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Results for “Cytoplasmic Streaming”

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At least 19 recordsLinked to original sources
PubMed1979

The estimation of velocity distribution profile of Paramecium cytoplasmic streaming.

Cytoplasmic streaming of Paramecium bursaria and Paramecium tetraurelia was investigated by cinematographic techniques. Analysis of the records reveals the paraboidal character of the velocity distribution profiles in all arbitrarily chosen zones along the whole route of moving cytoplasm in the cell. According to the date obtained from cytoplasmic streaming analysis and food vacuole path, the geometry of the "channel" was described in terms of ellipsoid axes. Total volume changes of cytoplasm flowing through a given cross section in a given time unit were computed and no significant differences were found. The participation of a pressure gradient in motive force generation in cytoplasmic streaming is discussed.

Animals↗
PubMed1976

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.

Chlorophyta↗
PubMed1979

Filaments associated with the endoplasmic reticulum in the streaming cytoplasm of Chara corallina.

Perfused Chara cells capable of resuming ATP-dependent cytoplasmic streaming in low free Ca++ solutions have been examined by electron microscopy for myosin-like filaments. Filaments 44 nm in diameter and up to 3 micron in length have been found associated with the endoplasmic reticulum that along with mitochondria, microbodies and dictyosomes from the endoplasm becomes immobilised around the sub-cortical actin bundles when ATP is depleted. Such endoplasmic filaments have not been detected in association with mitochondria or microbodies and they have not been found in the stationary cortex. These filaments are extracted from the perfused cell by ATP unless motility-inhibiting levels of cytochalasin B are present. The filaments are not detectable in cells inactivated in solutions containing high (10(-4) M) Ca++ concentrations even when the Ca++ level is subsequently lowered. Consistent with their being required for motility, cytoplasmic streaming cannot be effeiciently reactivated by ATP in such filament-depleted cells. The possibility is discussed that the filaments contain myosin and that the endoplasmic reticulum with which they are associated has a major role in generating and transmitting the motive force for streaming.

Adenosine Triphosphate↗
PubMed1979

Ultrastructure of the endoplasmic factor responsible for cytoplasmic streaming in Chara internodal cells.

Previous investigators have proposed that cytoplasmic streaming in Chara internodal cells results from the interaction between an endoplasmic factor and fibrils composed of microfilaments in the stationary cortex. Using the internal perfusion technique, we confirmed the observation that organelles which had been attached to the fibrils by decreasing the internal concentration of ATP moved along the fibrils after ATP was introduced. Thin-sectioned specimens revealed that endoplasmic organelles of various shapes were linked to microfilament bundles in the absence of ATP. Linkage was effected by regularly arranged electron-dense materials with a spacing of 100 -- 130 nm at definite regions on each organelle. The organelles in question were studied in negatively stained preparations of endoplasm. The organelles had some common features. (1) They were all membrane-limited.(2) Their sizes and configurations varied largely. (3) One or more protuberances were present on them. (4) The protuberances were usually rod- or horn-like. (5) Small globular bodies 20--30 nm in diameter were found in ordered array with the same spacing as those in thin sections at the surface of the protuberances. (6) Many fine filaments were always attached to the surface of the protuberances. These fine filaments differed from F-actin in diameter (less than 4 nm) and inability to react with heavy meromyosin from rabbit skeletal muscle. The role of such components of the organelles in cytoplasmic streaming is discussed. A paracrystalline array of microfilaments with a transverse periodicity of about 38 nm is presented, together with its optical diffraction pattern.

Adenosine Triphosphate↗
PubMedDate not supplied

Entamoeba motility: dynamics of cytoplasmic streaming, locomotion and translocation of surface-bound particles, and organization of the actin cytoskeleton in Entamoeba invadens.

The dynamics of cytoplasmic streaming, retrograde translocation of externally bound particles and locomotion by Entamoeba invadens were compared. Locomoting amoebae were monopodial, exhibited fountain flow cytoplasmic streaming and translocated externally bound erythrocytes to the rear of cells. The rates of rearward flow of peripheral cytoplasmic vacuoles and of the externally bound particles were equal to the rate of cell forward locomotion. Rhodamine-phalloidin staining revealed a distinct cortical polymerized actin cytoskelton. This was least evident about the periphery of the advancing pseudopod, increased in density toward the rear of the cell and was most concentrated in the uroid. A monoclonal anti-eucaryotic actin antibody, which recognized monomeric Entamoeba actin on immunoblots, stained trophozoites by indirect immunofluorescence throughout the cytoplasm, but not in the cortical regions stained by rhodamine-phalloidin. This and other evidence implied that the antibody recognized only unpolymerized actin in Entamoeba. We propose that locomotion, cytoplasmic streaming and translocation of externally bound particles are driven by a common actin-based mechanism in Entamoeba, possibly involving retrograde cortical actin flow and recycling.

Actins↗
PubMed1990

Movement of vesicles in cytoplasmic streaming in plasmodium.

