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At least 109 records · Page 6Linked to original sources
PubMed1997

Characterization of cucumber mosaic virus. IV. Movement protein and coat protein are both essential for cell-to-cell movement of cucumber mosaic virus.

cDNA clones of cucumber mosaic virus (CMV) RNA 3 were modified to express the jellyfish green fluorescent protein (GFP) in place of the 3a movement protein (MP) or coat protein (CP), as fusions to the N (GFP-3a) or C (3a-GFP) terminus of the MP or from a separate open reading frame as part of tricistronic RNAs 3. CMV RNA transcripts containing the individual modified RNAs 3 were unable to infect either Nicotiana tabacum or Nicotiana benthamiana systemically. Infection, as measured by confocal microscopy of GFP fluorescence, generally was limited to one to three epidermal cells at each inoculation site. Limited cell-to-cell movement, but not systemic movement, could be detected by complementation involving expression of MP and CP from two different RNA 3 constructs, each also expressing GFP. Infection involving RNA 3 expressing the GFP-3a fusion showed bright granules of variable size distributed predominantly and nonuniformly throughout the cytoplasm and, to a lesser extent, associated with the cell wall in single fluorescent cells, while infections expressing the 3a-GFP fusion showed bright, punctate fluorescence associated only with the cell wall. Infected cells expressing either 3a-GFP or free GFP showed a halo of less bright, fluorescent, neighboring cells, indicating limited movement of GFP. The initially infected cells also allowed movement of 10-kDa fluorescent dextran to the neighboring halo cells, while infection did not spread, suggesting different requirements for movement of either MP or dextran versus RNA.

Capsid↗
PubMed2004

Cell polarity, intercellular signalling and morphogenetic cell movements in Myxococcus xanthus.

In Myxococcus xanthus morphogenetic cell movements constitute the basis for the formation of spreading vegetative colonies and fruiting bodies in starving cells. M. xanthus cells move by gliding and gliding motility depends on two polarly localized engines, type IV pili pull cells forward, and slime extruding nozzle-like structures appear to push cells forward. The motility behaviour of cells provides evidence that the two engines are localized to opposite poles and that they undergo polarity switching. Several proteins involved in regulating polarity switching have been identified. The cell surface-associated C-signal induces the directed movement of cells into nascent fruiting bodies. Recently, the molecular nature of the C-signal molecule was elucidated and the motility parameters regulated by the C-signal were identified. From the effect of the C-signal on cell behaviour it appears that the C-signal inhibits polarity switching of the two motility engines. This establishes a connection between cell polarity, signalling by an intercellular signal and morphogenetic cell movements during fruiting body formation.

Bacterial Proteins↗
PubMed1984

Analysis of cell movement.

The methods of statistical physics have been applied to the analysis of cell movement. Human leukocytes (granulocytes) were observed using time-lapse photography. The center of gravity of a cell, variations of cell shape, and cell orientation were investigated. This analytical description leads to a better understanding of cell movement. Stationary motion of a cell is described by the anisotropy of the cell shape. The cell displacement can be characterized by three different types of movement: The persistent mode where the cell moves away from an arbitrary chosen origin with its track velocity. The diffusion mode where the cells become dispersed in space by a random walk process. The drift mode where the cell moves with a drift velocity, v parallel, in a concentration gradient of chemoattractant molecules. The chemokinetic response is described by the diffusion constant D (= 240 microns2/min) and the track velocity vc (= 30 microns/min). The chemotactic response is described by the degree of orientation P1 (= 0.8), which is identical with the McCutcheon index and the chemotropism index. Cell movement can be described by elementary moving states, and the life time of such a moving state is 0.5 min. The survival probability of the moving state is determined by an internal program. It is not described by a stochastic process. The angular change in moving direction is also programmed, as the square root of the mean square angular change is +/- 50 degrees. The plus and minus direction are equally probable in a chemokinetic response. However, in a chemotactic assay the plus and minus directions are not equally probably. We found that the information transfer from the chemotactic gradient to the migrating cell is 1 bit per change in moving direction. A disturbance in this information transfer leads to an order-disorder transition. Furthermore, we found that the migrating cell exhibits a directional memory of 75 s.

Biophysical Phenomena↗
PubMed1994

Cell movement and shape are non-random and determined by intracellular, oscillatory rotating waves in Dictyostelium amoebae.

