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  • 1
    Electronic Resource
    Electronic Resource
    The fine structure of neuroglia in the central nervous system of nereid polychaetes (1971)
    Springer
    Cell & tissue research 119 (1971), S. 295-308 
    Details
    ISSN: 1432-0878
    Keywords: Fine structure ; Neuroglia ; Nervous system ; Polychaetes ; Cell junctions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The principal supportive elements of the nereid central nervous system are non-neuronal cells that are referred to as supportive glia. Supportive glial cells form a conspicuous cortex in the nerve cord. The inner region of this cortex consists of closely packed processes and cell bodies of fibrous supportive glial cells that are arranged in concentric layers around the perimeter of the neuropile. The fibrous appearance of the glial cells results from dense bundles of cytoplasmic filaments. Many fibrous glial processes penetrate the neuropile and ramify among the neuronal elements. Larger, irregularly shaped cells are the chief supportive glial elements of the peripheral region of the cortex where they line the stromal sheath (neural lamella) and invest the neuronal perikarya with extensive concentric systems of lamellate processes. These glial cells usually possess a relatively undifferentiated cytoplasm with scattered glycogen granules, but occasionally have a well developed Golgi apparatus, endoplasmic reticulum and densely packed particulate glycogen. The supportive glia exhibits numerous desmosomes as well as 5-layered (“tight”) and 7-layered (“gap”) junctions. Interspersed among the supportive glial cells are non-neuronal cells referred to as granulocytes. These cells have abundant large, granular inclusions, electron lucent vesicles, plasmalemmal infoldings and microtubules. The granulocytes may be derived from undifferentiated glial cells or may represent coelomocytes that have invaded the nervous tissue.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00431288
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  • 2
    Electronic Resource
    Electronic Resource
    Electron microscopic study on the gill bars of amphioxus (Brachiostoma californiense) with special reference to Neurociliary control (1976)
    Springer
    Cell & tissue research 166 (1976), S. 167-178 
    Details
    ISSN: 1432-0878
    Keywords: Gill bars ; Fine structure ; Neurociliary control ; Neurosecretion ; Cephalochordata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Both primary and secondary (tongue) bars of the pharyngeal gill basket are covered by epithelial cells that are continuous with the cells that line the atrium. Anterior and posterior faces of the gill bars are covered with lateral ciliated cells, which possess a single cilium, ringed by microvilli, and an elaborate basal mitochondria-rootlet apparatus. Pharyngeal faces of the gill bars are covered with ciliated pharyngeal cells, atrial faces by mucus secreting atrial cells. The surface epithelium rests on a stromal septum, a flattened tube of basal lamina which dilates to form the visceral blood vessel (along the pharyngeal face) and skeletal blood vessel (along the atrial face). This basal lamina surrounds paired skeletal rods which run through the longitudinal axis of the gill bars near the atrial face. Between the skeletal rods and atrial cells of primary gill bars is a coelomic channel lined by epithelioid coelomic cells. Neuronal processes, some with neurosecretory granules, are located among the bases of the atrial cells. Some axons may contact lateral ciliated cells where the latter meet atrial cells, but synaptoid endings have not been found here or elsewhere in the gill bars. Nervous tissue has not been identified among lateral ciliated cells even though ciliary activity of these cells is supposedly regulated by atrial nervous tissue.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227038
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  • 3
    Electronic Resource
    Electronic Resource
    Further observations on the fine structure and development of the infracerebral complex (“infracerebral gland”) of Nereis limnicola (Annelida, Polychaeta) (1974)
    Springer
    Cell & tissue research 154 (1974), S. 519-531 
    Details
    ISSN: 1432-0878
    Keywords: Infracerebral complex ; Polychaeta, Nereidae ; Neurosecretion ; Fine structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The infracerebral complex consists of: (a) two types of ependymoid infracerebral cells located on the ventral surface of the brain, adjacent to a coelomic sinus and blood vessels; (b) a noncellular stroma, the neural lamella, which separates the infracerebral cells from cerebral nervous tissue; (c) two types of cerebral neurosecretory endings (one with many mitochondria) which abut on the neural lamella opposite from the infracerebral cells. The infracerebral a cells become columnar and develop abundant apical caveolae and Golgi elements in older worms. The infracerebral b cells, filled with electron opaque granules, resemble neurosecretory cells; their axon-like processes contain microtubules and make synaptoid contacts with the neural lamella. Both cell types are present in young worms of about 10 segments but the b cells, relatively abundant in younger worms, are outnumbered by a cells in mature individuals. However, during reproductive development neither a nor b cells display any structural changes which would indicate that they represent glandular tissue. Basal processes originating both from a and b cells form entanglements which become progressively more intricate during maturation. Neurosecretory endings are present in 10-segment worms and become very numerous in mature worms but at no time do they penetrate the neural lamella and contact the infracerebral cells. It is unlikely that the infracerebral cells per se constitute a gland but they are strategically located to influence the release of hormones from neurosecretory endings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00219671
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  • 4
    Electronic Resource
    Electronic Resource
    The fine structure of polychaete septate junctions (1976)
    Springer
    Cell & tissue research 174 (1976), S. 55-67 
    Details
    ISSN: 1432-0878
    Keywords: Septate junctions ; Polychaeta ; Fine structure ; Cell junctions ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Epidermal septate junctions of Nereis sp. and Cirriformia sp. fixed with OsO4 or glutaraldehyde/OsO4 display variable structure in electron micrographs. In transverse section the septa are often indistinct and obscured by opaque material that fills the junctional cleft. Septa (spaced at 180–280 Å) are more clearly defined in slightly oblique transverse section; they exhibit an electron lucent center and appear to be linked by arms. En face views of the junction show a honeycomb pattern. Cytoplasmic faces of junctional membranes are backed with plaques opposite the septa. Lanthanum used as a tracer delineates junctional structure in negative contrast. In transverse section a chain-like lattice is present in the junctional cleft. En face views show parallel rows of pleated elements often linked by arms into honeycomb arrays. Oblique sections demonstrate that these pleated elements are continuous with the chain-like lattice seen in transverse sections. Lanthanum does not pass entirely through the junction. Lanthanum reveals that the septa have a very intricate substructure, but it is difficult to visualize the architecture that could generate the various images presented by these junctions when seen in different orientations. However, it is clear that these junctions possess some features that are diagnostic of several supposedly different types of septate junctions in invertebrates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00222150
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    Paper (German National Licenses)
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