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Motile Cells (motile + cell)
Selected AbstractsTalin2 is induced during striated muscle differentiation and is targeted to stable adhesion complexes in mature muscleCYTOSKELETON, Issue 3 2007Melissa A. Senetar Abstract The cytoskeletal protein talin serves as an essential link between integrins and the actin cytoskeleton in several similar, but functionally distinct, adhesion complexes, including focal adhesions, costameres, and intercalated disks. Vertebrates contain two talin genes, TLN1 and TLN2, but the different roles of Talin1 and Talin2 in cell adhesion are unclear. In this report we have analyzed Talin1 and Talin2 in striated muscle. Using isoform-specific antibodies, we found that Talin2 is highly expressed in mature striated muscle. Using mouse C2C12 cells and primary human skeletal muscle myoblasts as models of muscle differentiation, we show that Talin1 is expressed in undifferentiated myoblasts and that Talin2 expression is upregulated during muscle differentiation at both the mRNA and protein levels. We have also identified regulatory sequences that may be responsible for the differential expression of Talin1 and Talin2. Using GFP-tagged Talin1 and Talin2 constructs, we found that GFP-Talin1 targets to focal adhesions while GFP-Talin2 targets to abnormally large adhesions in myoblasts. We also found that ectopic expression of Talin2 in myoblasts, which do not contain appreciable levels of Talin2, dysregulates the actin cytoskeleton. Finally we demonstrate that Talin2, but not Talin1, localizes to costameres and intercalated disks, which are stable adhesions required for the assembly of mature striated muscle. Our results suggest that Talin1 is the primary link between integrins and actin in dynamic focal adhesions in undifferentiated, motile cells, but that Talin2 may serve as the link between integrins and the sarcomeric cytoskeletonin stable adhesion complexes in mature striated muscle. Cell Motil. Cytoskeleton 2007. © 2006 Wiley-Liss, Inc. [source] Src-dependent phosphorylation of Scar1 promotes its association with the Arp2/3 complexCYTOSKELETON, Issue 1 2006Hazel Ardern Abstract The WAVE/Scar proteins regulate actin polymerisation at the leading edge of motile cells via activation of the Arp2/3 complex in response to extracellular cues. Within cells they form part of a pentameric complex that is thought to regulate their ability to interact and activate the Arp2/3 complex. However, the exact mechanism for this is not known. We set out to assess whether phosphorylation of Scar1 by the non-receptor tyrosine kinase Src may influence the function of Scar1 and its ability to regulate Arp2/3-mediated actin polymerisation. We show that Scar1 is phosphorylated by Src in vitro and in vivo and identify tyrosine 125 as the major site in Scar1 to be phosphorylated in cells. Src-dependent phosphorylation of Scar1 on tyrosine 125 enhances its ability to bind to the Arp2/3 complex and regulates its ability to control actin polymerisation in cells. Thus, Src may act as an intermediary to regulate the activity of the Arp2/3 complex in response to external stimuli, via modulation of its interaction with WAVE/Scar proteins. Cell Motil. Cytoskeleton, 2006. © 2005 Wiley-Liss, Inc. [source] Expression of WASP and Scar1/WAVE1 actin-associated proteins is differentially modulated during differentiation of HL-60 cellsCYTOSKELETON, Issue 4 2003Sophie Launay Abstract The Wiskott-Aldrich Syndrome (WAS) is a disease associated with mutations in the WAS gene and characterised by developmental defects in haematopoietic cells such as myeloid cells. The Wiskott-Aldrich Syndrome protein (WASP)-family includes Scar1 and WASP, which are key regulators of actin reorganization in motile cells. To understand the roles of Scar1 and WASP in myeloid cells and their cytoskeletal control in haematopoietic tissues, we have explored their expression during differentiation of the promyeloid cell line HL-60. Undifferentiated HL-60 cells expressed Scar1 and WASP, and differentiation to neutrophils, induced by retinoic acid or non-retinoid agent treatments, led to a decrease in the level of expression of Scar1, whereas WASP expression was unaffected. Differentiation to