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.     

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。     

Effect of Chilling Temperatures on the Protoplasmic Streaming of Plants from Different Climates

A microscope mount was designed so that specimen temperaturescould be monitored and controlled without impairing phase contrastoptics and used to measure rates of protoplasmic streaming between0 and 25 ?C in trichome cells of Lycopersicon esculentum, Lycopersiconhirsutum, Citrullus vulgaris, Tradescantia albiflora, Digitalispurpurea, and Veronica persica. Between 10 and 20 ?C the rates of streaming varied from 2–6µm s^–1 depending on the temperature, and differencesbetween the species were small. The temperature coefficientof streaming rates was found to increase as the temperaturewas lowered so that the plot of log rate against temperaturehad a steeper slope at the lower temperatures. The largest temperature cofficients were for the warmth-requiringL. esculentum (tomato) and C. vulgaris (water melon), and thesmallest for the temperate-zone plants V. persica (speedwell)and D. purpurea (foxglove). The changes in rate always occurredover a range of temperature; no ‘critical temperature’wasobserved below which streaming abruptly stopped and above whichit was active, although the amount of streaming as well as therate decreased as the lowest temperatures were approached. The temperatures experienced by the specimens during the experimentdid not affect the recovery of normal streaming rates betweenabout 10 and 20 ?C. In a population of a wild tomato, Lycopersicon hirsutum Humb.and Bonpl., collected from different altitudes in Peru and Ecuador,i.e. from locations of different environmental temperature,the rate of protoplasmic streaming at 5 ?C was greatest in thevarieties collected from the highest altitudes. The resultssuggest that streaming rates correlate with genetic adaptationto low temperature in the species examined.     

Intercellular Transport and Cytoplasmic Streaming in Chara hispida

The correlation between the velocities of cytoplasmic streamingand of translocation of ¹⁴C-photosynthate and ³²P-phosphateassociated radioactivity has been investigated in whole plantsof the green freshwater alga Chara hispida L. Tracer was suppliedto the plant's rhizoid system in a split-chamber. The velocityof cytoplasmic streaming of 52±3.3 µm s^–1compares with 57±10 µm s^–1 found for ¹⁴C-transportand 32±20 µm s^–1 found for ³²P-transport.There was no indication of intercellular translocation at avelocity faster than visible streaming. Cytochalasin B inhibitedthe translocation of ³²P and cytoplasmic streaming. CytochalasinB becomes fully effective in inhibiting streaming and transportafter an incubation time of at least 5 h. Key words: Chara hispida, Cytoplasmic streaming, Intercellular transport     

Rates of Axial Transport of 11C and 14C in Characean Cells: Faster than Visible Streaming?

Movements of ¹¹C and ¹⁴C in N. translucens occur at rates twoto five times greater than those of visually observed streaming.Like cytoplasmic streaming, longitudinal tracer movement isstopped reversibly by action potentials, irreversibly by N-ethylmaleimide(NEM) and is unaffected by colchicine (colch), suggesting thatboth processes share a common mechanism. Colchicine causes anincreased loading delay time. In both N. translucens and C. corallina the activity of ¹¹Cand ¹⁴C at the nodes shows a sharp discontinuity: it is lowon the feed side of the node and high at the node itself. Thissuggests that transport across plasmodesmata may be active. Key words: Axial-carbon transport, Cytoplasmic streaming, Carbon     

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.     

Induction of Cytoplasmic Streaming and Movement of Chloroplast Induced by L-Histidine and its Derivatives in Leaves of Egeria densa

Rotational cytoplasmic streaming in leaves of Egeria densa wasinduced by light as well as by L-histidine (L-His). During bothtreatement with light and with L-His chloroplasts on the periclinalface were dislodged and moved to the anticlinal face where rotationalcytoplasmic streaming occurred. The effective concentrationof L-His was about 0.01 mM and the effect was almost saturatedat 0.1 mM. A derivative of L-His, 3-methyl-L-histidine, wasslightly less effective than L-His. By contrast, 1-methyl-L-histidinewas almost ineffective for induction of streaming, not onlyin Egeria but also in Vallisneria. Our resutlts are in markedcontrast to Fitting's result (1936) that 1-M-L-His is more effectivethan L-His. In Egeria, 1-methyl-L-His counteracted the stimulativeeffect of L-His. 1-Methyl-L-His penetrated into leaf cells ofEgeria to the same extent as 3-methyl-L-His and to a greaterextent than L-His. This observation excludes the possibilitythat the impermeability of leaves to 1-M-L-His might be responsiblefor its ineffectiveness. 1-M-L-His did not interfere with photodinesis.Differences in the mechanism of induction of rotational streamingby L-His and by light are discussed. ⁴ Present address: Fukui Institute of Technology, Gakuen, Fukui,910 Japan (Received July 16, 1990; Accepted December 20, 1990)     

