Increase In Beat Frequency Research Articles

Effects of temperature on the mussel pump

The nature of the bivalve filter-pump was further elucidated in the n~ussel Mytilus edulis by investigating effects of temperature on pump and system characteristics. Pumping rates increased with temperature, linearly correlated with the temperature-determined decrease in viscosity of the water. The variation in pumping rate with temperature thus corresponded to the varying viscous resistance to water flow in the canal system of the mussel-pump. The increase in beat frequency of the lateral cilia with temperature therefore had no clear effect on the pumping rate. Also, spawning stimulation of beat frequency was without effect on pumping rates. In the back pressure-flow characteristic of fully open, active mussels, pump pressure at zero flow (AH;) was independent of temperature. Predictions based on the pump modelled as a leaky, viscous, constant-force pump were in good agreement with measured and estimated pump parameters, further supporting the concept of suspension-feeding bivalves as filter-pumps that process the ambient water autonomously that is, in the absence of physiological mechanisms for regulating water pumping.

The effects of 5-hydroxytryptamine on the isolated and intact circulatory system of the pinto abalone, Haliotis kamtschatkana, and its presence in cardiac and non-cardiac tissues

1. The in vivo and in vitro effects of 5-hydroxytryptamine (5-HT) on the circulatory system of the pinto abalone, Haliotis kamtschatkana, were examined. 2. In the isolated heart, 5-HT caused a dose-dependent increase in beat frequency. 3. In the intact animal, however, this effect was accompanied by increases in aortic systolic, diastolic, and pulse pressures and, at very high doses, efferent ctenidial pressure. 4. The effects of 5-HT were inhibited by several antagonists. 5. Furthermore, high levels of 5-HT were found in the tissue samples taken from the auricles, and ventricle and in the hemolymph, and pericardial fluid. 6. Therefore, 5-HT may have a role as an excitatory neurotransmitter in the control of circulation in H. kamtschatkana.

Intercellular communication between ciliated cells in culture.

Cultured mammalian ciliated cells from the respiratory tract respond to mechanical stimulation of their cell surface by displaying a rapid transient increase in beat frequency. Surrounding adjacent and more distal neighboring ciliated cells display a similar frequency response after a short delay that is proportional to their distance from the stimulated cell. To characterize the progression of this communicated response we developed an automated computer-assisted image-analysis system to examine high-speed films of responding cells. Transmission of the frequency response between cells occurs at 0.63 cells/s at 25 degrees C and 1.54 cells/s at 37 degrees C. We have also confirmed that gap junctions exist between cells in both epithelial explants and outgrowths and that adjacent or nonadjacent ciliated, as well as nonciliated, cells are electrically coupled. We postulate that mechanical stimulation and intercellular communication provide a mechanism to regulate beat frequency between ciliated cells in order to facilitate efficient ciliary function and mucus transport.

Effect of triton X‐100 on ultrastructure, reactivation, and motility characteristics of ram spermatozoa

AbstractFor optimal extraction and reactivation of ram sperm, glutamate, dithiothreitol, magnesium, and cyclic AMP were required in a medium of pH 7.9. On extraction with 0.01 % Triton X‐100, ram sperm were only partially demembranated, and extensive areas of plasma membrane remained intact especially in the midpiece region. Treatment with 0.1% Triton X‐100 removed all plasma membranes and extracted the mitochondrial membrane and matrix. In the absence of ATP, 16.6% ± 0.4 of the partially demembranated sperm were motile, but sperm extracted with 0.1% Triton X‐100 were completely immotile. On adding ATP partially demembranated sperm reactivated better (81.6% ± 2.8) than sperm completely demembranated in 0.1 % Triton X‐100 (39.5% ± 4.6). The release of intracellular LDH rose linearly with increasing concentrations of the detergent from 0.01 to 0.05%, at which it plateaued. There was a significant increase in beat frequency and forward velocity of partially demembranated sperm when treated with ATP. Partially demembranated sperm had intact mitochondria that presumably were still able to produce ATP, although the spermatozoan movement was stimulated by exogenous ATP.