We present evidence for a mechanism of eukaryotic cell movement. The pseudopodial dynamics and shape of Dictyostelium discoideum amoebae were investigated using computer-supported video microscopy. An examination of the cell periphery by the novel method of serial circular maps revealed explicit, classical wave patterns, which indicate the existence of intrinsic intracellular oscillations. The patterns are generated by the transit of self-organized, super-positioned, harmonic modes of rotating oscillatory waves (ROWS). These waves are probably associated with the dynamics of intracellular actin polymerisation and depolymerisation. A Karhunen-Loève expansion was conducted on one cell during 10 min of locomotion using points each 10 degrees around the cell's boundary. The results show that only 2-3 modes are necessary to describe the most essential features of cell movement and shape. Based on this analysis, a wave model was developed, which accurately simulates the dynamics of cell movement and shape during this time. The model was tested by reconstructing the cell's dynamical form by means of the Karhunen-Loève transform. No difference was detected between this reconstruction and the actual cell outline. Although cell movement and shape have hitherto been viewed as random, our results demonstrate that ROWS determine the spatio-temporal expression of pseudopodia, and consequently govern cell shape and movement, non-randomly.

Animals↗
PubMed1989

Relation between the rate of cell movement under agarose and the positioning of cells in heterotypic aggregates.

Single-cell suspensions prepared from 9-day-old chick tissues (skeletal muscle, liver, and neural retina) were used to investigate a possible relationship between intrinsic mobilities of different cell types and their positioning behavior in mixed (heterotypic) cellular aggregates. The relative mobilities of the three cell types, determined by comparing their ability to migrate under an agarose layer, was muscle greater than liver greater than neural retina. The gyratory shaker method was employed to produce heterotypic aggregates from mixed suspensions of muscle, liver, and neural retina cells and the tissue-specific positioning of cells after 24 h in culture was determined from histological and autoradiograph sections. The hierarchy for "inside" positioning of segregated cells was muscle greater than liver greater than neural retina cells, correlating with the rate of movement of these cells in the migration assay. The implication of the results is that relative speed of movement may determine the positioning of cells in heterotypic aggregates.

Animals↗
PubMed1996

Growth factors and the kidney: regulation of epithelial cell movement and morphogenesis.

The control of epithelial cell movement and shape change is complex and requires regulation of a broad range of events including cell-cell adhesion contacts, cell-substratum interactions, and the actin cytoskeleton. Utilizing the hepatocyte growth factor tyrosine kinase receptor, c-met, the present review examines how growth factor receptors activate intracellular signaling pathways, which can then regulate the events necessary for epithelial cells to disassemble their existing structure, undergo extensive shape change and cell body movement, and reassemble into a polarized epithelium. The role of growth factor-mediated activation of the phosphoinositide 3-kinase, phospholipase C-gamma, c-src family members, and ras family members is addressed in relation to integrin-mediated cell-basement membrane contacts, cadherin-mediated cell-cell adhesions, and regulation of the actin cytoskeleton.

Animals↗
PubMed1988

Directional cell movement during early development of the teleost Blennius pholis: II. Transformation of the cells of epithelial clusters into dendritic melanocytes, their dissociation from each other, and their migration to and invasion of the pectoral fin buds.

After clusters of pigmented epithelial cells have rested immobile in the yolk sac of Blennius pholis for 2-4 days (Trinkaus, '88), their constituent cells transform into mesenchymal, dendritic melanocytes. Then these melanocytes dissociate from one another and migrate directionally toward the developing pectoral fin bud (PFB) on either side. Each of these changes takes place in a proximodistal sequence, starting with the epithelial cluster closest to each PFB. Even individual clusters conform to this sequence, the proximal side dissociating first. Eventually, all melanocytes reach and invade the PFB. This is a 100% efficient morphogenetic cell movement. At the completion of this developmental sequence, each PFB is filled with melanocytes arranged in an arc with their filopodia extending outward and the yolk sac is bereft of pigment cells. The form and surface activity of these cells in relation to their motility and to their rate of movement are considered in detail. Attempts to understand the forces involved in giving directionality to these cell migrations are described. Finally, the significance of these observations for morphogenetic cell movements generally and for the relation between epithelial and mesenchymal cells is discussed briefly.

