Beat Direction Research Articles

The directions of ciliary beat on the wall of the fourth ventricle in the mouse

The directions of ciliary beat on the wall of the fourth ventricle in the mouse

Artificial deciliation causes loss of calcium-dependent responses in Paramecium

WHEN a paramecium collides with an obstacle, it reverses the direction of the effective stroke of its cilia, swims backwards for a while, and, with one or more repetitions of this ‘ciliary reversal’ response, avoids the obstacle1. When the medium is disturbed2 or when the posterior part of its body is stimulated mechanically, it swims faster than usual and escapes from the stimulus mainly by increasing the frequency of ciliary beat. The current view of the underlying mechanisms can be summarised as follows3,4. A mechanical stimulus to the anterior end of the animal deforms the cell membrane of this region, increasing the permeability to Ca2+ and causing a depolarisation which further activates the Ca2+-channels in the membrane. Thus, the depolarisation develops regeneratively towards the equilibrium potential of Ca2+. The Ca2+ which has entered the cell acts on some mechanism controlling the direction of ciliary beat to bring about ciliary reversal. On the other hand, a stimulus to the posterior end activates the K+-channels in the membrane, causing hyperpolarisation and an increase in ciliary beat frequency. Although the animal behaves as a mechanoreceptor cell in the early stages of these events, it is not clear which part of the cell transduces the mechanical stimulus to the activation of Ca2+- or K+-channels. We report here the effect of removal of cilia on the electro-physiological responses of paramecium to mechanical as well as some other stimuli.

Interactions of Membrane Potential and Cations in Regulation of Ciliary Activity in Paramecium

Ciliary activity in Paramecium was investigated in different external solutions using techniques of voltage clamp and high frequency cinematography. An increase in the external concentration of K, Ca or Mg ions decreased the resting potential. It had no effect on ciliary activity. When the membrane potential was fixed, an increase in external Ca or Mg and, to a lesser extent, an increase in K concentration, raised the frequency of normal beating or decreased the frequency of reversed beating of the cilia. Similar effects resulted from membrane hyperpolarization with constant ionic conditions. Increase in concentration of Ca, but not of Mg or K, enhanced hyperpolarization-induced augmentation of ciliary frequency. Increase in Ca concentration also specifically augmented the delayed increase in inward current during rapid hyperpolarizing clamp. The results support the view that [Ca]i regulates the frequency and direction of ciliary beating. It is suggested that the insensitivity of the ciliary motor system to elevations of the external concentrations of ions results from compensation of their effects on [Ca]i. Depolarization itself appears to increase [Ca]i while elevation of the external ion concentrations at a fixed membrane potential appears to decrease [Ca]i.

Ca2+ influx across the excitable membrane of behavioural mutants of Paramecium.

THE ciliate protozoan Paramecium has an excitable surface membrane, which depolarises in response to a sudden increase in the Na+ or K+ concentration of the medium. An influx of Ca2+ during depolarisation raises the internal Ca2+ concentration, which in turn causes the cilia to reverse their direction of beating, and the cells to swim backwards1. The swimming behaviour of Paramecium is therefore a direct and readily observable correlate of the electrophysiological state of the membrane.

Ciliary frequency and orientational responses to clamped voltage steps inParamecium

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.

Spontaneous nystagmus direction does not indicate laterality.

There have been conflicting statements made in the literature on electronystagmograms (ENG) concerning the direction of beating of spontaneous nystagmus in the presence of a damaged labyrinth. This report presents a retrospective examination of 1,220 ENGs done at Stanford over the past four years with regard to the direction of spontaneous nystagmus and the side of the diseased labyrinth. The diseased labyrinth is indicated by a hypoactive caloric response. The study showed that one cannot predict the side of the labyrinthine lesion from the direction of beating of the spontaneous nystagmus.

Calcium and flagellar response during the chemotaxis of bracken spermatozoids.

AbstractThe attraction of fern spermatozoids by secretions from the female reproductive structures, and by salts of malic acid, has long been known as a classic example of precise chemotactic orientation by motile cells. Spermatozoids of the bracken fern are attracted by the partially ionized form of malic acid, bimalate ion, and also by calcium ions. Both calcium and bimalate ions must be present for chemotactic response and for response to voltage gradients, Spermatozoids swimming up a bimalate concentration gradient swim in helical paths of abnormally small radius; if they accidentally swim down the concentration gradient the radii of their path helices become abnormally large.These observations suggest that changes in the direction of flagellar beating in response to the rate of change of bimalate ion concentration with time may be the basis for chemotactic orientation. A “coupled diffusion” hypothesis for chemo‐reception is presented, which postulates a membrane carrier which can only circulate freely in the membrane if it binds both bimalate and calcium ions. This hypothesis could explain time‐differentiation of the stimulus, the coupling of a specific stimulus — bimalate ions — to a general mediator of intracellular response — calcium ions — and the quantitative relationship between response of the spermatozoids and the chemical potential of “calcium bimalate.”

