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At least 127 records · Page 7Linked to original sources

PubMed1989

Corneal epithelial cell movement in humans.

Evidence is presented which supports the centripetal movement of epithelial cells in the normal corneal epithelium. This movement is not, however, uniform and is influenced by various factors including corneal topography, surface disease states and lid shearing forces. We have studied epithelial morphology with corneal specular microscopy and have demonstrated altered morphology in keratoconjunctivitis sicca, neurotrophic keratitis, and contact lens wearing. Following penetrating keratoplasty, we found a vortex keratopathy in 70 per cent of patients up to two years after surgery. We also found pallisading of epithelial cells around sutures which indicated centripetal movement of epithelial cells around islands of stability created by obstructions. The eyelid also alters epithelial migration and turnover by increasing exfoliation from shearing forces. We advance a new hypothesis that the driving force in the central epithelial cell movement is the preferential loss of surface cells by exfoliation from the central apex secondary to the shearing forces of the upper lid.

Cell Movement↗

PubMed1981

Epibolin: a protein of human plasma that supports epithelial cell movement.

Earlier studies suggested that there is a specific activity in mammalian serum and plasma that supports epidermal (epithelial) cell movement. This activity was shown to be nondialyzable and heat labile. In the studies reported here, using standard biochemical procedures--i.e., ammonium sulfate fractionation, ion-exchange and gel filtration chromatography, isoelectric precipitation, and preparative polyacrylamide gel electrophoresis--we have purified a factor from human plasma that supports epidermal cell movement. The factor travels as an apparent single band on disc gel electrophoresis and corresponds to a glycosylated single-chain protein of approximately 65,000 +/- 3,000 daltons. The purified fraction is necessary and sufficient for dissociated epidermal cells, (ii) outgrowth of epithelial sheets from skin explants, and (iii) epiboly, epithelial sheet movement over a floating skin explant. The purified fraction is active at a concentration of 1-2 micrograms/ml of growth medium. It is destroyed by trypsin and its activity is augmented more than 10-fold by a second, as yet unpurified, fraction of plasma. These studies support the notion that a single protein of plasma supports epidermal cell movement and that this protein may play an important role in wound closure. Because it supports epiboly, the most biologically relevant of the assays, it has been named epibolin.

Cell Movement↗

PubMed1997

A short-range signal restricts cell movement between telencephalic proliferative zones.

During telencephalic development, a boundary develops that restricts cell movement between the dorsal cortical and basal striatal proliferative zones. In this study, the appearance of this boundary and the mechanism by which cell movement is restricted were examined through a number of approaches. The general pattern of neuronal dispersion was examined both with an early neuronal marker and through the focal application of DiI to telencephalic explants. Both methods revealed that, although tangential neuronal dispersion is present throughout much of the telencephalon, it is restricted within the boundary region separating dorsal and ventral telencephalic proliferative zones. To examine the cellular mechanism underlying this boundary restriction, dissociated cells from the striatum were placed within both areas of the boundary, where dispersion is limited, and areas within the cortex, where significant cellular dispersion occurs. Cells placed within the boundary region remain round and extend only thin processes, whereas progenitors placed onto the cortical ventricular zone away from this boundary are able to migrate extensively. This suggests that the boundary inhibits directly the migration of cells. To examine whether the signal inhibiting dispersion within the boundary region acts as a long- or short-range cue, we apposed explants of boundary and nonboundary regions in vitro. Within these explants we found that migration was neither inhibited in nonboundary regions nor induced in boundary regions. This suggests that the boundary between dorsal and ventral telencephalon isolates these respective environments through either a contact-dependent or a short-range diffusible mechanism.

Acridine Orange↗

PubMed2003

The movement protein gene is involved in the virus-specific requirement of the coat protein in cell-to-cell movement of bromoviruses.

