Ca2+ effect on protoplasmic streaming in Nitella internodal cell

Ca²⁺ ion effect on protoplasmic streaming in an internodal cell of Nitella has been investigated for various temperatures. We have found that the protoplasmic streaming at low temperature is remarkably affected by the Ca²⁺ ions in the internodal cell but larger concentrations of the Ca²⁺ ions are needed to suppress the streaming velocity at higher temperatures. These streaming behaviors of the protoplasm, furthermore, have been elucidated on the basis of the reaction equations which take into account ATP hydrolysis due to actin-myosin molecules and inactivity of the molecules due to the Ca²⁺ ions.     

Laser light-scattering analysis of protoplasmic streaming in the slime mold Physarum polycephalum

Laser light scattering is shown to be an effective means of obtaining a rapid, objective assessment of dynamic changes in the intact plasmodium of the myxomycete Physarum polycephalum during bidirectional (shuttle) streaming. The motion of material in a 100 mum diameter region of a plasmodial vein was studied by following changes in the autocorrelation function of the fluctuations in the scattered light intensity. The autocorrelation function was recorded at 10 s intervals and analyzed to follow changes in the flow velocity of protoplasm associated with shuttle streaming. Rhythmic velocity changes and a "beating" pattern of velocity maxima were readily observed. In an attempt to locate the site of underlying structural changes in the vein responsible for the changing pattern of flow, the average scattered intensity was separated into components derived from moving and stationary scatterers. Periodic variations in the light intensity due to stationary scatterers are related to the streaming cycle and indicate the occurrence of important structural changes in the vein walls. Two possible interpretations of the data are offered; one involving gross dynamic changes in vein structure, the other involving the formation, contraction, or breakdown of fibrillar material in the vein wall during the streaming cycle.     

Studies on the velocity distribution of the protoplasmic streaming in the myxomycete plasmodium

Summary It was shown that the velocity distribution of the intracapillary streaming of protoplasm in a plasmodium ofPhysarum polycephalum is the same no matter whether the flow is spontaneous or whether it is induced artificially by external local air pressure applied to the plasmodium. Thus we conclude that the protoplasmic flow in the plasmodium is caused by local difference in endoplasm pressure. The view that the seat of the motive force responsible for the flow is located in the streaming protoplasm itself is untenable for this type of streaming.     

A study of protoplasmic streaming inPhysarum by laser Doppler spectroscopy

Summary Protoplasmic streaming in the slime moldPhysarum polycephalum has been characterized using laser Doppler spectroscopy. Measurement of the spectrum of scattered laser light permits simultaneous determination of the velocities of all particles in the laser beam, with the relative intensity from each particle proportional to its light scattering cross-section. Simple experimental modifications allow the tracking of the oscillations of the streaming velocities. Rhythmic wall contractions can be monitored simultaneously with the flow velocities. Interpretation of the Doppler spectra shows that a small fraction of the particles in the flowing protoplasm are moving with velocities two to four times greater than the characteristic velocities reported by optical microscopy. Transverse velocities in the tubes are nearly as great as the longitudinal velocities. The shape of the Doppler spectrum at the maximum of the oscillation cycle is consistent with a spatial velocity profile which is sharper than parabolic, presumably because of a viscosity gradient from the center to the walls of the plasmodial tubes. The shape of the Doppler spectrum of depolarized scattered light is of approximately the same form. The response of the plasmodium to increased temperature is an increase in the frequency of the velocity oscillations with little change in the magnitude of the velocities. The response of the plasmodium to very high intensities of laser light is to gel at the point of incidence.     

Explaining the “Pulse of Protoplasm”: The search for molecular mechanisms of protoplasmic streaming

Explanations for protoplasmic streaming began with appeals to contraction in the eighteenth century and ended with appeals to contraction in the twentieth. During the intervening years, biologists prop...     

