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  • 1
    Electronic Resource
    Electronic Resource
    Actin-dependent myoid elongation in teleost rod inner/outer segments occurs in the absence of net actin polymerization (1992)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 21 (1992), S. 235-251 
    Details
    ISSN: 0886-1544
    Keywords: actin polymerization ; cell elongation ; photoreceptor ; cytoskeleton ; phalloidin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In the retinas of teleost fish, rod photoreceptors elongate in response to light. Light-activated elongation is mediated by the myoid of the rod inner segment and is actin-dependent. Inner segment F-actin filaments form bundles running parallel to the cell's long axis. We examined the mechanism of rod elongation using mechanically-detached rod fragments, consisting of the motile inner segment and sensory outer segment (RIS-ROS). When RIS-ROS are isolated from darkadapted green sunfish and cultured in the light, they elongate 15μm at 0.3-0.6μm/min. Elongation was inhibited 65% by 0.1μM Cytochalasin D, suggesting a requirement for actin assembly. To determine the extent of assembly during elongation, we used three approaches to measure the F-actin content in RIS-ROS: detection of pelletable actin by SDS-PAGE after detergent-extraction of RIS-ROS; quantification of fluorescein-phalloidin binding by fluorimetry, fluorescence-activated cell sorting and image analysis; estimation of total F-actin filament length by electron microscopy. All three assays indicated that no net assembly of RIS-ROS F-actin accompanied myoid elongation. An increase in F-actin content within the elongated myoid was counterbalanced by a decrease in F-actin content within the 13 microvillus-like calycal processes located at the end of the inner segment opposite to the growing myoid. O'Connor and Burnside (Journal of Cell Biology 89:517-524, 1981) showed that minus-ends of rod F-actin filaments are oriented towards the elongating myoid while plus-ends are oriented towards the shortening calycal processes. Our observations suggest that RIS-ROS elongation entails actin polymerization at the minus-ends of filaments coupled with depolymerization at the filament plus-ends.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970210307
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of light and dark on photoreceptors in the polychaete annelid Nereis limnicola (1985)
    Springer
    Cell & tissue research 242 (1985), S. 613-622 
    Details
    ISSN: 1432-0878
    Keywords: Photoreceptors, annelid, polychaete ; Light, degeneration ; Dark, regeneration ; Membrane recycling ; Endocytosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The effects of light and dark on photoreceptors of the brackish-water polychaete annelid Nereis Hmnicola were studied by electron microscopy. Animals dark-adapted for one or two days exhibited well-formed straight microvilli (rhabdomeres) on the sensory cell processes. Continuous illumination of worms for one or two days caused extensive breakdown of the microvilli into vesicles and debris. Thirty minutes to three h of exposure of dark-adapted animals to light produced increasing severity of degradation of photoreceptoral microvilli. Light-adapted worms placed in darkness for one-half to three h showed progressive restoration of the microvilli to the dark-adapted condition. The products of degradation were internalized by both sensory and pigmented supportive cells by phagocytosis and pinocytosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00225427
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  • 3
    Electronic Resource
    Electronic Resource
    Cytochemical localization of acid phosphatase in light- and dark-adapted eyes of a polychaete worm, Nereis limnicola (1985)
    Springer
    Cell & tissue research 242 (1985), S. 623-628 
    Details
    ISSN: 1432-0878
    Keywords: Photoreceptor, annelid, polychaete ; Lysosomes ; Acid phosphatase ; Membrane recycling ; Dark and light, exposure to
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The amount and distribution of the lysosomal enzyme acid phosphatase in light- and dark-adapted eyes of the brackish-water annelid Nereis limnicola were studied by standard cytochemical techniques. Precipitate from the acid phosphatase reaction was observed in Golgi-endoplasmic reticulum-lysosomal complexes, primary lysosomes, and secondary lysosomes, formed by fusion of primary lysosomes with phagocytic and pinocytic vesicles containing products of presumed rhabdomeric degradation. The acid phosphatase reaction occurred in these organelles in both sensory and supportive cells of both light- and darkadapted ocelli. Secondary lysosomes were more abundant in sensory cells of illuminated ocelli than in those maintained in the dark. Sparse reaction product was found in Golgi cisternae, none in rough endoplasmic reticulum. We suggest that the increase of lysosomal activity in light-adapted eyes is correlated with the breakdown of photosensory microvilli upon exposure to light. A diagram of our interpretation of recycling of photoreceptoral membrane in N. limnicola is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00225428
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