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12 octobre 2018: 1 événement

Séminaire des doctorants

  • Séminaires Doctorants

    Vendredi 12 octobre 16:00-17:00 - François Yaya / Valentin Gerard

    Séminaires Doctorants

    Résumé :

    • François Yaya :
      Optical tweezers recently received more attention as this technology was rewarded with the Nobel prize in 2018. We will have a look at how light can move objects and what is the physical secret behind it. Arthur Ashkin’s discovery gave rise to multiple applications in the field of biophysics. This is where red blood cells (RBCs) come into play. RBCs are very deformable objects flowing in our body from large vessels to small capillaries. They swim in a medium containing proteins also known as plasma. Interactions of different natures (hydrodynamic / adhesive) take place and cells form aggregates called “rouleaux”. Those stacks of cells can also separate under shear stress. Optical tweezers allow us to work at a single cell level and measure very tiny forces within a few piconewtons range. Experimentally, we investigate the (dis)aggregation of a pair of RBCs using optical traps. This enables us to grasp hints about the underlying mechanisms of RBCs aggregation.
      https://www-liphy.ujf-grenoble.fr/IMG/png/presentation_francois.png
    • Artur Ruppel :
      Forces are fundamental in biological processes. Whereas the implication of forces in processes like cell division and cell migration are obvious, the importance of mechanical signals in regulatory processes e.g. in morphogenesis has long been overlooked. Whereas many of the molecular mechanisms for force generation, sensing and transduction are already well described, it is less known how these forces are used to regulate complex biological processes and how forces are transmitted from one cell to another. These kind of questions could long time not be adressed, since an appropriate tool for modulating cell-cell forces with high spatiotemporal resolution was missing. With the development of optogenetic tools, with which cell contraction can be induced by stimulating the cell with light, these questions can now be adressed. We propose a minimalistic tissue model consisting of two epithelial cells (MDCK) with standardized geometry, achieved through the use of micropatterns on a soft substrate, to study force transmission in epithelial tissues.
      Traction force microscopy is used to measure the cellular forces in the model in response to the optogenetic stimulation. In this work, we established the necessary parameters and verified the chosen tools for planned optogenetic experiments and obtained some preliminary results regarding force transmission between the two cells. We also developed a first, simplistic theoretical model aiming to explain the observed results.

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