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  • 1
    Electronic Resource
    Electronic Resource
    Phosphorylation on Threonine-18 of the Regulatory Light Chain Dissociates the ATPase and Motor Properties of Smooth Muscle Myosin II (1995)
    s.l. : American Chemical Society
    Biochemistry 34 (1995), S. 12576-12583 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00039a012
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  • 2
    Electronic Resource
    Electronic Resource
    Calcium- and inositol polyphosphate-sensitivity of the calcium-sequestering endoplasmic reticulum in the photoreceptor cells of the honeybee drone (1989)
    Springer
    Journal of comparative physiology 165 (1989), S. 627-636 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The photoreceptor cells in the honeybee drone contain an elaborate Ca2+-sequestering endoplasmic reticulum (ER). We measured Ca-oxalate formation within the ER of permeabilized retinal slices with a microphotometer and studied the kinetics of Ca2+-uptake into the ER and the properties of Ins(1,4,5)P3-induced Ca2+-release. The ATP-dependent Ca2+-uptake mechanism has a high affinity for Ca2+: Uptake rate was half maximal at Ca2+ free ≈ 0.6 μM. Addition of Ins(1,4,5)P3 caused a persistent depression of Ca-oxalate formation due to Ca2+ -release from the ER. The Ins(1,4,5)P3-dependent Ca2+-release mechanism has a high affinity (half maximal rate with 0.2 μM Ins(1,4,5)P3) and a high specificity for Ins(1,4,5)P3: Ins(2,4,5)P3 was 6 times, Ins(1,3,4,5)P4 was 15 times less potent in inducing Ca2+-release. 3 μM Ins(1,4)P2 had no detectable effect. The sensitivity for Ins(1,4,5)P3 was maximal between 280 nM and 1.6 μM Ca2+ free and decreased at higher and lower Ca2+-concentrations. Our data show that the ER in invertebrate photoreceptor cells is an effective Ca2+ -sink and an Ins(1,4,5)P3-sensitive Ca2+-source. We support the idea (Payne et al. 1988) that the ER-network close to the photoreceptive membrane, the submicrovillar cisternae (SMC), are the light- and Ins(1,4,5)P3-sensitive Ca2+-stores.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00610994
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  • 3
    Electronic Resource
    Electronic Resource
    The role of actin filaments in the organization of the endoplasmic reticulum in honeybee photoreceptor cells (1994)
    Springer
    Cell & tissue research 278 (1994), S. 419-432 
    Details
    ISSN: 1432-0878
    Keywords: Photoreceptor cells ; Endoplasmic reticulum, smooth ; Cytoskeleton ; Actin filaments ; Microtubules ; Polarity ; Calcium ions ; Apis mellifera (Insecta)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Close to the bases of the photoreceptive microvilli, arthropod photoreceptors contain a dense network of endoplasmic reticulum that is involved in the regulation of the intracellular calcium concentration, and in the biogenesis of the photoreceptive membrane. Here, we examine the role of the cytoskeleton in organizing this submicrovillar endoplasmic reticulum in honeybee photoreceptors. Immunofluorescence microscopy of taxol-stabilized specimens, and electron-microscopic examination of high-pressure frozen, freeze-substituted retinae demonstrate that the submicrovillar cytoplasm lacks microtubules. The submicrovillar region contains a conspicuous F-actin system that codistributes with the submicrovillar endoplasmic reticulum. Incubation of retinal tissue with cytochalasin B leads to depolymerization of the submicrovillar F-actin system, and to disorganization and disintegration of the submicrovillar endoplasmic reticulum, indicating that an intact F-actin cytoskeleton is required to maintain the architecture of this domain of the endoplasmic reticulum. We have also developed a permeabilized cell model in order to study the physiological requirements for the interaction of the endoplasmic reticulum with actin filaments. The association of submicrovillar endoplasmic reticulum with actin filaments appears to be independent of ATP, Ca2+ and Mg2+, suggesting a tight static anchorage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00331360
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  • 4
    Electronic Resource
    Electronic Resource
    Structural interactions of actin filaments and endoplasmic reticulum in honeybee photoreceptor cells (1992)
    Springer
    Cell & tissue research 268 (1992), S. 71-79 
    Details
    ISSN: 1432-0878
    Keywords: Photoreceptor cells ; Cytoskeleton ; Actin filaments ; Endoplasmic reticulum, smooth ; Apis mellifera (Insecta)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Fluorescent phallotoxins and heavy meromyosin were used to reveal the organization of the actin cytoskeleton in honeybee photoreceptor cells, and the relationship of actin filaments to the submicrovillar, palisade-like cisternae of the endoplasmic reticulum (ER). Bundles of unipolar actin filaments (pointed end towards the cell center) protrude from the microvillar bases and extend through cytoplasmic bridges that traverse the submicrovillar ER. Within the cytoplasmic bridges, the filaments are regularly spaced and tightly apposed to the ER membrane. In addition, actin filaments are deployed close to the microvillar bases to form a loose web. Actin filaments are scarce in cell areas remote from the rhabdom; these areas contain microtubule-associated ER domains. The results suggest that the actin system of the submicrovillar cytoplasm shapes the submicrovillar ER cisternae, and that the distinct ER domains interact with different cytoskeletal elements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00338055