Frequency and directional responses of cilia to membrane potential changes inParamecium

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.

The relations between membrane potential and parameters of ciliary beat in free-swimming Paramecium caudatum.

ABSTRACT A method of analysing the parameters of ciliary beat as a function of membrane potential in free-swimming organisms is presented. The method obviates artefacts which may be produced on impaling small organisms with micro-electrodes. Changes in the membrane potential of Paramecium caudatum produce two effects : an increase in frequency of beat of up to (23 ± 3) % mV−1 at 25 °C for both depolarizations and hyperpolarizations which falls to zero within a few minutes, and a change in the direction of ciliary beat of (9 ± 1) degree mV-1 for depolarizations only, which in a spiralling organism do not accommodate to the field. The orientation of P. caudatum towards the cathode in an electric field is due principally to changes in the angle of ciliary beat on the cathodal side of the organism ; changes in frequency seem to be relatively unimportant. Axial spinning during normal locomotion in P. caudatum is satisfactorily accounted for by transverse components of ciliary thrust. The oblique orientation of P. caudatum near boundaries is caused by an asymmetry (geometrical or electrical or both) over the surface of the organism. Comparison with observations on extracted organisms indicates that a change in the direction of beat of 9° is associated with an increase in calcium concentration at the ciliary apparatus of about 25 %.

Ciliary activity in the human and Macaca nemestrina oviduct.

AbstractThe direction of ciliary beat has been examined in vitro in human and pig‐tailed macaque (M. nemestrina) oviducts. Ducts removed under anesthesia were slit open longitudinally while submerged in Hanks solution at 37° C, and particulate matter was applied to the mucosal surface. Contrary to previous observations in pig and rabbit oviducts, transport of particles was consistently in a downward direction, toward the proximal (uterine) end, in the two species examined in this study.

Vascular physiology of the ascidian Pyura praeputialis

Blood pressure was measured at both ends of the heart of Pyura praeputialis (Heller) after removing the tunic.For posterior anterior heart waves average upstream pressures were 23–25 mm H2O (positive): corresponding downstream pressures averaged 8 mm H2O (negative). For anterior posterior waves average upstream pressures were 17–18 mm H2O (+) and downstream values were 7–8 mm H2O (‐). Maximum pulse amplitudes recorded were about 30 mm H2O (upstream).Speed of the peristaltic wave was 25‐31 mm/s. In one experiment the speed was demonstrably different over the two halves of the heart (48 mm/s over the rear half and 29 mm/s over the front half).Number of peristaltic waves per series (i.e. between successive reversals) varied from 20 to 178. Duration of each series varied from 120 s to 690 s. Wave frequency ranged from 8 to 21 per min. Reversal frequency ranged from 5 to 30 reversals per hour.Most preparations showed periods of reduced heart activity (“rest periods”) during the the 2 4 h of the experiment. All showed spasmodic contractions of the mantle muscles which caused pressure “surges” in the vascular system.It is shown that, in both directions of beat, most or all of the pressure wave is contributed by the front half of the heart (half towards which peristaltic wave is travelling). This can be related to the “reversed spiral” structure of the heart: each “half” of the heart (i.e. each spiral) serves primarily as the pump for one direction.

Membrane Control of Ciliary Activity in the Protozoan Euplotes

ABSTRACT Membrane control of ciliary activity in the protozoan Euplotes was investigated by a combination of electrophysiological and cinematographic techniques. The anal cirri, which are quiescent in the absence of stimulation, were selected for this study. Membrane depolarization by means of injected current produced a reversal of the direction of beating (i.e. towards the cell anterior so as to make the ciliate swim backwards). Depolarization also increased the frequency of beating. Increasing depolarizations resulted in an increased number of reversed beats and increased frequency. When the membrane potential was shifted beyond + 70 mV, reversed beating did not occur until after the current pulse ended. Depolarization did not evoke reversed beating when the external calcium (Ca) concentration was reduced to 10−6 M with EGTA. Hyperpolarization caused the cirri to beat in a normal direction (i.e. towards the rear of the ciliate so as to cause the animal to swim forward). Increasing hyperpolarizations resulted in an increased number of forward beats and an increased frequency. The cell was treated with the detergent Triton X-100 to permit Ca, Mg and ATP direct access through the extracted membrane to the cell interior. At Ca concentrations below 10−7 M, Mg-ATP-reactivated cilia of Triton-extracted cells beat normally. At Ca concentrations above approximately 10−7 M the reactivated beat resembled the reversed beat in the living cell. The evidence suggests that membrane-regulated concentrations of intracellular Ca control the direction of ciliary beating. Thus, stimuli which produce an adequate Ca influx lead to ciliary reversal.

