scholarly journals Ca++ regulation in caffeine-derived microplasmodia of Physarum polycephalum.

1977 ◽  
Vol 72 (2) ◽  
pp. 502-505 ◽  
Author(s):  
L M Matthews
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Physarum Polycephalum ◽  
Storage System ◽  
Shuttle Streaming ◽  
Intracellular Storage

Caffeine-derived microplasmodia possess a Ca++-sequestering system which can initiate motility. The experiments presented here suggest that this system is membranous and nonmitochondrial in nature. Therefore, it is proposed that the shuttle streaming in the plasmodium is controlled by the localized release and uptake of free Ca++ from an intracellular storage system analogous to the sarcoplasmic reticulum.

Plasmalemma Invaginations as Characteristic Constituents of Plasmodia of Physarum Polycephalum

1974 ◽  
Vol 16 (1) ◽  
pp. 23-37
Author(s):  
K. E. WOHLFARTH-BOTTERMANN
Keyword(s):  
Physarum Polycephalum ◽  
Close Contact ◽  
Surrounding Medium ◽  
Defined Medium ◽  
Subsequent Paper ◽  
Outer Border ◽  
Shuttle Streaming ◽  
Food Absorption ◽  
Plasmalemma Invaginations

Plasmodia of Physarum polycephalum grown on agar or filter paper and fed with rolled oats as food or with a partially defined medium were morphologically analysed in the living state and after fixation. Observation of the living plasmodium growing on agar reveals plasmalemma indentations in the outer regions of protoplasmic strands, which were studied in more detail by phase-contrast microscopy of unstained 1-µm sections. Plasmodia fixed and embedded in situ, i.e. in close contact to their substrate, exhibit an extensive system of plasmalemma invaginations as characteristic constituents throughout all regions. In plasmodial strands measuring between 40 µm and 1.5 mm in diameter and involved in shuttle streaming, the plasmalemma invaginations are found within the outer ectoplasmic wall. Rounded-up parts of this branched extracellular labyrinth limit the endoplasmic core engaged in the mass transport of protoplasm by shuttle streaming. Despite this clearcut borderline, the central endoplasmic core and the ectoplasmic cortex are connected by occasional protoplasmic bridges. The extracellular phase within the ectoplasmic regions of the strands can be interpreted either as a result of plasmalemma invaginations from the outer border of the strand, or as a consequence of pseudopodial-like processes originating from the central core and extending into the surrounding medium. The invagination system provides an extensive enlargement of the surface area within the multinucleate protoplasmic mass, probably important for food absorption, excretion processes and motility phenomena. In thick protoplasmic strands with diameters between 0.2 and 1.5 mm, there is an intimate connexion between the actomyosin fibrils and the invagination system. The fibrils are attached to the plasmalemma invaginations and/or run parallel to the invaginated plasmalemma sheets. The close relations between the invagination system and actomyosin fibrils will be described in detail in a subsequent paper.

Calcium is released from the junctional sarcoplasmic reticulum during cardiac muscle contraction

1991 ◽  
Vol 260 (3) ◽  
pp. H989-H997 ◽  
Author(s):  
C. S. Moravec ◽  
M. Bond
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Muscle Contraction ◽  
Cardiac Muscle ◽  
Electron Probe Microanalysis ◽  
Electron Probe ◽  
Storage Site ◽  
Papillary Muscles ◽  
Cardiac Muscle Contraction ◽  
Intracellular Storage ◽  
Junctional Sarcoplasmic Reticulum

We have used electron-probe microanalysis (EPMA) to address the question of Ca2+ release by junctional sarcoplasmic reticulum (JSR) as well as Ca2+ regulation by mitochondria (MT) during cardiac muscle contraction. Hamster papillary muscles were rapidly frozen during relaxation or at the peak rate of tension rise (+dT/dt). Total Ca2+ content was measured by EPMA in the JSR, within a MT, over the A band, and in the whole cell, in nine cells per animal (five animals per group). JSR Ca2+ content was found to be significantly lower in muscles frozen at the peak of contraction [7.3 +/- 1.3 (mean +/- SE) mmol Ca2+/kg dry wt] than in those frozen during relaxation (12.5 +/- 1.9 mmol Ca2+/kg dry wt; P less than 0.01), suggesting that Ca2+ is released from this storage site during cardiac muscle contraction. In contrast, MT Ca2+ content did not change significantly during contraction (0.4 +/- 0.1 mmol/kg dry wt) compared with relaxation (0.1 +/- 0.2 mmol/kg dry wt). A third group of muscles was frozen during relaxation after pretreatment with 10(-7) M ryanodine. Ca2+ content of the JSR was significantly decreased (P less than 0.01) in this group of muscles, (6.4 +/- 1.8 mmol/kg dry wt) compared with those frozen during relaxation in the absence of the drug. This suggests that the intracellular storage site with a decreased Ca2+ content in muscles frozen at the peak of contraction is the ryanodine-releasable store. These results provide the first direct measurement of the Ca2+ content of both JSR and MT during a normal cardiac muscle contraction and demonstrate that Ca2+ is released from the JSR during muscle contraction.

