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  • 1
    Electronic Resource
    Electronic Resource
    The Role of the Contractile Vacuole in the Osmoregulation of Tetrahymena pyriformis (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: The relationship of cell size and contractile vacuole efflux to osmotic stress was studied in Tetrahymena pyriformis strain W, after transfer into fresh solutions iso- or hypoosmotic to the growth medium. Microscopic measurements of the cell and contractile vacuole dimensions, made with an image-sharing ocular at 27 C, allowed the calculation of the cell size and shape and the vacuolar efflux rate which provide a measure of osmoregulation. The contractile vacuole cycles have no homeostatic oscillations. In 0.03–0.10 osmolar solutions, the cell size and shape are constant while the vacuolar efflux rate has an inverse linear dependence upon extracellular osmolarity. Regression analyses indicate that for cells with systole faster than 0.1 sec (the major part of the population), it is only the final diastolic volume of the contractile vacuole that is related to osmotic stress while the frequency of systole is independent of osmotic stress and has a constant period of 7.7 ± 0.2 sec. Therefore, osmotic stress upon Tetrahymena is regulated by a corresponding change in the filling rate of its contractile vacuole to allow an unaltered cell size and shape. Kinetic measurements of vacuoles during diastole fit the model (dV/dt = K1-K2A), where (dV/dt) is the vacuolar filling rate and (A) is the vacuolar surface area. This dependence of vacuolar volume upon its surface area may be ascribed either to elastic components of the vacuolar membrane or to an increasing leakiness of this membrane during diastole. Mitochondrial inhibitors were used to observe the energy requirements of vacuolar operation and of intracellular secretion of water.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.1973.tb06012.x
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of folic acid upon filopodia of Dictyostelium discoideum vegetative amoebae (1984)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 4 (1984), S. 129-135 
    Details
    ISSN: 0886-1544
    Keywords: amoeboid motion ; chemoattractants ; chemotaxis ; Dictyostelium ; filopodia ; folic acid ; pterins ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Living vegetative D. discoideum amoebae were studied to determine whether their filopodia respond to folic acid, a chemoattractant for these cells. Exponentially growing amoebae (ca. 10 μm diameter) exhibit 5-30 μm long filopodia; at stationary phase, aggregation competent amoebae have numerous multibranched filopodia up to 100 μm long. Folic acid was observed to stimulate production, elongation, and branching of filopodia with its effects progressively changing as the amoebae approach aggregation. Filopodial construction was also found to be dependent upon Mg2+ levels. The significance of these results is discussed with respect to progressive changes within the vegetative phase as well as to the mechanisms of amoeboid movement, pseudopodial activity, and chemotaxis.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970040206
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of pteridines on the filopodia of Dictyotelium discoideum vegetative amoebae (1986)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 6 (1986), S. 479-484 
    Details
    ISSN: 0886-1544
    Keywords: motility ; chemotaxis ; chemoattractant ; cytoskeleton ; folic acid ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Living vegetative amoebae of NC-4H Dictyostelium discoideum were studied to determine if a variety of pteridines had any effect on the filopodia. We observed that production, elongation, and branching of these filopodia were stimulated by pteridines that are chemoattractants for cells of this strain. This stimulation occurs at chemotactically effective concentrations and is observed before motility is evident. A relationship between filopodia and chemoattractant signal processing is discussed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970060506
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    Paper (German National Licenses)
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