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  • 1
    Electronic Resource
    Electronic Resource
    Cell migration into neural tube lumen provides evidence for the “fixed cortex” theory of cell motility (1989)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 14 (1989), S. 469-484 
    Details
    ISSN: 0886-1544
    Keywords: “fixed cortex” model ; neural crest ; mesenchyme ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We present a model of cell motility based on emigration of neural crest cells into the neural tube lumen under in vitro conditions (10% fetal calf serum or YIGSR) that inhibit their normal emigration from the base of the neuroepithelium into surrounding extracellular matrix (ECM). Ultrastructural observations reveal that cells lining the lumen are joined by zonulae adherentes (ZA), which are points of strong intercellular attachment, and thereby serve as markers for fixed regions of plasmalemma and cortical actin. Three major observations of the relationship of cells to the ZA support the “fixed cortex” model of mesenchymal cell migration. First, cells extend apical cel processes past the ZA into the lumen. To do this, they must make new apical plasmalemma and actin corrtex that the endoplasm slides into. Second, elongated cells are observed in the lumen that are still attached via ZA to the neuroepithelium. This indicates that all of the endoplasm finally slides past the ZA. Third, numerous cytoplasmic pieces, often attached to each other and to the neuroepithelium via ZA, are found at the site where cells appear to have detached from the epithelium after entering the lumen. Since the ZA is fixed in location, the endoplasm must have slid past it into newly manufactured anterior cortex and plasmalemma, with the trailing end of the cell finally snapping off. The “fixed cortex” theory of cell migration agrees with existing data in that it predicts the polarized insertion of new plasmalemma and actin at the leading end of the cell, but it differs significantly from existing theories of mesenchymal cell migration in that it states that the cell surface remains firmly attached to the substratum while the myosin-rich endoplasm slides past it.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970140405
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  • 2
    Electronic Resource
    Electronic Resource
    Theory for epithelial-mesenchymal transformation based on the “fixed cortex” cell motility model (1989)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 14 (1989), S. 455-457 
    Details
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970140403
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  • 3
    Electronic Resource
    Electronic Resource
    The fine structure of differentiating muscle in the salamander tail (1963)
    Springer
    Cell & tissue research 59 (1963), S. 6-34 
    Details
    ISSN: 1432-0878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Thin methacrylate sections of developing tails of Amblystoma opacum larvae were examined in the electron microscope and a series of stages in the differentiation of the myotome musculature was reconstructed from electron micrographs and earlier light microscopic studies of living muscle. The earliest muscle cell precursor that can be clearly identified is a round or oval cell with abundant cytoplasm containing scattered myofilaments and free ribonucleoprotein granules, but little endoplasmic reticulum. These cells sometimes form a syncytium and they may also be fused with adjacent formed muscle fibers by lateral processes. Nuclei are large and nucleoli are prominent. This cell, called a “myoblast” here, is distinctly different in its appearance from the adjacent mesenchymal cells which have abundant granular endoplasmic reticulum. The earliest myofilaments are of both the thick and thin varieties and are distributed in a disorganized fashion in the cytoplasm. These filaments are similar to the actin and myosin filaments described by Huxley and they are present in the cytoplasm at an earlier stage of differentiation than heretofore suspected from light microscopy studies. The first myofibrils are a heterogeneous combination of thick and thin filaments and dense Z bands and are not homogeneous as so many light microscopists have contended. As development progresses, cross striations become more orderly and definitive sarcomeres are formed. Thereafter, new myofilaments and Z bands seem to be added to the lateral surfaces and distal ends of existing myofibrils. Free ribonucleoprotein granules are a prominent part of the myoblast cytoplasm and are found in close association with the differentiating myofilaments in all stages of development. In early muscle fibers and some of the formed fibers, similar granules are often concentrated in the I bands. A theory of myofilament differentiation based on current concepts of the role of ribonucleoprotein in protein synthesis is presented in the discussion. Stages in myofibril formation and possible relationships of the filaments in developing muscle cells to other types of cytoplasmic filaments are also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00321005
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  • 4
    Electronic Resource
    Electronic Resource
    An autoradiographic and electron microscopic study of collagen synthesis in differentiating cartilage (1963)
    Springer
    Cell & tissue research 61 (1963), S. 110-144 
    Details
