Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Cytoplasmic Streaming”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 307 records · Page 17Linked to original sources
PubMed1966

Energy balancing in Nitella cells treated with dinitrophenol.

The toxic action of 2,4-dinitrophenol on the large cells of the alga, Nitella clavata, was evaluated, with the rate of protoplasmic streaming and the survival time at three light intensities used as criteria. At a sufficiently high intensity the cells survived several weeks, an indication that the energy-uncoupling action of dinitrophenol could be counterbalanced to some extent by an increased energy input. In the treated cells chloroplasts moved from the outer gel-type cytoplasm into the inner, streaming cytoplasm.

Chloroplasts↗
PubMed2005

Actin polymerization promotes the reversal of streaming in the apex of pollen tubes.

Actin polymerization is important in the control of pollen tube growth. Thus, treatment of pollen tubes with low concentrations of latrunculin B (Lat-B), which inhibits actin polymerization, permits streaming but reversibly blocks oscillatory growth. In the current study, we employ Jasplakinolide (Jas), a sponge cyclodepsipeptide that stabilizes actin microfilaments and promotes polymerization. Uniquely, Jas (2 microM) blocks streaming in the shank of the tube, but induces the formation of a toroidal-shaped domain in the swollen apex, of which longitudinal optical sections exhibit circles of motion. The polarity of this rotary motion is identical to that of reverse fountain motility in control pollen tubes, with the forward direction occurring at the edge of the cell and the rearward direction in the cell interior. Support for the idea that actin polymerization in the apical domain contributes to the formation of this rotary motility activity derives from the appearance therein of aggregates and flared cables of F-actin, using immunofluorescence, and by the reduction in G-actin as indicated with fluorescent DNAse. In addition, Jas reduces the tip-focused Ca2+ gradient. However, the alkaline band appears in the swollen apex and is spatially localized with the reverse fountain streaming activity. Taken together, our results support the idea that actin polymerization promotes reversal of streaming in the apex of the lily pollen tube.

Actin Cytoskeleton↗
PubMed1994

Simulation of aggregation in Dictyostelium using the Cell Programming Language.

In developmental biology, modeling and simulation play an important role in understanding cellular interactions. We suggest a simple language, the Cell Programming Language (CPL), to write computer programs to describe this behavior. Using these programs, it is possible to simulate and visualize intercellular behavior. We employ CPL to model aggregation in Dictyostelium in response to a chemotactic agent. CPL programs are utilized to model a variety of aggregation behavior including streaming, spiral formation and the effect of amoeba density on aggregation patterns. We believe CPL is a useful tool for developing, understanding and checking biological models that utilize cellular interactions.

Animals↗
PubMed1978

Convective control of long-range coherence in plant growth regulation.

It is hypothesized that morphogenetic control in plants depends on convective transport of biochemically important substances, where streaming velocity and cell shapes jointly determine spatial and temporal coherence, and where the streaming velocity in turn is affected by the gravitational field. The relative magnitudes of diffusive and convective effects are considered, and it is shown that in some plant cells for which cell sizes and streaming velocities have been measured convection could be the dominant transport mode. The consequences of this hypothesis in the presence and absence of a gravitational field are considered and permit its experimental verification or rejection.

Biological Transport↗
PubMed1999

Streaming potential of human lumbar anulus fibrosus is anisotropic and affected by disc degeneration.

The streaming potential responses of non-degenerate and degenerate human anulus fibrosus were measured in a one-dimensional permeation configuration under static and dynamic loading conditions. The goal of this study was to investigate the influence of the changes in tissue structure and composition on the electrokinetic behavior of intervertebral disc tissues. It was found that the static streaming potential of the anulus fibrosus depended on the degenerative grade of the discs (p = 0.0001) and on the specimen orientation in which the fluid flows (p = 0.0001). For a statically applied pressure of 0.07 MPa, the ratio of streaming potential to applied pressure ranged from 5.3 to 6.9 mV/MPa and was largest for Grade I tissue with axial orientation and lowest for Grade III tissue with circumferential orientation. The dynamic streaming potential responses of anulus fibrosus were sensitive to the degeneration of the disc: the total harmonic distortion factor increased by 108%, from 3.92 +/- 0.66% (mean +/- SD) for Grade I specimens to 8.15 +/- 3.05% for Grades II and III specimens. The alteration of streaming potential reflects the changes in tissue composition and structure with degeneration. To our knowledge, this is the first reported data for the streaming potential of human intervertebral disc tissues. Knowledge of the streaming potential response of the intervertebral disc provides an understanding of potentially important signal transduction mechanisms in the disc and of the etiology of intervertebral disc degeneration.

