Acoustic driven flow and lattice Boltzmann simulations to study cell adhesion in biofunctionalized ��-fluidic channels with complex geometry

Accurately mimicking the complexity of microvascular systems calls for a technology which can accommodate particularly small sample volumes while retaining a large degree of freedom in channel geometry and keeping the price considerably low to allow for high throughput experiments. Here, we demonstrate that the use of surface acoustic wave driven microfluidics systems successfully allows the study of the interrelation between melanoma cell adhesion, the matrix protein collagen type I, the blood clotting factor von Willebrand factor (vWF), and microfluidic channel geometry. The versatility of the tool presented enables us to examine cell adhesion under flow in straight and bifurcated microfluidic channels in the presence of different protein coatings. We show that the addition of vWF tremendously increases (up to tenfold) the adhesion of melanoma cells even under fairly low shear flow conditions. This effect is altered in the presence of bifurcated channels demonstrating the importance of an elaborate hydrodynamic analysis to differentiate between physical and biological effects. Therefore, computer simulations have been performed along with the experiments to reveal the entire flow profile in the channel. We conclude that a combination of theory and experiment will lead to a consistent explanation of cell adhesion, and will optimize the potential of microfluidic experiments to further unravel the relation between blood clotting factors, cell adhesion molecules, cancer cell spreading, and the hydrodynamic conditions in our microcirculatory system.     

Biochemistry in Wartime: The Life and Lessons of Adolf Butenandt, 1936–1946

This essay discusses the wartime work of one of the world’s leading biochemists, the Nobel Prize winner, Adolf Butenandt. It describes the influence of the war on Butenandt’s Institute, and considers his role as a representative figure in the collusion of science, government, and the military in Nazi Germany.Achim Trunk is a biologist and historian who specializes in the history of the life sciences. He studied at the University of Cologne, and now works at the Berlin-Brandenburg Academy of Science, where he is editing the scientific and medical papers of Gottfried Wilhelm Leibniz. Between 2001 and 2004, he was a member of the Berlin team that studied the history of the Kaiser Wilhelm Society during National Socialism. As part of that work, he coordinated the working party on Adolf Butenandt.     

Higher Education Supported by New Technologies at the Technical University of Dresden—Problems and Initiatives

This article summarizes the technical efforts and scientific experience that have been recognized as essential for the introduction of multimedia technologies for innovative teaching and learning at the Technical University of Dresden. Beginning with conventional standards, the most important media types are discussed. Important criteria for the development of multimedia tools are investigated. Finally, the first results of a pilot project of teleteaching are reported. This article emphasizes that new didactic and psychological studies are of the same level of importance for learning success as is technological development. Therefore, the strategy envisaged does not aim at developing the virtual university in its purest form but at the enrichment of the contemporary university by innovative elements that preserve the living contact between teachers and students.     

Neue Reitsportmotive jenseits des klassischen Turniersports

While the traditional equestrian disciplines of dressage and show jumping are losing members, other equestrian sports have become established in Germany and are enjoying increasing popularity. This empirical study examines the background behind this trend. A total of 1,814 horse riders were asked about their motives for riding. By applying factor and cluster analysis, a typology of riders was developed in order to reveal differences in motives between these groups. The performance-orientated riders are more represented in the classic equestrian disciplines, while the newer equestrian disciplines are mostly dominated by motives of pleasure. Overall, there is a clear trend towards more relaxation, recreation and self-fulfillment in equestrian sports. The desire to achieve success and to compete with others in one’s leisure time only remains important for a small proportion of riders. Therefore, riding clubs must try to balance the demands of performance-oriented and leisure riders and apply target group marketing to expand and to secure their member base.     

Persistence of innovation: Discriminating between types of innovation and sources of state dependence

This paper advances current research on the persistence of innovation drawing on a panel data set constructed from three waves of the German part of the Community Innovation Survey covering the time span from 2002 to 2008 (i.e., CIS IV, CIS 2007, and CIS 2009). We explore persistence patterns for various types of innovation (i.e., organizational, product and process innovation) and allowing for the moderating impact of firm-level characteristics. We use the ascertained patterns of persistence to comparatively evaluate various sources (and underlying theoretical accounts) of state dependence.     

