@article{BarbosaPfannesThevesWegneretal.2012,
  author    = {Barbosa Pfannes, Eva Katharina and Theves, Matthias and Wegner, Christian and Beta, Carsten},
  title     = {Impact of the carbazole derivative wiskostatin on mechanical stability and dynamics of motile cells},
  series = {JOURNAL OF MUSCLE RESEARCH AND CELL MOTILITY},
  volume    = {33},
  journal   = {JOURNAL OF MUSCLE RESEARCH AND CELL MOTILITY},
  number    = {2},
  publisher = {SPRINGER},
  address   = {DORDRECHT},
  issn      = {0142-4319},
  doi       = {10.1007/s10974-012-9287-8},
  pages     = {95 -- 106},
  year      = {2012},
  abstract  = {Many essential functions in eukaryotic cells like phagocytosis, division, and motility rely on the dynamical properties of the actin cytoskeleton. A central player in the actin system is the Arp2/3 complex. Its activity is controlled by members of the WASP (Wiskott-Aldrich syndrome protein) family. In this work, we investigated the effect of the carbazole derivative wiskostatin, a recently identified N-WASP inhibitor, on actin-driven processes in motile cells of the social ameba . Drug-treated cells exhibited an altered morphology and strongly reduced pseudopod formation. However, TIRF microscopy images revealed that the overall cortical network structure remained intact. We probed the mechanical stability of wiskostatin-treated cells using a microfluidic device. While the total amount of F-actin in the cells remained constant, their stiffness was strongly reduced. Furthermore, wiskostatin treatment enhanced the resistance to fluid shear stress, while spontaneous motility as well as chemotactic motion in gradients of cAMP were reduced. Our results suggest that wiskostatin affects the mechanical integrity of the actin cortex so that its rigidity is reduced and actin-driven force generation is impaired.},
  language  = {en}
}
@article{BarbosaPfannesAnielskiGerhardtetal.2013,
  author    = {Barbosa Pfannes, Eva Katharina and Anielski, Alexander and Gerhardt, Matthias and Beta, Carsten},
  title     = {Intracellular photoactivation of caged cGMP induces myosin II and actin responses in motile cells},
  series = {Integrative biology},
  volume    = {5},
  journal   = {Integrative biology},
  number    = {12},
  publisher = {Royal Society of Chemistry},
  address   = {Cambridge},
  issn      = {1757-9694},
  doi       = {10.1039/c3ib40109j},
  pages     = {1456 -- 1463},
  year      = {2013},
  abstract  = {Cyclic GMP (cGMP) is a ubiquitous second messenger in eukaryotic cells. It is assumed to regulate the association of myosin II with the cytoskeleton of motile cells. When cells of the social amoeba Dictyostelium discoideum are exposed to chemoattractants or to increased osmotic stress, intracellular cGMP levels rise, preceding the accumulation of myosin II in the cell cortex. To directly investigate the impact of intracellular cGMP on cytoskeletal dynamics in a living cell, we released cGMP inside the cell by laser-induced photo-cleavage of a caged precursor. With this approach, we could directly show in a live cell experiment that an increase in intracellular cGMP indeed induces myosin II to accumulate in the cortex. Unexpectedly, we observed for the first time that also the amount of filamentous actin in the cell cortex increases upon a rise in the cGMP concentration, independently of cAMP receptor activation and signaling. We discuss our results in the light of recent work on the cGMP signaling pathway and suggest possible links between cGMP signaling and the actin system.},
  language  = {en}
}
@article{AnielskiBarbosaPfannesBeta2017,
  author    = {Anielski, Alexander and Barbosa Pfannes, Eva Katharina and Beta, Carsten},
  title     = {Adaptive microfluidic gradient generator for quantitative chemotaxis experiments},
  series = {Review of scientific instruments : a monthly journal devoted to scientific instruments, apparatus, and techniques},
  volume    = {88},
  journal   = {Review of scientific instruments : a monthly journal devoted to scientific instruments, apparatus, and techniques},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {0034-6748},
  doi       = {10.1063/1.4978535},
  pages     = {10},
  year      = {2017},
  abstract  = {Chemotactic motion in a chemical gradient is an essential cellular function that controls many processes in the living world. For a better understanding and more detailed modelling of the underlying mechanisms of chemotaxis, quantitative investigations in controlled environments are needed. We developed a setup that allows us to separately address the dependencies of the chemotactic motion on the average background concentration and on the gradient steepness of the chemoattractant. In particular, both the background concentration and the gradient steepness can be kept constant at the position of the cell while it moves along in the gradient direction. This is achieved by generating a well-defined chemoattractant gradient using flow photolysis. In this approach, the chemoattractant is released by a light-induced reaction from a caged precursor in a microfluidic flow chamber upstream of the cell. The flow photolysis approach is combined with an automated real-time cell tracker that determines changes in the cell position and triggers movement of the microscope stage such that the cell motion is compensated and the cell remains at the same position in the gradient profile. The gradient profile can be either determined experimentally using a caged fluorescent dye or may be alternatively determined by numerical solutions of the corresponding physical model. To demonstrate the function of this adaptive microfluidic gradient generator, we compare the chemotactic motion of Dictyostelium discoideum cells in a static gradient and in a gradient that adapts to the position of the moving cell. Published by AIP Publishing.},
  language  = {en}
}