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  • 1
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 276 (1978), S. 285-287 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Fig. 1 Stylonychia mytilus, as orientated in the experimental set-up for cinematographic (16mm, 250f.p.s.) and electrophy-siological recording, a, Cell in oblique dorsal view with right marginal cirri (Cmr) focused under a compound microscope (Zeiss interference contrast). Vertical oscilloscope ...
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 2 (1982), S. 483-496 
    ISSN: 0886-1544
    Keywords: Cilia ; Ca ; motor control ; ciliates ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have studied quantitative aspects of ciliary motor responses to membrane depolarization in the ciliate Stylonychia using voltage clamp and high-speed cinematograhpy techniques and employing computer-processing methods for evaluation. Depolarizations beyond 4 mV activate the cirri (compound cilia) which are at rest in the absence of a stimulus. The power stroke of activiated cirri is oriented toward the cell anterior. The frequency and duration of beating increase with rising depolarization. With very large positive stimuli (≥ 150 mV) activation of the response is delayed until the end of the voltage step (“off-response”). The peak frequecy is essentially unaltered during sustained depolarization. The frequency drops exponentially following repolarization of the membrane. The time constant of the decay in ciliary activity rises with the amplitude, not with the duration of the depolarization. The ciliary motor response is most adequately represented by the number of evoked ciliary cycles (ciliary work), and appears to be related to the amplitude of the depolarization.
    Additional Material: 11 Ill.
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  • 3
    ISSN: 0886-1544
    Keywords: cilia ; electric motor control ; ciliates ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have studied the motor responses to membrane hyperpolarization of the marginal cirri in Stylonychia using voltage-clamp, high-speed cinematography, and computer-processing techniques. The cirri started beating when voltage step amplitudes rose beyond 5 mV. The power stroke was oriented toward the posterior cell and (hyperpolarizing motor activation). The frequency rose slightly during a voltage step, and decreased with similar rates for 100 ms following the step end. Amplitude and duration of the step tended to increase the motor response of the cirri. The late response declined exponentially. The time constant of the decay rose with the step amplitude. Among three response parameters tested (frequency, duration, number of cycles), the number of evoked ciliary cycles was best correlated with the amplitude of the hyperpolarization. Comparisons with the responses to depolarizing voltage steps reveal similarities in the relaxation of ciliary activity which appears to be uncoupled, in part, from the electric membrane events during the voltage stimulus.
    Additional Material: 8 Ill.
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  • 4
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Additional Material: 2 Ill.
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  • 5
    ISSN: 0886-1544
    Keywords: ciliary motility ; inclination ; polarity of beating ; sliding velocity ; sliding translocation rate ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Motor responses of the frontal cirri of the ciliate Stylonychia were recorded at the axial view of the ciliary base with high-speed cinematography. Voltage-clamp applying sustained hyperpolarizing voltage steps was used to explore the properties of the ciliary cycle modulated by the membrane potential. Upon hyperpolarization between - 1 and - 13 mV, a previously inactive frontal cirrus reoriented from a neutral posture and started beating so that the axis of the beating cone of a proximal cirral segment assumed an orientation near 100° (proceeding counterclockwise from posterior = 0°) and inclination near 60° (0° = perpendicular to the cell surface). The major beating amplitude was limited to about 150°. Increasing hyperpolarization increased the spatial polarity of the cycle (ratio of major over minor amplitude, from 2 to 2.4). Rates of the power stroke increased with hyperpolarizations up to - 4 mV but were consistently smaller than those of the return stroke during the ciliary cycle (ratio: 0.4 to 0.6; = temporal polarity). Comparison of different hypothetical beat forms (0-shape, D-shape, and egg-shape) showed that the orientation-time data are the major determinants of the angular velocity and rate of reorientation of the cilium during the cycle. Geometric transformation of these data led to descriptions of the cycle of a proximal ciliary segment in terms of active sliding velocities and rates of unidirectional sliding translocation between identified doublets. Three voltage-sensitive functional parameters of the cilium - the inclination (which is noncyclic) and the rates of active sliding and sliding translocation (both of which are cyclic in nature) - are discussed as generating the spatial and temporal properties of the ciliary beat.
    Additional Material: 13 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 16 (1990), S. 251-265 
    ISSN: 0886-1544
    Keywords: Ciliary motility ; inclination ; polarity of beating ; active sliding velocity ; sliding translocation rate ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Depolarization-induced cycles of a frontal cirrus of Stylonychia were investigated by applying methods of axial-view analysis of the cilia, high-speed microcinématography, and step voltage-clamp. Rising depolarization (from 3 mV to 7ge; 30mV) increased the rate of beating from zero to maximally 58 Hz. During cyclic activity, the axis of the beat cone of a proximal segment of the cirrus was inclined by 60° (0° = perpendicular to cell surface), and was always oriented 90° counterclockwise to the power stroke. With the stimulus amplitude rising, the orientations of the power stroke and inclination were increasingly shifted in more counterclockwise directions by up to 80° After correction for inclination ( = normalization), and following planification of the track of the segment, we determined the following properties of the cycle during depolarization: The course of the cycle tended to be rounded, i.e., the ratio of major over minor amplitudes (= spatial polarity) approximated a value of 1.6 which is only two thirds of maximal spatial polarity observed during hyperpolarization. The angular velocity generally increased with rising steps of depolarization; up to +5 mV (and comparable to hyperpolarization-induced responses), the velocity maximum occurred during the return stroke. With depolarizations ≥7 mV the angular velocity maximum shifted to the power stroke so that the temporal polarity (rates of power stroke over rates of return stroke) increased from 0.4 to 1.6. Calculations of the angular velocity as referred to the proximal ciliary segment level suggest active sliding rates (between 5 and 30 nm/ms) of identified pairs of doublet microtubules. Ciliary frequency is a function of the rate of reorientation of the cyclic track; this parameter, which corresponds to the rate of translocation of active sliding between pairs of doublets, grew with the amplitude of depolarization. Translocation rates were high during transitions between the beat phases (power stroke, return stroke), and were reduced during these phases. Orientational polarograms of the mean rates of both active sliding and sliding translocation show properties of discreteness as well as continuity. The depolarization-induced changes in inclination, and the inferred patterns of sliding rate and sliding translocation rate, are compared with previous results from hyperpolarization-dependent activation of the same motor organelle.