monocytes/macrophages, induced by phorbol ester treatment, resulted in a decreased expression of both proteins in the adherent mature cells. Vitamin D3 treatment or cytochalasin D in combination with PMA treatment did not affect WASP expression suggesting that adhesion and cytoskeletal integrity were both essential to regulate WASP expression. Scar1 expression was regulated by differentiation, adhesion, and cytoskeletal integrity. Recently, WASP was found to colocalize with actin in the podosomes. In contrast, we show here that Scar1 did not localize with the podosomes in mature monocytes/macrophages. These observations show for the first time that modulation of Scar1 and WASP expression is a component of the differentiation program of myeloid precursors and indicate that WASP and Scar1 have different roles in mature myeloid cells. Cell Motil. Cytoskeleton 54:274,285, 2003. © 2003 Wiley-Liss, Inc. [source] Hemidesmosome protein dynamics in live epithelial cellsCYTOSKELETON, Issue 2 2003Daisuke Tsuruta Abstract Hemidesmosomes mediate stable anchorage of epithelial cells to laminin-5 in the basement membrane zone and have been likened to spot-welds. Indeed, it has been assumed that hemidesmosomes are not dynamic, at least when compared to other matrix adhesion sites including focal contacts. We tested this notion by monitoring the fate of green fluorescent protein (GFP)-tagged human integrin ,4 subunit (GFP-h,4) and GFP-tagged 180-kD human bullous pemphigoid (BP) autoantigen (GFP-BP180) in live cultures of 804G cells that assemble numerous mature hemidesmosomes. In subconfluent 804G cells, both GFP-h,4 and GFP-BP180 protein clusters are not stable but assemble into and disassemble out of cat paw,like arrays at a relatively rapid rate. In confluent populations of 804G cells, although some cat paw,like clusters of both GFP-h,4 and GFP-BP180 are stable over periods of >60 min, other GFP-h,4 and GFP-BP180 protein arrays form and/or disappear during the same time period. Moreover, individual labeled particles show considerable motility in the plane of the membrane. Fluorescence recovery after photobleaching analyses provide a further indication of the dynamics of hemidesmosome proteins. In particular, bleached GFP-h,4 protein clusters in confluent cells recover signal within about 30 min, indicating that there is a relatively rapid turnover of hemidesmosome components in protein arrays clustered along the substratum attached surface of a cell. The rate of recovery is dependent on an intact microfilament system. In sharp contrast, bleached GFP-BP180 protein clusters in confluent cells fail to recover signal even when observed for longer than 60 min. To evaluate hemidesmosome protein dynamics in motile cells, we monitored GFP-h,4 and GFP-BP180 in 804G cells populating scrape wound sites in vitro. In these migratory cells, which lack mature hemidesmosomes, integrin ,4 subunit and BP180 protein clusters progressively assemble and disassemble into linear and cat-paw arrays. In summary, hemidesmosome protein clusters, like their counterparts in focal contacts, are dynamic. We discuss these results in relation to hemidesmosome functions. Cell Motil. Cytoskeleton 54:122,134, 2003. © 2003 Wiley-Liss, Inc. [source] Temperature and pyoverdine-mediated iron acquisition control surface motility of Pseudomonas putidaENVIRONMENTAL MICROBIOLOGY, Issue 7 2007Miguel A. Matilla Summary Pseudomonas putida KT2440 is unable to swarm at its common temperature of growth in the laboratory (30°C) but exhibits surface motility similar to swarming patterns in other Pseudomonas between 18°C and 28°C. These motile cells show differentiation, consisting on elongation and the presence of surface appendages. Analysis of a collection of mutants to define the molecular determinants of this type of surface movement in KT2440 shows that while type IV pili and lipopolysaccharide O-antigen are requisites flagella are not. Although surface motility of flagellar mutants was macroscopically undistinguishable from that of the wild type, microscopy analysis revealed that these mutants move using a distinct mechanism to that of the wild-type strain. Mutants either in the siderophore pyoverdine (ppsD) or in the FpvA siderophore receptor were also unable