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  • 1
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    CECILIA, a versatile research tool for cellular responses to gravity (2002)
    Springer
    Details
    Publication Date: 2002-09-01
    Print ISSN: 0938-0108
    Electronic ISSN: 1875-0494
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Natural Sciences in General , Technology
    Published by Springer
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  • 2
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    The Gravikinetic Response of Paramecium is Based on Orientation-Dependent Mechanotransduction (1999)
    Springer
    Details
    Publication Date: 1999-07-07
    Print ISSN: 0028-1042
    Electronic ISSN: 1432-1904
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Published by Springer
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  • 3
    Electronic Resource
    Electronic Resource
    Frequency and directional responses of cilia to membrane potential changes inParamecium (1974)
    Springer
    Journal of comparative physiology 92 (1974), S. 293-316 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Ciliary motor reactions and membrane responses to injected current stimulation inParamecium caudatum were recorded with a combined electrophysiological and high-speed cine system to investigate relations between ciliary activity and membrane potential. The power stroke of the cilia normally directed to the right rear rotates clockwise to a more posterior orientation in response to hyperpolarizing stimulation. Depolarization induces a counterclockwise shift, usually leading to the rapid reversal of beat direction toward the anterior end (Fig. 15). Ciliary frequency is increased either with hyperpolarization or with moderate or strong depolarization of the cell membrane. The frequency response is linked to the directional response in such a way that minimal frequency occurs during transition from reversed to normal beating, and that with increasing clock-wise or counterclockwise angular deviation of the power stroke from this sector of transition the frequency of beat is increased. In the course of transition from the reversed to normal beating the cilia are inactivated, i.e. they stick out perpendicularly to the cell surface without a polarized beat. A depression in normal beating activity somewhat resembling inactivation occurs with small depolarizations. Hyperpolarization-induced frequency time courses are significantly slower than those evoked by membrane depolarization. The role of transmembrane calcium fluxes and consequent modification of intraciliary calcium concentrations is considered with regard to the observed ciliary responses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00696617
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  • 4
    Electronic Resource
    Electronic Resource
    Ciliary beating in three dimensions: Steps of a quantitative description (1992)
    Springer
    Journal of mathematical biology 30 (1992), S. 215-249 
    Details
    ISSN: 1432-1416
    Keywords: Ciliary activity ; Voltage-clamp ; 3D-t video-processing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract We document a novel approach for quantitative assessment of ciliary activity, exemplified in rapid three-dimensional cyclic motion of the frontal cirri of Stylonychia. Cells held under voltage-clamp control are stimulated by step pulses to elicit reproducible hyperpolarization- or depolarization-induced ciliary motor responses. High-speed video recording at 200 fields per second is used for imaging ciliary organelles of the same cell in two perspectives: the axial view and, following cell rotation by 90°, the lateral view. From video sequences of typically 1 s, the contours of the cirral images are determined and digitized. Computer programs are established to (1) reduce an observed image to a “ciliary axis”, (2) sort series of axes by template to generate an averaged ciliary cycle in 2D-projection, and (3) to associate the generalized axial and lateral 2D-images for generation of a sequence of three-dimensional images, which quantitatively represent the cycle in space and time. The method allows us to produce pre-determined perspectives of images selected from the ciliary cycle, and to generate stereo views for graphical representation of ciliary motion. The approach includes a potential for extraction of the complete microtubular sliding program of a cilium under reproducible electric stimulation of the ciliary membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00176150
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  • 5
    Electronic Resource
    Electronic Resource
    Mechanoreception and signal transmission in the lateral ciliated cells on the gill ofMytilus (1982)
    Springer
    Journal of comparative physiology 145 (1982), S. 351-362 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. The lateral ciliated cells of the gill epithelium ofMytilus edulis were mechanically stimulated with a fine-tipped glass stylus. The electrical responses were recorded intracellularly from the ciliated cells, and the ciliary responses were photographed. 2. Mechanical stimuli to the cilia and to the cell surface evoked a depolarizing membrane response (receptor potential) which increased with the rate of rise and the steady-state amplitude of the electric pulse driving the piezo-transducer. The effective parameter of the stimulus was the velocity of the stylus. 3. Stimulation of the cilia in various directions (four parallel and one perpendicular to the cell surface), including direct stimulation of the lateral cell, led to similar depolarizing receptor potentials. The ‘perpendicular’ stimulation was among the most effective. 4. The same electric responses were elicited from stimuli applied to any of the four rows of lateral ciliated cells. 