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  • 1
    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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  • 2
    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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  • 3
    Electronic Resource
    Electronic Resource
    Electrophysiological control of ciliary motor responses in the ctenophorePleurobrachia (1986)
    Springer
    Journal of comparative physiology 158 (1986), S. 311-330 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Prey capture by a tentacle of the ctenophorePleurobrachia elicits a reversal of beat direction and increase in beat frequency of comb plates in rows adjacent to the catching tentacle (Tamm and Moss 1985). 2. These ciliary motor responses were elicited in intact animals by repetitive electrical stimulation of a tentacle or the midsubtentacular body surface with a suction electrode. 3. An isolated split-comb row preparation allowed stable intracellular recording from comb plate cells during electrically stimulated motor responses of the comb plates, which were imaged by high-speed video microscopy. 4. During normal beating in the absence of electrical stimulation, comb plate cells showed no changes in the resting membrane potential, which was typically about − 60 mV. 5. Trains of electrical impulses (5/s, 5 ms duration, at 5–15 V) delivered by an extracellular suction electrode elicited summing facilitating synaptic potentials which gave rise to graded regenerative responses. 6. High K+ artificial seawater caused progressive depolarization of the polster cells which led to volleys of action potentials. 7. Current injection (depolarizing or release from hyperpolarizing current) also elicited regenerative responses; the rate of rise and the peak amplitude were graded with intensity of stimulus current beyond a threshold value of about −40 mV. 8. Increasing levels of subthreshold depolarization were correlated with increasing rates of beating in the normal direction. 9. Action potentials were accompanied by laydown (upward curvature of nonbeating plates), reversed beating at high frequency, and intermediate beat patterns. 10. TEA increased the summed depolarization elicited by pulse train stimulation, as well as the size and duration of the action potentials. TEA-enhanced single action potentials evoked a sudden arrest, laydown and brief bout of reversed beating. 11. Dual electrode impalements showed that cells in the same comb plate ridge experienced similar but not identical electrical activity, even though all of their cilia beat synchronously. 12. The large number of cells making up a comb plate, their highly asymmetric shape, and their complex innervation and electrical characteristics present interesting features of bioelectric control not found in other cilia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00603615
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  • 4
    Electronic Resource
    Electronic Resource
    Calcium activation of macrocilia in the ctenophoreBeroë (1988)
    Springer
    Journal of comparative physiology 163 (1988), S. 23-31 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Macrocilia on the lips of the ctenophoreBeroë are usually quiescent, but can be activated to beat rapidly and continuously by various stimuli. 2. During feeding, macrocilia beat actively and serve to spread the lips ofBeroë over its prey. 3. Vigorous, repetitive mechanical stimulation of the lips evokes widespread activation of macrocilia via a pathway that is probably neural. 4. Extracellular electrical stimulation (DC or bipolar pulse-trains) elicits immediate activation of macrocilia on lip pieces, but not on dissociated cells. 5. Macrocilia on lip pieces are activated to beat by high KCl artificial sea water (ASW), but not by high KCl Ca-free ASW. Continuous beating for long periods is also elicited by high Ca ASW or Mg-free ASW, but not by Ca-Mg-free ASW. Addition of La, Cd, Co or Mn (10 mM) to high KCl ASW reversibly blocks activation. Verapamil, D-600, nifedipine, or BAY K 8644 (10 μM) has no effect on KCl-induced activation, but the anticalmodulin drug W-7 (10 μM) reversibly inhibits beating. 6. Mild heat treatment dissociates macrociliary cells from lip tissue. Such isolated macrociliary cells usually beat continuously in normal sea water, and swim in circular paths. Ca-free ASW, or addition of Co or Mn to ASW, inhibits beating of dissociated cells. High KCl ASW activates beating of quiescent, isolated macrociliary cells. 7. Ca-Mg-free ASW inhibits beating of dissociated macrociliary cells, and return to Mg-free ASW activates motility, allowing one to activate macrocilia on isolated cells simply by addition of Ca. 8. These results indicate that sensory stimuli associated with feeding may excite the pharyngeal nerve net, thereby depolarizing macrociliary cells and opening voltage-sensitive Ca channels which mediate a Ca influx responsible for activation of beating.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00611993
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  • 5
    Electronic Resource
    Electronic Resource
    Motility and mechanosensitivity of macrocilia in the ctenophore Beroë (1983)
    [s.l.] : Nature Publishing Group
    Nature 305 (1983), S. 430-433 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Macrocilia are thick cylindrical organelles found in a dense band around the inner margin of the lips of beroid ctenophores. A single macrocilium is 35-40 p? long and 5 p? in diameter, and consists of - 2,500 ciliary axonemes cross-linked to one another and surrounded by a common membrane20. ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/305430a0
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  • 6
    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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  • 7
    Electronic Resource
    Electronic Resource