Animals↗
PubMed1999

Molecular interactions continuously define the organizer during the cell movements of gastrulation.

The organizer is a unique region in the gastrulating embryo that induces and patterns the body axis. It arises before gastrulation under the influence of the Nieuwkoop center. We show that during gastrulation, cell movements bring cells into and out of the chick organizer, Hensen's node. During these movements, cells acquire and lose organizer properties according to their position. A "node inducing center," which emits Vg1 and Wnt8C, is located in the middle of the primitive streak. Its activity is inhibited by ADMP produced by the node and by BMPs at the periphery. These interactions define the organizer as a position in the embryo, whose cellular makeup is constantly changing, and explain the phenomenon of organizer regeneration.

Amino Acid Sequence↗
PubMed2005

Proteoglycan control of cell movement during wound healing and cancer spreading.

By virtue of their multifunctional nature, proteoglycans (PGs) are thought to govern the process of cell movement in numerous physiological and pathological contexts, spanning from early embryonic development to tumour invasion and metastasis. The precise mode by which they influence this process is still fragmentary, but evidence is accruing that they may affect it in a multifaceted manner. PGs bound to the plasma membrane mediate the polyvalent interaction of the cell with matrix constituents and with molecules of the neighbouring cells' surfaces; they modulate the activity of receptors implicated in the recognition of these components; and they participate in the perception and convergence of growth- and motility-promoting cues contributed by soluble factors. Through some of these interactions several PGs transduce to pro-motile cells crucial intracellular signals that are likely to be essential for their mobility. A regulated shedding of certain membrane-intercalated PGs seems to provide an additional level of control of cell movement. Coincidentally, matrix-associated PGs may govern cell migration by structuring permissive and non-permissive migratory paths and, when directly secreted by the moving cells, may alternatively create favourable or hostile microenvironments. To exert this latter, indirect effect on cell movement, matrix PGs strongly rely upon their primary molecular partners, such as hyaluronan, link proteins, tenascins, collagens and low-affinity cell surface receptors, whereas a further finer control is provided by a highly regulated proteolytic processing of the PGs accounted by both the migrating cells themselves and cells of their surrounding tissues. Overall, PGs seem to play an important role in determining the migratory phenotype of a cell by initiating, directing and terminating cell movement in a spatio-temporally controlled fashion. This implies that the "anti-adhesive and/or "anti-migratory" properties that have previously been assigned to certain PGs may be re-interpreted as being a means by which these macromolecules elaborate haptotaxis-like mechanisms imposing directionality upon the moving cells. Since these conditions would allow cells to be led to given tissue locations and become immobilized at these sites, a primary function may be ascribed to PGs in the dictation of a "stop or go" choice of the migrating cells.

Cell Adhesion↗
PubMed1982

Cell movements in a living mammalian tissue: long-term observation of individual cells in wounded corneal endothelia of cats.

Although the cells in tissues are known to be motile under special conditions (e.g., during tissue turnover or wound healing), there are not many reports that polygonal cells covering an area without leaving any gaps are also capable of movement. In the present study, cell movements (cell shifting and rearrangement) in a living mammalian eye tissue were documented by identifying and locating individual cells over intervals as long as 100 days. Cat corneal endothelium, a monolayered cell sheet, was wounded by removing a small number (about 180) of endothelial cells from the internal lining of the cornea. Healing of the wounded tissue was observed with a wide-view specular microscope applied to the outer surface of the cornea, enabling us to identify individual cells for as long as two to three months. Cells surrounding the wound underwent areal enlargement, elongated toward the wound, and shifted to cover the wound surface. During days 4-7, cells became rearranged by changing neighbors in such a way that they retained their enlarged size but recovered their non-elongated, original shape. This pattern of cell rearrangement was interpreted by a computer simulation which assumed that cells shorten their boundary length while maintaining contacts with contiguous cells. After day 7, the enlarged cells adjacent to the wounded area gradually contracted and pulled surrounding cells toward the wounded area. These movements were followed by a temporary halt in cell shifting, then by a recovery of shifting and cell elongation. These movements are interpreted as a result of the contractility of endothelial cell microfilaments.