5. The mechanically elicited depolarizing receptor potentials triggered action potentials. Such regenerative depolarizations were often missing in the isolated filament preparation, presumably due to subthreshold receptor potentials. 6. The electric membrane responses and arrest responses of the cilia following membrane depolarization were propagated with decrement along several cells. The area of the ciliary arrest responses increased with stimulus intensity extending to a maximum of 70 μm in any direction. 7. Exposure to Ca-free artificial sea water suppressed both the depolarizing receptor potential and the ciliary arrest response. Action potentials with long-lasting plateaus occurred spontaneously in the Ca-free solution. 8. Total substitution of Na with choline in artificial sea water hyperpolarized the membrane, but did not interfere with the generation of receptor potentials. Spontaneous and mechanically induced action potentials were suppressed in this solution. Electrical responses were not transmitted to the neighbouring cells, and no ciliary arrest responses were seen in the absence of external Na. 9. We conclude that mechanical stimuli impinging on the lateral cells via the cilia generate a Ca-dependent depolarizing receptor potential which elicits a Na-dependent regenerative process. The graded depolarization spreads transcellularly with decrement, and regulates the local arrest response of the cilia, which may play a role in the feeding behaviour of the mussel.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00619339
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  • 6
    Electronic Resource
    Electronic Resource
    Ciliary frequency and orientational responses to clamped voltage steps inParamecium (1975)
    Springer
    Journal of comparative physiology 104 (1975), S. 247-260 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Simultaneous voltage clamping and microcinematography were used to examine the behavior of cilia in response to prolonged hyperpolarizing and depolarizing steps in the membrane potential ofParamecium caudatum. In the absence of stimulation the cilia beat at less than 20 cycles per second with the power stroke directed toward the posterior and somewhat to the right (i.e. 4 o'clock) of the cell. 2. Hyperpolarization of the membrane results in a graded increase in frequency and a slight clockwise shift in orientation of the power stroke to a more posteriad orientation (i.e. toward 6 o'clock); peak frequencies of up to 50/sec are reached in about 4 sec, after which the beating settles to a lower steady frequency. 3. Responses to depolarization are more complex; below +3 to +5 mV the frequency drops toward a minimum. Further depolarization up to +20 mV produces a stimulus graded increase in frequency with a graded counterclockwise shift in orientation of the power stroke. 4. During maintained depolarizations the frequency of reversed beating increases with time over several seconds and then gradually decreases in frequency over a period of 30 to 60 sec during which time the orientation also relaxes toward normally directed beating. 5. With potential shifts of more than +60 mV the frequency of reversed beating becomes less, reaching a minimum between +80 and +100mV; at greater positive potential steps normal beating is reestablished. 6. During 1- to 2-sec steps of either small (1–4 mV) or large (60 to 100 mV) positive potential steps there is a progressive slowing of normally directed beating until the cilia stop and finally exhibit reversed beating. 7. In all instances ciliary orientation and frequency change together in parallel as a function of membrane voltage. Following the first second of stimulation these two parameters of movement also exhibit changes which parallel in time slow changes in current. This suggests a common regulating substance or process. 8. Evidence is discussed which indicates that it is [Ca]in, regulated by the voltage-sensitive calcium conductance of the surface membrane, which is the common agent controlling both the frequency and the direction of ciliary beating.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01379051
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  • 7
    Electronic Resource
    Electronic Resource
    Effects of cyclic nucleotides and intracellular Ca on voltage-activated ciliary beating in Paramecium (1990)
    Springer
    Journal of comparative physiology 166 (1990), S. 401-406 
    Details
    ISSN: 1432-1351
    Keywords: Ca2+ ; cAMP ; cGmP ; Ciliary frequency ; Voltage clamp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Coupling mechanisms between ciliary beating and the membrane potential in Paramecium were investigated under voltage clamp applying intracellular pressure injection of cAMP, cGMP and Ca-EGTA buffer. Ciliary responses following step changes in membrane potential were recorded by high-speed video on magnetic tape. 2. Injections of cAMP and cGMP up to millimolar concentrations caused no detectable changes in the frequency voltage relationship. A minor effect was that the ciliary reorientation towards the anterior cell end (reversal) tended to be inhibited with depolarization up to 10 mV. 3. Injection of Ca2+ into the cell clamped at the resting potential caused a transient anteriad ciliary reorientation and a simultaneous increase in the beating frequency. 4. Injection of EGTA (to buffer Ca2+ below 10−8 M) was ineffective in relation to frequency for several minutes. After this time, hyperpolarization- and depolarization activated frequency responses of EGTA-injected cells were increasingly inhibited. The ciliary reorientation following depolarization was not affected by EGTA. 5. A posterior contraction of the cell diameter was noticed upon membrane hyperpolarization. The contraction coincided in time with the increase in beating frequency. 6. The results support the view that the voltage-dependent augmentation of the ciliary beating rate is not directly mediated by an intracellular increase in either cAMP or cGMP. 7. The role of Ca2+ as intracellular messenger in the ciliary and somatic compartments is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00204813
