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Epithelial Sheets (epithelial + sheet)
Selected AbstractsGenerality of vertebrate developmental patterns: evidence for a dermomyotome in fishEVOLUTION AND DEVELOPMENT, Issue 1 2006S. H. Devoto SUMMARY The somitic compartment that gives rise to trunk muscle and dermis in amniotes is an epithelial sheet on the external surface of the somite, and is known as the dermomyotome. However, despite its central role in the development of the trunk and limbs, the evolutionary history of the dermomyotome and its role in nonamniotes is poorly understood. We have tested whether a tissue with the morphological and molecular characteristics of a dermomyotome exists in nonamniotes. We show that representatives of the agnathans and of all major clades of gnathostomes each have a layer of cells on the surface of the somite, external to the embryonic myotome. These external cells do not show any signs of terminal myogenic or dermogenic differentiation. Moreover, in the embryos of bony fishes as diverse as sturgeons (Chondrostei) and zebrafish (Teleostei) this layer of cells expresses the pax3 and pax7 genes that mark myogenic precursors. Some of the pax7- expressing cells also express the differentiation-promoting myogenic regulatory factor Myogenin and appear to enter into the myotome. We therefore suggest that the dermomyotome is an ancient and conserved structure that evolved prior to the last common ancestor of all vertebrates. The identification of a dermomyotome in fish makes it possible to apply the powerful cellular and genetic approaches available in zebrafish to the understanding of this key developmental structure. [source] Upregulation of gamma-2 laminin-332 in the mouse ear vesicant wound model,JOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY, Issue 3 2009Yoke-Chen Chang Abstract Epithelial cell migration during wound healing is regulated in part by enzymatic processing of laminin-332 (formerly LN-5), a heterodimer formed from ,, ,, and , polypeptide chains. Under static conditions, laminin-332 is secreted into the extracellular matrix as a proform and has two chains processed to smaller forms, allowing it to anchor epithelial cells to the basement membrane of the dermis. During incisional wounding, laminin ,2 chains in particular are processed to smaller sizes and function to promote epithelial sheet migration over the wound bed. The present study examines whether this same function occurs following chemical injury. The mouse ear vesicant model (MEVM) was used to follow the pathology in the ear and test whether processed laminin-332 enhances epithelial cell migration. Skin biopsies of sulfur mustard (SM) exposed ears for several time points were analyzed by histology, immunohistochemistry, real-time PCR, and Western blot analysis. SM exposure greatly increased mRNA levels for laminin-,2 in comparison to the other two chains. Protein production of laminin-,2 was upregulated, and there was an increase in the processed forms. Protein production was in excess of the amount required to form heterotrimeric laminin-332 and was associated with the migrating epithelial sheet, suggesting a potential role in wound healing for monomeric laminin-,2. © 2009 Wiley Periodicals, Inc. J Biochem Mol Toxicol 23:172,184, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.20275 [source] Analysis of Meox - 2 mutant mice reveals a novel postfusion-based cleft palateDEVELOPMENTAL DYNAMICS, Issue 2 2006Jiu-Zhen Jin Abstract Cleft palate represents a common human congential disease involving defects in the development of the secondary palate. Major steps in mammalian palatogenesis include vertical growth, elevation, and fusion of the palate shelves. Our current study with the homeobox gene Meox - 2 during mouse secondary palate development reveals a novel postfusion-based mechanism for cleft palate. Meox - 1 and Meox - 2 are two functionally related homeobox genes playing important roles in somitogenesis and limb muscle differentiation. We found that the expression of Meox - 2, not Meox - 1, marks the specification of early mouse palatal mesenchymal cells in the maxillary processes at embryonic day 11.5 (E11.5). From E12.5 to E15.5, the expression of Meox - 2 occupies only the posterior part of the palate, providing an early molecular marker for the anterior,posterior polarity in mouse secondary palate formation. A total of 35.3% of Meox - 2,/, (n = 17) and 25.5% of Meox - 2+/, (n = 55) mouse embryos display a cleft palate phenotype at E15.5, indicating that the reduction of Meox - 2 function is associated with susceptibility to cleft palate. Unlike previously reported clefts, none of the clefts found in Meox - 2 mutants contain any epithelial sheets in the medial edge areas, and detailed examination revealed that the clefts resulted from the breakdown of newly fused palates. This article is the first report of a gene required to maintain adherence of the palatal shelves after fusion. Developmental Dynamics 235:539,546, 2006. © 2005 Wiley-Liss, Inc. [source] Novel metalloprotease,disintegrin, meltrin , (ADAM35), expressed in epithelial tissues during chick embryogenesisDEVELOPMENTAL DYNAMICS, Issue 3 2004Mitsuko Watabe-Uchida Abstract Members of the ADAM (adisintegrin and metalloprotease) family are involved in fertilization, morphogenesis, and pathogenesis. Their metalloprotease domains mediate limited proteolysis, including ectodomain shedding of membrane-anchored growth factors and intercellular-signaling proteins, and their disintegrin domains play regulatory roles in cell adhesion and migration. In screening for cDNAs encoding chicken ADAM proteins expressed during muscle development, we identified Meltrin , as a novel member of this family. To elucidate its functions, we investigated its expression during development by using antibodies raised against its protease domain. In the somites, Meltrin , protein was specifically expressed in the myotomal cells, which delaminate from the dermomyotome to form epithelial sheets. It was also found in the surface ectoderm, lens placodes, otic vesicles, and the gut epithelia. Basolateral localization of Meltrin , in these epithelial cells suggests its unique roles in the organization of the epithelial tissues and development of the sensory organs and the gut. Developmental Dynamics 230:557,568, 2004. © 2004 Wiley-Liss, Inc. [source] Cytology of the central zone of the prostateDIAGNOSTIC CYTOPATHOLOGY, Issue 5 2003Lars Egevad M.D., Ph.D. Abstract The prostate has three anatomical regions: the peripheral, transition, and central zones (CZ). The CZ has distinct histological features, but its cytological morphology has not been described. This study was done on surgical specimens to ensure that samples were representative of the CZ, and that no prostatic intraepithelial neoplasia (PIN) or cancer contaminated the smears. An incision was made in the CZ of 51 prostatectomy specimens, and cells were scraped from cut surfaces. After exclusion of samples contaminated by PIN or cancer or with poor cell yield, 39 Giemsa-stained smears remained for analysis. Large branching epithelial sheets with geographic architecture and crowded nuclei were seen in 97% of smears. Epithelial clusters with elongated palisaded nuclei were identified in 80% of cases, but were always a minor component. Visible nucleoli (97%), cytoplasmic vacuoles (97%), and smooth muscle cells in the background (95%) were common. Blue-green cytoplasmic granules resembling seminal vesicle pigment were seen in 97%. Magenta-colored cytoplasmic pigment, similar to granules seen in other regions of the prostate, was found in 74%. Recognition of CZ epithelium as a benign constituent of prostate cytology is important because elongated cells, crowded nuclei, and visible nucleoli may otherwise be misinterpreted as PIN or cancer. Diagn. Cytopathol. 2003;28:239,244. © 2003 Wiley-Liss, Inc. [source] | ||||||||||