淡黄绒泡菌和全白绒泡菌原生质流向的观察

显型原质团是绒泡菌目黏菌的营养生长阶段,其最明显的现象是往返原生质流,但一直并不清楚原生质流反向流动的原因。观察研究了淡黄绒泡菌和全白绒泡菌原质团中的原生质流,结果表明：由于菌脉中堵塞或是在原质团前缘尚未分化通道引起反向原生质流,从而引起原质团多方向生长使原质团前缘呈现扇面状。原生质流总的方向是扇面端,并完成原质团运动。     

Laser light-scattering analysis of protoplasmic streaming in the slime mold physarum polycephalum

Laser light scattering is shown to be an effective means of obtaining a rapid, objective assessment of dynamic changes in the intact plasmodium of the myxomycete Physarum polycephalum during bidirectional (shuttle) streaming. The motion of material in a 100 μm diameter region of a plasmodial vein was studied by following changes in the autocorrelation function of the fluctuations in the scattered light intensity. The autocorrelation function was recorded at 10 s intervals and analyzed to follow changes in the flow velocity of protoplasm associated with shuttle streaming. Rhythmic velocity changes and a “beating” pattern of velocity maxima were readily observed. In an attempt to locate the site of underlying structural changes in the vein responsible for the changing pattern of flow, the average scattered intensity was separated into components derived from moving and stationary scatterers. Periodic variations in the light intensity due to stationary scatterers are related to the streaming cycle and indicate the occurrence of important structural changes in the vein walls. Two possible interpretations of the data are offered; one involving gross dynamic changes in vein structure, the other involving the formation, contraction, or breakdown of fibrillar material in the vein wall during the streaming cycle.     

Steady and transient behaviors of protoplasmic streaming in Nitella internodal cell

Steady and transient behaviors of protoplasmic streaming in Nitella internodal cell have been investigated for various temperatures from 30°C to near 0°C. It has been found that steady velocity of the streaming linearly decreases with increasing inverse temperature but its proportionality coefficient changes at ~ 10°C. Velocity distribution, which reflects temporal fluctuations of the protoplasmic streaming, is nonGaussian and its half width becomes larger at higher temperatures. On the other hand, recovery of the protoplasmic streaming, which is observed after stopping the streaming with a current stimulus to the internodal cell, has been found to show more clear sigmoidal time courses at higher temperatures.     

Cytoplasmic streaming in Chara corallina studied by laser light scattering.

An apparatus is described by means of which the power versus frequency spectrum of the photomultiplier current can be obtained for laser light scattered by streaming cytoplasm in the algal cell Chara corallina. A Doppler peak is noted in the spectrum which is abolished when cytoplasmic streaming is arrested by electrical stimulation. For 5 cells of Chara, this simple laser-Doppler velocimeter gave streaming velocities (46-7 mum s-1, S.D. +/- 4-8 at 20 degrees C) similar to those obtained for the same cells using the light microscope (44-3 mum s-1, S.D. +/- 5-3 at 20 degrees C). A narrow distribution of streaming velocities is indicated. The technique described provides a rapid, quantitative assay of the in vivo rheological properties of cytoplasm.     

A PHOTOGRAPHIC ANALYSIS OF PROTOPLASMIC MOVEMENT DURING CLEAVAGE IN THE SEA URCHIN EGG

The movement of the protoplasm during cleavage was analyzed by tracing the movements of particles in the protoplasm by time-lapse microcinematography of the eggs of the heart-urchin, Clypeaster japonicus .
Three methods of analysis are used. The first is to trace protoplasmic particles in the projected image frame by frame. The second is to record the displacements of protoplasmic particles at various regions of the egg within a definite period by printing several images of the same egg on the same sheet of photographic paper. The third is to record protoplasmic movement in the cleavage plane or along the spindle axis by projecting the film at a constant frame rate through a narrow slit on a sheet of photographic paper moving at a constant speed in a direction perpendicular to the slit.
As a result of the analysis, which confirms the result of a previous study (H iramoto , 1958), it is concluded that during cleavage of the sea urchin egg there is deformation of the preexisting cortex rather than the formation of a new cortex from endoplasmic materials.     

Cyclic longitudinal fibrillar motion as a basis for steady rotational protoplasmic streaming

The simple rhythmic motion of protoplasm back and forth along microfilaments sited at the active boundary of the streaming layer of Nitellais conjectured as a possible mechanism for the motive force for protoplasmic streaming. A theoretical model is set up to illustrate the process and estimate appropriate values for time scales and velocities of such oscillations to mantain streaming velocities of the order of those measured in these cells.     