The evolution of hamster sperm motility during capacitation and interaction with the ovum vestments in vitro

AbstractMovement characteristics of golden hamster spermatozoa were studied upon collection from the cauda epididymis, during an incubation which capacitates the spermatozoa in vitro, during penetration of the cumulus, and during attachment to and penetration of the zona pellucida. High‐speed videomicrography was employed to quantitate flagellar beat frequency and shape. The status of the acrosome was also assessed. During capacitation, hamster spermatozoa become increasingly invigorated before the onset of hyperactivated motility. Within the cumulus, beat frequency and curvature are reduced, apparently in response to the physical resistive properties of the matrix material. These properties appear to vary within the cumulus. Initial attachment to the zona precedes completion of the acrosome reaction, is non‐rigid, and is accompanied by increased beat frequency and curvature. Subsequently, the onset of rigid binding to the zona, completion of the acrosome reaction, and increased flagellar beat frequency are very closely associated in time. The latter produces an increase in thrust against the zona. Preliminary results indicate that ensuing zona penetration requires not more than five minutes, is at oblique angles, and is associated with a continuation of vigorous flagellar beating.

Electrophysiological control of ciliary motor responses in the ctenophore Pleurobrachia.

Prey capture by a tentacle of the ctenophore Pleurobrachia elicits a reversal of beat direction and increase in beat frequency of comb plates in rows adjacent to the catching tentacle (Tamm and Moss 1985). These ciliary motor responses were elicited in intact animals by repetitive electrical stimulation of a tentacle or the midsubtentacular body surface with a suction electrode. An isolated split-comb row preparation allowed stable intracellular recording from comb plate cells during electrically stimulated motor responses of the comb plates, which were imaged by high-speed video microscopy. During normal beating in the absence of electrical stimulation, comb plate cells showed no changes in the resting membrane potential, which was typically about -60 mV. Trains of electrical impulses (5/s, 5 ms duration, at 5-15 V) delivered by an extracellular suction electrode elicited summing facilitating synaptic potentials which gave rise to graded regenerative responses. High K+ artificial seawater caused progressive depolarization of the polster cells which led to volleys of action potentials. Current injection (depolarizing or release from hyperpolarizing current) also elicited regenerative responses; the rate of rise and the peak amplitude were graded with intensity of stimulus current beyond a threshold value of about -40 mV. Increasing levels of subthreshold depolarization were correlated with increasing rates of beating in the normal direction. Action potentials were accompanied by laydown (upward curvature of nonbeating plates), reversed beating at high frequency, and intermediate beat patterns. TEA increased the summed depolarization elicited by pulse train stimulation, as well as the size and duration of the action potentials. TEA-enhanced single action potentials evoked a sudden arrest, laydown and brief bout of reversed beating. Dual electrode impalements showed that cells in the same comb plate ridge experienced similar but not identical electrical activity, even though all of their cilia beat synchronously. The large number of cells making up a comb plate, their highly asymmetric shape, and their complex innervation and electrical characteristics present interesting features of bioelectric control not found in other cilia.

Calcium control of ciliary reversal in ionophore-treated and ATP-reactivated comb plates of ctenophores.

Previous work showed that ctenophore larvae swim backwards in high-KCl seawater, due to a 180 degrees reversal in the direction of effective stroke of their ciliary comb plates (Tamm, S. L., and S. Tamm, 1981, J. Cell Biol., 89: 495-509). Ion substitution and blocking experiments indicated that this response is Ca2+ dependent, but comb plate cells are innervated and presumably under nervous control. To determine whether Ca2+ is directly involved in activating the ciliary reversal mechanism and/or is required for synaptic triggering of the response, we (a) determined the effects of ionophore A23187 and Ca2+ on the beat direction of isolated nerve-free comb plates dissociated from larvae by hypotonic, divalent cation-free medium, and (b) used permeabilized ATP-reactivated models of comb plates to test motile responses to known concentrations of free Ca2+. We found that 5 microM A23187 and 10 mM Ca2+ induced dissociated comb plate cells to beat in the reverse direction and to swim counterclockwise in circular paths instead of in the normal clockwise direction. Detergent/glycerol-extracted comb plates beat actively in the presence of ATP, and reactivation was reversibly inhibited by micromolar concentrations of vanadate. Free Ca2+ concentrations greater than 10(-6)M caused reversal in direction of the effective stroke but no significant increase in beat frequency. These results show that ciliary reversal in ctenophores, like that in protozoa, is activated by an increase in intracellular free Ca2+ ions. This allows the unique experimental advantages of ctenophore comb plate cilia to be used for future studies on the site and mechanism of action of Ca2+ in the regulation of ciliary motion.

