13:00-13:20 武石 直樹 Naoki Takeishi (Graduate School of Engineering Science, Osaka University)
Numerical analysis of the rheology of suspension of red blood cells
13:20-13:40 松井 翼 Tsubasa S. Matsui (Graduate School of Engineering Science, Osaka University)
Load-denpendent contractile properties of actin stress fibers
13:40-14:00 大谷 智仁 Tomohiro Otani (Graduate School of Engineering Science, Osaka University)
Computational beam model and applications for biomedical engineering
14:00-15:00 Mohammad R. K. Mofrad (Departments of Bioengineering and Mechanical Engineering, University of California Berkeley)
Molecular biomechanics and cellular mechanotransduction in health and disease
Speaker: 武石 直樹 Naoki Takeishi (Graduate School of Engineering Science, Osaka University)
Title: Numerical analysis of the rheology of suspension of red blood cells
Abstract: I present a numerical analysis of the rheology of a suspension of red blood cells (RBCs) in shear flow for a wide range of viscosity ratio between the internal and external fluid. The problem is solved by GPU computing, where the Lattice-Boltzmann method coupling with the finite element method are used. Using a stresslet, I show how the bulk suspension of rheology is sifted as increasing internal viscosity of RBCs, and discuss the relationship between the macroviscosity of blood and individual behavior of RBCs.
Speaker: 松井 翼 Tsubasa S. Matsui (Graduate School of Engineering Science, Osaka University)
Title: Load-denpendent contractile properties of actin stress fibers
Abstract: Actomyosin-based contractile forces play important roles in many aspects of cell physiology. Actin stress fibers (SFs) are the main components of intracellular force generators to transmit isometric tension to the extracellular matrix. While their shortening properties have been extensively investigated, isometric contractile properties intrinsic to SFs are still unclear. To comprehensively characterize the contractile properties of individual SFs, we established an in vitro manipulation system. SFs were extracted from cells using a hypotonic shock technique and isolated from the substrates using fine glass microneedles. SFs immediately contracted upon the addition of MgATP, while the rate of the contraction was steeply decreased once they bear a magnitude of tension. These results suggest that SFs are highly sensitive to external load, and they may be responsible for tension-induced immobilization of focal adhesions.
Speaker: 大谷 智仁 Tomohiro Otani (Graduate School of Engineering Science, Osaka University)
Title: Computational beam model and applications for biomedical engineering
Abstract: Mechanical analysis of a thin beam structure is one of fundamental and essential topics in a wide varieties of engineering. This presentation briefly introduces a computational model of three-dimensional beam with considering finite deformation and rotation for applications of biomedical engineering, especially for the medial support simulator of endovascular treatment.
Speaker: Mohammad R. K. Mofrad (Departments of Bioengineering and Mechanical Engineering, University of California Berkeley)
Title: Molecular biomechanics and cellular mechanotransduction in health and disease
Abstract: Living cells sense mechanical signals, and respond actively by changing their phenotype. This process, termed as cellular mechanotransduction, is mediated by a combination of biochemical and biophysical mechanisms via mechanically induced changes in the structure and function of specific molecules and molecular complexes. Our specific attention is on the role of three macromolecular systems in cellular mechanotransduction, namely the integrin-mediated focal adhesions bridging the cell with the extracellular matrix (ECM), and linkers of the nucleoskeleton and cytoskeleton (LINC complexes), and the nuclear pore complex (NPC) at the interface between the cytoplasm and nucleus. Focal adhesions are the immediate sites of cell interaction with the ECM, and as such they play a key role in mechanosensing and mechanotransduction at the edge of the cell. LINC complexes physically link the cytoskeleton and nucleoskeleton to regulate force transmission to the nucleus; their direct associations with focal adhesions through filamentous actin bundles results in ultrafast mechanotransduction. Nuclear pores could also play a role in the overall process of cellular mechanotransduction by exquisitely controlling the material transport in and out of the nucleus, thereby regulating gene expression and protein synthesis. In this seminar, I will present some of our recent efforts aimed at better understanding of these interconnected molecular systems in the context of cellular mechanotransduction.