Activation of Cytoplasmic Streaming as an Adaptive Mechanism of Cultured Muskmelon Cells under Hypoxia Stress

Cytoplasmic granules were activated and moved along the cytoplasmicstrands as the cultured muskmelon (Cucumis melo L.) cells weretransferred from the k-8 agar medium to liquid medium. CytochalasinB reversibly inhibited the streaming, suggesting that the motiveforce for streaming was generated by microfilament. Besides,KCN and 2,4-dinitrophenol lowered the streaming velocity, showingthat the streaming required metabolic energy, ATP. Fluoresceindiacetate (FDA) staining was used to estimate cell viability.Variety reticulatus (CR), which had been regarded as floodinguntolerant (Crawford 1982, Liu and Chen 1987), had more viablecells than the flooding tolerant variety saccharinus (CS) whentheir calluses were transferred to liquid media. Meanwhile,variety CR had more streaming cells in the liquid medium, andwas maintained steadily between 6th and 9th day after transfer.It is considered that cytoplasmic streaming occurring in theCR cells served as an adaptive mechanism under flooding stress. (Received April 11, 1988; Accepted October 20, 1988)     

Cytochalasin Rearranges Cortical Actin of the Alga Nitella into Short, Stable Rods

The cortical cytoplasm of the alga Nitella contains reticulateactin that does not survive perfusion fixation with glutaraldehydeunless prestabilized with the cross-linker 3-maleimidobenzoyl-N-hydroxysuccinimidester (MBS). Cytochalasin D remodels thiscortical actin into short rods which are more stable, survivingaldehyde fixation without MBS pre-treatment. The overall alignmentof these actin rods correlates with that of cortical microtubules(transverse in young cells, random in old cells) but probablydoes not involve one-to-one correspondence. The time course,dose dependence and reversibility of these structural changesbroadly resemble those for streaming inhibition by cytochalasinbut the cortical actin responds to concentrations that do notslow streaming. Because the structural changes concern the corticaland not the subcortical actin, they seem unlikely to directlyinhibit streaming. Formation of cortical rods is not a responseto streaming inhibition per se since it does not occur whentwo other inhibitors of streaming (2,4-dinitrophenol (DNP) andNethyl maleimide (NEM)) are used. NEM, however, resembles MBSin stabilizing the reticulate form of cortical actin even thoughit cannot cross link. ¹Address from July 1995; Department of Biology, Faculty of Science,Osaka University, Machikaneyama 1-1, Tayonaka, Osaka, 560 Japan.     

Broad-range effects of ionophore X-537A on pollen tubes of Lilium longiflorum

The effects of the broad-range cationophore X-537A on pollen tubes of Lilium longiflorum were investigated, using both light and electron microscopy. Pollen tube growth is completely inhibited within 30 min after the application of 5·10^-5 M ionophore X-537A; cytoplasmic streaming is stopped only after 60 min of ionophore treatment. Ultrastructurally, X-537A effects are a vacuolation of Golgi cisternae and a general vacuolation. The wall is thickened at the very tip. Coated vesicles and coated regions are enriched close to and at the plasma membrane. The results indicate that pollen tube tip growth needs a specific ion distribution.Abbreviations CTC chlorotetracycline - DMSO dimethylsulfoxide     

Coupling of phospholipase C and PI3K/PTEN signaling pathways in <Emphasis Type="Italic">Physarum polycephalum</Emphasis>: The action of U73122 on motile and autooscillatory activity of plasmodium

The possibility of tight coupling of phospholipase C with the signal pathway PI3K/ PTEN, a ubiquitous mechanism for the control of chemotaxis and cell shape in free-living amoebae and mammalian tissue cells, has been investigated in Physarum polycephalum plasmodium, a multinuclear amoeboid cell with the autooscillatory mode of motility. It was found that on the maintenance of contractile autooscillations and protoplasmic shuttle streaming, U73122, an inhibitor of the signal transduction to phospholipase C, induces degradation of the plasmodium frontal zone, decreases efficiency of locomotion and suppresses the chemotaxis toward glucose as well as the response of oscillator to this attractant. The identity of the effects of U73122 with those shown for wortmannin and LY294002, widely used PI3K inhibitors (Matveeva et al. 2008. Biophysics. 53, 533–538), suggests a tight coupling of the signal pathways of phospholipase C and PI3K/PTEN. U73122 increases the period of contractile oscillations and abolishes its cyclic changes attributed for the plasmodium migration. The results indicate that motile behavior of the plasmodium is under the receptor-mediated control.     