Adolescent↗
PubMed1978

Light and electron microscopic observations of feeding behavior, nutrition, and reproduction in laboratory cultures of Thalassicolla nucleata.

T. nucleata is a skeletonless, single-celled radiolarian commonly found in ocean surface water. Specimens were cultured in the laboratory in a seawater--antibiotic medium. Feeding experiments show that T. nucleata is omnivorous with preference for crustacea, colorless flagellates, and occasional diatoms. Pigmented algae bearing organic thecae are occasionally consumed, but Dunaliella sp. is rejected. Rhizopodial activity during algal predation is compared to activity during crustacean predation, and evidence for differentiation of function among rhizopodia is presented. Electron microscopic observations and evidence from cytochalasin B treatment support the hypothesis that microfilaments mediate organized rhizopodial streaming. Reproduction is by isospores which resemble those in other spumellarian Radiolaria. Survival time in laboratory culture indicates that T. nucleata has a life span of at least 3 weeks. These findings are discussed in relation to the unique requirements imposed by a pelagic habitat on survival of a single-celled floating organism.

Animals↗
PubMed1992

Chondrocytes in agarose culture synthesize a mechanically functional extracellular matrix.

The ability of chondrocytes from calf articular cartilage to synthesize and assemble a mechanically functional cartilage-like extracellular matrix was quantified in high cell density (approximately 10(7) cells/ml) agarose gel culture. The time evolution of chondrocyte proliferation, proteoglycan synthesis and loss to the media, and total deposition of glycosaminoglycan (GAG)-containing matrix within agarose gels was characterized during 10 weeks in culture. To assess whether the matrix deposited within the agarose gel was mechanically and electromechanically functional, we measured in parallel cultures the time evolution of dynamic mechanical stiffness and oscillatory streaming potential in uniaxial confined compression, and determined the intrinsic equilibrium modulus, hydraulic permeability, and electrokinetic coupling coefficient of the developing cultures. Biosynthetic rates were initially high, but by 1 month had fallen to a level similar to that found in the parent calf articular cartilage from which the cells were extracted. The majority of the newly synthesized proteoglycans remained in the gel. Histological sections showed matrix rich in proteoglycans and collagen fibrils developing around individual cells. The equilibrium modulus, dynamic stiffness, and oscillatory streaming potential rose to many times (>5x) their initial values at the start of the culture; the hydraulic permeability decreased to a fraction (approximately 1/10) that of the cell-laden porous agarose at the beginning of the culture. By day 35 of culture, DNA concentration (cell density), GAG concentration, stiffness, and streaming potential were all approximately 25% that of calf articular cartilage. The frequency dependence of the dynamic stiffness and potential was similar to that of calf articular cartilage. Together, these results suggested the formation of a mechanically functional matrix.

Animals↗
PubMed1982

The cytokineplast: purified, stable, and functional motile machinery from human blood polymorphonuclear leukocytes.

We examined the formation of motile, chemotactically active, anucleate fragments from human blood polymorphonuclear leukocytes (PMN, granulocytes), induced by the brief application of heat. These granule-poor fragments are former protopods (leading fronts, lamellipodia) that become uncoupled from the main body of the cell and leave it, at first with a connecting filament that breaks and seals itself. The usual random orientation of such filaments can be controlled by preorientation of cells in a gradient of the chemotactic peptide, N-formylmethionylleucylphenylalanine (F-Met-Leu-Phe) (2x10(-9) M- 1x10(-8)). Cytochalsin B, 2.5-5 mug/ml, prevents fragment formation; colchicine, 10(-5) M, does not. In scanning electron micrographs, fragments are ruffled and the cell body rounded up and rather smooth. In transmission electron micrographs, fragments contain microfilaments but lack centrioles and microtubules. Like intact cells, both bound and free fragments can respond chemotactically to an erythrocyte destroyed by laser microirradiation (necrotaxis); the free, anucleate fragments may do so repeatedly, even after having been held overnight at ambient temperatures. We propse the name cytokineplast for the result of this self-purification of motile apparatus. The exodus of the motile machinery from the granulocyte requires anchoring of the bulk of the cell to glass and uncoupling, which may involve heat-induced dysfunction of the centrosome. In ultrastructural studies of the centrosomal region after heat, centriolar structure remains intact, but pericentriolar osmiophilic material appears condensed, and microtubules are sparse. These changes are found in all three blood cell types examined: PMN, eosinophil, and monocyte. Of these, the first two make fragments under our conditions; the more sluggish monocyte does not. Uncoupling is further linked to centrosomal dysfunction by the observation that colchicines-treated granulocytes (10(-5)M, to destroy the centrosome's efferent arm) make fragments after less heat than controls. If motive force and orientation are specified mainly from the organelle-excluding leading front, then endoplasmic streaming in PMN is a catch-up phenomenon, and microtubules do not provide the vector of locomotion but rather stabilize and orient the "baggage" (nucleus, granuloplasm)-i.e., they prevent fishtailing. Moreover, constraints emanating from the centrosome may now be extended to include, maintenance of the motile machinery as an integral part of the cell.

