Detection and gradation of oriented texture

Chaudhuri, B. B.; Kundu, Pulak; Sarkar, N.

doi:10.1016/0167-8655(93)90088-u

Cited by 45 publications

(38 citation statements)

References 7 publications

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“…The superimposed image stack was first separated into the collagen and elastin contents based on color channels. An algorithm developed by Chaudhuri et al (33), Karlon et al (34), and Courtney et al (35) was used to obtain the pixel intensity gradient for determination of the preferred fiber direction for each subregion (Fig. 2 C).…”

Section: Optical and Histological Measurementsmentioning

confidence: 99%

On the Presence of Affine Fibril and Fiber Kinematics in the Mitral Valve Anterior Leaflet

Lee

Zhang

Liao

et al. 2015

Biophysical Journal

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In this study, we evaluated the hypothesis that the constituent fibers follow an affine deformation kinematic model for planar collagenous tissues. Results from two experimental datasets were utilized, taken at two scales (nanometer and micrometer), using mitral valve anterior leaflet (MVAL) tissues as the representative tissue. We simulated MVAL collagen fiber network as an ensemble of undulated fibers under a generalized two-dimensional deformation state, by representing the collagen fibrils based on a planar sinusoidally shaped geometric model. The proposed approach accounted for collagen fibril amplitude, crimp period, and rotation with applied macroscopic tissue-level deformation. When compared to the small angle x-ray scattering measurements, the model fit the data well, with an r 2 ¼ 0.976. This important finding suggests that, at the homogenized tissue-level scale of~1 mm, the collagen fiber network in the MVAL deforms according to an affine kinematics model. Moreover, with respect to understanding its function, affine kinematics suggests that the constituent fibers are largely noninteracting and deform in accordance with the bulk tissue. It also suggests that the collagen fibrils are tightly bounded and deform as a single fiber-level unit. This greatly simplifies the modeling efforts at the tissue and organ levels, because affine kinematics allows a straightforward connection between the macroscopic and local fiber strains. It also suggests that the collagen and elastin fiber networks act independently of each other, with the collagen and elastin forming long fiber networks that allow for free rotations. Such freedom of rotation can greatly facilitate the observed high degree of mechanical anisotropy in the MVAL and other heart valves, which is essential to heart valve function. These apparently novel findings support modeling efforts directed toward improving our fundamental understanding of tissue biomechanics in healthy and diseased conditions.

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Section: Optical and Histological Measurementsmentioning

confidence: 99%

On the Presence of Affine Fibril and Fiber Kinematics in the Mitral Valve Anterior Leaflet

Lee

Zhang

Liao

et al. 2015

Biophysical Journal

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“…For microtubule organization, each pixel was assigned an orientation and a value based on its intensity relative to its immediate surroundings (Chaudhuri et al, 1993) (R. Fernandez-Gonzalez and J.A.Z., unpublished). Pixel orientation was perpendicular to the gradient at that pixel; the gradient is a vector that points in the direction of the maximum local intensity change.…”

Section: Measurements and Statisticsmentioning

confidence: 99%

“…A single ratio between the mean background-subtracted intensity for DV edges (0-45° relative to the AP axis) and AP edges (75-90° relative to the AP axis) was calculated for each embryo. An equal mix of Oregon R, y w and da-Gal4 embryos was the wild-type control.For microtubule organization, each pixel was assigned an orientation and a value based on its intensity relative to its immediate surroundings (Chaudhuri et al, 1993) (R. Fernandez-Gonzalez and J.A.Z., unpublished). Pixel orientation was perpendicular to the gradient at that pixel; the gradient is a vector that points in the direction of the maximum local intensity change.…”

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confidence: 99%

Regulation of cytoskeletal organization and junctional remodeling by the atypical cadherin Fat