to spread on surfaces. Motility in the ppsD strain was totally restored with pyoverdine and partially with the wild-type ppsD allele. Phenotype of the fpvA strain was not complemented by this siderophore. We discuss that iron influences surface motility and that it can be an environmental cue for swarming-like movement in P. putida. This study constitutes the first report assigning an important role to pyoverdine iron acquisition in en masse bacterial surface movement. [source] The first CH domain of affixin activates Cdc42 and Rac1 through ,PIX, a Cdc42/Rac1-specific guanine nucleotide exchanging factorGENES TO CELLS, Issue 3 2004Wataru Mishima Rho GTPases, Cdc42 and Rac1, play pivotal roles in cell migration by efficiently integrating cell-substrate adhesion and actin polymerization. Although it has been suggested that integrins stimulate these Rho GTPases via some of integrin binding proteins such as focal adhesion kinase (FAK) and paxillin, the precise molecular mechanism is largely unknown. In this study, we showed that the over-expression of RP1 corresponding to the first CH domain (CH1) of affixin, an integrin-linked kinase (ILK)-binding protein, induced a significant actin reorganization in MDCK cells by activating Cdc42/Rac1. Affixin full length and RP1 co-immunoprecipitated with ,PIX, a Cdc42/Rac1-specific guanine nucleotide exchanging factor (GEF), and they co-localized at the tips of lamellipodia in motile cells. The involvement of ,PIX in the RP1-induced Cdc42 activation was demonstrated by the significant dominant negative effect of a point mutant of ,PIX, ,PIX (L383R, L384S), lacking GEF activity. Our data strongly support that ILK and affixin provide a novel signalling pathway that links integrin signalling to Cdc42/Rac1 activation. [source] Modeling cell adhesion to a substrate with gradient in ligand densityAICHE JOURNAL, Issue 11 2009Alireza S. Sarvestani Abstract Surface density profile of bioadhesive ligands greatly influences spreading and migration of cells on substrates. A 1D peeling model is developed to predict the equilibrium adhesion strength and peeling tension of a cell membrane, adhered on a substrate with linearly increasing density of ligands. Cell membrane is modeled as a linear elastic shell subjected to a tensile force applied at the free extremity and adhesive traction due to specific receptor-ligand interactions with the substrate. Membrane peeling tension increased with gradient slope and reached an asymptotic limit independent of gradient slope but proportional to receptor-ligand interaction energy. Peeling tension from substrates with negative gradient slope, at the rear edge of adhesion zone, was considerably lower than the tension from substrates with positive gradient slope at the leading edge, indicating that detachment is more likely to be initiated at the rear edge. This prediction leads to a possible mechanism for experimentally observed haptotactic locomotion of motile cells toward the direction of higher ligand density. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] 94 An obligate(?) heterokont biflagellate parasite in codium fragileJOURNAL OF PHYCOLOGY, Issue 2003T. F. Lee Specimens of Codium fragile (Suringar) Hariot ssp. tomentosoides were collected from 9 sites in New England, and Long Island, New York at intervals throughout the years 1999-2003. Segments were removed from the thalli and chopped into fine fragments, mostly individual utricles and medullary filaments. Fragments were incubated in enriched seawater in dim light at 15C, 12:12 LD. Within 2,3 days, in almost all cases (more than 300) motile cells formed in many of the utricles and filaments. These were 10,15 micrometer elongated biflagellate heterokont cells. They appeared to consume the chloroplasts, and within 24 hours were reduced to colorless cells, about 5 micrometers long. These cells are unable to grow in Codium chloroplast suspensions. They appear to be always associated with Codium thalli, despite attempts to clean the thalli, and were never seen in utricles or filaments of intact plants. Their ultrastructure is under investigation and will be reported on here. [source] PHYLOGENETIC SYSTEMATICS OF THE ULVACEAE (ULVALES, ULVOPHYCEAE) USING CHLOROPLAST AND NUCLEAR