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  • 1
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    Actin pegs and ultrastructure of presumed sensory receptors of Bero� (Ctenophora) (1991)
    Springer
    Details
    Publication Date: 1991-04-01
    Print ISSN: 0302-766X
    Electronic ISSN: 1432-0878
    Topics: Biology , Medicine
    Published by Springer
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    PAPER CURRENT
  • 2
    Electronic Resource
    Electronic Resource
    The Fine Structure of the Centriolar Apparatus and Associated Structures in the Flagellates Deltotrichonympha and Koruga. I. Interphase (1973)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 20 (1973), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SYNOPSIS. An electronmicroscopic study was made of the centriolar apparatus in the rostrum of Deltotrichonympha operculata and Koruga bonita, 2 closely related hypermastigote flagellates from the Australian termite, Mastotermes darwiniensis. In interphase flagellates, the centriolar apparatus consists of 2 similar parts with a mutually perpendicular orientation. Each part contains a large, club-shaped centriolar body consisting of fibrillar and granular material, without recognizable internal symmetry or microtubules. The anterior centriolar body extends from the inner rostral wall, which is structurally related to the fibrous wall surrounding the posterior centriolar body. The 2 centriolar bodies are joined by connecting branches, which meet at 3 barren kinetosome-like structures located inside the rostrum. Thus, an interphase flagellate has 2 centriolar bodies oriented at a 90° angle to each other, like a pair of typical centrioles in an interphase metazoan cell.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.1973.tb00870.x
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  • 3
    Electronic Resource
    Electronic Resource
    The Fine Structure of the Centriolar Apparatus and Associated Structures in the Flagellates Deltotrichonympha and Koruga. II. Division (1973)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 20 (1973), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SYNOPSIS. At division of Deltotrichonympha operculata and Koruga bonita from the Australian termite, Mastotermes darwiniensis, the 2 centriolar bodies separate, each becoming a mitotic center. Spindle microtubules develop from the lower end of each centriolar body and radiate towards the elongating nucleus. A new rostrum is formed in association with each centriolar body. Thus, centriolar bodies which lack the structure of typical centrioles can nevertheless function as division centers during mitosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.1973.tb00871.x
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  • 4
    Electronic Resource
    Electronic Resource
    Diversity of macrociliary size, tooth patterns, and distribution in Beroe (Ctenophora) (1993)
    Springer
    Zoomorphology 113 (1993), S. 79-89 
    Details
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Macrocilia are compound ciliary feeding organelles found inside the mouth of beroid ctenophores. Each macrocilium contains multiple 9+2 axonemes surrounded by a common membrane and bears a distinct capping structure at the distal end. The cap consists of extensions of axonemal microtubules that are embedded in an electron-dense matrix to form pointed projections or teeth. The teeth change from a straight to a hooked configuration during the beat cycle of macrocilia, and these changes in tip shape are thought to aid ingestion and/or breakup of prey. Using light and electron microscopy we found a remarkable diversity in macrociliary size, tooth pattern, and distribution among “traditional” morphospecies of Beroe. These differences distinguish two major groups of Beroida. Group 1 includes most of the described nominal species [B. cucumis, B. abyssicola, B. ovata, B. gracilis, and B. sp. (Gloria)]. Their macrocilia are relatively small (typically 25–30 μm long, 5 μm diameter) and are restricted to a band around the inside of the lips. Two main types of macrociliary tooth patterns are found: 3–12 equally-sized teeth [B. cucumis (Mon), B. ovata, B. sp. (Gloria)] or 3 teeth with the middle tooth being larger (B. cucumis (CC), B. gracilis) or smaller (B. abyssicola). Group 2 species (B. forskali, B. mitrata) have greatly flattened bodies and wide mouths. Their macrocilia cover an extensive area of the stomodaeal cavity, and are longer and stouter (80–100 μm long, 12–15 μm in diameter). The shaft of the macrocilium is not hexagonal in transverse section, as in Group 1 species, but is wedge-shaped, being broader on the recovery-stroke (oral) side. The macrociliary tips are blunt and finely serrated, bearing one or more rows of 10–12 short teeth running at right angles to the beat plane. This diversity in macrociliary patterns is apparently related to differences in diet, feeding methods, and/or mechanism of prey digestion among various species. However, direct evidence for the functional significance of macrociliary diversity has not yet been obtained. The macrociliary patterns may be useful for clarifying problems of species identification and relationships within the Beroida. In particular, macrociliary differences found between and within traditionally distinguished morphospecies of Beroe raise the possibility of the existence of complexes of sibling species in this group.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00403086
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  • 5
    Electronic Resource
    Electronic Resource
    Ca/Ba/Sr-induced conformational changes of ciliary axonemes (1990)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 17 (1990), S. 187-196 
    Details
    ISSN: 0886-1544