Cell Movement↗
PubMedDate not supplied

Does streaming affect the cerebral distribution of infraophthalmic intracarotid chemotherapy?

BACKGROUND AND PURPOSE: The development of new non-ocular-toxic drugs has enabled infraophthalmic chemotherapeutic infusion. We assessed whether streaming occurs with infraophthalmic, high cervical internal carotid artery (ICA) delivery of chemotherapeutic agents by means of conventional angiographic catheters. METHODS: Six patients with high-grade gliomas treated with monthly carotid intraarterial chemotherapy were studied. Chemotherapy delivery and distribution was modeled by technetium 99m hexylmethyl-propyleneamine oxine (HMPAO), a first-pass agent. Each patient received 0.5 mCi (18.5 MBq) of (99m)Tc-HMPAO in 50-mL of saline intraarterially in the ICA at the C1-C2 level. Injections were given twice, at two different injection rates: 0.08 mL/s at one therapeutic session and 6 mL/s a month later. The slow injection rate modeled the slowest rate used in the delivery of chemotherapy into the ICA. The higher rate was selected to avoid any possibility of uneven mixing, by replacing intracarotid blood completely and by using a turbulent injection rate that destroys laminar flow and intraarterial streaming. Single photon emission CT (SPECT) was performed 2 hours after injection. For each patient, the corresponding SPECT sections at the two injection rates were compared. RESULTS: No differences were noted in (99m)Tc-HMPAO distribution between the two injection rates in any of the patients. However, some of the rapid injection rate SPECT scans showed extension of the (99m)Tc-HMPAO uptake into adjacent watershed territories. CONCLUSION: There was no evidence, in humans, of substantial streaming during slow infraophthalmic intracarotid injections. Slow rates of infusion are as good as high rates for infraophthalmic intracarotid drug delivery. This is of special importance for drugs that are not tolerated at high injection rates. Moreover, infraophthalmic intracarotid chemotherapeutic infusion does not require special injectors or catheters.

Adult↗
PubMed1976

A study of protoplasmic streaming in Nitella by laser Doppler spectroscopy.

Laser light scattered from particles in the streaming protoplasm of a living cell is shifted in frequency by the Doppler effect. The spectrum of the scattered light can be measured and interpreted to infer details of the velocity distribution in the protoplasm. We have developed this approach to study the protoplasmic streaming in the fresh-water alga Nitella. Our results indicate a characteristic flow pattern to which diffusion makes a negligible contribution. No difference in the velocity of particles of different size is indicated. The streaming velocity linearly with temperature with a supraoptimal temperature of 34 degrees C, and the velocity distribution becomes narrower at high temperatures. The protoplasmic streaming can be inhibited by laser light, and this effect has been used to study the photoresponse of the algae. Using beam diameters of about 50 mum, we have shown that the inhibition is very local, becoming minimal at a displacement of about 200 mum in the upstream direction and 400 mum in the downstream direction. Prolonged exposure produces a bleached area free of chloroplasts, which is three orders of magnitude less sensitive to photoinhibition.

Chlorophyta↗
PubMed1989

Potential sites for the perception of gravity in the acellular slime mold Physarum polycephalum.