DNA SEQUENCES,JOURNAL OF PHYCOLOGY, Issue 6 2002Hillary S. Hayden Systematic hypotheses for the Ulvaceae were tested using phylogenetic analysis of sequences for the gene encoding the large subunit of RUBISCO, small subunit rDNA and a combined data matrix. Representatives of eight putative ulvaceous genera and twelve additional taxa from the Ulvophyceae and Trebouxiophyceae were included in analyses using maximum parsimony and maximum likelihood criteria. Molecular data supported hypotheses for the Ulvaceae that are based on the early development of vegetative thalli and motile cell ultrastructure. Ulvaceae sensu Floyd and O'Kelly, including Percursaria Bory de Saint-Vincent, Ulvaria Ruprecht and a complex of closely related species of Chloropelta Tanner, Enteromorpha Link and Ulva L. was supported; however, monophyly of Enteromorpha and Ulva was not supported. The Ulvales and Ulotrichales sensu Floyd and O'Kelly were monophyletic. Blidingia Kylin and Kornmannia Bliding were allied with the former and Capsosiphon Gobi with the latter, although relationships among these and other taxa in these orders remain uncertain. The Ulvales are characterized by an isomorphic life history pattern, gametangia and sporangia that are identical in structure and development, motile cells with bilobed terminal caps and proximal sheaths consisting of two equal subunits. Method of motile cell release and the gross morphology of vegetative thalli are not systematically reliable characters. [source] Tetraspanins and Intercellular InteractionsMICROCIRCULATION, Issue 3 2001MARÍA YÁÑEZ-MÓ ABSTRACT The superfamily of tetraspanins comprises a group of polypeptides with four transmembrane domains that form large supramolecular structures in the plasma membrane through their associations to multiple integral membrane proteins. They are involved in homo- and heterotypic intercellular interactions in different processes such as hematopoiesis, lymphocyte activation, cancer metastasis, and fertilization. Intercellularly located tetraspanins regulate the juxtacrine activity of growth factors, cell fusion, and myelin formation. On the other hand, in motile cells they relocalize from cell-cell junctions to actin-based structures such as filopodia or growth cones and regulate cell motility in wound healing and angiogenesis processes. [source] Vertical Migration and Motility Responses in Three Marine Phytoplankton Species Exposed to Solar Radiation,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2007Peter R. Richter ABSTRACT Diurnal vertical migration in the water column and the impact of solar radiation on motility were investigated in three marine phytoplankton species: Tetraselmis suecica, Dunaliella salina and Gymnodinium chlorophorum. Cells were exposed to solar radiation either in ultraviolet radiation (UVR, 280,400 nm) transparent Plexiglas tubes (45 cm length, 10 cm diameter) or in quartz tubes under three radiation treatments: PAB (280,700 nm), PA (320,700 nm) and P (400,700 nm). The three species displayed different behavior after exposure to solar radiation. Tetraselmis suecica was insensitive to UVR and under high solar radiation levels, cells accumulated preferentially near the surface. Exposure experiments did not indicate any significant changes in swimming speed nor in the percentage of motile cells after 5 h of exposure. On the other hand, D. salina was sensitive to UV-B displaying a significant decrease in swimming speed and percentage of motile cells after 2,3 h of exposure. Moreover, D. salina cells migrated deep in the water column when irradiance was high. The response of G. chlorophorum was in between that of the other two species tested, with a slight (but significant) decrease in swimming speed and percentage of motile cells in all radiation treatments after 5 h of exposure. While G. chlorophorum cells were more or less homogenously distributed in the water column, a slight (but significant) avoidance response to high radiation was observed at local noon, with cells migrating deep in the water column. Our data clearly indicate that these sub-lethal effects of solar radiation are species-specific and they might have important implications for the aquatic ecosystem. [source] Development of the cell covering