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  • 1
    Digitale Medien
    Digitale Medien
    Elongated microvilli support the sea urchin embryo concentrically within the perivitelline space until hatching (1989)
    Springer
    Development genes and evolution 198 (1989), S. 85-91 
    Details
    ISSN: 1432-041X
    Schlagwort(e): Elongated microvilli ; Extracellular matrix ; Elastic support ; Hatching process ; Sea urchin embryo
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The early sea urchin embryo is supported in a concentric position within the perivitelline space by elongated microvilli which are attached to the fertilization envelope by extracellular matrix fibers. This “attachment complex,” of microvillus tip: extracellular matrix fibers: fertilization envelope, was revealed by two methods: the use of pronase or calcium-free sea water to dissolve the extracellular matrix fibers, thus causing the eggs to lose their concentric location, and the visualization of the “attachment complex” using video-enhanced differential interference contrast microscopy and transmission electron microscope images. The presence of the “attachment complex” helps in understanding two types of early developmental events: (1) the apparently continual change in microvillus length during cleavage stages which retains the embryos in their concentric position and (2) the hatching process.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02447743
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  • 2
    Digitale Medien
    Digitale Medien
    The insertion of mesenchyme cells into the ectoderm during differentiation in Sea urchin embryos (1992)
    Springer
    Development genes and evolution 201 (1992), S. 383-388 
    Details
    ISSN: 1432-041X
    Schlagwort(e): Ectodermal wall ; Mesenchyme cells ; Differentiation ; Larval skeleton ; Primitive gut
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary During the course of sea urchin development, from early blastula to pluteus larva, there are two major visible processes toward which all activities seem to be focused. They are the differentiation of the larval skeleton by the primary mesenchyme cells and the differentiation of the primitive gut by the secondary mesenchyme cells. These activities take place within the shell-like layer of epithelial cells, or ectodermal wall. The interactive role of the ectodermal wall with the mesenchyme cells is not yet clearly understood. A number of earlier studies have proposed that the ectoderm may have an inductive influence on the mesenchyme cells and that its inner surface forms a molecular template for guiding the mesenchyme cells. In this report, we suggest an additional role for the ectodermal wall. We show that some primary mesenchyme cells and secondary mesenchyme cells insert between the cells of the ectodermal wall in order to firmly anchor the anlage of the larval skeleton and primitive gut during differentiation. This mechanism may provide a physical basis for maintaining the stable positional relationship of the anlage during development.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00365126
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  • 3
    Digitale Medien
    Digitale Medien
    The contractility of elongated microvilli in early sea urchin embryos (1990)
    Springer
    Development genes and evolution 199 (1990), S. 228-236 
    Details
    ISSN: 1432-041X
    Schlagwort(e): Sea urchin embryo ; Elongated microvilli ; Contractility ; Fertilization envelope ; Extracelluar matrix
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Elongated microvilli attach the early sea urchin embryo to the fertilization envelope and support it in a concentric position within the perivitelline space. The contractility of the elongated microvilli was demonstrated in several ways. (1) During normal cleavage, these microvilli change their length to adapt to the change in shape and numbers of blastomeres. (2) When treated with calcium-free sea water, embryos become eccentrically located and the microvilli extend further than normal on one side; when returned to normal sea water, the embryos become centered again. (3) Several agents cause the fertilization envelope to become higher and thinner than normal and the elongated microvilli to extend correspondingly if treated within ten min after fertilization. In some cases, both elongated microvilli and fertilization envelope return to normal size when returned to normal sea water. (4) Fertilization in a papain solution causes the elongated microvilli and the fertilization envelope to contract to the surface of the embryo. (5) Refertilization after the papain-induced contraction can bring about the elongation of these microvilli and the elevation of the fertilization envelope a second time. It was also shown that elongated microvilli are extended immediately upon fertilization, at the same time as the short microvilli. The firm adherence of the tips of elongated microvilli to the fertilization envelope by means of extracellular matrix fibers is shown in a high voltage electron microscope stereoimage. This allows us to understand why it is that when the elongated microvilli extend or contract, the fertilization envelope also extends and contracts accordingly.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01682082
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  • 4
    Digitale Medien
    Digitale Medien
    Extracellular matrix of sea urchin and other marine invertebrate embryos (1989)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 199 (1989), S. 71-92 
    Details
    ISSN: 0362-2525
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: The extracellular matrix surrounding the sea urchin embryo (outer ECM) contains fibers and granules of various sizes which are organized in recognizable patterns as shown by ultrastructural studies, particularly stereoimaging techniques. The use of the ruthenium red method for retaining and staining the ECM, with modification of the Luft (Anatomical Record 171:347-368, 1971) method for invertebrate embryos, allows for the clarification of certain structures, particularly fiber compaction in the interzonal region, and microvillus-associated bodies.The inner ECM in the sea urchin embryo includes the basal lamina and blastocoel matrix. Stereoimages show that the fibers which are loosely distributed in the blastocoel matrix become compacted around the periphery of the blastocoel to form the basal lamina.The ruthenium red method was also used on a number of marine invertebrate embryos and larvae, representing different phyla, to facilitate comparisons between their surface coats. The similarities observed in the specimens shown suggest that ECMs are widely found on marine invertebrate eggs, embryos, and larvae, and that they resemble vertebrate ECMs and may, therefore, have similar functions.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jmor.1051990107
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