Reactivation of Cytoplasmic Streaming in a Tonoplast-Permeabilized Cell Model of Acetabularia

To find whether cytoplasmic streaming in Acetabularia is controlledby Ca²⁺, a tonoplast-permeabilized cell model was prepared usinga vacuolar perfusion technique. The cytoplasmic streaming remainedalmost normal after perfusion with EGTA medium (10 mM EGTA,40 mM PIPES, 5mM MgCl₂ and 800 mM sorbitol, pH 6.9), but stoppedwithin 10 min when saponin medium (EGTA medium plus 50 µg/mlsaponin, 50 µg/ml hexokinase and 5 mM glucose) was perfused.This model system was reactivated with a solution containing0.5 mM ATP and different concentrations of Ca²⁺ (reactivationmedium). With the reactivation medium at pCa 6–5, theresumed streaming lasted for about 10 min before the cytoplasmaggregated. At pCa 4–3, the streaming was observed onlyfor a few minutes because the cytoplasm aggregated quickly.At pCa 7, no reactivated movement was observed. Reactivationwas not induced in an ATP- or Mg²⁺-deficient medium even inthe presence of an adequate concentration of Ca²⁺, and was inhibitedby 50 µg/ml cytochalasin B or 1 mM N-ethylmaleimide. We concluded from these observations that the cytoplasmic streamingin Acetabularia is very likely to be driven by the actomyosinsystem in the presence of Mg-ATP and Ca²⁺ at pCa 6–5. (Received October 31, 1984; Accepted April 1, 1985)     

THE CHANGING PATTERN OF BIREFRINGENCE IN PLASMODIA OF THE SLIME MOLD, PHYSARUM POLYCEPHALUM

Plasmodia of the acellular slime mold, Physarum polycephalum, reveal a complex and changing pattern of birefringence when examined with a sensitive polarizing microscope. Positively birefringent fibrils are found throughout the ectoplasmic region of the plasmodium. In the larger strands they may be oriented parallel to the strand axis, or arranged circularly or spirally along the periphery of endoplasmic channels. Some fibrils exist for only a few minutes, others for a longer period. Some, particularly the circular fibrils, undergo changes in birefringence as they undergo cyclic deformations. In the ramifying strand region and the advancing margin there is a tendency for fibrils of various sizes to become organized into mutually orthogonal arrays. In some plasmodia the channel wall material immediately adjacent to the endoplasm has been found to be birefringent. The sign of endoplasmic birefringence is negative, and its magnitude is apparently constant over the streaming cycle. The pattern of plasmodial birefringence and its changes during the shuttle streaming cycle of Physarum are considered in the light of several models designed to explain either cytoplasmic streaming alone or the entire gamut of plasmodial motions. The results of this and other recent physical studies suggest that both streaming and the various other motions of the plasmodium may very likely be explained in terms of coordinated contractions taking place in the fibrils which are rendered visible in polarized light.     

Cytoplasmic Hydration Triggers a Transient Increase in Cytoplasmic Ca2+ Concentration in Nitella flexilis

Cells of Nitella flexilis were made inexcitable by treatmentwith 10 mM KCl for more than 24 h. A Ca²⁺-sensitive photoproteinaequorin was injected into the cytoplasm of such cells. Forvacuolar per fusion, the central part of an aequorin-loadedcell was immersed in silicone oil, and both cell ends bathedin the perfusion medium were cut off. A large light emissionfrom aequorin was observed when the vacuole was perfused witha hypotonic medium whose osmotic pressure was adjusted to halfof the osmotic pressure of the cell sap. This shows that hydrationof the cytoplasm triggers release of Ca²⁺ from internal stores,since influx of Ca²⁺ from silicone oil is excluded. Hydration of cells was induced in another way. Cells were firstdehydrated by transferring them from 10 mM KCl solution to thatwith 250 mM sorbitol added. This procedure did not affect thecytoplasmic streaming. When cells were rehydrated by transferringthem to 10 mM KCl solution, cytoplasmic streaming was eitherstopped or slowed down in a few seconds. A quick light emissionfrom aequorin was observed in the rehydration, evidence thatcytoplasmic streaming was inhibited by an increase in the cytoplasmicCa²⁺ concentration. Both streaming cessation and aequorin lightemission were observed even in KCl-treated cells which werefurther treated with 5 mM EGTA. Thus, the increase in Ca²⁺ isconcluded to be caused by the release of Ca²⁺ from internalstores. These results support our previous hypothesis [Tazawa et al.(1994) Plant Cell Physiol. 35:63] that, in Nitella flexilis,the increase in the concentration of Ca²⁺ in the cytoplasm whichoccurs on the endoosmotic side of the cell during transcellularosmosis is caused by hydration of the cytoplasm. (Received June 6, 1994; Accepted December 26, 1994)     