Recently a gravisensitivity of the acellular slime mold Physarum polycephalum, which possesses no specialized gravireceptor, could be established by conducting experiments under simulated and under real near weightlessness. In these experiments macroplasmodia showed a modulation of their contraction rhythm followed by regulation phenomena. Until now the perception mechanism for the gravistimulus is unknown, but several findings indicate the involvement of mitochondria: A) During the impediment of respiration the 0g-reaction is inhibited and the regulation is reduced. B) The response to a light stimulus and the following regulation phenomena strongly resemble the behavior during exposure to 0g, the only difference is that the two reactions are directed into opposite directions. In the blue-light reaction a flavin of the mitochondrial matrix seems to be involved in the light perception. C) The contraction rhythm as well as its modulations are coupled to rhythmic changes in the levels of ATP and calcium ions, involving the mitochondria as sites of energy production and of Ca(++)-storage. So the mitochondria could be the site of the regulation and they possibly are the receptor sites for the light and gravity stimuli. Also the observation of a morphologic polarity of the slime mold's plasmodial strands has to be considered: Cross-sections reveal that the ectoplasmic wall surrounding the streaming endoplasm is much thinner on the physically lower side than on the upper side of the strand--this applies to strands lying on or hanging on a horizontal surface. So, in addition to the mitochondria, also the morphologic polarity may be involved in the perception mechanism of the observed gravisensitivity and of the recently established geotaxis. The potential role of the nuclei and of the contractile elements in the perception of gravity is also discussed.

Adenosine Triphosphate↗
PubMed2002

Mesenchymally-derived insulin-like growth factor 1 provides a paracrine stimulus for trophoblast migration.

BACKGROUND: Trophoblast migration into maternal decidua is essential for normal pregnancy. It occurs in a defined time window, is spatially highly restricted, and is aberrant in some pathological pregnancies, but the control mechanisms are as yet ill-defined. At the periphery of the placenta, chorionic villi make contact with decidua to form specialised anchoring sites that feed interstitially migrating cytotrophoblast into the placental bed. RESULTS: Explants of first trimester mesenchymal villi on collagen type I developed cytotrophoblast outgrowths from the villous tips. However, in medium changed daily, cells did not progress to a migratory phenotype, remaining instead as a contiguous multi-layered sheet. This suggested the need for another migration stimulus. To test the possibility that this might arise from mesenchymal cells, serum-free conditioned medium from first trimester placental fibroblasts was added to explant cultures. Cytotrophoblasts were stimulated to migrate in streams across the gel. Affinity depletion of Insulin-like growth factor from fibroblast medium reduced streaming activity, while the addition of exogenous IGF-I (10 ng/ml) to serum-free medium produced a streaming phenotype. IGF receptor type 1 (IGFR1) was present on cells in the columns, and streaming could be inhibited by antibody to this receptor. IGF-II and activin, known stimulators of cytotrophoblast migration, were also active in this model. CONCLUSIONS: These data suggest a paracrine interaction between villous mesenchyme and the cytotrophoblast in anchoring sites that stimulates trophoblast infiltration of decidua. Such a signal would be self-limiting since it diminishes with distance from the placenta. This is a novel mechanism in placental development.

Cell Movement↗
PubMed1989

Gravity-dependent phenomena at the scale of the single cell.

Progress in gravitational cell biology research will depend on the continuing evaluation of a wide variety of physical phenomena affected by gravity and their roles in extracellular, intercellular, and intracellular processes. This paper examines those responses of organisms to gravity which depend on functions at the single cell level. Single cell functions are affected by perturbations in their internal and external environment by a variety of factors, one of which is the effect of gravity. Physical phenomena that could influence cell function include sedimentation, buoyancy-driven convection, streaming potential, hydrostatic pressure, and interactions among physical transport processes. Thermal motion and fluid viscosity play a significant role in all transport processes at the cellular level. The sedimentation of intracellular organelles tends to be counteracted by the cytoskeleton. Intracellular convective transport may be possible in large cells. In a microgravity environment extracellular solutes must be transported by diffusion or active circulatory processes in the absence of density gradient-driven convection, and flocculation and coalescence are reduced by the lack of motion of aggregates.

Animals↗
PubMed1986

Towards a new classification of intracellular particle movements based on quantitative analyses.

A survey study of organelle movements in a variety of cell types of plant and animal origin was made with the aid of video-enhanced contrast, differential interference contrast (AVEC-DIC) microscopy followed by fine analysis of the motile behavior of the individual organelles. We found that there exists besides Brownian motion a wide spectrum of active motions in cells, i.e. motion that is directionally biased through the expenditure of metabolic energy. The types of active motion seen range from a continuous motion (sometimes appearing as streaming) in plant cells and neurons to various types of less ordered and less well directed motion. We did not see any clear-cut qualitative difference between plant and animal cells or between systems presumed to be actin- and microtubule-based. A preliminary classification of the types of active motion is presented. The ongoing research activities, which aim at a more precise definition of the different types of motion by a set of quantitative parameters, are described, and the progress made so far is reported.

Animals↗
PubMed2001

Numerical simulation of streaming potentials due to deformation-induced hierarchical flows in cortical bone.