The moving velocities of vesicles in the cytoplasmic streaming of a slime mold were measured, in which all of the vesicles passing through a designated window were counted. Vesicles in the streaming are distributed in their moving velocities and the distribution itself varies with time. The mean velocity of vesicles and its standard deviation were found to exhibit a linear relationship, suggesting a possibility that vesicles in the cytoplasm would also be involved in force generation.

Cytoplasmic Streaming↗
PubMed1976

The migrating thermodynamic quantum hypothesis for cytoplasmic streaming, sodium pumping and other cell biological phenomena, deduced from biofunctional considerations of the ultrastructure of brush border microvilli.

An attempt is made to reconcile experimental data dealing with, inter alia, cytoplasmic streaming in Characean algae, contraction in actomyosin systems. Na+- and -K+-simtulated ATPase activity and the ultrastructure of brush border microvilli. It is postulated that myosin molecules transfer energy from ATP to an actin-containing filament and that a high energy conformation is subsequently propagated along the filament. At regularly spaced intervals corresponding to the length of an actin-tropomyosin subunit, the propagation of high energy involves rejection of a pressure pulse in the direction of cytoplasmic streaming. Proteins in solution capable of storing the thermodynamic energy represented by the pressure pulse will either migrate in the opposite direction or conserve the quantized cytoplasmic flow generated by the actin-containing filaments. At sites where actin filaments are attached to the plasma membrane the high energy is propagated in another direction leading to expulsion of sodium ions and neutralization of the vectorial pressure pulse.

Actomyosin↗
PubMed1988

The mechanism of cytoplasmic streaming in characean algal cells: sliding of endoplasmic reticulum along actin filaments.

Electron microscopy of directly frozen giant cells of characean algae shows a continuous, tridimensional network of anastomosing tubes and cisternae of rough endoplasmic reticulum which pervade the streaming region of their cytoplasm. Portions of this endoplasmic reticulum contact the parallel bundles of actin filaments at the interface with the stationary cortical cytoplasm. Mitochondria, glycosomes, and other small cytoplasmic organelles enmeshed in the endoplasmic reticulum network display Brownian motion while streaming. The binding and sliding of endoplasmic reticulum membranes along actin cables can also be directly visualized after the cytoplasm of these cells is dissociated in a buffer containing ATP. The shear forces produced at the interface with the dissociated actin cables move large aggregates of endoplasmic reticulum and other organelles. The combination of fast-freezing electron microscopy and video microscopy of living cells and dissociated cytoplasm demonstrates that the cytoplasmic streaming depends on endoplasmic reticulum membranes sliding along the stationary actin cables. Thus, the continuous network of endoplasmic reticulum provides a means of exerting motive forces on cytoplasm deep inside the cell distant from the cortical actin cables where the motive force is generated.

Actins↗
PubMed1976

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.

Cytoplasm↗
PubMed1986

The role of microfilaments in cytoplasmic streaming in Drosophila follicles.

During the last phase of oogenesis in Drosophila, nurse cell cytoplasm can be seen to be streaming into the growing oocyte when visualized in time-lapse films. This process can be reversibly inhibited by cytochalasins. The distribution of F-actin filaments in the nurse cells has been studied by staining with rhodamine-conjugated phalloidin. At the beginning of cytoplasmic streaming (stage 10B) increasingly thick bundles of microfilaments formed, many of which spanned the nurse cell cytoplasm from the cell membrane to the nuclear membrane. The association of F-actin with the nuclear membrane persisted when nurse cell nuclei were isolated mechanically. The experimental evidence suggests that microfilament contraction in the nurse cells leads to cytoplasmic streaming by pressure flow.

Actin Cytoskeleton↗
PubMed1979

Effects of the actin-binding protein DNAase I on cytoplasmic streaming and ultrastructure of Amoeba proteus. An attempt to explain amoeboid movement.

Microinjection of DNAase I, which is known to form a specific complex with G-actin, induces characteristic changes in cytoplasmic streaming, locomotion and morphology of the contractile apparatus of A. proteus. Light microscopical studies show pronounced streaming originating from the uroid and/or the retracting pseudopods, which ceases 10--15 min after injection of DNAase I, at a time when ultrasctructural studies show that the actin filament system is very much reduced. These results suggest that a controlled reversible equilibrium between soluble and polymerized forms of actin is a necessary requirement for amoeboid movement. The topographic distribution of contractile filaments beneath the plasma membrane visualized by correlated light- and electron microscopy of DNAase I-injected cells establishes the importance of the membrane-bound filamentous layer for three major aspects of streaming: (1) Streaming originates by local contractions of a cell membrane-associated filament layer at the uroid and/or retracting pseudopods, creating a pressure flow. (2) This flow continues beneath the membrane, which is stabilized by filaments in the lateral regions between the posterior end, with a high hydrostatic pressure, and the anterior end, with a low hydrostatic pressure. (3) Pseudopods or extending areas are created by a local destabilization of the cell periphery caused by the separation of the filamentous layer from the plasma membrane.

Amoeba↗