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  • 5
    Electronic Resource
    Electronic Resource
    The role of actin filaments in the organization of the endoplasmic reticulum in honeybee photoreceptor cells (1994)
    Springer
    Cell & tissue research 278 (1994), S. 419-432 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Photoreceptor cells ; Endoplasmic reticulum ; smooth ; Cytoskeleton ; Actin filaments ; Microtubules ; Polarity ; Calcium ions ; Apis mellifera ; (Insecta)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Close to the bases of the photoreceptive microvilli, arthropod photoreceptors contain a dense network of endoplasmic reticulum that is involved in the regulation of the intracellular calcium concentration, and in the biogenesis of the photoreceptive membrane. Here, we examine the role of the cytoskeleton in organizing this submicrovillar endoplasmic reticulum in honeybee photoreceptors. Immunofluorescence microscopy of taxol-stabilized specimens, and electron-microscopic examination of high-pressure frozen, freeze-substituted retinae demonstrate that the submicrovillar cytoplasm lacks microtubules. The submicrovillar region contains a conspicuous F-actin system that codistributes with the submicrovillar endoplasmic reticulum. Incubation of retinal tissue with cytochalasin B leads to depolymerization of the submicrovillar F-actin system, and to disorganization and disintegration of the submicrovillar endoplasmic reticulum, indicating that an intact F-actin cytoskeleton is required to maintain the architecture of this domain of the endoplasmic reticulum. We have also developed a permeabilized cell model in order to study the physiological requirements for the interaction of the endoplasmic reticulum with actin filaments. The association of submicrovillar endoplasmic reticulum with actin filaments appears to be independent of ATP, Ca2+ and Mg2+, suggesting a tight static anchorage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410050232
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Immunolocalization of the Na,K-ATPase in photoreceptor cells of the moth Manduca sexta-evidence for Na,K-ATPase on both the nonmicrovillar and the microvillar domains of the plasma membrane (1995)
    Springer
    Cell & tissue research 281 (1995), S. 119-126 
    Details
    ISSN: 1432-0878
    Keywords: Compound eye ; Photoreceptor cells ; Ion pumps ; Polarity ; Immunocytochemistry ; Manduca sexta (Insecta)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Immunohistochemical and physiological studies on various insect photoreceptors have demonstrated that the Na,K-ATPase (sodium pump) is restricted to the nonreceptive nonmicrovillar area of the plasma membrane. Here, we examined the distribution of the Na,K-ATPase in photoreceptor cells of the superposition-type compound eye in the moth Manduca sexta. Using immunofluorescent and immunogold cytochemistry, we show that the Na,K-ATPase is localized to both the nonmicrovillar and the microvillar parts of the plasma membrane. Manduca photoreceptors thus deviate from the common concept that the sodium pump and the molecular components of the photoreceptive machinery reside on different domains of the plasma membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00307965
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  • 7
    Electronic Resource
    Electronic Resource
    Immunolocalization of kinesin and cytoplasmic dynein in the retina of the locust Schistocerca gregaria (1996)
    Springer
    Cell & tissue research 286 (1996), S. 547-549 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Compound eye ; Photoreceptor cells ; Cytoskeleton ; Transport ; intracellular ; Microtubules ; Membrane turnover ; Schistocerca gregaria (Insecta)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Light stimulation of locust photoreceptors causes a translocation of submicrovillar cisternae of the endoplasmic reticulum away from the rhabdome, and a movement of mitochondria towards the rhabdome. To examine whether the microtubule cytoskeleton could be involved in these organelle movements, we have analysed the distribution of the microtubule-dependent motor proteins kinesin and cytoplasmic dynein in the retina of the locust Schistocerca gregaria. Both kinesin and cytoplasmic dynein are associated with vesicular structures that are distinct from mitochondria and the submicrovillar endoplasmic reticulum. These results, together with the previous demonstration of a lack of microtubules in the cell area of light-dependent organelle movements, provide evidence that the microtubule cytoskeleton is not involved with light-induced organelle translocations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410050725
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  • 8
    Electronic Resource
    Electronic Resource
    Immunolocalization of Na,K-ATPase in blowfly photoreceptor cells (1994)
