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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
    Microtubule-associated movement of mitochondria and small particles in Acanthamoeba castellanii (1995)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 32 (1995), S. 305-317 
    Details
    ISSN: 0886-1544
    Keywords: organelle transport ; cytoskeleton ; amoeba ; video microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Using video-enhanced differential interference microscopy and digital image processing, we have observed organelle motility in Acanthamoeba castellanii. In amoebae taken from cultures in rapid growth phase, mitochondria and small particles moved over distances of several microns and at an average velocity of ∼2 μ/s. Mitochondrial motility was verified by intensified fluorescence microscopy of cells that were labeled in vivo with the DNA-binding dye DAPI or the mitochondria-specific dye Mito Tracker. We further studied the role of microtubules (MTs) in the translocation of cell organelles. Double-labelling of fixed cells bules with mitochondrial markers (anti-F1β antibody, Mito Tracker) and cytoskeletal markers (anti-tubulin antibody, rhodamine-phalloidin) demonstrate that the mitochondria colocalize with MTs in the subcortical cell area and are excluded from the F-actin-rich cell cortex. Colchicine treatment resluted in an almost complete depolymerization of MTs and an inhibition of organelle motility. Moreover, we have directly visualized MTs in vivo in flattened amoebae. Mitochondria and small particles moved along the MTs in a bidirectional mode at an average velocity of ∼1 μm/s. We conclude that the observed movement of mitochondria and small particles in Acanthamoeba castellanii mainly occurs via microtubules and associated motor proteins. © 1995 Wiley-Liss, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970320407
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  • 4
    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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  • 5
    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: Key words: 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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  • 6
    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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  • 7
    Electronic Resource
    Electronic Resource
    Localization of Na/K-ATPase in developing and adult Drosophila melanogaster photoreceptors (2000)
    Springer
    Cell & tissue research 300 (2000), S. 239-249 
    Details
    ISSN: 1432-0878
    Keywords: Compound eye Ion pumps Rhodopsin Polarity Development Immunocytochemistry Drosophila melanogaster (Insecta)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Drosophila melanogaster photoreceptors are highly polarized cells and their plasma membrane is organized into distinct domains. Zonula adherens junctions separate a smooth peripheral surface, the equivalent of the basolateral surface in other epithelial cells, from the central surface (≅ apical surface). The latter consists of the microvillar rhabdomere and the juxtarhabdomeric domain, a nonmicrovillar area between the rhabdomere and the zonulae adherens. The distribution of Na/K-ATPase over these domains was examined by immunocytochemical, developmental, and genetic approaches. Immunofluorescence and immunogold labeling of adult compound eyes reveal that the distribution of Na/K-ATPase is concentrated at the peripheral surface in the photoreceptors R1–R6, but extends over the juxtarhabdomeric domain to the rhabdomere in the photoreceptors R7/R8. Developmental analysis demonstrates further that Na/K-ATPase is localized over the entire plasma membrane in all photoreceptors in early pupal eyes. Redistribution of Na/K-ATPase in R1–R6 occurs at about 78% of pupal life, coinciding with the onset of Rh1-rhodopsin expression on the central surface of these cells. Despite the essential role of Rh1 in structural development and intracellular trafficking, Rh1 mutations do not affect the distribution of Na/K-ATPase. These results suggest that Na/K-ATPase and rhodopsin are involved in distinct intracellular localization mechanisms, which are maintained independent of each other.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410000195
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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
    Immunolocalization of Na,K-ATPase in blowfly photoreceptor cells (1994)
    Springer
    Cell & tissue research 275 (1994), S. 225-234 
    Details
    ISSN: 1432-0878
    Keywords: Key words: 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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    Paper (German National Licenses)
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  • 10
    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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