak2 constitutively associated with receptor constructs containing the cytoplasmic part of LIFR, OSMR, or gp130, respectively. Homodimers of the LIFR or OSMR cytoplasmic regions did not elicit responses in COS-7 cells but did in HepG2 cells and in MCF-7 breast carcinoma cells. Thus, in spite of extensive functional similarities, differential signaling abilities of gp130, LIFR, and OSMR may become evident in a cell-type-specific manner.

Quantitative measurement of proteins by western blotting with Cy5-coupled secondary antibodies.

Abstract: The concentration of proteins in cells is an important parameter that determines how a protein will interact with other proteins or pharmacological agents. Recent developments in Western blotting techniques have now made this a method of choice to measure protein concentration in complex solutions such as total cell extracts. We show that detection of Cy5-coupled secondary antibodies by PhosphorImager analysis produces signals that approach linearity with respect to protein concentration over a 20-fold range. We used this technique to estimate cellular levels of zyxin, which is an important protein component of the actin cytoskeleton in mammalian cells. By producing specific protein standards based on sequences that are available from public databases, it is now possible to estimate the concentration of almost any protein by this technique.

Berezin-Toeplitz quantization and Berezin symbols for arbitrary compact Kähler manifolds

Abstract: For phase-space manifolds which are compact Kahler manifolds relations between the Berezin-Toeplitz quantization and the quantization with the help of Berezin's coherent states and symbols are studied. First the results on the Berezin-Toeplitz quantization of arbitrary compact Kahler manifolds due to Bordemann, Meinrenken and Schlichenmaier are recalled. It is shown that the covariant symbol map is adjoint to the Toeplitz map. The Berezin transform for compact Kahler manifolds is discussed.

Induction of Egr-1 mRNA and protein by endothelin 1, angiotensin II and norepinephrine in neonatal cardiac myocytes.

Abstract: The early growth response gene Egr-1 is a nuclear transcription factor known to serve as an intermediary in a broad range of signal transduction processes. Recent studies have assigned Egr-1 a new role as an amplifier of gene expression. Egr-1 mRNA is expressed in the myocardium and is rapidly induced in response to hypertrophic stimuli. However, induction of the Egr-1 protein has not yet been demonstrated in the myocardium; on the other hand, in skeletal muscle cells we have shown translational regulation of Egr-1. To further investigate the role of Egr-1 in the regulatory mechanisms of a variety of signal transduction processes we have therefore asked whether bona fide hypertrophic stimuli induce Egr-1 protein subsequently to its mRNA in neonatal rat cardiomyocytes or whether translational block occurs. In confocal laser studies the Egr-1 protein was nuclearly localized. Norepinephrine (NE, 2 μM), angiotensin II (AII, 0.1 μM), and endothelin 1 (E1, 0.1 μM) each induced the Egr-1 mRNA 6-8 fold and the Egr-1 protein 3-5 fold (n = 3, p < 0.01). Therefore, in contrast to skeletal muscle cells, these stimuli increased Egr-1 mRNA and protein levels. These results point further to the role of Egr-1 as a possible amplifier of signal transduction in the myocardium.

Appearance-Based Robot Localization

Abstract: In this paper we present our work on robot localization using images from an omni-directional camera. A probabilistic framework is used, and diierent criteria for the evaluation of the localization method are presented. Experiments with real data from a real robot have been carried out. We discuss our approach in the context of dynamically changing environments .