    ISSN: 1432-0878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The synthesis of the proline-rich collagen component of cartilage matrix has been studied by autoradiography using both the light and electron microscope. Amblystoma maculatum larvae had their forelimbs amputated, were allowed to regenerate for 12–15 days, and then injected intraperitoneally with tritiated proline. The animals were fixed at various times (1 min. to 28 days) after the injection and sections of the developing limbs were coated for autoradiography by dipping in Ilford L 4 or Gevaert 3.07 emulsion. The sequential labeling of the organelles of the cartilage cell which occurred is illustrated in light and electron micrographs. Radioactive products first appeared in the ergastoplasm and were associated with the cisternae of the endoplasmic reticulum. Twenty to thirty minutes after the injection, labeled material began to appear in the Golgi zone. There, the newly synthesized protein accumulated within large vacuoles. The fibrillar material within the vacuoles may represent collagen and the more amorphous material, mucoprotein. The vacuoles subsequently (∼2 hrs. later) discharge their labeled contents into the extracellular space. The secreted protein is probably soluble collagen (tropocollagen) for it diffuses readily through the matrix to polymerize into striated collagen fibrils some distance from the cell. These findings contradict some widely held opinions that the fibrillar component of the matrix arises by excortication and appositional growth of fibrils originating from the ectoplasm of chondrocytes. It seems reasonable to conclude that the secretory pathway by which extracellular proteins are produced in cartilage is analogous to that suggested for epithelial gland cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00341524
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  • 5
    Electronic Resource
    Electronic Resource
    Expression of β1 integrins changes during transformation of avian lens epithelium to mesenchyme in collagen gels (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Developmental Dynamics 201 (1994), S. 378-393 
    Details
    ISSN: 1058-8388
    Keywords: Integrins ; Epithelial-mesenchymal transformation ; Lens epithelium ; Type I collagen gels ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Remarkably, a number of definitive epithelia, such as that of the anterior lens, give rise when suspended within 3D gels of type I collagen, to elongate, bipolar shaped cells that exhibit the ultrastructure, polarity, and migratory ability of mesenchymal cells. They begin producing type I collagen and stop producing crystallins, type IV collagen, and laminin. Here, we investigated changes in β1 integrins and their extracellular matrix (ECM) ligands during this transdifferentiation. The former free surface of the lens epithelium that is now in contact with collagen begins within a day to stain intensely for β1 and it is this surface rather than the surface facing the basement membrane that gives rise to mesenchymal cells. Immunoprecipitation experiments reveal a large increase in the β1 integrin subunit on mesenchymal cells as compared to the epithelium of origin. The α5 integrin subunit, which is barely detectable in the lens, increases in the mesenchymal cells and α3 continues to be expressed at about the same level as in the epithelium. α6, the epithelial integrin subunit, and laminin, its ECM ligand, are not detected immunohistochemically or biochemically in the mesenchyme. Rather, the mesenchymal cells secrete abundant fibronectin, the major ECM ligand for α5β1. RGD peptides do not inhibit the transformation but antibodies to β1 do perturb the emigration of mesenchymal cells from the lens apical surface. We conclude that the β1 integrins newly expressed on the apical epithelial surface interact with the surrounding 3D collagen gel to help bring about this unusual epithelial-mesenchymal transition. © 1994 Wiley-Liss, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aja.1002010409
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  • 6
    Electronic Resource
    Electronic Resource
    Tissue-specific expression of type XII collagen during mouse embryonic development (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Developmental Dynamics 196 (1993), S. 37-46 
    Details
    ISSN: 1058-8388
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Polyclonal antibodies were raised in rabbits against a fusion peptide representing a portion of the amino-terminal non-triplehelical domain of mouse type XII collagen. The antibodies reacted with bands of 220 and 350 kDa on Western blots of mouse tissue extracts. Immunohistochemical analyses of mouse embryos demonstrated that type XII collagen is expressed mainly in dense connective tissues of tendons, ligaments, dermis, cornea, blood vessel walls, meninges, and developing membranous bones. Comparison of skin extracts and medium of cultured mouse skin fibroblasts by Western blotting showed that while tissues contain short 220 kDa type XII collagen polypeptides as well as the long form, cultured cells produce mainly the long form with 350 kDa polypeptides. © 1993 wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aja.1001960105
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  • 7
    Electronic Resource
    Electronic Resource
    Matrix-cytoskeletal interactions in the developing eye (1985)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 27 (1985), S. 143-156 
    Details
    ISSN: 0730-2312
