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Dynamic Alterations (dynamic + alteration)
Selected AbstractsMicrotubule-dependent organization of subcortical microfilaments in the early Drosophila embryoDEVELOPMENTAL DYNAMICS, Issue 3 2007Maria Giovanna Riparbelli Abstract Dynamic alterations in the spatial organization of cytoskeletal elements constitute a prominent morphological feature of the early, syncytial stages of embryogenesis in Drosophila. Here, we describe and characterize the dynamic behavior of cytoplasmic, subcortical microfilaments, which form a series of nucleus-associated structures, at different phases of the simultaneous nuclear division cycles characteristic of early Drosophila embryos. Remodeling of the cytoplasmic microfilament arrays takes place in parallel to the established cyclic reorganization of cortical microfilament structures. We provide evidence that the cortical and subcortical microfilament populations organize independently of each other, and in response to distinct instructive cues. Specifically, formation of subcortical microfilament structures appears to rely on, and spatially mirror, the organization of polarized microtubule arrays, while cortical microfilament restructuring constitutes a centrosome-dependent process. Genetic analysis identifies a requirement for SCAR, a key mediator of Arp2/3-based microfilament dynamics, in organization of subcortical microfilament structures. Developmental Dynamics 236:662,670, 2007. © 2007 Wiley-Liss, Inc. [source] Role of ,4,1 Integrins in Chemokine-Induced Monocyte Arrest under Conditions of Shear StressMICROCIRCULATION, Issue 1 2009SHARON J. HYDUK ABSTRACT Monocyte recruitment or emigration to tissues is an essential component of host defense in both acute and chronic inflammatory responses. Sequential molecular interactions mediate a cascade of tethering, rolling, arrest, stable adhesion, and intravascular crawling that culminates in monocyte diapedesis across the vascular endothelium and migration through the basement membrane of postcapillary venules. Integrins are complex adhesion and signaling molecules. Dynamic alterations in their conformation and distribution on the monocyte cell surface are required for many steps of monocyte emigration. Intracellular signaling initiated by chemokine receptors induces conformational changes in integrins that upregulate their affinity for ligands, and this is essential for monocyte arrest. This review focuses on the activation of monocyte ,4,1 integrins by endothelial chemokines, which is required for the arrest of monocytes rolling on vascular cell adhesion molecule 1 under shear flow. Using soluble ligand-binding assays and adhesion assays in parallel-plate flow chambers, critical signaling mediators in chemokine-induced ,4,1 integrin affinity upregulation and monocyte arrest have been identified, including phospholipase C, calcium, and calmodulin. [source] Dynamic alterations of the extracellular environment of ovarian surface epithelial cells in premalignant transformation, tumorigenicity, and metastasisCANCER, Issue 8 2002Callinice D. Capo-Chichi Ph.D. Abstract BACKGROUND Ovarian surface epithelial cells are positionally organized as a single cell layer by a sheet of basement membrane. It is believed that the contact of the ovarian surface epithelial cells with the basement membrane regulates cell growth and ensures the organization of the epithelium. Disabled-2 (Dab2), a signal transduction protein and a candidate tumor suppressor of ovarian carcinoma, functions in positional organization of ovarian surface epithelial cells. In ovarian carcinomas, genetic and epigenetic changes enable the tumor cells to escape positional control and proliferate in a disorganized fashion. Alterations in the extracellular environment may also be critical for tumor initiation and progression. METHODS We analyzed and compared the presence of collagen IV and laminin, the scaffold proteins of the basement membrane, and Dab2 in 50 ovarian tumors that are restricted to the ovaries and in 50 metastases of ovarian tumors by immunohistochemistry. Expression of collagen IV, laminin, and Dab2 was also analyzed by Northern blotting in a panel of human ovarian surface epithelial and cancer cell lines. RESULTS The basement membrane is often absent in morphologically benign ovarian surface and cyst epithelium and low-grade tumors and collagen IV and laminin are absent in the extracellular matrix of most of the primary tumors tested. Of the 50 ovarian tumors confined to the ovaries, 6% (3 of 50) were collagen IV positive and 24% (12 of 50) were laminin positive tumors. Of the 50 metastatic tumors, 16% (8 of 50) are collagen IV positive and 86% (43 of 50) are laminin