in the dinoflagellate Scrippsiella hexapraecingula (Peridiniales, Dinophyceae)PHYCOLOGICAL RESEARCH, Issue 3 2001Satoko Sekida SUMMARY The organization and development of cell coverings in two alternate phases of the life cycle in a marine dinoflagellate, Scrippsiella hexapraecingula Horiguchi et Chihara, were investigated by thin sectioning and freeze-fracture electron microscopy. In one of these phases, the motile phase, cells have an outermost plasma membrane that is lined with flattened amphiesmal vesicles. Groups of microtubules lie beneath these vesicles. In mature motile cells, thecal plates are completely enclosed in individual amphiesmal vesicles. After settling, the cells enter the second, non-motile phase. Here, ecdysis occurs, resulting in several steps including formation of the first pellicle layer (PI), fusion of the inner amphiesmal vesicle membranes to form the new plasma membrane, deposition of the second pellicle layer (PM) under PI, and the appearance and fusion of juvenile amphiesmal vesicles to form new territories, which eventually give rise to new thecal plates in the next motile phase. Thus, the pattern in which thecal plates are arranged in motile cells is determined at the time when the amphiesmal vesicles develop into non-motile cells. [source] Sperm quality of Brazilian flounder Paralichthys orbignyanus throughout the reproductive seasonAQUACULTURE RESEARCH, Issue 9 2010Carlos Frederico Ceccon Lanes Abstract The aim of this study was to evaluate the sperm quality of Brazilian flounder Paralichthys orbignyanus throughout its reproductive season. Sperm was collected at the beginning, middle and end of the breeding period. Spermatozoa density was maximum at the beginning (12.7 ± 0.92 × 109 cells mL,1) and at the end (11.8 ± 0.39 × 109 cells mL,1) of the breeding season (P<0.05). Sperm production and the percentage of spermatozoa moving fast forward increased significantly towards the end of the breeding season (P<0.05). The mean duration of progressive motility of spermatozoa was around 10 min. No difference was observed during the reproductive season in the percentage of motile cells, pH, osmolality and K+, Cl, and Mg2+ concentrations in seminal plasma. The concentration of Na+ increased throughout the breeding season, reaching 174.62 ± 12.68 mmol L,1 at the end (P<0.05). There was a decline in the concentration of Ca2+ (12.31 ± 3.08 mmol L,1) in the middle of the breeding season, which coincided with the shortest motility duration of spermatozoa. The information reported in this study should help to improve management and optimize the development of protocols for short-term storage and cryopreservation of Brazilian flounder semen. [source] Effect of different methods for the induction of spermiation on semen quality in European eelAQUACULTURE RESEARCH, Issue 15 2005Juan F Asturiano Abstract Five hormonal treatments with human chorionic gonadotropin (hCG) were tested for the induction of maturation and spermiation in male farmed eels. The main aim was to optimize previously used hormonal treatments to achieve shorter induction treatments, longer spermiation periods and/or higher sperm quality. Fish treated for just 3 weeks (treatment E) or until the onset of spermiation (treatment C) showed the worst results, while the treatment consisting of weekly administration of 1.5 IU hCG g,1 fish (treatment A) induced the highest percentage of spermiating males, the highest number of sperm samples and sperm volumes and densities similar to the rest of the treatments (B: half hormone dosage, or D: biweekly administration). Evaluation of the sperm quality was performed by computer-assisted sperm analysis (CASA), considering the percentage of total motile spermatozoa, the percentage of fast and medium-velocity spermatozoa, as well as different motility parameters. Sperm samples from A-D groups showed between 44% and 54% motile spermatozoa, and between 10% and 15% fast spermatozoa, while samples from E-treated males showed 0% motile cells. No significant differences were found in the spermatozoa straight line velocity (VSL), curvilinear velocity (VCL) or the angular velocity (VAP), neither spermatozoa beating cross frequency (BCF) between A,D groups. [source] | ||||||||||||||||||||||