Dynamic complexity inPhysarum polycephalum shuttle streaming

Summary The nature of the oscillator controlling shuttle streaming inPhysarum polycephalum is not well understood. To examine the possibility of complex behavior in shuttle streaming, the time between reversal of streaming direction was measured over several hours in an intact plasmodium to produce a time series. Time series data were then used to analyze shuttle streaming dynamics. Complexity in shuttle streaming is revealed by an inverse frequency (1/f) power spectrum where the amplitude of reversals is plotted against their frequency. The complex dynamics of shuttle streaming is also shown by a trajectory in phase space typical of a strange attractor. Finally, shuttle streaming time series data have a dominant Lyapunov exponent of approximately zero. Dynamic systems with a Lyapunov exponent of zero exist in a state at the edge of chaos. Systems at the edge exhibit self-organized criticality, which produces complex behavior in many physical and biological systems. We propose that complex dynamics inPhysarum shuttle streaming is an example of self-organized criticality in the cytoplasm. The complex behavior ofPhysarum is an emergent phenomenon that probably results from the interaction of actin filaments, myosin, ATP, and other components involved in cell motility.     

Effects of colchicine on the mitosis of Physarum polycephalum

Colchicine treatment delayed mitosis in the plasmodium of Physarumpolycephalum. This effect was observed when colchicine-pulsetreatments were performed at the late G2 phase. ³H-colchicine-bindingactivity was mainly localized in the nuclei and increased inthe late G2 phase. ¹ Present address: Department of Biochemistry, The Public HealthResearch Institute of The City of New York, Inc., New York,U.S.A. (Received September 22, 1977; )     

Intercellular Transport in Plants: II. CYCLOSIS AND THE RATE OF INTERCELLULAR TRANSPORT OF CHLORIDE IN CHARA

The effect of streaming speed on intercellular transport ofchloride has been studied using pairs of internodal cells ofChara. The rate of transport was measured by that fraction ofthe chloride that entered one internode which was transportedout of it into the cells of the node and the next internode.The speed of cytoplasmic streaming was altered by treating thefirst cell with cytochalasin B. The relative rate of intercellular transport depended markedlyon the streaming speed at all speeds up to those found in untreatedcells. The chloride influx into the treated cell did not dependon the streaming speed. It is concluded that the rate of intercellular transport oflow molecular weight solutes in Chara will be normally limitedby the rate at which cytoplasmic streaming brings solute tothe plasmodesmata, rather than by the diffusion permeabilityof the plasmodesmata. This conclusion may well apply to othercharophyte plants, and could in principle apply to higher plants.     

Calcium wave for cytoplasmic streaming of Physarum polycephalum

The plasmodium Physarum polycepharum exhibits periodic cycles of cytoplasmic streaming in association with those of contraction and relaxation movement. In the present study, we injected Calcium Green dextran as a fluorescent Ca²⁺ indicator into the thin‐spread living plasmodium. We found changes in the [Ca²⁺]i (intracellular concentration of Ca²⁺), which propagated in a wave‐like form in its cytoplasm. The Ca²⁺ waves were also detected when we used Fura dextran which detected [Ca²⁺]i by the ratio of two wavelengths. We prepared the plasmodial fragment from the thin‐spread and found that the cycles of the contraction–relaxation movement was so synchronized that the measurement of its area provided an indication of the movement. We observed that [Ca²⁺]i also synchronized in the entire fragment and that the relaxation ensued upon the reduction in [Ca²⁺]i. We suggest that the Ca²⁺ wave generated periodically is one of the major factors playing a crucial role in the relaxation of P. polycepharum.     

The Uptake and Transport of 14C in Cells of Conocephalum conicum L. in Light

Dissolved inorganic ¹⁴carbon, fed to a small portion of thetissue of Conocephalun conicum, travelled along the tissuesfrom cell to cell at rates of about 2.0 to 1.7 µm 5^–1,which is of the same order of magnitude as streaming rates inthese cells. Trans-cellular transport can take place againsta pressure gradient, but pressure gradients of 200 kPa or morein either direction reduced the trans-cellular transport significantlywithout reducing streaming rate and are, therefore, thoughtto have induced ‘valving’ effects at the plasmodesmata.Ammonium ion reduced or inhibited transport without reducingstreaming rates and is, therefore, thought to have inhibitedan active component in the plasmodesmata. Thus the results obtainedfrom tandem cells of Nitella can be transferred to tissues. Key words: Conocephalum, transport, plasmodesmata     

约氏疟原虫与伯氏疟原虫诱导感染小鼠产生保护性抗体的特点研究

比较约氏疟原虫(Plasmodium yoelii)与伯氏疟原虫(Plasmodium berghei)再次感染模型特异性抗体产生的差异,追溯相应虫体抗原的表达特点.建立约氏疟原虫与伯氏疟原虫再次感染鼠疟模型,ELISA检测特异性抗体水平;Western Blot检测血清中优势抗体反应特点;检测两种虫株的MSP-1重组...