Rhythmicity in the protoplasmic streaming of a slime mold,Physarum polycephalum. II. Theoretical treatment of the electric potential rhythm

The electric potential difference (1 to 15 mv.) between two loci of the slime mold connected with a strand of protoplasm changes rhythmically with the same period (60 to 180 seconds) as that of back and forth protoplasmic streaming along the strand. When atmospheric pressure at a part of the plasmodium is increased (about 10 cm. H₂O), the electric potential at this part becomes positive (0 to 20 mv.) to another part with a time constant of 2 to 15 minutes. If the atmospheric pressure at a part of the plasmodium is changed (about 10 cm. H₂O) periodically, the electric potential rhythm also changes with the same period as that of the applied pressure change, and the amplitude of the former grows to a new level (i.e., forced oscillation). The electric potential rhythm, in this case, is generally delayed about 90° in phase angle from the external pressure change. The period of the electric potential rhythm which coincided with that of the pressure change is maintained for a while after stopping the application of the pressure change, if the period is not much different from the native flow rhythm. Such a pressure effect is brought about by the forced transport of protoplasm and is reversible as a rule. In the statistical analysis made by Kishimoto (1958) and in the rheological treatment made in the report, the rhythmic deformation of the contractile protein networks is supposed to be the cause of the protoplasmic flow along the strand and of the electric potential rhythm. The role of such submicroscopic networks in the protoplasm in various kinds of protoplasmic movement is emphasized.     

Velocity distributions of the streaming protoplasm in Nitella flexilis.

Laser light is Doppler-shifted in frequency by the streaming endoplasm of living cells of Nitella flexilis. The frequency spectrum of the scattered light can be interpreted as the histogram of velocities within the organism, with the exception of the intense low-frequency portion of the spectrum. We demonstrate that the lowest-frequency component is the result of amplitude modulation of the scattered light by the array of chloroplasts in the cell. Measurement of the streaming endoplasm in a photobleached "window" region allows correction of the frequency distribution for the modulation component. The complete velocity histogram for the streaming endoplasm is calculated directly from the corrected frequency distribution. Measurements of vacuolar and endoplasmic motions show that the tonoplast, the membrane separating the vacuole and the endoplasm, seems to be flowing along with the endoplasm and vacuolar sap. Placing the cell in medium containing ATP in concentrations greater than 10(-3) M greatly increases the contribution of low velocities to the velocity histogram. Cytochalasin B at high dosages (10-50 mug/ml) does not noticably change the shape of the velocity histogram, while at low dosages (1 mug/ml) there is an increase in the contribution of low velocities to the velocity histogram. Colchicine in high concentrations (1%) has no observable effect on the velocity histogram.     

Locomotive mechanism of Physarum plasmodia based on spatiotemporal analysis of protoplasmic streaming

We investigate how an amoeba mechanically moves its own center of gravity using the model organism Physarum plasmodium. Time-dependent velocity fields of protoplasmic streaming over the whole plasmodia were measured with a particle image velocimetry program developed for this work. Combining these data with measurements of the simultaneous movements of the plasmodia revealed a simple physical mechanism of locomotion. The shuttle streaming of the protoplasm was not truly symmetric due to the peristalsis-like movements of the plasmodium. This asymmetry meant that the transport capacity of the stream was not equal in both directions, and a net forward displacement of the center of gravity resulted. The generality of this as a mechanism for amoeboid locomotion is discussed.     

Photon correlation analysis of cytoplasmic streaming

Laser light scattering has been used to investigate particle movements in a plant cell. Intensity autocorrelation functions are obtained by digital photon correlation of laser light scattered from cells of Nitella opaca both during cytoplasmic streaming and during the transitory cessation of streaming induced by electrical stimulation. The average velocity computed from the periodic oscillation in the intensity autocorrelation function during streaming corresponds to the velocity estimated using light microscopy. An estimate of the distribution of streaming velocities has been obtained from the decay in the amplitude of the envelope of the autocorrelation function derived from a streaming cell.     

Cytoplasmic streaming inParamecium

Summary Certain species ofParamecium demonstrate rotational cytoplasmic streaming, in which most cytoplasmic particles and organelles flow along permanent route, in a constant direction. By means of novel methods of immobilization, observation and recording, some dynamic properties of cytoplasmic streaming have been described. It was found that the velocity profiles of coaxial layers of cytoplasm have a (parabolic) paraboidal shape and the mean output of cytoplasm flow in different examined zones of streaming is constant. As the consequence of randomly distributed elementary propulsion units within the cytoplasm, particles, which serve as markers of movement, exhibit movements of a saltatory nature; this form of movement is seen inParamecium streaming only in cases of error due to polarization of the saltating particles. Interaction of actin filaments and myosin is likely to occur under specific conditions in microcompartments of cytoplasm where local solations are generated eventually leading to contractions which might propagate on gelated neighbouring areas. Places of elementary contractions are scattered. Therefore the motile effect appears as streaming. Rotational cytoplasmic streaming inParamecium may serve as a convenient model for the study of the dynamics and function of cytoplasmic motility.     