ON THE HEART OF THE ORANGE TUNICATEECTEINASCIDIA TURBINATAHERDMAN

1. The non-chambered tubular heart of the colonial ascidian Ecteinascidia turbinata is made up of a single layer of very long, thin, cross-striated and spirally-wrapped muscles. Enclosed within a large non-contractile pericardial sac, the heart and pericardium are innervated by a fine non-ganglionated network. The channels and vessels through which hemolymph circulates are non-contractile.2. In recently captured, intact, and healthy-looking tunicates over a 5 year period, the heart exhibited either prolonged diastolic arrest, prolonged highly erratic (arrhythmic) beating, or fairly rhythmical but highly variable beating with periodic reversals in beat direction. No significant differences were found in contraction rates originating from either pole of the heart.3. The heart begins to beat and reverse in the embryo and reversals continue throughout life. Synchronous reversals were not observed either between embryos from the same mother or between two or more attached individuals.4. The extremely variable character of rhythmical heart beating involves both the number and duration of complete advisceral and abvisceral cycles. The variability is not due to (a) developmental stage (embryo, tadpole, mature individuals), (b) body length, (c) time in sea table after captivity, or (d) amount of sea water in examination chamber.5. The great variability of heart rhythmicity in intact animals diminishes markedly within the first hour after isolation, if the tunicates are left undisturbed. The heart is capable of beating and reversing with remarkable uniformity for long periods both in unchanged and in constantly changing sea water in small chambers. Simple manipulation of intact tunicates can readily and quickly induce renewed and extreme cardiac variability.6. Pressing externally directly over the anterior (advisceral) pole of the heart or over the center of the heart shortly after the beginning of either the advisceral or abvisceral cycle significantly increases the rate of heart reversal.7. Hearts continue to beat and reverse for a long time after both siphons (including the "brains") are removed. When the pericardium alone of the heart itself is punctured with a fine needle or cut with scissors, the heart always stops instantly in diastole for variable periods of time. The two halves of a centrally-severed heart are capable of reversing. Heart reversals were observed after puncturing small portions of the anterior and posterior poles of the heart. When the anterior pole was completely ablated, heart beats were observed only from the posterior (abvisceral) pole. Semi-isolated hearts were never observed to beat normally and rhythmically.

Haemodynamics of Carcinus maenas (L.)

1. 1. Ventricular blood pressure consistently rises above general sinus pressure, which remains above branchio-pericardial pressure (pressures of the order of 0–15 cm water : 5 cm : 0 cm). 2. 2. During ventricular systole dorsal pericardial pressure rises (from 9 cm water to 13 cm) while ventricular pressure also rises (from 0 cm to 14 cm), and lateral pericardial pressure drops from around ambient (by about 1 cm). The dorsal pericardium seems functionally separate from the lateral pericardium and may act as an auxiliary heart chamber. 3. 3. Periodic reversal of the direction of scaphognathite beat may increase respiratory efficiency by emptying the gills of blood through a direct pressure effect.

The relation between the orientation of the central fibrils and the direction of beat in cilia ofOpalina

Metachronal waves of ciliary activity onOpalina ranarumwere instantaneously fixed, dehydrated by critical point drying, and examined with the scanning electron microscope. Photographs of waves on livingOpalinawere taken with Nomarski interference-contrast optics for comparison. Waves were also sectioned in three different planes for examination of ciliary cross-sections with the transmission electron microscope. This was done for metachronal waves travelling from anterior to posterior in some specimens and from right to left in others. Our object was to test the theory that the axis of the central pair of ciliary fibrils controls the direction of ciliary beating. The form of the wave and component parts of the beat are constant, no matter what is the direction of the wave across the animal, and comparison of the living with fixed material shows that the form is faithfully preserved. Moreover, in any region of a cilium, a line drawn through the central pair of fibrils is always at right angles to the direction of bending during both recovery and effective strokes, whatever the direction of the wave, but this observation alone does not show whether the plane of the central fibrils determines the direction of bending, or vice versa. Other considerations lead to the conclusion that the orientation of the central fibrils influences the direction of the effective stroke, but we cannot rule out the possibility that the direction of bending causes a passive twist of the central pair, especially during the recovery stroke.

Ionic mechanisms controlling behavioral responses of paramecium to mechanical stimulation.

A mechanical stimulus applied to the anterior part of Paramecium causes a transient increase in membrane permeability to calcium. This permits a calcium current to flow into the cell, causing the membrane potential to approach the equilibrium level for calcium. The transient depolarization which results elicits a reversal in the direction of ciliary beat. When the organisms are free-swimming this is seen as the reversed locomotion of Jennings' "avoiding reaction." In contrast, a mechanical stimulus applied to the posterior part results in increased permeability to potassium ions, and hence an outward potassium current. The hyperpolarization which results causes an increase in the frequency of ciliary beat in the normal direction. In free-swimming specimens this is seen as an increase in the velocity of forward locomotion.