Soziale Netze im Alter: Selektivität in der Netzwerkgestaltung, wahrgenommene Qualität der Sozialbeziehungen und Affekt

Abstract: Zusammenfassung. In dem vorliegenden Beitrag wurden Vorhersagen bezuglich der Netzwerkkomposition im Alter aus der sozioemotionalen Selektivitatstheorie abgeleitet und einer empirischen Prufung unterzogen. Im einem querschnittlichen Altersgruppenvergleich wurde zum einen gepruft, ob altere Menschen durch Selektivitat in der Netzwerkgestaltung zu beschreiben sind und ihr soziales Netz einen vergleichsweise hoheren Anteil emotional nahestehender Personen aufweist. Zum anderen wurde in Erweiterung zu bisherigen Uberprufungen der Theorie untersucht, inwieweit das soziale Netz im Alter neben dem Kriterium der emotionalen Nahe durch positive und negative Beziehungsaspekte zu beschreiben ist. In einem letzten Schritt wurden die Effekte der Selektivitat und des wahrgenommenen Ausmases an positiven und negativen Beziehungsaspekten auf die Haufigkeit von positivem und negativem Affekt uberpruft. Die Befunde bestatigen die bisherige Befundlage zur veranderten Netzwerkkomposition im Alter. Zudem konnte gezeigt werden...

Numerical Modelling of Tension Piles

Abstract: For determinations of the ultimate tension capacity of a piled foundation, often use is made of empirical relations between soil strength and skin friction. The disadvantage of these (analytical) methods is that they are in general not very accurate for most soil conditions. Therefore a numerical method for determination of the ultimate bearing capacity is presented here. Results were successively compared with actual test results which were measured during pile tests. It was found that the numerical model assessed the actual pile bearing capacity more closely than analytical models based on empirical calculation rules. Therefore lower factors of safety can be accepted. The behaviour of the (virtual) interface between pile and soil significantly influences the behaviour of the pile.

The alpha1-antichymotrypsin A-allele in German Parkinson disease patients.

Abstract: An increased frequency of the A-allele of the α1-antichymotrypsin (ACT) gene has been recently described in Japanese patients suffering from Parkinson disease (PD). In the present study, we have analyzed 62 German PD patients with regard to their ACT and APOE genotypes and com-pared them to 53 controls without clinical or pathological evidence of neurodegenerative disease. The A-allele frequency was 47% in PD patients compared to 54% in control cases excluding ACT as a major susceptibility factor for PD in the Caucasian population. Yet, ACT-A allele frequencies were significantly different (p < 0.001) between Japanese and German controls. Therefore, although our data do not suggest that the α1-ACT polymorphism is a significant risk factor for the development of PD, a consideration of differences in genetic background seems warranted when evaluating susceptibility factors for neurodegenerative disease.

Bismut type differentiation of semigroups.

Abstract: We present a unified approach to Bismut type differentiation formulas for heat semigroups on functions and forms. Both elliptic and hypoelliptic situations are considered. Nonlinear extensions apply to the case of harmonic maps between Riemannian manifolds and solutions to the nonlinear heat equation.

An information-theoretic localization criterion for robot map building

Abstract: In the process of robot map building, many diierent aspects of the problem must be taken into account, like the environment the robot moves in, the type of sensors it uses, the dimensionality of the measurements, etc. One fundamental issue becomes the extraction of relevant features from the raw measurements to be used by the robot for self-localization. Recently, a Bayesian lo-calization error formula was proposed to be used as an optimization criterion in a neural-network based non-linear feature extraction scheme. We derive in this paper an alternative criterion for robot localization that is based on information-theoretic concepts and that is more eecient to compute, and we compare with the localization error criterion. We discuss the case of linear projection with PCA and carry out an analysis thereof. Finally, we show experimental results for supervised data obtained by a real robot in a typical ooce environment.

Der Strukturwandel von Warenwirtschaft und Logistik und seine Bedeutung für die Stadtentwicklung.

Abstract: The paper focuses on the interaction between freight distribution, logistics and urban development processes. It is suggested that the role of cities is being transformed from that of a traditional point of goods-transshipment to a mere link in long-distance commodity chains. As a result of the introduction of new logistics concepts within companies, and depending on specific functional requirements, suburban and peripheral locations tend to be preferred locations of logistics centres and distribution functions. Thus far, the rationalisation of logistics and the locational behaviour of firms have had spatial impacts not only in terms of freight traffic, emissions and demand for space but also in terms of challenging traditional urban functions. Against this background further perspectives of urban development are discussed with respect to the spatial implications of modem logistics.