733 research outputs found
The promise of the city: space, identity, and politics in contemporary social thought
No full textThe Promise of the City proposes a new theoretical framework for the study of cities and urban life. Finding the contemporary urban scene too complex to be captured by radical or conventional approaches, Kian Tajbakhsh offers a threefold, interdisciplinary approach linking agency, space, and structure. First, he says, urban identities cannot be understood through individualistic, communitarian, or class perspectives but rather through the shifting spectrum of cultural, political, and economic influences. Second, the layered, unfinished city spaces we inhabit and within which we create meaning are best represented not by the image of bounded physical spaces but rather by overlapping and shifting boundaries. And third, the macro forces shaping urban society include bureaucratic and governmental interventions not captured by a purely economic paradigm. Tajbakhsh examines these dimensions in the work of three major critical urban theorists of recent decades: Manuel Castells, David Harvey, and Ira Katznelson. He shows why the answers offered by Marxian urban theory to the questions of identity, space, and structure are unsatisfactory and why the perspectives of other intellectual traditions such as poststructuralism, feminism, Habermasian Critical Theory, and pragmatism can help us better understand the challenges facing contemporary cities
Pathological features of tissues and cell populations during cancer cachexia
No full textCancers remain among the most devastating diseases in the human population in spite of considerable advances in limiting their impact on lifespan and healthspan. The multifactorial nature of cancers, as well as the number of tissues and organs that are affected, have exposed a considerable diversity in mechanistic features that are reflected in the wide array of therapeutic strategies that have been adopted. Cachexia is manifested in a number of diseases ranging from cancers to diabetes and ageing. In the context of cancers, a majority of patients experience cachexia and succumb to death due to the indirect effects of tumorigenesis that drain the energy reserves of different organs. Considerable information is available on the pathophysiological features of cancer cachexia, however limited knowledge has been acquired on the resident stem cell populations, and their function in the context of these diseases. Here we review current knowledge on cancer cachexia and focus on how tissues and their resident stem and progenitor cell populations are individually affected
Efferocytosis and Atherosclerosis: Regulation of Phagocyte Function by MicroRNAs
No full textThere is evidence of the critical role of efferocytosis, the clearance of apoptotic cells (ACs) by phagocytes, in vascular cell homeostasis and protection against atherosclerosis. Specific microRNAs (miRs) can regulate atherogenesis by controlling the accumulation of professional phagocytes (e.g., macrophages) and nonprofessional phagocytes (i.e., neighboring tissue cells with the ability to acquire a macrophage-like phenotype) within the arterial wall, the differentiation of phagocytes into foam cells, the efferocytosis of apoptotic foam cells by phagocytes, and the phagocyte-mediated inflammatory response. A better understanding of the mechanisms involved in miR-regulated phagocyte function might lead to novel therapeutic antiatherosclerotic strategies. In this review, we try to shed light on the relationship between miRs and cellular players in the process of efferocytosis in the context of atherosclerotic plaque and their potential as molecular targets for novel antiatherosclerotic therapies
Geodesic gaussian processes for the parametric reconstruction of a free-form surface
No full textReconstructing a free-form surface from 3-dimensional (3D) noisy measurements is a central problem in inspection, statistical quality control, and reverse engineering. We present a new method for the statistical reconstruction of a free-form surface patch based on 3D point cloud data. The surface is represented parametrically, with each of the three Cartesian coordinates (x, y, z) a function of surface coordinates (u, v), a model form compatible with computer-aided-design (CAD) models. This model form also avoids having to choose one Euclidean coordinate (say, z) as a “response” function of the other two coordinate “locations” (say, x and y), as commonly used in previous Euclidean kriging models of manufacturing data. The (u, v) surface coordinates are computed using parameterization algorithms from the manifold learning and computer graphics literature. These are then used as locations in a spatial Gaussian process model that considers correlations between two points on the surface a function of their geodesic distance on the surface, rather than a function of their Euclidean distances over the xy plane. We show how the proposed geodesic Gaussian process (GGP) approach better reconstructs the true surface, filtering the measurement noise, than when using a standard Euclidean kriging model of the “heights”, that is, z(x, y). The methodology is applied to simulated surface data and to a real dataset obtained with a noncontact laser scanner. Supplementary materials are available online
A Critical Requirement for Notch Signaling in Maintenance of the Quiescent Skeletal Muscle Stem Cell State
No full textAbstract
Notch signaling plays a key role in virtually all tissues and organs in metazoans; however, limited examples are available for the regulatory role of this pathway in adult quiescent stem cells. We performed a temporal and ontological assessment of effectors of the Notch pathway that indicated highest activity in freshly isolated satellite cells and, unexpectedly, a sharp decline before the first mitosis, and subsequently in proliferating, satellite cell-derived myoblasts. Using genetic tools to conditionally abrogate canonical Notch signaling during homeostasis, we demonstrate that satellite cells differentiate spontaneously and contribute to myofibers, thereby resulting in a severe depletion of the stem cell pool. Furthermore, whereas loss of Rbpj function provokes some satellite cells to proliferate before fusing, strikingly, the majority of mutant cells terminally differentiate unusually from the quiescent state, without passing through S-phase. This study establishes Notch signaling pathway as the first regulator of cellular quiescence in adult muscle stem cells.