    Keywords: cell-matrix interaction ; cytoskeleton ; Extracellular matrix ; mesenchyme ; epithelial-mesenchymal transformation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The embryonic avian corneal epithelium in vitro responds to extracellular matrix (ECM) molecules in either soluble or polymerized form by flattening its basal surface, organizing the basal cortical actin cytoskeleton, and stepping up its production of corneal stroma twofold. Embryonic corncal epithelia, like hepatocytes and mammary gland cells, seem to contain heparan sulfate proieoglycan (HSPG) in their plasmalemma, which may interact with actin on the one hand or underlying collagen on the other. Work on the corneal epithelium suggests that, in addition to HSPG, specific glycoprotein receptors for laminin and collagen exist in the basal plasmalemma and play, the critical role in actually organizing the basal epithelial cytoskeleton. As yet. uncharacterized proteins may link such receptors to actin. We suggest that ECM-dependent organization of the cytoskeleton is responsible for ECM enhancement of corneal epithelial differentiation. Cell shape and exogenous ECM also affect mesenchymal cell differentiation. In the case of the conical fibroblast migrating in collagen gels, an actin cortex present around the elongate cell seems to interact with myosin in the cytosol to bring about pseudopodial extension. Both microtubules and actin microfilaments are involved in fibroblast elongation in collagen gels. It follows from the rules presented in this review that the mesenchymal cell surface is quite different from the epithelial cell surface in its organization. Nevertheless, epithelial cell surface-ECM interaction can be modified in the embryo at particular times to permit predesignated epithelial-mesenchymal transformations, as for example at the primitive streak. Though basal surfaces of definitive, nonmalignanl epithelia adhere rather strictly to the rules of epithelium-ECM interaction and do not invade underlying ECM, the environment can be manipulated in vitro to cause these epithelia to send out pseudopodia and give rise aberrantly to mesenchymal cells in collagen gels. Further study of this phenomenon should cast light on the manner in which epithelial and mesenchymal cells organize receptors for matrix molecules on their cell surfaces and develop appropriate cytoskeletal responses to the extracellular matrix.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240270208
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  • 8
    Electronic Resource
    Electronic Resource
    Fine structure and origin of the tunic of Perophora viridisSupported by grants HD-00143, 2TI-GM406, and HD-30097 from the United States Public Health Service. (1966)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 120 (1966), S. 267-280 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The fine structure of the tunic of a typical ascidian was investigated because of the cellulose-like polysaccharide known to occur in its substance. The glycoprotein mantle does contain filaments very much like plant cellulose in morphology. Tunicin filaments are 35-50 Å in diameter, often beaded, and of indeterminate length. Histochemical evidence that they are composed of cellulose is given here and past chemical and physical studies on the unusual ascidian polysaccharide are reviewed. Moreover, we present here for the first time direct autoradiographic evidence that epidermal cells are involved in the synthesis and secretion of tunicin. Tritiated glucose is immediately incorporated into the Golgi zone of epidermal cells and labeled product appears in the tunic at later intervals. The fine structure of the epidermal cell is described in detail. Unlike the rather moribund appearing vanadocyte that wanders through the tunic, the epidermal cell has well-developed cytoplasmic organelles and a large vesicular nucleus. The granular endoplasmic reticulum is abundant and the Golgi complex is highly developed. It seems likely that the lamellae and vesicles of the Golgi complex are involved in the production of the tunic sugar and that tunic proteins of as yet unknown nature are produced by the ergastoplasm. Further investigation of the ascidian mantle should be of interest because of the possibility that cellulose is a more general component of glycoprotein surface coats in animals than has heretofore been recognized.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051200304
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  • 9
    Electronic Resource
    Electronic Resource
    Origin of osteoclasts from mononuclear leucocytes in regenerating newt limbsSupported by grant C-5196 (formerly C-3708) from the United States Public Health Service. (1962)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 143 (1962), S. 329-337 
    Details
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1091430402
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  • 10
    Electronic Resource
    Electronic Resource
    Interaction of embryonic cell surface and cytoskeleton with extracellular matrix (1982)
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 165 (1982), S. 1-12 
    Details
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Evidence for cell-matrix in vitro and in the embryo is briefly reviewed, and more detailed observations are presented on the reactions of corneal epithelium and mesenchyme to extracellular matrix (ECM) The basal surface of embryonic corneal epithelium blebs when the underlying ECM is removed If the epithelium is cultured on top of the lens capsule or collagen gel, the basal surface flattens and the cortical cytoskeleton reorganizes to resemble that present in vivo The basal surface also responds to soluble matrix molecules (types I-IV collagens, laminin, fibronectin), and the cells step up synthesis of corneal stroma as measured by incorporation of proline into collagen When embryonic corneal fibroblasts are placed on top of hydrated gels they tend to burrow into the gel rather than sitting on top as does epithelium When grown inside collagen gels, these mesenchymal cells elongate and the entire cell surface and cytoskeleton organize in response to matrix Stress fibers and ruffling membranes characterize the cells grown on glass When embryonic lens or corneal epithelia are placed within, instead of on top of, collagen gels, they give rise to mesenchyme-like cells from their apical surfaces In vivo, these epithelia do not give rise to mesenchyme The rules for epithelial-mesenchymal transformation in vivo are discussed in relation to these observations on cell-matrix interaction.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aja.1001650102
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