Yazar "Shreiber, David I" seçeneğine göre listele

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    Differentiation of reactive-like astrocytes cultured on nanofibrillar and comparative culture surfaces.
    (Nanomedicine, 2015) Tiryaki, Volkan; Ayres, Virginia M.; Ahmed, Ijaz; Shreiber, David I
    Aim: To investigate the directive importance of nanophysical properties on the morphological and protein expression responses of dibutyryladenosine cyclic monophosphate (dBcAMP)-treated cerebral cortical astrocytes in vitro. Materials & methods: Elasticity and work of adhesion characterizations of culture surfaces were performed using atomic force microscopy and combined with previous surface roughness and polarity results. The morphological and biochemical differentiation of dBcAMP-treated astrocytes cultured on promising nanofibrillar scaffolds and comparative culture surfaces were investigated by immunocytochemistry, colocalization, super resolution microscopy and atomic force microscopy. The dBcAMP-treated astrocyte responses were further compared with untreated astrocyte responses. Results & conclusion: Nanofibrillar scaffold properties were shown to reduce immunoreactivity responses while poly-l-lysine-functionalized Aclar® (Ted Pella Inc., CA, USA) properties were shown to induce responses reminiscent of glial scar formation. The comparison study indicated that directive cues may differ in wound-healing versus quiescent situations.
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    Nanofibrillar scaffolds induce preferential activation of Rho GTPases in cerebral cortical astrocytes
    (International Journal of Nanomedicine, 2012-07-12) Tiryaki, Volkan; Ayres, Virginia M.; Khan, Adeel A; Ahmed, Ijaz; Shreiber, David I; Meiners, Sally
    Cerebral cortical astrocyte responses to polyamide nanofibrillar scaffolds versus poly-L-lysine (PLL)-functionalized planar glass, unfunctionalized planar Aclar coverslips, and PLL-functionalized planar Aclar surfaces were investigated by atomic force microscopy and immunocytochemistry. The physical properties of the cell culture environments were evaluated using contact angle and surface roughness measurements and compared. Astrocyte morphological responses, including filopodia, lamellipodia, and stress fiber formation, and stellation were imaged using atomic force microscopy and phalloidin staining for F-actin. Activation of the corresponding Rho GTPase regulators was investigated using immunolabeling with Cdc42, Rac1, and RhoA. Astrocytes cultured on the nanofibrillar scaffolds showed a unique response that included stellation, cell–cell interactions by stellate processes, and evidence of depression of RhoA. The results support the hypothesis that the extracellular environment can trigger preferential activation of members of the Rho GTPase family, with demonstrable morphological consequences for cerebral cortical astrocytes.
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    Öğe
    Texture-Based Segmentation and a New Cell Shape Index for Quantitative Analysis of Cell Spreading in AFM Images
    (Cytometry Part A, 2015-11-02) Tiryaki, Volkan; Adia-Nimuwa, Usienemnfon; Ayres, Virginia M; Ahmed, Ijaz; Shreiber, David I
    A new cell shape index is defined for use with atomic force microscopy height images of cell cultures. The new cell shape index reveals quantitative cell spreading information not included in a conventional cell shape index. A supervised learning-based cell segmentation algorithm was implemented by texture feature extraction and a multi-layer neural network classifier. The texture feature sets for four different culture surfaces were determined from the gray level co-occurrence matrix and local statistics texture models using two feature selection algorithms and by considering computational cost. The quantitative morphometry of quiescent-like and reactive-like cerebral cortical astrocytes cultured on four different culture environments was investigated using the new and conventional cell shape index. Inclusion of cell spreading with stellation information through use of the new cell shape index was shown to change biomedical conclusions derived from conventional cell shape analysis based on stellation alone. The new CSI results showed that the quantitative astrocyte spreading and stellation behavior was induced by both the underlying substrate and the immunoreactivity of the astrocytes