Electrophysiological investigation of the antennal heart of Periplaneta americana and its reactions to proctolin

Some physiological parameters of the antennal heart, an accessory circulatory organ in the head of Periplaneta americana and the effect of the neuropeptide proctolin on it were investigated. The beat frequency of the antennal heart in vivo or semiisolated is about 2–3 times slower than that of the dorsal vessel and not coordinated with the latter. The extracellular ECG of the antennal heart has a simple biphasic shape with a total duration of 588.7 ± 38.2 ms. Intracellularly recorded parameters showed characteristics typical of myogenic rhythmicity: a slow depolarization with a rate of rise of 7.5 ± 0.7 mV/s, followed by an action potential of 54.9 ± 1.2 mV with a relatively long duration of 201.6 ± 10.8 ms, absence of overshoots and resistance to TTX. Proctolin produced a marked enhancement of the frequency of beat of the antennal heart up to about 400% with a high sensitivity (threshold concentrations: 5·10 −9M). The dose-response curve shows a linear relationship between the logarithm of the concentration and the percentage increase in beat frequency. The electrical event most influenced by proctolin was the slow pacemaker depolarization, whose rate of rise was enhanced up to 240%. The action potential remained unchanged; the depolarization of the resting potential was very small and the input resistance did not change. The antennal heart responds to neurohormone D, another neuropeptide in insects, in a similar way as it does to proctolin. The mode of action of proctolin on the antennal heart is discussed in comparison to that found in other systems.

Effect of repeat irradiation on the tracheal ciliary cell activity.

Rabbit tracheas were initially irradiated with 10 Gy in vitro. A second irradiation of 10 Gy was administered 2 hours later. The initial exposure caused a 25 per cent increase of the ciliary beat frequency during the irradiation--a response which was not found during the second irradiation. Between the exposures, the beat frequency dropped to 20 per cent below the reference level, followed by an 11 per cent overshooting before the second irradiation. Tracheas placed untreated in the experimental chamber for 2 hours and subsequently irradiated with 10 Gy showed a similar pattern of ciliary activity as induced by the initial radiation exposure in the first experiment. The storage during 2 hours did thus not affect the condition of the ciliae. The absence of a great increase of the beat frequency during a second irradiation period may be explained by damages caused by the initial exposure, morphologically seen first a few days later.

A versatile and quantitative computer‐assisted photoelectronic technique used for the analysis of ciliary beat cycles

The beat cycles of rabbit tracheal cilia in culture and Mytilus laterofrontal cirri were recorded using a phototransistor, transillumination, video, and phase-contrast microscopy. The photoelectronic signal and video image of the ciliary activity were simultaneously recorded as a composite image. The photoelectronic signal was converted into a digital signal by a data acquisition system for further computer processing. By the selection of a small detector area and accurate detector alignment, a simple, repetitive photoelectronic signal representing ciliary activity was obtained. This signal records the ciliary beat frequency and demonstrates the triphasic nature of the beat cycle. The photoelectronic signal can be precisely correlated with the ciliary activity by analysis of the composite video recordings to provide the duration of the effective, recovery, and rest phases of the beat cycle. The video-photoelectronic signal correlations were verified by high-speed cinematography. High-speed films of ciliary activity were digitized, and the image density of selected pixels was analyzed by computer with respect to time and ciliary motion. These studies indicate that duration of the phases of the beat cycle are differentially reduced with increased beat frequency; the effective phase duration was quickly reduced to a minimum. This was followed by the reduction of the duration of the recovery phase to a minimum. The rest phase continues to be reduced without reaching a minimum, over the range of beat frequencies observed. These results suggest that ciliary beat frequency may be regulated either by modifying the rates of dynein-microtubule interactions or the rate of transition from one beat phase to the next.

Effects of Perfusion Pressure on the Isolated Heart of the Lobster, Panulirus Japonicus

ABSTRACT Systolic contractions of the isolated heart were usually composed of a first and second systolic contraction (FSC and SSC) which corresponded to the first and second large potentials (FLP and SLP), respectively, recorded in the cardiac muscle cells and represented excitatory junction potentials produced by impulse bursts of the large cells of the cardiac ganglion. Under constant pressure, the magnitudes of the FSC and the SSC appeared to change according to the amplitudes and durations of the FLP and the SLP. Further, the total amplitude of systole was often affected by the time of occurrence of the SSC (or the SLP). Internal perfusion pressure and heart tonus were linearly related over a considerable range. With an increase in heart tonus (0-30mg), the magnitude of the FSC was enhanced markedly in the absence of equivalent increases in the amplitude and duration of the FLP. The elevation of heart tonus was also related to an increase in beat frequency. The SSC decreased in magnitude and disappeared when the beat frequency exceeded approx. 1 Hz under high perfusion pressure. Further, the abolition of the SSC resulted in a steeper slope in the curve relating beat frequency to tonus. The SSC was absent during the decline of beating caused by rapid reduction of the pressure. The SSC was abolished by transverse cuts of the ganglionic trunk between the 4th and 5th large cells or between the 5th large and the 6th small cells, but the SSC often remained after the trunk was severed at the region between the 6th and 7th small cells. After severing the trunk, the heart still had the ability to respond to pressure as detected by a change of the beat frequency. Spontaneous slow contractions of the cardioarterial valves were often observed.