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  • 8
    Electronic Resource
    Electronic Resource
    Gravikinesis in Paramecium: Theory and isolation of a physiological response to the natural gravity vector (1991)
    Springer
    Journal of comparative physiology 168 (1991), S. 1-12 
    Details
    ISSN: 1432-1351
    Keywords: Mechanosensation ; Gravitaxis ; Kinesis ; Paramecium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. We have investigated a physiological component of the gravitaxis of Paramecium using established mechanisms of ciliate mechanosensitivity. The horizontal, up and down swimming rates of cells, and the sedimentation of immobilized specimens were determined. Weak DC voltage gradients were applied to predetermine the Paramecium swimming direction. 2. An observed steady swimming rate is the vector sum of active propulsion (P), a possible gravity-dependent change in swimming rate (Δ), and rate of sedimentation (S). We approximated P from horizontal swimming. S was measured after cell immobilization. 3. Theory predicts that the difference between the down and up swimming rates, divided by two, equals the sum of S and Δ. Δ is supposed to be the arithmetic mean of two subcomponents, Δ a and Δ p, from gravistimulation of the anterior and posterior cell ends, respectively. 4. A negative value of Δ (0.038 mm/s) was isolated with Δ a(0.070 mm/s) subtracting from downward swimming, and Δ p(0.005 mm/s) adding to upward propulsion. The data agree with one out of three possible ways of gravisensory transduction: outward deformation of the mechanically sensitive ‘lower’ soma membrane. We call the response a negative gravikinesis because both Δ a and Δ p antagonize sedimentation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00217099
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  • 9
    Electronic Resource
    Electronic Resource
    In vivo activation of cirral movement in Stylonychia by calcium (1991)
    Springer
    Journal of comparative physiology 168 (1991), S. 687-695 
    Details
    ISSN: 1432-1351
    Keywords: Ca2+ ; Calcium binding ; Ciliary activation ; Hyperpolarization ; Voltage clamp ; Ciliate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Motor responses of cirri (= organelles consisting of bundles of cilia) in the protozoan Stylonychia are elicited by positive or negative shifts of the membrane voltage from its resting state. The same responses are evoked at voltages near the Ca2+ equilibrium potential (ECa) applying extremely positive steps under voltage clamp. Motor responses recorded at large positive voltages approaching ECa from the negative side corresponded to cirral activation following physiological depolarization from the resting potential (DCA). The hyperpolarization-induced activation of the cirri (HCA) was documented during step potentials positive to ECa, suggesting that the observed HCA of the cirri resulted from an efflux of Ca2+ from the ciliary space as compared with DCA, which is related to Ca2+ influx. The ciliary responses were graded functions of the rising outward or inward driving force for Ca2+. Slopes of reciprocal plots of response latencies near ECa as a function of membrane potential indicate a removal of Ca2+ during HCA which exceeds the free intraciliary Ca2+ content at rest. It is suggested that this excess Ca2+ is released from axonemal binding sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00224358
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  • 10
    Electronic Resource
    Electronic Resource
    Hyperpolarizing and depolarizing mechanoreceptor potentials inStylonychia (1978)
    Springer
    Journal of comparative physiology 127 (1978), S. 255-266 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The surface ofStylonychia was mechanically stimulated with a piezo-crystal driven microneedle of 0.5-2 μm distal diameter and maximal amplitudes of 13 μm. Stimulation of the anterior surface of the cell produced a membrane depolarization, while stimulation of the posterior surface elicited a hyperpolarizing response. The analysis of electric responses to mechanical stimuli, driven by pulses varied in duration, amplitude, rate and acceleration, revealed that the hyperpolarizing receptor potential (hRP) rose in parallel with the stimulus velocity. Stimulus amplitudes beyond 12 μm and at rates larger than 4 mm/s did not increase the amplitude of the membrane response. Sustained stimuli slowed down the repolarization to the resting level. Adaptation of the receptor response was seen with small and sustained velocities of the stimulating probe. The depolarizing receptor response (dRP) triggered an action potential consisting of two regenerative components, one graded, the other all-or-none. Positive conditioning current pulses reversed the polarity of the dRP which was primarily Ca-dependent (22.4 mV/log [Ca]0). The dRP was isolated from the action potential by negative membrane conditioning. The reversal potential of the hyperpolarizing receptor response was negative of the resting potential and completely K-dependent (58.5 mV/log [K]o). Submaximal hyperpolarizing and subthreshold depolarizing receptor potentials showed summation. No refractoriness of the hRP was detected. Summation of depolarizing responses beyond the threshold activated a regenerative membrane depolarization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01350116
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