Dynamics of Cell Shape and Forces on Micropatterned Substrates Predicted by a Cellular Potts Model

Micropatterned substrates are often used to standardize cell experiments and to quantitatively study the relation between cell shape and function. Moreover, they are increasingly used in combination with traction force microscopy on soft elastic substrates. To predict the dynamics and steady states of cell shape and forces without any a priori knowledge of how the cell will spread on a given micropattern, here we extend earlier formulations of the two-dimensional cellular Potts model. The third dimension is treated as an area reservoir for spreading. To account for local contour reinforcement by peripheral bundles, we augment the cellular Potts model by elements of the tension-elasticity model. We first parameterize our model and show that it accounts for momentum conservation. We then demonstrate that it is in good agreement with experimental data for shape, spreading dynamics, and traction force patterns of cells on micropatterned substrates. We finally predict shapes and forces for micropatterns that have not yet been experimentally studied.Comment: Revtex, 32 pages, 11 PDF figures, to appear in Biophysical Journa

Stadt, Land, Berg. Vom Zusammenspiel von Dialektwahrnehmung und Topographie

In traditional dialectology, prominent geographical conditions are particularly made responsible for linguistic divergence between neighboring dialect areas (e. g. rivers, mountain ranges, etc.). Also modern national borders, territories of the Middle Ages or even older borders between tribal areas are made responsible as factors which consider linguistic areas as “mirror pictures of history” (Bach 1950: 31, translation: CS). Geographical as well as political borders seem to function as points of orientation that speakers use for constructing their cognitive surroundings and which consequently can result in linguistic divergence. In our contribution, we want to focus on the question of how the topographic nature of land-scapes influences the mental construction of linguistic areas by lay speakers. For pursuing this question, we will discuss results from German dialect areas that cover a broad range of different topographic landscape forms. The analyzed areas are located in the utter southwest of Germany (characterized by flat lands along the Rhine valley and low mountain ranges of the Black Forest) and in South Tyrol in the very north of Italy (characterized by mountains and deep valley cuttings). In our contribution, we will argue that speakers in their subjective dialect perception orient themselves toward national borders and topographically prominent points. With regard to topography primarily valleys are used as eponyms for subjective dialect areas

Dynamics of Cell Ensembles on Adhesive Micropatterns: Bridging the Gap between Single Cell Spreading and Collective Cell Migration

The collective dynamics of multicellular systems arise from the interplay of a few fundamental elements: growth, division and apoptosis of single cells; their mechanical and adhesive interactions with neighboring cells and the extracellular matrix; and the tendency of polarized cells to move. Micropatterned substrates are increasingly used to dissect the relative roles of these fundamental processes and to control the resulting dynamics. Here we show that a unifying computational framework based on the cellular Potts model can describe the experimentally observed cell dynamics over all relevant length scales. For single cells, the model correctly predicts the statistical distribution of the orientation of the cell division axis as well as the final organisation of the two daughters on a large range of micropatterns, including those situations in which a stable configuration is not achieved and rotation ensues. Large ensembles migrating in heterogeneous environments form non-adhesive regions of inward-curved arcs like in epithelial bridge formation. Collective migration leads to swirl formation with variations in cell area as observed experimentally. In each case, we also use our model to predict cell dynamics on patterns that have not been studied before

Die Osteotomie nach Austin - klinische und radiologische Ergebnisse nach Operation

Nachuntersuchung von Patienten, die mit der Osteotomie nach Austin (Chevron-Osteotomie) zur Korrektur der Hallux-valgus-Deformität operiert wurden. Die Ergebnisse wurden anhand einer retrospektiven Studie mit einem minimalen Nachuntersuchungszeitraum von 2 Jahren analysiert