Bone is a very dynamic tissue capable of modiA,fing its composition, microstructure, and overall geometry in response to the changing biomechanical needs. Streaming potential has been hypothesized as a mechanotransduction mechanism that may allow osteocytes to sense their biomechanical environment. A correct understanding of the mechanism for streaming potential will illuminate our understanding of bone remodeling, such as the remodeling associated with exercise hypertrophy, disuse atrophy, and the bone remodeling arounid implants. In the current research, a numerical model based on the finite element discretization is proposed to simulate the fluid flows through the complicated hierarchical flow system and to calculate the concomitant stress generated potential (SGP) as a result of applied mechanical loading. The lacunae-canaliculi and the matrix microporosity are modeled together as discrete one-dimensional flow channels superposed in a biphasic poroelastic matrix. The cusplike electric potential distribution surrounding the Haversian canal that was experimentallv observed and reported in the literature earlier was successfully reproduced by the current numerical calculation.

Bone and Bones↗
PubMed1974

Endoplasmic filaments generate the motive force for rotational streaming in Nitella.

The streaming endoplasm of characean cells has been shown to contain previously unreported endoplasmic filaments along which bending waves are observed under the light microscope using special techniques. The bending waves are similar to those propagated along sperm tails causing propulsion of sperm. In Nitella there is reason to believe that nearly all of the filaments are anchored in the cortex and that their beating propels the endoplasm in which they are suspended. This hypothesis is supported by calculations in which typical and average wave parameters have been inserted into the classical hydrodynamic equations derived for sperm tail bending waves. These calculations come within an order of magnitude of predicting the velocity of streaming and they show that waves of the character described, propagated along an estimated 52 m of endoplasmic filaments per cell, must generate a total motive force per cell within less than an order of magnitude of the forces measured experimentally by others. If we assume that undulating filaments produce the force driving the endoplasm, then the method described for measuring the motive force could lead to a lower than actual value for the motive force, since both centrifugation and vacuolar perfusion would reverse the orientation of some filaments. Observations of the initiation of particle translation in association with the filaments suggest that particle transport and wave propagation, which occur at the same velocity, may both be dependent on the same process. The possibility that some form of contractility provides the motive force for filament flection and particle transport is discussed.

Chlorophyta↗
PubMed1983

Quantitative analysis of changes in cell shape of Amoeba proteus during locomotion and upon responses to salt stimuli.

A new parameter expressing the complexity of cell shape defined as (periphery)2/(area) in 2D projection was found useful for a quantitative analysis of changes in the cell shape of Amoeba proteus and potentially of any amoeboid cells. During locomotion the complexity and the motive force of the protoplasmic streaming in amoeba varied periodically, and the Fourier analysis of the two showed a similar pattern in the power spectrum, giving a rather broad peak at about 2.5 X 10(-3) Hz. The complexity increased mainly due to elongation of the cell as external Ca2+ increased. This effect was blocked by La3+, half the inhibition being attained at 1/200 amount of the coexisting Ca2+. On the other hand, the complexity decreased due to rounding up of the cell as the concentration of other cations, such as Sr2+, Mg2+, Co2+, Ni2+, Na+, K+ etc., increased. Irrespective of the opposite effects of Ca2+ and other cations on the cell shape, the ATP concentration in amoeba decreased in both cases with increase of all these cations. The irregularity in amoeboid motility is discussed in terms of a dynamic system theory.

Adenosine Triphosphate↗
PubMed1969

Studies on streaming. I. Inhibition of protoplasmic streaming and cytokinesis of Chaos chaos by adenosine triphosphate and reversal by magnesium and calcium ions.

In Chaos chaos streaming, motility, and cytokinesis were inhibited nearly 100% for several hours by 2.5-5 mM sodium adenosine triphosphate (ATP)(1) added to culture fluid. All three effects were completely prevented by the addition of equimolar Mg(++) or Ca(++) ions but not Na(+) to the ATP/culture fluid solution. The effects of ATP were not reproduced by EDTA, EGTA, colchicine, or AMP. Sodium pyrophosphate produced about 50% inhibition at 5 mM. Studies with (14)C-ATP showed that 5 x 10(-5) to 5 x 10(-4) mmole of ATP was firmly associated with each milliliter of packed cells after an hour's incubation at 24 degrees C. Labeling studies also showed that prevention of the ATP effects by Mg(++) ions was not due to a decrease in the amount of ATP associated with the cells.

Adenine Nucleotides↗