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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 22 (1975), S. 0 
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SYNOPSIS. The shock reaction of Euglena gracilis strain Z to a sudden increase in light intensity (the “direct photophobic response”) was examined by high speed cinemicrography. The response is expressed as a turning reaction toward the dorsal side of the cell, after a transduction time of 0.1–0.5 sec after the onset of stimulation. Transduction times, turning rates, and flagellar beat frequencies were measured by analyzing the filmed sequences. The experimental data are consistent with a mechanism of directional homeostasis in negative phototaxis that is based upon shading of the photoreceptor by the cell's posterior end.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 11 (1964), S. 0 
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SYNOPSIS. Mastigonemes occur on flagella of many species of Protozoa, but the only function so far proposed for the mastigonemes is to increase the effective surface of the flagellum. Locomotion of Ochromonas malhamensis, O. danica, and an unidentified marine chrysomonad was examined by means of high speed microcinematography up to 600 pictures per second. In addition, analyses were performed on the movement of the organism in a suspension of polystyrene spheres (1.17 μ in diameter). The films clearly show that the organisms move by means of a planar sine wave in the long anteriorly-directed flagellum. The wave starts at the basal end of the flagellum and progresses distally. It is apparent that the organisms are pulled forward by the action of the long flagellum, and that the flagellum does not push backward as would ordinarily be expected with a forwardly-directed sine wave.It is well known that flagellar sine waves usually start at the base, move distally, and produce a push toward the point of attachment. It also is known (2) that in Mastigamoeba a helical wave may start at the tip, progress proximally toward the base, and pull the organism. However, in the present organisms the wave begins at the base, moves distally (i.e., forward), and pulls the organism. The flagellum is a true tractellum. The theoretical calculations of Taylor (1952, Proc. Roy. Soc., 214A, 158) show that if a thin cylinder, undergoing sinuous movements produced by a traveling sine wave of active bending, has a roughness of surface which is sufficiently great and has a certain directional character, propulsion may be achieved in the direction opposite to that expected of a smooth cylinder bending in exactly the same manner. It is known that the long flagellum of the chrysomonads is pantonematic, i.e., has numerous stiff lateral mastigonemes on at least two and probably all sides. It is proposed that one function of these mastigonemes is to provide a roughness of surface which brings about this type of reversal.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 15 (1968), S. 0 
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SYNOPSIS. Paramecia immobilized on an agar surface were stimulated with pulses of 2–8 mamps/cm2 with intervals ranging from 1.0 to 1000 msec. High speed cine films (1500-6000 frames per second) of the animals' responses were analyzed to determine changes in body length and the effects on cilia and trichocysts. At current densities in the range of 1.0 mamp/cm2, rapid ciliary reversal occurred. Above this value the paramecia shortened. This body contraction can be very rapid, resulting in shortening to 95% of the body length in 0.95 msec. At all levels of stimulation, contraction of the body length occurred 1st anodally, then cathodally. Extensive trichocyst extrusion occurred 1st at the anode and later at the cathode at current densities greater than 5 mamp/cm2 in the agar. Results of this study indicate that the protoplasm of paramecia is capable of very fast contraction in response to electric stimulation and that the initial response is always anodal.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The contraction of Stentor and Blepharisma, in response to mechanical and electrical stimulation and of Spirostomum in response to mechanical stimulation is described. All three species respond to electrical stimulation by contraction of the cytoplasm, beginning at the anodal end regardless of orientation of the animal. The differences in contractile ability and shapes during contraction are discussed in relation to body form and microanatomy. Stentor and Spirostomum also respond to mechanical stimulation. Dropping a weight on the slide causes contraction of the whole body of Spirostomum, but not of Stentor. Stimulation of the oral region of Stentor by means of a vibrating needle causes a contraction of the entire body, but this sensitivity is limited to the oral region. Blepharisma does not respond to mechanical stimulation. Spirostomum and Stentor undergo rapid spontaneous contractions, but Blepharisma does not contract spontaneously.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The contraction and relaxation of Vorticella difficilis, V. campanula and Carchesium sp. were studied by high speed cinematography. In Vorticella it was shown that coiling of the stalk usually started near the zooid and spread downwards; the point of initiation bore no relation to the position of the stimulating electrodes. Contraction took about 5 msec to complete, and the fully contracted animals were 29 ± 3.9% of their original lengths. The zooids were 66 ± 5.0% and the stalks 14 ± 6.0% of their original lengths (V. difficilis). The shortening of the stalk was mostly in the form of coiling. Measurement of the myoneme length demonstrated that its real shortening was less than 10%. Thus the contraction is virtually isometric, producing a helical deformation of the stalk. As the stalk contracts it takes the form of a steeply pitched helix. This change in shape should produce rotational forces on the zooid (torque). Physical models of similar proportions produced about 1.5 revolutions of torque for similar changes in pitch. However during contraction no turning of the zooid was detected, though rotation did occur after the completion of contraction.In Carchesium the contraction is not so isometric, the myoneme apparently shortening by 20%. While the coiled shape of the contracted Vorticella stalk can be explained by its acentric structures, the stalk of Carchesium is much more symmetrical in cross-section, demonstrating that a high acentricity is not necessary for helical coiling. In all three species there seems to be some separation of the control of zooid and stalk contraction.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Electrically stimulated contraction of Spirostomum ambiguum was investigated by high speed cinematography (up to 6,000 pps). Contraction is completed in about 4 msec following a latent period of up to 30 msec. Reduction in length during contraction followed a sigmoid curve, and final length was about 50% of the original length. Contraction always started at the end of the animal directed towards the anode. When the length of each half was measured separately, it was found that the cathodal end lagged about 1 msec in all cases observed. Rate of contraction was increased when the external calcium contraction was increased, and was decreased in Ca-free and K-free solutions, but was unchanged in K-rich solutions. These results are interpreted in terms of contraction being associated with a relative increase of calcium bound to the contractile protein. The differential migration of potassium and calcium ions in an electric current would result in a temporary lowering of K+ at the anodal end of the animal, hence a relative rise would take place in the Ca++ available for binding. The results of experiments using changed calcium and potassium concentrations can be explained by this hypothesis which is in general agreement with modern work on muscle contraction and relaxation.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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