Brome mosaic virus (BMV) requires the coat protein (CP) for cell-to-cell movement whereas Cowpea chlorotic mottle virus (CCMV), from the same genus, does not. Chimeric viruses created by exchanging the movement protein (MP) gene between the viruses can move from cell to cell. We show that interference in CP expression impaired the movement of the chimeric CCMV with the BMV MP gene but not of the chimeric BMV with the CCMV MP gene. We thus conclude that the MP gene plays a crucial role in determination of the virus-specific CP requirement in bromovirus cell-to-cell movement.

Amino Acid Sequence↗

PubMed2005

The zebrafish down syndrome cell adhesion molecule is involved in cell movement during embryogenesis.

The Down syndrome cell adhesion molecule (Dscam) is a protein overexpressed in the brains of Down syndrome patients and implicated in mental retardation. Dscam is involved in axon guidance and branching in Drosophila, but cellular roles in vertebrates have yet to be elucidated. To understand its role in vertebrate development, we cloned the zebrafish homolog of Dscam and showed that it shares high amino acid identity and structure with the mammalian homologs. Zebrafish dscam is highly expressed in developing neurons, similar to what has been described in Drosophila and mouse. When dscam expression is diminished by morpholino injection, embryos display few neurons and their axons do not enter stereotyped pathways. Zebrafish dscam is also present at early embryonic stages including blastulation and gastrulation. Its loss results in early morphogenetic defects. dscam knockdown results in impaired cell movement during epiboly as well as in subsequent stages. We propose that migrating cells utilize dscam to remodel the developing embryo.

Amino Acid Sequence↗

PubMed1999

Regulation of cell movement is mediated by stretch-activated calcium channels.

Intracellular calcium regulates many of the molecular processes that are essential for cell movement. It is required for the production of actomyosin-based contractile forces, the regulation of the structure and dynamics of the actin cytoskeletons, and the formation and disassembly of cell-substratum adhesions. Calcium also serves as a second messenger in many biochemical signal-transduction pathways. However, despite the pivotal role of calcium in motile processes, it is not clear how calcium regulates overall cell movement. Here we show that transient increases in intracellular calcium, [Ca2+]i, during the locomotion of fish epithelial keratocytes, occur more frequently in cells that become temporarily 'stuck' to the substratum or when subjected to mechanical stretching. We find that calcium transients arise from the activation of stretch-activated calcium channels, which triggers an influx of extracellular calcium. In addition, the subsequent increase in [Ca2+]i is involved in detachment of the rear cell margin. Thus, we have defined a mechanism by which cells can detect and transduce mechanical forces into biochemical signals that can modulate locomotion.

Animals↗

PubMed2001

Cell-to-cell movement and assembly of a plant closterovirus: roles for the capsid proteins and Hsp70 homolog.

Diverse animal and plant viruses are able to translocate their virions between neighboring cells via intercellular connections. In this work, we analyze the virion assembly and cell-to-cell movement of a plant closterovirus and reveal a strong correlation between these two processes. The filamentous virions of a closterovirus possess a long body formed by the major capsid protein (CP) and a short tail formed by the minor capsid protein (CPm). Genetic and biochemical analyses show that the functions of these virion components are distinct. A virion body is required primarily for genome protection, whereas a tail represents a specialized device for cell-to-cell movement. Furthermore, tail assembly is mediated by the viral Hsp70 homolog (Hsp70h) that becomes an integral part of the virion. Inactivation of the ATPase domain of Hsp70h results in assembly of tailless virions that are incapable of translocation. A dual role for the viral molecular chaperone Hsp70h in virion assembly and transport, combined with the previous finding of this protein in intercellular channels, allowed us to propose a model of closteroviral movement from cell to cell.

Amino Acid Sequence↗

PubMedDate not supplied

Cell movement and symmetry of the cellular environment.

