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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 278 (1994), S. 419-432 
    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
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  • 2
    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
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 275 (1994), S. 225-234 
    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
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 286 (1996), S. 547-549 
    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
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  • 5
    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
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 268 (1992), S. 71-79 
    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
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