Hematocrit and flow rate regulate the adhesion of platelets to von Willebrand factor

Primary hemostasis and blood clotting is known to be influenced by the red blood cell volume fraction (hematocrit) in blood. Depressed or elevated levels of red blood cells can lead to vascular perfusion problems ranging from bleeding to thrombus formation. The early stage of hemostasis and thus blood clotting in all vessel sections from the arterial to the venous system involves the adhesion of platelets to von Willebrand factor. Here we present experimental and theoretical results showing that the adhesion probability of platelets to von Willebrand factor is strongly and nonlinearly dependent on hematocrit and flow rate. Interestingly, the actual binding forces are not markedly different, which suggest that the origin of such behavior is in the distribution of platelets. Using hydrodynamic simulations of a simple model, we explicitly show that the higher the hematocrit and the flow rate, the larger the amount of platelets residing close to the wall. Our simulation results, which are in excellent agreement with the experimental observations, explain why such phenomena occur. We believe that the nonhomogeneous red blood cell distribution as well as the shear dependent hydrodynamic interaction is key for the accumulation of platelets on the vessel wall. The work we present here is an important step forward from our earlier work on single molecules and extends into the collective cellular behavior of whole blood. It sheds new light on the correlation between hematocrit and the initial steps in hemostasis and thrombosis, and outlines advances for the treatment of vascular diseases associated with high levels of red blood cells. These results are not only highly relevant for the field of hemostasis and the physics of blood clotting but are also of powerful impact in applied science most obviously in drug delivery and colloidal science.     

Circulating but not immobilized N-deglycosylated von Willebrand factor increases platelet adhesion under flow conditions

The role of von Willebrand factor (VWF) as a shear stress activated platelet adhesive has been related to a coiled-elongated shape conformation. The forces dominating this transition have been suggested to be controlled by the proteins polymeric architecture. However, the fact that 20% of VWF molecular weight originates from glycan moieties has so far been neglected in these calculations. In this study, we present a systematic experimental investigation on the role of N-glycosylation for VWF mediated platelet adhesion under flow. A microfluidic flow chamber with a stenotic compartment that allows one to mimic various physiological flow conditions was designed for the efficient analysis of the adhesion spectrum. Surprisingly, we found an increase in platelet adhesion with elevated shear rate, both qualitatively and quantitatively fully conserved when N-deglycosylated VWF (N-deg-VWF) instead of VWF was immobilized in the microfluidic channel. This has been demonstrated consistently over four orders of magnitude in shear rate. In contrast, when N-deg-VWF was added to the supernatant, an increase in adhesion rate by a factor of two was detected compared to the addition of wild-type VWF. It appears that once immobilized, the role of glycans is at least modified if not—as found here for the case of adhesion—negated. These findings strengthen the physical impact of the circulating polymer on shear dependent platelet adhesion events. At present, there is no theoretical explanation for an increase in platelet adhesion to VWF in the absence of its N-glycans. However, our data indicate that the effective solubility of the protein and hence its shape or conformation may be altered by the degree of glycosylation and is therefore a good candidate for modifying the forces required to uncoil this biopolymer.     

Motivational patterns as an instrument for predicting success in promising young football players

Psychological characteristics are crucial to identifying talents, which is why these are being incorporated in today’s multidimensional talent models. In addition to multidimensionality, talent studies are increasingly drawing on holistic theories of development, leading to the use of person-oriented approaches. The present study adopts such an approach by looking at the influence that motivational characteristics have on the development of performance, in a person-oriented way. For this purpose, it looks at how the constructs achievement motive, achievement goal orientation and self-determination interact with one another, what patterns they form and how these patterns are linked to subsequent sports success. Ninety-seven top young football players were questioned twice. Another year later, it was enquired which of these players had been selected for the U15 national team. At both measuring points, four patterns were identified, which displayed a high degree of structural and individual stability. As expected, the highly intrinsically achievement-oriented players were significantly more likely to move up into the U15 national team. The results point to the importance of favourable patterns of motivational variables in the form of specific types, for medium-term performance development among promising football talents, and thus provide valuable clues for the selection and promotion of those.