Permeability of the Plasmalemma as Compared with that of the Tonoplast

In recent years there has been an increasing tendency to regard the tonoplast as the decisive diffusion barrier of the protoplast. The plasmalemma has been assumed to be more or less freely permeable, especially to ions (Brooks 4, Arisz 1, Epstein 8, Briggs and Robertson 3, Sutcliffe 12). This view is, however, based on observations which are far from unequivocal.
In the following we shall try to elucidate the question of the relative permeability and susceptibility of the two plasma membranes towards sodium hydroxide and sodium carbonate. The tests were made on internodal cells of Nitellopsis obtusa , staminal hairs of Tradescantia virginiana and T. zcbrina and epidermal cells of Allium cepa var. sanguinetim. These cells show protoplasmic streaming and either contain anthocyanins or were stained with neutral red.
In these experiments the plasmalemma, or some other layer outside the streaming part of the protoplasm, is assumed to be more or less impermeable towards sodium hydroxide as long as protoplasmic streaming is going on in the cells lying in the strongly alkaline solution. On the other hand, by the time the colour of the cell sap changes a considerable amount of NaOH must have passed through the whole protoplast, including both plasmalemma and tonoplast. The principal object of the experiments was, therefore, to compare (a) the time necessary to stop the protoplasmic streaming, irreversibly, with (b) the time required for the colour of the vacuole to change either to yellow (neutral red) or to blue (anthocyanin).     

Rhythmicity in the protoplasmic streaming of a slime mold,Physarum polycephalum. I. A statistical analysis of the electric potential rhythm

The electric potential difference (1 to 15 mv.) between two loci of the slime mold connected with a strand of protoplasm changes rhythmically with the same period (60 to 180 seconds) as that of the back and forth protoplasmic streaming along the strand. Generally some phase difference is observed between them. Periods of the electric potential rhythm show a Gaussian distribution. Amplitudes give a somewhat different distribution curve. Wave forms are not always simple harmonic ones, but are distorted more or less. However, auto-correlation analysis proves that there is a dominant rhythm of a nearly constant period which coincides with the mean period of the Gaussian distribution curve. Calculations made on an assumption that the electric potential rhythm is the result of many elementary rhythms (i.e., same periodicity, arbitrary phase angles) distributed throughout the plasmodium, give a satisfactory coincidence with the observed distribution for the amplitude. The predominance of a rhythm of a nearly constant periodicity suggests the existence of well organized interactions among components of a contractile protein network, the rhythmic deformation of which is supposed to be responsible for the protoplasmic streaming and for the electric potential rhythm.     

Morphogenesis and Disassembly of the Circular Plasmalemma Invagination System in Physarum polycephalum

During the morphogenesis of small plasmodia developing from endoplasmic drops, an extended plasmalemma invagination system is formed. This system is a characteristic constituent of the ectoplasm. The invaginations have different cytophysiological functions.
The transition from the initial very irregular plasmalemma indentations in protoplasmic drops to the highly organized circular invagination ring of protoplasmic strands, i.e., the differentiation as well as the disassembly of this circular invagination system in retracting endings of strands was investigated with the aid of the semithin- and ultrathin-sectioning technique.
Live observation of protoplasmic drops revealed that simultaneously with the onset of initially irregular oscillating contractions, small endoplasmic streamlets are generated. Subsequently, an improvement of the coordination of contraction activities leads to an oriented mass transport of protoplasm and thereby to locomotion. The growing endoplasmic channels continuously develop into the well-known structure of protoplasmic strands. Differentiation and disassembly of circular plasmalemma invaginations are based on processes of membrane invagination in combination with intracytosis and exocytosis.
The importance and correlations of the following phenomena for morphogenesis and differentiation are discussed: 1) the formation and distribution of the contractile apparatus, i.e., the system of cytoplasmic actomyosin fibrils, 2) plasmalemma invaginations, 3) the generation of oscillating contractions, and 4) the endoplasmic streaming.     

Fluid-dynamical study of protoplasmic streaming in a plant cell

A mathematical model of protoplasmic streaming in a plant cell such as Nitella and Chara is studied. General rheological equations for the non-Newtonian fluid is derived theoretically, and the boundary value problem for the model is solved. The pattern of motion of cytoplasm in a living cell is obtained, and the rheological property of protoplasm is evaluated in vivo.