Marcinkevicius

Zallen

2013

Development

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SUMMARYThe atypical cadherin Fat is a conserved regulator of planar cell polarity, but the mechanisms by which Fat controls cell shape and tissue structure are not well understood. Here, we show that Fat is required for the planar polarized organization of actin denticle precursors, adherens junction proteins and microtubules in the epidermis of the late Drosophila embryo. In wild-type embryos, spatially regulated cell-shape changes and rearrangements organize cells into highly aligned columns. Junctional remodeling is suppressed at dorsal and ventral cell boundaries, where adherens junction proteins accumulate. By contrast, adherens junction proteins fail to accumulate to the wild-type extent and all cell boundaries are equally engaged in junctional remodeling in fat mutants. The effects of loss of Fat on cell shape and junctional localization, but not its role in denticle organization, are recapitulated by mutations in Expanded, an upstream regulator of the conserved Hippo pathway, and mutations in Hippo and Warts, two kinases in the Hippo kinase cascade. However, the cell shape and planar polarity defects in fat mutants are not suppressed by removing the transcriptional co-activator Yorkie, suggesting that these roles of Fat are independent of Yorkie-mediated transcription. The effects of Fat on cell shape, junctional remodeling and microtubule localization are recapitulated by expression of activated Notch. These results demonstrate that cell shape, junctional localization and cytoskeletal planar polarity in the Drosophila embryo are regulated by a common signal provided by the atypical cadherin Fat and suggest that Fat influences tissue organization through its role in polarized junctional remodeling. DEVELOPMENT 434 Donoughe and DiNardo, 2011). Despite substantial progress in understanding the upstream signals that regulate Fat activity, the cellular and molecular mechanisms by which Fat controls planar tissue organization are not well understood. Fat and Ds are asymmetrically localized within cells (Ambegaonkar et al., 2012;Bosveld et al., 2012;Brittle et al., 2012) and could influence cell polarity directly or through the regulation of downstream effectors. However, the relationship between these molecular asymmetries and the asymmetric shapes and behaviors of cells is not clear. Fat and Ds regulate the localization and activity of Frizzled pathway proteins (Adler et al., 1998;Strutt and Strutt, 2002;Yang et al., 2002;Ma et al., 2003), but some effects of Fat and Ds are independent of Frizzled (Casal et al., 2006;Donoughe and DiNardo, 2011). Fat/Ds signaling produces an asymmetric localization of the unconventional myosin Dachs, which is required for cell and tissue shape (Mao et al., 2006;Rogulja et al., 2008;Mao et al., 2011b;Bosveld et al., 2012). Fat binds to Atrophin (Grunge -FlyBase), a transcriptional regulator that is required for planar polarity in the eye (Zhang et al., 2002;Fanto et al., 2003;Saburi et al., 2012). Ds regulates microtubule organization in the wing and has been proposed to influ...

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“…these features on stem cell phenotype commitment. It should be noted that the current method is applicable to fibrous network topology, and would not be amenable to more amorphous substrates, although other characterization approaches [50,51] might be useful when identifying fibre orientation and angle distribution in amorphous materials. Screening for significant correlations between microstructural features and gene expression was performed via a second-order polynomial regression.…”

Section: Discussionmentioning

confidence: 99%

Systems level approach reveals the correlation of endoderm differentiation of mouse embryonic stem cells with specific microstructural cues of fibrin gels

Task

D’Amore

Singh

et al. 2014

J. R. Soc. Interface.

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ResearchCite this article: Task K, D'Amore A, Singh S, Candiello J, Jaramillo M, Wagner WR, Kumta P, Banerjee I. 2014 Systems level approach reveals the correlation of endoderm differentiation of mouse embryonic stem cells with specific microstructural cues of fibrin gels. J. R. Soc. Stem cells receive numerous cues from their associated substrate that help to govern their behaviour. However, identification of influential substrate characteristics poses difficulties because of their complex nature. In this study, we developed an integrated experimental and systems level modelling approach to investigate and identify specific substrate features influencing differentiation of mouse embryonic stem cells (mESCs) on a model fibrous substrate, fibrin. We synthesized a range of fibrin gels by varying fibrinogen and thrombin concentrations, which led to a range of substrate stiffness and microstructure. mESCs were cultured on each of these gels, and characterization of the differentiated cells revealed a strong influence of substrate modulation on gene expression patterning. To identify specific substrate features influencing differentiation, the substrate microstructure was quantified by image analysis and correlated with stem cell gene expression patterns using a statistical model. Significant correlations were observed between differentiation and microstructure features, specifically fibre alignment. Furthermore, this relationship occurred in a lineage-specific manner towards endoderm. This systems level approach allows for identification of specific substrate features from a complex material which are influential to cellular behaviour. Such analysis may be effective in guiding the design of scaffolds with specific properties for tissue engineering applications.

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Detection and gradation of oriented texture

Cited by 45 publications

References 7 publications

On the Presence of Affine Fibril and Fiber Kinematics in the Mitral Valve Anterior Leaflet

On the Presence of Affine Fibril and Fiber Kinematics in the Mitral Valve Anterior Leaflet

Regulation of cytoskeletal organization and junctional remodeling by the atypical cadherin Fat

Systems level approach reveals the correlation of endoderm differentiation of mouse embryonic stem cells with specific microstructural cues of fibrin gels

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