    A giant nerve net with multi-effector synapses underlying epithelial adhesive strips in the mouth ofBeroë (Ctenophora) (1995)
    Springer
    Journal of neurocytology 24 (1995), S. 711-723 
    Details
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We present ultrastructural evidence for the first known example of a giant nerve net in the phylum Ctenophora. The giant fibre system inBeroë underlies paired strips of adherent epithelial cells that run inside the lips. Interlocking actin-lined cell junctions between opposing adhesive strips keepBeroë's large mouth closed while the ctenophore searches for prey. The giant neurons, up to 6–8 μm in diameter, form a continuous lattice-like plexus rich in vesicles, microtubules, and ‘presynaptic triads’. A novel feature is that individual giant axons make synaptic contacts with more than one type of effector, i.e. longitudinal muscle fibres and epithelial adhesive cells. Contact of prey with sensory receptors on the lips ofBeroë induces rapid disappearance of the actin-lined adhesive cell junctions, and muscular opening of the mouth to ingest prey. Electron microscopy of food-opened mouths shows local thickening of longitudinal muscles and widening of the basal ends of epithelial cells in the adhesive strip, correlated with retraction of the adhesive epithelium into the mesoglea. Addition of 1% Triton X-100 to formaldehyde fixative in the absence of prey also elicits regional thickening of longitudinal muscles at the location of the adhesive strips (visualized by rhodamine-phalloidin staining). The giant neuron system may serve as a final common pathway to rapidly signal disassembly of actin-based junctions between adhesive cells as well as contractions of longitudinal muscles underlying the adhesive strips, thereby enablingBeroë to open its mouth rapidly to engulf prey.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01179820
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  • 8
    Electronic Resource
    Electronic Resource
    Control of reactivation and microtubule sliding by calcium, strontium, and barium in detergent-extracted macrocilia of Beroë (1989)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 12 (1989), S. 104-112 
    Details
    ISSN: 0886-1544
    Keywords: Ca2+ control ; Beroë macrocilia ; sliding disruption ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Macrocilia of the ctenophore Beroë are activated to beat continuously in the normal direction by membrane-mediated Ca2+ influx (Tamm: Journal of Comparative Physiology [A] 163:23-31, 1988a). Using saponin or Brij-58 permeabilized models of macrocilia, we show that ATP-reactivation of beating requires μM levels of free Ca2+, Ba2+, or Sr2+. Isolated macrocilia beat initially in reactivation solution (RS) containing Ca2+, Ba2+, or Sr2+ and then undergo microtubule sliding disintegration without added proteases. Addition of protease inhibitors to RS + 10-5 M Ca2+ prevents sliding disruption. Pretreatment in wash solution (containing 1 mM EGTA) without protease inhibitors, followed by RS + 10-5 M Ca2+ with protease inhibitors results in extensive sliding disintegration. However, treatment in wash solution followed by RS + protease inhibitors does not induce sliding. Therefore, Ca2+ is not required for proteolysis by endogenous proteases, but is necessary for sliding disintegration.Local iontophoretic application of Ca2+, Ba2+, or Sr2+ to permeabilized macrocilia in RS lacking these cations triggers motility and/or sliding disintegration. Extrusion of microtubules occurs from the tip or the base, depending on whether or not the macrocilium remains attached to its large actin bundle. Thin sheets of microtubules telescope out initially, due to synchronized sliding of subsets of doublet microtubules from parallel rows of axonemes.Macrocilia are one of the first examples of ATP-induced microtubule sliding which retains Ca2+ sensitivity. In addition, the finding that Ba2+ and Sr2+ also trigger active sliding provides an additional method for investigating the control of dynein-powered microtubule movements.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970120205
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  • 9
    Electronic Resource
    Electronic Resource
    Iontophoretic localization of Ca-sensitive sites controlling activation of ciliary beating in macrocilia of Beroë: The ciliary rete (1988)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 11 (1988), S. 126-138 
    Details
    ISSN: 0886-1544
    Keywords: Ca sensitivity ; macrocilia activation ; membrane rete ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Macrocilia are thick compound ciliary organelles found on the lips of the ctenophore Beroë. Each macrocilium contains several hundred axonemes enclosed by a single common membrane around the shaft of the organelle. Macrocilia are activated to beat rapidly and continuously in the normal direction by stimulus-triggered Ca influx through voltage-dependent Ca channels (Tamm, 1988). Heat-dissociated macrociliary cells are spontaneously active without depolarizing stimuli, providing Ca is present (Tamm, 1988). Here we investigate the spatial distribution of macrociliary Ca channels by iontophoretic application of extracellular Ca to different sites along quiescent, “potentially activated” macrocilia of dissociated cells in Ca-free medium. We find that Ca sensitivity for eliciting motility is highest or resides exclusively on the basal portion of the macrociliary surface. This is the first demonstration of local differences in Ca morphologically with a reticulum of unfused ciliary membranes at the base of the macrocilium. This ciliary rete is in direct communication with the surrounding sea water. It is likely that the ciliary rete provides the necessary Ca influx to trigger beating by virtue of its greater Ca conductance (i.e., density of Ca channels) and/or greater total membrane area.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970110206
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