The movement of micro-organisms was investigated in different cellular environments. The type of movement was described in terms of the symmetry of the cellular environment: (i) Random movement - isotropic symmetry of the environment, (ii) contact guidance - apolar symmetry of the environment and (iii) directed movement as chemotaxis and galvanotaxis - polar symmetry of the environment. To quantitate cell movement it was necessary to parameterize the environment as well as the cell movement by observables. The random movement was quantitated by the diffusion coefficient. The contact guidance of the nematic type and the contact guidance on a bent surface were quantified by an apolar order parameter. The contact guidance constant for fibroblast on a glass cylinder was 87.5 microns. The directed movement was quantified by a polar order parameter. Dose-response curves were derived and compared for different types of cells: Chemotaxis of granulocytes KCT-1 = 2.2 mm for 10 microM f-Met-Met-Met, galvanotaxis of granulocytes KG-1 = 0.2 V/mm, galvanotaxis of fibroblast KG-1 = 0.28 V/mm, galvanotaxis of spermatozoids of bracken fern KG-1 = 0.024 V/mm.

Cell Movement↗

PubMed1989

A study on skeletal myogenic cell movement in the developing avian limb bud.

Quail limb mesenchyme containing myogenic cells of somitic origin were transplanted into chick limb buds to determine whether cell movement might play a role in avian limb myogenesis. In general, cell displacement was not detected 1-day after implantation: all quail cells were found at the graft site. Migration was evident 2-days after implantation but not all cell types were capable of movement; myogenic cells were very invasive while chondrocytes were relatively immobile. The spreading of myogenic cells was discernible up to 4-days after implantation and specifically in a proximodistal direction towards the apex of the limb.

Animals↗

PubMed2003

Coupling cell movement to multicellular development in myxobacteria.

The myxobacteria are Gram-negative organisms that are capable of multicellular, social behaviour. In the presence of nutrients, swarms of myxobacteria feed cooperatively by sharing extracellular digestive enzymes, and can prey on other bacteria. When the food supply runs low, they initiate a complex developmental programme that culminates in the production of a fruiting body. Myxobacteria move by gliding and have two, polarly positioned engines to control their motility. The two engines undergo coordinated reversals, and changes in the reversal frequency and speed are responsible for the different patterns of movement that are seen during development. The myxobacteria communicate with each other and coordinate their movements through a cell-contact-dependent signal. Here, the cell movements that culminate in the development of the multicellular fruiting body are reviewed.

Morphogenesis↗

PubMed2001

Conversion in the requirement of coat protein in cell-to-cell movement mediated by the cucumber mosaic virus movement protein.

Plant viruses have movement protein (MP) gene(s) essential for cell-to-cell movement in hosts. Cucumber mosaic virus (CMV) requires its own coat protein (CP) in addition to the MP for intercellular movement. Our present results using variants of both CMV and a chimeric Brome mosaic virus with the CMV MP gene revealed that CMV MP truncated in its C-terminal 33 amino acids has the ability to mediate viral movement independently of CP. Coexpression of the intact and truncated CMV MPs extremely reduced movement of the chimeric viruses, suggesting that these heterogeneous CMV MPs function antagonistically. Sequential deletion analyses of the CMV MP revealed that the dispensability of CP occurred when the C-terminal deletion ranged between 31 and 36 amino acids and that shorter deletion impaired the ability of the MP to promote viral movement. This is the first report that a region of MP determines the requirement of CP in cell-to-cell movement of a plant virus.

Bromovirus↗

PubMed2006

The dynamic geometry of mass cell movements in animal morphogenesis.

There is an infinite number of interactions between morphogenetic processes of different time and space scales. How do these unfold in a regular series of mass morphogenetic movements to produce a basically simple and reproducible structure? I present a new morphogenetic concept -- the spatial unfolding (SU) of cell movements, whose definition rests on the correspondence between the continuous spatial series of cell shapes and the succession of changes in the shape of a single cell moving in an epithelial sheet whose shape is also subject to change. The change in the shape of moving cells is the only measure of their translocation both in space and time. The SU provides a morpho-dynamics description of mass cell movements which is completely independent of both an external coordinate system and external forces. The cell geometry of SU allows us to derive the future embryonic form from the actual one by a movement-shaping algorithm operating on the basis of positive and negative geometric feedbacks between the cell movement in the epithelial sheet plane and the epithelial sheet shaping, the feedback system providing a geometric alternative to Turing's self-organization via reaction-diffusion systems. Putting together histological, quantitative morphological and experimental data permits us to isolate four SU, each acting in morphogenesis as an irreducible whole, which seem to include all real examples of epithelial morphogenesis in multicellular animals, from Coelenterates to Chordates.

