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End date: 2019 × Start date: 2019 × DDC: 570 × Type: Text × Publisher: Amsterdam : Elsevier ×

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Now showing 1 - 5 of 5
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    Surviving the surf: The tribomechanical properties of the periostracum of Mytilus sp
    (Amsterdam : Elsevier, 2014) Wählisch, Felix C.; Peter, Nicolas J.; Torrents Abad, Oscar; Oliveira, Mariana V.G.; Schneider, Andreas S.; Schmahl, Wolfgang; Griesshaber, Erika; Bennewitz, Roland
    We investigated the friction and wear behavior as well as the mechanical properties of the periostracum of Mytilus sp. Tribological properties were determined with a reciprocal sliding microtribometer, while mechanical characterization was performed using a nanoindenter. Measurements were performed in dry and wet conditions. On the dry periostracum we found a low friction coefficient of 0.078 ± 0.007 on the young parts and a higher one of 0.63 ± 0.02 on the old parts of the shell. Under wet, saline, conditions we only observed one average coefficient of friction of 0.37 ± 0.01. Microscopic ex situ analysis indicated that dry periostracum wore rather rapidly by plowing and fatigue, while it exhibited a high wear resistance when immersed in salt water. The Young’s modulus and hardness of the periostracum were also investigated in both dry and wet conditions. Under dry conditions the Young’s modulus of the periostracum was 8 ± 3 GPa, while under wet conditions it was 0.21 ± 0.05 GPa. The hardness of dry periostracum samples was 353 ± 127 MPa, whereas the hardness of wet samples was 5 ± 2 MPa. It was found that, in the wet state, viscous behavior plays a significant role in the mechanical response of the periostracum. Our results strongly indicate that the periostracum can provide an important contribution to the overall wear resistance of Mytilus sp. shell.
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    The mTOR and PP2A pathways regulate PHD2 phosphorylation to Fine-Tune HIF1α levels and colorectal cancer cell survival under hypoxia
    (Amsterdam : Elsevier, 2017) Di Conza, Giusy; Cafarello, Sarah Trusso; Loroch, Stefan; Mennerich, Daniela; Deschoemaeker, Sofie; Di Matteo, Mario; Ehling, Manuel; Gevaert, Kris; Prenen, Hans; Zahedi, Rene Peiman; Sickmann, Albert; Kietzmann, Thomas; Moretti, Fabiola; Mazzone, Massimiliano
    Oxygen-dependent HIF1α hydroxylation and degradation are strictly controlled by PHD2. In hypoxia, HIF1α partly escapes degradation because of low oxygen availability. Here, we show that PHD2 is phosphorylated on serine 125 (S125) by the mechanistic target of rapamycin (mTOR) downstream kinase P70S6K and that this phosphorylation increases its ability to degrade HIF1α. mTOR blockade in hypoxia by REDD1 restrains P70S6K and unleashes PP2A phosphatase activity. Through its regulatory subunit B55α, PP2A directly dephosphorylates PHD2 on S125, resulting in a further reduction of PHD2 activity that ultimately boosts HIF1α accumulation. These events promote autophagy-mediated cell survival in colorectal cancer (CRC) cells. B55α knockdown blocks neoplastic growth of CRC cells in vitro and in vivo in a PHD2-dependent manner. In patients, CRC tissue expresses higher levels of REDD1, B55α, and HIF1α but has lower phospho-S125 PHD2 compared with a healthy colon. Our data disclose a mechanism of PHD2 regulation that involves the mTOR and PP2A pathways and controls tumor growth.
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    Datasets from a vapor diffusion mineral precipitation protocol for Dictyostelium stalks
    (Amsterdam : Elsevier, 2016) Eder, Magdalena; Muth, Christina; Weiss, Ingrid M.
    Datasets from a slow carbonate vapor diffusion and mineral precipitation protocol for Dictyostelium ECM and cellulose stalks show examples for composite materials obtained by an in vitro approach, which differs substantially from the in vivo approach reported in The Journal of Structural Biology, doi: 10.1016/j.jsb.2016.03.015 [1]. Methods for obtaining the datasets include bright field transmitted light microscopy, fluorescence microscopy, LC-PolScope birefringence microscopy, variable pressure scanning electron microscopy (VP-SEM/ESEM), and Raman imaging spectroscopy.
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    Gli protein activity is controlled by multisite phosphorylation in vertebrate hedgehog signaling
    (Amsterdam : Elsevier, 2013) Niewiadomski, Pawel; Kong, Jennifer H.; Ahrends, Robert; Ma, Yan; Humke, Eric W.; Khan, Sohini; Teruel, Mary N.; Novitch, Bennett G.; Rohatgi, Rajat
    Gli proteins are transcriptional effectors of the Hedgehog (Hh) pathway in both normal development and cancer. We describe a program of multisite phosphorylation that regulates the conversion of Gli proteins into transcriptional activators. In the absence of Hh ligands, Gli activity is restrained by the direct phosphorylation of six conserved serine residues by protein kinase A (PKA), a master negative regulator of the Hh pathway. Activation of signaling leads to a global remodeling of the Gli phosphorylation landscape: the PKA target sites become dephosphorylated, while a second cluster of sites undergoes phosphorylation. The pattern of Gli phosphorylation can regulate Gli transcriptional activity in a graded fashion, suggesting a phosphorylation-based mechanism for how a gradient of Hh signaling in a morphogenetic field can be converted into a gradient of transcriptional activity.
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    Bifunctional hydrogels containing the laminin motif IKVAV promote neurogenesis
    (Amsterdam : Elsevier, 2017) Farrukh, Aleeza; Ortega, Felipe; Fan, Wenqiang; Marichal, Nicolás; Paez, Julieta I.; Berninger, Benedikt; del Campo, Aránzazu; Salierno, Marcelo J.
    Engineering of biomaterials with specific biological properties has gained momentum as a means to control stem cell behavior. Here, we address the effect of bifunctionalized hydrogels comprising polylysine (PL) and a 19-mer peptide containing the laminin motif IKVAV (IKVAV) on embryonic and adult neuronal progenitor cells under different stiffness regimes. Neuronal differentiation of embryonic and adult neural progenitors was accelerated by adjusting the gel stiffness to 2 kPa and 20 kPa, respectively.While gels containing IKVAV or PL alone failed to support long-term cell adhesion, in bifunctional gels, IKVAV synergized with PL to promote differentiation and formation of focal adhesions containing b1-integrin in embryonic cortical neurons. Furthermore, in adult neural stem cell culture, bifunctionalized gels promoted neurogenesis via the expansion of neurogenic clones. These data highlight the potential of synthetic matrices to steer stem and progenitor cell behavior via defined mechano-adhesive properties.