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SYNOPSIS. Paramecia induced to perform high rates of avoiding reactions by mechanical stimulation and the action of Ba ions were instantaneously fixed with OsO4. Quantitative evaluation of the preparations revealed, among other things, metachronal stages of the transition between the ciliary patterns of swimming backward and forward. In each of the transitory stages, metachronal waves of swimming forward were found at the anterior end and waves of swimming backward at the posterior end of the animal. This confirms the so-called Párducz-scheme of avoiding reaction for the case of homogeneous chemical stimulation as well as for mechanical stimulation.
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  • 8
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Cells of Loxodes striatus were adjusted to defined culturing, experimental solution, O2-supply, temperature, and state of equilibration to be subjected to step-type transition of acceleration from normal gravity (1 g) to the weightless condition (μg) during free fall in a 500-m drop shaft. Cellular locomotion inside a vertical experimental chamber was recorded preceding transition and during 10 s of μg. Cell tracks from video records were used to separate cells gliding along a solid surface from free swimmers, and to determine gravitaxis and gravikinesis of gliding and swimming cells. With O2 concentrations ≥ 40% air saturation, gliders and swimmers showed a positive gravitaxis. In μg gravitaxis of gliders relaxed within 5 s, whereas gravitaxis relaxation of swimmers was not completed even after 10 s. Rates of horizontal gliders (319 μm/s) exceeded those of horizontal swimmers (275 μm/s). Relaxation of gravikinesis was incomplete after 10 s of μg. Analysis of the locomotion rates during the g-step transition revealed that gliders sediment more slowly than swimmers (14 versus 45 μm/s). The gravikinesis of gliders cancelled sedimentation effects during upward and downward locomotion tending to maintain cells at a predetermined level inside sediments of a freshwater habitat. At ≥ 40% air saturation, gravikinesis of swimmers augmented the speed of the majority of cells during gravitaxis, which favours fast vertical migrations of Loxodes.
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: . This essay considers the responses of Paramecium and other ciliates to the inorganic ion environment from an elec-trophysiological point of view. In reviewing data from published and unpublished sources it is shown that ions affect the cellular behaviour in multiple ways because the transmembrane potential can change due to the alteration of equilibrium potentials, ion conductances and surface charges of the membrane. Sensory input including effects from the ionic environment converge upon the membrane potential which has a temporal and spatial summing function. Hyperpolarizing and depolarizing potential shifts from the set point are near-simultaneously and omnidirectionally transmitted along the membrane including the ciliary boundaries. The membrane potential regulates ciliary motility via an intraciliary messenger, Ca2+, which can enter, and presumably leave, the cytosol directly adjacent to the ciliary motor. Integration of the responses of thousands of cilia occurs in accordance with the electrical and structural provisions of the cell. Potential-regulated motor and behavioural responses attenuate with time. This phenomenon, which has been loosely termed adaptation, has an electrophysiological basis in analogy to membrane accommodation following sustained stimulus input. The mechanisms of adaptation serve to restore, in principle, the membrane resting state and, thereby, the sensitivity to depolarizing and hyperpolarizing shifts of the membrane potential and the cell's responsiveness to environmental stimuli, respectively. For the inorganic ions involved in chemosensation the terms attractant and repellent are not applicable. They should be reserved to signalling substances which per se can define the behaviour of the cell.
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  • 10
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Different sites of theParamecium surface were mechanically stimulated with a fine-tipped glass stylus. Ciliated and deciliated specimens showed a decrease in depolarizing mechanosensitivity and a subsequent increase in hyperpolarizing mechanosensitivity, when the site of stimulation was shifted from the anterior to the posterior end of the cell. Maximal depolarizing sensitivity was observed slightly posterior to the front end of the cell. Specimens without cilia failed to produce action potentials, but no differences in mechanosensitivity were detected. Stimuli given to dorsal surfaces produced larger hyperpolarizations, or smaller depolarizations, than stimuli applied to ventral surfaces at the same latitude. In voltage-clamped cells posterior stimulation elicited outward receptor currents with 5 ms half-time of decay. Inward receptor currents following anterior stimulation decayed with half-times between 20 and 70 ms. Reversal potentials of the receptor currents became more positive, when more anterior surfaces were stimulated. Measurements of the reversal potentials in solutions with varied K and Ca concentrations showed that the posterior receptor currents are exclusively carried by K, while the anterior receptor currents are the sum of K and Ca currents. Ca and K mechanoreceptor currents cancel out in the midposterior region of the cell. Quantitative evaluations of the data suggest that the receptor potentials inParamecium occur due to activated Ca and K mechanoreceptor channels distributing over the somatic cell surface in the manner of overlapping gradients.
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