Animals↗

PubMedDate not supplied

Dynamics of cell movement during the wound repair of human surface respiratory epithelium.

Epithelial wound repair represents an important process by which the epithelial barrier integrity recovers after wounding. To evaluate and quantify the dynamics of surface airway cell movement during the wound repair process, we developed an in vitro wounding model of human respiratory cells in culture and we analyzed the wound repair by using videomicroscopic and image analysis techniques. We observed that wound closure occurred within 6 hours, due to the spreading and migration of the cells surrounding the wounded surface. The migration rate of the cells at the leading edge of the wound surface increased progressively up to 26 microns/h during the repair process which was characterized by a uniform centripetal direction of cell movement. The distance travelled by these cells was 2.5 fold longer than the distance travelled by ciliated cells which were located far from the wound area. These results suggest that cell migration after wounding is an important process by which the respiratory epithelial barrier integrity is maintained.

Cell Movement↗

PubMed2000

Regulation of plasmodesmal transport by phosphorylation of tobacco mosaic virus cell-to-cell movement protein.

Cell-to-cell spread of tobacco mosaic virus (TMV) through plant intercellular connections, the plasmodesmata, is mediated by a specialized viral movement protein (MP). In vivo studies using transgenic tobacco plants showed that MP is phosphorylated at its C-terminus at amino acid residues Ser258, Thr261 and Ser265. When MP phosphorylation was mimicked by negatively charged amino acid substitutions, MP lost its ability to gate plasmodesmata. This effect on MP-plasmodesmata interactions was specific because other activities of MP, such as RNA binding and interaction with pectin methylesterases, were not affected. Furthermore, TMV encoding the MP mutant mimicking phosphorylation was unable to spread from cell to cell in inoculated tobacco plants. The regulatory effect of MP phosphorylation on plasmodesmal permeability was host dependent, occurring in tobacco but not in a more promiscuous Nicotiana benthamiana host. Thus, phosphorylation may represent a regulatory mechanism for controlling the TMV MP-plasmodesmata interactions in a host-dependent fashion.

Amino Acids↗

PubMed1998

Characterization of cucumber mosaic virus. V. Cell-to-cell movement requires capsid protein but not virions.

To ascertain the importance of amino-terminal proximal capsid protein (CP) sequences in cel-to-cell movement, virion formation, and stabilization, two CP mutants of cucumber mosaic virus (CMV) were generated by deletion of sequences encoding CP amino acids 15-40 (delta Sal-Nru) or 26-40 (delta Sac-Nru). Wildtype CMV and CMV containing delta Sac-Nru could infect systemically four host species, although symptoms induced by the two viruses usually were different CMV containing delta Sal-Nru could only infect Nicotiana benthamiana and N. clevelandii systemically, but only slowly, suggesting phloem-independent long-distance movement. A variant mutant designated delta Sal-Nru* could systemically infect N. tabacum as well as the above two Nicotiana species, rapidly, but could not systemically infect Cucurbita pepo. Virus particles could not be detected in plants infected by delta Sal-Nru, while delta Sal-Nru* and delta Sac-Nru formed particles of lower stabilities than for wildtype virus. The CPs of delta Sal-Nru and delta Sal-Nru* could bind RNA in vitro, although less strongly than delta Sac-Nru or wildtype CMV. These data indicate that amino-terminal proximal sequences of the CMV CP interact with viral RNA and are required for the formation of stable virions. Moreover, while the CP is necessary for cell-to-cell movement, the ability to form virions is not a prerequisite for cell-to-cell movement.