Animals↗
PubMed1998

Induction of optical density waves and chemotactic cell movement in Dictyostelium discoideum by microinjection of cAMP pulses.

The development of most multicellular organisms involves coordinated cell movement. The early aggregation of Dictyostelium cells has been shown to be mediated by chemotactic movement to propagating waves of cAMP. We have proposed that propagating waves of a chemoattractant, most likely cAMP, also control the movement of cells in mounds and slugs. We have now used periodic pressure injection of pulses of cAMP in the extracellular space of aggregation streams, mounds, and slugs to investigate whether these signals can be relayed and control cell movement, using quantitative digital time-lapse microscopy. Our major findings are (1) short (0.1 s) pulses of cAMP (10(7) molecules) were able to elicit optical density (OD) waves in fields of aggregating amoebae. They propagate from the micropipet outward and interact with endogenous OD waves. (2) Periodic injection of cAMP pulses into aggregation streams blocked the pulses coming from the center and led to the rapid accumulation of cells downstream of the pipet around the pipet. (3) Injection of pulses of cAMP into mounds elicited OD waves, which propagated from the pipet outward and interacted with the endogenous waves, indicating that the same propagator carries them. (4) Periodic microinjection of cAMP in the prespore zone of slugs led to accumulation of anterior-like cells around the micropipet followed by tip formation. Furthermore, the cAMP signal could control the spacing of the endogenous sorting pattern. These results strongly support the hypothesis that the optical density waves observed during early development up to the mound stage represent propagating cAMP waves. They suggest furthermore that cAMP is the morphogen that controls cell movements in slugs.

Animals↗
PubMed2001

Morphogenetic cell movements in the middle region of the dermomyotome dorsomedial lip associated with patterning and growth of the primary epaxial myotome.

The morphogenetic cell movements responsible for growth and morphogenesis in vertebrate embryos are poorly understood. Myotome precursor cells undergo myotomal translocation; a key morphogenetic cell movement whereby myotomal precursor cells leave the dermomyotome epithelium and enter the subjacent myotome layer where myogenic differentiation ensues. The precursors to the embryonic epaxial myotome are concentrated in the dorsomedial lip (DML) of the somite dermomyotome (W. F. Denetclaw, B. Christ and C. P. Ordahl (1997) Development 124, 1601-1610), a finding recently substantiated through surgical transplantation studies (C. P. Ordahl, E. Berdougo, S. J. Venters and W. F. Denetclaw, Jr (2001) Development 128, 1731-1744). Confocal microscopy was used here to analyze the location and pattern of myotome cells whose precursors had earlier been labeled by fluorescent dye injection into the middle region of the DML, a site that maximizes the potential to discriminate among experimental outcomes. Double-dye injection experiments conducted at this site demonstrate that cells fated to form myotome do not involute around the recurved epithelium of the DML but rather are displaced laterally where they transiently intermingle with cells fated to enter the central epithelial sheet region of the dermomyotome. Time- and position-dependent labeling experiments demonstrated that myotome precursor cells translocate directly from the middle region of the DML without prior intra-epithelial 'translational' movements of precursor cells to either the cranial or caudal lips of the dermomyotome epithelium, nor were any such translational movements evident in these experiments. The morphogenetic cell movements demonstrated here to be involved in the directional growth and segmental patterning of the myotome and dermomyotome bear interesting similarities with those of other morphogenetic systems.

Animals↗
PubMed1975

Cell movement and adhesion in the developing chick wing bud: studies on cultured mesenchyme cells from normal and talpid mutant embryos.

Mesenchyme fragments from early wing buds of normal and talpid3 mutant chick embryos were explanted for culture in plastic Petri dishes and the behaviour of individual cells as they moved out on to the plastic surface was studied by time-lapse ciné photography, followed by statistical analysis. Two parameters of cell movement were recorded: (1) the distances moved over measured 100-s intervals and (2) the length of time each cell spent at rest before moving on. The average speed of movement over the whole path tracked for each cell, inclusive of time at rest, was significantly greater in normal than talpid3 cells. There was no significant difference between normal and mutant cells in the average distance mover per 100-s step, equivalent to the speed over the whole path exclusive of time at rest, but the percentage of time spent at rest was significantly less in normal than in talpid3 cells. This difference appears to be related to a difference in cell morphology, since it was observed that the mutant cells were more flattened than normals, with very extensive ruffled membranes and short spiky microvilli all round the cell periphery. The relation of these differences in cell morphology and behaviour in vitro to the production of the characteristically fan-shaped limb bud outgrowth and altered pattern of cartilage elements in the developing mutant limb bud is discussed.