Cilia and other surface structures of the trochophore of Harmothoë imbricata (Polychaeta).

Ciliary aggregations occur as the prototroch, neurotroch, apical system and as tufts associated with the eyes and superficial glands. The major collection of cilia is the locomotory organ or prototroch that runs around the equatorial plane of the larva. This band is composed of four contiguous rows of cells, the two medial rows bearing the long locomotory cilia. The cilia occur in clumps, with several clumps arising from each prototroch cell while both the main cells contribute to each clump. The central filaments of these cilia are orientated at right angles to the long axis of the clump, the direction of ciliary beat being at right angles to the progression of the metachronal wave along the prototroch. The neurotroch, extending from the mouth to the posterior pole of the larva, beats away from the mouth. The rate of beating is rapid, and the cilia are short. The apical area of the larva is bordered by five single lines of compound cilia that surround a few stiff cilia. All the cilia beat occasionally. A further line of cilia, the akrotroch, exists at a position halfway between the apical area and the prototroch on the same side as the mouth. These cilia beat towards the prototroch. Some of these cilia are associated with sets of glandular openings. The fine structure of the glands and cuticle is described. The glands are small mucous glands that open via a projecting pore which is encircled by rings of microvilli. They often occur in groups of four or in pairs. The cuticle is similar to that described previously for adult polychaetes.

Ionic control of the reversal response of cilia in Paramecium caudatum. A calcium hypothesis.

The duration of ciliary reversal of Paramecium caudatum in response to changes in external ionic factors was determined with various ionic compositions of both equilibration and stimulation media. The reversal response was found to occur when calcium ions bound by an inferred cellular cation exchange system were liberated in exchange for externally applied cations other than calcium. Factors which affect the duration of the response were (a) initial amount of calcium bound by the cation exchange system, (b) final amount of calcium bound by the system after equilibration with the stimulation medium, and (c) concentration of calcium ions in the stimulation medium. An empirical equation is presented which relates the duration of the response to these three factors. On the basis of these and previously published data, the following hypothesis is proposed for the mechanism underlying ciliary reversal in response to cationic stimulation: Ca(++) liberated from the cellular cation exchange system activates a contractile system which is energized by ATP. Contraction of this component results in the reversal of effective beat direction of cilia by a mechanism not yet understood. The duration of reversal in live paramecia is related to the time course of bound calcium release.

The organization and replacement of the epidermis in acoelous turbellarians

ABSTRACT Five species of acoelous turbellarians have been studied: Convoluta roscoffensis Graff, C. convoluta (Abildgaard), Aphanostoma diversicolor Oersted, Otocelis rubropunctata (Schmidt), and Avagina incola Leiper. A culture-method for C. roscoffensis is described. Experiments have been carried out with various preparative methods for electron microscopy, and a method that yields adequate results with acoel material is described. The epidermis is not syncytial, as has been maintained by some authors, but is composed of distinct, uninucleate cells. The cytoplasm of these has never been found to be continuous between cells, nor between the epidermis and the tissues that lie below it. The basal surfaces of the cells are intimately associated with the muscle layers and with other peripheral tissues. A brief account of the cytology of the epidermal cell is given. The fine structure of the cilia and their rootlets is described from observations on sectioned material and on isolated, ‘negatively stained’ specimens. The rootlets of adjacent cilia make contact with each other in such a way as to preserve a hexagonal arrangement of the cilia, and yet to allow some degree of dimensional flexibility. The organization of the ciliary array over the surface of the animal is described. The ciliary ‘streamlines’ radiate outwards in all directions from a region (occupied by the frontal gland) at the anterior tip of the animal, and converge on a point at the posterior tip. This pattern is interrupted only in small regions near the mouth and the genital openings. The directions of beat and of metachronal-wave propagation are uniformly related to each other, and to the structural pattern, at all points. Epidermal replacement has been studied experimentally in C. roscoffensis. Batches of animals were subjected to a surface-abrasive treatment, and epidermal-replacement cells were later identified in the parenchyma. The structure and situation of these is described, though their origin is not known. The findings are discussed in relation to the variety and possible functions of ciliary rootlets, and to current concepts of acoel organization.

Heat Flux Distribution Near a Crevasse

AbstractPreviously reported experimental temperature data were used to compute the two components of the heat flux vector in the ice body adjacent to a crevasse in a glacier of the ice sheet of northern Greenland. Graphical differentiation techniques were employed. The computed components were used to synthesize values of the beat flux vector, including magnitude and direction. Improved accuracy was achieved over the previously reported technique of sketching heat flow lines orthogonal to the isotherms.