    Springer
    Cell & tissue research 275 (1994), S. 225-234 
    Details
    ISSN: 1432-0878
    Keywords: Compound eye ; Photoreceptor cells ; Ion pumps ; Polarity ; Spectrin ; Cytoskeleton ; Immunocytochemistry ; Calliphora erythrocephala (Insecta)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The Na,K-ATPase (sodium pump) plays a central role in the physiology of arthropod photoreceptors as it re-establishes gradients for Na+ and K+ after light stimulation. We have mapped the distribution of the Na,K-ATPase in the photoreceptors of the blowfly (Calliphora erythrocephala) by immunofluorescent and immunogold cytochemistry, and demonstrate that the distribution pattern is more complex than previously presumed. High levels of sodium pumps have been detected consistently in all photoreceptors R1-8 on the nonreceptive surface, but no sodium pumps are found on the microvillar rhabdomere. Within the nonreceptive surface of the cells R1-6, however, the sodium pumps are confined to sites juxtaposed to neighboring photoreceptor or glial cells; no sodium pumps have been detected on the parts of the nonreceptive surface exposed to the intra-ommatidial space. In R7 and R8, the sodium pumps are found over the entire nonreceptive surface. The cytoskeletal protein spectrin colocalizes with the sodium pumps suggesting that linkage of the pump molecules to the spectrin-based submembrane cytoskeleton contributes to the maintenance of the complex pattern of pump distribution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00319420
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  • 9
    Electronic Resource
    Electronic Resource
    Submembrane cytoskeleton of pigmented glial cells, primary pigment cells and crystalline cone cells in the honeybee compound eye (1992)
    Springer
    Cell & tissue research 270 (1992), S. 353-363 
    Details
    ISSN: 1432-0878
    Keywords: Eye, compound ; Glia-like cells ; Pigment cells ; Cytoskeleton ; Actin filaments ; Spectrin ; Microtubules ; Apis mellifera (Insecta)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The organization of the submembrane cytoskeleton of non-photoreceptive, accessory cells in the honeybee compound eye was examined using light-microscopic (phallotoxin labeling, immunohistochemistry) and electron-microscopic (decoration with myosin fragments) techniques. The crystalline cone cells contain numerous peripheral actin filaments oriented longitudinally with antiparallel polarity. Bundles of microtubules lie under the plasma membrane of primary pigment cells, in close apposition to the crystalline cone; they are interspersed with only a few actin filaments. Pigmented glial cells (secondary pigment cells) contain a two-dimensional filament/particle web lining their entire plasma membranes. Both filamentous actin and α-spectrin are localized within the cortex of these cells, indicating that they are web components. The results demonstrate that the three cell types contain different cortical cytoskeletons, implying different functional properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00328019
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  • 10
    Electronic Resource
    Electronic Resource
    Characterization of an extremely motile cellular network in the rotifer Asplanchna spp. (2000)
    Springer
    Cell & tissue research 299 (2000), S. 159-172 
    Details
    ISSN: 1432-0878
    Keywords: Cell motility Intracellular transport Cytoskeleton Microtubules Actin filaments Asplanchna spp. (Rotifera)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The pseudocoelomic body cavity of the rotifer Asplanchna spp. contains free cells that form a highly dynamic, three-dimensional polygonal network of filopodia. Using video-enhanced differential interference contrast microscopy, we have qualitatively and quantitatively characterized the motion types involved with network motility: (1) filopodial junctions are displaced laterally at 10.52±0.46 µm/s; (2) free-ending filopodia form and extend at rates of 8.77±0.40 µm/s, until they retract again at 7.23±0.87 µm/s; (3) filopodial strands fuse either laterally or tip to the lateral side. The combination of these motion types results in enlargements, diminutions, and extinctions of filopodial polygons, and in the formation of new polygons. Moreover, there is intense and fast (5.11±0.28 µm/s) particle transport within the filopodial strands. The organization of the cytoskeleton in filopodia was examined by electron microscopy and by labeling with fluorescent-tagged phalloidin. Filopodia contain several microtubules that are often organized in a bundle. Moreover, F-actin is present within the filopodia. To characterize which of these cytoskeletal systems is involved with cell and organelle motility, we have examined cell dynamics after incubations with colchicine or cytochalasin D. The results of these pharmacological experiments provide evidence that microtubules are required for both cell and organelle motility, but that actin filaments contribute to these phenomena and are required for the structural maintenance of slender filopodia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004419900140
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