Animals↗
PubMed1984

Cell movement analysis in a necrotactic assay.

The methods of statistical physics have been applied to analysis of cell movement. Human leukocytes (granulocytes) were observed using time-lapse photography. The paths of the migrating cells were determined. The chemokinetic response at 35 degrees C is described by the diffusion constant (D = 233 micron2/min) and the track velocity (25 micron/min). A time-dependent chemotactic gradient is created by killing an erythrocyte by an intense laser flash. The chemotactic response at 35 degrees C is described by the degree of polar orientation (P1 = 0.85), the track velocity 24 micron/min, and the drift velocity towards the necrotactic source (v parallel = 20 micron/min). The track velocity as well the drift velocity show a broad distribution. The half-width of the velocity distribution. The half-width of the velocity distribution is approximately 5 micron/min. Cell movement can be described by elementary moving states. The characteristic time of the internal clock of the migrating cell is approximately 0.5 min. We found that the information transfer from the necrotactic gradient to the migrating cell is 1 bit per change in directed movement. A migrating cell cannot be stimulated within a period of approximately 10 s after the last decision to adapt a new moving direction.

Biophysical Phenomena↗
PubMed2004

E-cadherin regulates cell movements and tissue formation in early zebrafish embryos.

E-cadherin is maternally expressed in most vertebrate species, but its function during early development of the vertebrate embryo proper is unknown. To directly examine E-cadherin gene (cdh1) function in zebrafish, morpholino oligonucleotides (MOs) that inhibit E-cadherin protein (Cdh1) expression were injected into embryos. Cdh1 knockdown reduced embryo survival. In early cdh1 MO-injected embryos, the cleavage plane orientation between blastomeres was irregular and adhesion defects prevented normal compaction. Cdh1 knockdown inhibited epiboly cell movements. Epiboly delay caused yolk cell lysis and produced embryos with a bifurcated embryonic axis. Cdh1 knockdown inhibited gastrulation cell movements, causing defects in convergence and extension. Additionally, prechordal plate derivatives were absent in Cdh1 knockdown embryos even though presumptive prechordal plate markers were induced normally. E-cadherin mRNA coinjection demonstrated the specificity of cdh1 MO-induced defects. Our experiments illustrate the importance of cdh1 in regulating morphogenetic cell movements and tissue formation in the early embryo.

Animals↗
PubMed1990

Patterns of cell movement in early organ primordia of the chick embryo.

Purse-string constriction of the cytoskeleton at cell poles is generally accepted as the causal mechanism for invagination during early stages of organ formation. However, it is known that other cell movements, including intercalation, play a role in the organotypic shape changes that occur during gastrulation and neurulation. Such cell movements have not been investigated in pouching and branching epithelial primordia. There is reason to suspect that cells within these organ primordia might exchange their neighbors for others, that is, intercalate or translocate, at sites of sharp folding such as borders with the surrounding epithelial sheet or where a bend occurs within the primordium. The greatest difficulty in identifying these movements has been the need to use intact embryos so that the processes are not distorted. This study explores the possibility of using time-lapse video recording to identify cell movement at these locations. Three organ primordia were tested: otic and thyroid placodes, which had not been tested previously, and neural plate as a control, where movements of this sort have been documented. Embryos or parts containing the primordia were immobilized and cell apices visualized with Hoffman modulation contrast optics. Recordings to an optical memory disc recorder were transferred to a microcomputer for image analysis. The viewing procedure allows reasonably clear visualization of cell apices, and image analysis permits tracking of a number of adjacent cell apices over an extended time period. Several types of movement were found to occur within cell sheets, and the relative abundance of each type depends on the specific primordium. In the neural plate, some cells move many cell diameters from their neighbors. In the other two primordia, most cells show limited shifts in position relative to their neighbors except at regions where folds are formed. In other regions, adjacent cells move as a unit. Knowledge of the movements which occur in any particular primordium is essential to an understanding of the mechanisms controlling its formation.

Animals↗