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

1965 ◽  
Vol 25 (2) ◽  
pp. 361-374 ◽  
Author(s):  
Hiromichi Nakajima ◽  
Robert D. Allen
Keyword(s):  
Physarum Polycephalum ◽  
Cytoplasmic Streaming ◽  
Channel Wall ◽  
Polarized Light ◽  
Orthogonal Arrays ◽  
Slime Mold ◽  
Wall Material ◽  
Shuttle Streaming ◽  
Oriented Parallel ◽  
Birefringent Fibrils

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.

scholarly journals Periodic traction in migrating large amoeba of Physarum polycephalum

2015 ◽  
Vol 12 (106) ◽  
pp. 20150099 ◽  
Author(s):  
Jean-Paul Rieu ◽  
Hélène Delanoë-Ayari ◽  
Seiji Takagi ◽  
Yoshimi Tanaka ◽  
Toshiyuki Nakagaki
Keyword(s):  
Physarum Polycephalum ◽  
Traction Force ◽  
Cortical Layer ◽  
Force Distribution ◽  
Locomotory Activity ◽  
Multinucleated Cell ◽  
Force Microscopy ◽  
Giant Multinucleated Cell ◽  
Shuttle Streaming

The slime mould Physarum polycephalum is a giant multinucleated cell exhibiting well-known Ca 2+ -dependent actomyosin contractions of its vein network driving the so-called cytoplasmic shuttle streaming. Its actomyosin network forms both a filamentous cortical layer and large fibrils. In order to understand the role of each structure in the locomotory activity, we performed birefringence observations and traction force microscopy on excised fragments of Physarum . After several hours, these microplasmodia adopt three main morphologies: flat motile amoeba, chain types with round contractile heads connected by tubes and motile hybrid types. Each type exhibits oscillations with a period of about 1.5 min of cell area, traction forces and fibril activity (retardance) when fibrils are present. The amoeboid types show only peripheral forces while the chain types present a never-reported force pattern with contractile rings far from the cell boundary under the spherical heads. Forces are mostly transmitted where the actomyosin cortical layer anchors to the substratum, but fibrils maintain highly invaginated structures and contribute to forces by increasing the length of the anchorage line. Microplasmodia are motile only when there is an asymmetry in the shape and/or the force distribution.

Relation of cytoplasmic calcium to contractility in Physarum polycephalum

1982 ◽  
Vol 53 (1) ◽  
pp. 37-48 ◽  
Author(s):  
R. Kuroda ◽  
H. Kuroda
Keyword(s):  
Electron Microscopy ◽  
Physarum Polycephalum ◽  
Motive Force ◽  
Cytoplasmic Calcium ◽  
Shuttle Streaming ◽  
The Asymmetry ◽  
Plasmodium Of Physarum Polycephalum ◽  
Potassium Pyroantimonate ◽  
Cellular Organelles

In a dumbbell-shaped plasmodium of Physarum polycephalum showing active shuttle streaming Ca was precipitated with potassium pyroantimonate (K[Sb(OH)6]), and the distribution of Ca between the cytoplasm and cellular organelles, especially vacuoles, was examined by electron microscopy. The contracting half-mass, where many empty vacuoles were present, was rich in the small Ca precipitates located in the cytoplasm. The relaxing half-mass, where many Ca-containing vacuoles were present, was poor in the cytoplasmic Ca precipitates. One half-mass of a dumbbell-shaped plasmodium was treated with Ca ionophore, X-537A, and its effect on the motive force for endoplasmic streaming and the distribution of Ca was investigated. The motive force was increased by X-537A, but the period of shuttle streaming was not changed. X-537A also induced a significant increase in the number of the cytoplasmic Ca precipitates in the X-537A-treated contracting half-mass, so that the asymmetry of the distribution of cytoplasmic Ca precipitates was enhanced. A large portion of the vacuoles were empty in the contracting half-mass, and Ca-containing in the relaxing one as in the case of the untreated plasmodium.

