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  • 1980-1984  (5)
  • 1
    Electronic Resource
    Electronic Resource
    Fine structure of syzygial articulations before and after arm autotomy in florometra serratissima (Echinodermata: Crinoidea) (1981)
    Springer
    Zoomorphology 98 (1981), S. 169-183 
    Details
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary About 1 s after appropriate stimulation, arms of Florometra serratissima break at articulations called syzygies that are specialized for autotomy. The fine structure of unreacted and of newly broken syzygies is described. The unreacted syzygy includes (1) ligament fibers consisting of collagen fibrils interconnected by interfibrillar strands and (2) axons filled with presumed neurosecretory granules. The newly broken syzygy includes (1) ruptured ligament fibers consisting of swollen collagen fibrils associated with interfibrillar globules and (2) axons containing few presumed neurosecretory granules, some of which are fixed in the act of exocytosis; moreover, the calcareous skeleton adjacent to the broken syzygy is partly eroded. The observations before and after breaking suggest that the autotomy mechanism may comprise the following sequence of events: rapid neural transmission from stimulation site to syzygy triggers a massive exocytosis of granules from presumed neurosecretory axons; the released neurosecretions (which could include chelating agents, strong acids, proteolytic enzymes or enzyme activators) etch the skeleton and lower the tensile strength of the ligament fibers by weakening the collagen fibrils and/or the interfibrillar material; breakage of the ligament fibers, the major connective tissue of the articulation, is quickly followed by rupture of all the other tissues at the syzygy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00310434
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Electron microscopic studies of the digestive tract and absorption from the gut lumen of a feather star, oligometra serripinna (Echinodermata) (1984)
    Springer
    Zoomorphology 104 (1984), S. 252-259 
    Details
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The gut of a crinoid echinoderm is described for the first time by transmission electron microscopy. The gut comprises a short esophagus, a relatively long intestine and a short rectum. From the luminal side to the coelomic side, the layers of the gut wall are an inner epithelium, an epineural plexus (much reduced or absent in the intestine and rectum), haemal fluid, smooth muscles mixed with a hyponeural plexus, and a visceral peritoneum. The inner epithelium of the esophagus consists of numerous flagellated enterocytes and some mucous cells containing abundant mucous granules. The luminal surface of the esophagus, but not that of the other gut regions, is covered by a conspicuous cuticle. The inner epithelium of the intestine consists of some exocrine cells, presumably exporting digestive enzymes to the gut lumen, and numerous vesicular enterocytes that are flagellated and contain a few apical mucous granules. The inner epithelium of the rectum is made up entirely of vesicular enterocytes most of which lack a flagellum. The uptake of macromolecules from the gut lumen was demonstrated by feeding the feather stars food mixed with ferritin. By 4 h after feeding, ferritin was identified in presumed secondary lysosomes within the enterocytes of the esophagus and within the vesicular enterocytes of the intestine and rectum. The functional implications of the new fine structural results are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00312039
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Electron microscopy of extracellular materials during the development of a sea star, Patiria miniata (Echinodermata: Asteroidea) (1983)
    Springer
    Cell & tissue research 234 (1983), S. 193-200 
    Details
    ISSN: 1432-0878
    Keywords: Sea star ; Development ; Cuticle ; Extracellular materials ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The fine structure of conspicuous extracellular materials during the life history of a sea star (Patiria miniata) is described. The outer surface of the developing sea star is covered by two morphologically different cuticles that appear sequentially during ontogeny. The primary cuticle, which is about 120 nm thick and two-layered, is present from mid-blastula through the end of the larval stage. The secondary cuticle, which is about 1 μm thick and three-layered, first appears on the epidermis of the rudiment region of the larva and, after metamorphosis, covers the entire epidermis of the juvenile and adult stages. During ontogeny, there are only two conspicuous gut cuticles: the first lines the newly invaginated archenteron at the start of the gastrula stage, and the second lines the esophagus during the larval stage. A blastocoelic basal lamina first appears at mid-blastula and persists as subectodermal and subendodermal basal laminae. Ruthenium red-positive granules are detectable between the lateral surfaces of adjacent ectodermal cells during part of the gastrula stage; this transient intercellular material may possibly aid in lateral adhesion between cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00217412
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Electron microscopic study of the cortical reaction in eggs of the starfish (Patiria miniata) (1980)
    Springer
    Cell & tissue research 205 (1980), S. 67-76 
    Details
    ISSN: 1432-0878
    Keywords: Starfish egg ; Cortical reaction ; Vitelline coat ; Fertilization envelope ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The egg coats of a starfish (Patiria miniata) are examined before, during, and after the cortical reaction by scanning and transmission electron microscopy. The unfertilized egg is closely invested by a vitelline coat about 300 μm thick, and cortical granules are scattered in the peripheral cytoplasm. After insemination, as the cortical granules undergo exocytosis, the cortical reaction sweeps over the egg surface. Much of the material ejected from the cortical granules adheres to the inner surface of the vitelline coat as a dense layer about 40 μm thick and as scattered spheres and hemispheres, each about 1 μm in diameter. Together, the vitelline coat and the adherent cortical granule material form the fertilization envelope, which becomes separated from the plasma membrane of the egg by a perivitelline space. The perivitelline space contains some flocculent material, which is too diffuse and discontinuous to be considered a hyaline layer. Possible functions of the starfish egg coats are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00234443
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Fine structure of the cirri and a possible mechanism for their motility in stalkless crinoids (Echinodermata) (1981)
    Springer
    Cell & tissue research 214 (1981), S. 207-217 
    Details
    ISSN: 1432-0878
    Keywords: Echinoderm ; Filament bundles ; Motility ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Crinoid cirri are jointed appendages that can slowly bend and straighten. The structures causing each cirrus to move have not been identified unequivocally by light microscopy; therefore, we examined them by electron microscopy. No muscle cells were found, but a probable contractile apparatus was demonstrated in the cytoplasm of epithelial cells lining the oral and aboral coeloms running the length of the cirrus. The presumed contractile apparatus is a bundle of 5 nm filaments oriented parallel to each other and to the long axis of the appendage. We have proposed that contractile shortening of the coelomic epithelia bends the cirrus in an aboral direction, since the fulcral articulations of the skeletal ossicles are oral to the contractile tissue; this active bending is presumably opposed by an elasticity of the oral ligaments, which seem to straighten the cirrus. It is possible that ligaments of the cirrus may undergo neurosecretion-mediated changes in consistency that could lock the appendage into a rigid state; however, active contraction by the ligaments appears unlikely.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00235158
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    Paper (German National Licenses)
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