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  • 1
    Electronic Resource
    Electronic Resource
    Organization of a phyllobranchiate gill from the green shore crab Carcinus maenas (Crustacea, Decapoda) (1990)
    Springer
    Cell & tissue research 260 (1990), S. 495-505 
    Details
    ISSN: 1432-0878
    Keywords: Cuticle ; Epithelium, branchial ; Gills ; Hemocoel ; Histology ; Ultrastructure ; Carcinus maenas (Crustacea)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The phyllobranchiate gills of the green shore crab Carcinus maenas have been examined histologically and ultrastructurally. Each gill lamella is bounded by a chitinous cuticle. The apical surface of the branchial epithelium contacts this cuticle, and a basal lamina segregates the epithelium from an intralamellar hemocoel. In animals acclimated to normal sea water, five epithelial cell types can be identified in the lamellae of the posterior gills: chief cells, striated cells, pillar cells, nephrocytes, and glycocytes. Chief cells are the predominant cells in the branchial epithelium. They are squamous or low cuboidal and likely play a role in respiration. Striated cells, which are probably involved in ionoregulation, are also squamous or low cuboidal. Basal folds of the striated cells contain mitochondria and interdigitate with the bodies and processes of adjacent cells. Pillar cells span the hemocoel to link the proximal and distal sides of a lamella. Nephrocytes are large, spherical cells with voluminous vacuoles. They are rimmed by foot processes or pedicels and frequently associate with the pillar cells. Glycocytes are pleomorphic cells packed with glycogen granules and multigranular rosettes. The glycocytes often mingle with the nephrocytes. Inclusion of the nephrocytes and glycocytes as members of the branchial epithelium is justified by their participation in intercellular junctions and their position internal to the epithelial basal lamina.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00297229
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  • 2
    Electronic Resource
    Electronic Resource
    Specializations for excitation-contraction coupling in the podial retractor cells of the starfish Stylasterias forreri (1981)
    Springer
    Cell & tissue research 218 (1981), S. 475-485 
    Details
    ISSN: 1432-0878
    Keywords: Excitation-contraction coupling ; Podium ; Retractor cells ; Starfish ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Ultrastructural examination of the podium of the asteroid echinoderm Stylasterias forreri has revealed that cells of the coelomic epithelium and cells of the retractor muscle should be considered as components of a single epithelium. The podial retractor cells are, therefore, myoepithelial in nature. This report concentrates on those ultrastructural features of the retractor cells that are most likely involved with excitation-contraction coupling. The spatial arrangement of the sarcoplasmic reticulum, the couplings between the sarcoplasmic reticulum and sarcolemma, and an intramembranous specialization of the sarcolemma are documented and discussed. Current concepts regarding the innervation of the retractor cells of the podium and the protractor cells of the ampulla are reviewed, and specific proposals for further investigation of podial innervation are outlined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00210108
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  • 3
    Electronic Resource
    Electronic Resource
    Ultrastructure of the coelomic lining in the podium of the starfish Stylasterias forreri (1981)
    Springer
    Cell & tissue research 218 (1981), S. 449-473 
    Details
    ISSN: 1432-0878
    Keywords: Coelomic lining ; Myoepithelium ; Podium ; Starfish ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Ultrastructural examination of the podium of the asteroid echinoderm Stylasterias forreri reveals that cells of the coelomic epithelium and cells of the retractor muscle are, in fact, components of a single epithelium. The basal lamina of this unified epithelium adjoins the connective tissue layer of the podium. The principal epithelial cells in the coelomic lining are the flagellated adluminal cells and the myofilament-bearing retractor cells. Adluminal cells interdigitate extensively with each other and form zonular intermediate and septate junctions at their apicolateral surfaces. The adluminal cells emit processes which extend between the underlying retractor cells and terminate on the basal lamina of the epithelium. Retractor cells exhibit unregistered arrays of thick and thin myofilaments. The periphery of the retractor cell is characteristically thrown into keel-like folds which interdigitate with the processes of neighboring cells. Specialized intermediate junctions bind the retractor cells to each other and anchor the retractor cells to the basal lamina of the epithelium. The retractor cells are not surrounded by external laminae or connective tissue envelopes. It is concluded that the coelomic lining in the podium of S. forreri is a bipartite epithelium and that the retractor cells of the podium are myoepithelial in nature. There are no detectable communicating (gap) junctions between the epithelial cells of the coelomic lining.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00210107
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  • 4
    Electronic Resource
    Electronic Resource
    Ultrastructure and differentiation of ascidian muscle (1983)
    Springer
    Cell & tissue research 230 (1983), S. 77-94 
    Details
    ISSN: 1432-0878
    Keywords: Ascidian larva ; Embryology ; Myogenesis ; Somatic striated (skeletal) muscle ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The larval muscle cells of Diplosoma macdonaldi contain subcortical and medullary myofibrils which are invested by fenestrated sheets of the sarcoplasmic reticulum. Cisternae of the sarcoplasmic reticulum are coupled with tubular invaginations of the sarcolemma. To appreciate better such uncommon features of cellular organization, six embryonic stages were selected for an ultrastructural study of myogenesis. The proliferative, synthetic, and elaborative phases of myogenesis were represented by embryos ranging from neurulae to prehatching larvae. The contractile apparatus originates during the synthetic phase of myogenesis, when thick and thin myofilaments appear in the cortical sarcoplasm at the epidermal and notochordal poles of the cell. The myofilaments promptly aggregate into unstriated fascicles, and the fascicles unite in series to establish the rudimentary myofibrils. All major sarcomeric bands, except the Z-lines, are evident along the myofibrils. Cisternae of the sarcoplasmic reticulum form peripheral couplings with the overlying sarcolemma, and they also form interior couplings with sarcolemmal invaginations from the ends of the cell. The interior couplings localize over the I-bands of the myofibrils. In the elaborative phase of myogenesis, mitochondria invade the cortical sarcoplasm, and the contractile apparatus passively shifts to the subcortex and medulla of the cell. Relocation of the myofibrils coincides with the disappearance of all peripheral couplings. Cisternae of the sarcoplasmic reticulum anastomose around the myofibrils, creating the fenestrated sheets that extend between sarcomeres. As Z-lines begin to bisect the I-bands, the perifibrillar cisternae become confluent with the cisternae in the precocious interior couplings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00216029
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