positive. In addition, even in the metastatic ovarian tumors that are largely collagen IV negative, there are pockets of local areas in which the tumor cells are surrounded by collagen IV-positive staining. Dab2 is absent in the majority of ovarian tumors found in both ovaries and metastatic sites. In both nontumorigenic human ovarian surface epithelial and cancer cell lines, collagen IV, laminin, and Dab2 are expressed aberrantly. CONCLUSIONS Loss of the basement membrane may be an early event in the preneoplastic transformation of ovarian surface epithelium and in the early stages of tumorigenesis before tumor invasion and metastasis. The majority of primary ovarian tumors examined lack collagen IV and laminin in their extracellular matrix. However, expression of laminin is restored in the majority of metastatic tumors. Reexpression of collagen IV may also contribute to tumor metastasis. The ability of tumor cells to dynamically alter the expression of collagen IV and laminin may facilitate the shedding of cancer cells into the peritoneal spaces and subsequent attachment to the metastatic sites. We propose that loss of collagen IV and laminin may be an initial event in ovarian tumorigenicity and that restoration of collagen IV and laminin expression in the later stages of tumor development may promote metastasis of ovarian tumors. Cancer 2002;95:1802,15. © 2002 American Cancer Society. DOI 10.1002/cncr.10870 [source] Experimental hearths and the thermal alteration of Caliche on the Southern High PlainsGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 7 2005Paul N. Backhouse Throughout the Holocene, caliche has been a ubiquitous technological resource for the people of the Southern High Plains. Archaeological sites on the Southern High Plains often contain thermal features that appear to utilize caliche nodules in various cultural processes. These processes usually involve some degree of thermal dynamic alteration to the caliche, identified in the archaeological record as fire-scorched or blackened nodules. Previous studies of the pyrodynamic properties of caliche have focused on quantification of color and fracture patterns within a laboratory setting, without direct involvement of cultural processes or problems associated with thermal features. Thermal alteration variables of caliche are examined from an actualistic perspective, utilizing previously excavated basin feature geometry and local caliche outcrops. Results indicate that sustained, intense heating of caliche (above 204°C) causes significant, but variable, structural transformations at the specimen level. The experimental use of shallow basin hearths demonstrates that hearth structures were easily capable of achieving and sustaining temperatures that would result in the physical alteration of individual caliche nodules, defined here as hearthstones. The broader implications of this study suggest that the interpretation of archaeological hearthstone assemblages should reflect variability, as observed during this experiment. © 2005 Wiley Periodicals, Inc. [source] A subpopulation of mesenchymal stromal cells with high osteogenic potentialJOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 8b 2009Hua Liu Abstract Current bone disease therapy with bone marrow-derived mesenchymal stromal cells (MSC) is hampered by low efficiency. Advanced allogeneic studies on well-established mouse genetic and disease models are hindered by difficulties in isolating murine MSC (mMSC). And mMSC prepared from different laboratories exhibit significant heterogeneity. Hence, this study aimed to identify and isolate a sub-population of mMSC at an early passage number with high osteogenic potential. Enrichment of mMSC was achieved by 1-hr silica incubation and negative selection. Approximately 96% of these cells synthesized osteocalcin after 28 days of osteogenic induction in vitro, and displayed a complete dynamic alteration of alkaline phosphatase (ALP) activity with increasing osteogenic maturation and strong mineralization. Moreover, the cells displayed uniform and stable surface molecular profile, long-term survival, fast proliferation in vitro with maintenance of normal karyotype and distinct immunological properties. CD73 was found to be expressed exclusively in osteogenesis but not in adipogenesis. These cells also retained high osteogenic potential upon allogeneic transplantation in an ectopic site by the detection of bone-specific ALP, osteopontin, osteocalcin and local mineralization as early as 12 days after implantation. Hence, these cells may provide a useful source for improving current strategies in bone regenerative therapy, and for characterizing markers defining the putative MSC population. [source] | ||||||||||