Amino Acid Sequence↗

PubMed1997

Molecular studies on bromovirus capsid protein. III. Analysis of cell-to-cell movement competence of coat protein defective variants of cowpea chlorotic mottle virus.

To determine whether the role of coat protein (CP) in cell-to-cell movement of dicot-adapted cowpea chlorotic mottle bromovirus (CCMV) is distinct from that of monocot-adapted brome mosaic bromovirus (BMV), two reporter genes, beta-glucuronidase (GUS) and enhanced green fluorescent protein (EGFP), were substituted for the CP in a biologically active clone of CCMV RNA3 (C3). Primary leaves of Nicotiana benthamiana, Chenopodium quinoa, and cowpea were co-inoculated with wild-type (wt) CCMV RNA 1 and -2 and either C3/delta CP-GUS or C3/delta CP-EGFP and analyzed for GUS activity or the presence of green fluorescence. The visual appearance of infections caused by GUS or EGFP variants indicated that, in CCMV, epidermal cell-to-cell movement can occur without a functional CP. By contrast, inoculation of MP defective variants of C3/delta CP-GUS or C3/delta CP-EGFP resulted in subliminal infections. Additional experiments examining the infectivity of wt BMV RNA 1 and -2 and a BMV RNA3 variant bearing the EGFP in the place of CP (B3/delta CP-EGFP) confirmed previous observations that, unlike CCMV, epidermal cell-to-cell movement of BMV is dependent on the expression of a functional CP. Taken together, the results demonstrate that BMV and CCMV use different mechanisms for initial epidermal cell-to-cell spread, and the individual role played by the respective CP genes in this active process is discussed.

Bromovirus↗

PubMedDate not supplied

A system for computer analysis of cancer cell movement.

BACKGROUND: Motility of cancer cells is a principal cellular parameter, essentially required in the invasion and formation of distant metastasis in human cancer. Measures to stimulate or inhibit motility of cancer cells may play an important part in the understanding of metastasis biology. The aim of this study was to develop a computer system to analyse and evaluate the movement of cells. METHOD: Software was developed which enabled cell boundary definition by specifying salient points around the cell. The position of the centre of area was calculated. Six human cancer cells treated with a motogen and cells without added motogen were analysed by the system. RESULTS: We observed higher velocities and greater variation in area and velocity of the cells treated with HGF/SF motogen compared with control cells. CONCLUSION: The system enables rapid analysis of cell area, velocity and movement, and may thus be of value in further understanding cell motility.

Cell Movement↗

PubMed2001

A differential role of extracellular signal-regulated kinase in stimulated PC12 pheochromocytoma cell movement.

Rat pheochromocytoma PC12 cells have been widely used as a cell system for study of growth factor-stimulated cell functions. We report here that nerve growth factor (NGF) stimulated both chemotaxis (directional migration) and chemokinesis (random migration) of PC12 cells. Treatment with a MEK1/2-specific inhibitor (PD98059) or expression of a dominant negative variant of Ras differentially inhibited NGF-stimulated chemotaxis but not chemokinesis of PC12 cells. Priming of PC12 cells with NGF resulted in reduced extracellular signal-regulated kinase (ERK) activation and loss of chemotactic, but not chemokinetic, response. In addition, NGF stimulation of ERK is known to involve an early transient phase of activation followed by a late sustained phase of activation; in contrast, epidermal growth factor (EGF) elicits only early transient ERK activation. We observed that like NGF, EGF also stimulated both chemotaxis and chemokinesis, and treatment with PD98059 abolished the EGF-stimulated chemotaxis. Therefore, the early transient phase of ERK activation functioned in signaling chemotaxis; the late sustained phase of ERK activation did not seem to have an essential role. In addition, our results suggested that chemotactic signaling required a threshold level of ERK activation; at below threshold level of ERK activation, chemotaxis would not occur.

Animals↗