Bending patterns of chlamydomonas flagella I. Wild-type bending patterns.

Using a uniflagellate mutant of Chlamydomonas and flash photomicrography at 300 Hz, we have obtained detailed information on the forward and reverse beating modes of Chlamydomonas flagella and on the relationship between rotation of the uniflagellate cell and the bending cycle of the forward mode. Flagella ranging in length from 5 to 15.5 micron were photographed. There is a decrease in wavelength and an increase in curvature in the principal bends when the length of the flagellum is less than the normal length of 12-13 micron, but these changes are not sufficient to maintain similarity of the bending pattern. In the reverse mode, the flagellum propagates symmetrical, planar, undulatory waves with a shear amplitude which is the same as in the forward mode; there is a 19% increase in beat frequency and a similar decrease in wave length. The reorientation of the flagellar beat direction towards the axis of the cell in the reverse mode is caused both by the decrease in asymmetry of beat and by activation of sliding in the principal bends at an earlier time in the beat cycle, relative to the time of activation of sliding in reverse bends. There are additional rare modes of beating which may be related to intermediate stages in the transition between forward and reverse beating modes.

Potent inhibition of sperm motility by palytoxin

Palytoxin, produced by a stationary marine animal and one of the most toxic substances known, was used as a spear poison in ancient Hawaii to cause death by cardiovascular contracture. We report here that the motility of hamster caudal epididymal (HCE) and other sperm can be inhibited by as little as 10 −13 M palytoxin in a time-dependent manner. This inhibition manifested itself as a loss in flagellar amplitude, often accompanied by an increase in beat frequency, resulting in a loss of forward progression and ultimately cessation of movement. Similar effects were observed in sperm from guinea pigs, rabbit, cattle, sea urchins and man. Preincubation with palytoxin did not prevent the induction of motility from quiescence in HCE sperm when free calcium ion was added. However, regardless of the timing of palytoxin addition this very vigorous motility disappeared shortly after it appeared. These, plus earlier observations showing palytoxin did not cause lysis under similar conditions or inhibit the progressive motility of demembranated sperm axoneme preparations, suggest both that this large molecule acts via the plasma membrane to cause its exceedingly toxic effects and that spermatozoa may be useful for the investigation of the mechanism of action of palytoxin.

Effects of vanadate ions on action potentials and tension development in papillary muscles and cultured heart muscle cells.

In isolated and electrically driven (1/s) papillary muscles peak tension and, to a slighter degree, resting tension increased through treatment with Na3VO4 in concentrations higher than 10(-4)M. The positive inotropic effect was found to be transient. With vanadate, the resting membrane potential became more negative and rate of rise and overshoot of the action potential increased. Positivity and duration of the action potential plateau was markedly lessened by vanadate. These vanadate-induced changes of the electrical activity were not transient and hardly recovered during washout. Single cardiac cells in culture showed increased beat frequency when treated with vanadate ions in excess of 10(-4)M. This increase was fast but transient and led to cessation of spontaneous discharge. Simultaneously with the initial increase of beat frequency, maximum of rate of rise, diastolic potential and overshoot of the action potential also increased. Cells inactivated by vanadate (5 X 10(-4)M and higher concentrations) were relaxed in diastole and could be excited by intracellular stimulation.

Common pathways of interferon and hormonal action.

The action of interferon as well as polypeptide hormones has been shown to be transmissible between cells, possibly through gap-junctional transfer of secondary messenger molecules. This and other similarities between interferon and polypeptide hormones have led us to propose that there is a common cellular pathway of interferon and hormonal action. If correct, this hypothesis would predict that interferon should cause a species-specific hormonal response and a hormone should induce tissue-specific antiviral activity. If these two responses are mediated by similar secondary messengers, they should be transmissible and cross-activate cells. Here, we show that interferon caused a species-specific hormonal response (noradrenaline-like stimulation of the beat frequency of cultured mouse myocardial cells). Noradrenaline induced an interferon-like antiviral state in mouse myocardial cells but not human amnion (WISH) cells. In conditions which demonstrate interferon-induced transfer of viral resistance, exposure of co-cultures of mouse myocardial cells and WISH cells to either human interferon or noradrenaline caused an increased beat frequency in the myocardial cells and development of antiviral activity in WISH cells, respectively. These studies strongly suggest common pathways of interferon and hormonal stimulation that are transmissible between cells.