Synchrony in the rhythm of the contraction-relaxation cycle in two plasmodial strands of Physarum polycephalum

1977 ◽  
Vol 26 (1) ◽  
pp. 151-160
Author(s):  
Y. Takeuchi ◽  
M. Yoneda
Keyword(s):  
Control System ◽  
Physarum Polycephalum ◽  
Isometric Tension ◽  
Entire Body ◽  
Periodic Activity ◽  
Relaxation Cycle ◽  
Shuttle Streaming

Rhythmicity of contraction of plasmodial strands of Physarum polycephalum was studied, by measuring the isometric tension exerted by isolated segments of the strands. When 2 strands were connected by way of a plasmodial mass, the contraction-relaxation cycle of the 2 strands synchronized. Such cycle activity of the strand was found to be well coordinated with shuttle streaming in the plasmodial mass which had been in connection with the strand. The presence of a control system which induces synchrony of periodic activity over the entire body of a plasmodium is discussed.

Progress and problems in understanding the involvement of calcium in heart function

1984 ◽  
Vol 62 (7) ◽  
pp. 867-873 ◽  
Author(s):  
N. S. Dhalla ◽  
P. K. Singal ◽  
V. Panagia ◽  
J. A. C. Harrow ◽  
M. B. Anand-Srivastava ◽  
...  
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Atpase Activity ◽  
Heart Function ◽  
Cardiac Contraction ◽  
Antiarrhythmic Agents ◽  
Functional Changes ◽  
Intracellular Ca ◽  
Cardiomyopathic Hamsters ◽  
Intracellular Storage

In this article we have briefly reviewed the role of Ca2+ in the excitation contraction coupling in the myocardium and have indicated that cardiac contraction and relaxation are initiated upon raising and lowering the intracellular concentration of free Ca2+, respectively. Different mechanisms for the entry of Ca2+ through sarcolemma as well as release of Ca2+ from sarcoplasmic reticulum and possibly mitochondria have been outlined for initiating cardiac contraction. Relaxation of the cardiac muscle appears to be intimately dependent upon efflux of Ca2+ through sarcolemma as well as sequestration of Ca2+ by the intracellular storage sites, particularly sarcoplasmic reticulum and possibly mitochondria. The actions of some pharmacological and pathophysiological interventions have been explained on the basis of changes in subcellular Ca2+ movements in myocardium. Quinidine, which produced an initial positive inotropic action on rat heart was also found to increase sarcolemmal Ca2+-ATPase activity without any changes in the Na+–K+ ATPase. Other antiarrhythmic agents, procainamide and lidocaine, also increased sarcolemmal Ca2+-ATPase activity without affecting the Na+–K+ ATPase. On the other hand, both Ca2+-ATPase and Na+–K+ ATPase activities were increased in heart sarcolemma obtained from cardiomyopathic hamsters. In this model the increased Ca2+-ATPase activity may promote the occurrence of intracellular Ca2+ overload in the cardiac cell whereas the increased Na+–K+ ATPase activity may increase Ca2+ efflux through Na+–Ca2+ exchange systems as an adaptive mechanism. It has been suggested that some caution should be exercised while interpreting the data from in vitro experiments in terms of functional changes in the myocardium. Furthermore, it has been proposed that the pathophysiology and pharmacology of Ca2+ movements at different membrane sites be understood fully in normal and diseased myocardium in order to improve the therapy of heart disease.

A mathematically modelled cytogel cortex exhibits periodic Ca++-modulated contraction cycles seen in Physarum shuttle streaming

Development ◽  
1984 ◽  
Vol 83 (Supplement) ◽  
pp. 261-287
Author(s):  
Garrett M. Odell
Keyword(s):  
Physarum Polycephalum ◽  
Mechanical Strain ◽  
Qualitative Behaviour ◽  
Collective Interaction ◽  
Vein Segment ◽  
Animated Films ◽  
Shuttle Streaming ◽  
Set Up ◽  
The Right ◽  
Tissue Deformations

If each of many cells of an embryo (or different zones in a single cell) possess identical active cytogel machinery, having the ‘right’ mechanochemical response properties, then the collective interaction among those identical participants leads automatically to the globally coherent tissue deformations seen in embryogenesis, and to shuttle streaming in the plasmodial slime mould Physarum polycephalum. Biologically plausible, and experimentally verifiable hypotheses are proposed concerning how the tension generated by a strand of cytogel is determined by the deformation it suffers and by the concentration of a contraction trigger chemical, Ca2+, whose kinetics involve coupling to mechanical strain. The consequences of these hypotheses, deduced by solving the appropriate differential equation systems numerically, and displayed in computer-animated films, closely imitate diverse tissue deformation events seen in developing embryos. The same hypotheses on cytogel behaviour are used to model a thick-walled Physarum vein segment, and two such segments are set up to be able to pump endoplasm back and forth between them. Under certain conditions, this model exhibits spontaneous rhythmic mechanochemical oscillations, many features of which correlate well with shuttle streaming in Physarum. Small gradual variations of parameters, presumably under genetic control, are shown to cause abrupt and biologically interesting bifurcations of the qualitative behaviour of the model.

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