Disclosure of potential conflicts of interest is found at the end of this article.</jats:p
The homeobox gene Arx is a novel positive regulator of embryonic myogenesis.
No full textSkeletal muscle fibers form in overlapping, but distinct phases that depend on the generation of temporally different lineages of myogenic cells. During primary myogenesis (E10.5–E12.5 in the mouse), embryonic myoblasts fuse homotypically to generate primary fibers, whereas during later development (E14.5–E17.5), fetal myoblasts differentiate into secondary fibers. How these myogenic waves are regulated remains largely unknown. Studies have been hampered by the lack of markers which would distinguish embryonic from fetal myoblast populations. We show here that the homeobox gene Arx is strongly expressed in differentiating embryonic muscle, downstream of myogenic basic helix–loop–helix (bHLH) genes. Its expression progressively decreases during development. When overexpressed in the C2C12 myogenic cell line, Arx enhances differentiation. Accordingly, it stimulates the transcriptional activity from the Myogenin promoter and from multimerized E-boxes when co-expressed with MyoD and Mef2C in CH310T1/2. Furthermore, Arx co-immunoprecipitates with Mef2C, suggesting that it participates in the transcriptional regulatory network acting in embryonic muscle. Finally, embryonic myoblasts isolated from Arx-deficient embryos show a delayed differentiation in vivo together with an enhanced clonogenic capacity in vitro. We propose here that Arx acts as a novel positive regulator of embryonic myogenesis by synergizing with Mef2C and MyoD and by establishing an activating loop with Myogenin
Differential activation of Myf5 and MyoD by different Wnts in explants of mouse paraxial mesoderm and the later activation of myogenesis in the absence of Myf5
No full textActivation of myogenesis in newly formed somites is dependent upon signals derived from neighboring tissues, namely axial structures (neural tube and notochord) and dorsal ectoderm, In explants of paraxial mesoderm from mouse embryos, axial structures preferentially activate myogenesis through a Myf5-dependent pathway and dorsal ectoderm preferentially through a MyoD-dependent pathway. Here we report that cells expressing Wnt1 will preferentially activate Myf5 while cells expressing Wnt7a will preferentially activate MyoD. Wnt1 is expressed in the dorsal neural tube and Wnt7a in dorsal ectoderm in the early embryo, therefore both can potentially act in vivo to activate Myf5 and MyoD, respectively, Wnt4, Wnt5a and Wnt6 exert an intermediate effect activating both Myf5 and MyoD equivalently in paraxial mesoderm, Sonic Hedgehog synergises with both Wnt1 and Wnt7a in explants from E8.5 paraxial mesoderm but not in explants from E9.5 embryos. Signaling through different myogenic pathways may explain the rescue of muscle formation in Myf5 null embryos, which do not form an early myotome but later develop both epaxial and hypaxial musculature, Explants of unsegmented paraxial mesoderm contain myogenic precursors capable of expressing MyoD in response to signaling from a neural tube isolated from E10.5 embryos, the developmental stage when MyoD is present throughout the embryo. Myogenic cells cannot activate MyoD in response to signaling from a less mature neural tube. Together these data suggest that different Wnt molecules can activate myogenesis through different pathways such that commitment of myogenic precursors is precisely regulated in space and time to achieve the correct pattern of skeletal muscle development
A Study of Mohsen Tajbakhsh's Illustrations in Qajar and Pahlavi Lithographic Books
No full textIntroduction: The illustrators of lithographic books are important research components that remain unknown to the audience interested in this field except for limited cases. According to the studies of «Ulrich Marzolph», 46 book illustrators have been identified in the field of the lithographic printing industry of Iran in the Qajar era, 19 of whom are on the list of the most famous ones. Mohsen Tajbakhsh, as one of these distinguished but little-known artists, has made a significant contribution to the expression of the public culture of the Iranian people, and his works have represented the technical and visual qualities of reproduction of pictures through lithography in his time. This study seeks to introduce Mohsen Tajbakhsh as a hard-working and active artist in the late Qajar and early Pahlavi periods. Also, identifying, categorizing and visual analysis of his works is one of the main goals of this research.Research Method: The present research is descriptive-analytical, and data collection was conducted through direct access and study of manuscripts using library sources and written documents.Findings: Even though Mohsen Tajbakhsh followed the artists before him in illustrating books, features such as short and large human bodies, round faces with almond-shaped eyes, smiling lips, tall horses with long legs, etc., are the distinctive features of his illustrations which makes it possible to distinguish Tajbakhsh's works from others. Also, comparing his miniature paintings with others makes it possible to realize more simplicity and fewer details in his illustration technique.Conclusion: Mohsen Tajbakhsh was a hard-working illustrator who lived in Tehran during the era of Ahmad Shah Qajar and Reza Shah Pahlavi and illustrated many books with religious, folk-romantic, and school (Maktabkhaneh) themes. In the illustration, he has adopted the style of artists before him, and despite the trend towards realistic illustration in the mentioned period and access to such miniature paintings, he has chosen traditional Iranian illustration, simplicity in expression, creating flat images without volume and perspective, etc
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