    Keywords: axonemal shape changes ; Ca/Ba/Sr ; macrocilia ; Beroë ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Macrocilia of the ctenophore Beroë undergo Ca/Ba/Sr-dependent activation of ciliary beating and microtubule sliding disintegration [Tamm, J. Comp. Physiol. A163:23-31. 1988a: Tamm, Cell Motil. Cytoskeleton 11:126-138, 1988b; Tamm, Cell Motil. Cytoskeleton 12:104-112, 1989: Tamm and Tamm, Proc. Natl. Acad. Sci. U.S.A. 86:6987-6991, 1989]. Here we report that detergent-extracted macrocilia show an ATP-independent conformational change in response to high concentrations of Ca. Ba. or Sr ions. When applied locally by iontophoresis, these ions induce a rapid planar curvature of the distal end of the macrociliary shaft, followed by a slower relaxation to the rest position. Tip curling occurs in a direction opposite to the physiological Ca/Ba/Sr response. When applied uniformly in the bath, a threshold concentration of 10-1 M Sr is required to induce curling of the tip, and the distal ends remain curved. Calmodulin antagonists do not inhibit the tip curling response.Previous workers found that Ca induces changes in the helical shape of isolated doublet microtubules [Miki-Noumura and Kamiya, Exp. Cell Res. 97:451-453, 1976: Miki-Noumura and Kamiya. J. Cell Biol. 81:355-360, 1979; Takasaki and Miki-Noumura. J. Mol. Biol. 158:317-324, 1982] and sperm axonemes [Okuno and Brokaw, Cell Motil. 1:349-362. 1981] and suggested that conformational changes in microtubules may play a role in Ca regulation of ciliary motility. We propose that the Ca/Ba/Sr-induced curling of the macrociliary tip is due to similar helical changes of doublet microtubules, some of which in macrocilia are prevented from sliding by permanent connections (compartmenting lamellae) between adjacent axonemes within the shaft. Although the tip curling response does not appear to be directly relevant to the physiological Ca response of macrocilia, it provides a novel system for investigating Ca-induced conformational changes of microtubules independent of dynein-powered active sliding.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970170306
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  • 6
    Electronic Resource
    Electronic Resource
    Massive actin bundle couples macrocilia to muscles in the ctenophore Beroë (1987)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 7 (1987), S. 116-128 
    Details
    ISSN: 0886-1544
    Keywords: actin filament bundle ; macrociliary cell ; Clenophores ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Macrocilia are thick compound ciliary organlles arising individually from elongated epithelial cells on the lips of beroid ctenophores. A giant wedge-shaped bundle of microfilaments extends 25-30 μm from the base of each macrocilium to the lower end of the cell, terminating at a junction with an underlying smooth muscle cell. The broad end of the microfilament bundle is anchored to the macrocilium by striated rootlet fibers that extend from the basal bodies into the bundle and are linked to the microfilaments by periodic bridges. Fluorescence microscopy of rhodamine-phalloidin stained intact tissue, dissociated macrociliary cells, and Triton/glycerol-isolated bundles shows that the microfilaments contain actin. The microfilaments run generally parallel to the long axis of the bundle but are not highly ordered. Filaments decorated with myosin S1 show a uniform polarity with arrowheads pointing away from the tapered membrane-associated end of the bundle. No variations in bundle length (nor changes in rootlet periodicity) were observed in tissue fixed under conditions of calcium activation. Isolated bundles did not contract in Mg-ATP, even though detached macrocilia underwent reactivated beating and sliding disintegration. Macrocilia arc used to bite through food organisms or transport prey into the stomach. The actin filament bundles probably play a supporting role as a structural linker between macrocilia and subepithelial muscle fibers and may serve as intracellular tendons lo mechanically coordinate the motor activities of macrocilia and muscles during prey ingestion.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970070204
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  • 7
    Electronic Resource
    Electronic Resource
    Actin pegs and ultrastructure of presumed sensory receptors of Beroë (Ctenophora) (1991)
    Springer
    Cell & tissue research 264 (1991), S. 151-159 
    Details
    ISSN: 1432-0878
    Keywords: Actin pegs ; Sensory receptors ; Beroë abyssicola, Beroë cucumis, Beroë sp. (Ctenophora)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary We have investigated the actin content and ultrastructure of two kinds of presumed sensory projections on the lip epidermis of beroid ctenophores. Transmission electron microscopy showed that conical pegs contain a large bundle of densely packed, parallel microfilaments. Rhodamine-phalloidin brightly stained the pegs, confirming that they contain filamentous actin. Epidermal cells with actin pegs also bear a single long cilium with an onion-root structure, previously described as arising from a different type of cell. The actin peg and onion-root cilium project side-by-side, defining a polarized axis of the cell which is shared by neighboring cells. The onion-root body is surrounded by a flattened membranes sac which lies immediately below the plasma membrane. The perimeter of the membrane sac is encircled by aggregates of dense material. An extra layer of dense material is found along the side of the membrane sac facing the peg; this material often makes direct contact with the adjacent actin filament bundle. Cells with actin pegs and onion-root cilia synapse onto adjacent neurites and secretory gland cells, indicating that one or both types of projections are sensory elements. Since the feeding responses of beroids are reported to depend on chemical and tactile stimuli to the lips, the cells bearing pegs and cilia may function as both mechanoreceptors and chemoreceptors, that is, as double sensory receptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00305733
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